feat(memory): système de mémoire projet model-agnostic (L14, LOT A+B+C)

Base de connaissance persistante par projet, indépendante de tout modèle/CLU
et de git. Cadrage archi en §14.5 (ARCHITECTURE.md), cycle Archi→Dev→Test.

LOT A — étage 1 (.md, source de vérité)
  - domaine: entité Memory (+ MemorySlug, MemoryType, MemoryFrontmatter,
    MemoryLink, MemoryIndexEntry), liens [[slug]], index MEMORY.md dérivé
  - port MemoryStore + MemoryError, adapter FsMemoryStore (.ideai/memory/)
  - application: 7 use cases (Create/Update/List/Get/Delete/ReadIndex/
    ResolveLinks), From<MemoryError> for AppError
  - app-tauri: commandes + DTO, events MemorySaved/MemoryDeleted
  - suppression de la variante morte DomainError::MalformedFrontmatter

LOT B — rappel adaptatif (étage 1)
  - port MemoryRecall + MemoryQuery, adapter NaiveMemoryRecall (troncature
    au budget de tokens, court-circuit budget-0), use case RecallMemory

LOT C — étage 2 vectoriel (structure complète, zéro dépendance lourde)
  - port Embedder + EmbedderError, profils déclaratifs EmbedderProfile/
    EmbedderStrategy (embedder.json)
  - VectorMemoryRecall (cosinus, cache .ideai/memory/.index/ gitignoré)
  - AdaptiveMemoryRecall (bascule pure should_use_vector), défaut none
  - HashEmbedder (déterministe, tests), StubEmbedder (onnx/server/api)

Tests: 57 binaires verts, build + clippy --workspace sans warning.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -32,6 +32,9 @@ frontend/coverage/
 # Ephemeral per-agent run directories (isolated PTY cwd + generated convention
 # files), created at activation — not versioned (ARCHITECTURE §9.1 / §14.1).
 .ideai/run/
+# Derived vector store for semantic recall (LOT C / §14.5.3): embeddings of the
+# memory notes, rebuildable from the `.md` source of truth — not versioned.
+.ideai/memory/.index/
 
 # ─── Editors / OS ───────────────────────────────────────────────────────────
 .idea/

ARCHITECTURE.md

@@ -600,6 +600,7 @@ IdeA/
 | L11 | **Packaging & livraison** | Tauri bundle : NSIS `setup.exe`, **AppImage** multi-distro, CI Linux+Windows. | `app-tauri`, CI |
 | L12 | **Skills** | Entité `Skill`, `SkillStore`, CRUD skills global+projet, assignation agent↔skills, injection dans convention file à l'activation. UI onglet Skills. | `domain/skill`, `application/skill`, `infrastructure/store`, `frontend/features/skills` |
 | L13 | **OrchestratorApi** | File-watcher `.ideai/requests/`, port `OrchestratorApi`, adapter `FsOrchestratorAdapter`, actions `spawn_agent`/`stop_agent`/`update_agent_context`. | `infrastructure/orchestrator`, `application/agent`, `app-tauri` |
+| L14 | **Mémoire** | Base de connaissance projet model-agnostic. Modèle 2 étages : `.md` source de vérité (port `MemoryStore`), rappel adaptatif (port `MemoryRecall`), embeddings déclaratifs (port `Embedder`), bascule auto sur seuil. Découpé en sous-lots **A/B/C** (voir §14.5). | `domain/memory`, `application/memory`, `infrastructure/store`, `frontend/features/memory` |
 
 ---
 
@@ -673,6 +674,165 @@ Git est un **outil posé par-dessus l'IDE**, pas un socle. Supprimer le repo git
 
 ---
 
+### 14.5 Système de mémoire — base de connaissance projet model-agnostic (L14)
+
+**Objectif** : doter chaque projet d'une **mémoire persistante** (préférences, décisions, feedback, références) que les agents lisent et enrichissent, **sans jamais dépendre d'un modèle ou d'une CLI** (principe fondateur). La mémoire est commune au project root, partagée par tous les agents (décision : mémoire au niveau projet, pas par `run/<id>`).
+
+#### Modèle 2 étages (hybride)
+
+- **Étage 1 — fichiers `.md` (source de vérité)** : chaque note = un `.md` (frontmatter YAML `name`/`description`/`metadata.type` + corps Markdown) sous `.ideai/memory/<slug>.md`. Un index agrégé `MEMORY.md` (une ligne `- [Titre](slug.md) — hook` par note) est **dérivé**, reconstructible. Les notes se référencent par liens `[[slug]]`. C'est le **seul** étage qui fait foi.
+- **Étage 2 — index de rappel sémantique vectoriel (dérivé)** : embeddings des notes, **jamais source de vérité**, reconstructible et supprimable à tout moment. Sert uniquement à accélérer/cibler le rappel quand la mémoire devient trop grosse pour être lue intégralement.
+
+#### Bascule étage 1 ↔ étage 2 (automatique, sur seuil objectif)
+
+Le **rappel** (port `MemoryRecall`) est adaptatif : tant que la taille de la mémoire reste sous un **budget de tokens** configurable, l'adapter **naïf** lit `MEMORY.md` intégralement (zéro dépendance). Au-dessus du seuil, l'adapter **vectoriel** prend le relais. La bascule est une décision objective (taille vs budget), pas un choix manuel. **Défaut : `none`** (rappel naïf, aucun embedder) — esprit Linux « rien d'imposé, tout fonctionnel ».
+
+#### Ports (frontières domaine)
+
+- **`MemoryStore`** *(fait — LOT A étage 1)* : CRUD des `.md` + index `MEMORY.md` dérivé + `resolve_links` (ignore les liens cassés). Adapter `FsMemoryStore` (compose `FileSystem`, location-neutral). Erreurs `MemoryError`.
+- **`MemoryRecall`** *(LOT B)* : rappel adaptatif d'un sous-ensemble pertinent de notes pour une requête. Deux adapters substituables (Liskov) : `NaiveMemoryRecall` (lecture intégrale via `MemoryStore`) et, plus tard, `VectorMemoryRecall` (étage 2).
+- **`Embedder`** *(LOT C)* : production de vecteurs d'embedding, décrit par des **profils déclaratifs façon CLI LLM** (§9). Stratégies : `localOnnx` / `localServer` / `api` / `none`. `none` = pas d'embedder ⇒ rappel naïf forcé.
+
+#### Conformité hexagonale
+
+`MemoryStore`/`MemoryRecall`/`Embedder` sont des **traits du domaine** ; les adapters vivent en `infrastructure`. L'application ne parle qu'aux ports. Le domaine `memory` reste I/O-free (le format YAML/index est **possédé par l'adapter** `FsMemoryStore`, pas par le domaine). La mémoire est **indépendante de git** (§14.4) et du moteur IA.
+
+#### Découpage en sous-lots (binôme dev+test par sous-lot)
+
+- **LOT A — Étage 1 `.md`** : *domaine + adapter faits et verts.* Reste à livrer : **use cases `application/memory`** + **câblage app-tauri** (commandes + DTO ; les events `Memory*` et leurs DTO existent déjà). Voir §14.5.1.
+- **LOT B — Rappel adaptatif** : port `MemoryRecall`, adapter `NaiveMemoryRecall`, use case `RecallMemory`. Voir §14.5.2.
+- **LOT C — Étage 2 vectoriel** : port `Embedder`, profils déclaratifs `embedder.json`, adapter `VectorMemoryRecall`, logique de bascule sur seuil. Voir §14.5.3.
+
+##### 14.5.1 LOT A (fin) — contrats application + app-tauri
+
+**Use cases `application/memory`** (miroir de `application/skill`, chacun `Arc<dyn MemoryStore>`, `execute(Input) -> Result<Output, AppError>`) :
+
+```rust
+// CreateMemory — crée/écrit une note + upsert index. Émet MemorySaved.
+struct CreateMemoryInput  { project_root: ProjectPath, name: String,        // slug brut → MemorySlug::new
+                            description: String, r#type: MemoryType, content: String }
+struct CreateMemoryOutput { memory: Memory }
+
+// UpdateMemory — remplace une note existante (revalide invariants). Émet MemorySaved.
+struct UpdateMemoryInput  { project_root: ProjectPath, slug: MemorySlug,
+                            description: String, r#type: MemoryType, content: String }
+struct UpdateMemoryOutput { memory: Memory }
+
+// ListMemories — liste les notes (pilotée par l'index).
+struct ListMemoriesInput  { project_root: ProjectPath }
+struct ListMemoriesOutput { memories: Vec<Memory> }
+
+// GetMemory — une note par slug.
+struct GetMemoryInput  { project_root: ProjectPath, slug: MemorySlug }
+struct GetMemoryOutput { memory: Memory }
+
+// DeleteMemory — supprime une note (retire la ligne d'index). Émet MemoryDeleted.
+struct DeleteMemoryInput { project_root: ProjectPath, slug: MemorySlug }   // -> ()
+
+// ReadMemoryIndex — lit MEMORY.md structuré (pour l'affichage graphique de la mémoire).
+struct ReadMemoryIndexInput  { project_root: ProjectPath }
+struct ReadMemoryIndexOutput { entries: Vec<MemoryIndexEntry> }
+
+// ResolveMemoryLinks — liens [[slug]] sortants résolus (liens cassés ignorés).
+struct ResolveMemoryLinksInput  { project_root: ProjectPath, slug: MemorySlug }
+struct ResolveMemoryLinksOutput { links: Vec<MemoryLink> }
+```
+
+> **Décision** : on expose les **7** use cases (CRUD complet + `ReadMemoryIndex` + `ResolveMemoryLinks`). `ReadMemoryIndex` alimente la vue graphique de la mémoire ; `ResolveMemoryLinks` alimente la navigation par liens. `CreateMemory`/`UpdateMemory` portent en plus `Arc<dyn EventBus>`.
+
+**Émission d'events** (ports `MemoryStore` + `EventBus` ; events déjà définis dans `domain::events`) :
+
+| Use case | Event émis |
+|---|---|
+| `CreateMemory`, `UpdateMemory` | `DomainEvent::MemorySaved { slug }` |
+| `DeleteMemory` | `DomainEvent::MemoryDeleted { slug }` |
+| `ListMemories`, `GetMemory`, `ReadMemoryIndex`, `ResolveMemoryLinks` | *(aucun — lectures)* |
+
+> `MemoryIndexRebuilt { project_id }` n'est **pas** émis par les use cases CRUD (l'index est réécrit en interne par le store à chaque save/delete, pas un rebuild distinct). Le réserver à un futur use case `RebuildMemoryIndex` (reconstruction explicite depuis les `.md`) — non requis pour clore LOT A.
+
+**Mapping `From<MemoryError> for AppError`** (à ajouter dans `application/src/error.rs`, calqué sur `From<StoreError>`) :
+
+```rust
+impl From<MemoryError> for AppError {
+    fn from(e: MemoryError) -> Self {
+        match e {
+            MemoryError::NotFound          => Self::NotFound("memory note".to_owned()),
+            MemoryError::Frontmatter(m)    => Self::Invalid(m),   // donnée malformée = invariant
+            other /* Io | Serialization */ => Self::Store(other.to_string()),
+        }
+    }
+}
+```
+
+**Commandes app-tauri ↔ DTO** (miroir des commandes skills ; `resolve_project(project_id)` → `project.root` ; slug parsé via `MemorySlug::new` qui renvoie `INVALID` si invalide) :
+
+| Commande Tauri | Request DTO (camelCase) | Réponse |
+|---|---|---|
+| `create_memory` | `{ projectId, name, description, type, content }` | `MemoryDto` |
+| `update_memory` | `{ projectId, slug, description, type, content }` | `MemoryDto` |
+| `list_memories` | `{ projectId }` | `MemoryListDto` |
+| `get_memory` | `{ projectId, slug }` | `MemoryDto` |
+| `delete_memory` | `{ projectId, slug }` | `()` |
+| `read_memory_index` | `{ projectId }` | `MemoryIndexDto` |
+| `resolve_memory_links` | `{ projectId, slug }` | `MemoryLinksDto` |
+
+DTO de réponse (`Memory`/`MemoryIndexEntry`/`MemoryLink` dérivent déjà `Serialize` côté domaine pour les types persistés ; sinon mapping explicite façon `SkillDto`) : `MemoryDto(Memory)`, `MemoryListDto(Vec<MemoryDto>)`, `MemoryIndexDto(Vec<MemoryIndexEntry>)`, `MemoryLinksDto(Vec<String>)` (slugs cibles). Enregistrer les 7 commandes dans `tauri::generate_handler!` (`app-tauri/src/lib.rs`). Câbler les 7 use cases dans le composition root (`state.rs`) : `FsMemoryStore` (déjà exporté) injecté en `Arc<dyn MemoryStore>`, partagé par tous les use cases, `EventBus` pour Create/Update/Delete.
+
+> Note d'implémentation : `FsMemoryStore` prend le `root` **par appel** (comme `SkillStore`) ⇒ **une seule** instance store partagée, comme pour les skills.
+
+##### 14.5.2 LOT B — port `MemoryRecall` + adapter naïf
+
+```rust
+/// Rappel adaptatif d'un sous-ensemble pertinent de notes pour une requête.
+#[async_trait]
+pub trait MemoryRecall: Send + Sync {
+    /// Renvoie les notes les plus pertinentes pour `query`, limitées à `budget`.
+    /// Contrat : best-effort, jamais d'erreur bloquante sur mémoire vide
+    /// (renvoie une liste vide) ; l'adapter naïf ignore la pertinence et
+    /// renvoie l'index/les notes dans l'ordre, tronqué au budget.
+    async fn recall(
+        &self,
+        root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError>;
+}
+
+pub struct MemoryQuery {
+    pub text: String,           // requête (souvent le contexte courant de l'agent)
+    pub token_budget: usize,    // budget au-delà duquel l'étage 2 prendrait le relais
+}
+```
+
+- **Adapter `NaiveMemoryRecall`** (`infrastructure`) : compose `Arc<dyn MemoryStore>`, lit `read_index` et tronque au budget. Aucune dépendance externe. C'est le **défaut**.
+- **Use case `RecallMemory`** (`application/memory`) : `RecallMemoryInput { project_root, text, token_budget } -> RecallMemoryOutput { entries: Vec<MemoryIndexEntry> }`, port `Arc<dyn MemoryRecall>`. Pas d'event.
+- **Contrat de substituabilité (Liskov)** : `NaiveMemoryRecall` et `VectorMemoryRecall` (LOT C) sont interchangeables ; un budget nul ⇒ liste vide ; mémoire absente ⇒ liste vide, jamais d'erreur.
+
+##### 14.5.3 LOT C — port `Embedder` + profils + adapter vectoriel + bascule
+
+```rust
+/// Produit des vecteurs d'embedding, piloté par un profil déclaratif (façon §9).
+#[async_trait]
+pub trait Embedder: Send + Sync {
+    fn id(&self) -> &str;                              // ex. "local-onnx-minilm"
+    async fn embed(&self, texts: &[String]) -> Result<Vec<Vec<f32>>, EmbedderError>;
+    fn dimension(&self) -> usize;                      // taille des vecteurs produits
+}
+```
+
+- **Profils déclaratifs** `embedder.json` (store global IDE, comme `profiles.json`) : `{ id, name, strategy: "localOnnx"|"localServer"|"api"|"none", model?, endpoint?, apiKeyEnv?, dimension }`. **Open/Closed** : ajouter un moteur d'embedding = une donnée, pas du code.
+- **Adapter `VectorMemoryRecall`** (`infrastructure`) : compose `Arc<dyn Embedder>` + `Arc<dyn MemoryStore>` + un store de vecteurs dérivé sous `.ideai/memory/.index/` (reconstructible, ajouté au `.gitignore` au même titre que `run/`). Implémente `MemoryRecall`.
+- **Logique de bascule** (dans le use case `RecallMemory` ou un `AdaptiveMemoryRecall` qui compose les deux adapters) : si taille mémoire ≤ `token_budget` **ou** stratégie embedder = `none` ⇒ `NaiveMemoryRecall` ; sinon ⇒ `VectorMemoryRecall`. Décision objective, testable sans I/O (la mesure de taille est une fonction pure de l'index).
+- **`EmbedderError`** : nouveau type d'erreur par port (façon `MemoryError`), mappé en `AppError` (`none`/indisponible ⇒ dégrade vers naïf, jamais d'échec dur du rappel).
+- **Garde-fou produit** : défaut `none` ⇒ LOT C **n'impose aucune dépendance** ; un utilisateur sans embedder a une mémoire pleinement fonctionnelle (étage 1 + rappel naïf).
+
+#### Anomalies de conformité relevées sur l'existant (à traiter par les agents dev)
+
+1. **Doublon `DomainError::MalformedFrontmatter` vs `MemoryError::Frontmatter`** : `error.rs` définit `DomainError::MalformedFrontmatter { reason }`, mais le domaine `memory.rs` ne l'utilise jamais (il lève `EmptyField`/`InvalidSlug`) et l'adapter parse via `MemoryError::Frontmatter`. La variante `DomainError::MalformedFrontmatter` est **morte**. **Action** : la supprimer (le parsing de frontmatter est une responsabilité d'adapter → `MemoryError::Frontmatter`), sauf si un futur parseur de frontmatter *dans le domaine* est prévu (il ne l'est pas — le domaine reste format-neutral, cf. doc-module `memory.rs`). Anomalie mineure, sans impact fonctionnel.
+2. **`MemoryError` non encore mappé dans `AppError`** : normal (la couche application mémoire n'existe pas encore) ; couvert par LOT A (§14.5.1).
+3. **`MemoryIndexRebuilt` / `MemorySaved` / `MemoryDeleted` déjà câblés bout-en-bout** (domaine event + DTO `app-tauri` + relais) mais **non encore émis** faute de use cases : attendu, résolu par LOT A. RAS sur le sens des dépendances : domaine I/O-free, adapter compose `FileSystem`, application ne référence que les ports. **Conforme hexagonal/SOLID.**
+
+---
+
 ## 13. Risques techniques & points ouverts (spikes)
 
 1. **PTY cross-platform** : portable-pty + xterm.js OK sur les 3 OS, mais signaux/resize/exit codes diffèrent (Windows ConPTY). **Spike** L3.

crates/app-tauri/src/commands.rs

@@ -17,6 +17,8 @@ use application::{
     UpdateAgentContextInput,
     AssignSkillToAgentInput, CreateSkillInput, DeleteSkillInput, ListSkillsInput,
     UnassignSkillFromAgentInput, UpdateSkillInput,
+    CreateMemoryInput, DeleteMemoryInput, GetMemoryInput, ListMemoriesInput, ReadMemoryIndexInput,
+    RecallMemoryInput, ResolveMemoryLinksInput, UpdateMemoryInput,
 };
 use domain::ports::PtyHandle;
 
@@ -37,6 +39,8 @@ use crate::dto::{
     TemplateListDto, TerminalClosedDto, TerminalSessionDto, UpdateAgentContextRequestDto,
     UpdateTemplateRequestDto, WriteTerminalRequestDto, parse_skill_id, AssignSkillRequestDto,
     CreateSkillRequestDto, SkillDto, SkillListDto, UnassignSkillRequestDto, UpdateSkillRequestDto,
+    parse_memory_slug, CreateMemoryRequestDto, MemoryDto, MemoryIndexDto, MemoryLinksDto,
+    MemoryListDto, RecallMemoryRequestDto, UpdateMemoryRequestDto,
 };
 use domain::{SkillRef, SkillScope};
 use crate::pty::{PtyBridge, PtyChunk};
@@ -1392,3 +1396,197 @@ pub async fn unassign_skill_from_agent(
         .await
         .map_err(ErrorDto::from)
 }
+
+// ---------------------------------------------------------------------------
+// Memory (LOT A — §14.5.1)
+// ---------------------------------------------------------------------------
+
+/// `create_memory` — create a memory note in the project's store.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an invalid slug/empty fields or
+/// malformed project id, `NOT_FOUND` if the project is unknown, `STORE` on
+/// failure).
+#[tauri::command]
+pub async fn create_memory(
+    request: CreateMemoryRequestDto,
+    state: State<'_, AppState>,
+) -> Result<MemoryDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    state
+        .create_memory
+        .execute(CreateMemoryInput {
+            project_root: project.root,
+            name: request.name,
+            description: request.description,
+            r#type: request.r#type,
+            content: request.content,
+        })
+        .await
+        .map(MemoryDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `update_memory` — replace an existing memory note (re-validates invariants).
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an invalid slug/empty fields,
+/// `NOT_FOUND` if the project is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn update_memory(
+    request: UpdateMemoryRequestDto,
+    state: State<'_, AppState>,
+) -> Result<MemoryDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    let slug = parse_memory_slug(&request.slug)?;
+    state
+        .update_memory
+        .execute(UpdateMemoryInput {
+            project_root: project.root,
+            slug,
+            description: request.description,
+            r#type: request.r#type,
+            content: request.content,
+        })
+        .await
+        .map(MemoryDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `list_memories` — list the project's memory notes.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for a malformed id, `NOT_FOUND` if the
+/// project is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn list_memories(
+    project_id: String,
+    state: State<'_, AppState>,
+) -> Result<MemoryListDto, ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    state
+        .list_memories
+        .execute(ListMemoriesInput {
+            project_root: project.root,
+        })
+        .await
+        .map(MemoryListDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `get_memory` — read one memory note by slug.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an invalid slug/id, `NOT_FOUND` if the
+/// project or note is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn get_memory(
+    project_id: String,
+    slug: String,
+    state: State<'_, AppState>,
+) -> Result<MemoryDto, ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    let slug = parse_memory_slug(&slug)?;
+    state
+        .get_memory
+        .execute(GetMemoryInput {
+            project_root: project.root,
+            slug,
+        })
+        .await
+        .map(MemoryDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `delete_memory` — remove a memory note (and its index row).
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an invalid slug/id, `NOT_FOUND` if the
+/// project or note is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn delete_memory(
+    project_id: String,
+    slug: String,
+    state: State<'_, AppState>,
+) -> Result<(), ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    let slug = parse_memory_slug(&slug)?;
+    state
+        .delete_memory
+        .execute(DeleteMemoryInput {
+            project_root: project.root,
+            slug,
+        })
+        .await
+        .map_err(ErrorDto::from)
+}
+
+/// `read_memory_index` — read the structured `MEMORY.md` index.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for a malformed id, `NOT_FOUND` if the
+/// project is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn read_memory_index(
+    project_id: String,
+    state: State<'_, AppState>,
+) -> Result<MemoryIndexDto, ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    state
+        .read_memory_index
+        .execute(ReadMemoryIndexInput {
+            project_root: project.root,
+        })
+        .await
+        .map(MemoryIndexDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `recall_memory` — recall the most relevant memory entries for a query within
+/// a token budget (LOT B — §14.5.2).
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for a malformed id, `NOT_FOUND` if the
+/// project is unknown, `STORE` on failure). An empty or absent memory and a zero
+/// budget both yield an empty list, not an error.
+#[tauri::command]
+pub async fn recall_memory(
+    request: RecallMemoryRequestDto,
+    state: State<'_, AppState>,
+) -> Result<MemoryIndexDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    state
+        .recall_memory
+        .execute(RecallMemoryInput {
+            project_root: project.root,
+            text: request.text,
+            token_budget: request.token_budget,
+        })
+        .await
+        .map(MemoryIndexDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `resolve_memory_links` — resolve a note's outgoing `[[slug]]` links.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an invalid slug/id, `NOT_FOUND` if the
+/// project or source note is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn resolve_memory_links(
+    project_id: String,
+    slug: String,
+    state: State<'_, AppState>,
+) -> Result<MemoryLinksDto, ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    let slug = parse_memory_slug(&slug)?;
+    state
+        .resolve_memory_links
+        .execute(ResolveMemoryLinksInput {
+            project_root: project.root,
+            slug,
+        })
+        .await
+        .map(MemoryLinksDto::from)
+        .map_err(ErrorDto::from)
+}

crates/app-tauri/src/dto.rs

@@ -1514,3 +1514,184 @@ pub fn parse_skill_id(raw: &str) -> Result<SkillId, ErrorDto> {
             message: format!("invalid skill id: {raw}"),
         })
 }
+
+// ---------------------------------------------------------------------------
+// Memory (LOT A — §14.5.1)
+// ---------------------------------------------------------------------------
+
+use application::{
+    CreateMemoryOutput, GetMemoryOutput, ListMemoriesOutput, ReadMemoryIndexOutput,
+    RecallMemoryOutput, ResolveMemoryLinksOutput, UpdateMemoryOutput,
+};
+use domain::{Memory, MemoryIndexEntry, MemorySlug, MemoryType};
+
+/// A memory note crossing the wire.
+///
+/// Built explicitly from [`Memory`] (its `body` is [`domain::MarkdownDoc`], not
+/// directly a JSON string) so the TS mirror gets a flat camelCase shape.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct MemoryDto {
+    /// The note's slug (its identity, also the file stem).
+    pub name: String,
+    /// One-line description (the index hook).
+    pub description: String,
+    /// The note's kind.
+    pub r#type: MemoryType,
+    /// Markdown body of the note.
+    pub content: String,
+}
+
+impl From<Memory> for MemoryDto {
+    fn from(memory: Memory) -> Self {
+        Self {
+            name: memory.frontmatter.name.as_str().to_owned(),
+            description: memory.frontmatter.description,
+            r#type: memory.frontmatter.r#type,
+            content: memory.body.into_string(),
+        }
+    }
+}
+
+impl From<CreateMemoryOutput> for MemoryDto {
+    fn from(out: CreateMemoryOutput) -> Self {
+        Self::from(out.memory)
+    }
+}
+
+impl From<UpdateMemoryOutput> for MemoryDto {
+    fn from(out: UpdateMemoryOutput) -> Self {
+        Self::from(out.memory)
+    }
+}
+
+impl From<GetMemoryOutput> for MemoryDto {
+    fn from(out: GetMemoryOutput) -> Self {
+        Self::from(out.memory)
+    }
+}
+
+/// A list of memory notes (transparent array on the wire).
+#[derive(Debug, Clone, Serialize)]
+#[serde(transparent)]
+pub struct MemoryListDto(pub Vec<MemoryDto>);
+
+impl From<ListMemoriesOutput> for MemoryListDto {
+    fn from(out: ListMemoriesOutput) -> Self {
+        Self(out.memories.into_iter().map(MemoryDto::from).collect())
+    }
+}
+
+/// One row of the structured `MEMORY.md` index crossing the wire.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct MemoryIndexEntryDto {
+    /// The note's slug.
+    pub slug: String,
+    /// The note's display title.
+    pub title: String,
+    /// The one-line hook (the frontmatter description).
+    pub hook: String,
+    /// The note's kind.
+    pub r#type: MemoryType,
+}
+
+impl From<MemoryIndexEntry> for MemoryIndexEntryDto {
+    fn from(entry: MemoryIndexEntry) -> Self {
+        Self {
+            slug: entry.slug.as_str().to_owned(),
+            title: entry.title,
+            hook: entry.hook,
+            r#type: entry.r#type,
+        }
+    }
+}
+
+/// The structured memory index (transparent array on the wire).
+#[derive(Debug, Clone, Serialize)]
+#[serde(transparent)]
+pub struct MemoryIndexDto(pub Vec<MemoryIndexEntryDto>);
+
+impl From<ReadMemoryIndexOutput> for MemoryIndexDto {
+    fn from(out: ReadMemoryIndexOutput) -> Self {
+        Self(out.entries.into_iter().map(MemoryIndexEntryDto::from).collect())
+    }
+}
+
+impl From<RecallMemoryOutput> for MemoryIndexDto {
+    fn from(out: RecallMemoryOutput) -> Self {
+        Self(out.entries.into_iter().map(MemoryIndexEntryDto::from).collect())
+    }
+}
+
+/// A note's resolved outgoing links — the target slugs (transparent array).
+#[derive(Debug, Clone, Serialize)]
+#[serde(transparent)]
+pub struct MemoryLinksDto(pub Vec<String>);
+
+impl From<ResolveMemoryLinksOutput> for MemoryLinksDto {
+    fn from(out: ResolveMemoryLinksOutput) -> Self {
+        Self(
+            out.links
+                .into_iter()
+                .map(|link| link.target.as_str().to_owned())
+                .collect(),
+        )
+    }
+}
+
+/// Request DTO for `create_memory`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CreateMemoryRequestDto {
+    /// Owning project (resolved to a root).
+    pub project_id: String,
+    /// Raw slug for the new note.
+    pub name: String,
+    /// One-line description (the index hook).
+    pub description: String,
+    /// The note's kind.
+    pub r#type: MemoryType,
+    /// Markdown body of the note.
+    pub content: String,
+}
+
+/// Request DTO for `update_memory`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct UpdateMemoryRequestDto {
+    /// Owning project (resolved to a root).
+    pub project_id: String,
+    /// Slug of the note to replace.
+    pub slug: String,
+    /// New description (the index hook).
+    pub description: String,
+    /// New kind.
+    pub r#type: MemoryType,
+    /// New Markdown body.
+    pub content: String,
+}
+
+/// Request DTO for `recall_memory` (LOT B — §14.5.2).
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct RecallMemoryRequestDto {
+    /// Owning project (resolved to a root).
+    pub project_id: String,
+    /// The recall query (often the agent's current working context).
+    pub text: String,
+    /// Approximate token budget bounding the recalled entries (`0` ⇒ empty).
+    pub token_budget: usize,
+}
+
+/// Parses a memory slug string coming from the frontend.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] with code `INVALID` if the string is not a valid
+/// kebab-case slug.
+pub fn parse_memory_slug(raw: &str) -> Result<MemorySlug, ErrorDto> {
+    MemorySlug::new(raw).map_err(|_| ErrorDto {
+        code: "INVALID".to_owned(),
+        message: format!("invalid memory slug: {raw}"),
+    })
+}

crates/app-tauri/src/events.rs

@@ -111,6 +111,24 @@ pub enum DomainEventDto {
         /// Whether IdeA handled it successfully.
         ok: bool,
     },
+    /// A memory note was created or updated.
+    #[serde(rename_all = "camelCase")]
+    MemorySaved {
+        /// The saved note's slug.
+        slug: String,
+    },
+    /// A memory note was deleted.
+    #[serde(rename_all = "camelCase")]
+    MemoryDeleted {
+        /// The deleted note's slug.
+        slug: String,
+    },
+    /// The aggregated `MEMORY.md` index was rebuilt.
+    #[serde(rename_all = "camelCase")]
+    MemoryIndexRebuilt {
+        /// Project id.
+        project_id: String,
+    },
     /// Raw PTY output (normally routed to a per-session channel, not here).
     #[serde(rename_all = "camelCase")]
     PtyOutput {
@@ -185,6 +203,15 @@ impl From<&DomainEvent> for DomainEventDto {
                 action: action.clone(),
                 ok: *ok,
             },
+            DomainEvent::MemorySaved { slug } => Self::MemorySaved {
+                slug: slug.as_str().to_string(),
+            },
+            DomainEvent::MemoryDeleted { slug } => Self::MemoryDeleted {
+                slug: slug.as_str().to_string(),
+            },
+            DomainEvent::MemoryIndexRebuilt { project_id } => Self::MemoryIndexRebuilt {
+                project_id: project_id.to_string(),
+            },
             DomainEvent::PtyOutput { session_id, bytes } => Self::PtyOutput {
                 session_id: session_id.to_string(),
                 bytes: bytes.clone(),

crates/app-tauri/src/lib.rs

@@ -140,6 +140,14 @@ pub fn run() {
             commands::delete_skill,
             commands::assign_skill_to_agent,
             commands::unassign_skill_from_agent,
+            commands::create_memory,
+            commands::update_memory,
+            commands::list_memories,
+            commands::get_memory,
+            commands::delete_memory,
+            commands::read_memory_index,
+            commands::recall_memory,
+            commands::resolve_memory_links,
             commands::move_tab_to_new_window,
         ])
         .run(tauri::generate_context!())

crates/app-tauri/src/state.rs

@@ -19,19 +19,22 @@ use application::{
     OpenTerminal, OrchestratorService, ReadAgentContext, ReferenceProfiles, RenameLayout,
     ResizeTerminal, SaveProfile, SetActiveLayout, SnapshotRunningAgents,
     AssignSkillToAgent, CreateSkill, DeleteSkill, UnassignSkillFromAgent, UpdateSkill,
+    CreateMemory, DeleteMemory, GetMemory, ListMemories, ReadMemoryIndex, RecallMemory,
+    ResolveMemoryLinks, UpdateMemory,
     SyncAgentWithTemplate, TerminalSessions, UpdateAgentContext, UpdateTemplate, WriteToTerminal,
 };
 use domain::ports::{
     AgentContextStore, AgentRuntime, Clock, EventBus, FileSystem, GitPort, IdGenerator,
-    ProcessSpawner, ProfileStore, ProjectStore, PtyPort, SkillStore, TemplateStore,
+    MemoryRecall, MemoryStore, ProcessSpawner, ProfileStore, ProjectStore, PtyPort, SkillStore,
+    TemplateStore,
 };
 use domain::{DomainEvent, Project, ProjectId};
 
 use infrastructure::{
     ClaudeTranscriptInspector, CliAgentRuntime, FsOrchestratorWatcher, FsProfileStore,
-    FsProjectStore, FsSkillStore, FsTemplateStore, Git2Repository, IdeaiContextStore,
+    FsMemoryStore, FsProjectStore, FsSkillStore, FsTemplateStore, Git2Repository, IdeaiContextStore,
-    LocalFileSystem, LocalProcessSpawner, OrchestratorWatchHandle, PortablePtyAdapter, SystemClock,
+    LocalFileSystem, LocalProcessSpawner, NaiveMemoryRecall, OrchestratorWatchHandle,
-    TokioBroadcastEventBus, UuidGenerator,
+    PortablePtyAdapter, SystemClock, TokioBroadcastEventBus, UuidGenerator,
 };
 
 use crate::pty::PtyBridge;
@@ -172,6 +175,25 @@ pub struct AppState {
     pub assign_skill: Arc<AssignSkillToAgent>,
     /// Unassign a skill from an agent.
     pub unassign_skill: Arc<UnassignSkillFromAgent>,
+
+    // --- Memory (LOT A — §14.5.1) ---
+    /// Create a memory note in the project's store.
+    pub create_memory: Arc<CreateMemory>,
+    /// Replace an existing memory note.
+    pub update_memory: Arc<UpdateMemory>,
+    /// List the project's memory notes.
+    pub list_memories: Arc<ListMemories>,
+    /// Read one memory note by slug.
+    pub get_memory: Arc<GetMemory>,
+    /// Delete a memory note.
+    pub delete_memory: Arc<DeleteMemory>,
+    /// Read the structured `MEMORY.md` index.
+    pub read_memory_index: Arc<ReadMemoryIndex>,
+    /// Resolve a note's outgoing `[[slug]]` links.
+    pub resolve_memory_links: Arc<ResolveMemoryLinks>,
+    /// Recall the most relevant memory entries for a query within a budget
+    /// (LOT B — §14.5.2).
+    pub recall_memory: Arc<RecallMemory>,
     // --- Orchestrator (§14.3) ---
     /// Dispatches validated orchestrator requests to the agent/skill use cases.
     /// Shared by every per-project filesystem watcher.
@@ -458,6 +480,36 @@ impl AppState {
             Arc::clone(&events_port),
         ));
 
+        // --- Memory store + use cases (LOT A — §14.5.1) ---
+        // A single FsMemoryStore takes the project root per call (like the skill
+        // store), so one instance serves every open project. The mutating use
+        // cases share the event bus to announce Memory{Saved,Deleted}.
+        let memory_store = Arc::new(FsMemoryStore::new(Arc::clone(&fs_port)));
+        let memory_store_port = Arc::clone(&memory_store) as Arc<dyn MemoryStore>;
+        let create_memory = Arc::new(CreateMemory::new(
+            Arc::clone(&memory_store_port),
+            Arc::clone(&events_port),
+        ));
+        let update_memory = Arc::new(UpdateMemory::new(
+            Arc::clone(&memory_store_port),
+            Arc::clone(&events_port),
+        ));
+        let list_memories = Arc::new(ListMemories::new(Arc::clone(&memory_store_port)));
+        let get_memory = Arc::new(GetMemory::new(Arc::clone(&memory_store_port)));
+        let delete_memory = Arc::new(DeleteMemory::new(
+            Arc::clone(&memory_store_port),
+            Arc::clone(&events_port),
+        ));
+        let read_memory_index = Arc::new(ReadMemoryIndex::new(Arc::clone(&memory_store_port)));
+        let resolve_memory_links =
+            Arc::new(ResolveMemoryLinks::new(Arc::clone(&memory_store_port)));
+        // Naïve recall (LOT B): composes the same store, returns index entries in
+        // order, truncated to the token budget. The default, dependency-free
+        // MemoryRecall; substitutable by a VectorMemoryRecall (LOT C).
+        let memory_recall_port =
+            Arc::new(NaiveMemoryRecall::new(Arc::clone(&memory_store_port))) as Arc<dyn MemoryRecall>;
+        let recall_memory = Arc::new(RecallMemory::new(memory_recall_port));
+
         // --- Orchestrator service (§14.3) ---
         // Dispatches file-based orchestrator requests through the *same* use cases
         // the UI drives (IdeA stays the single source of truth for the agent/skill
@@ -540,6 +592,14 @@ impl AppState {
             delete_skill,
             assign_skill,
             unassign_skill,
+            create_memory,
+            update_memory,
+            list_memories,
+            get_memory,
+            delete_memory,
+            read_memory_index,
+            resolve_memory_links,
+            recall_memory,
             orchestrator_service,
             orchestrator_watchers: Mutex::new(HashMap::new()),
             move_tab,

crates/application/src/error.rs

@@ -6,7 +6,8 @@
 //! with one error shape when building its `ErrorDTO`.
 
 use domain::ports::{
-    FsError, GitError, ProcessError, PtyError, RemoteError, RuntimeError, StoreError,
+    EmbedderError, FsError, GitError, MemoryError, ProcessError, PtyError, RemoteError,
+    RuntimeError, StoreError,
 };
 
 /// Errors surfaced by application use cases.
@@ -84,6 +85,26 @@ impl From<StoreError> for AppError {
     }
 }
 
+impl From<MemoryError> for AppError {
+    fn from(e: MemoryError) -> Self {
+        match e {
+            MemoryError::NotFound => Self::NotFound("memory note".to_owned()),
+            MemoryError::Frontmatter(m) => Self::Invalid(m),
+            other => Self::Store(other.to_string()),
+        }
+    }
+}
+
+impl From<EmbedderError> for AppError {
+    /// Maps to [`AppError::Store`] — an embedder is a *derived* recall detail; its
+    /// failure must degrade the recall (fallback to naïve), never fail hard. This
+    /// mapping exists for completeness; recall adapters degrade *before* an
+    /// embedder error ever reaches a use case.
+    fn from(e: EmbedderError) -> Self {
+        Self::Store(e.to_string())
+    }
+}
+
 impl From<PtyError> for AppError {
     fn from(e: PtyError) -> Self {
         Self::Process(e.to_string())

crates/application/src/lib.rs

@@ -16,6 +16,7 @@ pub mod error;
 pub mod git;
 pub mod health;
 pub mod layout;
+pub mod memory;
 pub mod orchestrator;
 pub mod project;
 pub mod remote;
@@ -53,6 +54,13 @@ pub use layout::{
     RenameLayoutInput, SetActiveLayout, SetActiveLayoutInput, SnapshotRunningAgents,
     SnapshotRunningAgentsInput, SnapshotRunningAgentsOutput, LAYOUTS_FILE,
 };
+pub use memory::{
+    CreateMemory, CreateMemoryInput, CreateMemoryOutput, DeleteMemory, DeleteMemoryInput,
+    GetMemory, GetMemoryInput, GetMemoryOutput, ListMemories, ListMemoriesInput, ListMemoriesOutput,
+    ReadMemoryIndex, ReadMemoryIndexInput, ReadMemoryIndexOutput, RecallMemory, RecallMemoryInput,
+    RecallMemoryOutput, ResolveMemoryLinks, ResolveMemoryLinksInput, ResolveMemoryLinksOutput,
+    UpdateMemory, UpdateMemoryInput, UpdateMemoryOutput,
+};
 pub use project::{
     CloseProject, CloseProjectInput, CloseProjectOutput, CloseTab, CloseTabInput, CreateProject,
     CreateProjectInput, CreateProjectOutput, ListProjects, ListProjectsOutput, OpenProject,

crates/application/src/memory/mod.rs

@@ -0,0 +1,23 @@
+//! Memory use cases (ARCHITECTURE §14.5.1; LOT A, étage 1: `.md`).
+//!
+//! The memory module owns the CRUD of a project's persistent knowledge base —
+//! one Markdown note per [`domain::memory::Memory`], stored under
+//! `.ideai/memory/<slug>.md` with a derived `MEMORY.md` index. On top of the
+//! CRUD it exposes two read-only navigation helpers driving the graphical memory
+//! view: [`ReadMemoryIndex`] (the structured index) and [`ResolveMemoryLinks`]
+//! (a note's resolved `[[slug]]` outgoing links, broken links dropped).
+//!
+//! Every use case talks only to ports ([`domain::ports::MemoryStore`],
+//! [`domain::ports::EventBus`]). Mutating use cases ([`CreateMemory`],
+//! [`UpdateMemory`], [`DeleteMemory`]) announce a [`domain::DomainEvent`]; the
+//! read use cases emit nothing.
+
+mod usecases;
+
+pub use usecases::{
+    CreateMemory, CreateMemoryInput, CreateMemoryOutput, DeleteMemory, DeleteMemoryInput,
+    GetMemory, GetMemoryInput, GetMemoryOutput, ListMemories, ListMemoriesInput, ListMemoriesOutput,
+    ReadMemoryIndex, ReadMemoryIndexInput, ReadMemoryIndexOutput, RecallMemory, RecallMemoryInput,
+    RecallMemoryOutput, ResolveMemoryLinks, ResolveMemoryLinksInput, ResolveMemoryLinksOutput,
+    UpdateMemory, UpdateMemoryInput, UpdateMemoryOutput,
+};

crates/application/src/memory/usecases.rs

@@ -0,0 +1,414 @@
+//! Memory use cases (ARCHITECTURE §14.5.1).
+//!
+//! - **CRUD**: [`CreateMemory`], [`UpdateMemory`], [`GetMemory`],
+//!   [`ListMemories`], [`DeleteMemory`].
+//! - **Navigation** (read-only): [`ReadMemoryIndex`] (structured `MEMORY.md`
+//!   rows) and [`ResolveMemoryLinks`] (a note's outgoing `[[slug]]` links).
+//!
+//! Mutating use cases announce a [`DomainEvent`]; the read use cases emit none.
+
+use std::sync::Arc;
+
+use domain::ports::{EventBus, MemoryQuery, MemoryRecall, MemoryStore};
+use domain::{
+    DomainEvent, MarkdownDoc, Memory, MemoryFrontmatter, MemoryIndexEntry, MemoryLink, MemorySlug,
+    MemoryType, ProjectPath,
+};
+
+use crate::error::AppError;
+
+// ---------------------------------------------------------------------------
+// CreateMemory
+// ---------------------------------------------------------------------------
+
+/// Input for [`CreateMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CreateMemoryInput {
+    /// Active project root (the note is stored under its `.ideai/memory/`).
+    pub project_root: ProjectPath,
+    /// Raw slug for the new note (validated into a [`MemorySlug`]).
+    pub name: String,
+    /// Human-readable one-line description (the index hook). Non-empty.
+    pub description: String,
+    /// The note's kind.
+    pub r#type: MemoryType,
+    /// Markdown body of the note.
+    pub content: String,
+}
+
+/// Output of [`CreateMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CreateMemoryOutput {
+    /// The created note.
+    pub memory: Memory,
+}
+
+/// Creates a memory note in the project's store and upserts the index.
+///
+/// Announces [`DomainEvent::MemorySaved`] on success.
+pub struct CreateMemory {
+    memories: Arc<dyn MemoryStore>,
+    events: Arc<dyn EventBus>,
+}
+
+impl CreateMemory {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>, events: Arc<dyn EventBus>) -> Self {
+        Self { memories, events }
+    }
+
+    /// Executes creation.
+    ///
+    /// # Errors
+    /// - [`AppError::Invalid`] if `name` is not a valid kebab-case slug or the
+    ///   note's invariants are violated (empty description/body),
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: CreateMemoryInput) -> Result<CreateMemoryOutput, AppError> {
+        let slug = MemorySlug::new(input.name).map_err(|e| AppError::Invalid(e.to_string()))?;
+        let frontmatter = MemoryFrontmatter {
+            name: slug.clone(),
+            description: input.description,
+            r#type: input.r#type,
+        };
+        let memory = Memory::new(frontmatter, MarkdownDoc::new(input.content))
+            .map_err(|e| AppError::Invalid(e.to_string()))?;
+        self.memories.save(&input.project_root, &memory).await?;
+        self.events.publish(DomainEvent::MemorySaved { slug });
+        Ok(CreateMemoryOutput { memory })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// UpdateMemory
+// ---------------------------------------------------------------------------
+
+/// Input for [`UpdateMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct UpdateMemoryInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+    /// Slug of the note to replace.
+    pub slug: MemorySlug,
+    /// New description (the index hook). Non-empty.
+    pub description: String,
+    /// New kind.
+    pub r#type: MemoryType,
+    /// New Markdown body.
+    pub content: String,
+}
+
+/// Output of [`UpdateMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct UpdateMemoryOutput {
+    /// The updated note.
+    pub memory: Memory,
+}
+
+/// Replaces a memory note's content (re-validating its invariants).
+///
+/// Announces [`DomainEvent::MemorySaved`] on success. The input carries the full
+/// note, so no prior `get` is needed — this is replace semantics.
+pub struct UpdateMemory {
+    memories: Arc<dyn MemoryStore>,
+    events: Arc<dyn EventBus>,
+}
+
+impl UpdateMemory {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>, events: Arc<dyn EventBus>) -> Self {
+        Self { memories, events }
+    }
+
+    /// Executes the update.
+    ///
+    /// # Errors
+    /// - [`AppError::Invalid`] if the note's invariants are violated (empty
+    ///   description/body),
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: UpdateMemoryInput) -> Result<UpdateMemoryOutput, AppError> {
+        let frontmatter = MemoryFrontmatter {
+            name: input.slug.clone(),
+            description: input.description,
+            r#type: input.r#type,
+        };
+        let memory = Memory::new(frontmatter, MarkdownDoc::new(input.content))
+            .map_err(|e| AppError::Invalid(e.to_string()))?;
+        self.memories.save(&input.project_root, &memory).await?;
+        self.events.publish(DomainEvent::MemorySaved { slug: input.slug });
+        Ok(UpdateMemoryOutput { memory })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// ListMemories
+// ---------------------------------------------------------------------------
+
+/// Input for [`ListMemories::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ListMemoriesInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+}
+
+/// Output of [`ListMemories::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ListMemoriesOutput {
+    /// All notes in the project.
+    pub memories: Vec<Memory>,
+}
+
+/// Lists the memory notes of a project.
+pub struct ListMemories {
+    memories: Arc<dyn MemoryStore>,
+}
+
+impl ListMemories {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>) -> Self {
+        Self { memories }
+    }
+
+    /// Lists the project's notes.
+    ///
+    /// # Errors
+    /// - [`AppError::Invalid`] if a note's frontmatter is malformed,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: ListMemoriesInput) -> Result<ListMemoriesOutput, AppError> {
+        Ok(ListMemoriesOutput {
+            memories: self.memories.list(&input.project_root).await?,
+        })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// GetMemory
+// ---------------------------------------------------------------------------
+
+/// Input for [`GetMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct GetMemoryInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+    /// Slug of the note to read.
+    pub slug: MemorySlug,
+}
+
+/// Output of [`GetMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct GetMemoryOutput {
+    /// The requested note.
+    pub memory: Memory,
+}
+
+/// Reads one memory note by slug.
+pub struct GetMemory {
+    memories: Arc<dyn MemoryStore>,
+}
+
+impl GetMemory {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>) -> Self {
+        Self { memories }
+    }
+
+    /// Reads the note.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if no note carries that slug,
+    /// - [`AppError::Invalid`] if the note's frontmatter is malformed,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: GetMemoryInput) -> Result<GetMemoryOutput, AppError> {
+        Ok(GetMemoryOutput {
+            memory: self.memories.get(&input.project_root, &input.slug).await?,
+        })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// DeleteMemory
+// ---------------------------------------------------------------------------
+
+/// Input for [`DeleteMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct DeleteMemoryInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+    /// Slug of the note to delete.
+    pub slug: MemorySlug,
+}
+
+/// Deletes a memory note (and removes its index row).
+///
+/// Announces [`DomainEvent::MemoryDeleted`] on success.
+pub struct DeleteMemory {
+    memories: Arc<dyn MemoryStore>,
+    events: Arc<dyn EventBus>,
+}
+
+impl DeleteMemory {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>, events: Arc<dyn EventBus>) -> Self {
+        Self { memories, events }
+    }
+
+    /// Deletes the note.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if no note carries that slug,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: DeleteMemoryInput) -> Result<(), AppError> {
+        self.memories.delete(&input.project_root, &input.slug).await?;
+        self.events.publish(DomainEvent::MemoryDeleted { slug: input.slug });
+        Ok(())
+    }
+}
+
+// ---------------------------------------------------------------------------
+// ReadMemoryIndex
+// ---------------------------------------------------------------------------
+
+/// Input for [`ReadMemoryIndex::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ReadMemoryIndexInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+}
+
+/// Output of [`ReadMemoryIndex::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ReadMemoryIndexOutput {
+    /// One row per note in the aggregated `MEMORY.md` index.
+    pub entries: Vec<MemoryIndexEntry>,
+}
+
+/// Reads the structured `MEMORY.md` index (drives the graphical memory view).
+pub struct ReadMemoryIndex {
+    memories: Arc<dyn MemoryStore>,
+}
+
+impl ReadMemoryIndex {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>) -> Self {
+        Self { memories }
+    }
+
+    /// Reads the index rows.
+    ///
+    /// # Errors
+    /// - [`AppError::Store`] on an I/O failure.
+    pub async fn execute(
+        &self,
+        input: ReadMemoryIndexInput,
+    ) -> Result<ReadMemoryIndexOutput, AppError> {
+        Ok(ReadMemoryIndexOutput {
+            entries: self.memories.read_index(&input.project_root).await?,
+        })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// RecallMemory
+// ---------------------------------------------------------------------------
+
+/// Input for [`RecallMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RecallMemoryInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+    /// The recall query (often the agent's current working context).
+    pub text: String,
+    /// Approximate token budget bounding the returned entries (`0` ⇒ empty).
+    pub token_budget: usize,
+}
+
+/// Output of [`RecallMemory::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct RecallMemoryOutput {
+    /// The recalled index entries, in relevance order, fitting the budget.
+    pub entries: Vec<MemoryIndexEntry>,
+}
+
+/// Recalls the most relevant memory entries for a query within a token budget
+/// (LOT B, étage 1). Read-only — emits no event.
+pub struct RecallMemory {
+    recall: Arc<dyn MemoryRecall>,
+}
+
+impl RecallMemory {
+    /// Builds the use case from the [`MemoryRecall`] port.
+    #[must_use]
+    pub fn new(recall: Arc<dyn MemoryRecall>) -> Self {
+        Self { recall }
+    }
+
+    /// Executes recall. Best-effort: an empty or absent memory yields an empty
+    /// list, and a budget of `0` yields an empty list.
+    ///
+    /// # Errors
+    /// - [`AppError::Store`] on an unexpected I/O failure of the underlying store.
+    pub async fn execute(&self, input: RecallMemoryInput) -> Result<RecallMemoryOutput, AppError> {
+        let query = MemoryQuery {
+            text: input.text,
+            token_budget: input.token_budget,
+        };
+        Ok(RecallMemoryOutput {
+            entries: self.recall.recall(&input.project_root, &query).await?,
+        })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// ResolveMemoryLinks
+// ---------------------------------------------------------------------------
+
+/// Input for [`ResolveMemoryLinks::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ResolveMemoryLinksInput {
+    /// Active project root.
+    pub project_root: ProjectPath,
+    /// Slug of the source note whose outgoing links are resolved.
+    pub slug: MemorySlug,
+}
+
+/// Output of [`ResolveMemoryLinks::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ResolveMemoryLinksOutput {
+    /// The note's resolved outgoing `[[slug]]` links (broken links dropped).
+    pub links: Vec<MemoryLink>,
+}
+
+/// Resolves a note's outgoing `[[slug]]` links (drives link navigation).
+pub struct ResolveMemoryLinks {
+    memories: Arc<dyn MemoryStore>,
+}
+
+impl ResolveMemoryLinks {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(memories: Arc<dyn MemoryStore>) -> Self {
+        Self { memories }
+    }
+
+    /// Resolves the outgoing links.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the source note does not exist,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(
+        &self,
+        input: ResolveMemoryLinksInput,
+    ) -> Result<ResolveMemoryLinksOutput, AppError> {
+        Ok(ResolveMemoryLinksOutput {
+            links: self
+                .memories
+                .resolve_links(&input.project_root, &input.slug)
+                .await?,
+        })
+    }
+}

crates/application/tests/error_codes.rs

@@ -2,7 +2,9 @@
 //! relies on, and the per-port `From` mappings.
 
 use application::AppError;
-use domain::ports::{FsError, GitError, ProcessError, PtyError, RemoteError, StoreError};
+use domain::ports::{
+    EmbedderError, FsError, GitError, MemoryError, ProcessError, PtyError, RemoteError, StoreError,
+};
 
 #[test]
 fn codes_are_stable() {
@@ -55,3 +57,43 @@ fn git_and_remote_map_through() {
         "REMOTE"
     );
 }
+
+#[test]
+fn memory_errors_map_per_variant() {
+    // NotFound → NotFound.
+    assert_eq!(AppError::from(MemoryError::NotFound).code(), "NOT_FOUND");
+    // Frontmatter → Invalid (a malformed note is an invariant violation, not I/O).
+    let invalid = AppError::from(MemoryError::Frontmatter("bad yaml".into()));
+    assert_eq!(invalid.code(), "INVALID");
+    assert_eq!(invalid, AppError::Invalid("bad yaml".to_owned()));
+    // Io → Store.
+    assert_eq!(AppError::from(MemoryError::Io("disk full".into())).code(), "STORE");
+    // Serialization → Store (the catch-all arm).
+    assert_eq!(
+        AppError::from(MemoryError::Serialization("bad index".into())).code(),
+        "STORE"
+    );
+}
+
+#[test]
+fn embedder_errors_all_map_to_store() {
+    // An embedder is a *derived* recall detail: every variant maps to STORE (its
+    // failure must degrade the recall, never fail hard — see the From impl doc).
+    assert_eq!(
+        AppError::from(EmbedderError::Unavailable("no model".into())).code(),
+        "STORE"
+    );
+    assert_eq!(
+        AppError::from(EmbedderError::Unsupported("localOnnx".into())).code(),
+        "STORE"
+    );
+    assert_eq!(
+        AppError::from(EmbedderError::Io("read failed".into())).code(),
+        "STORE"
+    );
+    // The message is carried through.
+    assert_eq!(
+        AppError::from(EmbedderError::Unsupported("api".into())),
+        AppError::Store("embedder strategy unsupported: api".to_owned())
+    );
+}

crates/application/tests/memory_usecases.rs

@@ -0,0 +1,632 @@
+//! L12 tests for the memory use cases (ARCHITECTURE §14.5.1) with in-memory
+//! port fakes (no real store/FS): CRUD (`CreateMemory`, `UpdateMemory`,
+//! `GetMemory`, `ListMemories`, `DeleteMemory`) asserting the `MemorySaved` /
+//! `MemoryDeleted` events, and the read-only navigation helpers
+//! (`ReadMemoryIndex`, `ResolveMemoryLinks`) asserting they emit nothing.
+
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+use domain::events::DomainEvent;
+use domain::ports::{EventBus, EventStream, MemoryError, MemoryQuery, MemoryRecall, MemoryStore};
+use domain::{
+    MarkdownDoc, Memory, MemoryFrontmatter, MemoryIndexEntry, MemoryLink, MemorySlug, MemoryType,
+    ProjectPath,
+};
+
+use application::{
+    CreateMemory, CreateMemoryInput, DeleteMemory, DeleteMemoryInput, GetMemory, GetMemoryInput,
+    ListMemories, ListMemoriesInput, ReadMemoryIndex, ReadMemoryIndexInput, RecallMemory,
+    RecallMemoryInput, ResolveMemoryLinks, ResolveMemoryLinksInput, UpdateMemory, UpdateMemoryInput,
+};
+
+// ---------------------------------------------------------------------------
+// Fakes
+// ---------------------------------------------------------------------------
+
+/// In-memory memory store keyed by slug. Index and links are derived from the
+/// stored notes (mirroring the real adapter), so navigation reads stay honest.
+#[derive(Clone, Default)]
+struct FakeMemories(Arc<Mutex<Vec<Memory>>>);
+
+#[async_trait]
+impl MemoryStore for FakeMemories {
+    async fn list(&self, _root: &ProjectPath) -> Result<Vec<Memory>, MemoryError> {
+        Ok(self.0.lock().unwrap().clone())
+    }
+
+    async fn get(&self, _root: &ProjectPath, slug: &MemorySlug) -> Result<Memory, MemoryError> {
+        self.0
+            .lock()
+            .unwrap()
+            .iter()
+            .find(|m| m.slug() == slug)
+            .cloned()
+            .ok_or(MemoryError::NotFound)
+    }
+
+    async fn save(&self, _root: &ProjectPath, memory: &Memory) -> Result<(), MemoryError> {
+        let mut v = self.0.lock().unwrap();
+        if let Some(slot) = v.iter_mut().find(|m| m.slug() == memory.slug()) {
+            *slot = memory.clone();
+        } else {
+            v.push(memory.clone());
+        }
+        Ok(())
+    }
+
+    async fn delete(&self, _root: &ProjectPath, slug: &MemorySlug) -> Result<(), MemoryError> {
+        let mut v = self.0.lock().unwrap();
+        let before = v.len();
+        v.retain(|m| m.slug() != slug);
+        if v.len() == before {
+            return Err(MemoryError::NotFound);
+        }
+        Ok(())
+    }
+
+    async fn read_index(
+        &self,
+        _root: &ProjectPath,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        Ok(self
+            .0
+            .lock()
+            .unwrap()
+            .iter()
+            .map(Memory::index_entry)
+            .collect())
+    }
+
+    async fn resolve_links(
+        &self,
+        _root: &ProjectPath,
+        slug: &MemorySlug,
+    ) -> Result<Vec<MemoryLink>, MemoryError> {
+        let v = self.0.lock().unwrap();
+        let source = v
+            .iter()
+            .find(|m| m.slug() == slug)
+            .ok_or(MemoryError::NotFound)?;
+        // Mirror the adapter: drop links whose target note does not exist.
+        Ok(source
+            .outgoing_links()
+            .into_iter()
+            .filter(|l| v.iter().any(|m| m.slug() == &l.target))
+            .collect())
+    }
+}
+
+#[derive(Default, Clone)]
+struct SpyBus(Arc<Mutex<Vec<DomainEvent>>>);
+impl SpyBus {
+    fn events(&self) -> Vec<DomainEvent> {
+        self.0.lock().unwrap().clone()
+    }
+}
+impl EventBus for SpyBus {
+    fn publish(&self, event: DomainEvent) {
+        self.0.lock().unwrap().push(event);
+    }
+    fn subscribe(&self) -> EventStream {
+        Box::new(std::iter::empty())
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Builders
+// ---------------------------------------------------------------------------
+
+fn root() -> ProjectPath {
+    ProjectPath::new("/home/me/demo").unwrap()
+}
+
+fn slug(s: &str) -> MemorySlug {
+    MemorySlug::new(s).unwrap()
+}
+
+/// Builds and persists a note directly through the store (bypassing use cases).
+async fn seed(store: &FakeMemories, name: &str, body: &str) {
+    let memory = Memory::new(
+        MemoryFrontmatter {
+            name: slug(name),
+            description: format!("{name} hook"),
+            r#type: MemoryType::Project,
+        },
+        MarkdownDoc::new(body),
+    )
+    .unwrap();
+    store.save(&root(), &memory).await.unwrap();
+}
+
+fn saved_slugs(events: &[DomainEvent]) -> Vec<MemorySlug> {
+    events
+        .iter()
+        .filter_map(|e| match e {
+            DomainEvent::MemorySaved { slug } => Some(slug.clone()),
+            _ => None,
+        })
+        .collect()
+}
+
+fn deleted_slugs(events: &[DomainEvent]) -> Vec<MemorySlug> {
+    events
+        .iter()
+        .filter_map(|e| match e {
+            DomainEvent::MemoryDeleted { slug } => Some(slug.clone()),
+            _ => None,
+        })
+        .collect()
+}
+
+// ---------------------------------------------------------------------------
+// CreateMemory
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn create_persists_note_and_emits_memory_saved_with_slug() {
+    let store = FakeMemories::default();
+    let bus = SpyBus::default();
+    let out = CreateMemory::new(Arc::new(store.clone()), Arc::new(bus.clone()))
+        .execute(CreateMemoryInput {
+            project_root: root(),
+            name: "design-decision".to_owned(),
+            description: "why we chose hexagonal".to_owned(),
+            r#type: MemoryType::Project,
+            content: "# body".to_owned(),
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(out.memory.slug(), &slug("design-decision"));
+    // Persisted.
+    let listed = store.list(&root()).await.unwrap();
+    assert_eq!(listed.len(), 1);
+    assert_eq!(listed[0].slug(), &slug("design-decision"));
+    // Emits exactly one MemorySaved with the right slug.
+    assert_eq!(saved_slugs(&bus.events()), vec![slug("design-decision")]);
+}
+
+#[tokio::test]
+async fn create_rejects_non_kebab_name_as_invalid() {
+    let store = FakeMemories::default();
+    let bus = SpyBus::default();
+    let err = CreateMemory::new(Arc::new(store.clone()), Arc::new(bus.clone()))
+        .execute(CreateMemoryInput {
+            project_root: root(),
+            name: "Not Kebab".to_owned(),
+            description: "x".to_owned(),
+            r#type: MemoryType::User,
+            content: "# body".to_owned(),
+        })
+        .await
+        .unwrap_err();
+
+    assert_eq!(err.code(), "INVALID");
+    // Nothing persisted, nothing announced.
+    assert!(store.list(&root()).await.unwrap().is_empty());
+    assert!(bus.events().is_empty());
+}
+
+#[tokio::test]
+async fn create_rejects_empty_description() {
+    let store = FakeMemories::default();
+    let bus = SpyBus::default();
+    let err = CreateMemory::new(Arc::new(store), Arc::new(bus))
+        .execute(CreateMemoryInput {
+            project_root: root(),
+            name: "ok-slug".to_owned(),
+            description: String::new(),
+            r#type: MemoryType::User,
+            content: "# body".to_owned(),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "INVALID");
+}
+
+#[tokio::test]
+async fn create_rejects_empty_content() {
+    let store = FakeMemories::default();
+    let bus = SpyBus::default();
+    let err = CreateMemory::new(Arc::new(store), Arc::new(bus))
+        .execute(CreateMemoryInput {
+            project_root: root(),
+            name: "ok-slug".to_owned(),
+            description: "a hook".to_owned(),
+            r#type: MemoryType::User,
+            content: String::new(),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "INVALID");
+}
+
+// ---------------------------------------------------------------------------
+// UpdateMemory
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn update_replaces_content_and_emits_memory_saved() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "v1").await;
+    let bus = SpyBus::default();
+
+    let out = UpdateMemory::new(Arc::new(store.clone()), Arc::new(bus.clone()))
+        .execute(UpdateMemoryInput {
+            project_root: root(),
+            slug: slug("note-a"),
+            description: "updated hook".to_owned(),
+            r#type: MemoryType::Reference,
+            content: "v2".to_owned(),
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(out.memory.body.as_str(), "v2");
+    assert_eq!(out.memory.frontmatter.description, "updated hook");
+    assert_eq!(out.memory.frontmatter.r#type, MemoryType::Reference);
+    // Replace semantics: still a single note.
+    let listed = store.list(&root()).await.unwrap();
+    assert_eq!(listed.len(), 1);
+    assert_eq!(listed[0].body.as_str(), "v2");
+    assert_eq!(saved_slugs(&bus.events()), vec![slug("note-a")]);
+}
+
+#[tokio::test]
+async fn update_revalidates_invariants_and_rejects_empty_content() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "v1").await;
+    let bus = SpyBus::default();
+
+    let err = UpdateMemory::new(Arc::new(store.clone()), Arc::new(bus.clone()))
+        .execute(UpdateMemoryInput {
+            project_root: root(),
+            slug: slug("note-a"),
+            description: "still here".to_owned(),
+            r#type: MemoryType::Project,
+            content: String::new(),
+        })
+        .await
+        .unwrap_err();
+
+    assert_eq!(err.code(), "INVALID");
+    // Original note untouched, no event.
+    assert_eq!(store.get(&root(), &slug("note-a")).await.unwrap().body.as_str(), "v1");
+    assert!(bus.events().is_empty());
+}
+
+// ---------------------------------------------------------------------------
+// DeleteMemory
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn delete_removes_note_and_emits_memory_deleted() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "body").await;
+    let bus = SpyBus::default();
+
+    DeleteMemory::new(Arc::new(store.clone()), Arc::new(bus.clone()))
+        .execute(DeleteMemoryInput {
+            project_root: root(),
+            slug: slug("note-a"),
+        })
+        .await
+        .unwrap();
+
+    assert!(store.list(&root()).await.unwrap().is_empty());
+    assert_eq!(deleted_slugs(&bus.events()), vec![slug("note-a")]);
+}
+
+#[tokio::test]
+async fn delete_unknown_slug_is_not_found_and_emits_nothing() {
+    let store = FakeMemories::default();
+    let bus = SpyBus::default();
+
+    let err = DeleteMemory::new(Arc::new(store), Arc::new(bus.clone()))
+        .execute(DeleteMemoryInput {
+            project_root: root(),
+            slug: slug("ghost"),
+        })
+        .await
+        .unwrap_err();
+
+    assert_eq!(err.code(), "NOT_FOUND");
+    assert!(bus.events().is_empty());
+}
+
+// ---------------------------------------------------------------------------
+// GetMemory
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn get_returns_the_note() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "hello").await;
+
+    let out = GetMemory::new(Arc::new(store))
+        .execute(GetMemoryInput {
+            project_root: root(),
+            slug: slug("note-a"),
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(out.memory.slug(), &slug("note-a"));
+    assert_eq!(out.memory.body.as_str(), "hello");
+}
+
+#[tokio::test]
+async fn get_unknown_slug_is_not_found() {
+    let store = FakeMemories::default();
+    let err = GetMemory::new(Arc::new(store))
+        .execute(GetMemoryInput {
+            project_root: root(),
+            slug: slug("ghost"),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
+// ---------------------------------------------------------------------------
+// ListMemories
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn list_returns_all_notes() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "a").await;
+    seed(&store, "note-b", "b").await;
+
+    let out = ListMemories::new(Arc::new(store))
+        .execute(ListMemoriesInput {
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+
+    let mut slugs: Vec<_> = out.memories.iter().map(|m| m.slug().clone()).collect();
+    slugs.sort();
+    assert_eq!(slugs, vec![slug("note-a"), slug("note-b")]);
+}
+
+#[tokio::test]
+async fn list_is_empty_when_no_notes() {
+    let store = FakeMemories::default();
+    let out = ListMemories::new(Arc::new(store))
+        .execute(ListMemoriesInput {
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+    assert!(out.memories.is_empty());
+}
+
+// ---------------------------------------------------------------------------
+// ReadMemoryIndex
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn read_index_returns_one_row_per_note() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "a").await;
+    seed(&store, "note-b", "b").await;
+
+    let out = ReadMemoryIndex::new(Arc::new(store))
+        .execute(ReadMemoryIndexInput {
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(out.entries.len(), 2);
+    let mut rows: Vec<_> = out
+        .entries
+        .iter()
+        .map(|e| (e.slug.clone(), e.hook.clone()))
+        .collect();
+    rows.sort();
+    assert_eq!(
+        rows,
+        vec![
+            (slug("note-a"), "note-a hook".to_owned()),
+            (slug("note-b"), "note-b hook".to_owned()),
+        ]
+    );
+}
+
+// ---------------------------------------------------------------------------
+// ResolveMemoryLinks
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn resolve_links_returns_outgoing_links_dropping_broken_ones() {
+    let store = FakeMemories::default();
+    // note-a links to note-b (exists) and to ghost (does not).
+    seed(&store, "note-a", "see [[note-b]] and [[ghost]]").await;
+    seed(&store, "note-b", "target body").await;
+
+    let out = ResolveMemoryLinks::new(Arc::new(store))
+        .execute(ResolveMemoryLinksInput {
+            project_root: root(),
+            slug: slug("note-a"),
+        })
+        .await
+        .unwrap();
+
+    // Only the resolvable link survives; the broken one is dropped.
+    assert_eq!(
+        out.links,
+        vec![MemoryLink {
+            target: slug("note-b")
+        }]
+    );
+}
+
+#[tokio::test]
+async fn resolve_links_for_unknown_source_is_not_found() {
+    let store = FakeMemories::default();
+    let err = ResolveMemoryLinks::new(Arc::new(store))
+        .execute(ResolveMemoryLinksInput {
+            project_root: root(),
+            slug: slug("ghost"),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
+// ---------------------------------------------------------------------------
+// RecallMemory
+// ---------------------------------------------------------------------------
+
+/// In-memory [`MemoryRecall`] fake: records the queries it received and returns a
+/// canned set of entries. Lets us assert the use case delegates faithfully (same
+/// `root`, the input `text`/`token_budget` forwarded) and surfaces the result.
+#[derive(Clone, Default)]
+struct FakeRecall {
+    entries: Arc<Vec<MemoryIndexEntry>>,
+    seen: Arc<Mutex<Vec<MemoryQuery>>>,
+}
+
+impl FakeRecall {
+    fn returning(entries: Vec<MemoryIndexEntry>) -> Self {
+        Self {
+            entries: Arc::new(entries),
+            seen: Arc::default(),
+        }
+    }
+    fn queries(&self) -> Vec<MemoryQuery> {
+        self.seen.lock().unwrap().clone()
+    }
+}
+
+#[async_trait]
+impl MemoryRecall for FakeRecall {
+    async fn recall(
+        &self,
+        _root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        self.seen.lock().unwrap().push(query.clone());
+        Ok((*self.entries).clone())
+    }
+}
+
+fn entry(slug_str: &str, hook: &str) -> MemoryIndexEntry {
+    MemoryIndexEntry {
+        slug: slug(slug_str),
+        title: slug_str.to_owned(),
+        hook: hook.to_owned(),
+        r#type: MemoryType::Reference,
+    }
+}
+
+#[tokio::test]
+async fn recall_delegates_to_port_and_returns_entries() {
+    let recalled = vec![entry("alpha", "first"), entry("beta", "second")];
+    let recall = FakeRecall::returning(recalled.clone());
+
+    let out = RecallMemory::new(Arc::new(recall.clone()))
+        .execute(RecallMemoryInput {
+            project_root: root(),
+            text: "current context".to_owned(),
+            token_budget: 42,
+        })
+        .await
+        .unwrap();
+
+    // Returns exactly what the port produced, in order.
+    assert_eq!(out.entries, recalled);
+    // The query was forwarded verbatim (text + budget).
+    assert_eq!(
+        recall.queries(),
+        vec![MemoryQuery {
+            text: "current context".to_owned(),
+            token_budget: 42,
+        }]
+    );
+}
+
+#[tokio::test]
+async fn recall_empty_result_is_empty_not_error() {
+    let recall = FakeRecall::returning(Vec::new());
+    let out = RecallMemory::new(Arc::new(recall))
+        .execute(RecallMemoryInput {
+            project_root: root(),
+            text: String::new(),
+            token_budget: 0,
+        })
+        .await
+        .unwrap();
+    assert!(out.entries.is_empty());
+}
+
+#[tokio::test]
+async fn recall_publishes_no_events() {
+    // RecallMemory takes no EventBus; assert a shared spy stays empty when other
+    // (mutating) use cases on the same bus are NOT exercised — i.e. recall is
+    // read-only by construction.
+    let recall = FakeRecall::returning(vec![entry("alpha", "first")]);
+    let bus = SpyBus::default();
+
+    RecallMemory::new(Arc::new(recall))
+        .execute(RecallMemoryInput {
+            project_root: root(),
+            text: "ctx".to_owned(),
+            token_budget: 10,
+        })
+        .await
+        .unwrap();
+
+    assert!(
+        bus.events().is_empty(),
+        "recall must not publish any DomainEvent"
+    );
+}
+
+// ---------------------------------------------------------------------------
+// Read use cases emit no events
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn read_use_cases_publish_no_events() {
+    let store = FakeMemories::default();
+    seed(&store, "note-a", "see [[note-a]]").await;
+    let bus = SpyBus::default();
+
+    // None of the read use cases take an EventBus — assert the shared spy stays
+    // empty after exercising every read path on the same store.
+    GetMemory::new(Arc::new(store.clone()))
+        .execute(GetMemoryInput {
+            project_root: root(),
+            slug: slug("note-a"),
+        })
+        .await
+        .unwrap();
+    ListMemories::new(Arc::new(store.clone()))
+        .execute(ListMemoriesInput {
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+    ReadMemoryIndex::new(Arc::new(store.clone()))
+        .execute(ReadMemoryIndexInput {
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+    ResolveMemoryLinks::new(Arc::new(store))
+        .execute(ResolveMemoryLinksInput {
+            project_root: root(),
+            slug: slug("note-a"),
+        })
+        .await
+        .unwrap();
+
+    assert!(
+        bus.events().is_empty(),
+        "read use cases must not publish any DomainEvent"
+    );
+}

crates/domain/src/error.rs

@@ -65,6 +65,13 @@ pub enum DomainError {
         reason: String,
     },
 
+    /// A memory slug was not valid kebab-case (`[a-z0-9-]`, non-empty).
+    #[error("`{value}` is not a valid kebab-case slug")]
+    InvalidSlug {
+        /// The offending value.
+        value: String,
+    },
+
     /// A generic invariant violation with an explanatory message.
     #[error("invariant violated: {0}")]
     Invariant(String),

crates/domain/src/events.rs

@@ -2,6 +2,7 @@
 //! presentation layer (ARCHITECTURE §3.2).
 
 use crate::ids::{AgentId, ProjectId, SessionId, SkillId, TemplateId};
+use crate::memory::MemorySlug;
 use crate::template::TemplateVersion;
 
 /// Events emitted by the domain/application as state changes occur.
@@ -90,6 +91,21 @@ pub enum DomainEvent {
         /// Whether IdeA handled it successfully.
         ok: bool,
     },
+    /// A memory note was created or updated (`.md` written, index upserted).
+    MemorySaved {
+        /// The saved note's slug.
+        slug: MemorySlug,
+    },
+    /// A memory note was deleted.
+    MemoryDeleted {
+        /// The deleted note's slug.
+        slug: MemorySlug,
+    },
+    /// The aggregated `MEMORY.md` index was rebuilt for a project.
+    MemoryIndexRebuilt {
+        /// The project whose index was rebuilt.
+        project_id: ProjectId,
+    },
     /// Raw PTY output (usually routed to a dedicated channel, not this bus).
     PtyOutput {
         /// The session.

crates/domain/src/lib.rs

@@ -37,6 +37,7 @@ pub mod git;
 pub mod ids;
 pub mod layout;
 pub mod markdown;
+pub mod memory;
 pub mod orchestrator;
 pub mod ports;
 pub mod profile;
@@ -67,10 +68,16 @@ pub use skill::{Skill, SkillRef, SkillScope};
 
 pub use template::{AgentTemplate, TemplateVersion};
 
-pub use profile::{AgentProfile, ContextInjection, SessionStrategy};
+pub use profile::{
+    AgentProfile, ContextInjection, EmbedderProfile, EmbedderStrategy, SessionStrategy,
+};
 
 pub use markdown::MarkdownDoc;
 
+pub use memory::{
+    Memory, MemoryFrontmatter, MemoryIndexEntry, MemoryLink, MemorySlug, MemoryType,
+};
+
 pub use remote::{RemoteKind, RemoteRef, SshAuth};
 
 pub use terminal::{PtySize, SessionKind, SessionStatus, TerminalSession};
@@ -87,9 +94,11 @@ pub use events::DomainEvent;
 pub use orchestrator::{OrchestratorCommand, OrchestratorError, OrchestratorRequest};
 
 pub use ports::{
-    AgentContextStore, AgentRuntime, Clock, ContextInjectionPlan, DirEntry, EventBus, EventStream,
+    AgentContextStore, AgentRuntime, Clock, ContextInjectionPlan, DirEntry, Embedder,
+    EmbedderError, EventBus, EventStream,
     ExitStatus, FileSystem, FsError, GitCommitInfo, GitError, GitFileStatus, GitPort, GraphCommit,
-    IdGenerator, Output, OutputStream, PreparedContext, ProcessError, ProcessSpawner, ProfileStore,
+    IdGenerator, MemoryError, MemoryQuery, MemoryRecall, MemoryStore, Output, OutputStream,
-    ProjectStore, PtyError, PtyHandle, PtyPort, RemoteError, RemoteHost, RemotePath, RuntimeError,
+    PreparedContext, ProcessError,
-    SpawnSpec, StoreError, TemplateStore,
+    ProcessSpawner, ProfileStore, ProjectStore, PtyError, PtyHandle, PtyPort, RemoteError,
+    RemoteHost, RemotePath, RuntimeError, SpawnSpec, StoreError, TemplateStore,
 };

crates/domain/src/memory.rs

@@ -0,0 +1,194 @@
+//! Memory entity — the persistent, model-agnostic knowledge base of a project
+//! (LOT A, étage 1: `.md` files as the single source of truth).
+//!
+//! A [`Memory`] is one Markdown note stored under `.ideai/memory/<slug>.md`. Its
+//! frontmatter carries the structured metadata (a kebab-case [`MemorySlug`], a
+//! human-readable description, and a [`MemoryType`]); its body is opaque
+//! [`MarkdownDoc`] text. Notes cross-reference one another via `[[slug]]` wiki
+//! links, scanned by [`Memory::outgoing_links`].
+//!
+//! The aggregated `.ideai/memory/MEMORY.md` index (one [`MemoryIndexEntry`] line
+//! per note) is derived data: [`Memory::index_entry`] produces a note's row. The
+//! adapter (`FsMemoryStore`) owns the on-disk YAML frontmatter and index file
+//! formats; the domain stays I/O-free and format-neutral.
+
+use serde::{Deserialize, Serialize};
+
+use crate::error::DomainError;
+use crate::markdown::MarkdownDoc;
+
+/// A kebab-case identifier for a memory note (`[a-z0-9]` plus `-`), used both as
+/// the on-disk file stem (`<slug>.md`) and as the `[[slug]]` link target.
+///
+/// Invariants enforced by [`MemorySlug::new`]:
+/// - non-empty,
+/// - only lowercase ASCII letters, ASCII digits, and `-`,
+/// - therefore no uppercase, no whitespace, and no `.` (so no `..` traversal).
+#[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
+#[serde(transparent)]
+pub struct MemorySlug(String);
+
+impl MemorySlug {
+    /// Builds a validated kebab-case slug.
+    ///
+    /// # Errors
+    /// [`DomainError::InvalidSlug`] if `raw` is empty or contains any character
+    /// outside `[a-z0-9-]`.
+    pub fn new(raw: impl Into<String>) -> Result<Self, DomainError> {
+        let raw = raw.into();
+        let invalid = || DomainError::InvalidSlug {
+            value: raw.clone(),
+        };
+        if raw.is_empty() {
+            return Err(invalid());
+        }
+        if raw
+            .chars()
+            .all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '-')
+        {
+            Ok(Self(raw))
+        } else {
+            Err(invalid())
+        }
+    }
+
+    /// Returns the slug as a string slice.
+    #[must_use]
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}
+
+impl std::fmt::Display for MemorySlug {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+/// The kind of a memory note, driving how it is surfaced and prioritised.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum MemoryType {
+    /// A user-authored preference or instruction.
+    User,
+    /// Feedback captured from a prior interaction.
+    Feedback,
+    /// A project-level fact or decision.
+    Project,
+    /// A reference / external knowledge note.
+    Reference,
+}
+
+/// The structured frontmatter of a memory note.
+///
+/// Serialised with `type` (not `kind`) as the discriminator field name, matching
+/// the on-disk YAML `metadata.type` (the adapter maps the nesting). Invariant:
+/// `description` is non-empty (enforced at [`Memory::new`]).
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct MemoryFrontmatter {
+    /// Stable kebab-case identifier (also the file stem).
+    pub name: MemorySlug,
+    /// Human-readable one-line description (the index hook). Non-empty.
+    pub description: String,
+    /// The note's kind.
+    #[serde(rename = "type")]
+    pub r#type: MemoryType,
+}
+
+/// A `[[slug]]` wiki link found in a note's body, pointing at another note.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct MemoryLink {
+    /// The linked note's slug.
+    pub target: MemorySlug,
+}
+
+/// One row of the aggregated `MEMORY.md` index: the `- [Title](slug.md) — hook`
+/// line, decomposed into its parts.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct MemoryIndexEntry {
+    /// The note's slug.
+    pub slug: MemorySlug,
+    /// The note's display title (currently the slug; titles are derived later).
+    pub title: String,
+    /// The one-line hook (the frontmatter description).
+    pub hook: String,
+    /// The note's kind.
+    pub r#type: MemoryType,
+}
+
+/// A memory note: validated frontmatter plus an opaque Markdown body.
+///
+/// Invariants enforced by [`Memory::new`]:
+/// - `frontmatter.description` non-empty,
+/// - `body` non-empty (an empty note carries no knowledge).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Memory {
+    /// Structured metadata.
+    pub frontmatter: MemoryFrontmatter,
+    /// Markdown body of the note.
+    pub body: MarkdownDoc,
+}
+
+impl Memory {
+    /// Builds a validated memory note.
+    ///
+    /// # Errors
+    /// - [`DomainError::EmptyField`] if `frontmatter.description` is empty,
+    /// - [`DomainError::EmptyField`] if `body` is empty.
+    pub fn new(frontmatter: MemoryFrontmatter, body: MarkdownDoc) -> Result<Self, DomainError> {
+        crate::validation::non_empty(&frontmatter.description, "memory.description")?;
+        if body.is_empty() {
+            return Err(DomainError::EmptyField {
+                field: "memory.body",
+            });
+        }
+        Ok(Self { frontmatter, body })
+    }
+
+    /// Returns the note's slug (its identity).
+    #[must_use]
+    pub fn slug(&self) -> &MemorySlug {
+        &self.frontmatter.name
+    }
+
+    /// Scans the body for `[[slug]]` wiki links, in order of appearance.
+    ///
+    /// Tokens whose inner text is not a valid [`MemorySlug`] are skipped (a
+    /// malformed link is not a hard error here). Duplicates are preserved — the
+    /// caller dedups if it wants a unique link set. No regex: a small linear scan.
+    #[must_use]
+    pub fn outgoing_links(&self) -> Vec<MemoryLink> {
+        let text = self.body.as_str();
+        let bytes = text.as_bytes();
+        let mut links = Vec::new();
+        let mut i = 0;
+        while i + 1 < bytes.len() {
+            if bytes[i] == b'[' && bytes[i + 1] == b'[' {
+                // Find the closing `]]`.
+                if let Some(close) = text[i + 2..].find("]]") {
+                    let inner = &text[i + 2..i + 2 + close];
+                    if let Ok(target) = MemorySlug::new(inner) {
+                        links.push(MemoryLink { target });
+                    }
+                    i = i + 2 + close + 2;
+                    continue;
+                }
+                // No closing token: stop scanning further `[[`.
+                break;
+            }
+            i += 1;
+        }
+        links
+    }
+
+    /// Produces this note's row in the aggregated `MEMORY.md` index.
+    #[must_use]
+    pub fn index_entry(&self) -> MemoryIndexEntry {
+        MemoryIndexEntry {
+            slug: self.frontmatter.name.clone(),
+            title: self.frontmatter.name.as_str().to_string(),
+            hook: self.frontmatter.description.clone(),
+            r#type: self.frontmatter.r#type,
+        }
+    }
+}

crates/domain/src/ports.rs

@@ -31,6 +31,7 @@ use crate::agent::AgentManifest;
 use crate::events::DomainEvent;
 use crate::ids::{AgentId, SessionId};
 use crate::markdown::MarkdownDoc;
+use crate::memory::{Memory, MemoryIndexEntry, MemoryLink, MemorySlug};
 use crate::profile::AgentProfile;
 use crate::project::{Project, ProjectPath};
 use crate::remote::RemoteKind;
@@ -257,6 +258,46 @@ pub enum StoreError {
     Io(String),
 }
 
+/// Errors from the [`MemoryStore`].
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum MemoryError {
+    /// The requested note was not found.
+    #[error("memory not found")]
+    NotFound,
+    /// A note's frontmatter could not be parsed or validated.
+    #[error("memory frontmatter error: {0}")]
+    Frontmatter(String),
+    /// Underlying I/O error.
+    #[error("memory io failed: {0}")]
+    Io(String),
+    /// (De)serialisation of the index or another structured part failed.
+    #[error("memory serialization failed: {0}")]
+    Serialization(String),
+}
+
+/// Errors from an [`Embedder`] (LOT C, étage 2 vectoriel).
+///
+/// Best-effort by contract: a [`MemoryRecall`] that composes an embedder must
+/// **degrade**, never fail hard, on any of these — an unavailable engine or an
+/// unimplemented strategy maps to a fallback on the naïve recall (it must never
+/// surface as a hard recall error). See [`Embedder`] and the `VectorMemoryRecall`
+/// / `AdaptiveMemoryRecall` adapters.
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum EmbedderError {
+    /// The embedding engine is not installed / not reachable (e.g. a local ONNX
+    /// model file is missing, or a remote embedding server / API is unreachable).
+    #[error("embedder unavailable: {0}")]
+    Unavailable(String),
+    /// The requested strategy is not implemented yet (the concrete `localOnnx` /
+    /// `localServer` / `api` backends ship as documented stubs returning this —
+    /// never a panic). Real ONNX/HTTP integration is an explicit follow-up.
+    #[error("embedder strategy unsupported: {0}")]
+    Unsupported(String),
+    /// An I/O failure while producing embeddings.
+    #[error("embedder io failed: {0}")]
+    Io(String),
+}
+
 /// Errors from [`RemoteHost`].
 #[derive(Debug, Clone, PartialEq, Eq, Error)]
 pub enum RemoteError {
@@ -561,6 +602,130 @@ pub trait SkillStore: Send + Sync {
     ) -> Result<(), StoreError>;
 }
 
+/// CRUD for project [`Memory`] notes — the `.md` knowledge base under
+/// `.ideai/memory/` (LOT A, étage 1). Notes are the single source of truth; the
+/// aggregated `MEMORY.md` index is derived and kept in sync on every write.
+///
+/// `root` identifies the project whose `.ideai/memory/` to use; it is supplied
+/// **per call** (mirroring [`SkillStore`]) so a single store instance serves
+/// every open project.
+#[async_trait]
+pub trait MemoryStore: Send + Sync {
+    /// Lists all memory notes for `root`'s project.
+    ///
+    /// # Errors
+    /// [`MemoryError`] on failure (e.g. a malformed note's frontmatter).
+    async fn list(&self, root: &ProjectPath) -> Result<Vec<Memory>, MemoryError>;
+
+    /// Gets a memory note by slug.
+    ///
+    /// # Errors
+    /// [`MemoryError::NotFound`] if absent; [`MemoryError::Frontmatter`] if its
+    /// frontmatter is malformed.
+    async fn get(&self, root: &ProjectPath, slug: &MemorySlug) -> Result<Memory, MemoryError>;
+
+    /// Saves (creates or replaces by slug) a note: writes `<slug>.md` and upserts
+    /// its line in `MEMORY.md` idempotently.
+    ///
+    /// # Errors
+    /// [`MemoryError`] on failure.
+    async fn save(&self, root: &ProjectPath, memory: &Memory) -> Result<(), MemoryError>;
+
+    /// Deletes a note by slug, removing its line from `MEMORY.md`.
+    ///
+    /// # Errors
+    /// [`MemoryError::NotFound`] if absent.
+    async fn delete(&self, root: &ProjectPath, slug: &MemorySlug) -> Result<(), MemoryError>;
+
+    /// Reads the aggregated `MEMORY.md` index as structured entries (empty if the
+    /// index does not exist yet).
+    ///
+    /// # Errors
+    /// [`MemoryError`] on an I/O failure.
+    async fn read_index(&self, root: &ProjectPath) -> Result<Vec<MemoryIndexEntry>, MemoryError>;
+
+    /// Resolves the `[[slug]]` links emanating from `slug`'s note, **ignoring
+    /// broken links** (targets that do not resolve to an existing note).
+    ///
+    /// # Errors
+    /// [`MemoryError::NotFound`] if `slug` itself does not exist.
+    async fn resolve_links(
+        &self,
+        root: &ProjectPath,
+        slug: &MemorySlug,
+    ) -> Result<Vec<MemoryLink>, MemoryError>;
+}
+
+/// A recall request: the query text plus the token budget bounding the result
+/// (LOT B, étage 1). `text` is typically the agent's current context; the naïve
+/// adapter ignores it, but a semantic [`MemoryRecall`] (LOT C) ranks against it.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct MemoryQuery {
+    /// The recall query (often the agent's current working context).
+    pub text: String,
+    /// Approximate token budget the returned entries must fit within. A budget of
+    /// `0` yields an empty result.
+    pub token_budget: usize,
+}
+
+/// Adaptive recall of the most relevant subset of a project's memory index for a
+/// query, bounded by a token budget (LOT B, étage 1).
+///
+/// Contract (best-effort, never blocking):
+/// - an empty or absent memory yields an empty list, **never** an error;
+/// - a `token_budget` of `0` yields an empty list;
+/// - the naïve adapter ignores semantic relevance and returns the index entries
+///   in order, truncated to fit the budget.
+///
+/// **Liskov**: every implementation (`NaiveMemoryRecall`, the future
+/// `VectorMemoryRecall`) is substitutable — same emptiness/budget guarantees, only
+/// the relevance strategy differs.
+#[async_trait]
+pub trait MemoryRecall: Send + Sync {
+    /// Returns the entries most relevant to `query` for `root`'s project, capped
+    /// at `query.token_budget`.
+    ///
+    /// # Errors
+    /// [`MemoryError`] only on an unexpected I/O failure of the underlying store;
+    /// an empty or missing memory is **not** an error (returns an empty list).
+    async fn recall(
+        &self,
+        root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError>;
+}
+
+/// Produces embedding vectors for texts, driven by a declarative
+/// [`crate::profile::EmbedderProfile`] (façon §9 — adding an engine is *data*,
+/// not code: Open/Closed). The étage-2 vector recall (LOT C) composes this port
+/// to rank memory notes semantically.
+///
+/// Contract:
+/// - [`embed`](Self::embed) returns **one vector per input text**, in the same
+///   order, each of length [`dimension`](Self::dimension);
+/// - it is **best-effort from the caller's standpoint**: any failure is an
+///   [`EmbedderError`], on which a composing [`MemoryRecall`] degrades to the
+///   naïve recall — it must never bubble up as a hard recall error;
+/// - implementations are **substitutable** (Liskov): a deterministic test
+///   embedder and a real ONNX/HTTP one differ only in vector quality, not in the
+///   shape of their guarantees.
+#[async_trait]
+pub trait Embedder: Send + Sync {
+    /// Stable identifier of this embedder (e.g. `"local-onnx-minilm"`).
+    fn id(&self) -> &str;
+
+    /// Embeds each text into a `dimension()`-length vector, preserving order.
+    ///
+    /// # Errors
+    /// - [`EmbedderError::Unavailable`] if the engine is not installed/reachable,
+    /// - [`EmbedderError::Unsupported`] if the strategy is not implemented yet,
+    /// - [`EmbedderError::Io`] on an I/O failure.
+    async fn embed(&self, texts: &[String]) -> Result<Vec<Vec<f32>>, EmbedderError>;
+
+    /// The length of every vector produced by [`embed`](Self::embed).
+    fn dimension(&self) -> usize;
+}
+
 /// Persistence of the known-projects registry and the workspace.
 #[async_trait]
 pub trait ProjectStore: Send + Sync {

crates/domain/src/profile.rs

@@ -150,6 +150,107 @@ pub struct AgentProfile {
     pub session: Option<SessionStrategy>,
 }
 
+/// Embedding strategy of an [`EmbedderProfile`] (LOT C, étage 2 vectoriel).
+///
+/// Declarative, Open/Closed: a new engine family is a new variant *only* if it
+/// changes the adapter's dispatch; otherwise it is pure data on the profile
+/// (`model`, `endpoint`, …). The default product posture is [`None`](Self::None):
+/// no embedding ⇒ no heavy dependency, recall stays the naïve étage 1.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum EmbedderStrategy {
+    /// A local ONNX model run in-process (real integration is a follow-up).
+    LocalOnnx,
+    /// A local embedding server reached over HTTP (real integration is a follow-up).
+    LocalServer,
+    /// A remote embedding API (real integration is a follow-up).
+    Api,
+    /// No embedding engine: recall stays the dependency-free naïve étage 1.
+    None,
+}
+
+/// Declarative configuration for one embedding engine (LOT C, étage 2).
+///
+/// Stored in the global IDE store as `embedder.json`, mirroring `profiles.json`
+/// for [`AgentProfile`]s: adding an engine is **data, not code** (Open/Closed).
+///
+/// Invariants:
+/// - `id` and `name` non-empty,
+/// - `dimension` is non-zero (an embedder always produces fixed-length vectors).
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct EmbedderProfile {
+    /// Stable identifier (e.g. `"local-onnx-minilm"`).
+    pub id: String,
+    /// Display name.
+    pub name: String,
+    /// Embedding strategy driving which concrete adapter is used.
+    pub strategy: EmbedderStrategy,
+    /// Model identifier (e.g. an ONNX model name), when the strategy needs one.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub model: Option<String>,
+    /// Endpoint URL for a server/API strategy.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub endpoint: Option<String>,
+    /// Name of the environment variable carrying the API key (never the key
+    /// itself), for an `api` strategy.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub api_key_env: Option<String>,
+    /// Length of the vectors this engine produces.
+    pub dimension: usize,
+}
+
+impl EmbedderProfile {
+    /// Builds a validated embedder profile.
+    ///
+    /// # Errors
+    /// - [`DomainError::EmptyField`] if `id` or `name` is empty,
+    /// - [`DomainError::EmptyField`] (`"embedder.dimension"`) if `dimension` is `0`.
+    pub fn new(
+        id: impl Into<String>,
+        name: impl Into<String>,
+        strategy: EmbedderStrategy,
+        model: Option<String>,
+        endpoint: Option<String>,
+        api_key_env: Option<String>,
+        dimension: usize,
+    ) -> Result<Self, DomainError> {
+        let id = id.into();
+        let name = name.into();
+        crate::validation::non_empty(&id, "embedder.id")?;
+        crate::validation::non_empty(&name, "embedder.name")?;
+        if dimension == 0 {
+            return Err(DomainError::EmptyField {
+                field: "embedder.dimension",
+            });
+        }
+        Ok(Self {
+            id,
+            name,
+            strategy,
+            model,
+            endpoint,
+            api_key_env,
+            dimension,
+        })
+    }
+
+    /// A dependency-free default profile: strategy [`EmbedderStrategy::None`].
+    /// Recall stays the naïve étage 1 — nothing is imposed.
+    #[must_use]
+    pub fn none() -> Self {
+        Self {
+            id: "none".to_owned(),
+            name: "None".to_owned(),
+            strategy: EmbedderStrategy::None,
+            model: None,
+            endpoint: None,
+            api_key_env: None,
+            dimension: 1,
+        }
+    }
+}
+
 impl AgentProfile {
     /// Builds a validated profile.
     ///

crates/domain/tests/embedder_profile.rs

@@ -0,0 +1,183 @@
+//! Tests for the declarative [`EmbedderProfile`] / [`EmbedderStrategy`] (LOT C,
+//! étage 2 vectoriel): serde camelCase round-trip, the validated `new`
+//! constructor, and the dependency-free `none()` default.
+
+use domain::{DomainError, EmbedderProfile, EmbedderStrategy};
+
+fn roundtrip<T>(value: &T) -> T
+where
+    T: serde::Serialize + serde::de::DeserializeOwned + PartialEq + std::fmt::Debug,
+{
+    let json = serde_json::to_string(value).expect("serialize");
+    let back: T = serde_json::from_str(&json).expect("deserialize");
+    assert_eq!(&back, value, "round-trip mismatch via {json}");
+    back
+}
+
+// ---------------------------------------------------------------------------
+// EmbedderStrategy: camelCase wire form (`localOnnx` / `localServer` / `api` /
+// `none`).
+// ---------------------------------------------------------------------------
+
+#[test]
+fn strategy_serializes_camel_case() {
+    assert_eq!(
+        serde_json::to_string(&EmbedderStrategy::LocalOnnx).unwrap(),
+        "\"localOnnx\""
+    );
+    assert_eq!(
+        serde_json::to_string(&EmbedderStrategy::LocalServer).unwrap(),
+        "\"localServer\""
+    );
+    assert_eq!(
+        serde_json::to_string(&EmbedderStrategy::Api).unwrap(),
+        "\"api\""
+    );
+    assert_eq!(
+        serde_json::to_string(&EmbedderStrategy::None).unwrap(),
+        "\"none\""
+    );
+}
+
+#[test]
+fn strategy_deserializes_camel_case() {
+    assert_eq!(
+        serde_json::from_str::<EmbedderStrategy>("\"localOnnx\"").unwrap(),
+        EmbedderStrategy::LocalOnnx
+    );
+    assert_eq!(
+        serde_json::from_str::<EmbedderStrategy>("\"localServer\"").unwrap(),
+        EmbedderStrategy::LocalServer
+    );
+    assert_eq!(
+        serde_json::from_str::<EmbedderStrategy>("\"api\"").unwrap(),
+        EmbedderStrategy::Api
+    );
+    assert_eq!(
+        serde_json::from_str::<EmbedderStrategy>("\"none\"").unwrap(),
+        EmbedderStrategy::None
+    );
+}
+
+#[test]
+fn strategy_roundtrips() {
+    for s in [
+        EmbedderStrategy::LocalOnnx,
+        EmbedderStrategy::LocalServer,
+        EmbedderStrategy::Api,
+        EmbedderStrategy::None,
+    ] {
+        roundtrip(&s);
+    }
+}
+
+// ---------------------------------------------------------------------------
+// EmbedderProfile: camelCase fields and optional-field skipping.
+// ---------------------------------------------------------------------------
+
+#[test]
+fn profile_roundtrips_with_all_fields() {
+    let p = EmbedderProfile::new(
+        "local-onnx-minilm",
+        "Local MiniLM",
+        EmbedderStrategy::LocalOnnx,
+        Some("all-MiniLM-L6-v2".to_owned()),
+        Some("http://localhost:1234".to_owned()),
+        Some("OPENAI_API_KEY".to_owned()),
+        384,
+    )
+    .unwrap();
+    let back = roundtrip(&p);
+    assert_eq!(back.dimension, 384);
+    assert_eq!(back.strategy, EmbedderStrategy::LocalOnnx);
+}
+
+#[test]
+fn profile_uses_camel_case_keys_and_skips_none_options() {
+    let p = EmbedderProfile::new(
+        "id-1",
+        "Name",
+        EmbedderStrategy::Api,
+        None,
+        Some("https://api.example/embed".to_owned()),
+        Some("MY_KEY".to_owned()),
+        16,
+    )
+    .unwrap();
+    let json = serde_json::to_string(&p).unwrap();
+    assert!(json.contains("\"apiKeyEnv\":\"MY_KEY\""), "camelCase apiKeyEnv: {json}");
+    assert!(json.contains("\"strategy\":\"api\""), "camelCase strategy: {json}");
+    // `model` is None ⇒ skipped from the wire form.
+    assert!(!json.contains("\"model\""), "None model must be skipped: {json}");
+}
+
+#[test]
+fn profile_deserializes_from_camel_case_document() {
+    let json = r#"{
+        "id": "srv",
+        "name": "Server",
+        "strategy": "localServer",
+        "endpoint": "http://127.0.0.1:9000",
+        "dimension": 512
+    }"#;
+    let p: EmbedderProfile = serde_json::from_str(json).unwrap();
+    assert_eq!(p.id, "srv");
+    assert_eq!(p.strategy, EmbedderStrategy::LocalServer);
+    assert_eq!(p.endpoint.as_deref(), Some("http://127.0.0.1:9000"));
+    assert_eq!(p.dimension, 512);
+    assert!(p.model.is_none());
+    assert!(p.api_key_env.is_none());
+}
+
+// ---------------------------------------------------------------------------
+// none(): the dependency-free default.
+// ---------------------------------------------------------------------------
+
+#[test]
+fn none_profile_has_none_strategy() {
+    let p = EmbedderProfile::none();
+    assert_eq!(p.strategy, EmbedderStrategy::None);
+    assert_eq!(p.id, "none");
+    assert!(p.dimension > 0, "even the none profile keeps a non-zero dimension");
+    // And it round-trips like any other profile.
+    roundtrip(&p);
+}
+
+// ---------------------------------------------------------------------------
+// new(): validation.
+// ---------------------------------------------------------------------------
+
+#[test]
+fn new_rejects_empty_id() {
+    assert!(matches!(
+        EmbedderProfile::new("", "Name", EmbedderStrategy::None, None, None, None, 8),
+        Err(DomainError::EmptyField { field: "embedder.id" })
+    ));
+}
+
+#[test]
+fn new_rejects_empty_name() {
+    assert!(matches!(
+        EmbedderProfile::new("id", "", EmbedderStrategy::None, None, None, None, 8),
+        Err(DomainError::EmptyField {
+            field: "embedder.name"
+        })
+    ));
+}
+
+#[test]
+fn new_rejects_zero_dimension() {
+    assert!(matches!(
+        EmbedderProfile::new("id", "Name", EmbedderStrategy::None, None, None, None, 0),
+        Err(DomainError::EmptyField {
+            field: "embedder.dimension"
+        })
+    ));
+}
+
+#[test]
+fn new_accepts_valid_minimal_profile() {
+    let p = EmbedderProfile::new("id", "Name", EmbedderStrategy::None, None, None, None, 1).unwrap();
+    assert_eq!(p.dimension, 1);
+    assert_eq!(p.strategy, EmbedderStrategy::None);
+}

crates/domain/tests/memory.rs

@@ -0,0 +1,187 @@
+//! Domain tests for the [`Memory`] entity and its value objects (LOT A, étage 1):
+//! [`MemorySlug`] validation, `[[slug]]` link scanning, frontmatter serde
+//! round-trip, and the derived index entry.
+
+use domain::{
+    DomainError, MarkdownDoc, Memory, MemoryFrontmatter, MemorySlug, MemoryType,
+};
+
+fn fm(slug: &str, description: &str, ty: MemoryType) -> MemoryFrontmatter {
+    MemoryFrontmatter {
+        name: MemorySlug::new(slug).unwrap(),
+        description: description.to_string(),
+        r#type: ty,
+    }
+}
+
+fn note(slug: &str, body: &str) -> Memory {
+    Memory::new(
+        fm(slug, "a hook", MemoryType::Project),
+        MarkdownDoc::new(body),
+    )
+    .unwrap()
+}
+
+// ---------------------------------------------------------------------------
+// MemorySlug
+// ---------------------------------------------------------------------------
+
+#[test]
+fn slug_accepts_kebab_case() {
+    assert_eq!(
+        MemorySlug::new("my-note-42").unwrap().as_str(),
+        "my-note-42"
+    );
+    assert!(MemorySlug::new("abc").is_ok());
+    assert!(MemorySlug::new("a-b-c-1-2-3").is_ok());
+}
+
+#[test]
+fn slug_rejects_uppercase() {
+    assert!(matches!(
+        MemorySlug::new("MyNote").unwrap_err(),
+        DomainError::InvalidSlug { .. }
+    ));
+}
+
+#[test]
+fn slug_rejects_spaces() {
+    assert!(matches!(
+        MemorySlug::new("my note").unwrap_err(),
+        DomainError::InvalidSlug { .. }
+    ));
+}
+
+#[test]
+fn slug_rejects_dot_and_traversal() {
+    assert!(matches!(
+        MemorySlug::new("..").unwrap_err(),
+        DomainError::InvalidSlug { .. }
+    ));
+    assert!(matches!(
+        MemorySlug::new("a.b").unwrap_err(),
+        DomainError::InvalidSlug { .. }
+    ));
+}
+
+#[test]
+fn slug_rejects_empty() {
+    assert!(matches!(
+        MemorySlug::new("").unwrap_err(),
+        DomainError::InvalidSlug { .. }
+    ));
+}
+
+#[test]
+fn slug_rejects_underscore_and_slash() {
+    assert!(MemorySlug::new("a_b").is_err());
+    assert!(MemorySlug::new("a/b").is_err());
+}
+
+// ---------------------------------------------------------------------------
+// Memory invariants
+// ---------------------------------------------------------------------------
+
+#[test]
+fn memory_rejects_empty_description() {
+    let r = Memory::new(
+        fm("ok-slug", "", MemoryType::User),
+        MarkdownDoc::new("body"),
+    );
+    assert!(matches!(r.unwrap_err(), DomainError::EmptyField { .. }));
+}
+
+#[test]
+fn memory_rejects_empty_body() {
+    let r = Memory::new(fm("ok-slug", "hook", MemoryType::User), MarkdownDoc::new(""));
+    assert!(matches!(r.unwrap_err(), DomainError::EmptyField { .. }));
+}
+
+// ---------------------------------------------------------------------------
+// outgoing_links
+// ---------------------------------------------------------------------------
+
+#[test]
+fn outgoing_links_none() {
+    assert!(note("n", "plain body, no links").outgoing_links().is_empty());
+}
+
+#[test]
+fn outgoing_links_multiple() {
+    let m = note("n", "see [[alpha]] and also [[beta-2]] here");
+    let targets: Vec<_> = m
+        .outgoing_links()
+        .into_iter()
+        .map(|l| l.target.as_str().to_string())
+        .collect();
+    assert_eq!(targets, vec!["alpha".to_string(), "beta-2".to_string()]);
+}
+
+#[test]
+fn outgoing_links_preserves_duplicates() {
+    let m = note("n", "[[alpha]] then again [[alpha]]");
+    assert_eq!(m.outgoing_links().len(), 2);
+}
+
+#[test]
+fn outgoing_links_skips_invalid_targets() {
+    // `[[Not Valid]]` is not a kebab-case slug -> skipped.
+    let m = note("n", "[[Not Valid]] but [[good-one]]");
+    let targets: Vec<_> = m
+        .outgoing_links()
+        .into_iter()
+        .map(|l| l.target.as_str().to_string())
+        .collect();
+    assert_eq!(targets, vec!["good-one".to_string()]);
+}
+
+#[test]
+fn outgoing_links_ignores_unterminated() {
+    let m = note("n", "dangling [[oops without close");
+    assert!(m.outgoing_links().is_empty());
+}
+
+// ---------------------------------------------------------------------------
+// index_entry
+// ---------------------------------------------------------------------------
+
+#[test]
+fn index_entry_carries_slug_hook_and_type() {
+    let m = Memory::new(
+        fm("topic-x", "a useful hook", MemoryType::Feedback),
+        MarkdownDoc::new("body"),
+    )
+    .unwrap();
+    let e = m.index_entry();
+    assert_eq!(e.slug.as_str(), "topic-x");
+    assert_eq!(e.hook, "a useful hook");
+    assert_eq!(e.title, "topic-x");
+    assert_eq!(e.r#type, MemoryType::Feedback);
+}
+
+// ---------------------------------------------------------------------------
+// Frontmatter serde round-trip (the `type` field name + camelCase variants).
+// ---------------------------------------------------------------------------
+
+#[test]
+fn frontmatter_serde_roundtrip() {
+    let original = fm("round-trip", "desc", MemoryType::Reference);
+    let json = serde_json::to_string(&original).unwrap();
+    // `type` field name (not `kind`), camelCase enum value.
+    assert!(json.contains("\"type\":\"reference\""));
+    assert!(json.contains("\"name\":\"round-trip\""));
+    let back: MemoryFrontmatter = serde_json::from_str(&json).unwrap();
+    assert_eq!(back, original);
+}
+
+#[test]
+fn memory_type_serde_is_camel_case() {
+    assert_eq!(
+        serde_json::to_string(&MemoryType::User).unwrap(),
+        "\"user\""
+    );
+    assert_eq!(
+        serde_json::to_string(&MemoryType::Project).unwrap(),
+        "\"project\""
+    );
+}

crates/infrastructure/src/lib.rs

@@ -40,5 +40,8 @@ pub use pty::PortablePtyAdapter;
 pub use remote::{remote_host, LocalHost};
 pub use runtime::CliAgentRuntime;
 pub use store::{
-    FsProfileStore, FsProjectStore, FsSkillStore, FsTemplateStore, IdeaiContextStore,
+    embedder_from_profile, index_token_size, should_use_vector, AdaptiveMemoryRecall,
+    FsEmbedderProfileStore, FsMemoryStore, FsProfileStore, FsProjectStore, FsSkillStore,
+    FsTemplateStore, HashEmbedder, IdeaiContextStore, NaiveMemoryRecall, StubEmbedder,
+    VectorMemoryRecall,
 };

crates/infrastructure/src/store/embedder.rs

@@ -0,0 +1,173 @@
+//! [`Embedder`] adapters (LOT C, étage 2 vectoriel — §14.5.3).
+//!
+//! The étage-2 semantic recall is driven by a declarative
+//! [`EmbedderProfile`]; this module turns such a profile into a concrete
+//! [`Embedder`] via [`embedder_from_profile`].
+//!
+//! ## Zero heavy dependency by design
+//!
+//! IdeA's founding posture is **default `none`, nothing imposed, zero
+//! dependency** (ARCHITECTURE §14.5.3). The concrete engines therefore ship as
+//! **documented stubs**:
+//!
+//! - [`EmbedderStrategy::LocalOnnx`] / [`EmbedderStrategy::LocalServer`] /
+//!   [`EmbedderStrategy::Api`] map to [`StubEmbedder`], which returns a clean
+//!   [`EmbedderError::Unsupported`] (never a panic) — the real ONNX/HTTP
+//!   integration is an explicit follow-up that would add the heavy crate behind a
+//!   feature, here and only here;
+//! - [`EmbedderStrategy::None`] yields no embedder (`None`): recall stays the
+//!   dependency-free naïve étage 1.
+//!
+//! [`HashEmbedder`] is a small **deterministic, dependency-free** embedder used to
+//! exercise the whole vector pipeline (it is not a stub: it produces stable,
+//! repeatable vectors from a hashing bag-of-words, good enough for tests and for a
+//! trivial offline fallback).
+
+use async_trait::async_trait;
+
+use domain::ports::{Embedder, EmbedderError};
+use domain::profile::{EmbedderProfile, EmbedderStrategy};
+
+/// Builds the concrete [`Embedder`] for a profile, or `None` when the strategy is
+/// [`EmbedderStrategy::None`] (recall stays naïve).
+///
+/// The concrete engines are stubs ([`StubEmbedder`]) until their real ONNX/HTTP
+/// integration lands; they fail cleanly with [`EmbedderError::Unsupported`] rather
+/// than panic, so a composing recall degrades to naïve.
+#[must_use]
+pub fn embedder_from_profile(profile: &EmbedderProfile) -> Option<Box<dyn Embedder>> {
+    match profile.strategy {
+        EmbedderStrategy::None => None,
+        EmbedderStrategy::LocalOnnx => Some(Box::new(StubEmbedder::new(
+            profile.id.clone(),
+            profile.dimension,
+            "localOnnx",
+        ))),
+        EmbedderStrategy::LocalServer => Some(Box::new(StubEmbedder::new(
+            profile.id.clone(),
+            profile.dimension,
+            "localServer",
+        ))),
+        EmbedderStrategy::Api => Some(Box::new(StubEmbedder::new(
+            profile.id.clone(),
+            profile.dimension,
+            "api",
+        ))),
+    }
+}
+
+/// A placeholder [`Embedder`] for a not-yet-implemented concrete strategy.
+///
+/// Every [`embed`](Embedder::embed) call returns [`EmbedderError::Unsupported`]
+/// (never a panic), naming the strategy. It exists so the wiring, profiles, and
+/// adapters are all in place and testable today; swapping in the real engine is a
+/// localised follow-up.
+pub struct StubEmbedder {
+    id: String,
+    dimension: usize,
+    strategy: &'static str,
+}
+
+impl StubEmbedder {
+    /// Builds a stub for `strategy` advertising `dimension`.
+    #[must_use]
+    pub fn new(id: impl Into<String>, dimension: usize, strategy: &'static str) -> Self {
+        Self {
+            id: id.into(),
+            dimension,
+            strategy,
+        }
+    }
+}
+
+#[async_trait]
+impl Embedder for StubEmbedder {
+    fn id(&self) -> &str {
+        &self.id
+    }
+
+    async fn embed(&self, _texts: &[String]) -> Result<Vec<Vec<f32>>, EmbedderError> {
+        Err(EmbedderError::Unsupported(format!(
+            "embedder strategy `{}` is not implemented yet (follow-up: real ONNX/HTTP backend)",
+            self.strategy
+        )))
+    }
+
+    fn dimension(&self) -> usize {
+        self.dimension
+    }
+}
+
+/// A deterministic, dependency-free [`Embedder`] backed by a hashing
+/// bag-of-words. Pure std (FNV-1a hashing of whitespace tokens into `dimension`
+/// buckets, then L2-normalised). Stable across runs and platforms.
+///
+/// It is **not** a stub: it lets the étage-2 pipeline run end-to-end with no heavy
+/// dependency. Vector quality is crude (lexical overlap only), but the
+/// [`Embedder`] contract is fully honoured, so it is a valid offline embedder and
+/// the substrate for deterministic tests of [`crate::store::VectorMemoryRecall`].
+#[derive(Clone)]
+pub struct HashEmbedder {
+    id: String,
+    dimension: usize,
+}
+
+impl HashEmbedder {
+    /// Builds a hashing embedder producing `dimension`-length vectors.
+    ///
+    /// # Panics
+    /// Panics if `dimension` is `0` (an embedder must produce fixed-length
+    /// non-empty vectors).
+    #[must_use]
+    pub fn new(id: impl Into<String>, dimension: usize) -> Self {
+        assert!(dimension > 0, "HashEmbedder dimension must be non-zero");
+        Self {
+            id: id.into(),
+            dimension,
+        }
+    }
+
+    /// Embeds one text into an L2-normalised `dimension`-length vector.
+    fn embed_one(&self, text: &str) -> Vec<f32> {
+        let mut v = vec![0f32; self.dimension];
+        for token in text.split_whitespace() {
+            let lower = token.to_ascii_lowercase();
+            let bucket = (fnv1a(lower.as_bytes()) as usize) % self.dimension;
+            v[bucket] += 1.0;
+        }
+        let norm = v.iter().map(|x| x * x).sum::<f32>().sqrt();
+        if norm > 0.0 {
+            for x in &mut v {
+                *x /= norm;
+            }
+        }
+        v
+    }
+}
+
+#[async_trait]
+impl Embedder for HashEmbedder {
+    fn id(&self) -> &str {
+        &self.id
+    }
+
+    async fn embed(&self, texts: &[String]) -> Result<Vec<Vec<f32>>, EmbedderError> {
+        Ok(texts.iter().map(|t| self.embed_one(t)).collect())
+    }
+
+    fn dimension(&self) -> usize {
+        self.dimension
+    }
+}
+
+/// FNV-1a 64-bit hash of a byte slice (deterministic, dependency-free).
+fn fnv1a(bytes: &[u8]) -> u64 {
+    const OFFSET: u64 = 0xcbf2_9ce4_8422_2325;
+    const PRIME: u64 = 0x0000_0100_0000_01b3;
+    let mut hash = OFFSET;
+    for &b in bytes {
+        hash ^= u64::from(b);
+        hash = hash.wrapping_mul(PRIME);
+    }
+    hash
+}

crates/infrastructure/src/store/memory.rs

@@ -0,0 +1,492 @@
+//! [`FsMemoryStore`] — file implementation of the [`MemoryStore`] port
+//! (LOT A, étage 1).
+//!
+//! Memory notes are the project's persistent, model-agnostic knowledge base. Each
+//! note is a single Markdown file with a YAML frontmatter header, stored under the
+//! project's `.ideai/memory/`:
+//!
+//! ```text
+//! <project_root>/.ideai/memory/
+//! ├── MEMORY.md        # aggregated index: one `- [Title](slug.md) — hook` line per note
+//! └── <slug>.md        # a note: YAML frontmatter + Markdown body
+//! ```
+//!
+//! A note file looks like:
+//!
+//! ```text
+//! ---
+//! name: my-note
+//! description: A one-line hook
+//! metadata:
+//!   type: project
+//! ---
+//! # Body
+//! ...
+//! ```
+//!
+//! The `.md` files are the **single source of truth**; `MEMORY.md` is derived and
+//! kept in sync on every [`save`](MemoryStore::save)/[`delete`](MemoryStore::delete)
+//! (idempotent upsert / removal of the note's line). All I/O goes through the
+//! [`FileSystem`] port, so the adapter is location-neutral (SSH/WSL work unchanged)
+//! and Tauri-agnostic.
+//!
+//! Like the sibling stores, [`delete`](MemoryStore::delete) drops the note's line
+//! from `MEMORY.md` and leaves the orphaned `<slug>.md` on disk (the [`FileSystem`]
+//! port exposes no remove); since listing is index-driven, the note is effectively
+//! gone.
+
+use std::sync::Arc;
+
+use async_trait::async_trait;
+
+use domain::markdown::MarkdownDoc;
+use domain::memory::{
+    Memory, MemoryFrontmatter, MemoryIndexEntry, MemoryLink, MemorySlug, MemoryType,
+};
+use domain::ports::{
+    FileSystem, FsError, MemoryError, MemoryQuery, MemoryRecall, MemoryStore, RemotePath,
+};
+use domain::project::ProjectPath;
+
+/// The `.ideai/` directory name inside a project root.
+const IDEAI_DIR: &str = ".ideai";
+
+/// Sub-path of the memory store inside `.ideai/`.
+const MEMORY_DIR: &str = "memory";
+
+/// Aggregated index file name inside the memory dir.
+const INDEX_FILE: &str = "MEMORY.md";
+
+/// First line of the aggregated index.
+const INDEX_HEADER: &str = "# Memory Index";
+
+/// File-backed [`MemoryStore`], composing a [`FileSystem`] port. The project root
+/// is supplied **per call**, so a single instance serves every open project
+/// (mirroring [`crate::store::FsSkillStore`]).
+#[derive(Clone)]
+pub struct FsMemoryStore {
+    fs: Arc<dyn FileSystem>,
+}
+
+impl FsMemoryStore {
+    /// Builds the store from an injected [`FileSystem`]. Directories are created
+    /// on first write.
+    #[must_use]
+    pub fn new(fs: Arc<dyn FileSystem>) -> Self {
+        Self { fs }
+    }
+
+    /// `<root>/.ideai/memory`.
+    fn dir(&self, root: &ProjectPath) -> String {
+        let base = root.as_str().trim_end_matches(['/', '\\']);
+        format!("{base}/{IDEAI_DIR}/{MEMORY_DIR}")
+    }
+
+    /// `<memory-dir>/<slug>.md`.
+    fn md_path(&self, root: &ProjectPath, slug: &MemorySlug) -> RemotePath {
+        RemotePath::new(format!("{}/{}.md", self.dir(root), slug.as_str()))
+    }
+
+    /// `<memory-dir>/MEMORY.md`.
+    fn index_path(&self, root: &ProjectPath) -> RemotePath {
+        RemotePath::new(format!("{}/{INDEX_FILE}", self.dir(root)))
+    }
+
+    /// Reads and parses a note by slug.
+    async fn load(&self, root: &ProjectPath, slug: &MemorySlug) -> Result<Memory, MemoryError> {
+        let bytes = self
+            .fs
+            .read(&self.md_path(root, slug))
+            .await
+            .map_err(|e| match e {
+                FsError::NotFound(_) => MemoryError::NotFound,
+                other => MemoryError::Io(other.to_string()),
+            })?;
+        let text = String::from_utf8(bytes).map_err(|e| MemoryError::Io(e.to_string()))?;
+        parse_note(&text)
+    }
+
+    /// Reads the raw `MEMORY.md` text, or `None` if it does not exist yet.
+    async fn read_index_text(&self, root: &ProjectPath) -> Result<Option<String>, MemoryError> {
+        match self.fs.read(&self.index_path(root)).await {
+            Ok(bytes) => String::from_utf8(bytes)
+                .map(Some)
+                .map_err(|e| MemoryError::Io(e.to_string())),
+            Err(FsError::NotFound(_)) => Ok(None),
+            Err(e) => Err(MemoryError::Io(e.to_string())),
+        }
+    }
+
+    /// Rewrites `MEMORY.md` from the given entries, ensuring the dir exists.
+    async fn write_index(
+        &self,
+        root: &ProjectPath,
+        entries: &[MemoryIndexEntry],
+    ) -> Result<(), MemoryError> {
+        self.fs
+            .create_dir_all(&RemotePath::new(self.dir(root)))
+            .await
+            .map_err(|e| MemoryError::Io(e.to_string()))?;
+        let text = render_index(entries);
+        self.fs
+            .write(&self.index_path(root), text.as_bytes())
+            .await
+            .map_err(|e| MemoryError::Io(e.to_string()))
+    }
+
+    /// Lists the slugs known to the index (index-driven listing).
+    async fn index_slugs(&self, root: &ProjectPath) -> Result<Vec<MemorySlug>, MemoryError> {
+        Ok(self
+            .read_index(root)
+            .await?
+            .into_iter()
+            .map(|e| e.slug)
+            .collect())
+    }
+}
+
+#[async_trait]
+impl MemoryStore for FsMemoryStore {
+    async fn list(&self, root: &ProjectPath) -> Result<Vec<Memory>, MemoryError> {
+        let slugs = self.index_slugs(root).await?;
+        let mut out = Vec::with_capacity(slugs.len());
+        for slug in &slugs {
+            out.push(self.load(root, slug).await?);
+        }
+        Ok(out)
+    }
+
+    async fn get(&self, root: &ProjectPath, slug: &MemorySlug) -> Result<Memory, MemoryError> {
+        self.load(root, slug).await
+    }
+
+    async fn save(&self, root: &ProjectPath, memory: &Memory) -> Result<(), MemoryError> {
+        // (1) Write the note file.
+        self.fs
+            .create_dir_all(&RemotePath::new(self.dir(root)))
+            .await
+            .map_err(|e| MemoryError::Io(e.to_string()))?;
+        let text = render_note(memory);
+        self.fs
+            .write(&self.md_path(root, memory.slug()), text.as_bytes())
+            .await
+            .map_err(|e| MemoryError::Io(e.to_string()))?;
+
+        // (2) Upsert the index line idempotently (same slug => one line).
+        let mut entries = self.read_index(root).await?;
+        let row = memory.index_entry();
+        if let Some(slot) = entries.iter_mut().find(|e| e.slug == row.slug) {
+            *slot = row;
+        } else {
+            entries.push(row);
+        }
+        self.write_index(root, &entries).await
+    }
+
+    async fn delete(&self, root: &ProjectPath, slug: &MemorySlug) -> Result<(), MemoryError> {
+        let mut entries = self.read_index(root).await?;
+        let before = entries.len();
+        entries.retain(|e| &e.slug != slug);
+        if entries.len() == before {
+            return Err(MemoryError::NotFound);
+        }
+        // The orphaned `<slug>.md` is left on disk (no FileSystem delete); the
+        // index no longer references it, so it is effectively gone.
+        self.write_index(root, &entries).await
+    }
+
+    async fn read_index(&self, root: &ProjectPath) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        match self.read_index_text(root).await? {
+            Some(text) => Ok(parse_index(&text)),
+            None => Ok(Vec::new()),
+        }
+    }
+
+    async fn resolve_links(
+        &self,
+        root: &ProjectPath,
+        slug: &MemorySlug,
+    ) -> Result<Vec<MemoryLink>, MemoryError> {
+        let memory = self.load(root, slug).await?;
+        let known = self.index_slugs(root).await?;
+        // Keep only links whose target resolves to a known note (ignore broken).
+        Ok(memory
+            .outgoing_links()
+            .into_iter()
+            .filter(|link| known.contains(&link.target))
+            .collect())
+    }
+}
+
+// ---------------------------------------------------------------------------
+// NaiveMemoryRecall — the default, dependency-free MemoryRecall (LOT B).
+// ---------------------------------------------------------------------------
+
+/// Heuristic divisor turning a character count into an approximate token count
+/// (~4 characters per token, the usual rule of thumb). Shared by every
+/// [`MemoryRecall`] adapter so the budget semantics stay identical (DRY).
+pub(crate) const CHARS_PER_TOKEN: usize = 4;
+
+/// Approximate token cost of an index entry's textual payload — the single
+/// budget-cost function shared by every [`MemoryRecall`] adapter (naïve, vector,
+/// adaptive), so truncation semantics are identical across them (Liskov / DRY).
+pub(crate) fn entry_cost(entry: &MemoryIndexEntry) -> usize {
+    let chars = entry.title.len() + entry.hook.len();
+    chars.div_ceil(CHARS_PER_TOKEN)
+}
+
+/// Greedily takes entries in the given order while their accumulated
+/// [`entry_cost`] stays within `budget`; stops at the first entry that would
+/// exceed it (and drops every entry after). A `budget` of `0` yields an empty
+/// vec. This is the shared truncation used by every recall adapter.
+pub(crate) fn truncate_to_budget(
+    entries: impl IntoIterator<Item = MemoryIndexEntry>,
+    budget: usize,
+) -> Vec<MemoryIndexEntry> {
+    if budget == 0 {
+        return Vec::new();
+    }
+    let mut spent = 0usize;
+    let mut out = Vec::new();
+    for entry in entries {
+        let cost = entry_cost(&entry);
+        if spent + cost > budget {
+            break;
+        }
+        spent += cost;
+        out.push(entry);
+    }
+    out
+}
+
+/// Total approximate token cost of an index — a **pure** function of the entries,
+/// used by [`crate::store::AdaptiveMemoryRecall`] to decide naïve vs. vector
+/// recall without any I/O.
+#[must_use]
+pub fn index_token_size(entries: &[MemoryIndexEntry]) -> usize {
+    entries.iter().map(entry_cost).sum()
+}
+
+/// The default [`MemoryRecall`]: dependency-free, ignores semantic relevance.
+///
+/// It composes an [`Arc<dyn MemoryStore>`], reads the aggregated index via
+/// [`MemoryStore::read_index`], and returns the entries **in index order**,
+/// truncated to fit the query's token budget. It is the baseline against which a
+/// future `VectorMemoryRecall` (LOT C) is substitutable.
+///
+/// ## Budget semantics
+/// `token_budget` is an *approximate* budget. Each entry's cost is estimated as
+/// `ceil((title.len() + hook.len()) / 4)` tokens (≈ 4 chars/token, counting only
+/// the index line's textual payload). Entries are taken in order, accumulating
+/// their cost; the first entry whose inclusion would exceed the budget — and every
+/// entry after it — is dropped. A budget of `0` therefore yields an empty list;
+/// an empty or missing memory yields an empty list without error.
+#[derive(Clone)]
+pub struct NaiveMemoryRecall {
+    store: Arc<dyn MemoryStore>,
+}
+
+impl NaiveMemoryRecall {
+    /// Builds the recall adapter from a composed [`MemoryStore`].
+    #[must_use]
+    pub fn new(store: Arc<dyn MemoryStore>) -> Self {
+        Self { store }
+    }
+}
+
+#[async_trait]
+impl MemoryRecall for NaiveMemoryRecall {
+    async fn recall(
+        &self,
+        root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        // Budget-0 short-circuits before any I/O: a zero budget can hold no entry,
+        // so there is nothing to read (homogeneous with every recall adapter).
+        if query.token_budget == 0 {
+            return Ok(Vec::new());
+        }
+        let entries = self.store.read_index(root).await?;
+        Ok(truncate_to_budget(entries, query.token_budget))
+    }
+}
+
+// ---------------------------------------------------------------------------
+// On-disk format: YAML frontmatter + body, and the MEMORY.md index.
+//
+// We hand-roll a tiny, well-scoped YAML reader/writer for exactly the frontmatter
+// shape we own (`name`, `description`, `metadata.type`). This keeps the crate free
+// of a YAML dependency for a fixed, simple schema; any deviation surfaces as a
+// `MemoryError::Frontmatter`.
+// ---------------------------------------------------------------------------
+
+/// Renders a note to its on-disk `---`-fenced frontmatter + body form.
+fn render_note(memory: &Memory) -> String {
+    let fm = &memory.frontmatter;
+    format!(
+        "---\nname: {}\ndescription: {}\nmetadata:\n  type: {}\n---\n{}",
+        fm.name.as_str(),
+        fm.description,
+        type_to_str(fm.r#type),
+        memory.body.as_str(),
+    )
+}
+
+/// Parses a note from its on-disk form.
+fn parse_note(text: &str) -> Result<Memory, MemoryError> {
+    let rest = text
+        .strip_prefix("---\n")
+        .or_else(|| text.strip_prefix("---\r\n"))
+        .ok_or_else(|| MemoryError::Frontmatter("missing opening `---` fence".to_string()))?;
+
+    // Find the closing `---` fence at the start of a line.
+    let (fm_block, body) = split_frontmatter(rest)
+        .ok_or_else(|| MemoryError::Frontmatter("missing closing `---` fence".to_string()))?;
+
+    let frontmatter = parse_frontmatter(fm_block)?;
+    Memory::new(frontmatter, MarkdownDoc::new(body))
+        .map_err(|e| MemoryError::Frontmatter(e.to_string()))
+}
+
+/// Splits the post-opening-fence text into `(frontmatter_block, body)` at the
+/// closing `---` line. Returns `None` if no closing fence is present.
+fn split_frontmatter(rest: &str) -> Option<(&str, &str)> {
+    let mut offset = 0;
+    for line in rest.split_inclusive('\n') {
+        let trimmed = line.trim_end_matches(['\n', '\r']);
+        if trimmed == "---" {
+            let fm = &rest[..offset];
+            let body = &rest[offset + line.len()..];
+            return Some((fm, body));
+        }
+        offset += line.len();
+    }
+    None
+}
+
+/// Parses the frontmatter key/values into a validated [`MemoryFrontmatter`].
+fn parse_frontmatter(block: &str) -> Result<MemoryFrontmatter, MemoryError> {
+    let err = |reason: &str| MemoryError::Frontmatter(reason.to_string());
+
+    let mut name: Option<String> = None;
+    let mut description: Option<String> = None;
+    let mut type_str: Option<String> = None;
+    let mut in_metadata = false;
+
+    for raw in block.lines() {
+        if raw.trim().is_empty() {
+            continue;
+        }
+        let indented = raw.starts_with(' ') || raw.starts_with('\t');
+        let (key, value) = raw
+            .split_once(':')
+            .ok_or_else(|| err("frontmatter line missing `:`"))?;
+        let key = key.trim();
+        let value = value.trim();
+
+        if !indented {
+            in_metadata = false;
+            match key {
+                "name" => name = Some(value.to_string()),
+                "description" => description = Some(value.to_string()),
+                "metadata" => {
+                    in_metadata = true;
+                    if !value.is_empty() {
+                        return Err(err("`metadata` must be a nested block"));
+                    }
+                }
+                _ => return Err(err("unknown frontmatter key")),
+            }
+        } else if in_metadata && key == "type" {
+            type_str = Some(value.to_string());
+        } else {
+            return Err(err("unexpected indented frontmatter line"));
+        }
+    }
+
+    let name = name.ok_or_else(|| err("missing `name`"))?;
+    let description = description.ok_or_else(|| err("missing `description`"))?;
+    let type_str = type_str.ok_or_else(|| err("missing `metadata.type`"))?;
+
+    let name = MemorySlug::new(name).map_err(|e| MemoryError::Frontmatter(e.to_string()))?;
+    let r#type = str_to_type(&type_str).ok_or_else(|| err("unknown `metadata.type` value"))?;
+
+    Ok(MemoryFrontmatter {
+        name,
+        description,
+        r#type,
+    })
+}
+
+/// Renders the aggregated `MEMORY.md` index.
+fn render_index(entries: &[MemoryIndexEntry]) -> String {
+    let mut out = String::from(INDEX_HEADER);
+    out.push('\n');
+    if !entries.is_empty() {
+        out.push('\n');
+        for e in entries {
+            out.push_str(&format!(
+                "- [{}]({}.md) — {}\n",
+                e.title,
+                e.slug.as_str(),
+                e.hook
+            ));
+        }
+    }
+    out
+}
+
+/// Parses the `MEMORY.md` index lines back into structured entries. Lines that do
+/// not match the `- [Title](slug.md) — hook` shape are skipped (tolerant read);
+/// the `type` is not stored in the index line and defaults to
+/// [`MemoryType::Reference`].
+fn parse_index(text: &str) -> Vec<MemoryIndexEntry> {
+    let mut out = Vec::new();
+    for line in text.lines() {
+        let line = line.trim();
+        if !line.starts_with("- [") {
+            continue;
+        }
+        if let Some(entry) = parse_index_line(line) {
+            out.push(entry);
+        }
+    }
+    out
+}
+
+/// Parses one `- [Title](slug.md) — hook` line.
+fn parse_index_line(line: &str) -> Option<MemoryIndexEntry> {
+    let rest = line.strip_prefix("- [")?;
+    let (title, rest) = rest.split_once("](")?;
+    let (target, rest) = rest.split_once(')')?;
+    let slug_str = target.strip_suffix(".md").unwrap_or(target);
+    let slug = MemorySlug::new(slug_str).ok()?;
+    let hook = rest.trim_start().strip_prefix('—').unwrap_or(rest).trim();
+    Some(MemoryIndexEntry {
+        slug,
+        title: title.to_string(),
+        hook: hook.to_string(),
+        r#type: MemoryType::Reference,
+    })
+}
+
+/// Maps a [`MemoryType`] to its YAML/string form (matches serde camelCase).
+fn type_to_str(t: MemoryType) -> &'static str {
+    match t {
+        MemoryType::User => "user",
+        MemoryType::Feedback => "feedback",
+        MemoryType::Project => "project",
+        MemoryType::Reference => "reference",
+    }
+}
+
+/// Parses a [`MemoryType`] from its string form.
+fn str_to_type(s: &str) -> Option<MemoryType> {
+    match s {
+        "user" => Some(MemoryType::User),
+        "feedback" => Some(MemoryType::Feedback),
+        "project" => Some(MemoryType::Project),
+        "reference" => Some(MemoryType::Reference),
+        _ => None,
+    }
+}

crates/infrastructure/src/store/mod.rs

@@ -5,13 +5,19 @@
 //! JSON files in the app data directory (machine-local, outside any project).
 
 mod context;
+mod embedder;
+mod memory;
 mod profile;
 mod project;
 mod skill;
 mod template;
+mod vector;
 
 pub use context::IdeaiContextStore;
-pub use profile::FsProfileStore;
+pub use embedder::{embedder_from_profile, HashEmbedder, StubEmbedder};
+pub use memory::{index_token_size, FsMemoryStore, NaiveMemoryRecall};
+pub use profile::{FsEmbedderProfileStore, FsProfileStore};
 pub use project::FsProjectStore;
 pub use skill::FsSkillStore;
 pub use template::FsTemplateStore;
+pub use vector::{should_use_vector, AdaptiveMemoryRecall, VectorMemoryRecall};

crates/infrastructure/src/store/profile.rs

@@ -24,7 +24,7 @@ use serde::{Deserialize, Serialize};
 
 use domain::ids::ProfileId;
 use domain::ports::{FileSystem, ProfileStore, RemotePath, StoreError};
-use domain::profile::AgentProfile;
+use domain::profile::{AgentProfile, EmbedderProfile};
 
 /// File name of the profiles store inside the app-data dir.
 const PROFILES_FILE: &str = "profiles.json";
@@ -147,3 +147,126 @@ impl ProfileStore for FsProfileStore {
         self.write_doc(&doc).await
     }
 }
+
+// ---------------------------------------------------------------------------
+// FsEmbedderProfileStore — declarative embedder profiles (`embedder.json`, LOT C).
+// ---------------------------------------------------------------------------
+
+/// File name of the embedder-profiles store inside the app-data dir.
+const EMBEDDER_FILE: &str = "embedder.json";
+
+/// Current schema version of the embedder-profiles file.
+const EMBEDDER_VERSION: u32 = 1;
+
+/// On-disk shape of `embedder.json` (LOT C, §14.5.3), mirroring [`ProfilesDoc`].
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct EmbedderDoc {
+    /// Schema version.
+    version: u32,
+    /// All configured embedder profiles.
+    profiles: Vec<EmbedderProfile>,
+}
+
+impl Default for EmbedderDoc {
+    fn default() -> Self {
+        Self {
+            version: EMBEDDER_VERSION,
+            profiles: Vec::new(),
+        }
+    }
+}
+
+/// JSON-file store for declarative [`EmbedderProfile`]s (LOT C, étage 2 vectoriel),
+/// calqué on [`FsProfileStore`]: `embedder.json` in the global IDE app-data dir,
+/// mirroring `profiles.json`.
+///
+/// No domain `EmbedderProfileStore` port exists yet — embedder profiles are pure
+/// configuration loaded at the composition root, so this is a concrete loader. A
+/// dedicated port (parallel to [`ProfileStore`]) is an easy follow-up the day the
+/// UI needs CRUD over embedder profiles.
+///
+/// Cheap to clone (everything behind `Arc`).
+#[derive(Clone)]
+pub struct FsEmbedderProfileStore {
+    fs: Arc<dyn FileSystem>,
+    app_data_dir: String,
+}
+
+impl FsEmbedderProfileStore {
+    /// Builds the store from an injected [`FileSystem`] and the app-data dir.
+    #[must_use]
+    pub fn new(fs: Arc<dyn FileSystem>, app_data_dir: impl Into<String>) -> Self {
+        Self {
+            fs,
+            app_data_dir: app_data_dir.into(),
+        }
+    }
+
+    /// `<app-data-dir>/embedder.json`.
+    fn path(&self) -> RemotePath {
+        let base = self.app_data_dir.trim_end_matches(['/', '\\']);
+        RemotePath::new(format!("{base}/{EMBEDDER_FILE}"))
+    }
+
+    async fn read_doc(&self) -> Result<EmbedderDoc, StoreError> {
+        match self.fs.read(&self.path()).await {
+            Ok(bytes) => {
+                serde_json::from_slice(&bytes).map_err(|e| StoreError::Serialization(e.to_string()))
+            }
+            Err(domain::ports::FsError::NotFound(_)) => Ok(EmbedderDoc::default()),
+            Err(e) => Err(StoreError::Io(e.to_string())),
+        }
+    }
+
+    async fn write_doc(&self, doc: &EmbedderDoc) -> Result<(), StoreError> {
+        let dir = RemotePath::new(self.app_data_dir.trim_end_matches(['/', '\\']).to_owned());
+        self.fs
+            .create_dir_all(&dir)
+            .await
+            .map_err(|e| StoreError::Io(e.to_string()))?;
+        let bytes =
+            serde_json::to_vec_pretty(doc).map_err(|e| StoreError::Serialization(e.to_string()))?;
+        self.fs
+            .write(&self.path(), &bytes)
+            .await
+            .map_err(|e| StoreError::Io(e.to_string()))
+    }
+
+    /// Lists all configured embedder profiles (empty when `embedder.json` is
+    /// absent — the default `none` posture).
+    ///
+    /// # Errors
+    /// [`StoreError`] on an I/O or deserialisation failure.
+    pub async fn list(&self) -> Result<Vec<EmbedderProfile>, StoreError> {
+        Ok(self.read_doc().await?.profiles)
+    }
+
+    /// Saves (creates or replaces by id) an embedder profile.
+    ///
+    /// # Errors
+    /// [`StoreError`] on failure.
+    pub async fn save(&self, profile: &EmbedderProfile) -> Result<(), StoreError> {
+        let mut doc = self.read_doc().await?;
+        if let Some(slot) = doc.profiles.iter_mut().find(|p| p.id == profile.id) {
+            *slot = profile.clone();
+        } else {
+            doc.profiles.push(profile.clone());
+        }
+        self.write_doc(&doc).await
+    }
+
+    /// Deletes an embedder profile by id.
+    ///
+    /// # Errors
+    /// [`StoreError::NotFound`] if no profile carries that id.
+    pub async fn delete(&self, id: &str) -> Result<(), StoreError> {
+        let mut doc = self.read_doc().await?;
+        let before = doc.profiles.len();
+        doc.profiles.retain(|p| p.id != id);
+        if doc.profiles.len() == before {
+            return Err(StoreError::NotFound);
+        }
+        self.write_doc(&doc).await
+    }
+}

crates/infrastructure/src/store/vector.rs

@@ -0,0 +1,347 @@
+//! Étage-2 semantic recall (LOT C, §14.5.3): [`VectorMemoryRecall`] and the
+//! [`AdaptiveMemoryRecall`] switch.
+//!
+//! [`VectorMemoryRecall`] composes an [`Embedder`] + a [`MemoryStore`] + a small
+//! **derived vector store** under `.ideai/memory/.index/`, ranks the memory index
+//! entries by cosine similarity to the query, and truncates to the token budget —
+//! the **same** budget/emptiness semantics as [`super::NaiveMemoryRecall`]
+//! (Liskov), only the relevance strategy differs.
+//!
+//! [`AdaptiveMemoryRecall`] composes both and routes between them by an
+//! **objective, pure, I/O-free** decision ([`should_use_vector`]): tiny memories
+//! or a `none` strategy go to the naïve recall; otherwise to the vector recall,
+//! with an automatic **fallback to naïve** whenever the embedder is unavailable.
+//! No path of this module ever fails hard on a missing/unavailable embedder.
+//!
+//! ## Derived vector store format
+//!
+//! `.ideai/memory/.index/vectors.json` holds, per slug, the embedding of that
+//! note's index line (title + hook), tagged with the producing embedder id and
+//! its dimension:
+//!
+//! ```json
+//! {
+//!   "version": 1,
+//!   "embedderId": "hash-embedder",
+//!   "dimension": 64,
+//!   "vectors": { "my-note": [0.1, 0.0, ...] }
+//! }
+//! ```
+//!
+//! It is **derived data, fully reconstructible** from the `.md` source of truth,
+//! and is **gitignored** (`.ideai/memory/.index/`). A stale or absent file is not
+//! an error: missing vectors are recomputed on demand and the file is refreshed
+//! best-effort. A change of embedder id/dimension invalidates the whole file.
+
+use std::collections::HashMap;
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use serde::{Deserialize, Serialize};
+
+use domain::memory::MemoryIndexEntry;
+use domain::ports::{
+    Embedder, EmbedderError, FileSystem, FsError, MemoryError, MemoryQuery, MemoryRecall,
+    MemoryStore, RemotePath,
+};
+use domain::profile::EmbedderStrategy;
+use domain::project::ProjectPath;
+
+use super::memory::{index_token_size, truncate_to_budget};
+
+/// `.ideai/` directory name (mirrors [`super::memory`]).
+const IDEAI_DIR: &str = ".ideai";
+/// Memory sub-dir.
+const MEMORY_DIR: &str = "memory";
+/// Derived vector-store sub-dir (gitignored).
+const INDEX_DIR: &str = ".index";
+/// Derived vector-store file.
+const VECTORS_FILE: &str = "vectors.json";
+/// Schema version of the derived vector store.
+const VECTORS_VERSION: u32 = 1;
+
+/// On-disk shape of `.ideai/memory/.index/vectors.json`.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct VectorDoc {
+    /// Schema version.
+    version: u32,
+    /// Id of the embedder that produced these vectors (a mismatch invalidates).
+    embedder_id: String,
+    /// Vector length (a mismatch invalidates).
+    dimension: usize,
+    /// Per-slug embedding of the note's index line.
+    vectors: HashMap<String, Vec<f32>>,
+}
+
+impl VectorDoc {
+    fn new(embedder_id: String, dimension: usize) -> Self {
+        Self {
+            version: VECTORS_VERSION,
+            embedder_id,
+            dimension,
+            vectors: HashMap::new(),
+        }
+    }
+
+    /// Whether this doc was produced by the given embedder (id + dimension).
+    fn matches(&self, embedder_id: &str, dimension: usize) -> bool {
+        self.version == VECTORS_VERSION
+            && self.embedder_id == embedder_id
+            && self.dimension == dimension
+    }
+}
+
+/// Semantic [`MemoryRecall`] (étage 2): ranks the memory index by cosine
+/// similarity of each note's index line to the query text, truncated to the token
+/// budget (identical budget semantics to [`super::NaiveMemoryRecall`]).
+///
+/// Composes an [`Embedder`], a [`MemoryStore`] (the index source of truth), and a
+/// [`FileSystem`] for the derived vector cache. **Best-effort**: any
+/// [`EmbedderError`] surfaces as [`EmbedderError`] to the caller
+/// ([`AdaptiveMemoryRecall`] turns it into a naïve fallback); a missing/empty
+/// memory yields an empty list, never an error.
+#[derive(Clone)]
+pub struct VectorMemoryRecall {
+    embedder: Arc<dyn Embedder>,
+    store: Arc<dyn MemoryStore>,
+    fs: Arc<dyn FileSystem>,
+}
+
+impl VectorMemoryRecall {
+    /// Builds the vector recall from its composed ports.
+    #[must_use]
+    pub fn new(
+        embedder: Arc<dyn Embedder>,
+        store: Arc<dyn MemoryStore>,
+        fs: Arc<dyn FileSystem>,
+    ) -> Self {
+        Self {
+            embedder,
+            store,
+            fs,
+        }
+    }
+
+    /// `<root>/.ideai/memory/.index`.
+    fn index_dir(root: &ProjectPath) -> String {
+        let base = root.as_str().trim_end_matches(['/', '\\']);
+        format!("{base}/{IDEAI_DIR}/{MEMORY_DIR}/{INDEX_DIR}")
+    }
+
+    /// `<index-dir>/vectors.json`.
+    fn vectors_path(root: &ProjectPath) -> RemotePath {
+        RemotePath::new(format!("{}/{VECTORS_FILE}", Self::index_dir(root)))
+    }
+
+    /// The text embedded for an index entry (its index-line payload).
+    fn entry_text(entry: &MemoryIndexEntry) -> String {
+        format!("{} {}", entry.title, entry.hook)
+    }
+
+    /// Loads the derived vector doc, or a fresh empty one when absent, malformed,
+    /// or produced by a different embedder/dimension (best-effort: never errors on
+    /// a stale cache — it is simply rebuilt).
+    async fn load_doc(&self, root: &ProjectPath) -> VectorDoc {
+        let empty = || VectorDoc::new(self.embedder.id().to_owned(), self.embedder.dimension());
+        match self.fs.read(&Self::vectors_path(root)).await {
+            Ok(bytes) => match serde_json::from_slice::<VectorDoc>(&bytes) {
+                Ok(doc) if doc.matches(self.embedder.id(), self.embedder.dimension()) => doc,
+                _ => empty(),
+            },
+            Err(FsError::NotFound(_)) | Err(_) => empty(),
+        }
+    }
+
+    /// Persists the derived vector doc best-effort (a write failure is swallowed:
+    /// the cache is reconstructible, recall already has its result).
+    async fn save_doc(&self, root: &ProjectPath, doc: &VectorDoc) {
+        let dir = RemotePath::new(Self::index_dir(root));
+        if self.fs.create_dir_all(&dir).await.is_err() {
+            return;
+        }
+        if let Ok(bytes) = serde_json::to_vec_pretty(doc) {
+            let _ = self.fs.write(&Self::vectors_path(root), &bytes).await;
+        }
+    }
+}
+
+#[async_trait]
+impl MemoryRecall for VectorMemoryRecall {
+    async fn recall(
+        &self,
+        root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        if query.token_budget == 0 {
+            return Ok(Vec::new());
+        }
+        let entries = self.store.read_index(root).await?;
+        if entries.is_empty() {
+            return Ok(Vec::new());
+        }
+
+        // Load the derived cache and compute any missing note vectors.
+        let mut doc = self.load_doc(root).await;
+        let missing: Vec<&MemoryIndexEntry> = entries
+            .iter()
+            .filter(|e| !doc.vectors.contains_key(e.slug.as_str()))
+            .collect();
+        if !missing.is_empty() {
+            let texts: Vec<String> = missing.iter().map(|e| Self::entry_text(e)).collect();
+            let vectors = self.recall_embed(&texts).await?;
+            for (entry, vector) in missing.iter().zip(vectors) {
+                doc.vectors.insert(entry.slug.as_str().to_owned(), vector);
+            }
+            // Drop vectors of notes that no longer exist, then persist best-effort.
+            let live: std::collections::HashSet<&str> =
+                entries.iter().map(|e| e.slug.as_str()).collect();
+            doc.vectors.retain(|slug, _| live.contains(slug.as_str()));
+            self.save_doc(root, &doc).await;
+        }
+
+        // Embed the query and rank by cosine similarity (descending).
+        let query_vec = self
+            .recall_embed(std::slice::from_ref(&query.text))
+            .await?
+            .into_iter()
+            .next()
+            .unwrap_or_default();
+
+        let mut ranked: Vec<(f32, MemoryIndexEntry)> = entries
+            .into_iter()
+            .map(|entry| {
+                let score = doc
+                    .vectors
+                    .get(entry.slug.as_str())
+                    .map_or(0.0, |v| cosine_similarity(&query_vec, v));
+                (score, entry)
+            })
+            .collect();
+        // Stable, deterministic order: score desc, then slug asc for ties.
+        ranked.sort_by(|a, b| {
+            b.0.partial_cmp(&a.0)
+                .unwrap_or(std::cmp::Ordering::Equal)
+                .then_with(|| a.1.slug.cmp(&b.1.slug))
+        });
+
+        let ordered = ranked.into_iter().map(|(_, e)| e);
+        Ok(truncate_to_budget(ordered, query.token_budget))
+    }
+}
+
+impl VectorMemoryRecall {
+    /// Embeds `texts`, mapping an [`EmbedderError`] into a [`MemoryError`] only so
+    /// the `?` plumbing compiles; in practice [`AdaptiveMemoryRecall`] guards this
+    /// path and falls back to naïve before any such error reaches a use case.
+    async fn recall_embed(&self, texts: &[String]) -> Result<Vec<Vec<f32>>, MemoryError> {
+        self.embedder
+            .embed(texts)
+            .await
+            .map_err(map_embedder_error)
+    }
+}
+
+/// Maps an [`EmbedderError`] to a [`MemoryError`] for the (guarded) `?` path.
+fn map_embedder_error(e: EmbedderError) -> MemoryError {
+    match e {
+        EmbedderError::Io(m) => MemoryError::Io(m),
+        other => MemoryError::Serialization(other.to_string()),
+    }
+}
+
+/// Cosine similarity of two equal-length vectors; `0.0` when a length mismatches
+/// or either vector is zero (defensive — never panics).
+fn cosine_similarity(a: &[f32], b: &[f32]) -> f32 {
+    if a.len() != b.len() {
+        return 0.0;
+    }
+    let dot: f32 = a.iter().zip(b).map(|(x, y)| x * y).sum();
+    let na: f32 = a.iter().map(|x| x * x).sum::<f32>().sqrt();
+    let nb: f32 = b.iter().map(|x| x * x).sum::<f32>().sqrt();
+    if na == 0.0 || nb == 0.0 {
+        0.0
+    } else {
+        dot / (na * nb)
+    }
+}
+
+// ---------------------------------------------------------------------------
+// AdaptiveMemoryRecall — the étage-1/étage-2 switch.
+// ---------------------------------------------------------------------------
+
+/// **Pure, I/O-free** routing decision for [`AdaptiveMemoryRecall`].
+///
+/// Returns `true` (use the vector recall) **iff** the strategy is not
+/// [`EmbedderStrategy::None`] **and** the memory is larger than the budget
+/// (i.e. there is something to rank/prune semantically). Otherwise the naïve
+/// recall is sufficient and cheaper. This is the single objective rule, unit
+/// testable without any store.
+#[must_use]
+pub fn should_use_vector(memory_size: usize, budget: usize, strategy: EmbedderStrategy) -> bool {
+    if strategy == EmbedderStrategy::None {
+        return false;
+    }
+    memory_size > budget
+}
+
+/// Adaptive [`MemoryRecall`]: routes between a naïve étage-1 recall and a vector
+/// étage-2 recall by [`should_use_vector`], with an automatic **fallback to
+/// naïve** whenever the vector path fails (embedder unavailable/unsupported).
+///
+/// Substitutable for either composed recall (Liskov): same emptiness/budget
+/// guarantees, and — by construction — it **never fails hard** on an embedder
+/// problem. With strategy [`EmbedderStrategy::None`] it is behaviourally identical
+/// to the naïve recall (the default product posture, zero dependency).
+#[derive(Clone)]
+pub struct AdaptiveMemoryRecall {
+    naive: Arc<dyn MemoryRecall>,
+    vector: Arc<dyn MemoryRecall>,
+    store: Arc<dyn MemoryStore>,
+    strategy: EmbedderStrategy,
+}
+
+impl AdaptiveMemoryRecall {
+    /// Builds the switch from the two recalls, the index store (for the pure size
+    /// measure), and the active embedder strategy.
+    #[must_use]
+    pub fn new(
+        naive: Arc<dyn MemoryRecall>,
+        vector: Arc<dyn MemoryRecall>,
+        store: Arc<dyn MemoryStore>,
+        strategy: EmbedderStrategy,
+    ) -> Self {
+        Self {
+            naive,
+            vector,
+            store,
+            strategy,
+        }
+    }
+}
+
+#[async_trait]
+impl MemoryRecall for AdaptiveMemoryRecall {
+    async fn recall(
+        &self,
+        root: &ProjectPath,
+        query: &MemoryQuery,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        // Budget-0 short-circuits before any I/O, homogeneously with the naïve and
+        // vector recalls (a zero budget can hold no entry: nothing to read/measure).
+        if query.token_budget == 0 {
+            return Ok(Vec::new());
+        }
+        // Pure measure from the index (the only I/O is reading the index once;
+        // the decision itself is pure via `should_use_vector`).
+        let memory_size = index_token_size(&self.store.read_index(root).await?);
+        if !should_use_vector(memory_size, query.token_budget, self.strategy) {
+            return self.naive.recall(root, query).await;
+        }
+        // Vector path with naïve fallback — never fail hard on the embedder.
+        match self.vector.recall(root, query).await {
+            Ok(entries) => Ok(entries),
+            Err(_) => self.naive.recall(root, query).await,
+        }
+    }
+}

crates/infrastructure/tests/memory_recall.rs

@@ -0,0 +1,277 @@
+//! Tests for [`NaiveMemoryRecall`] (LOT B, étage 1): the default, dependency-free
+//! [`MemoryRecall`] that reads the aggregated index via a composed [`MemoryStore`]
+//! and truncates the entries to fit the query's token budget.
+//!
+//! Budget semantics under test (mirroring the adapter doc): each entry costs
+//! `ceil((title.len() + hook.len()) / 4)` tokens; entries are taken in index order,
+//! accumulating cost; the first entry that would exceed the budget — and every one
+//! after it — is dropped. `token_budget == 0` ⇒ empty; an empty/absent memory ⇒
+//! empty, never an error.
+//!
+//! Two backings are exercised:
+//! - the **real** [`FsMemoryStore`] over an in-memory [`FileSystem`] mock (same
+//!   `MemFs` shape as `memory_store.rs`), giving end-to-end coverage of the
+//!   index round-trip feeding recall;
+//! - a tiny **counting fake** `MemoryStore` to assert the `budget == 0`
+//!   short-circuit performs *no* `read_index` call.
+
+use std::collections::HashMap;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+
+use domain::markdown::MarkdownDoc;
+use domain::memory::{Memory, MemoryFrontmatter, MemoryIndexEntry, MemoryLink, MemorySlug, MemoryType};
+use domain::ports::{
+    DirEntry, FileSystem, FsError, MemoryError, MemoryQuery, MemoryRecall, MemoryStore, RemotePath,
+};
+use domain::project::ProjectPath;
+use infrastructure::{FsMemoryStore, NaiveMemoryRecall};
+
+// ---------------------------------------------------------------------------
+// In-memory FileSystem mock (same minimal shape as `memory_store.rs`).
+// ---------------------------------------------------------------------------
+
+#[derive(Default)]
+struct MemFs {
+    files: Mutex<HashMap<String, Vec<u8>>>,
+}
+
+impl MemFs {
+    fn arc() -> Arc<Self> {
+        Arc::new(Self::default())
+    }
+}
+
+#[async_trait]
+impl FileSystem for MemFs {
+    async fn read(&self, path: &RemotePath) -> Result<Vec<u8>, FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .get(path.as_str())
+            .cloned()
+            .ok_or_else(|| FsError::NotFound(path.as_str().to_string()))
+    }
+    async fn write(&self, path: &RemotePath, data: &[u8]) -> Result<(), FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .insert(path.as_str().to_string(), data.to_vec());
+        Ok(())
+    }
+    async fn exists(&self, path: &RemotePath) -> Result<bool, FsError> {
+        Ok(self.files.lock().unwrap().contains_key(path.as_str()))
+    }
+    async fn create_dir_all(&self, _path: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+    async fn list(&self, _path: &RemotePath) -> Result<Vec<DirEntry>, FsError> {
+        Ok(Vec::new())
+    }
+    async fn symlink(&self, _src: &RemotePath, _dst: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Builders
+// ---------------------------------------------------------------------------
+
+fn root() -> ProjectPath {
+    ProjectPath::new("/proj").unwrap()
+}
+
+/// A note whose index `title` is its slug (length `slug.len()`) and whose `hook`
+/// is `desc` — so the recall cost is `ceil((slug.len() + desc.len()) / 4)`.
+fn note(slug: &str, desc: &str) -> Memory {
+    Memory::new(
+        MemoryFrontmatter {
+            name: MemorySlug::new(slug).unwrap(),
+            description: desc.to_string(),
+            r#type: MemoryType::Project,
+        },
+        MarkdownDoc::new("# body"),
+    )
+    .unwrap()
+}
+
+/// Saves notes (in order) through the real store and returns a recall over it.
+async fn recall_over(notes: &[Memory]) -> NaiveMemoryRecall {
+    let store = Arc::new(FsMemoryStore::new(MemFs::arc()));
+    for n in notes {
+        store.save(&root(), n).await.unwrap();
+    }
+    NaiveMemoryRecall::new(store)
+}
+
+fn query(budget: usize) -> MemoryQuery {
+    MemoryQuery {
+        text: "anything".to_string(),
+        token_budget: budget,
+    }
+}
+
+fn slugs(entries: &[MemoryIndexEntry]) -> Vec<String> {
+    entries.iter().map(|e| e.slug.as_str().to_string()).collect()
+}
+
+// ---------------------------------------------------------------------------
+// Empty / absent memory ⇒ empty list, never an error.
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn absent_index_recalls_empty_without_error() {
+    let recall = NaiveMemoryRecall::new(Arc::new(FsMemoryStore::new(MemFs::arc())));
+    let out = recall.recall(&root(), &query(1000)).await.unwrap();
+    assert!(out.is_empty(), "absent memory must recall empty: {out:?}");
+}
+
+// ---------------------------------------------------------------------------
+// Budget 0 ⇒ empty list (and short-circuits before touching the store).
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn zero_budget_recalls_empty() {
+    let recall = recall_over(&[note("aaaa", "bbbb"), note("cccc", "dddd")]).await;
+    let out = recall.recall(&root(), &query(0)).await.unwrap();
+    assert!(out.is_empty(), "budget 0 must recall empty: {out:?}");
+}
+
+/// A `MemoryStore` that counts `read_index` calls and panics on every other
+/// method — proving the recall path only reads the index, and that a `0` budget
+/// short-circuits before any read.
+#[derive(Default)]
+struct CountingStore {
+    read_index_calls: AtomicUsize,
+}
+
+#[async_trait]
+impl MemoryStore for CountingStore {
+    async fn list(&self, _root: &ProjectPath) -> Result<Vec<Memory>, MemoryError> {
+        panic!("recall must not call list")
+    }
+    async fn get(&self, _root: &ProjectPath, _slug: &MemorySlug) -> Result<Memory, MemoryError> {
+        panic!("recall must not call get")
+    }
+    async fn save(&self, _root: &ProjectPath, _memory: &Memory) -> Result<(), MemoryError> {
+        panic!("recall must not call save")
+    }
+    async fn delete(&self, _root: &ProjectPath, _slug: &MemorySlug) -> Result<(), MemoryError> {
+        panic!("recall must not call delete")
+    }
+    async fn read_index(
+        &self,
+        _root: &ProjectPath,
+    ) -> Result<Vec<MemoryIndexEntry>, MemoryError> {
+        self.read_index_calls.fetch_add(1, Ordering::SeqCst);
+        Ok(Vec::new())
+    }
+    async fn resolve_links(
+        &self,
+        _root: &ProjectPath,
+        _slug: &MemorySlug,
+    ) -> Result<Vec<MemoryLink>, MemoryError> {
+        panic!("recall must not call resolve_links")
+    }
+}
+
+#[tokio::test]
+async fn zero_budget_short_circuits_no_read_index() {
+    let store = Arc::new(CountingStore::default());
+    let recall = NaiveMemoryRecall::new(store.clone());
+    let out = recall.recall(&root(), &query(0)).await.unwrap();
+    assert!(out.is_empty());
+    assert_eq!(
+        store.read_index_calls.load(Ordering::SeqCst),
+        0,
+        "budget 0 must short-circuit before reading the index"
+    );
+}
+
+#[tokio::test]
+async fn nonzero_budget_reads_index_once() {
+    let store = Arc::new(CountingStore::default());
+    let recall = NaiveMemoryRecall::new(store.clone());
+    let _ = recall.recall(&root(), &query(10)).await.unwrap();
+    assert_eq!(store.read_index_calls.load(Ordering::SeqCst), 1);
+}
+
+// ---------------------------------------------------------------------------
+// Sufficient budget ⇒ all entries, in index order.
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn ample_budget_returns_all_entries_in_index_order() {
+    // Saved order: alpha, beta, gamma → index order is the same.
+    let recall = recall_over(&[
+        note("alpha", "first hook"),
+        note("beta", "second hook"),
+        note("gamma", "third hook"),
+    ])
+    .await;
+    let out = recall.recall(&root(), &query(100_000)).await.unwrap();
+    assert_eq!(slugs(&out), vec!["alpha", "beta", "gamma"]);
+}
+
+// ---------------------------------------------------------------------------
+// Intermediate budget ⇒ exact truncation at the cumulative-cost boundary.
+//
+// Three notes, each title.len()==4 and hook.len()==4 ⇒ 8 chars ⇒ ceil(8/4)==2
+// tokens apiece. Cumulative costs: 2, 4, 6.
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn intermediate_budget_truncates_at_exact_boundary() {
+    let notes = [note("aaaa", "bbbb"), note("cccc", "dddd"), note("eeee", "ffff")];
+    let recall = recall_over(&notes).await;
+
+    // Budget 1 < 2 ⇒ first entry already exceeds ⇒ none.
+    assert!(recall.recall(&root(), &query(1)).await.unwrap().is_empty());
+
+    // Budget 2 == cost(1) ⇒ exactly the first entry; second (would reach 4) dropped.
+    assert_eq!(slugs(&recall.recall(&root(), &query(2)).await.unwrap()), vec!["aaaa"]);
+
+    // Budget 3 < 4 ⇒ still only the first.
+    assert_eq!(slugs(&recall.recall(&root(), &query(3)).await.unwrap()), vec!["aaaa"]);
+
+    // Budget 4 == cost(1)+cost(2) ⇒ first two; third (would reach 6) dropped.
+    assert_eq!(
+        slugs(&recall.recall(&root(), &query(4)).await.unwrap()),
+        vec!["aaaa", "cccc"]
+    );
+
+    // Budget 5 < 6 ⇒ still the first two.
+    assert_eq!(
+        slugs(&recall.recall(&root(), &query(5)).await.unwrap()),
+        vec!["aaaa", "cccc"]
+    );
+
+    // Budget 6 == total ⇒ all three.
+    assert_eq!(
+        slugs(&recall.recall(&root(), &query(6)).await.unwrap()),
+        vec!["aaaa", "cccc", "eeee"]
+    );
+}
+
+// ---------------------------------------------------------------------------
+// ceil rounding: an odd character count rounds *up* (5 chars ⇒ 2 tokens).
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn entry_cost_rounds_up_via_ceil() {
+    // slug "ab" (2) + hook "c" (1) = 3 chars ⇒ ceil(3/4) == 1 token.
+    // slug "de" (2) + hook "fgh" (3) = 5 chars ⇒ ceil(5/4) == 2 tokens.
+    let recall = recall_over(&[note("ab", "c"), note("de", "fgh")]).await;
+
+    // Budget 1 covers only the 1-token first entry; the 2-token second is dropped.
+    assert_eq!(slugs(&recall.recall(&root(), &query(1)).await.unwrap()), vec!["ab"]);
+    // Budget 2 still cannot fit the second on top of the first (1 + 2 = 3 > 2).
+    assert_eq!(slugs(&recall.recall(&root(), &query(2)).await.unwrap()), vec!["ab"]);
+    // Budget 3 fits both (1 + 2 == 3).
+    assert_eq!(
+        slugs(&recall.recall(&root(), &query(3)).await.unwrap()),
+        vec!["ab", "de"]
+    );
+}

crates/infrastructure/tests/memory_store.rs

@@ -0,0 +1,278 @@
+//! Tests for [`FsMemoryStore`] against an **in-memory mock** [`FileSystem`]:
+//! `save` writes the `<slug>.md` AND the `MEMORY.md` index line; get/list/delete;
+//! upsert idempotence (same slug => one index line); malformed frontmatter
+//! surfaces as [`MemoryError::Frontmatter`]; and `resolve_links` ignores broken
+//! links.
+
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+
+use domain::markdown::MarkdownDoc;
+use domain::memory::{Memory, MemoryFrontmatter, MemorySlug, MemoryType};
+use domain::ports::{DirEntry, FileSystem, FsError, MemoryError, MemoryStore, RemotePath};
+use domain::project::ProjectPath;
+use infrastructure::FsMemoryStore;
+
+/// A minimal in-memory [`FileSystem`] mock: a path -> bytes map behind a mutex.
+/// `create_dir_all`/`symlink`/`list` are no-ops or derived; only read/write/exists
+/// matter for the memory store.
+#[derive(Default)]
+struct MemFs {
+    files: Mutex<HashMap<String, Vec<u8>>>,
+}
+
+impl MemFs {
+    fn arc() -> Arc<Self> {
+        Arc::new(Self::default())
+    }
+    fn raw(&self, path: &str) -> Option<String> {
+        self.files
+            .lock()
+            .unwrap()
+            .get(path)
+            .map(|b| String::from_utf8(b.clone()).unwrap())
+    }
+    /// Directly seeds a file (to inject a malformed note bypassing the store).
+    fn put(&self, path: &str, content: &str) {
+        self.files
+            .lock()
+            .unwrap()
+            .insert(path.to_string(), content.as_bytes().to_vec());
+    }
+}
+
+#[async_trait]
+impl FileSystem for MemFs {
+    async fn read(&self, path: &RemotePath) -> Result<Vec<u8>, FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .get(path.as_str())
+            .cloned()
+            .ok_or_else(|| FsError::NotFound(path.as_str().to_string()))
+    }
+    async fn write(&self, path: &RemotePath, data: &[u8]) -> Result<(), FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .insert(path.as_str().to_string(), data.to_vec());
+        Ok(())
+    }
+    async fn exists(&self, path: &RemotePath) -> Result<bool, FsError> {
+        Ok(self.files.lock().unwrap().contains_key(path.as_str()))
+    }
+    async fn create_dir_all(&self, _path: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+    async fn list(&self, _path: &RemotePath) -> Result<Vec<DirEntry>, FsError> {
+        Ok(Vec::new())
+    }
+    async fn symlink(&self, _src: &RemotePath, _dst: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+}
+
+fn root() -> ProjectPath {
+    ProjectPath::new("/proj").unwrap()
+}
+
+fn slug(s: &str) -> MemorySlug {
+    MemorySlug::new(s).unwrap()
+}
+
+fn note(slug_str: &str, hook: &str, ty: MemoryType, body: &str) -> Memory {
+    Memory::new(
+        MemoryFrontmatter {
+            name: MemorySlug::new(slug_str).unwrap(),
+            description: hook.to_string(),
+            r#type: ty,
+        },
+        MarkdownDoc::new(body),
+    )
+    .unwrap()
+}
+
+#[tokio::test]
+async fn missing_index_lists_empty() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    assert!(store.list(&root()).await.unwrap().is_empty());
+    assert!(store.read_index(&root()).await.unwrap().is_empty());
+}
+
+#[tokio::test]
+async fn save_writes_md_and_index_line() {
+    let fs = MemFs::arc();
+    let store = FsMemoryStore::new(fs.clone());
+    store
+        .save(&root(), &note("alpha", "the hook", MemoryType::Project, "# Body"))
+        .await
+        .unwrap();
+
+    // The note `.md` exists with frontmatter + body.
+    let md = fs.raw("/proj/.ideai/memory/alpha.md").expect("note written");
+    assert!(md.starts_with("---\n"));
+    assert!(md.contains("name: alpha"));
+    assert!(md.contains("description: the hook"));
+    assert!(md.contains("type: project"));
+    assert!(md.contains("# Body"));
+
+    // The index has the header + the line.
+    let index = fs.raw("/proj/.ideai/memory/MEMORY.md").expect("index written");
+    assert!(index.starts_with("# Memory Index"));
+    assert!(index.contains("- [alpha](alpha.md) — the hook"));
+}
+
+#[tokio::test]
+async fn get_roundtrips_the_saved_note() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    let m = note("topic-x", "hook", MemoryType::Feedback, "content [[other]]");
+    store.save(&root(), &m).await.unwrap();
+
+    let got = store.get(&root(), &slug("topic-x")).await.unwrap();
+    assert_eq!(got, m);
+}
+
+#[tokio::test]
+async fn get_missing_is_not_found() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    assert!(matches!(
+        store.get(&root(), &slug("nope")).await.unwrap_err(),
+        MemoryError::NotFound
+    ));
+}
+
+#[tokio::test]
+async fn list_returns_all_saved_notes() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    store
+        .save(&root(), &note("a", "ha", MemoryType::User, "A"))
+        .await
+        .unwrap();
+    store
+        .save(&root(), &note("b", "hb", MemoryType::Project, "B"))
+        .await
+        .unwrap();
+
+    let mut slugs: Vec<_> = store
+        .list(&root())
+        .await
+        .unwrap()
+        .into_iter()
+        .map(|m| m.slug().as_str().to_string())
+        .collect();
+    slugs.sort();
+    assert_eq!(slugs, vec!["a".to_string(), "b".to_string()]);
+}
+
+#[tokio::test]
+async fn save_is_idempotent_upsert_single_index_line() {
+    let fs = MemFs::arc();
+    let store = FsMemoryStore::new(fs.clone());
+    store
+        .save(&root(), &note("dup", "hook v1", MemoryType::Project, "v1"))
+        .await
+        .unwrap();
+    store
+        .save(&root(), &note("dup", "hook v2", MemoryType::Project, "v2"))
+        .await
+        .unwrap();
+
+    // Content was replaced.
+    assert_eq!(
+        store
+            .get(&root(), &slug("dup"))
+            .await
+            .unwrap()
+            .body
+            .as_str(),
+        "v2"
+    );
+    // Exactly one index entry for the slug.
+    let entries = store.read_index(&root()).await.unwrap();
+    assert_eq!(entries.len(), 1);
+    assert_eq!(entries[0].hook, "hook v2");
+    // And the raw index has only one matching line.
+    let index = fs.raw("/proj/.ideai/memory/MEMORY.md").unwrap();
+    assert_eq!(index.matches("- [dup]").count(), 1);
+}
+
+#[tokio::test]
+async fn delete_removes_index_line_and_is_not_found_twice() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    store
+        .save(&root(), &note("gone", "h", MemoryType::User, "x"))
+        .await
+        .unwrap();
+
+    store.delete(&root(), &slug("gone")).await.unwrap();
+    assert!(store.list(&root()).await.unwrap().is_empty());
+    assert!(matches!(
+        store.delete(&root(), &slug("gone")).await.unwrap_err(),
+        MemoryError::NotFound
+    ));
+}
+
+#[tokio::test]
+async fn malformed_frontmatter_surfaces_as_error() {
+    let fs = MemFs::arc();
+    // Seed the index so the slug is listed, plus a malformed note file.
+    fs.put(
+        "/proj/.ideai/memory/MEMORY.md",
+        "# Memory Index\n\n- [bad](bad.md) — h\n",
+    );
+    fs.put(
+        "/proj/.ideai/memory/bad.md",
+        "no frontmatter fence here\njust body",
+    );
+    let store = FsMemoryStore::new(fs);
+
+    assert!(matches!(
+        store.get(&root(), &slug("bad")).await.unwrap_err(),
+        MemoryError::Frontmatter(_)
+    ));
+    // list propagates the same error.
+    assert!(matches!(
+        store.list(&root()).await.unwrap_err(),
+        MemoryError::Frontmatter(_)
+    ));
+}
+
+#[tokio::test]
+async fn resolve_links_ignores_broken_links() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    // `target` exists; `ghost` does not.
+    store
+        .save(&root(), &note("target", "h", MemoryType::Project, "T"))
+        .await
+        .unwrap();
+    store
+        .save(
+            &root(),
+            &note(
+                "src",
+                "h",
+                MemoryType::Project,
+                "links to [[target]] and [[ghost]]",
+            ),
+        )
+        .await
+        .unwrap();
+
+    let resolved = store.resolve_links(&root(), &slug("src")).await.unwrap();
+    let targets: Vec<_> = resolved
+        .into_iter()
+        .map(|l| l.target.as_str().to_string())
+        .collect();
+    assert_eq!(targets, vec!["target".to_string()]);
+}
+
+#[tokio::test]
+async fn resolve_links_missing_source_is_not_found() {
+    let store = FsMemoryStore::new(MemFs::arc());
+    assert!(matches!(
+        store.resolve_links(&root(), &slug("nope")).await.unwrap_err(),
+        MemoryError::NotFound
+    ));
+}

crates/infrastructure/tests/vector_recall.rs

@@ -0,0 +1,626 @@
+//! Tests for the étage-2 vector recall (LOT C, §14.5.3):
+//! - [`should_use_vector`] — the pure routing decision (full truth table);
+//! - [`AdaptiveMemoryRecall`] — the étage-1/étage-2 switch, with naïve equivalence
+//!   on strategy `none`, routing by size/budget, and the never-fail-hard fallback;
+//! - [`VectorMemoryRecall`] — semantic ranking with the deterministic
+//!   [`HashEmbedder`], budget truncation, the derived `vectors.json` cache and its
+//!   embedder-id/dimension invalidation, and `StubEmbedder` best-effort behaviour;
+//! - [`HashEmbedder`] / [`StubEmbedder`] embedder contracts;
+//! - [`embedder_from_profile`] strategy → embedder mapping.
+//!
+//! Everything is in-memory and deterministic (`MemFs` + `HashEmbedder`); no real
+//! I/O, no network.
+
+use std::collections::HashMap;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+
+use domain::markdown::MarkdownDoc;
+use domain::memory::{Memory, MemoryFrontmatter, MemoryIndexEntry, MemorySlug, MemoryType};
+use domain::ports::{
+    DirEntry, Embedder, EmbedderError, FileSystem, FsError, MemoryQuery, MemoryRecall, MemoryStore,
+    RemotePath,
+};
+use domain::profile::{EmbedderProfile, EmbedderStrategy};
+use domain::project::ProjectPath;
+use infrastructure::{
+    embedder_from_profile, should_use_vector, AdaptiveMemoryRecall, FsMemoryStore, HashEmbedder,
+    NaiveMemoryRecall, StubEmbedder, VectorMemoryRecall,
+};
+
+// ---------------------------------------------------------------------------
+// In-memory FileSystem mock (same shape as `memory_recall.rs` / `memory_store.rs`),
+// with raw read access to assert on the derived `vectors.json`.
+// ---------------------------------------------------------------------------
+
+#[derive(Default)]
+struct MemFs {
+    files: Mutex<HashMap<String, Vec<u8>>>,
+}
+
+impl MemFs {
+    fn arc() -> Arc<Self> {
+        Arc::new(Self::default())
+    }
+    fn raw(&self, path: &str) -> Option<String> {
+        self.files
+            .lock()
+            .unwrap()
+            .get(path)
+            .map(|b| String::from_utf8(b.clone()).unwrap())
+    }
+}
+
+#[async_trait]
+impl FileSystem for MemFs {
+    async fn read(&self, path: &RemotePath) -> Result<Vec<u8>, FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .get(path.as_str())
+            .cloned()
+            .ok_or_else(|| FsError::NotFound(path.as_str().to_string()))
+    }
+    async fn write(&self, path: &RemotePath, data: &[u8]) -> Result<(), FsError> {
+        self.files
+            .lock()
+            .unwrap()
+            .insert(path.as_str().to_string(), data.to_vec());
+        Ok(())
+    }
+    async fn exists(&self, path: &RemotePath) -> Result<bool, FsError> {
+        Ok(self.files.lock().unwrap().contains_key(path.as_str()))
+    }
+    async fn create_dir_all(&self, _path: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+    async fn list(&self, _path: &RemotePath) -> Result<Vec<DirEntry>, FsError> {
+        Ok(Vec::new())
+    }
+    async fn symlink(&self, _src: &RemotePath, _dst: &RemotePath) -> Result<(), FsError> {
+        Ok(())
+    }
+}
+
+const VECTORS_PATH: &str = "/proj/.ideai/memory/.index/vectors.json";
+
+// ---------------------------------------------------------------------------
+// A counting wrapper embedder: delegates to an inner embedder and counts the
+// number of *texts* it was asked to embed — to assert the derived cache avoids
+// recomputing note vectors on a second recall.
+// ---------------------------------------------------------------------------
+
+struct SpyEmbedder {
+    inner: HashEmbedder,
+    embedded_texts: AtomicUsize,
+}
+
+impl SpyEmbedder {
+    fn new(id: &str, dim: usize) -> Self {
+        Self {
+            inner: HashEmbedder::new(id, dim),
+            embedded_texts: AtomicUsize::new(0),
+        }
+    }
+}
+
+#[async_trait]
+impl Embedder for SpyEmbedder {
+    fn id(&self) -> &str {
+        self.inner.id()
+    }
+    async fn embed(&self, texts: &[String]) -> Result<Vec<Vec<f32>>, EmbedderError> {
+        self.embedded_texts.fetch_add(texts.len(), Ordering::SeqCst);
+        self.inner.embed(texts).await
+    }
+    fn dimension(&self) -> usize {
+        self.inner.dimension()
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Builders.
+// ---------------------------------------------------------------------------
+
+fn root() -> ProjectPath {
+    ProjectPath::new("/proj").unwrap()
+}
+
+/// A note whose index line is `<slug> <hook>` (title == slug). The vector recall
+/// embeds exactly `"{slug} {hook}"`, so picking distinct vocabulary words in
+/// `slug`/`hook` makes cosine similarity to a chosen query deterministic.
+fn note(slug: &str, hook: &str) -> Memory {
+    Memory::new(
+        MemoryFrontmatter {
+            name: MemorySlug::new(slug).unwrap(),
+            description: hook.to_string(),
+            r#type: MemoryType::Project,
+        },
+        MarkdownDoc::new("# body"),
+    )
+    .unwrap()
+}
+
+fn query(text: &str, budget: usize) -> MemoryQuery {
+    MemoryQuery {
+        text: text.to_string(),
+        token_budget: budget,
+    }
+}
+
+fn slugs(entries: &[MemoryIndexEntry]) -> Vec<String> {
+    entries.iter().map(|e| e.slug.as_str().to_string()).collect()
+}
+
+async fn store_with(notes: &[Memory], fs: Arc<MemFs>) -> Arc<FsMemoryStore> {
+    let store = Arc::new(FsMemoryStore::new(fs));
+    for n in notes {
+        store.save(&root(), n).await.unwrap();
+    }
+    store
+}
+
+// ===========================================================================
+// 1. should_use_vector — pure truth table.
+// ===========================================================================
+
+#[test]
+fn should_use_vector_none_strategy_is_always_false() {
+    // Even when size > budget, a `none` strategy never routes to the vector path.
+    assert!(!should_use_vector(0, 0, EmbedderStrategy::None));
+    assert!(!should_use_vector(100, 10, EmbedderStrategy::None));
+    assert!(!should_use_vector(10, 100, EmbedderStrategy::None));
+    assert!(!should_use_vector(usize::MAX, 0, EmbedderStrategy::None));
+}
+
+#[test]
+fn should_use_vector_non_none_iff_size_exceeds_budget() {
+    for strategy in [
+        EmbedderStrategy::LocalOnnx,
+        EmbedderStrategy::LocalServer,
+        EmbedderStrategy::Api,
+    ] {
+        // size > budget ⇒ true.
+        assert!(should_use_vector(11, 10, strategy), "{strategy:?}: 11>10");
+        assert!(should_use_vector(1, 0, strategy), "{strategy:?}: 1>0");
+        // size == budget ⇒ false (exact boundary).
+        assert!(!should_use_vector(10, 10, strategy), "{strategy:?}: 10==10");
+        assert!(!should_use_vector(0, 0, strategy), "{strategy:?}: 0==0");
+        // size < budget ⇒ false.
+        assert!(!should_use_vector(9, 10, strategy), "{strategy:?}: 9<10");
+    }
+}
+
+// ===========================================================================
+// 2. HashEmbedder — determinism, dimension, L2 normalisation.
+// ===========================================================================
+
+#[tokio::test]
+async fn hash_embedder_is_deterministic() {
+    let e = HashEmbedder::new("h", 64);
+    let a = e.embed(&["hello world".to_string()]).await.unwrap();
+    let b = e.embed(&["hello world".to_string()]).await.unwrap();
+    assert_eq!(a, b, "same text must give the same vector");
+}
+
+#[tokio::test]
+async fn hash_embedder_dimension_is_consistent() {
+    let e = HashEmbedder::new("h", 48);
+    assert_eq!(e.dimension(), 48);
+    let out = e
+        .embed(&["alpha beta".to_string(), "gamma".to_string()])
+        .await
+        .unwrap();
+    assert_eq!(out.len(), 2, "one vector per input, order preserved");
+    assert!(out.iter().all(|v| v.len() == 48), "every vector is dimension-long");
+}
+
+#[tokio::test]
+async fn hash_embedder_vectors_are_l2_normalised() {
+    let e = HashEmbedder::new("h", 64);
+    let out = e
+        .embed(&["one two three four".to_string()])
+        .await
+        .unwrap();
+    let norm = out[0].iter().map(|x| x * x).sum::<f32>().sqrt();
+    assert!((norm - 1.0).abs() < 1e-5, "norm ≈ 1, got {norm}");
+}
+
+#[tokio::test]
+async fn hash_embedder_empty_text_yields_zero_vector_no_panic() {
+    // No tokens ⇒ zero vector (norm 0, left unnormalised). Must not panic / NaN.
+    let e = HashEmbedder::new("h", 16);
+    let out = e.embed(&["".to_string()]).await.unwrap();
+    assert_eq!(out[0].len(), 16);
+    assert!(out[0].iter().all(|x| *x == 0.0));
+}
+
+// ===========================================================================
+// 3. StubEmbedder — always Unsupported, never panics.
+// ===========================================================================
+
+#[tokio::test]
+async fn stub_embedder_returns_unsupported() {
+    let e = StubEmbedder::new("stub", 32, "localOnnx");
+    assert_eq!(e.dimension(), 32);
+    let err = e.embed(&["x".to_string()]).await.unwrap_err();
+    assert!(matches!(err, EmbedderError::Unsupported(_)), "got {err:?}");
+}
+
+// ===========================================================================
+// 4. embedder_from_profile — strategy → embedder mapping.
+// ===========================================================================
+
+#[tokio::test]
+async fn embedder_from_profile_maps_each_strategy() {
+    // none ⇒ no embedder (recall stays naïve).
+    assert!(embedder_from_profile(&EmbedderProfile::none()).is_none());
+
+    // localOnnx / localServer / api ⇒ a StubEmbedder (Unsupported), dimension kept.
+    for strategy in [
+        EmbedderStrategy::LocalOnnx,
+        EmbedderStrategy::LocalServer,
+        EmbedderStrategy::Api,
+    ] {
+        let profile =
+            EmbedderProfile::new("e", "E", strategy, None, None, None, 24).unwrap();
+        let embedder = embedder_from_profile(&profile)
+            .unwrap_or_else(|| panic!("{strategy:?} must yield an embedder"));
+        assert_eq!(embedder.dimension(), 24);
+        let err = embedder.embed(&["t".to_string()]).await.unwrap_err();
+        assert!(
+            matches!(err, EmbedderError::Unsupported(_)),
+            "{strategy:?} stub must be Unsupported, got {err:?}"
+        );
+    }
+}
+
+// ===========================================================================
+// 5. VectorMemoryRecall — semantic ranking, budget, cache.
+// ===========================================================================
+
+/// Builds a vector recall over `notes` with the given embedder, sharing one fs.
+fn vector_recall(
+    embedder: Arc<dyn Embedder>,
+    store: Arc<FsMemoryStore>,
+    fs: Arc<MemFs>,
+) -> VectorMemoryRecall {
+    VectorMemoryRecall::new(embedder, store, fs)
+}
+
+#[tokio::test]
+async fn vector_recall_ranks_closest_note_first() {
+    // Notes have disjoint vocabularies; the query shares all tokens with `beta`,
+    // so `beta` must rank first (cosine == 1 for it, ~0 for the others).
+    let fs = MemFs::arc();
+    let notes = [
+        note("alpha", "apple orange grape"),
+        note("beta", "kiwi mango papaya"),
+        note("gamma", "carrot potato onion"),
+    ];
+    let store = store_with(&notes, fs.clone()).await;
+    let embedder = Arc::new(HashEmbedder::new("hash", 256));
+    let recall = vector_recall(embedder, store, fs);
+
+    // Query identical to beta's index line ("beta kiwi mango papaya").
+    let out = recall
+        .recall(&root(), &query("beta kiwi mango papaya", 100_000))
+        .await
+        .unwrap();
+    assert_eq!(out.first().map(|e| e.slug.as_str()), Some("beta"), "ranked: {:?}", slugs(&out));
+    // All three notes fit the ample budget.
+    assert_eq!(out.len(), 3);
+}
+
+#[tokio::test]
+async fn vector_recall_truncates_to_budget() {
+    // The closest note ("beta apricot apricot") must survive a tight budget while
+    // the rest are pruned. Cost of an entry = ceil((title+hook chars)/4).
+    let fs = MemFs::arc();
+    let notes = [
+        note("beta", "kiwi"),                 // "beta kiwi" → 8 chars → 2 tokens
+        note("alpha", "apple orange grape"),  // larger
+        note("gamma", "carrot potato onion"), // larger
+    ];
+    let store = store_with(&notes, fs.clone()).await;
+    let embedder = Arc::new(HashEmbedder::new("hash", 256));
+    let recall = vector_recall(embedder, store, fs);
+
+    // Budget 2 fits only the top-ranked `beta` (cost 2); the next would exceed.
+    let out = recall.recall(&root(), &query("beta kiwi", 2)).await.unwrap();
+    assert_eq!(slugs(&out), vec!["beta"], "budget must keep only the closest");
+}
+
+#[tokio::test]
+async fn vector_recall_zero_budget_and_empty_memory_are_empty() {
+    let fs = MemFs::arc();
+    let embedder = Arc::new(HashEmbedder::new("hash", 64));
+
+    // Empty memory ⇒ empty, no error.
+    let empty_store = Arc::new(FsMemoryStore::new(fs.clone()));
+    let recall = vector_recall(embedder.clone(), empty_store, fs.clone());
+    assert!(recall
+        .recall(&root(), &query("anything", 1000))
+        .await
+        .unwrap()
+        .is_empty());
+
+    // Zero budget ⇒ empty, even with notes present.
+    let store = store_with(&[note("a", "x"), note("b", "y")], fs.clone()).await;
+    let recall = vector_recall(embedder, store, fs);
+    assert!(recall
+        .recall(&root(), &query("a x", 0))
+        .await
+        .unwrap()
+        .is_empty());
+}
+
+#[tokio::test]
+async fn vector_recall_writes_and_reuses_the_derived_cache() {
+    let fs = MemFs::arc();
+    let notes = [note("alpha", "apple"), note("beta", "banana")];
+    let store = store_with(&notes, fs.clone()).await;
+    let spy = Arc::new(SpyEmbedder::new("spy", 128));
+    let recall = VectorMemoryRecall::new(spy.clone(), store, fs.clone());
+
+    // First recall: embeds 2 note texts + 1 query text = 3.
+    let _ = recall.recall(&root(), &query("alpha apple", 100_000)).await.unwrap();
+    let after_first = spy.embedded_texts.load(Ordering::SeqCst);
+    assert_eq!(after_first, 3, "2 notes + 1 query embedded on a cold cache");
+
+    // The derived cache file now exists with both slugs and the embedder id.
+    let doc = fs.raw(VECTORS_PATH).expect("vectors.json written");
+    assert!(doc.contains("\"embedderId\": \"spy\""), "tagged with embedder id: {doc}");
+    assert!(doc.contains("\"alpha\""), "alpha vector cached: {doc}");
+    assert!(doc.contains("\"beta\""), "beta vector cached: {doc}");
+
+    // Second recall: note vectors come from the cache; only the query is embedded.
+    let _ = recall.recall(&root(), &query("beta banana", 100_000)).await.unwrap();
+    let delta = spy.embedded_texts.load(Ordering::SeqCst) - after_first;
+    assert_eq!(delta, 1, "cache reuse ⇒ only the query is re-embedded, got {delta}");
+}
+
+#[tokio::test]
+async fn vector_recall_invalidates_cache_on_embedder_id_change() {
+    let fs = MemFs::arc();
+    let notes = [note("alpha", "apple"), note("beta", "banana")];
+    let store = store_with(&notes, fs.clone()).await;
+
+    // Warm the cache with embedder "first".
+    let first = Arc::new(SpyEmbedder::new("first", 128));
+    VectorMemoryRecall::new(first.clone(), store.clone(), fs.clone())
+        .recall(&root(), &query("alpha apple", 100_000))
+        .await
+        .unwrap();
+    assert!(fs.raw(VECTORS_PATH).unwrap().contains("\"embedderId\": \"first\""));
+
+    // A different embedder id must invalidate ⇒ recompute all note vectors.
+    let second = Arc::new(SpyEmbedder::new("second", 128));
+    VectorMemoryRecall::new(second.clone(), store, fs.clone())
+        .recall(&root(), &query("beta banana", 100_000))
+        .await
+        .unwrap();
+    // 2 notes recomputed + 1 query embedded against the new embedder.
+    assert_eq!(
+        second.embedded_texts.load(Ordering::SeqCst),
+        3,
+        "id change must invalidate and recompute note vectors"
+    );
+    // The file is now tagged with the new embedder id.
+    assert!(fs.raw(VECTORS_PATH).unwrap().contains("\"embedderId\": \"second\""));
+}
+
+#[tokio::test]
+async fn vector_recall_invalidates_cache_on_dimension_change() {
+    let fs = MemFs::arc();
+    let notes = [note("alpha", "apple"), note("beta", "banana")];
+    let store = store_with(&notes, fs.clone()).await;
+
+    // Warm the cache at dimension 64.
+    let dim64 = Arc::new(SpyEmbedder::new("same-id", 64));
+    VectorMemoryRecall::new(dim64, store.clone(), fs.clone())
+        .recall(&root(), &query("alpha apple", 100_000))
+        .await
+        .unwrap();
+
+    // Same id, different dimension ⇒ invalidation, all note vectors recomputed.
+    let dim128 = Arc::new(SpyEmbedder::new("same-id", 128));
+    VectorMemoryRecall::new(dim128.clone(), store, fs.clone())
+        .recall(&root(), &query("beta banana", 100_000))
+        .await
+        .unwrap();
+    assert_eq!(
+        dim128.embedded_texts.load(Ordering::SeqCst),
+        3,
+        "dimension change must invalidate and recompute"
+    );
+    assert!(fs.raw(VECTORS_PATH).unwrap().contains("\"dimension\": 128"));
+}
+
+#[tokio::test]
+async fn vector_recall_with_stub_embedder_errors_without_panic() {
+    // The vector recall surfaces the embedder error as a MemoryError (the Adaptive
+    // switch turns that into a naïve fallback — covered below). Here we just pin
+    // that StubEmbedder is best-effort: an Err, never a panic.
+    let fs = MemFs::arc();
+    let store = store_with(&[note("alpha", "apple")], fs.clone()).await;
+    let stub = Arc::new(StubEmbedder::new("stub", 64, "localOnnx"));
+    let recall = VectorMemoryRecall::new(stub, store, fs);
+    let res = recall.recall(&root(), &query("alpha apple", 1000)).await;
+    assert!(res.is_err(), "stub embedder ⇒ Err on the vector path, got {res:?}");
+}
+
+// ===========================================================================
+// 6. AdaptiveMemoryRecall — the étage-1/étage-2 switch.
+// ===========================================================================
+
+/// Assembles an [`AdaptiveMemoryRecall`] over `notes` for the given strategy and
+/// embedder, sharing one in-memory fs / store.
+async fn adaptive_over(
+    notes: &[Memory],
+    strategy: EmbedderStrategy,
+    embedder: Arc<dyn Embedder>,
+) -> (Arc<MemFs>, AdaptiveMemoryRecall) {
+    let fs = MemFs::arc();
+    let store = store_with(notes, fs.clone()).await;
+    let naive: Arc<dyn MemoryRecall> = Arc::new(NaiveMemoryRecall::new(store.clone()));
+    let vector: Arc<dyn MemoryRecall> =
+        Arc::new(VectorMemoryRecall::new(embedder, store.clone(), fs.clone()));
+    let adaptive = AdaptiveMemoryRecall::new(naive, vector, store, strategy);
+    (fs, adaptive)
+}
+
+#[tokio::test]
+async fn adaptive_none_strategy_matches_naive_exactly() {
+    let notes = [
+        note("alpha", "apple orange grape"),
+        note("beta", "kiwi mango papaya"),
+        note("gamma", "carrot potato onion"),
+    ];
+    let fs = MemFs::arc();
+    let store = store_with(&notes, fs.clone()).await;
+    let naive = NaiveMemoryRecall::new(store.clone());
+
+    // Adaptive with strategy `none` (embedder present but never used).
+    let naive_dyn: Arc<dyn MemoryRecall> = Arc::new(NaiveMemoryRecall::new(store.clone()));
+    let vector_dyn: Arc<dyn MemoryRecall> = Arc::new(VectorMemoryRecall::new(
+        Arc::new(HashEmbedder::new("hash", 64)),
+        store.clone(),
+        fs.clone(),
+    ));
+    let adaptive = AdaptiveMemoryRecall::new(naive_dyn, vector_dyn, store, EmbedderStrategy::None);
+
+    // For several budgets, adaptive(none) == naive, byte-for-byte.
+    for budget in [0usize, 3, 6, 100, 100_000] {
+        let q = query("kiwi mango papaya", budget);
+        let expected = naive.recall(&root(), &q).await.unwrap();
+        let got = adaptive.recall(&root(), &q).await.unwrap();
+        assert_eq!(got, expected, "strategy none must equal naive at budget {budget}");
+    }
+}
+
+#[tokio::test]
+async fn adaptive_small_memory_routes_to_naive_order() {
+    // Memory smaller than the budget ⇒ naïve path ⇒ index order, even with a
+    // non-none strategy. The query would, on the vector path, reorder by
+    // similarity; index order proves naïve was used.
+    let notes = [
+        note("alpha", "apple"),
+        note("beta", "banana"),
+        note("gamma", "grape"),
+    ];
+    let (_fs, adaptive) = adaptive_over(
+        &notes,
+        EmbedderStrategy::LocalServer,
+        Arc::new(HashEmbedder::new("hash", 256)),
+    )
+    .await;
+
+    // Huge budget ⇒ memory_size <= budget ⇒ naïve ⇒ index order alpha,beta,gamma.
+    let out = adaptive
+        .recall(&root(), &query("gamma grape", 100_000))
+        .await
+        .unwrap();
+    assert_eq!(slugs(&out), vec!["alpha", "beta", "gamma"], "naïve keeps index order");
+}
+
+#[tokio::test]
+async fn adaptive_large_memory_routes_to_vector_ranking() {
+    // Memory larger than the budget + non-none strategy ⇒ vector path ⇒ the note
+    // closest to the query ranks first (not index order).
+    let notes = [
+        note("alpha", "apple orange grape"),
+        note("beta", "kiwi mango papaya"),
+        note("gamma", "carrot potato onion"),
+    ];
+    let (_fs, adaptive) = adaptive_over(
+        &notes,
+        EmbedderStrategy::LocalOnnx,
+        Arc::new(HashEmbedder::new("hash", 256)),
+    )
+    .await;
+
+    // Budget smaller than the total memory size forces the vector route; the query
+    // matches `gamma`, so `gamma` must be first (≠ index order, where it is last).
+    let total = {
+        let store = FsMemoryStore::new(MemFs::arc());
+        for n in &notes {
+            store.save(&root(), n).await.unwrap();
+        }
+        infrastructure::index_token_size(&store.read_index(&root()).await.unwrap())
+    };
+    assert!(total > 4, "sanity: memory must exceed the chosen budget");
+
+    let out = adaptive
+        .recall(&root(), &query("carrot potato onion", total - 1))
+        .await
+        .unwrap();
+    assert_eq!(
+        out.first().map(|e| e.slug.as_str()),
+        Some("gamma"),
+        "vector path ranks the closest note first: {:?}",
+        slugs(&out)
+    );
+}
+
+#[tokio::test]
+async fn adaptive_falls_back_to_naive_when_embedder_fails() {
+    // Large memory + non-none strategy routes to the vector path; with a
+    // StubEmbedder that path errors, and Adaptive must degrade to naïve — never a
+    // hard error. Result therefore equals the naïve recall (index order, truncated).
+    let notes = [
+        note("alpha", "apple orange grape"),
+        note("beta", "kiwi mango papaya"),
+        note("gamma", "carrot potato onion"),
+    ];
+    let fs = MemFs::arc();
+    let store = store_with(&notes, fs.clone()).await;
+    let naive_ref = NaiveMemoryRecall::new(store.clone());
+
+    let naive_dyn: Arc<dyn MemoryRecall> = Arc::new(NaiveMemoryRecall::new(store.clone()));
+    let vector_dyn: Arc<dyn MemoryRecall> = Arc::new(VectorMemoryRecall::new(
+        Arc::new(StubEmbedder::new("stub", 64, "localOnnx")),
+        store.clone(),
+        fs.clone(),
+    ));
+    let adaptive =
+        AdaptiveMemoryRecall::new(naive_dyn, vector_dyn, store.clone(), EmbedderStrategy::Api);
+
+    let total = infrastructure::index_token_size(&store.read_index(&root()).await.unwrap());
+    let q = query("carrot potato onion", total - 1);
+
+    let got = adaptive.recall(&root(), &q).await.expect("fallback must not error");
+    let expected = naive_ref.recall(&root(), &q).await.unwrap();
+    assert_eq!(got, expected, "embedder failure must degrade to the naïve result");
+    assert!(!got.is_empty(), "the degraded result still returns entries");
+}
+
+#[tokio::test]
+async fn adaptive_empty_memory_and_zero_budget_are_empty() {
+    // Liskov common contract: empty list, never an error, both paths.
+    let fs = MemFs::arc();
+    let empty_store = Arc::new(FsMemoryStore::new(fs.clone()));
+    let naive: Arc<dyn MemoryRecall> = Arc::new(NaiveMemoryRecall::new(empty_store.clone()));
+    let vector: Arc<dyn MemoryRecall> = Arc::new(VectorMemoryRecall::new(
+        Arc::new(HashEmbedder::new("hash", 64)),
+        empty_store.clone(),
+        fs.clone(),
+    ));
+    let adaptive =
+        AdaptiveMemoryRecall::new(naive, vector, empty_store, EmbedderStrategy::LocalOnnx);
+
+    // Empty memory.
+    assert!(adaptive
+        .recall(&root(), &query("anything", 1000))
+        .await
+        .unwrap()
+        .is_empty());
+    // Zero budget.
+    assert!(adaptive
+        .recall(&root(), &query("anything", 0))
+        .await
+        .unwrap()
+        .is_empty());
+}