fix: fix some displays and features

.gitignore

@@ -24,6 +24,9 @@ frontend/coverage/
 # ─── Claude Code ────────────────────────────────────────────────────────────
 # Personal, machine-local overrides (shared settings.json, if any, stays tracked).
 .claude/settings.local.json
+# Ephemeral git worktrees created by Claude Code's isolated sub-agents — dev
+# tooling only, unrelated to IdeA (which stays git-independent).
+.claude/worktrees/
 
 # ─── IdeA project data ──────────────────────────────────────────────────────
 # Ephemeral per-agent run directories (isolated PTY cwd + generated convention

.ideai/layouts.json

@@ -18,6 +18,7 @@
                   "type": "leaf",
                   "node": {
                     "id": "d8a86eb1-cd4d-4937-b900-4989da7c868d",
+                    "session": "2e6293fe-250a-4654-a8b2-4fe6996f8288",
                     "agent": "a6ced819-b893-4213-b003-9e9dc79b9641"
                   }
                 },
@@ -27,7 +28,8 @@
                 "node": {
                   "type": "leaf",
                   "node": {
-                    "id": "6c5be5e7-a54b-468c-a2e2-8ec853629d5e"
+                    "id": "6c5be5e7-a54b-468c-a2e2-8ec853629d5e",
+                    "session": "9aa5859c-5868-46b3-a045-68cbea6eb629"
                   }
                 },
                 "weight": 1.0

agents-dev/L12-skills.md

@@ -35,8 +35,31 @@ Modéliser les **Skills** : workflows réutilisables (équivalent universel des
 - **`Agent`** étendu : champ `skills: Vec<SkillRef>` (serde `default`), méthodes `assign_skill` (idempotent), `unassign_skill`, `with_skills` (dédup). **`ManifestEntry`** : champ `skills` (serde `default` + `skip_serializing_if` → rétrocompat des manifests pré-L12) ; `from_agent`/`to_agent` préservent les skills.
 - **Tests** : 8 invariants (`entities.rs`) + 3 serde dont rétrocompat d'un manifest legacy sans clé `skills` (`serde_roundtrip.rs`). `cargo test -p domain` vert ; `cargo test --workspace` vert (0 régression) ; clippy clean.
 
+### ✅ Port + adapter store (vert)
+- **Port `SkillStore`** (`domain/ports.rs`) : `list/get/save/delete` portant `scope` + `root: &ProjectPath` **par appel** (root ignoré pour `Global`, résolu pour `Project`) — un seul store sert tous les projets ouverts, comme `AgentContextStore`.
+- **Adapter `FsSkillStore`** (`infrastructure/store/skill.rs`) : même forme on-disk que `FsTemplateStore` (`index.json` + `md/<id>.md`), deux racines disjointes : `<app_data>/skills/` (Global) et `<root>/.ideai/skills/` (Project). Delete laisse l'orphelin md (pas de remove dans le port FS), index = source de vérité. **7 tests** d'intégration tmpdir (`skill_store.rs`) : round-trip 2 scopes, **isolation de scope**, upsert, delete idempotent, camelCase.
+
+### ✅ Use cases application (vert)
+- `application/skill` : `CreateSkill`, `UpdateSkill`, `DeleteSkill`, `ListSkills(scope)` (inputs portant `project_root`), `AssignSkillToAgent` / `UnassignSkillFromAgent` (mutent l'`AgentManifest` via `to_agent`/`from_agent`, dédup, émettent `SkillAssigned`, **idempotents**). **9 tests** (`skill_usecases.rs`).
+
+### ✅ Injection dans le convention file (vert, fil L6)
+- `LaunchAgent` reçoit le port `SkillStore` ; `resolve_skills` lit les `.md` des skills assignés (ordre manifest, déterministe ; skill supprimé = `SkillRef` pendant → ignoré sans bloquer le lancement).
+- `compose_convention_file` étendu : section `# Skills` (sous-titres `## <name>`) après le persona ; omise si aucun skill. **3 tests** unitaires + e2e (`agent_lifecycle.rs` : injection ordonnée, ref pendant tolérée).
+- **Composition root** (`app-tauri/state.rs`) : `FsSkillStore` construit (app-data global), injecté dans `LaunchAgent`.
+
+### ✅ IPC `app-tauri` (vert)
+- **DTOs** (`dto.rs`) : `SkillDto` (transparent sur `Skill`, camelCase), `SkillListDto`, request DTOs (`Create/Update/Assign/UnassignSkillRequestDto`), `parse_skill_id`. `scope` désérialise directement vers `SkillScope` (`"global"`/`"project"`).
+- **Commandes** (`commands.rs`) : `create_skill`, `update_skill`, `list_skills`, `delete_skill`, `assign_skill_to_agent`, `unassign_skill_from_agent` — shells fins qui résolvent le `Project` (→ `project.root`) puis appellent le use case. Enregistrées dans `lib.rs`.
+- **Composition root** (`state.rs`) : 6 use cases skill câblés sur le `skill_store_port` (déjà construit pour le launcher) et le `contexts_port` partagé.
+- `cargo build -p app-tauri` + `cargo test --workspace` (304) verts ; clippy clean.
+
+### ✅ Front `features/skills` (vert)
+- **Domaine** (`domain/index.ts`) : `SkillScope`, `Skill`, `SkillRef` ; `Agent` étendu avec `skills: SkillRef[]`.
+- **Port** (`ports/index.ts`) : `SkillGateway` (list/create/update/delete + assign/unassign) + `CreateSkillInput` ; ajouté à `Gateways`.
+- **Adapters** : `TauriSkillGateway` (`adapters/skill.ts`, invoke camelCase) ; `MockSkillGateway` (`adapters/mock`, scopes disjoints + mutation partagée du `MockAgentGateway` via `_setSkills`, assign idempotent).
+- **Feature** : `useSkills` (VM 2 scopes), `SkillEditor` (overlay md edit/preview + sélecteur de scope), `SkillsPanel` (listes Project/Global, CRUD). Onglet **Skills** ajouté dans `ProjectsView`.
+- **Assignation** dans `AgentsPanel` : chips des skills assignés + sélecteur d'assignation + unassign, sur l'agent sélectionné ; refresh après mutation.
+- **Tests** (`skills.test.tsx`, RTL via `DIProvider` + mocks) : CRUD project/global, isolation de scope, édition, suppression, assign/unassign reflétés sur l'agent, idempotence, **garde-fou « no direct invoke »** (aucune action run/launch). `vitest` : **229** verts (0 régression ; test « ten gateways » mis à jour).
+
 ### ⏳ Reste à faire
-- Port `SkillStore` (`domain/ports.rs`) + adapter `FsSkillStore` (`infrastructure/store`).
-- Use cases `application/skill` : CRUD + `AssignSkillToAgent`/`UnassignSkillFromAgent`.
-- Injection des skills assignés dans le convention file à l'activation (fil L6).
-- IPC `app-tauri` + front `features/skills`.
+- Cycle manuel : créer un skill, l'assigner à un agent, l'activer → vérifier qu'il apparaît dans le convention file de `.ideai/run/<agent-id>/` (à faire sur l'AppImage).

crates/app-tauri/src/commands.rs

@@ -14,6 +14,8 @@ use application::{
     GitStatusInput, LaunchAgentInput, ListAgentsInput, ListLayoutsInput, LoadLayoutInput,
     MutateLayoutInput, OpenProjectInput, ReadAgentContextInput, RenameLayoutInput,
     SetActiveLayoutInput, SyncAgentWithTemplateInput, UpdateAgentContextInput,
+    AssignSkillToAgentInput, CreateSkillInput, DeleteSkillInput, ListSkillsInput,
+    UnassignSkillFromAgentInput, UpdateSkillInput,
 };
 use domain::ports::PtyHandle;
 
@@ -31,8 +33,10 @@ use crate::dto::{
     ReattachResultDto, RenameLayoutRequestDto, ResizeTerminalRequestDto, SaveProfileRequestDto,
     SetActiveLayoutRequestDto, SyncAgentWithTemplateRequestDto, SyncResultDto, TemplateDto,
     TemplateListDto, TerminalClosedDto, TerminalSessionDto, UpdateAgentContextRequestDto,
-    UpdateTemplateRequestDto, WriteTerminalRequestDto,
+    UpdateTemplateRequestDto, WriteTerminalRequestDto, parse_skill_id, AssignSkillRequestDto,
+    CreateSkillRequestDto, SkillDto, SkillListDto, UnassignSkillRequestDto, UpdateSkillRequestDto,
 };
+use domain::{SkillRef, SkillScope};
 use crate::pty::{PtyBridge, PtyChunk};
 use crate::state::AppState;
 
@@ -1182,3 +1186,157 @@ pub async fn move_tab_to_new_window(
 
     Ok(MoveTabResultDto::from(out))
 }
+
+// ---------------------------------------------------------------------------
+// Skills (L12)
+// ---------------------------------------------------------------------------
+
+/// `create_skill` — create a skill in its scope's store.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for an empty name/content or malformed
+/// project id, `NOT_FOUND` if the project is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn create_skill(
+    request: CreateSkillRequestDto,
+    state: State<'_, AppState>,
+) -> Result<SkillDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    state
+        .create_skill
+        .execute(CreateSkillInput {
+            name: request.name,
+            content: request.content,
+            scope: request.scope,
+            project_root: project.root,
+        })
+        .await
+        .map(SkillDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `update_skill` — replace a skill's Markdown content.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for malformed ids or empty content,
+/// `NOT_FOUND` if the project or skill is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn update_skill(
+    request: UpdateSkillRequestDto,
+    state: State<'_, AppState>,
+) -> Result<SkillDto, ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    let skill_id = parse_skill_id(&request.skill_id)?;
+    state
+        .update_skill
+        .execute(UpdateSkillInput {
+            scope: request.scope,
+            skill_id,
+            content: request.content,
+            project_root: project.root,
+        })
+        .await
+        .map(SkillDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `list_skills` — list the skills in one scope.
+///
+/// # 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_skills(
+    project_id: String,
+    scope: SkillScope,
+    state: State<'_, AppState>,
+) -> Result<SkillListDto, ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    state
+        .list_skills
+        .execute(ListSkillsInput {
+            scope,
+            project_root: project.root,
+        })
+        .await
+        .map(SkillListDto::from)
+        .map_err(ErrorDto::from)
+}
+
+/// `delete_skill` — remove a skill from its scope's store.
+///
+/// Agents that referenced it keep their `SkillRef`; injection simply skips the
+/// now-absent skill.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for malformed ids, `NOT_FOUND` if the
+/// project or skill is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn delete_skill(
+    project_id: String,
+    scope: SkillScope,
+    skill_id: String,
+    state: State<'_, AppState>,
+) -> Result<(), ErrorDto> {
+    let project = resolve_project(&project_id, &state).await?;
+    let id = parse_skill_id(&skill_id)?;
+    state
+        .delete_skill
+        .execute(DeleteSkillInput {
+            scope,
+            skill_id: id,
+            project_root: project.root,
+        })
+        .await
+        .map_err(ErrorDto::from)
+}
+
+/// `assign_skill_to_agent` — record a `SkillRef` in the agent's manifest entry.
+/// Idempotent.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for malformed ids, `NOT_FOUND` if the
+/// project or agent is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn assign_skill_to_agent(
+    request: AssignSkillRequestDto,
+    state: State<'_, AppState>,
+) -> Result<(), ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    let agent_id = parse_agent_id(&request.agent_id)?;
+    let skill_id = parse_skill_id(&request.skill_id)?;
+    state
+        .assign_skill
+        .execute(AssignSkillToAgentInput {
+            project,
+            agent_id,
+            skill: SkillRef::new(skill_id, request.scope),
+        })
+        .await
+        .map_err(ErrorDto::from)
+}
+
+/// `unassign_skill_from_agent` — drop a skill assignment from an agent.
+/// Idempotent.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for malformed ids, `NOT_FOUND` if the
+/// project or agent is unknown, `STORE` on failure).
+#[tauri::command]
+pub async fn unassign_skill_from_agent(
+    request: UnassignSkillRequestDto,
+    state: State<'_, AppState>,
+) -> Result<(), ErrorDto> {
+    let project = resolve_project(&request.project_id, &state).await?;
+    let agent_id = parse_agent_id(&request.agent_id)?;
+    let skill_id = parse_skill_id(&request.skill_id)?;
+    state
+        .unassign_skill
+        .execute(UnassignSkillFromAgentInput {
+            project,
+            agent_id,
+            skill_id,
+        })
+        .await
+        .map_err(ErrorDto::from)
+}

crates/app-tauri/src/dto.rs

@@ -1342,3 +1342,107 @@ pub fn parse_tab_id(raw: &str) -> Result<TabId, ErrorDto> {
             message: format!("invalid tab id: {raw}"),
         })
 }
+
+// ---------------------------------------------------------------------------
+// Skills (L12)
+// ---------------------------------------------------------------------------
+
+use application::{CreateSkillOutput, ListSkillsOutput, UpdateSkillOutput};
+use domain::{Skill, SkillId, SkillScope};
+
+/// A skill crossing the wire. [`Skill`] already serialises camelCase
+/// (`id`, `name`, `contentMd`, `scope` as `"global"`/`"project"`), so we embed
+/// it directly — the TS mirror matches this shape.
+#[derive(Debug, Clone, Serialize)]
+#[serde(transparent)]
+pub struct SkillDto(pub Skill);
+
+/// A list of skills (transparent array on the wire).
+#[derive(Debug, Clone, Serialize)]
+#[serde(transparent)]
+pub struct SkillListDto(pub Vec<SkillDto>);
+
+impl From<ListSkillsOutput> for SkillListDto {
+    fn from(out: ListSkillsOutput) -> Self {
+        Self(out.skills.into_iter().map(SkillDto).collect())
+    }
+}
+
+impl From<CreateSkillOutput> for SkillDto {
+    fn from(out: CreateSkillOutput) -> Self {
+        Self(out.skill)
+    }
+}
+
+impl From<UpdateSkillOutput> for SkillDto {
+    fn from(out: UpdateSkillOutput) -> Self {
+        Self(out.skill)
+    }
+}
+
+/// Request DTO for `create_skill`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CreateSkillRequestDto {
+    /// Owning project (resolved to a root; ignored on disk for `Global`).
+    pub project_id: String,
+    /// Display name.
+    pub name: String,
+    /// Initial Markdown content.
+    pub content: String,
+    /// Scope the skill is created in.
+    pub scope: SkillScope,
+}
+
+/// Request DTO for `update_skill`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct UpdateSkillRequestDto {
+    /// Owning project (resolved to a root; ignored on disk for `Global`).
+    pub project_id: String,
+    /// Id of the skill to update.
+    pub skill_id: String,
+    /// Scope the skill lives in.
+    pub scope: SkillScope,
+    /// New Markdown content.
+    pub content: String,
+}
+
+/// Request DTO for `assign_skill_to_agent`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct AssignSkillRequestDto {
+    /// Owning project.
+    pub project_id: String,
+    /// Agent receiving the skill.
+    pub agent_id: String,
+    /// Skill to assign.
+    pub skill_id: String,
+    /// Scope of the skill (recorded alongside the ref).
+    pub scope: SkillScope,
+}
+
+/// Request DTO for `unassign_skill_from_agent`.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct UnassignSkillRequestDto {
+    /// Owning project.
+    pub project_id: String,
+    /// Agent losing the skill.
+    pub agent_id: String,
+    /// Skill to unassign.
+    pub skill_id: String,
+}
+
+/// Parses a skill-id string (UUID) coming from the frontend.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] with code `INVALID` if the string is not a UUID.
+pub fn parse_skill_id(raw: &str) -> Result<SkillId, ErrorDto> {
+    uuid::Uuid::parse_str(raw)
+        .map(SkillId::from_uuid)
+        .map_err(|_| ErrorDto {
+            code: "INVALID".to_owned(),
+            message: format!("invalid skill id: {raw}"),
+        })
+}

crates/app-tauri/src/lib.rs

@@ -119,6 +119,12 @@ pub fn run() {
             commands::git_log,
             commands::git_init,
             commands::git_graph,
+            commands::create_skill,
+            commands::update_skill,
+            commands::list_skills,
+            commands::delete_skill,
+            commands::assign_skill_to_agent,
+            commands::unassign_skill_from_agent,
             commands::move_tab_to_new_window,
         ])
         .run(tauri::generate_context!())

crates/app-tauri/src/state.rs

@@ -13,18 +13,19 @@ use application::{
     CreateAgentFromTemplate, CreateLayout, CreateProject, CreateTemplate, DeleteAgent,
     DeleteLayout, DeleteProfile, DeleteTemplate, DetectAgentDrift, DetectProfiles, FirstRunState,
     GitBranches, GitCheckout, GitCommit, GitGraph, GitInit, GitLog, GitStage, GitStatus, GitUnstage,
-    HealthUseCase, LaunchAgent, ListAgents, ListLayouts, ListProfiles, ListProjects, ListTemplates,
-    LoadLayout, MoveTabToNewWindow, MutateLayout, OpenProject, OpenTerminal, ReadAgentContext,
-    ReferenceProfiles, RenameLayout, ResizeTerminal, SaveProfile, SetActiveLayout,
+    HealthUseCase, LaunchAgent, ListAgents, ListLayouts, ListProfiles, ListProjects, ListSkills,
+    ListTemplates, LoadLayout, MoveTabToNewWindow, MutateLayout, OpenProject, OpenTerminal,
+    ReadAgentContext, ReferenceProfiles, RenameLayout, ResizeTerminal, SaveProfile, SetActiveLayout,
+    AssignSkillToAgent, CreateSkill, DeleteSkill, UnassignSkillFromAgent, UpdateSkill,
     SyncAgentWithTemplate, TerminalSessions, UpdateAgentContext, UpdateTemplate, WriteToTerminal,
 };
 use domain::ports::{
     AgentContextStore, AgentRuntime, Clock, EventBus, FileSystem, GitPort, IdGenerator,
-    ProcessSpawner, ProfileStore, ProjectStore, PtyPort, TemplateStore,
+    ProcessSpawner, ProfileStore, ProjectStore, PtyPort, SkillStore, TemplateStore,
 };
 
 use infrastructure::{
-    CliAgentRuntime, FsProfileStore, FsProjectStore, FsTemplateStore, Git2Repository,
+    CliAgentRuntime, FsProfileStore, FsProjectStore, FsSkillStore, FsTemplateStore, Git2Repository,
     IdeaiContextStore, LocalFileSystem, LocalProcessSpawner, PortablePtyAdapter, SystemClock,
     TokioBroadcastEventBus, UuidGenerator,
 };
@@ -147,6 +148,19 @@ pub struct AppState {
     pub git_init: Arc<GitInit>,
     /// Return the commit graph for all local branches.
     pub git_graph: Arc<GitGraph>,
+    // --- Skills (L12) ---
+    /// Create a skill in a scope's store.
+    pub create_skill: Arc<CreateSkill>,
+    /// Update a skill's content.
+    pub update_skill: Arc<UpdateSkill>,
+    /// List skills in a scope.
+    pub list_skills: Arc<ListSkills>,
+    /// Delete a skill from its scope's store.
+    pub delete_skill: Arc<DeleteSkill>,
+    /// Assign a skill to an agent (records a `SkillRef`).
+    pub assign_skill: Arc<AssignSkillToAgent>,
+    /// Unassign a skill from an agent.
+    pub unassign_skill: Arc<UnassignSkillFromAgent>,
 }
 
 impl AppState {
@@ -287,6 +301,17 @@ impl AppState {
         let contexts = Arc::new(IdeaiContextStore::new(Arc::clone(&fs_port)));
         let contexts_port = Arc::clone(&contexts) as Arc<dyn AgentContextStore>;
 
+        // --- Skill store (L12) ---
+        // Global skills live in the machine-local app-data dir; project skills are
+        // resolved per call from each project's `.ideai/` (so one store serves all
+        // open projects). Shared by the skill use cases and the agent launcher
+        // (assigned-skill injection into the convention file, §14.2).
+        let skill_store = Arc::new(FsSkillStore::new(
+            Arc::clone(&fs_port),
+            app_data_dir.to_string_lossy().into_owned(),
+        ));
+        let skill_store_port = Arc::clone(&skill_store) as Arc<dyn SkillStore>;
+
         let create_agent = Arc::new(CreateAgentFromScratch::new(
             Arc::clone(&contexts_port),
             Arc::clone(&ids) as Arc<dyn IdGenerator>,
@@ -307,6 +332,7 @@ impl AppState {
             Arc::clone(&runtime_port),
             Arc::clone(&fs_port),
             Arc::clone(&pty_port),
+            Arc::clone(&skill_store_port),
             Arc::clone(&terminal_sessions),
             Arc::clone(&events_port),
         ));
@@ -364,6 +390,25 @@ impl AppState {
         let git_init = Arc::new(GitInit::new(Arc::clone(&git_port), Arc::clone(&events_port)));
         let git_graph = Arc::new(GitGraph::new(Arc::clone(&git_port)));
 
+        // --- Skill use cases (L12) ---
+        // Reuse the skill store (built above for the launcher) and the shared
+        // agent context store for the agent↔skill assignment.
+        let create_skill = Arc::new(CreateSkill::new(
+            Arc::clone(&skill_store_port),
+            Arc::clone(&ids) as Arc<dyn IdGenerator>,
+        ));
+        let update_skill = Arc::new(UpdateSkill::new(Arc::clone(&skill_store_port)));
+        let list_skills = Arc::new(ListSkills::new(Arc::clone(&skill_store_port)));
+        let delete_skill = Arc::new(DeleteSkill::new(Arc::clone(&skill_store_port)));
+        let assign_skill = Arc::new(AssignSkillToAgent::new(
+            Arc::clone(&contexts_port),
+            Arc::clone(&events_port),
+        ));
+        let unassign_skill = Arc::new(UnassignSkillFromAgent::new(
+            Arc::clone(&contexts_port),
+            Arc::clone(&events_port),
+        ));
+
         // --- Windows (L10) ---
         let move_tab = Arc::new(MoveTabToNewWindow::new(
             Arc::clone(&store_port),
@@ -422,6 +467,12 @@ impl AppState {
             git_log,
             git_init,
             git_graph,
+            create_skill,
+            update_skill,
+            list_skills,
+            delete_skill,
+            assign_skill,
+            unassign_skill,
             move_tab,
         }
     }

crates/application/src/agent/lifecycle.rs

@@ -15,11 +15,11 @@ use std::sync::Arc;
 
 use domain::ports::{
     AgentContextStore, AgentRuntime, ContextInjectionPlan, EventBus, FileSystem, PreparedContext,
-    ProfileStore, PtyPort, RemotePath, SpawnSpec,
+    ProfileStore, PtyPort, RemotePath, SkillStore, SpawnSpec, StoreError,
 };
 use domain::{
     Agent, AgentId, AgentManifest, AgentOrigin, DomainEvent, ManifestEntry, MarkdownDoc, NodeId,
-    Project, ProfileId, ProjectPath, PtySize, SessionKind, SessionStatus, TerminalSession,
+    Project, ProfileId, ProjectPath, PtySize, SessionKind, SessionStatus, Skill, TerminalSession,
 };
 
 use crate::error::AppError;
@@ -350,6 +350,7 @@ pub struct LaunchAgent {
     runtime: Arc<dyn AgentRuntime>,
     fs: Arc<dyn FileSystem>,
     pty: Arc<dyn PtyPort>,
+    skills: Arc<dyn SkillStore>,
     sessions: Arc<TerminalSessions>,
     events: Arc<dyn EventBus>,
 }
@@ -364,6 +365,7 @@ impl LaunchAgent {
         runtime: Arc<dyn AgentRuntime>,
         fs: Arc<dyn FileSystem>,
         pty: Arc<dyn PtyPort>,
+        skills: Arc<dyn SkillStore>,
         sessions: Arc<TerminalSessions>,
         events: Arc<dyn EventBus>,
     ) -> Self {
@@ -373,11 +375,35 @@ impl LaunchAgent {
             runtime,
             fs,
             pty,
+            skills,
             sessions,
             events,
         }
     }
 
+    /// Resolves the Markdown bodies of an agent's assigned skills, in the
+    /// **manifest order** (deterministic). A skill that no longer exists in its
+    /// store (deleted out from under the assignment) is silently skipped — a
+    /// dangling [`domain::SkillRef`] must not block a launch.
+    ///
+    /// # Errors
+    /// [`AppError::Store`] on any store failure other than a missing skill.
+    async fn resolve_skills(
+        &self,
+        agent: &Agent,
+        root: &ProjectPath,
+    ) -> Result<Vec<Skill>, AppError> {
+        let mut out = Vec::with_capacity(agent.skills.len());
+        for skill_ref in &agent.skills {
+            match self.skills.get(skill_ref.scope, root, skill_ref.skill_id).await {
+                Ok(skill) => out.push(skill),
+                Err(StoreError::NotFound) => {}
+                Err(e) => return Err(e.into()),
+            }
+        }
+        Ok(out)
+    }
+
     /// Executes the launch.
     ///
     /// Step order is contractually significant (and unit-tested): resolve the
@@ -444,8 +470,10 @@ impl LaunchAgent {
             .runtime
             .prepare_invocation(&profile, &prepared, &run_dir)?;
 
-        // 5. Apply the injection plan side effects *before* spawning.
-        self.apply_injection(&input.project, &agent.context_path, &content, &mut spec)
+        // 5. Resolve the agent's assigned skills (their `.md` bodies), then apply
+        //    the injection plan side effects *before* spawning.
+        let skills = self.resolve_skills(&agent, &input.project.root).await?;
+        self.apply_injection(&input.project, &agent.context_path, &content, &skills, &mut spec)
             .await?;
 
         // 6. Spawn the PTY at the resolved cwd; adopt its session id everywhere.
@@ -487,6 +515,7 @@ impl LaunchAgent {
         project: &Project,
         context_rel_path: &str,
         content: &MarkdownDoc,
+        skills: &[Skill],
         spec: &mut SpawnSpec,
     ) -> Result<(), AppError> {
         match spec.context_plan.clone() {
@@ -496,9 +525,10 @@ impl LaunchAgent {
                 // run directory — `spec.cwd` is that run dir, never the project
                 // root, so there is zero collision between agents. The document is
                 // composed: an absolute project-root header (so the agent knows
-                // where to operate, since its cwd is *not* the root) followed by
-                // the agent's persona `.md`.
-                let document = compose_convention_file(project.root.as_str(), content.as_str());
+                // where to operate, since its cwd is *not* the root), the agent's
+                // persona `.md`, then the bodies of its assigned skills (§14.2).
+                let document =
+                    compose_convention_file(project.root.as_str(), content.as_str(), skills);
                 let path = RemotePath::new(join(&spec.cwd, &target));
                 self.fs.write(&path, document.as_bytes()).await?;
             }
@@ -537,13 +567,17 @@ fn agent_run_dir(root: &ProjectPath, agent_id: &AgentId) -> Result<ProjectPath,
 
 /// Composes the convention file IdeA writes into an agent's run directory: an
 /// absolute project-root header (the agent's cwd is the run dir, *not* the root,
-/// so it must be told where to work) followed by the agent's persona `.md`.
+/// so it must be told where to work), the agent's persona `.md`, then the bodies
+/// of its assigned `skills` under a `# Skills` section (ARCHITECTURE §14.2).
 ///
-/// Kept as a **pure** function (no I/O) so it is unit-testable in isolation, and
-/// deliberately structured so future blocks (assigned skills, shared project
-/// context — ARCHITECTURE §14.2) can be appended without touching the launcher.
+/// Skills are emitted in the order given (the caller passes them in manifest
+/// order, making the output deterministic); each is introduced by a `##` header
+/// carrying its name. When `skills` is empty the section is omitted entirely, so
+/// an agent with no skills gets exactly the previous document.
+///
+/// Kept as a **pure** function (no I/O) so it is unit-testable in isolation.
 #[must_use]
-pub(crate) fn compose_convention_file(project_root: &str, agent_md: &str) -> String {
+pub(crate) fn compose_convention_file(project_root: &str, agent_md: &str, skills: &[Skill]) -> String {
     let mut out = String::new();
     out.push_str("# Project root\n\n");
     out.push_str(project_root);
@@ -554,6 +588,17 @@ pub(crate) fn compose_convention_file(project_root: &str, agent_md: &str) -> Str
     );
     out.push_str("---\n\n");
     out.push_str(agent_md);
+
+    if !skills.is_empty() {
+        out.push_str("\n\n---\n\n# Skills\n");
+        for skill in skills {
+            out.push_str("\n## ");
+            out.push_str(&skill.name);
+            out.push_str("\n\n");
+            out.push_str(skill.content_md.as_str());
+            out.push('\n');
+        }
+    }
     out
 }
 
@@ -610,7 +655,7 @@ mod tests {
 
     #[test]
     fn compose_convention_file_carries_root_then_persona() {
-        let doc = compose_convention_file("/abs/project/root", "# Persona\n\nDo things.");
+        let doc = compose_convention_file("/abs/project/root", "# Persona\n\nDo things.", &[]);
 
         // Absolute project root present.
         assert!(doc.contains("/abs/project/root"));
@@ -621,5 +666,38 @@ mod tests {
         let root_at = doc.find("/abs/project/root").unwrap();
         let persona_at = doc.find("# Persona").unwrap();
         assert!(root_at < persona_at, "root header must precede the persona");
+        // No skills ⇒ no Skills section.
+        assert!(!doc.contains("# Skills"));
+    }
+
+    #[test]
+    fn compose_convention_file_appends_assigned_skills_in_order() {
+        let s = |n: u128, name: &str, body: &str| {
+            Skill::new(
+                domain::SkillId::from_uuid(uuid::Uuid::from_u128(n)),
+                name,
+                MarkdownDoc::new(body),
+                domain::SkillScope::Global,
+            )
+            .unwrap()
+        };
+        let doc = compose_convention_file(
+            "/root",
+            "# Persona",
+            &[s(1, "refactor", "REFAC_BODY"), s(2, "review", "REVIEW_BODY")],
+        );
+
+        // Both skill bodies present, after the persona.
+        assert!(doc.contains("REFAC_BODY"));
+        assert!(doc.contains("REVIEW_BODY"));
+        let persona_at = doc.find("# Persona").unwrap();
+        let refac_at = doc.find("REFAC_BODY").unwrap();
+        let review_at = doc.find("REVIEW_BODY").unwrap();
+        assert!(persona_at < refac_at, "skills come after the persona");
+        // Deterministic order: first assigned skill precedes the second.
+        assert!(refac_at < review_at, "skills emitted in the given order");
+        // Skill names surface as sub-headers.
+        assert!(doc.contains("## refactor"));
+        assert!(doc.contains("## review"));
     }
 }

crates/application/src/lib.rs

@@ -18,6 +18,7 @@ pub mod health;
 pub mod layout;
 pub mod project;
 pub mod remote;
+pub mod skill;
 pub mod template;
 pub mod terminal;
 pub mod window;
@@ -61,6 +62,12 @@ pub use template::{
     SyncAgentWithTemplateInput, SyncAgentWithTemplateOutput, UpdateTemplate, UpdateTemplateInput,
     UpdateTemplateOutput,
 };
+pub use skill::{
+    AssignSkillToAgent, AssignSkillToAgentInput, CreateSkill, CreateSkillInput, CreateSkillOutput,
+    DeleteSkill, DeleteSkillInput, ListSkills, ListSkillsInput, ListSkillsOutput,
+    UnassignSkillFromAgent, UnassignSkillFromAgentInput, UpdateSkill, UpdateSkillInput,
+    UpdateSkillOutput,
+};
 pub use terminal::{
     CloseTerminal, CloseTerminalInput, CloseTerminalOutput, OpenTerminal, OpenTerminalInput,
     OpenTerminalOutput, ResizeTerminal, ResizeTerminalInput, TerminalSessions, WriteToTerminal,

crates/application/src/skill/mod.rs

@@ -0,0 +1,21 @@
+//! Skill use cases (ARCHITECTURE §14.2; L12).
+//!
+//! Skills are reusable, model-agnostic workflows (IdeA's universal equivalent of
+//! a CLI slash-command). This module owns their CRUD across both scopes
+//! ([`domain::skill::SkillScope`]) and the agent↔skill assignment that records a
+//! [`domain::skill::SkillRef`] in the project manifest. The actual injection of
+//! an assigned skill's body into the generated convention file happens at agent
+//! activation (L6).
+//!
+//! Every use case talks only to ports ([`domain::ports::SkillStore`],
+//! [`domain::ports::AgentContextStore`], [`domain::ports::IdGenerator`],
+//! [`domain::ports::EventBus`]).
+
+mod usecases;
+
+pub use usecases::{
+    AssignSkillToAgent, AssignSkillToAgentInput, CreateSkill, CreateSkillInput, CreateSkillOutput,
+    DeleteSkill, DeleteSkillInput, ListSkills, ListSkillsInput, ListSkillsOutput,
+    UnassignSkillFromAgent, UnassignSkillFromAgentInput, UpdateSkill, UpdateSkillInput,
+    UpdateSkillOutput,
+};

crates/application/src/skill/usecases.rs

@@ -0,0 +1,339 @@
+//! Skill use cases (ARCHITECTURE §14.2; L12).
+//!
+//! - **CRUD** in either scope: [`CreateSkill`], [`UpdateSkill`], [`DeleteSkill`],
+//!   [`ListSkills`].
+//! - **Assignment**: [`AssignSkillToAgent`] / [`UnassignSkillFromAgent`] mutate
+//!   the project manifest entry's `skills` and announce
+//!   [`DomainEvent::SkillAssigned`]. Both are idempotent.
+
+use std::sync::Arc;
+
+use domain::ports::{AgentContextStore, EventBus, IdGenerator, SkillStore};
+use domain::{
+    AgentId, AgentManifest, DomainEvent, MarkdownDoc, Project, ProjectPath, Skill, SkillId,
+    SkillRef, SkillScope,
+};
+
+use crate::error::AppError;
+
+// ---------------------------------------------------------------------------
+// CreateSkill
+// ---------------------------------------------------------------------------
+
+/// Input for [`CreateSkill::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CreateSkillInput {
+    /// Display name (also the `.md` stem on disk).
+    pub name: String,
+    /// Initial Markdown body.
+    pub content: String,
+    /// Scope the skill is created in (selects its backing store).
+    pub scope: SkillScope,
+    /// Active project root (used only for [`SkillScope::Project`]).
+    pub project_root: ProjectPath,
+}
+
+/// Output of [`CreateSkill::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct CreateSkillOutput {
+    /// The created skill.
+    pub skill: Skill,
+}
+
+/// Creates a skill in the store of its [`SkillScope`].
+pub struct CreateSkill {
+    skills: Arc<dyn SkillStore>,
+    ids: Arc<dyn IdGenerator>,
+}
+
+impl CreateSkill {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(skills: Arc<dyn SkillStore>, ids: Arc<dyn IdGenerator>) -> Self {
+        Self { skills, ids }
+    }
+
+    /// Executes creation.
+    ///
+    /// # Errors
+    /// - [`AppError::Invalid`] if `name`/`content` is empty,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: CreateSkillInput) -> Result<CreateSkillOutput, AppError> {
+        let id = SkillId::from_uuid(self.ids.new_uuid());
+        let skill = Skill::new(id, input.name, MarkdownDoc::new(input.content), input.scope)
+            .map_err(|e| AppError::Invalid(e.to_string()))?;
+        self.skills.save(&skill, &input.project_root).await?;
+        Ok(CreateSkillOutput { skill })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// UpdateSkill
+// ---------------------------------------------------------------------------
+
+/// Input for [`UpdateSkill::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct UpdateSkillInput {
+    /// Scope the skill lives in.
+    pub scope: SkillScope,
+    /// Skill to update.
+    pub skill_id: SkillId,
+    /// New Markdown body.
+    pub content: String,
+    /// Active project root (used only for [`SkillScope::Project`]).
+    pub project_root: ProjectPath,
+}
+
+/// Output of [`UpdateSkill::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct UpdateSkillOutput {
+    /// The updated skill.
+    pub skill: Skill,
+}
+
+/// Replaces a skill's content (re-validating the non-empty invariant).
+pub struct UpdateSkill {
+    skills: Arc<dyn SkillStore>,
+}
+
+impl UpdateSkill {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(skills: Arc<dyn SkillStore>) -> Self {
+        Self { skills }
+    }
+
+    /// Executes the update.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the skill is unknown in that scope,
+    /// - [`AppError::Invalid`] if the new content is empty,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: UpdateSkillInput) -> Result<UpdateSkillOutput, AppError> {
+        let current = self
+            .skills
+            .get(input.scope, &input.project_root, input.skill_id)
+            .await?;
+        let updated = current
+            .with_content(MarkdownDoc::new(input.content))
+            .map_err(|e| AppError::Invalid(e.to_string()))?;
+        self.skills.save(&updated, &input.project_root).await?;
+        Ok(UpdateSkillOutput { skill: updated })
+    }
+}
+
+// ---------------------------------------------------------------------------
+// ListSkills / DeleteSkill
+// ---------------------------------------------------------------------------
+
+/// Input for [`ListSkills::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ListSkillsInput {
+    /// Scope to list.
+    pub scope: SkillScope,
+    /// Active project root (used only for [`SkillScope::Project`]).
+    pub project_root: ProjectPath,
+}
+
+/// Output of [`ListSkills::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ListSkillsOutput {
+    /// All skills in the requested scope.
+    pub skills: Vec<Skill>,
+}
+
+/// Lists the skills in one scope.
+pub struct ListSkills {
+    skills: Arc<dyn SkillStore>,
+}
+
+impl ListSkills {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(skills: Arc<dyn SkillStore>) -> Self {
+        Self { skills }
+    }
+
+    /// Lists skills in `input.scope`.
+    ///
+    /// # Errors
+    /// [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: ListSkillsInput) -> Result<ListSkillsOutput, AppError> {
+        Ok(ListSkillsOutput {
+            skills: self.skills.list(input.scope, &input.project_root).await?,
+        })
+    }
+}
+
+/// Input for [`DeleteSkill::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct DeleteSkillInput {
+    /// Scope the skill lives in.
+    pub scope: SkillScope,
+    /// Skill to delete.
+    pub skill_id: SkillId,
+    /// Active project root (used only for [`SkillScope::Project`]).
+    pub project_root: ProjectPath,
+}
+
+/// Deletes a skill from its scope's store.
+///
+/// Agents that referenced it keep their [`SkillRef`]; the injection step simply
+/// finds nothing to resolve for the now-absent skill and skips it.
+pub struct DeleteSkill {
+    skills: Arc<dyn SkillStore>,
+}
+
+impl DeleteSkill {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(skills: Arc<dyn SkillStore>) -> Self {
+        Self { skills }
+    }
+
+    /// Deletes the skill.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the skill is unknown in that scope,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: DeleteSkillInput) -> Result<(), AppError> {
+        self.skills
+            .delete(input.scope, &input.project_root, input.skill_id)
+            .await?;
+        Ok(())
+    }
+}
+
+// ---------------------------------------------------------------------------
+// AssignSkillToAgent / UnassignSkillFromAgent
+// ---------------------------------------------------------------------------
+
+/// Input for [`AssignSkillToAgent::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AssignSkillToAgentInput {
+    /// The owning project.
+    pub project: Project,
+    /// The agent receiving the skill.
+    pub agent_id: AgentId,
+    /// The skill to assign.
+    pub skill: SkillRef,
+}
+
+/// Assigns a skill to an agent by recording a [`SkillRef`] in its manifest entry.
+/// Idempotent: re-assigning the same skill is a no-op (no duplicate).
+pub struct AssignSkillToAgent {
+    contexts: Arc<dyn AgentContextStore>,
+    events: Arc<dyn EventBus>,
+}
+
+impl AssignSkillToAgent {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(contexts: Arc<dyn AgentContextStore>, events: Arc<dyn EventBus>) -> Self {
+        Self { contexts, events }
+    }
+
+    /// Executes the assignment.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the agent is unknown to the project,
+    /// - [`AppError::Invalid`] if the resulting manifest is invalid,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: AssignSkillToAgentInput) -> Result<(), AppError> {
+        let mut manifest = self.contexts.load_manifest(&input.project).await?;
+        let entry = manifest
+            .entries
+            .iter_mut()
+            .find(|e| e.agent_id == input.agent_id)
+            .ok_or_else(|| AppError::NotFound(format!("agent {}", input.agent_id)))?;
+
+        // Mutate through the domain entity so the dedup invariant is enforced in
+        // one place, then fold the result back into the manifest entry.
+        let mut agent = entry.to_agent().map_err(|e| AppError::Invalid(e.to_string()))?;
+        let changed = agent.assign_skill(input.skill);
+        *entry = domain::ManifestEntry::from_agent(&agent);
+
+        if changed {
+            self.persist_and_announce(&input.project, manifest, input.agent_id, input.skill.skill_id, true)
+                .await?;
+        }
+        Ok(())
+    }
+
+    /// Saves the manifest and announces the assignment change.
+    async fn persist_and_announce(
+        &self,
+        project: &Project,
+        manifest: AgentManifest,
+        agent_id: AgentId,
+        skill_id: SkillId,
+        assigned: bool,
+    ) -> Result<(), AppError> {
+        let manifest = AgentManifest::new(manifest.version, manifest.entries)
+            .map_err(|e| AppError::Invalid(e.to_string()))?;
+        self.contexts.save_manifest(project, &manifest).await?;
+        self.events.publish(DomainEvent::SkillAssigned {
+            agent_id,
+            skill_id,
+            assigned,
+        });
+        Ok(())
+    }
+}
+
+/// Input for [`UnassignSkillFromAgent::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct UnassignSkillFromAgentInput {
+    /// The owning project.
+    pub project: Project,
+    /// The agent losing the skill.
+    pub agent_id: AgentId,
+    /// The skill to unassign.
+    pub skill_id: SkillId,
+}
+
+/// Removes a skill assignment from an agent. Idempotent: unassigning a skill the
+/// agent does not carry is a no-op.
+pub struct UnassignSkillFromAgent {
+    contexts: Arc<dyn AgentContextStore>,
+    events: Arc<dyn EventBus>,
+}
+
+impl UnassignSkillFromAgent {
+    /// Builds the use case from its ports.
+    #[must_use]
+    pub fn new(contexts: Arc<dyn AgentContextStore>, events: Arc<dyn EventBus>) -> Self {
+        Self { contexts, events }
+    }
+
+    /// Executes the un-assignment.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the agent is unknown to the project,
+    /// - [`AppError::Invalid`] if the resulting manifest is invalid,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: UnassignSkillFromAgentInput) -> Result<(), AppError> {
+        let mut manifest = self.contexts.load_manifest(&input.project).await?;
+        let entry = manifest
+            .entries
+            .iter_mut()
+            .find(|e| e.agent_id == input.agent_id)
+            .ok_or_else(|| AppError::NotFound(format!("agent {}", input.agent_id)))?;
+
+        let mut agent = entry.to_agent().map_err(|e| AppError::Invalid(e.to_string()))?;
+        let changed = agent.unassign_skill(input.skill_id);
+        *entry = domain::ManifestEntry::from_agent(&agent);
+
+        if changed {
+            let manifest = AgentManifest::new(manifest.version, manifest.entries)
+                .map_err(|e| AppError::Invalid(e.to_string()))?;
+            self.contexts.save_manifest(&input.project, &manifest).await?;
+            self.events.publish(DomainEvent::SkillAssigned {
+                agent_id: input.agent_id,
+                skill_id: input.skill_id,
+                assigned: false,
+            });
+        }
+        Ok(())
+    }
+}

crates/application/tests/agent_lifecycle.rs

@@ -26,12 +26,13 @@ use domain::markdown::MarkdownDoc;
 use domain::ports::{
     AgentContextStore, AgentRuntime, ContextInjectionPlan, DirEntry, EventBus, EventStream,
     ExitStatus, FileSystem, FsError, IdGenerator, OutputStream, PreparedContext, ProfileStore,
-    PtyError, PtyHandle, PtyPort, RemotePath, RuntimeError, SpawnSpec, StoreError,
+    PtyError, PtyHandle, PtyPort, RemotePath, RuntimeError, SkillStore, SpawnSpec, StoreError,
 };
 use domain::profile::{AgentProfile, ContextInjection};
 use domain::project::{Project, ProjectPath};
 use domain::remote::RemoteRef;
-use domain::{PtySize, SessionId};
+use domain::skill::{Skill, SkillScope};
+use domain::{PtySize, SessionId, SkillId, SkillRef};
 use uuid::Uuid;
 
 use application::{
@@ -177,6 +178,49 @@ impl ProfileStore for FakeProfiles {
     }
 }
 
+// ---------------------------------------------------------------------------
+// FakeSkills (SkillStore) — an in-memory store seeded with a few skills
+// ---------------------------------------------------------------------------
+
+#[derive(Clone, Default)]
+struct FakeSkills(Arc<Vec<Skill>>);
+
+impl FakeSkills {
+    fn with(skills: Vec<Skill>) -> Self {
+        Self(Arc::new(skills))
+    }
+}
+
+#[async_trait]
+impl SkillStore for FakeSkills {
+    async fn list(&self, scope: SkillScope, _root: &ProjectPath) -> Result<Vec<Skill>, StoreError> {
+        Ok(self.0.iter().filter(|s| s.scope == scope).cloned().collect())
+    }
+    async fn get(
+        &self,
+        scope: SkillScope,
+        _root: &ProjectPath,
+        id: SkillId,
+    ) -> Result<Skill, StoreError> {
+        self.0
+            .iter()
+            .find(|s| s.scope == scope && s.id == id)
+            .cloned()
+            .ok_or(StoreError::NotFound)
+    }
+    async fn save(&self, _skill: &Skill, _root: &ProjectPath) -> Result<(), StoreError> {
+        Ok(())
+    }
+    async fn delete(
+        &self,
+        _scope: SkillScope,
+        _root: &ProjectPath,
+        _id: SkillId,
+    ) -> Result<(), StoreError> {
+        Ok(())
+    }
+}
+
 // ---------------------------------------------------------------------------
 // FakeRuntime (AgentRuntime) — records prepare + returns a configured plan
 // ---------------------------------------------------------------------------
@@ -577,6 +621,7 @@ fn launch_fixture(injection: ContextInjection, plan: Option<ContextInjectionPlan
         Arc::new(runtime),
         Arc::new(fs.clone()),
         Arc::new(pty.clone()),
+        Arc::new(FakeSkills::default()),
         Arc::clone(&sessions),
         Arc::new(bus.clone()),
     );
@@ -695,6 +740,7 @@ async fn two_agents_same_root_get_distinct_run_dirs_no_collision() {
         Arc::new(FakeRuntime::new(Arc::clone(&tr), plan)),
         Arc::new(fs.clone()),
         Arc::new(pty.clone()),
+        Arc::new(FakeSkills::default()),
         Arc::clone(&sessions),
         Arc::new(SpyBus::default()),
     );
@@ -730,6 +776,98 @@ async fn two_agents_same_root_get_distinct_run_dirs_no_collision() {
     assert!(String::from_utf8(writes[1].1.clone()).unwrap().contains("# bravo"));
 }
 
+#[tokio::test]
+async fn launch_conventionfile_injects_assigned_skills_in_order() {
+    // An agent with two assigned global skills; the generated convention file must
+    // carry both skill bodies, after the persona, in assignment order (§14.2).
+    let skill_id = |n: u128| SkillId::from_uuid(Uuid::from_u128(n));
+    let skill = |n: u128, name: &str, body: &str| {
+        Skill::new(skill_id(n), name, MarkdownDoc::new(body), SkillScope::Global).unwrap()
+    };
+
+    let mut agent = scratch_agent(aid(1), "Backend", "agents/backend.md", pid(9));
+    agent.assign_skill(SkillRef::new(skill_id(1), SkillScope::Global));
+    agent.assign_skill(SkillRef::new(skill_id(2), SkillScope::Global));
+
+    let contexts = FakeContexts::with_agent(&agent, "# persona");
+    let profiles = FakeProfiles::new(vec![profile(
+        pid(9),
+        ContextInjection::convention_file("CLAUDE.md").unwrap(),
+    )]);
+    let tr = trace();
+    let fs = FakeFs::new(Arc::clone(&tr));
+    let pty = FakePty::new(Arc::clone(&tr), sid(777));
+    let skills = FakeSkills::with(vec![
+        skill(1, "refactor", "REFAC_BODY"),
+        skill(2, "review", "REVIEW_BODY"),
+    ]);
+    let launch = LaunchAgent::new(
+        Arc::new(contexts),
+        Arc::new(profiles),
+        Arc::new(FakeRuntime::new(
+            Arc::clone(&tr),
+            Some(ContextInjectionPlan::File {
+                target: "CLAUDE.md".to_owned(),
+            }),
+        )),
+        Arc::new(fs.clone()),
+        Arc::new(pty.clone()),
+        Arc::new(skills),
+        Arc::new(TerminalSessions::new()),
+        Arc::new(SpyBus::default()),
+    );
+
+    launch.execute(launch_input(agent.id)).await.unwrap();
+
+    let writes = fs.writes();
+    assert_eq!(writes.len(), 1);
+    let doc = String::from_utf8(writes[0].1.clone()).unwrap();
+    assert!(doc.contains("# persona"), "persona present: {doc}");
+    assert!(doc.contains("REFAC_BODY"), "first skill body present");
+    assert!(doc.contains("REVIEW_BODY"), "second skill body present");
+    // Deterministic order: persona before skills, skill 1 before skill 2.
+    let persona_at = doc.find("# persona").unwrap();
+    let refac_at = doc.find("REFAC_BODY").unwrap();
+    let review_at = doc.find("REVIEW_BODY").unwrap();
+    assert!(persona_at < refac_at && refac_at < review_at, "ordering: {doc}");
+}
+
+#[tokio::test]
+async fn launch_skips_dangling_skill_ref_without_failing() {
+    // The agent references a skill that no longer exists in the store: launch must
+    // still succeed and simply omit it (no Skills section for a sole dangling ref).
+    let mut agent = scratch_agent(aid(1), "Backend", "agents/backend.md", pid(9));
+    agent.assign_skill(SkillRef::new(SkillId::from_uuid(Uuid::from_u128(99)), SkillScope::Global));
+
+    let contexts = FakeContexts::with_agent(&agent, "# persona");
+    let profiles = FakeProfiles::new(vec![profile(
+        pid(9),
+        ContextInjection::convention_file("CLAUDE.md").unwrap(),
+    )]);
+    let tr = trace();
+    let fs = FakeFs::new(Arc::clone(&tr));
+    let pty = FakePty::new(Arc::clone(&tr), sid(777));
+    let launch = LaunchAgent::new(
+        Arc::new(contexts),
+        Arc::new(profiles),
+        Arc::new(FakeRuntime::new(
+            Arc::clone(&tr),
+            Some(ContextInjectionPlan::File {
+                target: "CLAUDE.md".to_owned(),
+            }),
+        )),
+        Arc::new(fs.clone()),
+        Arc::new(pty.clone()),
+        Arc::new(FakeSkills::default()), // empty store ⇒ the ref is dangling
+        Arc::new(TerminalSessions::new()),
+        Arc::new(SpyBus::default()),
+    );
+
+    launch.execute(launch_input(agent.id)).await.expect("launch must succeed");
+    let doc = String::from_utf8(fs.writes()[0].1.clone()).unwrap();
+    assert!(!doc.contains("# Skills"), "no Skills section for a dangling ref: {doc}");
+}
+
 #[tokio::test]
 async fn launch_stdin_strategy_pipes_context_after_spawn() {
     let (launch, agent, fs, pty, _bus, _sessions, tr) =
@@ -771,6 +909,7 @@ async fn launch_unknown_profile_is_not_found() {
         Arc::new(FakeRuntime::new(Arc::clone(&tr), Some(ContextInjectionPlan::Stdin))),
         Arc::new(FakeFs::new(Arc::clone(&tr))),
         Arc::new(pty.clone()),
+        Arc::new(FakeSkills::default()),
         Arc::new(TerminalSessions::new()),
         Arc::new(SpyBus::default()),
     );

crates/application/tests/skill_usecases.rs

@@ -0,0 +1,395 @@
+//! L12 tests for the skill use cases with in-memory port fakes (no real
+//! store/FS): CRUD across scopes (`CreateSkill`, `UpdateSkill`, `DeleteSkill`,
+//! `ListSkills`) and the manifest-mutating assignment
+//! (`AssignSkillToAgent` / `UnassignSkillFromAgent`), asserting the
+//! `SkillAssigned` event and idempotence.
+
+use std::sync::{Arc, Mutex};
+
+use async_trait::async_trait;
+use domain::events::DomainEvent;
+use domain::ids::{AgentId, ProfileId, ProjectId, SkillId};
+use domain::markdown::MarkdownDoc;
+use domain::ports::{
+    AgentContextStore, EventBus, EventStream, IdGenerator, SkillStore, StoreError,
+};
+use domain::skill::{Skill, SkillScope};
+use domain::{AgentManifest, ManifestEntry, Project, ProjectPath, RemoteRef, SkillRef};
+use uuid::Uuid;
+
+use application::{
+    AssignSkillToAgent, AssignSkillToAgentInput, CreateSkill, CreateSkillInput, DeleteSkill,
+    DeleteSkillInput, ListSkills, ListSkillsInput, UnassignSkillFromAgent,
+    UnassignSkillFromAgentInput, UpdateSkill, UpdateSkillInput,
+};
+
+// ---------------------------------------------------------------------------
+// Fakes
+// ---------------------------------------------------------------------------
+
+/// In-memory skill store keyed by `(scope, id)`, honouring scope isolation.
+#[derive(Clone, Default)]
+struct FakeSkills(Arc<Mutex<Vec<Skill>>>);
+#[async_trait]
+impl SkillStore for FakeSkills {
+    async fn list(&self, scope: SkillScope, _root: &ProjectPath) -> Result<Vec<Skill>, StoreError> {
+        Ok(self
+            .0
+            .lock()
+            .unwrap()
+            .iter()
+            .filter(|s| s.scope == scope)
+            .cloned()
+            .collect())
+    }
+    async fn get(
+        &self,
+        scope: SkillScope,
+        _root: &ProjectPath,
+        id: SkillId,
+    ) -> Result<Skill, StoreError> {
+        self.0
+            .lock()
+            .unwrap()
+            .iter()
+            .find(|s| s.scope == scope && s.id == id)
+            .cloned()
+            .ok_or(StoreError::NotFound)
+    }
+    async fn save(&self, skill: &Skill, _root: &ProjectPath) -> Result<(), StoreError> {
+        let mut v = self.0.lock().unwrap();
+        if let Some(slot) = v.iter_mut().find(|s| s.scope == skill.scope && s.id == skill.id) {
+            *slot = skill.clone();
+        } else {
+            v.push(skill.clone());
+        }
+        Ok(())
+    }
+    async fn delete(
+        &self,
+        scope: SkillScope,
+        _root: &ProjectPath,
+        id: SkillId,
+    ) -> Result<(), StoreError> {
+        let mut v = self.0.lock().unwrap();
+        let before = v.len();
+        v.retain(|s| !(s.scope == scope && s.id == id));
+        if v.len() == before {
+            return Err(StoreError::NotFound);
+        }
+        Ok(())
+    }
+}
+
+#[derive(Clone)]
+struct FakeContexts(Arc<Mutex<AgentManifest>>);
+impl FakeContexts {
+    fn new(entries: Vec<ManifestEntry>) -> Self {
+        Self(Arc::new(Mutex::new(AgentManifest { version: 1, entries })))
+    }
+    fn manifest(&self) -> AgentManifest {
+        self.0.lock().unwrap().clone()
+    }
+}
+#[async_trait]
+impl AgentContextStore for FakeContexts {
+    async fn read_context(
+        &self,
+        _p: &Project,
+        _agent: &AgentId,
+    ) -> Result<MarkdownDoc, StoreError> {
+        Err(StoreError::NotFound)
+    }
+    async fn write_context(
+        &self,
+        _p: &Project,
+        _agent: &AgentId,
+        _md: &MarkdownDoc,
+    ) -> Result<(), StoreError> {
+        Ok(())
+    }
+    async fn load_manifest(&self, _p: &Project) -> Result<AgentManifest, StoreError> {
+        Ok(self.manifest())
+    }
+    async fn save_manifest(&self, _p: &Project, m: &AgentManifest) -> Result<(), StoreError> {
+        *self.0.lock().unwrap() = m.clone();
+        Ok(())
+    }
+}
+
+#[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())
+    }
+}
+
+struct SeqIds(Mutex<u128>);
+impl SeqIds {
+    fn new() -> Self {
+        Self(Mutex::new(1))
+    }
+}
+impl IdGenerator for SeqIds {
+    fn new_uuid(&self) -> Uuid {
+        let mut n = self.0.lock().unwrap();
+        let id = Uuid::from_u128(*n);
+        *n += 1;
+        id
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Builders
+// ---------------------------------------------------------------------------
+
+fn pid(n: u128) -> ProfileId {
+    ProfileId::from_uuid(Uuid::from_u128(n))
+}
+fn aid(n: u128) -> AgentId {
+    AgentId::from_uuid(Uuid::from_u128(n))
+}
+fn sid(n: u128) -> SkillId {
+    SkillId::from_uuid(Uuid::from_u128(n))
+}
+fn root() -> ProjectPath {
+    ProjectPath::new("/home/me/demo").unwrap()
+}
+fn project() -> Project {
+    Project::new(
+        ProjectId::from_uuid(Uuid::from_u128(1000)),
+        "demo",
+        root(),
+        RemoteRef::local(),
+        1_700_000_000_000,
+    )
+    .unwrap()
+}
+fn scratch_entry(agent: AgentId) -> ManifestEntry {
+    ManifestEntry::new(agent, "A", "agents/a.md", pid(1), None, false, None).unwrap()
+}
+
+// ---------------------------------------------------------------------------
+// CRUD
+// ---------------------------------------------------------------------------
+
+#[tokio::test]
+async fn create_skill_persists_in_its_scope() {
+    let store = FakeSkills::default();
+    let out = CreateSkill::new(Arc::new(store.clone()), Arc::new(SeqIds::new()))
+        .execute(CreateSkillInput {
+            name: "refactor".to_owned(),
+            content: "# body".to_owned(),
+            scope: SkillScope::Project,
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(out.skill.scope, SkillScope::Project);
+    assert_eq!(
+        store.list(SkillScope::Project, &root()).await.unwrap().len(),
+        1
+    );
+    assert!(store
+        .list(SkillScope::Global, &root())
+        .await
+        .unwrap()
+        .is_empty());
+}
+
+#[tokio::test]
+async fn create_skill_rejects_empty_content() {
+    let store = FakeSkills::default();
+    let err = CreateSkill::new(Arc::new(store), Arc::new(SeqIds::new()))
+        .execute(CreateSkillInput {
+            name: "k".to_owned(),
+            content: String::new(),
+            scope: SkillScope::Global,
+            project_root: root(),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "INVALID");
+}
+
+#[tokio::test]
+async fn update_skill_replaces_content() {
+    let store = FakeSkills::default();
+    store
+        .save(
+            &Skill::new(sid(1), "k", MarkdownDoc::new("v1"), SkillScope::Global).unwrap(),
+            &root(),
+        )
+        .await
+        .unwrap();
+
+    let out = UpdateSkill::new(Arc::new(store.clone()))
+        .execute(UpdateSkillInput {
+            scope: SkillScope::Global,
+            skill_id: sid(1),
+            content: "v2".to_owned(),
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+    assert_eq!(out.skill.content_md.as_str(), "v2");
+}
+
+#[tokio::test]
+async fn update_unknown_skill_is_not_found() {
+    let store = FakeSkills::default();
+    let err = UpdateSkill::new(Arc::new(store))
+        .execute(UpdateSkillInput {
+            scope: SkillScope::Global,
+            skill_id: sid(404),
+            content: "x".to_owned(),
+            project_root: root(),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
+#[tokio::test]
+async fn list_is_scope_filtered() {
+    let store = FakeSkills::default();
+    store
+        .save(
+            &Skill::new(sid(1), "g", MarkdownDoc::new("x"), SkillScope::Global).unwrap(),
+            &root(),
+        )
+        .await
+        .unwrap();
+    store
+        .save(
+            &Skill::new(sid(2), "p", MarkdownDoc::new("x"), SkillScope::Project).unwrap(),
+            &root(),
+        )
+        .await
+        .unwrap();
+
+    let listed = ListSkills::new(Arc::new(store))
+        .execute(ListSkillsInput {
+            scope: SkillScope::Global,
+            project_root: root(),
+        })
+        .await
+        .unwrap();
+    assert_eq!(listed.skills.len(), 1);
+    assert_eq!(listed.skills[0].id, sid(1));
+}
+
+#[tokio::test]
+async fn delete_then_delete_is_not_found() {
+    let store = FakeSkills::default();
+    store
+        .save(
+            &Skill::new(sid(1), "k", MarkdownDoc::new("x"), SkillScope::Project).unwrap(),
+            &root(),
+        )
+        .await
+        .unwrap();
+    let uc = DeleteSkill::new(Arc::new(store));
+    uc.execute(DeleteSkillInput {
+        scope: SkillScope::Project,
+        skill_id: sid(1),
+        project_root: root(),
+    })
+    .await
+    .unwrap();
+    let err = uc
+        .execute(DeleteSkillInput {
+            scope: SkillScope::Project,
+            skill_id: sid(1),
+            project_root: root(),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
+// ---------------------------------------------------------------------------
+// Assignment
+// ---------------------------------------------------------------------------
+
+fn assigned_event(events: &[DomainEvent]) -> Vec<(SkillId, bool)> {
+    events
+        .iter()
+        .filter_map(|e| match e {
+            DomainEvent::SkillAssigned {
+                skill_id, assigned, ..
+            } => Some((*skill_id, *assigned)),
+            _ => None,
+        })
+        .collect()
+}
+
+#[tokio::test]
+async fn assign_mutates_manifest_emits_event_and_is_idempotent() {
+    let contexts = FakeContexts::new(vec![scratch_entry(aid(1))]);
+    let bus = SpyBus::default();
+    let uc = AssignSkillToAgent::new(Arc::new(contexts.clone()), Arc::new(bus.clone()));
+    let input = AssignSkillToAgentInput {
+        project: project(),
+        agent_id: aid(1),
+        skill: SkillRef::new(sid(9), SkillScope::Global),
+    };
+
+    uc.execute(input.clone()).await.unwrap();
+    // Re-assigning the same skill is a no-op (dedup).
+    uc.execute(input).await.unwrap();
+
+    let entry = &contexts.manifest().entries[0];
+    assert_eq!(entry.skills.len(), 1, "no duplicate assignment");
+    assert_eq!(entry.skills[0].skill_id, sid(9));
+    assert_eq!(
+        assigned_event(&bus.events()),
+        vec![(sid(9), true)],
+        "exactly one assign event despite double execute"
+    );
+}
+
+#[tokio::test]
+async fn unassign_removes_and_emits_false_then_is_noop() {
+    let mut entry = scratch_entry(aid(1));
+    entry.skills.push(SkillRef::new(sid(9), SkillScope::Global));
+    let contexts = FakeContexts::new(vec![entry]);
+    let bus = SpyBus::default();
+    let uc = UnassignSkillFromAgent::new(Arc::new(contexts.clone()), Arc::new(bus.clone()));
+    let input = UnassignSkillFromAgentInput {
+        project: project(),
+        agent_id: aid(1),
+        skill_id: sid(9),
+    };
+
+    uc.execute(input.clone()).await.unwrap();
+    uc.execute(input).await.unwrap(); // already gone → no-op
+
+    assert!(contexts.manifest().entries[0].skills.is_empty());
+    assert_eq!(assigned_event(&bus.events()), vec![(sid(9), false)]);
+}
+
+#[tokio::test]
+async fn assign_to_unknown_agent_is_not_found() {
+    let contexts = FakeContexts::new(vec![]);
+    let bus = SpyBus::default();
+    let err = AssignSkillToAgent::new(Arc::new(contexts), Arc::new(bus))
+        .execute(AssignSkillToAgentInput {
+            project: project(),
+            agent_id: aid(404),
+            skill: SkillRef::new(sid(9), SkillScope::Global),
+        })
+        .await
+        .unwrap_err();
+    assert_eq!(err.code(), "NOT_FOUND");
+}

crates/domain/src/ports.rs

@@ -34,6 +34,7 @@ use crate::markdown::MarkdownDoc;
 use crate::profile::AgentProfile;
 use crate::project::{Project, ProjectPath};
 use crate::remote::RemoteKind;
+use crate::skill::{Skill, SkillScope};
 use crate::template::AgentTemplate;
 use crate::terminal::PtySize;
 
@@ -209,7 +210,7 @@ pub enum FsError {
 }
 
 /// Errors from persistence stores ([`TemplateStore`], [`ProjectStore`],
-/// [`AgentContextStore`]).
+/// [`AgentContextStore`], [`SkillStore`]).
 #[derive(Debug, Clone, PartialEq, Eq, Error)]
 pub enum StoreError {
     /// The requested item was not found.
@@ -460,6 +461,57 @@ pub trait TemplateStore: Send + Sync {
     async fn delete(&self, id: crate::ids::TemplateId) -> Result<(), StoreError>;
 }
 
+/// CRUD for [`Skill`]s across both scopes ([`SkillScope::Global`] in the IDE
+/// store, [`SkillScope::Project`] under `.ideai/skills/`), per ARCHITECTURE
+/// §14.2 and L12.
+///
+/// The two scopes are **isolated**: a skill saved as `Project` never surfaces in
+/// a `Global` listing and vice-versa. Each call carries the [`SkillScope`]
+/// explicitly (or via the [`Skill`] for [`save`](Self::save)) so the adapter
+/// resolves the right backing location.
+///
+/// `root` identifies the project whose `.ideai/skills/` to use for
+/// [`SkillScope::Project`]; it is **ignored** for [`SkillScope::Global`] (which
+/// lives in the machine-global IDE store). Passing the root per call — rather
+/// than baking it into the adapter — keeps a single store instance correct
+/// across every open project (mirroring [`AgentContextStore`]).
+#[async_trait]
+pub trait SkillStore: Send + Sync {
+    /// Lists all skills in `scope` (for `root`'s project when project-scoped).
+    ///
+    /// # Errors
+    /// [`StoreError`] on failure.
+    async fn list(&self, scope: SkillScope, root: &ProjectPath) -> Result<Vec<Skill>, StoreError>;
+
+    /// Gets a skill by id within `scope`.
+    ///
+    /// # Errors
+    /// [`StoreError::NotFound`] if absent in that scope.
+    async fn get(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        id: crate::ids::SkillId,
+    ) -> Result<Skill, StoreError>;
+
+    /// Saves (creates or replaces by id) a skill in its own [`Skill::scope`].
+    ///
+    /// # Errors
+    /// [`StoreError`] on failure.
+    async fn save(&self, skill: &Skill, root: &ProjectPath) -> Result<(), StoreError>;
+
+    /// Deletes a skill by id within `scope`.
+    ///
+    /// # Errors
+    /// [`StoreError::NotFound`] if absent in that scope.
+    async fn delete(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        id: crate::ids::SkillId,
+    ) -> Result<(), StoreError>;
+}
+
 /// Persistence of the known-projects registry and the workspace.
 #[async_trait]
 pub trait ProjectStore: Send + Sync {

crates/infrastructure/src/lib.rs

@@ -32,4 +32,6 @@ pub use process::LocalProcessSpawner;
 pub use pty::PortablePtyAdapter;
 pub use remote::{remote_host, LocalHost};
 pub use runtime::CliAgentRuntime;
-pub use store::{FsProfileStore, FsProjectStore, FsTemplateStore, IdeaiContextStore};
+pub use store::{
+    FsProfileStore, FsProjectStore, FsSkillStore, FsTemplateStore, IdeaiContextStore,
+};

crates/infrastructure/src/store/mod.rs

@@ -7,9 +7,11 @@
 mod context;
 mod profile;
 mod project;
+mod skill;
 mod template;
 
 pub use context::IdeaiContextStore;
 pub use profile::FsProfileStore;
 pub use project::FsProjectStore;
+pub use skill::FsSkillStore;
 pub use template::FsTemplateStore;

crates/infrastructure/src/store/skill.rs

@@ -0,0 +1,263 @@
+//! [`FsSkillStore`] — file implementation of the [`SkillStore`] port
+//! (ARCHITECTURE §14.2, L12).
+//!
+//! Skills are reusable, model-agnostic workflows. They live in **two isolated
+//! scopes**, each backed by its own directory but the same on-disk shape
+//! (mirroring [`crate::store::FsTemplateStore`]): a small JSON index carrying the
+//! metadata needed to list without parsing every `.md`, plus the Markdown bodies
+//! under `md/`:
+//!
+//! ```text
+//! <app_data_dir>/skills/            # SkillScope::Global  (shared across projects)
+//! <project_root>/.ideai/skills/     # SkillScope::Project (travels with the code)
+//! ├── index.json   # { version, skills: [{ id, name, contentHash }] }
+//! └── md/
+//!     └── <id>.md   # a skill's Markdown content
+//! ```
+//!
+//! The two scopes never bleed into one another: a `Project` skill is invisible to
+//! a `Global` listing and vice-versa, because each resolves to a different
+//! directory. All I/O goes through the [`FileSystem`] port, so the adapter is
+//! location-neutral (a project hosted over SSH/WSL works unchanged) and
+//! Tauri-agnostic.
+//!
+//! Like the template store, [`delete`](SkillStore::delete) drops the index row
+//! and leaves the orphaned `md/<id>.md` on disk (the [`FileSystem`] port exposes
+//! no remove); since listing is index-driven, the skill is effectively gone.
+
+use std::hash::{Hash, Hasher};
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use serde::{Deserialize, Serialize};
+
+use domain::ids::SkillId;
+use domain::markdown::MarkdownDoc;
+use domain::ports::{FileSystem, RemotePath, SkillStore, StoreError};
+use domain::project::ProjectPath;
+use domain::skill::{Skill, SkillScope};
+
+/// Directory (under app-data) holding the global skills store.
+const GLOBAL_SKILLS_DIR: &str = "skills";
+
+/// The `.ideai/` directory name inside a project root.
+const IDEAI_DIR: &str = ".ideai";
+
+/// Sub-path of the project-scoped skills store inside `.ideai/`.
+const PROJECT_SKILLS_DIR: &str = "skills";
+
+/// Index file name inside a skills dir.
+const INDEX_FILE: &str = "index.json";
+
+/// Current schema version of the index file.
+const INDEX_VERSION: u32 = 1;
+
+/// One metadata row in `index.json` (the `.md` content lives separately).
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct IndexEntry {
+    id: SkillId,
+    name: String,
+    content_hash: String,
+}
+
+/// On-disk shape of a scope's `index.json`.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct IndexDoc {
+    version: u32,
+    skills: Vec<IndexEntry>,
+}
+
+impl Default for IndexDoc {
+    fn default() -> Self {
+        Self {
+            version: INDEX_VERSION,
+            skills: Vec::new(),
+        }
+    }
+}
+
+/// A stable, dependency-free digest of Markdown content for out-of-app edit
+/// detection — deterministic across runs and platforms (fixed-key hasher).
+fn content_hash(md: &MarkdownDoc) -> String {
+    let mut hasher = std::collections::hash_map::DefaultHasher::new();
+    md.as_str().hash(&mut hasher);
+    format!("{:016x}", hasher.finish())
+}
+
+/// File-backed [`SkillStore`], composing a [`FileSystem`] port. Holds only the
+/// machine-global app-data dir; the project root for [`SkillScope::Project`] is
+/// supplied **per call**, so a single instance serves every open project
+/// (mirroring [`crate::store::IdeaiContextStore`]).
+#[derive(Clone)]
+pub struct FsSkillStore {
+    fs: Arc<dyn FileSystem>,
+    app_data_dir: String,
+}
+
+impl FsSkillStore {
+    /// Builds the store from an injected [`FileSystem`] and the global app-data
+    /// dir (used for [`SkillScope::Global`]). Directories are created on first
+    /// write.
+    #[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(),
+        }
+    }
+
+    /// Root directory of a scope's store. `root` is ignored for `Global`.
+    fn dir(&self, scope: SkillScope, root: &ProjectPath) -> String {
+        match scope {
+            SkillScope::Global => {
+                let base = self.app_data_dir.trim_end_matches(['/', '\\']);
+                format!("{base}/{GLOBAL_SKILLS_DIR}")
+            }
+            SkillScope::Project => {
+                let base = root.as_str().trim_end_matches(['/', '\\']);
+                format!("{base}/{IDEAI_DIR}/{PROJECT_SKILLS_DIR}")
+            }
+        }
+    }
+
+    /// `<scope-dir>/index.json`.
+    fn index_path(&self, scope: SkillScope, root: &ProjectPath) -> RemotePath {
+        RemotePath::new(format!("{}/{INDEX_FILE}", self.dir(scope, root)))
+    }
+
+    /// `<scope-dir>/md/<id>.md`.
+    fn md_path(&self, scope: SkillScope, root: &ProjectPath, id: SkillId) -> RemotePath {
+        RemotePath::new(format!("{}/md/{id}.md", self.dir(scope, root)))
+    }
+
+    /// Reads a scope's index, returning an empty default if absent.
+    async fn read_index(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+    ) -> Result<IndexDoc, StoreError> {
+        match self.fs.read(&self.index_path(scope, root)).await {
+            Ok(bytes) => {
+                serde_json::from_slice(&bytes).map_err(|e| StoreError::Serialization(e.to_string()))
+            }
+            Err(domain::ports::FsError::NotFound(_)) => Ok(IndexDoc::default()),
+            Err(e) => Err(StoreError::Io(e.to_string())),
+        }
+    }
+
+    /// Writes a scope's index, ensuring its directory exists.
+    async fn write_index(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        doc: &IndexDoc,
+    ) -> Result<(), StoreError> {
+        self.fs
+            .create_dir_all(&RemotePath::new(self.dir(scope, root)))
+            .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.index_path(scope, root), &bytes)
+            .await
+            .map_err(|e| StoreError::Io(e.to_string()))
+    }
+
+    /// Reconstructs the [`Skill`] for an index entry by reading its `.md`.
+    async fn load(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        entry: &IndexEntry,
+    ) -> Result<Skill, StoreError> {
+        let bytes = self
+            .fs
+            .read(&self.md_path(scope, root, entry.id))
+            .await
+            .map_err(|e| match e {
+                domain::ports::FsError::NotFound(_) => StoreError::NotFound,
+                other => StoreError::Io(other.to_string()),
+            })?;
+        let content =
+            String::from_utf8(bytes).map_err(|e| StoreError::Serialization(e.to_string()))?;
+        Skill::new(entry.id, entry.name.clone(), MarkdownDoc::new(content), scope)
+            .map_err(|e| StoreError::Serialization(e.to_string()))
+    }
+}
+
+#[async_trait]
+impl SkillStore for FsSkillStore {
+    async fn list(&self, scope: SkillScope, root: &ProjectPath) -> Result<Vec<Skill>, StoreError> {
+        let index = self.read_index(scope, root).await?;
+        let mut out = Vec::with_capacity(index.skills.len());
+        for entry in &index.skills {
+            out.push(self.load(scope, root, entry).await?);
+        }
+        Ok(out)
+    }
+
+    async fn get(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        id: SkillId,
+    ) -> Result<Skill, StoreError> {
+        let index = self.read_index(scope, root).await?;
+        let entry = index
+            .skills
+            .iter()
+            .find(|e| e.id == id)
+            .ok_or(StoreError::NotFound)?;
+        self.load(scope, root, entry).await
+    }
+
+    async fn save(&self, skill: &Skill, root: &ProjectPath) -> Result<(), StoreError> {
+        let scope = skill.scope;
+        // (1) Write the Markdown content.
+        self.fs
+            .create_dir_all(&RemotePath::new(format!("{}/md", self.dir(scope, root))))
+            .await
+            .map_err(|e| StoreError::Io(e.to_string()))?;
+        self.fs
+            .write(
+                &self.md_path(scope, root, skill.id),
+                skill.content_md.as_str().as_bytes(),
+            )
+            .await
+            .map_err(|e| StoreError::Io(e.to_string()))?;
+
+        // (2) Upsert the index metadata.
+        let mut index = self.read_index(scope, root).await?;
+        let row = IndexEntry {
+            id: skill.id,
+            name: skill.name.clone(),
+            content_hash: content_hash(&skill.content_md),
+        };
+        if let Some(slot) = index.skills.iter_mut().find(|e| e.id == skill.id) {
+            *slot = row;
+        } else {
+            index.skills.push(row);
+        }
+        self.write_index(scope, root, &index).await
+    }
+
+    async fn delete(
+        &self,
+        scope: SkillScope,
+        root: &ProjectPath,
+        id: SkillId,
+    ) -> Result<(), StoreError> {
+        let mut index = self.read_index(scope, root).await?;
+        let before = index.skills.len();
+        index.skills.retain(|e| e.id != id);
+        if index.skills.len() == before {
+            return Err(StoreError::NotFound);
+        }
+        // The orphaned `md/<id>.md` is left on disk (no FileSystem delete); the
+        // index no longer references it, so it is effectively gone.
+        self.write_index(scope, root, &index).await
+    }
+}

crates/infrastructure/tests/skill_store.rs

@@ -0,0 +1,211 @@
+//! L12 integration tests for [`FsSkillStore`] against a real temp directory and a
+//! real [`LocalFileSystem`]: md + `index.json` round-trip in **both** scopes,
+//! scope isolation (a `Project` skill never appears under `Global` and vice
+//! versa), upsert, delete, tolerant reads, and the on-disk layout.
+
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use domain::ids::SkillId;
+use domain::markdown::MarkdownDoc;
+use domain::ports::{FileSystem, RemotePath, SkillStore, StoreError};
+use domain::project::ProjectPath;
+use domain::skill::{Skill, SkillScope};
+use infrastructure::{FsSkillStore, LocalFileSystem};
+use uuid::Uuid;
+
+/// A unique scratch directory under the OS temp dir, cleaned up on drop. It plays
+/// **both** roles: its own path is the global app-data dir, and a `project/`
+/// child is the project root (so the two scopes resolve to disjoint subtrees).
+struct TempDir(PathBuf);
+impl TempDir {
+    fn new() -> Self {
+        let p = std::env::temp_dir().join(format!("idea-l12-skill-{}", Uuid::new_v4()));
+        std::fs::create_dir_all(&p).unwrap();
+        Self(p)
+    }
+    fn app_data_dir(&self) -> String {
+        self.0.to_string_lossy().into_owned()
+    }
+    fn project_root(&self) -> ProjectPath {
+        ProjectPath::new(self.0.join("project").to_string_lossy().into_owned()).unwrap()
+    }
+    fn child(&self, rel: &str) -> RemotePath {
+        RemotePath::new(self.0.join(rel).to_string_lossy().into_owned())
+    }
+}
+impl Drop for TempDir {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.0);
+    }
+}
+
+fn store(tmp: &TempDir) -> FsSkillStore {
+    let fs: Arc<dyn FileSystem> = Arc::new(LocalFileSystem::new());
+    FsSkillStore::new(fs, tmp.app_data_dir())
+}
+
+fn sid(n: u128) -> SkillId {
+    SkillId::from_uuid(Uuid::from_u128(n))
+}
+
+fn skill(id: SkillId, name: &str, content: &str, scope: SkillScope) -> Skill {
+    Skill::new(id, name, MarkdownDoc::new(content), scope).unwrap()
+}
+
+#[tokio::test]
+async fn missing_index_lists_empty_in_both_scopes() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+    assert!(s.list(SkillScope::Global, &root).await.unwrap().is_empty());
+    assert!(s.list(SkillScope::Project, &root).await.unwrap().is_empty());
+}
+
+#[tokio::test]
+async fn global_roundtrip_save_get_list() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+
+    let sk = skill(sid(1), "refactor", "# Refactor workflow", SkillScope::Global);
+    s.save(&sk, &root).await.unwrap();
+
+    assert_eq!(s.get(SkillScope::Global, &root, sid(1)).await.unwrap(), sk);
+    assert_eq!(
+        s.list(SkillScope::Global, &root).await.unwrap(),
+        vec![sk.clone()]
+    );
+
+    // The Markdown landed under the global skills dir.
+    let fs = LocalFileSystem::new();
+    let bytes = fs
+        .read(&tmp.child(&format!("skills/md/{}.md", sid(1))))
+        .await
+        .unwrap();
+    assert_eq!(String::from_utf8(bytes).unwrap(), sk.content_md.as_str());
+}
+
+#[tokio::test]
+async fn project_roundtrip_lands_under_ideai() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+
+    let sk = skill(sid(1), "review", "# Review workflow", SkillScope::Project);
+    s.save(&sk, &root).await.unwrap();
+
+    assert_eq!(s.get(SkillScope::Project, &root, sid(1)).await.unwrap(), sk);
+
+    let fs = LocalFileSystem::new();
+    let bytes = fs
+        .read(&tmp.child(&format!("project/.ideai/skills/md/{}.md", sid(1))))
+        .await
+        .unwrap();
+    assert_eq!(String::from_utf8(bytes).unwrap(), sk.content_md.as_str());
+}
+
+#[tokio::test]
+async fn scopes_are_isolated() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+
+    s.save(&skill(sid(1), "g", "global body", SkillScope::Global), &root)
+        .await
+        .unwrap();
+    s.save(
+        &skill(sid(2), "p", "project body", SkillScope::Project),
+        &root,
+    )
+    .await
+    .unwrap();
+
+    // A global skill never surfaces in the project scope and vice-versa.
+    let globals = s.list(SkillScope::Global, &root).await.unwrap();
+    let projects = s.list(SkillScope::Project, &root).await.unwrap();
+    assert_eq!(globals.len(), 1);
+    assert_eq!(projects.len(), 1);
+    assert_eq!(globals[0].id, sid(1));
+    assert_eq!(projects[0].id, sid(2));
+
+    assert!(matches!(
+        s.get(SkillScope::Global, &root, sid(2)).await.unwrap_err(),
+        StoreError::NotFound
+    ));
+    assert!(matches!(
+        s.get(SkillScope::Project, &root, sid(1)).await.unwrap_err(),
+        StoreError::NotFound
+    ));
+}
+
+#[tokio::test]
+async fn save_upserts_content() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+
+    s.save(&skill(sid(1), "k", "v1", SkillScope::Global), &root)
+        .await
+        .unwrap();
+    s.save(&skill(sid(1), "k", "v2", SkillScope::Global), &root)
+        .await
+        .unwrap();
+
+    assert_eq!(
+        s.get(SkillScope::Global, &root, sid(1))
+            .await
+            .unwrap()
+            .content_md
+            .as_str(),
+        "v2"
+    );
+    assert_eq!(
+        s.list(SkillScope::Global, &root).await.unwrap().len(),
+        1,
+        "upsert, not append"
+    );
+}
+
+#[tokio::test]
+async fn delete_removes_from_index_and_is_not_found_twice() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+    s.save(&skill(sid(1), "k", "x", SkillScope::Project), &root)
+        .await
+        .unwrap();
+
+    s.delete(SkillScope::Project, &root, sid(1)).await.unwrap();
+    assert!(s.list(SkillScope::Project, &root).await.unwrap().is_empty());
+    assert!(matches!(
+        s.delete(SkillScope::Project, &root, sid(1))
+            .await
+            .unwrap_err(),
+        StoreError::NotFound
+    ));
+}
+
+#[tokio::test]
+async fn index_is_camelcase_with_content_hash() {
+    let tmp = TempDir::new();
+    let s = store(&tmp);
+    let root = tmp.project_root();
+    s.save(&skill(sid(1), "refactor", "hello", SkillScope::Global), &root)
+        .await
+        .unwrap();
+
+    let fs = LocalFileSystem::new();
+    let bytes = fs.read(&tmp.child("skills/index.json")).await.unwrap();
+    let json: serde_json::Value = serde_json::from_slice(&bytes).unwrap();
+    let entry = &json.get("skills").unwrap().as_array().unwrap()[0];
+    assert_eq!(entry.get("name").and_then(|v| v.as_str()), Some("refactor"));
+    assert!(
+        entry.get("contentHash").is_some(),
+        "camelCase contentHash present"
+    );
+    assert!(
+        entry.get("content_hash").is_none(),
+        "no snake_case leak"
+    );
+}

frontend/src/adapters/index.ts

@@ -19,6 +19,7 @@ import { TauriTerminalGateway } from "./terminal";
 import { TauriLayoutGateway } from "./layout";
 import { TauriProfileGateway } from "./profile";
 import { TauriTemplateGateway } from "./template";
+import { TauriSkillGateway } from "./skill";
 import { TauriGitGateway } from "./git";
 
 function notImplemented(what: string): never {
@@ -47,6 +48,7 @@ export function createTauriGateways(): Gateways {
     remote: new TauriRemoteGateway(),
     profile: new TauriProfileGateway(),
     template: new TauriTemplateGateway(),
+    skill: new TauriSkillGateway(),
   };
 }
 
@@ -58,5 +60,6 @@ export {
   TauriLayoutGateway,
   TauriProfileGateway,
   TauriTemplateGateway,
+  TauriSkillGateway,
   TauriGitGateway,
 };

frontend/src/adapters/mock/index.ts

@@ -23,12 +23,15 @@ import type {
   LayoutTree,
   Project,
   ProfileAvailability,
+  Skill,
+  SkillScope,
   Template,
   Unsubscribe,
 } from "@/domain";
 import type {
   AgentGateway,
   CreateAgentInput,
+  CreateSkillInput,
   CreateTemplateInput,
   Gateways,
   GitGateway,
@@ -38,6 +41,7 @@ import type {
   ProjectGateway,
   ReattachResult,
   RemoteGateway,
+  SkillGateway,
   SystemGateway,
   TemplateGateway,
   TerminalGateway,
@@ -191,6 +195,7 @@ export class MockAgentGateway implements AgentGateway {
       profileId: input.profileId,
       origin: { type: "scratch" },
       synchronized: false,
+      skills: [],
     };
     list.push(agent);
     this.contexts.set(
@@ -282,6 +287,18 @@ export class MockAgentGateway implements AgentGateway {
     return this.getAgents(projectId);
   }
 
+  /**
+   * Replaces an agent's assigned skills in-place.
+   * Used by `MockSkillGateway.assignSkill` / `unassignSkill` so both gateways
+   * share the same in-memory store.
+   */
+  _setSkills(projectId: string, agentId: string, skills: Agent["skills"]): void {
+    const list = this.getAgents(projectId);
+    const idx = list.findIndex((a) => a.id === agentId);
+    if (idx === -1) return;
+    list[idx] = { ...list[idx], skills };
+  }
+
   async launchAgent(
     projectId: string,
     agentId: string,
@@ -931,6 +948,7 @@ export class MockTemplateGateway implements TemplateGateway {
         syncedTemplateVersion: template.version,
       },
       synchronized,
+      skills: [],
     };
 
     this.agentGateway._insertAgent(projectId, agent, template.contentMd);
@@ -990,6 +1008,130 @@ export class MockTemplateGateway implements TemplateGateway {
   }
 }
 
+/**
+ * Stateful in-memory skill gateway (L12).
+ *
+ * Skills are keyed by `${scope}` (project scope is further partitioned by
+ * `projectId`, mirroring the disjoint on-disk roots). Assignment mutates the
+ * agent record held by the injected {@link MockAgentGateway}, so both gateways
+ * share one store — exactly like {@link MockTemplateGateway}.
+ */
+export class MockSkillGateway implements SkillGateway {
+  // Global skills are project-independent; project skills live under their id.
+  private global: Skill[] = [];
+  private byProject = new Map<string, Skill[]>();
+  private seq = 0;
+
+  constructor(private readonly agentGateway: MockAgentGateway) {}
+
+  private bucket(projectId: string, scope: SkillScope): Skill[] {
+    if (scope === "global") return this.global;
+    let list = this.byProject.get(projectId);
+    if (!list) {
+      list = [];
+      this.byProject.set(projectId, list);
+    }
+    return list;
+  }
+
+  async listSkills(projectId: string, scope: SkillScope): Promise<Skill[]> {
+    return structuredClone(this.bucket(projectId, scope));
+  }
+
+  async createSkill(input: CreateSkillInput): Promise<Skill> {
+    this.seq += 1;
+    const skill: Skill = {
+      id: `mock-skill-${this.seq}`,
+      name: input.name,
+      contentMd: input.content,
+      scope: input.scope,
+    };
+    this.bucket(input.projectId, input.scope).push(skill);
+    return structuredClone(skill);
+  }
+
+  async updateSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+    content: string,
+  ): Promise<Skill> {
+    const list = this.bucket(projectId, scope);
+    const idx = list.findIndex((s) => s.id === skillId);
+    if (idx === -1) {
+      const err: GatewayError = {
+        code: "NOT_FOUND",
+        message: `skill ${skillId} not found`,
+      };
+      throw err;
+    }
+    list[idx] = { ...list[idx], contentMd: content };
+    return structuredClone(list[idx]);
+  }
+
+  async deleteSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+  ): Promise<void> {
+    const list = this.bucket(projectId, scope);
+    const idx = list.findIndex((s) => s.id === skillId);
+    if (idx === -1) {
+      const err: GatewayError = {
+        code: "NOT_FOUND",
+        message: `skill ${skillId} not found`,
+      };
+      throw err;
+    }
+    list.splice(idx, 1);
+  }
+
+  async assignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+    scope: SkillScope,
+  ): Promise<void> {
+    const agent = this.agentGateway
+      ._rawAgents(projectId)
+      .find((a) => a.id === agentId);
+    if (!agent) {
+      const err: GatewayError = {
+        code: "NOT_FOUND",
+        message: `agent ${agentId} not found in project ${projectId}`,
+      };
+      throw err;
+    }
+    if (agent.skills.some((s) => s.skillId === skillId)) return; // idempotent
+    this.agentGateway._setSkills(projectId, agentId, [
+      ...agent.skills,
+      { skillId, scope },
+    ]);
+  }
+
+  async unassignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+  ): Promise<void> {
+    const agent = this.agentGateway
+      ._rawAgents(projectId)
+      .find((a) => a.id === agentId);
+    if (!agent) {
+      const err: GatewayError = {
+        code: "NOT_FOUND",
+        message: `agent ${agentId} not found in project ${projectId}`,
+      };
+      throw err;
+    }
+    this.agentGateway._setSkills(
+      projectId,
+      agentId,
+      agent.skills.filter((s) => s.skillId !== skillId),
+    );
+  }
+}
+
 /** Builds the full set of mock gateways. */
 export function createMockGateways(): Gateways {
   const agentGateway = new MockAgentGateway();
@@ -1003,6 +1145,7 @@ export function createMockGateways(): Gateways {
     remote: new MockRemoteGateway(),
     profile: new MockProfileGateway(),
     template: new MockTemplateGateway(agentGateway),
+    skill: new MockSkillGateway(agentGateway),
   };
 }
 

frontend/src/adapters/mock/mock.test.ts

@@ -12,7 +12,7 @@ import { createMockGateways, MockSystemGateway } from "./index";
 const gateways: Gateways = createMockGateways();
 
 describe("createMockGateways", () => {
-  it("exposes all nine gateways", () => {
+  it("exposes all ten gateways", () => {
     expect(Object.keys(gateways).sort()).toEqual([
       "agent",
       "git",
@@ -20,6 +20,7 @@ describe("createMockGateways", () => {
       "profile",
       "project",
       "remote",
+      "skill",
       "system",
       "template",
       "terminal",

frontend/src/adapters/skill.ts

@@ -0,0 +1,70 @@
+/**
+ * Tauri adapter for {@link SkillGateway} (L12).
+ *
+ * Commands use snake_case (Tauri convention); payload keys are camelCase
+ * (matching the backend DTO `#[serde(rename_all = "camelCase")]`), consistent
+ * with the other adapters in this directory. The `scope` value (`"global"` /
+ * `"project"`) maps directly onto the backend `SkillScope` serde enum.
+ */
+
+import { invoke } from "@tauri-apps/api/core";
+
+import type { Skill, SkillScope } from "@/domain";
+import type { CreateSkillInput, SkillGateway } from "@/ports";
+
+export class TauriSkillGateway implements SkillGateway {
+  listSkills(projectId: string, scope: SkillScope): Promise<Skill[]> {
+    return invoke<Skill[]>("list_skills", { projectId, scope });
+  }
+
+  createSkill(input: CreateSkillInput): Promise<Skill> {
+    return invoke<Skill>("create_skill", {
+      request: {
+        projectId: input.projectId,
+        name: input.name,
+        content: input.content,
+        scope: input.scope,
+      },
+    });
+  }
+
+  updateSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+    content: string,
+  ): Promise<Skill> {
+    return invoke<Skill>("update_skill", {
+      request: { projectId, scope, skillId, content },
+    });
+  }
+
+  async deleteSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+  ): Promise<void> {
+    await invoke("delete_skill", { projectId, scope, skillId });
+  }
+
+  async assignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+    scope: SkillScope,
+  ): Promise<void> {
+    await invoke("assign_skill_to_agent", {
+      request: { projectId, agentId, skillId, scope },
+    });
+  }
+
+  async unassignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+  ): Promise<void> {
+    await invoke("unassign_skill_from_agent", {
+      request: { projectId, agentId, skillId },
+    });
+  }
+}

frontend/src/domain/index.ts

@@ -236,6 +236,35 @@ export interface Agent {
   profileId: string;
   origin: AgentOrigin;
   synchronized: boolean;
+  /** Skills assigned to this agent (injected into its convention file). */
+  skills: SkillRef[];
+}
+
+// ---------------------------------------------------------------------------
+// Skills (L12) — mirror of the domain `Skill` / `SkillRef`.
+// ---------------------------------------------------------------------------
+
+/**
+ * Where a skill lives (selects its backing store): `global` skills are reusable
+ * across projects; `project` skills are specific to one project's `.ideai/`.
+ */
+export type SkillScope = "global" | "project";
+
+/**
+ * A reusable, model-agnostic workflow assignable to agents (mirror of the
+ * backend `Skill` DTO, camelCase wire format).
+ */
+export interface Skill {
+  id: string;
+  name: string;
+  contentMd: string;
+  scope: SkillScope;
+}
+
+/** A reference from an agent to one assigned skill (mirror of `SkillRef`). */
+export interface SkillRef {
+  skillId: string;
+  scope: SkillScope;
 }
 
 // ---------------------------------------------------------------------------

frontend/src/features/agents/AgentsPanel.tsx

@@ -54,6 +54,50 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
     void templateGw.listTemplates().then(setTemplates).catch(() => {});
   }
 
+  // Skills available for assignment (global + project), loaded lazily once.
+  const skillGw = gateways.skill ?? null;
+  const [skills, setSkills] = useState<import("@/domain").Skill[]>([]);
+  const [skillsLoaded, setSkillsLoaded] = useState(false);
+  const [skillToAssign, setSkillToAssign] = useState("");
+
+  async function refreshSkills() {
+    if (!skillGw) return;
+    try {
+      const [globals, projects] = await Promise.all([
+        skillGw.listSkills(projectId, "global"),
+        skillGw.listSkills(projectId, "project"),
+      ]);
+      setSkills([...projects, ...globals]);
+    } catch {
+      // Skills are optional — leave the list empty on failure.
+    }
+  }
+
+  if (!skillsLoaded && skillGw) {
+    setSkillsLoaded(true);
+    void refreshSkills();
+  }
+
+  async function handleAssignSkill() {
+    if (!skillGw || !vm.selectedAgentId || !skillToAssign) return;
+    const target = skills.find((s) => s.id === skillToAssign);
+    if (!target) return;
+    await skillGw.assignSkill(
+      projectId,
+      vm.selectedAgentId,
+      target.id,
+      target.scope,
+    );
+    setSkillToAssign("");
+    await vm.refresh();
+  }
+
+  async function handleUnassignSkill(skillId: string) {
+    if (!skillGw || !vm.selectedAgentId) return;
+    await skillGw.unassignSkill(projectId, vm.selectedAgentId, skillId);
+    await vm.refresh();
+  }
+
   // Context editor state — local copy before Save
   const [editedContext, setEditedContext] = useState(vm.context);
 
@@ -351,6 +395,79 @@ export function AgentsPanel({ projectId, projectRoot = "" }: AgentsPanelProps) {
         </div>
       )}
 
+      {/* ── Skill assignment ── */}
+      {selectedAgent && skillGw && (
+        <div className="flex flex-col gap-2 border-t border-border p-4">
+          <h4 className="text-sm font-semibold text-content">
+            Skills — {selectedAgent.name}
+          </h4>
+
+          {/* Assigned skills */}
+          {selectedAgent.skills.length === 0 ? (
+            <p className="text-xs text-muted">No skills assigned.</p>
+          ) : (
+            <ul className="flex flex-wrap gap-1.5">
+              {selectedAgent.skills.map((ref) => {
+                const name =
+                  skills.find((s) => s.id === ref.skillId)?.name ?? ref.skillId;
+                return (
+                  <li
+                    key={ref.skillId}
+                    className="flex items-center gap-1 rounded-full bg-raised px-2 py-0.5 text-xs text-content"
+                  >
+                    <span>{name}</span>
+                    <button
+                      type="button"
+                      aria-label={`unassign ${name}`}
+                      disabled={vm.busy}
+                      onClick={() => void handleUnassignSkill(ref.skillId)}
+                      className="text-faint hover:text-danger"
+                    >
+                      ✕
+                    </button>
+                  </li>
+                );
+              })}
+            </ul>
+          )}
+
+          {/* Assign selector */}
+          <div className="flex items-end gap-2">
+            <select
+              aria-label="skill to assign"
+              value={skillToAssign}
+              onChange={(e) => setSkillToAssign(e.target.value)}
+              disabled={vm.busy}
+              className={cn(
+                "h-9 min-w-0 flex-1 rounded-md bg-raised px-3 text-sm text-content",
+                "border border-border outline-none transition-colors",
+                "focus:border-primary disabled:cursor-not-allowed disabled:opacity-50",
+              )}
+            >
+              <option value="">— assign a skill —</option>
+              {skills
+                .filter(
+                  (s) =>
+                    !selectedAgent.skills.some((r) => r.skillId === s.id),
+                )
+                .map((s) => (
+                  <option key={s.id} value={s.id}>
+                    {s.name} ({s.scope})
+                  </option>
+                ))}
+            </select>
+            <Button
+              variant="primary"
+              aria-label="assign skill"
+              disabled={vm.busy || !skillToAssign}
+              onClick={() => void handleAssignSkill()}
+            >
+              Assign
+            </Button>
+          </div>
+        </div>
+      )}
+
       {/* ── Context editor ── */}
       {selectedAgent && (
         <div className="flex flex-col gap-2 border-t border-border p-4">

frontend/src/features/projects/ProjectsView.tsx

@@ -34,17 +34,19 @@ import type { LayoutInfo } from "@/domain";
 import { LayoutGrid, LayoutTabs } from "@/features/layout";
 import { AgentsPanel } from "@/features/agents";
 import { TemplatesPanel } from "@/features/templates";
+import { SkillsPanel } from "@/features/skills";
 import { GitPanel, GitGraphView } from "@/features/git";
 import { Button, Input, Panel, Tabs, cn } from "@/shared";
 import { useGateways } from "@/app/di";
 import { useProjects } from "./useProjects";
 
-type SidebarTab = "projects" | "agents" | "templates" | "git";
+type SidebarTab = "projects" | "agents" | "templates" | "skills" | "git";
 
 const SIDEBAR_TABS: { id: SidebarTab; label: string }[] = [
   { id: "projects", label: "Projects" },
   { id: "agents", label: "Agents" },
   { id: "templates", label: "Templates" },
+  { id: "skills", label: "Skills" },
   { id: "git", label: "Git" },
 ];
 
@@ -259,6 +261,14 @@ export function ProjectsView() {
               <p className="text-sm text-muted">Open a project to manage templates.</p>
             )}
 
+            {/* Skills panel */}
+            {sidebarTab === "skills" && active && (
+              <SkillsPanel projectId={active.id} />
+            )}
+            {sidebarTab === "skills" && !active && (
+              <p className="text-sm text-muted">Open a project to manage skills.</p>
+            )}
+
             {/* Git panel */}
             {sidebarTab === "git" && active && (
               <GitPanel projectId={active.id} />

frontend/src/features/skills/SkillEditor.tsx

@@ -0,0 +1,207 @@
+/**
+ * `SkillEditor` — a fullscreen overlay for creating or editing skills (L12).
+ * Rendered on top of the rest of the UI (`fixed inset-0`).
+ *
+ * Provides:
+ * - Name field and scope selector (create-mode only; scope is fixed in edit-mode)
+ * - Two tabs: "Edit" (textarea) and "Preview" (react-markdown)
+ * - Save (create/update) and Cancel/Close buttons
+ *
+ * Pure presentation: all mutations are delegated to the callbacks supplied by
+ * the parent (`SkillsPanel`). Styled with `@/shared`; no inline styles.
+ */
+
+import { useState } from "react";
+import ReactMarkdown from "react-markdown";
+import remarkGfm from "remark-gfm";
+
+import type { Skill, SkillScope } from "@/domain";
+import { Button, Input, cn } from "@/shared";
+
+export interface SkillEditorProps {
+  /**
+   * When set, the editor is in edit-mode for the given skill; otherwise it is in
+   * create-mode (all fields start empty).
+   */
+  skill?: Skill | null;
+  /** Called when the user submits the form. */
+  onSave: (name: string, content: string, scope: SkillScope) => Promise<void>;
+  /** Called when the user cancels / closes the overlay. */
+  onClose: () => void;
+  /** Whether a save operation is in flight. */
+  busy?: boolean;
+}
+
+type EditorTab = "edit" | "preview";
+
+export function SkillEditor({
+  skill,
+  onSave,
+  onClose,
+  busy = false,
+}: SkillEditorProps) {
+  const [name, setName] = useState(skill?.name ?? "");
+  const [content, setContent] = useState(skill?.contentMd ?? "");
+  const [scope, setScope] = useState<SkillScope>(skill?.scope ?? "project");
+  const [tab, setTab] = useState<EditorTab>("edit");
+
+  const editing = skill != null;
+  const canSave = name.trim().length > 0 && content.trim().length > 0 && !busy;
+
+  async function handleSubmit(e: React.FormEvent) {
+    e.preventDefault();
+    if (!canSave) return;
+    await onSave(name.trim(), content, scope);
+  }
+
+  return (
+    <div
+      className="fixed inset-0 z-50 flex flex-col bg-canvas"
+      role="dialog"
+      aria-modal="true"
+      aria-label="skill editor"
+    >
+      {/* ── Header bar ── */}
+      <div className="flex shrink-0 items-center justify-between border-b border-border bg-surface px-4 py-3">
+        <h2 className="text-sm font-semibold text-content">
+          {editing ? `Edit skill — ${skill.name}` : "New skill"}
+        </h2>
+        <Button
+          type="button"
+          variant="ghost"
+          aria-label="close skill editor"
+          onClick={onClose}
+          disabled={busy}
+        >
+          ✕
+        </Button>
+      </div>
+
+      {/* ── Form body ── */}
+      <form
+        onSubmit={(e) => void handleSubmit(e)}
+        className="flex flex-1 flex-col gap-0 overflow-hidden"
+      >
+        {/* ── Meta fields ── */}
+        <div className="flex shrink-0 flex-wrap items-end gap-3 border-b border-border px-4 py-3">
+          <div className="flex min-w-0 flex-1 flex-col gap-1">
+            <label htmlFor="se-name" className="text-xs font-medium text-muted">
+              Name
+            </label>
+            <Input
+              id="se-name"
+              aria-label="skill name"
+              placeholder="My skill"
+              value={name}
+              onChange={(e) => setName(e.target.value)}
+              disabled={busy}
+              className="min-w-48"
+            />
+          </div>
+
+          <div className="flex min-w-0 flex-col gap-1">
+            <label htmlFor="se-scope" className="text-xs font-medium text-muted">
+              Scope
+            </label>
+            <select
+              id="se-scope"
+              aria-label="skill scope"
+              value={scope}
+              onChange={(e) => setScope(e.target.value as SkillScope)}
+              disabled={busy || editing}
+              className={cn(
+                "h-9 w-full rounded-md bg-raised px-3 text-sm text-content",
+                "border border-border outline-none transition-colors",
+                "focus:border-primary disabled:cursor-not-allowed disabled:opacity-50",
+              )}
+            >
+              <option value="project">Project</option>
+              <option value="global">Global</option>
+            </select>
+          </div>
+        </div>
+
+        {/* ── Tab strip ── */}
+        <div className="flex shrink-0 items-center gap-0 border-b border-border px-4">
+          {(["edit", "preview"] as EditorTab[]).map((t) => (
+            <button
+              key={t}
+              type="button"
+              role="tab"
+              aria-label={t === "edit" ? "Edit" : "Preview"}
+              aria-selected={tab === t}
+              onClick={() => setTab(t)}
+              className={cn(
+                "px-4 py-2 text-sm font-medium capitalize transition-colors",
+                tab === t
+                  ? "border-b-2 border-primary text-content"
+                  : "text-muted hover:text-content",
+              )}
+            >
+              {t === "edit" ? "Edit" : "Preview"}
+            </button>
+          ))}
+        </div>
+
+        {/* ── Edit / Preview pane ── */}
+        <div className="flex flex-1 flex-col overflow-hidden px-4 py-3">
+          {tab === "edit" ? (
+            <textarea
+              aria-label="skill content"
+              value={content}
+              onChange={(e) => setContent(e.target.value)}
+              disabled={busy}
+              className={cn(
+                "flex-1 w-full rounded-md bg-raised px-3 py-2 text-sm text-content font-mono",
+                "border border-border outline-none transition-colors resize-none",
+                "focus:border-primary placeholder:text-faint",
+                "disabled:cursor-not-allowed disabled:opacity-50",
+              )}
+              placeholder="# Skill workflow&#10;&#10;..."
+            />
+          ) : (
+            <div
+              className={cn(
+                "flex-1 overflow-auto rounded-md border border-border bg-raised px-6 py-4",
+                "prose prose-sm prose-invert max-w-none",
+                "[&_h1]:text-content [&_h2]:text-content [&_h3]:text-content",
+                "[&_p]:text-content/90 [&_li]:text-content/90",
+                "[&_code]:bg-canvas [&_code]:text-primary [&_code]:rounded [&_code]:px-1",
+                "[&_pre]:bg-canvas [&_pre]:border [&_pre]:border-border [&_pre]:rounded-md",
+                "[&_a]:text-primary [&_a:hover]:underline",
+                "[&_blockquote]:border-l-2 [&_blockquote]:border-primary [&_blockquote]:text-muted",
+                "[&_hr]:border-border",
+              )}
+            >
+              {content.trim() ? (
+                <ReactMarkdown remarkPlugins={[remarkGfm]}>
+                  {content}
+                </ReactMarkdown>
+              ) : (
+                <p className="text-sm text-muted italic">
+                  Nothing to preview yet.
+                </p>
+              )}
+            </div>
+          )}
+        </div>
+
+        {/* ── Footer ── */}
+        <div className="flex shrink-0 items-center justify-end gap-2 border-t border-border px-4 py-3">
+          <Button type="button" variant="ghost" onClick={onClose} disabled={busy}>
+            Cancel
+          </Button>
+          <Button
+            type="submit"
+            variant="primary"
+            aria-label="Save skill"
+            disabled={!canSave}
+            loading={busy}
+          >
+            Save
+          </Button>
+        </div>
+      </form>
+    </div>
+  );
+}

frontend/src/features/skills/SkillsPanel.tsx

@@ -0,0 +1,154 @@
+/**
+ * `SkillsPanel` — feature component for skill management (L12).
+ *
+ * Pure presentation: all behaviour comes from {@link useSkills}. Styled with
+ * `@/shared` design system tokens; no inline styles.
+ *
+ * Provides, per scope (Global + Project):
+ * - Skill list (name + scope)
+ * - "New skill" button that opens {@link SkillEditor} in create-mode
+ * - Per-skill "Edit" (opens the editor in edit-mode) and "Delete"
+ *
+ * Skills are assigned to agents from the `AgentsPanel`, not here — this panel is
+ * the authoring surface only ("no direct invoke": a skill is never run from the
+ * UI, only injected into an agent's convention file at activation).
+ */
+
+import { useState } from "react";
+
+import type { Skill, SkillScope } from "@/domain";
+import { Button, Panel, Spinner } from "@/shared";
+import { SkillEditor } from "./SkillEditor";
+import { useSkills } from "./useSkills";
+
+export interface SkillsPanelProps {
+  /** The project whose skills to manage. */
+  projectId: string;
+}
+
+/** Editor open-state: "create" or edit-mode for a specific skill. */
+type EditorState = { mode: "create" } | { mode: "edit"; skill: Skill };
+
+export function SkillsPanel({ projectId }: SkillsPanelProps) {
+  const vm = useSkills(projectId);
+
+  const [editorState, setEditorState] = useState<EditorState | null>(null);
+  const [editorBusy, setEditorBusy] = useState(false);
+
+  async function handleSave(name: string, content: string, scope: SkillScope) {
+    if (!editorState) return;
+    setEditorBusy(true);
+    try {
+      if (editorState.mode === "create") {
+        await vm.createSkill({ name, content, scope });
+      } else {
+        await vm.updateSkill(editorState.skill.scope, editorState.skill.id, content);
+      }
+      setEditorState(null);
+    } finally {
+      setEditorBusy(false);
+    }
+  }
+
+  function renderList(scope: SkillScope, skills: Skill[]) {
+    return (
+      <div className="p-4">
+        {skills.length === 0 ? (
+          <p className="text-sm text-muted">No {scope} skills yet.</p>
+        ) : (
+          <ul className="flex flex-col divide-y divide-border">
+            {skills.map((s) => (
+              <li
+                key={s.id}
+                className="flex items-center justify-between gap-3 py-3 first:pt-0 last:pb-0"
+              >
+                <span className="min-w-0 font-medium text-content">{s.name}</span>
+                <div className="flex items-center gap-1.5 shrink-0">
+                  <Button
+                    size="sm"
+                    variant="ghost"
+                    aria-label={`edit skill ${s.name}`}
+                    disabled={vm.busy}
+                    onClick={() => setEditorState({ mode: "edit", skill: s })}
+                  >
+                    Edit
+                  </Button>
+                  <Button
+                    size="sm"
+                    variant="ghost"
+                    aria-label={`delete skill ${s.name}`}
+                    disabled={vm.busy}
+                    onClick={() => void vm.deleteSkill(s.scope, s.id)}
+                    className="text-danger hover:text-danger"
+                  >
+                    Delete
+                  </Button>
+                </div>
+              </li>
+            ))}
+          </ul>
+        )}
+      </div>
+    );
+  }
+
+  return (
+    <>
+      {/* ── Fullscreen skill editor overlay ── */}
+      {editorState !== null && (
+        <SkillEditor
+          skill={editorState.mode === "edit" ? editorState.skill : null}
+          onSave={handleSave}
+          onClose={() => setEditorState(null)}
+          busy={editorBusy}
+        />
+      )}
+
+      <Panel title="Skills" className="flex flex-col gap-0">
+        {vm.error && (
+          <p
+            role="alert"
+            className="mx-4 mt-3 rounded-md border border-danger/40 bg-danger/10 px-3 py-2 text-sm text-danger"
+          >
+            {vm.error}
+          </p>
+        )}
+
+        {/* ── Create button ── */}
+        <div className="flex items-center justify-between border-b border-border px-4 py-3">
+          <h4 className="text-xs font-semibold uppercase tracking-wide text-faint">
+            Skills
+          </h4>
+          <div className="flex items-center gap-2">
+            {vm.busy && <Spinner size={14} />}
+            <Button
+              type="button"
+              variant="primary"
+              aria-label="create skill"
+              disabled={vm.busy}
+              onClick={() => setEditorState({ mode: "create" })}
+            >
+              New skill
+            </Button>
+          </div>
+        </div>
+
+        {/* ── Project skills ── */}
+        <div className="border-b border-border px-4 pt-3">
+          <h5 className="text-xs font-semibold uppercase tracking-wide text-faint">
+            Project
+          </h5>
+        </div>
+        {renderList("project", vm.projectSkills)}
+
+        {/* ── Global skills ── */}
+        <div className="border-y border-border px-4 pt-3">
+          <h5 className="text-xs font-semibold uppercase tracking-wide text-faint">
+            Global
+          </h5>
+        </div>
+        {renderList("global", vm.globalSkills)}
+      </Panel>
+    </>
+  );
+}

frontend/src/features/skills/index.ts

@@ -0,0 +1,6 @@
+/** Public surface of the skills feature (L12). */
+export { SkillsPanel } from "./SkillsPanel";
+export type { SkillsPanelProps } from "./SkillsPanel";
+export { SkillEditor } from "./SkillEditor";
+export { useSkills } from "./useSkills";
+export type { SkillsViewModel } from "./useSkills";

frontend/src/features/skills/skills.test.tsx

@@ -0,0 +1,297 @@
+/**
+ * L12 — skills feature + agent assignment, wired to the stateful
+ * `MockSkillGateway` (sharing a `MockAgentGateway`) via the real `DIProvider`.
+ *
+ * Covers:
+ * - createSkill (project + global) → skill appears under the right scope
+ * - updateSkill → content persisted in the gateway
+ * - deleteSkill → skill removed from the list
+ * - assignSkill / unassignSkill in AgentsPanel → reflected on the agent record
+ * - guardrail "no direct invoke": SkillsPanel never offers a run/launch action
+ *
+ * Also includes MockSkillGateway unit tests.
+ */
+
+import { describe, it, expect } from "vitest";
+import { render, screen, waitFor, fireEvent } from "@testing-library/react";
+
+import {
+  MockAgentGateway,
+  MockProfileGateway,
+  MockSkillGateway,
+} from "@/adapters/mock";
+import type { Gateways } from "@/ports";
+import { DIProvider } from "@/app/di";
+import { SkillsPanel } from "./SkillsPanel";
+import { AgentsPanel } from "@/features/agents/AgentsPanel";
+
+const PROJECT_ID = "proj-skill-test";
+
+function renderSkillsPanel(agent?: MockAgentGateway, skill?: MockSkillGateway) {
+  const a = agent ?? new MockAgentGateway();
+  const sk = skill ?? new MockSkillGateway(a);
+  const gateways = { agent: a, skill: sk } as unknown as Gateways;
+  return {
+    agent: a,
+    skill: sk,
+    ...render(
+      <DIProvider gateways={gateways}>
+        <SkillsPanel projectId={PROJECT_ID} />
+      </DIProvider>,
+    ),
+  };
+}
+
+function renderAgentsPanel(agent: MockAgentGateway, skill: MockSkillGateway) {
+  const profile = new MockProfileGateway();
+  const gateways = { agent, profile, skill } as unknown as Gateways;
+  return render(
+    <DIProvider gateways={gateways}>
+      <AgentsPanel projectId={PROJECT_ID} projectRoot="/tmp/proj" />
+    </DIProvider>,
+  );
+}
+
+async function waitForSkillsIdle() {
+  await waitFor(() => {
+    expect(screen.getByRole("button", { name: "create skill" })).toBeTruthy();
+  });
+}
+
+/** Opens the SkillEditor, fills it, and saves. */
+async function createSkill(
+  name: string,
+  content = "# Workflow",
+  scope: "project" | "global" = "project",
+) {
+  await waitForSkillsIdle();
+  fireEvent.click(screen.getByRole("button", { name: "create skill" }));
+  await waitFor(() => expect(screen.getByLabelText("skill name")).toBeTruthy());
+  fireEvent.change(screen.getByLabelText("skill name"), {
+    target: { value: name },
+  });
+  fireEvent.change(screen.getByLabelText("skill content"), {
+    target: { value: content },
+  });
+  fireEvent.change(screen.getByLabelText("skill scope"), {
+    target: { value: scope },
+  });
+  fireEvent.click(screen.getByRole("button", { name: "Save skill" }));
+}
+
+// ---------------------------------------------------------------------------
+// SkillsPanel feature tests
+// ---------------------------------------------------------------------------
+
+describe("SkillsPanel (with MockSkillGateway)", () => {
+  it("shows empty state for both scopes initially", async () => {
+    renderSkillsPanel();
+    await waitForSkillsIdle();
+    expect(screen.getByText("No project skills yet.")).toBeTruthy();
+    expect(screen.getByText("No global skills yet.")).toBeTruthy();
+  });
+
+  it("creating a project skill adds it to the list", async () => {
+    const { skill } = renderSkillsPanel();
+    await createSkill("Refactor", "## steps", "project");
+    await screen.findByText("Refactor");
+    const projects = await skill.listSkills(PROJECT_ID, "project");
+    expect(projects).toHaveLength(1);
+    expect(projects[0].name).toBe("Refactor");
+  });
+
+  it("creating a global skill stores it under the global scope", async () => {
+    const { skill } = renderSkillsPanel();
+    await createSkill("Review", "## global", "global");
+    await screen.findByText("Review");
+    expect(await skill.listSkills(PROJECT_ID, "global")).toHaveLength(1);
+    expect(await skill.listSkills(PROJECT_ID, "project")).toHaveLength(0);
+  });
+
+  it("Save is disabled when name or content is empty", async () => {
+    renderSkillsPanel();
+    await waitForSkillsIdle();
+    fireEvent.click(screen.getByRole("button", { name: "create skill" }));
+    await waitFor(() =>
+      expect(screen.getByRole("button", { name: "Save skill" })).toBeTruthy(),
+    );
+    const save = screen.getByRole("button", {
+      name: "Save skill",
+    }) as HTMLButtonElement;
+    expect(save.disabled).toBe(true);
+  });
+
+  it("editing a skill persists the new content", async () => {
+    const { skill } = renderSkillsPanel();
+    await createSkill("Editable", "old", "project");
+    await screen.findByText("Editable");
+
+    fireEvent.click(screen.getByRole("button", { name: "edit skill Editable" }));
+    await waitFor(() =>
+      expect(screen.getByLabelText("skill content")).toBeTruthy(),
+    );
+    fireEvent.change(screen.getByLabelText("skill content"), {
+      target: { value: "new content" },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "Save skill" }));
+
+    await waitFor(async () => {
+      const list = await skill.listSkills(PROJECT_ID, "project");
+      expect(list[0].contentMd).toBe("new content");
+    });
+  });
+
+  it("deleting a skill removes it from the list", async () => {
+    renderSkillsPanel();
+    await createSkill("ToDelete", "x", "project");
+    await screen.findByText("ToDelete");
+    fireEvent.click(
+      screen.getByRole("button", { name: "delete skill ToDelete" }),
+    );
+    await waitFor(() => expect(screen.queryByText("ToDelete")).toBeNull());
+  });
+
+  it("guardrail: never offers a run/launch action for a skill (no direct invoke)", async () => {
+    renderSkillsPanel();
+    await createSkill("Plain", "x", "project");
+    await screen.findByText("Plain");
+    // Only Edit/Delete are exposed; nothing that would "run" the skill.
+    expect(screen.queryByRole("button", { name: /^run/i })).toBeNull();
+    expect(screen.queryByRole("button", { name: /^launch/i })).toBeNull();
+    expect(screen.queryByRole("button", { name: /invoke/i })).toBeNull();
+  });
+});
+
+// ---------------------------------------------------------------------------
+// Assignment integration (AgentsPanel)
+// ---------------------------------------------------------------------------
+
+describe("Skill assignment (AgentsPanel + MockSkillGateway)", () => {
+  it("assigns a skill to the selected agent and shows it as a chip", async () => {
+    const agent = new MockAgentGateway();
+    const skill = new MockSkillGateway(agent);
+    const created = await agent.createAgent(PROJECT_ID, {
+      name: "Worker",
+      profileId: "p1",
+    });
+    await skill.createSkill({
+      projectId: PROJECT_ID,
+      name: "Deploy",
+      content: "## deploy",
+      scope: "project",
+    });
+
+    renderAgentsPanel(agent, skill);
+    await waitFor(() => expect(screen.getByLabelText("agent name")).toBeTruthy());
+
+    // Select the agent
+    fireEvent.click(screen.getByText("Worker"));
+    await waitFor(() =>
+      expect(screen.getByLabelText("skill to assign")).toBeTruthy(),
+    );
+
+    // Choose the skill and assign
+    const sk = (await skill.listSkills(PROJECT_ID, "project"))[0];
+    fireEvent.change(screen.getByLabelText("skill to assign"), {
+      target: { value: sk.id },
+    });
+    fireEvent.click(screen.getByRole("button", { name: "assign skill" }));
+
+    // The agent record now carries the skill ref
+    await waitFor(async () => {
+      const agents = await agent.listAgents(PROJECT_ID);
+      const a = agents.find((x) => x.id === created.id)!;
+      expect(a.skills.map((s) => s.skillId)).toContain(sk.id);
+    });
+    // Chip with an unassign control appears
+    expect(screen.getByRole("button", { name: "unassign Deploy" })).toBeTruthy();
+  });
+
+  it("unassigns a skill from the agent", async () => {
+    const agent = new MockAgentGateway();
+    const skill = new MockSkillGateway(agent);
+    const a = await agent.createAgent(PROJECT_ID, {
+      name: "Worker2",
+      profileId: "p1",
+    });
+    const sk = await skill.createSkill({
+      projectId: PROJECT_ID,
+      name: "Cleanup",
+      content: "## cleanup",
+      scope: "global",
+    });
+    await skill.assignSkill(PROJECT_ID, a.id, sk.id, sk.scope);
+
+    renderAgentsPanel(agent, skill);
+    await waitFor(() => expect(screen.getByLabelText("agent name")).toBeTruthy());
+    fireEvent.click(screen.getByText("Worker2"));
+
+    await waitFor(() =>
+      expect(
+        screen.getByRole("button", { name: "unassign Cleanup" }),
+      ).toBeTruthy(),
+    );
+    fireEvent.click(screen.getByRole("button", { name: "unassign Cleanup" }));
+
+    await waitFor(async () => {
+      const agents = await agent.listAgents(PROJECT_ID);
+      expect(agents.find((x) => x.id === a.id)!.skills).toHaveLength(0);
+    });
+  });
+});
+
+// ---------------------------------------------------------------------------
+// MockSkillGateway unit tests
+// ---------------------------------------------------------------------------
+
+describe("MockSkillGateway (unit)", () => {
+  it("scopes are isolated: a project skill never appears in global and vice-versa", async () => {
+    const gw = new MockSkillGateway(new MockAgentGateway());
+    await gw.createSkill({
+      projectId: "p",
+      name: "P",
+      content: "x",
+      scope: "project",
+    });
+    await gw.createSkill({
+      projectId: "p",
+      name: "G",
+      content: "y",
+      scope: "global",
+    });
+    expect(await gw.listSkills("p", "project")).toHaveLength(1);
+    expect(await gw.listSkills("p", "global")).toHaveLength(1);
+    expect((await gw.listSkills("p", "project"))[0].name).toBe("P");
+    expect((await gw.listSkills("p", "global"))[0].name).toBe("G");
+  });
+
+  it("updateSkill throws NOT_FOUND for unknown skill", async () => {
+    const gw = new MockSkillGateway(new MockAgentGateway());
+    await expect(
+      gw.updateSkill("p", "project", "ghost", "x"),
+    ).rejects.toMatchObject({ code: "NOT_FOUND" });
+  });
+
+  it("assignSkill is idempotent (no duplicate refs)", async () => {
+    const agentGw = new MockAgentGateway();
+    const gw = new MockSkillGateway(agentGw);
+    const a = await agentGw.createAgent("p", { name: "A", profileId: "p1" });
+    const s = await gw.createSkill({
+      projectId: "p",
+      name: "S",
+      content: "x",
+      scope: "project",
+    });
+    await gw.assignSkill("p", a.id, s.id, s.scope);
+    await gw.assignSkill("p", a.id, s.id, s.scope);
+    const agents = await agentGw.listAgents("p");
+    expect(agents[0].skills).toHaveLength(1);
+  });
+
+  it("assignSkill throws NOT_FOUND for unknown agent", async () => {
+    const gw = new MockSkillGateway(new MockAgentGateway());
+    await expect(
+      gw.assignSkill("p", "ghost", "s", "project"),
+    ).rejects.toMatchObject({ code: "NOT_FOUND" });
+  });
+});

frontend/src/features/skills/useSkills.ts

@@ -0,0 +1,145 @@
+/**
+ * `useSkills` — view-model hook for the skills feature (L12).
+ *
+ * Owns the skill lists for both scopes (`global` + `project`) of one project and
+ * the CRUD actions. Consumes {@link SkillGateway} exclusively; never touches
+ * `invoke()` or `@tauri-apps/api`, keeping the component layer testable with
+ * mock gateways (ARCHITECTURE §1.3).
+ */
+
+import { useCallback, useEffect, useState } from "react";
+
+import type { GatewayError, Skill, SkillScope } from "@/domain";
+import type { CreateSkillInput } from "@/ports";
+import { useGateways } from "@/app/di";
+
+/** What the skills UI needs from this hook. */
+export interface SkillsViewModel {
+  /** Global skills (reusable across projects). */
+  globalSkills: Skill[];
+  /** Project-scoped skills. */
+  projectSkills: Skill[];
+  /** Last error message, or `null`. */
+  error: string | null;
+  /** Whether a request is in flight. */
+  busy: boolean;
+  /** Reloads both scope lists. */
+  refresh: () => Promise<void>;
+  /** Creates a new skill and refreshes its scope's list. */
+  createSkill: (input: Omit<CreateSkillInput, "projectId">) => Promise<void>;
+  /** Updates the content of an existing skill. */
+  updateSkill: (
+    scope: SkillScope,
+    skillId: string,
+    content: string,
+  ) => Promise<void>;
+  /** Deletes a skill by id from its scope. */
+  deleteSkill: (scope: SkillScope, skillId: string) => Promise<void>;
+}
+
+function describe(e: unknown): string {
+  if (e && typeof e === "object" && "message" in e) {
+    return String((e as GatewayError).message);
+  }
+  return String(e);
+}
+
+export function useSkills(projectId: string): SkillsViewModel {
+  const { skill } = useGateways();
+
+  const [globalSkills, setGlobalSkills] = useState<Skill[]>([]);
+  const [projectSkills, setProjectSkills] = useState<Skill[]>([]);
+  const [error, setError] = useState<string | null>(null);
+  const [busy, setBusy] = useState(false);
+
+  const refresh = useCallback(async () => {
+    if (!projectId) return;
+    setBusy(true);
+    setError(null);
+    try {
+      const [globals, projects] = await Promise.all([
+        skill.listSkills(projectId, "global"),
+        skill.listSkills(projectId, "project"),
+      ]);
+      setGlobalSkills(globals);
+      setProjectSkills(projects);
+    } catch (e) {
+      setError(describe(e));
+    } finally {
+      setBusy(false);
+    }
+  }, [skill, projectId]);
+
+  useEffect(() => {
+    void refresh();
+  }, [refresh]);
+
+  const setter = (scope: SkillScope) =>
+    scope === "global" ? setGlobalSkills : setProjectSkills;
+
+  const createSkill = useCallback(
+    async (input: Omit<CreateSkillInput, "projectId">) => {
+      setBusy(true);
+      setError(null);
+      try {
+        const created = await skill.createSkill({ ...input, projectId });
+        setter(input.scope)((prev) => [...prev, created]);
+      } catch (e) {
+        setError(describe(e));
+      } finally {
+        setBusy(false);
+      }
+    },
+    [skill, projectId],
+  );
+
+  const updateSkill = useCallback(
+    async (scope: SkillScope, skillId: string, content: string) => {
+      setBusy(true);
+      setError(null);
+      try {
+        const updated = await skill.updateSkill(
+          projectId,
+          scope,
+          skillId,
+          content,
+        );
+        setter(scope)((prev) =>
+          prev.map((s) => (s.id === skillId ? updated : s)),
+        );
+      } catch (e) {
+        setError(describe(e));
+      } finally {
+        setBusy(false);
+      }
+    },
+    [skill, projectId],
+  );
+
+  const deleteSkill = useCallback(
+    async (scope: SkillScope, skillId: string) => {
+      setBusy(true);
+      setError(null);
+      try {
+        await skill.deleteSkill(projectId, scope, skillId);
+        setter(scope)((prev) => prev.filter((s) => s.id !== skillId));
+      } catch (e) {
+        setError(describe(e));
+      } finally {
+        setBusy(false);
+      }
+    },
+    [skill, projectId],
+  );
+
+  return {
+    globalSkills,
+    projectSkills,
+    error,
+    busy,
+    refresh,
+    createSkill,
+    updateSkill,
+    deleteSkill,
+  };
+}

frontend/src/ports/index.ts

@@ -25,6 +25,8 @@ import type {
   LayoutTree,
   Project,
   ProfileAvailability,
+  Skill,
+  SkillScope,
   Template,
   Unsubscribe,
 } from "@/domain";
@@ -260,6 +262,53 @@ export interface TemplateGateway {
   ): Promise<{ synced: boolean; version: number | null }>;
 }
 
+/** Input for {@link SkillGateway.createSkill}. */
+export interface CreateSkillInput {
+  /** Owning project (resolved to a root; ignored on disk for `global`). */
+  projectId: string;
+  name: string;
+  content: string;
+  scope: SkillScope;
+}
+
+/**
+ * Skills (L12): CRUD for reusable, model-agnostic workflows in either scope, and
+ * agent↔skill assignment. Assigned skills are injected into the agent's
+ * convention file at activation (handled backend-side, ARCHITECTURE §14.2).
+ */
+export interface SkillGateway {
+  /** Lists the skills in one scope for the given project. */
+  listSkills(projectId: string, scope: SkillScope): Promise<Skill[]>;
+  /** Creates a new skill; returns the created skill. */
+  createSkill(input: CreateSkillInput): Promise<Skill>;
+  /** Updates a skill's content; returns the updated skill. */
+  updateSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+    content: string,
+  ): Promise<Skill>;
+  /** Deletes a skill by id from its scope's store. */
+  deleteSkill(
+    projectId: string,
+    scope: SkillScope,
+    skillId: string,
+  ): Promise<void>;
+  /** Assigns a skill to an agent (idempotent). */
+  assignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+    scope: SkillScope,
+  ): Promise<void>;
+  /** Unassigns a skill from an agent (idempotent). */
+  unassignSkill(
+    projectId: string,
+    agentId: string,
+    skillId: string,
+  ): Promise<void>;
+}
+
 /**
  * AI profiles & first-run (L5). Drives the first-run wizard and profile
  * management: the pre-filled reference catalogue, detection of installed CLIs,
@@ -296,4 +345,5 @@ export interface Gateways {
   remote: RemoteGateway;
   profile: ProfileGateway;
   template: TemplateGateway;
+  skill: SkillGateway;
 }