fix(chat): réattache persistante CLI custom et rendu tools/MCP/progress enrichi (#188)

Corrige la perte de session à la navigation: le démontage du CustomAgentChatView
appelait close_agent_session (destructeur) au lieu de simplement détacher le
transport. Désormais:

- nouvelle commande Tauri detach_agent_chat (+ ChatBridge::detach) qui libère le
  canal sans tuer la session ni le scrollback retenu; distinct de
  close_agent_session qui reste le close destructeur explicite;
- le frontend appelle detachAgentChat à l'unmount puis restore sa vue depuis un
  cache de session (turns + chunkCount) à la réattache;
- message « Reprise effectuée: N événements rattrapés… » quand la réattache
  rejoue plus de chunks que le cache local n'en avait conservé.

Enrichit le rendu tools/MCP/progress:

- ProgressSettler (chat bridge) émet un progress completed synthétique quand un
  spinner reste ouvert (nouvelle entité progress, chunk text/final/error): fini
  les spinners fantômes;
- les adapters claude/codex/opencode/openai_compat extraient un aperçu du
  payload (arguments/input/command/message/params) attaché au progress;
- bounded_reply_progress_preview (domain) garde les 4 premières lignes non
  vides, normalisation CR/LF;
- previewText (frontend) multiligne whitespace-pre-wrap, source/nativeEvent
  affichés sous le titre; suppression du flag settled et du Spinner inline
  devenus redondants (l'état est porté par le stage + le settler).

Tests: detach_agent_chat gateway (Tauri + mock), ProgressSettler, bornage
reply_progress, item_preview/tool_preview par adapter, réattache avec cache et
notice de rattrapage.

crates/app-tauri/src/chat.rs

@@ -34,7 +34,7 @@ use domain::ports::{
     ReplyEvent, ReplyProgress, ReplyProgressKind, ReplyProgressSource, ReplyProgressStage,
 };
 
-use crate::dto::ReplyChunk;
+use crate::dto::{ReplyChunk, ReplyProgressDto, ReplyProgressKindDto, ReplyProgressStageDto};
 use crate::stream::TauriChannelSink;
 
 /// Maximum number of recent chat chunks retained for transport reattach replay.
@@ -110,6 +110,13 @@ impl ChatBridge {
         self.inner.unregister(session);
     }
 
+    /// Detaches the current output channel while preserving the live session's
+    /// retained scrollback. This is the view-unmount path; it is intentionally
+    /// distinct from [`unregister`](Self::unregister), which is the real close.
+    pub fn detach(&self, session: &SessionId) {
+        self.inner.detach(session);
+    }
+
     /// Detaches a session's channel **only if** `gen` is still the current
     /// generation, leaving the scrollback intact. A pump calls this when its turn
     /// stream ends: if the session was re-attached meanwhile (newer generation),
@@ -136,6 +143,22 @@ impl ChatBridge {
         self.inner.send_output(session, chunk)
     }
 
+    /// Sends `chunk`, first completing any previous running progress entity when
+    /// the next chunk proves that another process/tool/MCP has taken over.
+    pub fn send_output_settled(
+        &self,
+        session: &SessionId,
+        settler: &mut ProgressSettler,
+        chunk: ReplyChunk,
+    ) -> bool {
+        let mut delivered = true;
+        if let Some(completed) = settler.before(&chunk) {
+            delivered &= self.send_output(session, completed);
+        }
+        let current_delivered = self.send_output(session, chunk);
+        delivered && current_delivered
+    }
+
     /// Number of currently-tracked sessions (handy for tests/diagnostics).
     #[must_use]
     pub fn active_sessions(&self) -> usize {
@@ -143,6 +166,86 @@ impl ChatBridge {
     }
 }
 
+/// Tracks one running progress entity for a chat stream and emits a synthetic
+/// `completed` update when subsequent activity makes the previous spinner stale.
+#[derive(Default)]
+pub struct ProgressSettler {
+    active: Option<ReplyProgressDto>,
+}
+
+impl ProgressSettler {
+    /// Completes the currently active progress entity, if any.
+    pub fn finish(&mut self) -> Option<ReplyChunk> {
+        self.complete_active()
+    }
+
+    fn before(&mut self, chunk: &ReplyChunk) -> Option<ReplyChunk> {
+        match chunk {
+            ReplyChunk::Progress { progress } => self.before_progress(progress),
+            ReplyChunk::TextDelta { .. }
+            | ReplyChunk::ToolActivity { .. }
+            | ReplyChunk::Final { .. }
+            | ReplyChunk::Error { .. }
+            | ReplyChunk::UserPrompt { .. } => self.complete_active(),
+        }
+    }
+
+    fn before_progress(&mut self, progress: &ReplyProgressDto) -> Option<ReplyChunk> {
+        if !is_settleable_progress(progress) {
+            return self.complete_active();
+        }
+        match progress.stage {
+            ReplyProgressStageDto::Started | ReplyProgressStageDto::Delta => {
+                let next_key = progress_entity_key(progress);
+                let previous = self.active.as_ref().and_then(progress_entity_key);
+                if previous.as_deref() == next_key.as_deref() {
+                    self.active = Some(progress.clone());
+                    None
+                } else {
+                    let completed = self.complete_active();
+                    self.active = Some(progress.clone());
+                    completed
+                }
+            }
+            ReplyProgressStageDto::Completed => {
+                let next_key = progress_entity_key(progress);
+                let previous = self.active.as_ref().and_then(progress_entity_key);
+                if previous.as_deref() == next_key.as_deref() {
+                    self.active = None;
+                }
+                None
+            }
+            ReplyProgressStageDto::Info => self.complete_active(),
+        }
+    }
+
+    fn complete_active(&mut self) -> Option<ReplyChunk> {
+        let mut progress = self.active.take()?;
+        progress.stage = ReplyProgressStageDto::Completed;
+        Some(ReplyChunk::Progress { progress })
+    }
+}
+
+fn is_settleable_progress(progress: &ReplyProgressDto) -> bool {
+    matches!(
+        progress.kind,
+        ReplyProgressKindDto::Tool | ReplyProgressKindDto::Mcp | ReplyProgressKindDto::Message
+    )
+}
+
+fn progress_entity_key(progress: &ReplyProgressDto) -> Option<String> {
+    if !is_settleable_progress(progress) {
+        return None;
+    }
+    let name = progress
+        .tool_name
+        .as_ref()
+        .filter(|name| !name.trim().is_empty())
+        .unwrap_or(&progress.label);
+    let name = name.trim().to_ascii_lowercase();
+    (!name.is_empty()).then(|| format!("{:?}:{name}", progress.kind))
+}
+
 fn reply_chunk_bytes(chunk: &ReplyChunk) -> usize {
     match chunk {
         ReplyChunk::UserPrompt { text, attachments } => {

crates/app-tauri/src/commands.rs

@@ -2379,6 +2379,7 @@ pub async fn agent_send(
     let tap_bridge = std::sync::Arc::clone(&state.chat_bridge);
     let tap_sid = sid;
     let tap_pump = std::thread::spawn(move || {
+        let mut settler = crate::chat::ProgressSettler::default();
         for event in tap_rx {
             let Some(chunk) = crate::chat::chunk_from_event(event) else {
                 continue;
@@ -2386,7 +2387,10 @@ pub async fn agent_send(
             if matches!(chunk, ReplyChunk::Final { .. } | ReplyChunk::Error { .. }) {
                 continue;
             }
-            let _ = tap_bridge.send_output(&tap_sid, chunk);
+            let _ = tap_bridge.send_output_settled(&tap_sid, &mut settler, chunk);
+        }
+        if let Some(completed) = settler.finish() {
+            let _ = tap_bridge.send_output(&tap_sid, completed);
         }
     });
 
@@ -2411,6 +2415,7 @@ pub async fn agent_send(
     let meta = state.structured_sessions.meta_for_session(&sid);
     std::thread::spawn(move || {
         let mut terminal_visible = false;
+        let mut settler = crate::chat::ProgressSettler::default();
         for event in stream {
             // Non-terminal, sans contenu chat : un signal de limite alimente le service
             // (le badge UI vient du bus `AgentRateLimited`, pas du flux chat) puis on
@@ -2447,11 +2452,12 @@ pub async fn agent_send(
             // boolean only reflects live delivery. If the view navigated away
             // (no channel at this generation) we keep draining so the turn still
             // completes and the scrollback stays whole for the next re-attach.
-            let _ = bridge.send_output(&sid, chunk);
+            let _ = bridge.send_output_settled(&sid, &mut settler, chunk);
         }
         if !terminal_visible {
-            let _ = bridge.send_output(
+            let _ = bridge.send_output_settled(
                 &sid,
+                &mut settler,
                 ReplyChunk::Error {
                     message: "Le modèle n'a renvoyé aucune réponse.".to_owned(),
                 },
@@ -2967,6 +2973,28 @@ pub fn reattach_agent_chat(
     })
 }
 
+/// `detach_agent_chat` — detach only the custom chat view transport from a live
+/// structured session, preserving the agent process and retained scrollback.
+///
+/// This is the backend distinction between a disappearing view
+/// (layout/tab/project switch, cell unmount) and [`close_agent_session`], which is
+/// an explicit destructive close.
+///
+/// # Errors
+/// Returns an [`ErrorDto`] (`INVALID` for a malformed id, `NOT_FOUND` if no live
+/// structured session owns the id).
+#[tauri::command]
+pub fn detach_agent_chat(session_id: String, state: State<'_, AppState>) -> Result<(), ErrorDto> {
+    let sid = parse_session_id(&session_id)?;
+    if state.structured_sessions.session(&sid).is_none() {
+        return Err(ErrorDto::from(AppError::NotFound(format!(
+            "structured session {sid}"
+        ))));
+    }
+    state.chat_bridge.detach(&sid);
+    Ok(())
+}
+
 /// `close_agent_session` — shut a live structured session down and tear its
 /// transport (channel + conversation scrollback) down (ARCHITECTURE §17.7).
 ///

crates/app-tauri/src/lib.rs

@@ -354,6 +354,7 @@ pub fn run() {
             commands::delegation_delivered,
             commands::set_front_attached,
             commands::reattach_agent_chat,
+            commands::detach_agent_chat,
             commands::close_agent_session,
             commands::list_resumable_agents,
             commands::inspect_conversation,

crates/app-tauri/tests/chat_bridge.rs

@@ -14,9 +14,13 @@ use std::sync::{Arc, Mutex};
 use tauri::ipc::{Channel, InvokeResponseBody};
 
 use app_tauri_lib::chat::{
-    chunk_from_event, ChatBridge, MAX_CHAT_SCROLLBACK_BYTES, MAX_CHAT_SCROLLBACK_CHUNKS,
+    chunk_from_event, ChatBridge, ProgressSettler, MAX_CHAT_SCROLLBACK_BYTES,
+    MAX_CHAT_SCROLLBACK_CHUNKS,
+};
+use app_tauri_lib::dto::{
+    ReplyChunk, ReplyProgressDto, ReplyProgressKindDto, ReplyProgressSourceDto,
+    ReplyProgressStageDto,
 };
-use app_tauri_lib::dto::ReplyChunk;
 use domain::ids::SessionId;
 use domain::ports::{
     ReplyEvent, ReplyProgress, ReplyProgressKind, ReplyProgressSource, ReplyProgressStage,
@@ -59,6 +63,25 @@ fn error_chunk(s: &str) -> ReplyChunk {
     }
 }
 
+fn progress_chunk(
+    kind: ReplyProgressKindDto,
+    stage: ReplyProgressStageDto,
+    label: &str,
+) -> ReplyChunk {
+    ReplyChunk::Progress {
+        progress: ReplyProgressDto {
+            source: ReplyProgressSourceDto::ProviderNative,
+            kind,
+            stage,
+            label: label.to_owned(),
+            text: None,
+            provider: None,
+            native_event: None,
+            tool_name: Some(label.to_owned()),
+        },
+    }
+}
+
 fn chunk_bytes(chunk: &ReplyChunk) -> usize {
     match chunk {
         ReplyChunk::UserPrompt { text, attachments } => {
@@ -458,6 +481,47 @@ fn reattach_repaints_scrollback_and_preserves_it_without_resend() {
     );
 }
 
+#[test]
+fn detach_view_keeps_session_scrollback_and_later_reattach_replays_absent_chunks() {
+    let bridge = ChatBridge::new();
+    let session = sid();
+    let first_sink = Arc::new(Mutex::new(Vec::new()));
+    let _gen = bridge.register(session, capturing_channel(Arc::clone(&first_sink)));
+
+    assert!(bridge.send_output(&session, delta("before")));
+    bridge.detach(&session);
+
+    assert!(
+        !bridge.send_output(&session, delta("during")),
+        "detached view receives nothing live"
+    );
+    assert_eq!(
+        bridge.active_sessions(),
+        1,
+        "detach keeps session registered"
+    );
+    assert_eq!(
+        bridge.scrollback(&session),
+        vec![delta("before"), delta("during")],
+        "chunks produced while detached are retained for reattach"
+    );
+    assert_eq!(first_sink.lock().unwrap().as_slice(), &[delta("before")]);
+
+    let reattach_sink = Arc::new(Mutex::new(Vec::new()));
+    bridge.register(session, capturing_channel(Arc::clone(&reattach_sink)));
+    assert!(bridge.send_output(&session, final_chunk("done")));
+
+    assert_eq!(
+        bridge.scrollback(&session),
+        vec![delta("before"), delta("during"), final_chunk("done")]
+    );
+    assert_eq!(
+        reattach_sink.lock().unwrap().as_slice(),
+        &[final_chunk("done")],
+        "reattach receives only new live chunks; returned scrollback replays history"
+    );
+}
+
 #[test]
 fn scrollback_of_unknown_session_is_empty() {
     let bridge = ChatBridge::new();
@@ -625,6 +689,71 @@ fn unregister_purges_channel_and_scrollback() {
     assert_eq!(sink.lock().unwrap().as_slice(), &[final_chunk("bye")]);
 }
 
+#[test]
+fn send_output_settled_completes_stale_tool_progress_before_next_activity() {
+    let bridge = ChatBridge::new();
+    let session = sid();
+    let sink = Arc::new(Mutex::new(Vec::new()));
+    bridge.register(session, capturing_channel(Arc::clone(&sink)));
+    let mut settler = ProgressSettler::default();
+
+    let started = progress_chunk(
+        ReplyProgressKindDto::Tool,
+        ReplyProgressStageDto::Started,
+        "read_file",
+    );
+    let next = progress_chunk(
+        ReplyProgressKindDto::Mcp,
+        ReplyProgressStageDto::Started,
+        "idea_ask_agent",
+    );
+
+    assert!(bridge.send_output_settled(&session, &mut settler, started.clone()));
+    assert!(bridge.send_output_settled(&session, &mut settler, next.clone()));
+    assert!(bridge.send_output_settled(&session, &mut settler, delta("answer")));
+
+    let received = sink.lock().unwrap().clone();
+    assert_eq!(received.len(), 5);
+    assert_eq!(received[0], started);
+    assert!(matches!(
+        &received[1],
+        ReplyChunk::Progress { progress }
+            if progress.label == "read_file"
+                && progress.stage == ReplyProgressStageDto::Completed
+    ));
+    assert_eq!(received[2], next);
+    assert!(matches!(
+        &received[3],
+        ReplyChunk::Progress { progress }
+            if progress.label == "idea_ask_agent"
+                && progress.stage == ReplyProgressStageDto::Completed
+    ));
+    assert_eq!(received[4], delta("answer"));
+}
+
+#[test]
+fn progress_settler_finish_completes_active_progress_at_stream_end() {
+    let bridge = ChatBridge::new();
+    let session = sid();
+    let sink = Arc::new(Mutex::new(Vec::new()));
+    bridge.register(session, capturing_channel(Arc::clone(&sink)));
+    let mut settler = ProgressSettler::default();
+    let started = progress_chunk(
+        ReplyProgressKindDto::Tool,
+        ReplyProgressStageDto::Started,
+        "write_file",
+    );
+
+    assert!(bridge.send_output_settled(&session, &mut settler, started));
+
+    let Some(ReplyChunk::Progress { progress: done }) = settler.finish() else {
+        panic!("finish must complete the active progress")
+    };
+    assert_eq!(done.label, "write_file");
+    assert_eq!(done.stage, ReplyProgressStageDto::Completed);
+    assert!(settler.finish().is_none());
+}
+
 // ---------------------------------------------------------------------------
 // Registry basics, mirrored from pty_bridge.rs for parity
 // ---------------------------------------------------------------------------

crates/backend/src/stream.rs

@@ -176,6 +176,15 @@ where
         }
     }
 
+    pub fn detach(&self, key: &K) {
+        if let Ok(mut map) = self.entries.lock() {
+            if let Some(entry) = map.get_mut(key) {
+                entry.sink = None;
+                entry.generation = entry.generation.wrapping_add(1);
+            }
+        }
+    }
+
     pub fn detach_if(&self, key: &K, gen: u64) {
         if let Ok(mut map) = self.entries.lock() {
             if let Some(entry) = map.get_mut(key) {

crates/domain/src/ports.rs

@@ -688,7 +688,7 @@ impl ReplyProgress {
     /// Ajoute un extrait textuel.
     #[must_use]
     pub fn with_text(mut self, text: impl Into<String>) -> Self {
-        self.text = Some(text.into());
+        self.text = bounded_reply_progress_preview(text.into());
         self
     }
 
@@ -712,6 +712,57 @@ impl ReplyProgress {
     }
 }
 
+fn bounded_reply_progress_preview(text: String) -> Option<String> {
+    let mut lines = Vec::new();
+    let normalized = text.replace("\r\n", "\n").replace('\r', "\n");
+    for line in normalized.lines() {
+        let trimmed = line.trim();
+        if trimmed.is_empty() {
+            continue;
+        }
+        lines.push(trimmed.to_owned());
+        if lines.len() == 4 {
+            break;
+        }
+    }
+    if lines.is_empty() {
+        None
+    } else {
+        Some(lines.join("\n"))
+    }
+}
+
+#[cfg(test)]
+mod reply_progress_tests {
+    use super::{ReplyProgress, ReplyProgressKind, ReplyProgressSource, ReplyProgressStage};
+
+    #[test]
+    fn with_text_keeps_first_four_non_blank_lines() {
+        let progress = ReplyProgress::new(
+            ReplyProgressSource::ProviderNative,
+            ReplyProgressKind::Tool,
+            ReplyProgressStage::Started,
+            "tool",
+        )
+        .with_text(" one \n\n two\r\n three\r four\n five ");
+
+        assert_eq!(progress.text.as_deref(), Some("one\ntwo\nthree\nfour"));
+    }
+
+    #[test]
+    fn with_text_drops_blank_preview() {
+        let progress = ReplyProgress::new(
+            ReplyProgressSource::ProviderNative,
+            ReplyProgressKind::Tool,
+            ReplyProgressStage::Started,
+            "tool",
+        )
+        .with_text(" \n\t\r\n ");
+
+        assert_eq!(progress.text, None);
+    }
+}
+
 /// Un événement incrémental d'un tour de réponse d'un agent IA (ARCHITECTURE §17.1).
 ///
 /// Universel : l'adapter (Claude/Codex) traduit SON format structuré documenté

crates/infrastructure/src/session/claude.rs

@@ -153,15 +153,17 @@ fn assistant_events(value: &Value) -> Vec<ReplyEvent> {
                     .and_then(Value::as_str)
                     .unwrap_or("outil")
                     .to_owned();
-                events.push(ReplyEvent::Progress {
+                let mut progress = provider_progress(
-                    progress: provider_progress(
                     ReplyProgressKind::Tool,
                     ReplyProgressStage::Started,
                     label.clone(),
                     "tool_use",
                 )
-                    .with_tool_name(label.clone()),
+                .with_tool_name(label.clone());
-                });
+                if let Some(preview) = tool_use_preview(block) {
+                    progress = progress.with_text(preview);
+                }
+                events.push(ReplyEvent::Progress { progress });
                 events.push(ReplyEvent::ToolActivity { label });
             }
             _ => {}
@@ -170,6 +172,22 @@ fn assistant_events(value: &Value) -> Vec<ReplyEvent> {
     events
 }
 
+fn tool_use_preview(block: &Value) -> Option<String> {
+    block
+        .get("input")
+        .or_else(|| block.get("arguments"))
+        .or_else(|| block.get("parameters"))
+        .map(preview_value)
+        .filter(|text| !text.trim().is_empty())
+}
+
+fn preview_value(value: &Value) -> String {
+    value
+        .as_str()
+        .map(str::to_owned)
+        .unwrap_or_else(|| value.to_string())
+}
+
 fn provider_progress(
     kind: ReplyProgressKind,
     stage: ReplyProgressStage,

crates/infrastructure/src/session/codex.rs

@@ -156,6 +156,7 @@ pub fn parse_event(line: &str) -> Result<ParsedLine, AgentSessionError> {
                         let label = item_label(item).unwrap_or_else(|| kind.to_owned());
                         events.push(ReplyEvent::Progress {
                             progress: item_progress(
+                                item,
                                 &label,
                                 ReplyProgressStage::Completed,
                                 value
@@ -190,11 +191,12 @@ fn provider_progress(
 }
 
 fn item_progress(
+    item: &Value,
     label: &str,
     stage: ReplyProgressStage,
     native_event: impl Into<String>,
 ) -> ReplyProgress {
-    if label.starts_with("idea_") {
+    let progress = if label.starts_with("idea_") {
         ReplyProgress::new(
             ReplyProgressSource::IdeaLocal,
             ReplyProgressKind::Mcp,
@@ -211,6 +213,11 @@ fn item_progress(
             native_event,
         )
         .with_tool_name(label.to_owned())
+    };
+    if let Some(preview) = item_preview(item) {
+        progress.with_text(preview)
+    } else {
+        progress
     }
 }
 
@@ -228,7 +235,7 @@ fn append_item_progress(
     }
     let label = item_label(item).unwrap_or(kind);
     events.push(ReplyEvent::Progress {
-        progress: item_progress(&label, stage, native_event),
+        progress: item_progress(item, &label, stage, native_event),
     });
 }
 
@@ -255,6 +262,26 @@ fn item_text(item: &Value) -> Option<String> {
         .or_else(|| nested_non_blank(item, &["content", "text"]))
 }
 
+fn item_preview(item: &Value) -> Option<String> {
+    non_blank_string(item.get("arguments"))
+        .or_else(|| non_blank_string(item.get("input")))
+        .or_else(|| non_blank_string(item.get("command")))
+        .or_else(|| non_blank_string(item.get("text")))
+        .or_else(|| non_blank_string(item.get("message")))
+        .or_else(|| nested_non_blank(item, &["function", "arguments"]))
+        .or_else(|| nested_non_blank(item, &["function_call", "arguments"]))
+        .or_else(|| nested_non_blank(item, &["call", "arguments"]))
+        .or_else(|| value_preview(item.get("arguments")))
+        .or_else(|| value_preview(item.get("input")))
+}
+
+fn value_preview(value: Option<&Value>) -> Option<String> {
+    value
+        .filter(|value| value.is_object() || value.is_array())
+        .map(Value::to_string)
+        .filter(|text| !text.trim().is_empty())
+}
+
 fn nested_non_blank(root: &Value, path: &[&str]) -> Option<String> {
     let mut cursor = root;
     for key in path {

crates/infrastructure/src/session/openai_compat.rs

@@ -466,6 +466,7 @@ impl OpenAiCompatibleSession {
                 ReplyProgressStage::Started,
                 format!("appel MCP {}", call.name),
                 &call.name,
+                Some(call.arguments.as_str()),
             );
             send_tap(tap, &started);
             events.push(started);
@@ -485,6 +486,7 @@ impl OpenAiCompatibleSession {
                 ReplyProgressStage::Completed,
                 format!("MCP {} terminé", call.name),
                 &call.name,
+                Some(result.as_str()),
             );
             send_tap(tap, &completed);
             events.push(completed);
@@ -658,16 +660,19 @@ fn local_tool_progress(
     stage: ReplyProgressStage,
     label: impl Into<String>,
     tool_name: &str,
+    preview: Option<&str>,
 ) -> ReplyEvent {
-    ReplyEvent::Progress {
+    let mut progress = ReplyProgress::new(
-        progress: ReplyProgress::new(
         ReplyProgressSource::IdeaLocal,
         ReplyProgressKind::Mcp,
         stage,
         label,
     )
-        .with_tool_name(tool_name.to_owned()),
+    .with_tool_name(tool_name.to_owned());
+    if let Some(preview) = preview {
+        progress = progress.with_text(preview);
     }
+    ReplyEvent::Progress { progress }
 }
 
 fn should_retry_without_tools(err: &AgentSessionError, using_tools: bool) -> bool {

crates/infrastructure/src/session/opencode.rs

@@ -31,7 +31,12 @@ pub enum ParsedEvent {
     /// Fragment texte assistant.
     Text(String),
     /// Activité outil OpenCode.
-    ToolActivity(String),
+    ToolActivity {
+        /// Nom d'outil affichable.
+        label: String,
+        /// Aperçu borné du payload d'appel outil, quand OpenCode l'expose.
+        preview: Option<String>,
+    },
     /// Fin d'étape OpenCode.
     StepFinish,
     /// Erreur terminale remontée par OpenCode.
@@ -110,7 +115,10 @@ fn parse_jsonl_record(line: &str) -> Result<ParsedRecord, AgentSessionError> {
             .and_then(Value::as_str)
             .map(|text| ParsedEvent::Text(text.to_owned()))
             .unwrap_or(ParsedEvent::Ignored),
-        Some("tool_use" | "tool.use" | "tool") => ParsedEvent::ToolActivity(tool_label(&value)),
+        Some("tool_use" | "tool.use" | "tool") => ParsedEvent::ToolActivity {
+            label: tool_label(&value),
+            preview: tool_preview(&value),
+        },
         Some("error" | "session.error") => ParsedEvent::Error(opencode_error_message(&value)),
         _ => ParsedEvent::Ignored,
     };
@@ -168,6 +176,39 @@ fn tool_label(value: &Value) -> String {
         .unwrap_or_else(|| "outil OpenCode".to_owned())
 }
 
+fn tool_preview(value: &Value) -> Option<String> {
+    let part = value.get("part").unwrap_or(value);
+    non_blank_string(part.get("arguments"))
+        .or_else(|| non_blank_string(part.get("input")))
+        .or_else(|| non_blank_string(part.get("params")))
+        .or_else(|| non_blank_string(part.get("command")))
+        .or_else(|| non_blank_string(value.get("arguments")))
+        .or_else(|| non_blank_string(value.get("input")))
+        .or_else(|| non_blank_string(value.get("params")))
+        .or_else(|| non_blank_string(value.get("command")))
+        .or_else(|| value_preview(part.get("arguments")))
+        .or_else(|| value_preview(part.get("input")))
+        .or_else(|| value_preview(part.get("params")))
+        .or_else(|| value_preview(value.get("arguments")))
+        .or_else(|| value_preview(value.get("input")))
+        .or_else(|| value_preview(value.get("params")))
+}
+
+fn non_blank_string(value: Option<&Value>) -> Option<String> {
+    value
+        .and_then(Value::as_str)
+        .map(str::trim)
+        .filter(|text| !text.is_empty())
+        .map(str::to_owned)
+}
+
+fn value_preview(value: Option<&Value>) -> Option<String> {
+    value
+        .filter(|value| value.is_object() || value.is_array())
+        .map(Value::to_string)
+        .filter(|text| !text.trim().is_empty())
+}
+
 /// Convertit des lignes JSONL OpenCode en événements domaine.
 ///
 /// Le `Final` est la concaténation ordonnée des événements `text` du tour courant.
@@ -226,10 +267,12 @@ fn append_record_events(
             });
             events.push(ReplyEvent::Heartbeat);
         }
-        ParsedEvent::ToolActivity(label) => {
+        ParsedEvent::ToolActivity { label, preview } => {
-            events.push(ReplyEvent::Progress {
+            let mut progress = tool_progress(&label);
-                progress: tool_progress(&label),
+            if let Some(preview) = preview {
-            });
+                progress = progress.with_text(preview);
+            }
+            events.push(ReplyEvent::Progress { progress });
             events.push(ReplyEvent::ToolActivity { label });
         }
         ParsedEvent::Text(text) => {
@@ -396,7 +439,7 @@ fn current_turn_records(
         matches!(
             record.event,
             ParsedEvent::Text(_)
-                | ParsedEvent::ToolActivity(_)
+                | ParsedEvent::ToolActivity { .. }
                 | ParsedEvent::StepStart
                 | ParsedEvent::StepFinish
                 | ParsedEvent::Error(_)
@@ -871,7 +914,13 @@ mod tests {
     #[test]
     fn parse_jsonl_event_accepts_tool_use() {
         let event = parse_jsonl_event(r#"{"type":"tool_use","part":{"tool":"bash"}}"#).unwrap();
-        assert_eq!(event, ParsedEvent::ToolActivity("bash".to_owned()));
+        assert_eq!(
+            event,
+            ParsedEvent::ToolActivity {
+                label: "bash".to_owned(),
+                preview: None,
+            }
+        );
     }
 
     #[test]

frontend/src/adapters/agent.test.ts

@@ -171,6 +171,15 @@ describe("TauriAgentGateway invoke payloads", () => {
     expect(invoke).not.toHaveBeenCalledWith("close_agent_session", expect.anything());
   });
 
+  it("detachAgentChat invokes detach_agent_chat without closing the session", async () => {
+    await new TauriAgentGateway().detachAgentChat("chat-session-1");
+
+    expect(invoke).toHaveBeenCalledWith("detach_agent_chat", {
+      sessionId: "chat-session-1",
+    });
+    expect(invoke).not.toHaveBeenCalledWith("close_agent_session", expect.anything());
+  });
+
   it("sendAgentChat forwards structured clipboard attachments to agent_send", async () => {
     await new TauriAgentGateway().sendAgentChat(
       "chat-session-1",

frontend/src/adapters/agent.ts

@@ -262,6 +262,10 @@ export class TauriAgentGateway implements AgentGateway {
     });
   }
 
+  async detachAgentChat(sessionId: string): Promise<void> {
+    await invoke("detach_agent_chat", { sessionId });
+  }
+
   async sendAgentChat(
     sessionId: string,
     prompt: string,

frontend/src/adapters/mock/index.ts

@@ -1026,6 +1026,15 @@ export class MockAgentGateway implements AgentGateway {
     }
   }
 
+  async detachAgentChat(sessionId: string): Promise<void> {
+    if (!this.chatScrollback.has(sessionId)) {
+      throw {
+        code: "NOT_FOUND",
+        message: `agent chat session ${sessionId} not found`,
+      } as GatewayError;
+    }
+  }
+
   async cancelAgentChat(sessionId: string): Promise<void> {
     if (!this.chatScrollback.has(sessionId)) {
       throw {

frontend/src/features/agents/CustomAgentChatView.test.tsx

@@ -1,9 +1,9 @@
 import { act, fireEvent, render, screen, waitFor } from "@testing-library/react";
 import { useState } from "react";
-import { describe, expect, it, vi } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import { DIProvider } from "@/app/di";
-import type { AgentProfile } from "@/domain";
+import type { AgentProfile, ReplyChunk } from "@/domain";
 import { PluginRuntimeProvider } from "@/features/plugins";
 import {
   PluginCommandRegistry,
@@ -12,7 +12,10 @@ import {
   PluginRuntimeRegistry,
 } from "@/plugins/runtime";
 import type { ChatDraftScope, Gateways } from "@/ports";
-import { CustomAgentChatView } from "./CustomAgentChatView";
+import {
+  CustomAgentChatView,
+  __clearCustomAgentChatViewCacheForTests,
+} from "./CustomAgentChatView";
 
 const profile: AgentProfile = {
   id: "structured",
@@ -57,6 +60,11 @@ function addPluginCommand(
 }
 
 describe("CustomAgentChatView", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    __clearCustomAgentChatViewCacheForTests();
+  });
+
   it("repaints attachment labels from user prompt scrollback", async () => {
     const agent = {
       launchAgentChat: vi.fn(),
@@ -101,6 +109,75 @@ describe("CustomAgentChatView", () => {
     expect(screen.getByText("Fichier: clipboard.png")).toBeTruthy();
   });
 
+  it("detaches on unmount then reattaches with missed scrollback chunks", async () => {
+    let scrollback: ReplyChunk[] = [
+      { kind: "userPrompt" as const, text: "Initial prompt" },
+      { kind: "textDelta" as const, text: "Initial reply" },
+    ];
+    const agent = {
+      launchAgentChat: vi.fn(),
+      reattachAgentChat: vi.fn(async (sessionId: string) => ({
+        sessionId,
+        scrollback,
+      })),
+      detachAgentChat: vi.fn(async () => {}),
+      sendAgentChat: vi.fn(async () => {}),
+      cancelAgentChat: vi.fn(async () => {}),
+      closeAgentChat: vi.fn(async () => {}),
+    };
+    const props = {
+      projectId: "project-1",
+      agentId: "agent-1",
+      agentName: "Worker",
+      profile,
+      cwd: "/repo",
+      nodeId: "node-1",
+      sessionId: "chat-session-1",
+      conversationId: "conversation-1",
+      onSessionId: vi.fn(),
+      onConversationId: vi.fn(),
+    };
+
+    const first = render(
+      <DIProvider
+        gateways={{
+          agent,
+          system: { pickFile: vi.fn(async () => null) },
+        } as unknown as Gateways}
+      >
+        <CustomAgentChatView {...props} />
+      </DIProvider>,
+    );
+
+    expect(await screen.findByText("Initial reply")).toBeTruthy();
+    first.unmount();
+    await waitFor(() => expect(agent.detachAgentChat).toHaveBeenCalledWith("chat-session-1"));
+
+    scrollback = [
+      ...scrollback,
+      { kind: "toolActivity" as const, label: "Background tool" },
+      { kind: "final" as const, content: "Completed away" },
+    ];
+
+    render(
+      <DIProvider
+        gateways={{
+          agent,
+          system: { pickFile: vi.fn(async () => null) },
+        } as unknown as Gateways}
+      >
+        <CustomAgentChatView {...props} />
+      </DIProvider>,
+    );
+
+    expect(screen.getByText("Initial reply")).toBeTruthy();
+    expect(await screen.findByText("Background tool")).toBeTruthy();
+    expect(screen.getByText("Completed away")).toBeTruthy();
+    expect(
+      screen.getByText("Reprise effectuée: 2 événements rattrapés pendant l'absence."),
+    ).toBeTruthy();
+  });
+
   it("stops the live agent with cascade feedback and releases the structured session", async () => {
     let resolveStop: (value: {
       agentId: string;
@@ -614,7 +691,7 @@ describe("CustomAgentChatView", () => {
 
     expect(screen.getByText("Worker → QA")).toBeTruthy();
     expect(screen.getByText("Worker → QA").parentElement?.textContent).toContain("started");
-    expect(screen.getAllByRole("status", { name: "Loading" }).length).toBeGreaterThan(0);
+    expect(screen.queryByRole("status", { name: "Loading" })).toBeNull();
 
     act(() => {
       emitChunk?.(progress("providerNative", "completed"));
@@ -638,7 +715,7 @@ describe("CustomAgentChatView", () => {
     );
   });
 
-  it("stops animating running progress rows once the turn reaches a final chunk", async () => {
+  it("renders running progress without spinner and marks it done on final", async () => {
     let emitChunk: ((chunk: unknown) => void) | null = null;
     const agent = {
       launchAgentChat: vi.fn(),
@@ -707,7 +784,7 @@ describe("CustomAgentChatView", () => {
       });
     });
 
-    expect(screen.getAllByRole("status", { name: "Loading" }).length).toBeGreaterThan(0);
+    expect(screen.queryByRole("status", { name: "Loading" })).toBeNull();
     expect(screen.getByText("Progress").parentElement?.textContent).toContain("running");
 
     act(() => {

frontend/src/features/agents/CustomAgentChatView.tsx

@@ -53,6 +53,17 @@ type ChatTurn =
   | { role: "error"; text: string }
   | { role: "unknown"; text: string };
 
+interface CachedChatView {
+  turns: ChatTurn[];
+  chunkCount: number;
+}
+
+const chatSessionViewCache = new Map<string, CachedChatView>();
+
+export function __clearCustomAgentChatViewCacheForTests() {
+  chatSessionViewCache.clear();
+}
+
 interface AttachmentDraft {
   id: string;
   label: string;
@@ -288,6 +299,17 @@ function appendProgress(turns: ChatTurn[], progress: ReplyProgress): ChatTurn[]
   return [...turns, { role: "progress", progress }];
 }
 
+function reattachNotice(missedChunks: number): ChatTurn | null {
+  if (missedChunks <= 0) return null;
+  return {
+    role: "tool",
+    label:
+      missedChunks === 1
+        ? "Reprise effectuée: 1 événement rattrapé pendant l'absence."
+        : `Reprise effectuée: ${missedChunks} événements rattrapés pendant l'absence.`,
+  };
+}
+
 function mergeCompletedProgress(
   running: ReplyProgress,
   completed: ReplyProgress,
@@ -522,7 +544,9 @@ export function CustomAgentChatView({
 }: CustomAgentChatViewProps) {
   const { agent, profile: profileGateway, system } = useGateways();
   const pluginRuntime = usePluginRuntime();
-  const [turns, setTurns] = useState<ChatTurn[]>([]);
+  const [turns, setTurns] = useState<ChatTurn[]>(
+    () => (sessionId ? (chatSessionViewCache.get(sessionId)?.turns ?? []) : []),
+  );
   const [currentSession, setCurrentSession] = useState(sessionId);
   const [externalSessionId, setExternalSessionId] = useState(sessionId);
   const [draft, setDraft] = useState("");
@@ -540,6 +564,11 @@ export function CustomAgentChatView({
   const composerRef = useRef<HTMLTextAreaElement | null>(null);
   const sessionRef = useRef<string | null>(sessionId);
   sessionRef.current = currentSession;
+  const scrollbackChunkCountRef = useRef(
+    sessionId ? (chatSessionViewCache.get(sessionId)?.chunkCount ?? 0) : 0,
+  );
+  const detachAgentChatRef = useRef(agent.detachAgentChat);
+  detachAgentChatRef.current = agent.detachAgentChat;
   const slashQuerySeqRef = useRef(0);
   const draftSaveSeqRef = useRef(0);
   const draftHydratedRef = useRef(false);
@@ -593,14 +622,30 @@ export function CustomAgentChatView({
     mountedRef.current = true;
     return () => {
       mountedRef.current = false;
+      const sid = sessionRef.current;
+      if (!sid) return;
+      void detachAgentChatRef.current?.(sid).catch((e) => {
+        if (!isNotFound(e)) {
+          console.warn("[ticket188] detachAgentChat failed", instrumentationError(e));
+        }
+      });
     };
   }, []);
 
   const receive = useCallback((chunk: ReplyChunk) => {
+    scrollbackChunkCountRef.current += 1;
     setTurns((prev) => foldChunk(prev, chunk));
     if (chunk.kind === "final" || chunk.kind === "error") setBusy(false);
   }, []);
 
+  useEffect(() => {
+    if (!currentSession) return;
+    chatSessionViewCache.set(currentSession, {
+      turns,
+      chunkCount: scrollbackChunkCountRef.current,
+    });
+  }, [currentSession, turns]);
+
   useEffect(() => {
     draftSaveSeqRef.current += 1;
     draftHydratedRef.current = false;
@@ -748,7 +793,14 @@ export function CustomAgentChatView({
       if (!mountedRef.current) return reattached.sessionId;
       setCurrentSession(reattached.sessionId);
       if (options.applyScrollback) {
-        setTurns(reattached.scrollback.reduce(foldChunk, [] as ChatTurn[]));
+        const cachedCount = chatSessionViewCache.get(sid)?.chunkCount ?? 0;
+        scrollbackChunkCountRef.current = Math.max(
+          scrollbackChunkCountRef.current,
+          reattached.scrollback.length,
+        );
+        const replayed = reattached.scrollback.reduce(foldChunk, [] as ChatTurn[]);
+        const notice = reattachNotice(reattached.scrollback.length - cachedCount);
+        setTurns(notice ? [...replayed, notice] : replayed);
       }
       return reattached.sessionId;
     },
@@ -810,6 +862,7 @@ export function CustomAgentChatView({
           launched,
         });
         if (!mountedRef.current) return launched.sessionId;
+        scrollbackChunkCountRef.current = 0;
         setCurrentSession(launched.sessionId);
         publishSessionId(launched.sessionId);
         if (launched.assignedConversationId) {
@@ -888,6 +941,11 @@ export function CustomAgentChatView({
       setError(null);
       try {
         if (externalSessionId) {
+          const cached = chatSessionViewCache.get(externalSessionId);
+          if (cached) {
+            scrollbackChunkCountRef.current = cached.chunkCount;
+            setTurns(cached.turns);
+          }
           try {
             await reattachStructuredSession(externalSessionId, { applyScrollback: true });
             if (cancelled) return;
@@ -1385,7 +1443,9 @@ export function CustomAgentChatView({
         {opening && turns.length === 0 ? (
           <div className="flex items-center gap-2 text-sm text-muted">
             <Spinner size={14} />
-            <span>Ouverture de la session structurée…</span>
+            <span>
+              {externalSessionId ? "Reprise en cours..." : "Ouverture de la session structurée…"}
+            </span>
           </div>
         ) : turns.length === 0 ? (
           <p className="m-auto text-xs text-muted">
@@ -1572,7 +1632,6 @@ function ChatBubble({
       <ProgressBubble
         progress={turn.progress}
         requesterName={requesterName}
-        settled={turn.settled}
       />
     );
   }
@@ -1683,9 +1742,20 @@ function compactToolName(progress: ReplyProgress): string {
   return progress.toolName ?? progress.label;
 }
 
-function truncateText(text: string, max = 140): string {
+function previewText(text: string, maxLineLength = 160): string {
-  const flat = text.replace(/\s+/g, " ").trim();
+  return text
-  return flat.length > max ? `${flat.slice(0, max - 3)}...` : flat;
+    .replace(/\r\n/g, "\n")
+    .replace(/\r/g, "\n")
+    .split("\n")
+    .map((line) => line.trim())
+    .filter(Boolean)
+    .slice(0, 4)
+    .map((line) =>
+      line.length > maxLineLength
+        ? `${line.slice(0, Math.max(0, maxLineLength - 3))}...`
+        : line,
+    )
+    .join("\n");
 }
 
 function parseKeyValue(text: string, key: string): string | null {
@@ -1710,9 +1780,9 @@ function delegationSummary(progress: ReplyProgress): {
     requester,
     target,
     excerpt: task
-      ? truncateText(task, 92)
+      ? previewText(task, 92)
       : fallback
-        ? truncateText(fallback, 92)
+        ? previewText(fallback, 92)
         : null,
   };
 }
@@ -1743,16 +1813,13 @@ function TurnMarker({ progress }: { progress: ReplyProgress }) {
 function ToolProgressCard({
   progress,
   requesterName,
-  settled,
 }: {
   progress: ReplyProgress;
   requesterName: string;
-  settled: boolean;
 }) {
-  const running = !settled && (progress.stage === "started" || progress.stage === "delta");
   const stage = progressStageLabel(progress.stage);
   const detail =
-    progress.text && !isDelegationProgress(progress) ? truncateText(progress.text) : null;
+    progress.text && !isDelegationProgress(progress) ? previewText(progress.text) : null;
   const delegation = isDelegationProgress(progress) ? delegationSummary(progress) : null;
   const title = delegation
     ? delegation.target
@@ -1770,7 +1837,6 @@ function ToolProgressCard({
         )}
       >
         <div className="flex min-w-0 items-center justify-center gap-1.5">
-          {running && <Spinner size={12} />}
           <span className="shrink-0 font-semibold">{title}</span>
           {!delegation && (
             <span className="min-w-0 truncate text-muted">{compactToolName(progress)}</span>
@@ -1787,8 +1853,19 @@ function ToolProgressCard({
             {compactToolName(progress)}
           </p>
         )}
+        {(progress.source || progress.nativeEvent || progress.provider) && (
+          <div className="mt-0.5 flex min-w-0 flex-wrap justify-center gap-x-2 gap-y-0.5 text-[11px] text-muted">
+            <span>{progressSourceLabel(progress)}</span>
+            {progress.nativeEvent && (
+              <span className="truncate">event: {progress.nativeEvent}</span>
+            )}
+          </div>
+        )}
         {detail && (
-          <p className="mt-1 text-center text-[11px] text-content" style={fourLineClamp}>
+          <p
+            className="mt-1 overflow-hidden whitespace-pre-wrap break-words text-center text-[11px] text-content"
+            style={fourLineClamp}
+          >
             {detail}
           </p>
         )}
@@ -1800,11 +1877,9 @@ function ToolProgressCard({
 function ProgressBubble({
   progress,
   requesterName,
-  settled = false,
 }: {
   progress: ReplyProgress;
   requesterName: string;
-  settled?: boolean;
 }) {
   if (isTimelineProgress(progress)) return <TurnMarker progress={progress} />;
   if (isCenteredToolProgress(progress)) {
@@ -1812,15 +1887,13 @@ function ProgressBubble({
       <ToolProgressCard
         progress={progress}
         requesterName={requesterName}
-        settled={settled}
       />
     );
   }
   const title = progressTitle(progress);
   const stage = progressStageLabel(progress.stage);
   const source = progressSourceLabel(progress);
-  const detail = progress.text ? truncateText(progress.text, 260) : null;
+  const detail = progress.text ? previewText(progress.text, 180) : null;
-  const running = !settled && (progress.stage === "started" || progress.stage === "delta");
   return (
     <div data-testid="chat-progress-status" className="flex min-w-0 justify-end">
       <div
@@ -1830,7 +1903,6 @@ function ProgressBubble({
         )}
       >
         <div className="flex min-w-0 items-center gap-1.5">
-          {running && <Spinner size={12} />}
           <span className="shrink-0 font-semibold">{title}</span>
           <span className="min-w-0 truncate text-muted">{progress.label}</span>
           <span className="shrink-0 text-muted">· {stage}</span>

frontend/src/ports/index.ts

@@ -311,6 +311,8 @@ export interface AgentGateway {
     sessionId: string,
     onChunk: (chunk: ReplyChunk) => void,
   ): Promise<ReattachAgentChatResult>;
+  /** Detaches the current custom chat view transport while keeping the session alive. */
+  detachAgentChat?(sessionId: string): Promise<void>;
   /** Sends one user prompt to a live structured session. */
   sendAgentChat?(
     sessionId: string,