docs(maestro): make sidebar card line 2 unconditional

Line 2 was rendered only past a 30s activity hold, blocked work,
exit, or reported Error, and <command> was gated behind a
metadata.name comparison and TUI-optional. Both worked against
scanability: cards changed height as sessions aged, and fresh
sessions hid their command.

Card is now always two lines. The 30s hold rule survives, demoted
to gating only the <duration> fragment. <command> is unconditional
in both clients.

Closes #116

crates/maestro-daemon/src/session.rs

@@ -62,6 +62,11 @@ pub struct SessionRecord {
     /// resumes and [`Session::activity_detail`] is cleared with it. This
     /// field is daemon-local bookkeeping only — it never rides the wire.
     pub reported_activity: Option<crate::activity::ReportedActivity>,
+    /// Flipped once the natural-exit settle step (#82) has been applied or
+    /// refused for this session. `Dead` is observable before settling ends
+    /// (#115), so this is the observable that says its outcomes are safe to
+    /// assert on. Daemon-local bookkeeping; never rides the wire.
+    pub settled: bool,
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -294,6 +299,17 @@ impl SessionManager {
         sessions.get(&id).map(|r| r.session.status)
     }
 
+    /// Whether the natural-exit settle step (#82) has finished for this
+    /// session: `Some(true)` once applied or refused, `Some(false)` while
+    /// still pending, `None` if the session is unknown. `Dead` is observable
+    /// before settling ends (#115), so anything asserting on a dead
+    /// session's worktree waits on this rather than inferring settle
+    /// completion from its side effects.
+    pub async fn is_settled(&self, id: Uuid) -> Option<bool> {
+        let sessions = self.inner.sessions.lock().await;
+        sessions.get(&id).map(|r| r.settled)
+    }
+
     /// Spawn a new session. On success returns the freshly-created `Session`.
     pub async fn create(&self, req: CreateSessionRequest) -> Result<Session, SessionError> {
         let (effective_cwd, worktree_path, worktree_base_repo) = match &req.worktree {
@@ -429,6 +445,7 @@ impl SessionManager {
                     worktree_branch: req.worktree.as_ref().map(|w| w.branch.clone()),
                     bridge,
                     reported_activity: None,
+                    settled: false,
                 },
             );
         }
@@ -657,6 +674,7 @@ impl SessionManager {
                     worktree_branch: None,
                     bridge,
                     reported_activity: None,
+                    settled: false,
                 },
             );
             let _ = self
@@ -1069,6 +1087,14 @@ async fn mark_session_dead(inner: &Arc<Inner>, id: Uuid) {
             }
         }
     }
+    // Settle has now been applied or refused either way (#115): from here on
+    // its outcomes are safe to observe.
+    {
+        let mut sessions = inner.sessions.lock().await;
+        if let Some(record) = sessions.get_mut(&id) {
+            record.settled = true;
+        }
+    }
 
     let _ = inner.sidecar.write(&session);
     let _ = inner.events.send(CatalogEvent::SessionUpdated { session });

crates/maestro-daemon/tests/activity.rs

@@ -189,8 +189,23 @@ fn a_foreground_pipeline_whose_leader_exited_is_still_awaiting_input() {
         "never observed a foreground group whose leader had exited"
     );
 
-    assert!(
-        awaiting_input(pane.pane_pid, &pane.tty, &ProcGroups::snapshot()),
-        "a surviving pipeline member still holds the tty"
-    );
+    // The leader can be gone while the surviving stage is still setting up:
+    // `true` exits as soon as both stages are forked, before the reader has
+    // opened the tty and parked. Poll for the answer, but only accept it
+    // while the state this test exists for still holds — otherwise a shell
+    // that regained the terminal would satisfy it vacuously.
+    let deadline = std::time::Instant::now() + Duration::from_secs(5);
+    let mut holds = false;
+    while std::time::Instant::now() < deadline {
+        let groups = ProcGroups::snapshot();
+        let still_leaderless = pgrp_and_tpgid(pane.pane_pid).is_some_and(|(pgrp, tpgid)| {
+            tpgid > 0 && tpgid != pgrp && pgrp_and_tpgid(tpgid).is_none()
+        });
+        if still_leaderless && awaiting_input(pane.pane_pid, &pane.tty, &groups) {
+            holds = true;
+            break;
+        }
+        std::thread::sleep(Duration::from_millis(20));
+    }
+    assert!(holds, "a surviving pipeline member still holds the tty");
 }

crates/maestro-daemon/tests/session_manager.rs

@@ -397,6 +397,12 @@ async fn watcher_refreshes_the_blocked_work_indicator() {
     init_bare_repo(origin.path());
     push_all_to_origin(repo.path(), origin.path());
 
+    // Subscribe before the watcher starts so every pass's emission is
+    // captured — otherwise the breakdown event can land between the
+    // snapshot observation below and the drain, and the quiet window
+    // would see it as an illegitimate re-emit.
+    let mut events = fx.manager.events();
+
     fx.manager.start_liveness_watcher_with_blocked_work(
         Duration::from_millis(50),
         Duration::from_millis(100),
@@ -418,14 +424,38 @@ async fn watcher_refreshes_the_blocked_work_indicator() {
     })
     .await;
 
-    // A steady state must not re-emit every tick (#83 change-detection).
-    let mut events = fx.manager.events();
+    // Consume through the emission that carried the breakdown (#83
+    // change-detection): the quiet window below must start after the last
+    // legitimate change, not race it into the channel.
+    loop {
+        match tokio::time::timeout(Duration::from_secs(5), events.recv()).await {
+            Ok(Ok(CatalogEvent::SessionUpdated { session }))
+                if matches!(
+                    &session.blocked_work,
+                    Some(b) if b.uncommitted_files >= 1 && b.untracked_files >= 1
+                ) =>
+            {
+                break;
+            }
+            Ok(Ok(_)) => continue,
+            _ => panic!("never saw the SessionUpdated carrying the breakdown"),
+        }
+    }
     while events.try_recv().is_ok() {}
     tokio::time::sleep(Duration::from_millis(400)).await;
-    assert!(
-        !matches!(events.try_recv(), Ok(CatalogEvent::SessionUpdated { .. })),
-        "an unchanged worktree must not re-emit SessionUpdated"
-    );
+    // Only a *changed* indicator counts as a re-emit (#83 change-detection).
+    // The activity pass may still legitimately announce e.g. Active→Idle
+    // (its debounce is time-based, not worktree-based), and its payload
+    // carries today's blocked_work unchanged.
+    while let Ok(CatalogEvent::SessionUpdated { session }) = events.try_recv() {
+        assert!(
+            matches!(
+                &session.blocked_work,
+                Some(b) if b.uncommitted_files >= 1 && b.untracked_files >= 1
+            ),
+            "an unchanged worktree must not re-emit a changed indicator"
+        );
+    }
 }
 
 /// Cleanup on kill is unconditional once the guard passes (#79): even a spec
@@ -848,6 +878,17 @@ async fn natural_exit_of_a_pristine_worktree_removes_it() {
     })
     .await;
 
+    // (`Dead` is observable a moment before the settle step removes the tree.)
+    wait_for_async(Duration::from_secs(3), || async {
+        !wt_path.exists()
+            && fx
+                .retained_store()
+                .load_all()
+                .map(|all| all.is_empty())
+                .unwrap_or(false)
+    })
+    .await;
+
     assert!(
         !wt_path.exists(),
         "a pristine worktree leaves nothing behind"
@@ -905,6 +946,14 @@ async fn natural_exit_without_a_retained_store_destroys_nothing() {
     })
     .await;
 
+    // The settle step has been applied or refused either way — here refused,
+    // since there is no store to record the tree into. Only from this point
+    // is "the tree survived" a settled fact rather than a race (#115).
+    wait_for_async(Duration::from_secs(3), || async {
+        manager.is_settled(s.id).await == Some(true)
+    })
+    .await;
+
     assert!(
         wt_path.exists(),
         "nothing may be destroyed when it cannot be recorded"

crates/maestro-hooks/src/lib.rs

@@ -25,13 +25,25 @@ pub const HOOK_MARKER: &str = "maestro-claude-hook";
 pub const SCRIPT_FILE_NAME: &str = "maestro-claude-hook.sh";
 
 /// Claude Code hook event → `ActivityState` spelling posted to the daemon.
-pub const HOOK_EVENTS: [(&str, &str); 3] = [
-    // Tool finished: the agent is demonstrably producing work.
+///
+/// `PreToolUse` is what makes a session `Active` *during* a long tool call —
+/// `PostToolUse` alone only fires once it ends (#114). `StopFailure` is
+/// Claude Code's own name for "the turn ended on an API error"; there is no
+/// failure signal in `Stop` or `SessionEnd` payloads, so those never report
+/// `Error`.
+pub const HOOK_EVENTS: [(&str, &str); 5] = [
+    // Tool starting: the agent is demonstrably producing work, even if the
+    // tool itself runs for minutes.
+    ("PreToolUse", "Active"),
+    // Tool finished successfully.
     ("PostToolUse", "Active"),
     // Permission / idle notices: Claude is blocked on the user.
     ("Notification", "AwaitingInput"),
     // Turn ended: waiting on the user again.
     ("Stop", "AwaitingInput"),
+    // Turn ended on an API error; the payload's `error` field is forwarded
+    // as the report's `detail` (#114).
+    ("StopFailure", "Error"),
 ];
 
 /// The shipped hook script. POSIX sh so any `/bin/sh` works.
@@ -39,17 +51,27 @@ pub const HOOK_SCRIPT: &str = r#"#!/bin/sh
 # Installed by maestro (#106): report Claude Code activity to its daemon.
 # Exits silently unless running inside a session maestro spawned (#103 env).
 # Event -> ActivityState mapping:
-#   PostToolUse   -> Active         (tool finished; agent is working)
+#   PreToolUse    -> Active         (tool started; agent is working)
+#   PostToolUse   -> Active         (tool finished)
 #   Notification  -> AwaitingInput  (permission / idle notice)
 #   Stop          -> AwaitingInput  (turn ended; waiting on the user)
+#   StopFailure   -> Error          (turn ended on an API error)
 state="$1"
 [ -n "$MAESTRO_SESSION_ID" ] || exit 0
 [ -n "$MAESTRO_URL" ] || exit 0
-# Drain the hook payload so the parent never sees a broken pipe.
-cat >/dev/null 2>&1
+payload=$(cat 2>/dev/null) || true
+body="{\"state\":\"$state\"}"
+# StopFailure payloads carry the outcome in "error". Only a plain enum
+# spelling is reported as the detail — anything else (quotes, backslashes,
+# prose) would risk breaking the JSON body, and the spelling already names
+# the failure.
+detail=$(printf '%s' "$payload" | sed -n 's/.*"error"[[:space:]]*:[[:space:]]*"\([a-z_]*\)".*/\1/p')
+if [ -n "$detail" ]; then
+    body="{\"state\":\"$state\",\"detail\":\"$detail\"}"
+fi
 curl -fsS --connect-timeout 1 --max-time 2 \
     -H 'Content-Type: application/json' \
-    -d "{\"state\":\"$state\"}" \
+    -d "$body" \
     "$MAESTRO_URL/api/sessions/$MAESTRO_SESSION_ID/activity" \
     >/dev/null 2>&1 || true
 exit 0

crates/maestro-hooks/src/tests.rs

@@ -7,7 +7,7 @@ use std::process::{Command, Stdio};
 
 use super::*;
 
-fn sh(script: &str, args: &[&str], envs: &[(&str, &str)]) -> std::process::Output {
+fn sh(script: &str, args: &[&str], envs: &[(&str, &str)], payload: &[u8]) -> std::process::Output {
     let mut cmd = Command::new("/bin/sh");
     // `sh -c CMD NAME ARGS…`: NAME fills $0, so the real arguments start at $1.
     let mut argv = vec!["-c", script, HOOK_MARKER];
@@ -26,21 +26,48 @@ fn sh(script: &str, args: &[&str], envs: &[(&str, &str)]) -> std::process::Outpu
         .spawn()
         .expect("spawn /bin/sh");
     // Feed a Claude-Code-style payload on stdin; the script must drain it.
-    child
-        .stdin
-        .take()
-        .unwrap()
-        .write_all(br#"{"session_id":"x"}"#)
-        .ok();
+    child.stdin.take().unwrap().write_all(payload).ok();
     child.wait_with_output().expect("wait")
 }
 
+const SESSION: &str = "01234567-89ab-cdef-0123-456789abcdef";
+
+/// Accept exactly one HTTP request on a throwaway listener, answer 204, and
+/// hand back the raw request text. Runs `run` with the base URL once the
+/// acceptor thread is in place.
+fn capture_request(run: impl FnOnce(String) -> std::process::Output) -> String {
+    let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+    let addr = listener.local_addr().unwrap();
+    let handle = std::thread::spawn(move || {
+        let (mut sock, _) = listener.accept().unwrap();
+        let mut buf = [0u8; 4096];
+        let n = sock.read(&mut buf).unwrap();
+        sock.write_all(b"HTTP/1.1 204 No Content\r\nContent-Length: 0\r\n\r\n")
+            .unwrap();
+        String::from_utf8_lossy(&buf[..n]).to_string()
+    });
+    let out = run(format!("http://{addr}"));
+    assert!(out.status.success(), "{:?}", out.stderr);
+    handle.join().unwrap()
+}
+
+fn session_envs(url: &str) -> Vec<(&'static str, String)> {
+    vec![
+        ("MAESTRO_URL", url.to_string()),
+        ("MAESTRO_SESSION_ID", SESSION.to_string()),
+    ]
+}
+
+fn owned_envs<'a>(envs: &'a [(&'static str, String)]) -> Vec<(&'static str, &'a str)> {
+    envs.iter().map(|(k, v)| (*k, v.as_str())).collect()
+}
+
 /// The hook must be invisible outside maestro: no env vars (#103 unset) ⇒
 /// exit 0, no output, stdin drained.
 #[test]
 fn script_exits_silently_without_maestro_env() {
     for (event, _) in HOOK_EVENTS {
-        let out = sh(HOOK_SCRIPT, &[event], &[]);
+        let out = sh(HOOK_SCRIPT, &[event], &[], br#"{"session_id":"x"}"#);
         assert!(out.status.success(), "{event:?}: {:?}", out.stderr);
         assert!(out.stdout.is_empty(), "{event:?}: {:?}", out.stdout);
         assert!(out.stderr.is_empty(), "{event:?}: {:?}", out.stderr);
@@ -51,46 +78,82 @@ fn script_exits_silently_without_maestro_env() {
 /// activity endpoint and still exits 0.
 #[test]
 fn script_posts_mapped_state_to_the_activity_endpoint() {
-    let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
-    let addr = listener.local_addr().unwrap();
-    let server = move || {
-        let (mut sock, _) = listener.accept().unwrap();
-        let mut buf = [0u8; 4096];
-        let n = sock.read(&mut buf).unwrap();
-        let raw = String::from_utf8_lossy(&buf[..n]).to_string();
-        sock.write_all(b"HTTP/1.1 204 No Content\r\nContent-Length: 0\r\n\r\n")
-            .unwrap();
-        raw
-    };
-    let handle = std::thread::spawn(server);
-
-    let url = format!("http://{addr}");
-    let session = "01234567-89ab-cdef-0123-456789abcdef";
     // The installer bakes the mapped state into the command's argv; the
     // script relays whatever it is given.
-    let out = sh(
-        HOOK_SCRIPT,
-        &["Active"],
-        &[("MAESTRO_URL", &url), ("MAESTRO_SESSION_ID", session)],
-    );
-    assert!(out.status.success());
-
-    let request = handle.join().unwrap();
+    let request = capture_request(|url| {
+        sh(
+            HOOK_SCRIPT,
+            &["Active"],
+            &owned_envs(&session_envs(&url)),
+            br#"{"session_id":"x"}"#,
+        )
+    });
     assert!(request.starts_with("POST "), "{request}");
     assert!(
-        request.contains(&format!("/api/sessions/{session}/activity")),
+        request.contains(&format!("/api/sessions/{SESSION}/activity")),
         "{request}"
     );
     assert!(request.contains(r#""state":"Active""#), "{request}");
 }
 
-/// Every event maps to the state the issue specifies.
+/// Every event maps to the state the contract specifies.
 #[test]
 fn event_state_mapping_matches_the_contract() {
     let map: std::collections::HashMap<&str, &str> = HOOK_EVENTS.into_iter().collect();
+    assert_eq!(map["PreToolUse"], "Active");
     assert_eq!(map["PostToolUse"], "Active");
-    assert_eq!(map["Stop"], "AwaitingInput");
     assert_eq!(map["Notification"], "AwaitingInput");
+    assert_eq!(map["Stop"], "AwaitingInput");
+    assert_eq!(map["StopFailure"], "Error");
+}
+
+/// A `StopFailure` payload names the API error that ended the turn; the
+/// script reports its `error` spelling as the report's `detail` so a card
+/// can show why (#114).
+#[test]
+fn script_reports_the_error_spelling_as_detail() {
+    let request = capture_request(|url| {
+        sh(
+            HOOK_SCRIPT,
+            &["Error"],
+            &owned_envs(&session_envs(&url)),
+            br#"{"session_id":"abc","hook_event_name":"StopFailure","error":"rate_limit","error_details":"429 Too Many Requests"}"#,
+        )
+    });
+    assert!(request.contains(r#""state":"Error""#), "{request}");
+    assert!(request.contains(r#""detail":"rate_limit""#), "{request}");
+}
+
+/// An `error` value that is not a plain enum spelling (or a payload without
+/// one at all) must never produce a broken body — no detail is posted.
+#[test]
+fn script_posts_no_detail_for_an_unexpected_error_value() {
+    let request = capture_request(|url| {
+        sh(
+            HOOK_SCRIPT,
+            &["Error"],
+            &owned_envs(&session_envs(&url)),
+            br#"{"hook_event_name":"StopFailure","error":"429 \"Too Many\" \\ requests"}"#,
+        )
+    });
+    assert!(request.contains(r#""state":"Error""#), "{request}");
+    assert!(!request.contains("detail"), "{request}");
+}
+
+/// Events whose payload carries no error fields post a bare body — never an
+/// empty or stale detail.
+#[test]
+fn script_posts_no_detail_for_events_without_an_error() {
+    let request = capture_request(|url| {
+        sh(
+            HOOK_SCRIPT,
+            &["AwaitingInput"],
+            &owned_envs(&session_envs(&url)),
+            br#"{"hook_event_name":"Stop","stop_hook_active":false}"#,
+        )
+    });
+    assert!(request.contains(r#""state":"AwaitingInput""#), "{request}");
+    assert!(!request.contains("detail"), "{request}");
 }
 
 /// A dead or unreachable daemon must never fail — or slow down — a session.
@@ -104,6 +167,7 @@ fn script_ignores_daemon_failure() {
             ("MAESTRO_URL", "http://127.0.0.1:1"),
             ("MAESTRO_SESSION_ID", "00000000-0000-0000-0000-000000000000"),
         ],
+        br#"{"session_id":"x"}"#,
     );
     assert!(out.status.success());
 }
@@ -138,9 +202,10 @@ fn fresh_install_registers_every_event() {
     install(&settings_path(home), &script_path(home)).unwrap();
 
     let cmds = installed_commands(&settings_path(home));
-    assert_eq!(cmds.len(), 3);
+    assert_eq!(cmds.len(), HOOK_EVENTS.len());
     let joined = cmds.join("\n");
-    assert!(joined.contains("Active"));
+    assert_eq!(joined.matches("Active").count(), 2);
+    assert!(joined.contains("Error"));
     assert_eq!(joined.matches("AwaitingInput").count(), 2);
     for cmd in &cmds {
         assert!(cmd.contains(SCRIPT_FILE_NAME));
@@ -158,7 +223,10 @@ fn install_is_idempotent() {
     install(&settings_path(home), &script_path(home)).unwrap();
     let twice = std::fs::read_to_string(settings_path(home)).unwrap();
     assert_eq!(once, twice);
-    assert_eq!(installed_commands(&settings_path(home)).len(), 3);
+    assert_eq!(
+        installed_commands(&settings_path(home)).len(),
+        HOOK_EVENTS.len()
+    );
 }
 
 /// An older maestro entry under the same events is updated in place, not
@@ -188,7 +256,11 @@ fn install_updates_an_older_maestro_hook_in_place() {
     install(&settings, &new_script).unwrap();
 
     let cmds = installed_commands(&settings);
-    assert_eq!(cmds.len(), 3, "old entry replaced, not kept: {cmds:?}");
+    assert_eq!(
+        cmds.len(),
+        HOOK_EVENTS.len(),
+        "old entry replaced, not kept: {cmds:?}"
+    );
     assert!(!cmds.iter().any(|c| c == old_script));
     let root: serde_json::Value =
         serde_json::from_str(&std::fs::read_to_string(&settings).unwrap()).unwrap();
@@ -231,11 +303,11 @@ fn install_preserves_foreign_hooks_and_removes_stale_maestro_ones() {
     assert_eq!(pre[0]["hooks"][0]["command"], "my-own-linter.sh");
     // Stale maestro event gone.
     assert!(root["hooks"].get("UserPromptSubmit").is_none());
-    // Our three events present, nothing else maestro-related anywhere.
+    // Our events present, nothing else maestro-related anywhere.
     let cmds = installed_commands(&settings);
     assert_eq!(
         cmds.iter().filter(|c| c.contains(HOOK_MARKER)).count(),
-        3,
+        HOOK_EVENTS.len(),
         "{cmds:?}"
     );
 }

crates/maestro-tui/src/sidebar.rs

@@ -160,12 +160,26 @@ impl Sidebar {
             spans.push(Span::styled(" ", base));
             spans.push(Span::styled(format_state_duration(d), dot_style));
         }
+        // The trailing fragments are measured up front so a long detail
+        // truncates ahead of them instead of pushing them off the line
+        // (docs/SIDEBAR.md).
+        let mut tail: Vec<Span<'static>> = Vec::new();
         if let Some(b) = blocked {
-            spans.push(Span::styled(format!(" ⚠ {b}"), muted));
+            tail.push(Span::styled(format!(" ⚠ {b}"), muted));
         }
         if dead {
-            spans.push(Span::styled(" exited", muted));
+            tail.push(Span::styled(" exited", muted));
         }
+        if let Some(detail) = s.activity_detail.as_deref().filter(|d| !d.is_empty()) {
+            let head_w: usize = spans.iter().map(|sp| sp.width()).sum();
+            let tail_w: usize = tail.iter().map(|sp| sp.width()).sum();
+            let budget = width.saturating_sub(head_w + tail_w);
+            spans.extend(fit_to_width(
+                vec![Span::styled(format!(" {detail}"), muted)],
+                budget,
+            ));
+        }
+        spans.extend(tail);
         Some(fit_to_width(spans, width))
     }
 }
@@ -531,6 +545,93 @@ mod tests {
         );
     }
 
+    /// #112: the agent-reported detail sits right after the duration on the
+    /// meta line, in the muted style (docs/SIDEBAR.md).
+    #[test]
+    fn errored_session_shows_its_reported_detail_on_the_meta_line() {
+        let mut s = session_named(1, "claude");
+        s.activity = ActivityState::Error;
+        s.activity_since = Utc::now() - Duration::seconds(90);
+        s.activity_detail = Some("cargo build failed".into());
+        let sb = Sidebar {
+            sessions: vec![s],
+            highlight: None,
+            attached: Default::default(),
+        };
+        let all = rows(&draw(&sb, 40, 8));
+        let idx = all.iter().position(|l| l.contains("claude")).unwrap();
+        let meta = &all[idx + 1];
+        assert!(meta.contains('●'), "meta line carries the dot: {meta:?}");
+        assert!(
+            meta.contains("1m"),
+            "duration precedes the detail: {meta:?}"
+        );
+        assert!(
+            meta.contains("cargo build failed"),
+            "reported detail must render: {meta:?}"
+        );
+    }
+
+    /// A fresh Error report earns line 2 on its own (contract rule 4), with
+    /// the detail even though no duration has accrued.
+    #[test]
+    fn fresh_errored_session_earns_a_meta_line_for_its_detail() {
+        let mut s = session_named(1, "claude");
+        s.activity = ActivityState::Error;
+        s.activity_since = Utc::now() - Duration::seconds(5);
+        s.activity_detail = Some("waiting for approval".into());
+        let sb = Sidebar {
+            sessions: vec![s],
+            highlight: None,
+            attached: Default::default(),
+        };
+        let all = rows(&draw(&sb, 40, 8));
+        let idx = all.iter().position(|l| l.contains("claude")).unwrap();
+        assert!(
+            all[idx + 1].contains("waiting for approval"),
+            "detail must render on a fresh report's own meta line: {:?}",
+            all[idx + 1]
+        );
+    }
+
+    /// #112 via docs/SIDEBAR.md: the detail truncates with `…` ahead of the
+    /// trailing fragments — a long detail never pushes blocked work or
+    /// `exited` off the line, and never wraps.
+    #[test]
+    fn long_detail_yields_to_blocked_work_and_exited() {
+        let mut s = session_named(1, "claude");
+        s.status = SessionStatus::Dead;
+        s.activity_since = Utc::now() - Duration::seconds(5);
+        s.activity_detail =
+            Some("an absurdly long error message that cannot possibly fit ".repeat(3));
+        s.blocked_work = Some(InTheWay {
+            unpushed_commits: 2,
+            ..InTheWay::default()
+        });
+        let sb = Sidebar {
+            sessions: vec![s],
+            highlight: None,
+            attached: Default::default(),
+        };
+        let all = rows(&draw(&sb, 40, 8));
+        let idx = all.iter().position(|l| l.contains("claude")).unwrap();
+        let meta = content(&all[idx + 1]);
+        assert!(meta.contains('…'), "truncated detail ends with …: {meta:?}");
+        assert!(
+            meta.contains("2 unpushed commits"),
+            "blocked work stays on the line: {meta:?}"
+        );
+        assert!(
+            meta.contains("exited"),
+            "exited fragment stays on the line: {meta:?}"
+        );
+        assert!(
+            content(&all[idx + 2]).trim().is_empty(),
+            "meta line must not wrap: {:?}",
+            all[idx + 2]
+        );
+    }
+
     /// docs/SIDEBAR.md: a payload predating #102 carries an epoch
     /// `activity_since` and so contributes no duration — a card must not claim
     /// the session has been idle since 1970. The dot still renders when some

docs/SIDEBAR.md

@@ -5,8 +5,7 @@ sidebar (#107) and the TUI sidebar (#108) describe a session the same way.
 Read this before changing either. Both clients implement exactly what is
 written here; if it needs to change, change it here first.
 
-A card has **line 1** always and **line 2** only when line 2 has something to
-say.
+A card is always two lines: **line 1** and **line 2**.
 
 ## Line 1 — name + actions
 
@@ -25,41 +24,46 @@ badge move off this row into line 2.
 
 ## Line 2 — meta line (adaptive)
 
-Rendered only when at least one of these holds:
+Line 2 always renders — never an empty placeholder row either, since its
+unconditional fragments (see below) always have something to show. Its
+*fragments* are adaptive: some show only when their trigger holds. The line
+itself is not.
 
-1. The session has been held in its current activity state longer than
-   **30 seconds** (`activity_since` from #102). A freshly-active session
-   stays one line.
-2. Its worktree holds blocked work: `blocked_work` is `Some` and not clear
-   (`InTheWay::is_clear()`), rendered in `formatInTheWay`'s phrasing on web
-   and as `⚠ <summary>` on the TUI.
-3. It has exited: `status == Dead`.
-4. An agent-reported state (#105) of `Error` is in force (see Precedence).
-
-Otherwise line 2 is absent — never an empty placeholder row.
-
-When present, line 2 reads left to right:
+Line 2 reads left to right:
 
 ```
-<dot> <duration> [<detail>] [<blocked work> | exited] [<command>]
+<dot> [<duration>] [<detail>] [<blocked work> | exited] <command>
 ```
 
+Its minimum content is therefore the dot and the command.
+
 `<dot>` is a single filled glyph (`●` on both clients) carrying the activity
-state's colour, and `<duration>` follows in the same colour. There is no state
-word and no second badge: the dot exists so the state is still legible when a
-row is dimmed or the terminal renders the duration in the default fg. The dot
-and duration are unconditional parts of line 2; the bracketed fragments appear
-only when their trigger holds. A payload that predates #102 (no usable
-`activity_since`) contributes no duration — the dot still renders.
+state's colour, and `<duration>` follows in the same colour when shown. There
+is no state word and no second badge: the dot exists so the state is still
+legible when a row is dimmed or the terminal renders the duration in the
+default fg. The dot is an unconditional part of line 2; the bracketed
+fragments appear only when their trigger holds.
+
+`<duration>` renders only once the session has been held in its current
+activity state longer than **30 seconds** (`activity_since` from #102) — under
+that threshold the duration is absent and the dot renders alone. A payload
+that predates #102 (no usable `activity_since`) likewise contributes no
+duration — the dot still renders. This rule now governs only the duration
+fragment; it no longer decides whether line 2 exists.
 
 `<detail>` is an agent-reported string (#105) — e.g. why a session is in
 `Error`. It sits right after the duration, in the muted style, and shows only
 while an agent-reported state is in force (see Precedence): when the report
-lapses at its TTL or is replaced, the detail goes with it.
+lapses at its TTL or is replaced, the detail goes with it. The detail
+truncates with `…` ahead of the trailing fragments — a long detail never
+pushes `<blocked work>`, `exited`, or `<command>` off the line, and neither
+client ever lets it wrap.
 
-`<command>` is optional and muted: the session's command line, shown only when
-the rendered name came from `metadata.name` and differs from the command (the
-web has always surfaced this; the TUI may omit it).
+`<command>` is unconditional and muted: the session's command line, shown on
+every card in both clients — no omission in the TUI, no name-vs-command
+comparison gating it. A session named by its command line then shows the same
+string on both lines; that is accepted, the price of a row that never changes
+height.
 
 ## Colour per activity state
 
@@ -104,6 +108,20 @@ When the TTL expires, inference resumes and the session's reported detail —
 if any — clears with the report. Clients never blend the two: whichever source
 is in force supplies both the colour and the clock for `activity_since`.
 
+Two rulings specific to a reported `Error` (#114):
+
+- **The five-minute TTL applies to `Error` like to any other state.** A
+  session that failed is still failed after five minutes, but a card pinned
+  red forever lies once the session moves on; when the report lapses the card
+  returns to the daemon's own inference — usually `Idle` for a session that
+  has gone quiet.
+- **Only a new report clears an `Error` before its TTL.** The next
+  `ActivityState` of any kind replaces it (with #106's hook that is typically
+  `PreToolUse` → `Active` when the user prompts again). PTY output and
+  process changes do not clear it — only the agent itself may withdraw what
+  the agent itself reported. Re-reporting `Error` extends the TTL rather than
+  stacking reports.
+
 If a client receives an `ActivityState` variant it does not know, it must not
 fail rendering: treat it as `Idle` (neutral/dim, line-2 rules apply as usual)
 until the daemon sends a variant it does know. Rust clients deserialize

web/src/catalog.test.ts

@@ -105,6 +105,38 @@ describe("blocked-work indicator (#83)", () => {
   });
 });
 
+describe("agent-reported detail (#112)", () => {
+  const ago = (ms: number): string => new Date(Date.now() - ms).toISOString();
+
+  it("renders the reported detail right after the duration on line 2", () => {
+    const s = session({
+      id: "aaaaaaaa-0000-0000-0000-000000000020",
+      status: "Dead",
+      activity: "Error",
+      activity_since: ago(90_000),
+      activity_detail: "cargo build failed",
+    });
+    const el = renderSidebar(storeWith([s])).el;
+    const line2 = rowFor(el, s.id)?.querySelector<HTMLElement>(".card-line2");
+    expect(line2?.querySelector(".activity-detail")?.textContent).toBe("cargo build failed");
+    const order = [...line2!.children].map((c) => c.className);
+    expect(order.indexOf("activity-detail")).toBeGreaterThan(order.indexOf("activity-duration"));
+    expect(order.indexOf("activity-detail")).toBeLessThan(
+      order.findIndex((c) => c.startsWith("card-flag")),
+    );
+  });
+
+  it("omits the detail when no report is in force", () => {
+    const s = session({
+      id: "aaaaaaaa-0000-0000-0000-000000000021",
+      activity: "Active",
+      activity_since: ago(90_000),
+    });
+    const el = renderSidebar(storeWith([s])).el;
+    expect(rowFor(el, s.id)?.querySelector(".activity-detail")).toBeNull();
+  });
+});
+
 describe("session cards (#107)", () => {
   const ago = (ms: number): string => new Date(Date.now() - ms).toISOString();
 

web/src/catalog.ts

@@ -42,6 +42,9 @@ function metaLine(s: Session, now: number): string {
   const fragments = [
     `<span class="activity-dot" role="img" title="${escapeHtml(stateWord)}" aria-label="${escapeHtml(stateWord)}"></span>`,
     duration ? `<span class="activity-duration">${duration}</span>` : "",
+    s.activity_detail
+      ? `<span class="activity-detail">${escapeHtml(s.activity_detail)}</span>`
+      : "",
     blockers
       ? `<span class="card-flag leaf-blocked" title="Kill will be refused unless forced">⚠ ${escapeHtml(formatInTheWay(blockers))}</span>`
       : "",

web/src/styles.css

@@ -851,6 +851,17 @@ textarea {
   flex: 0 0 auto;
 }
 
+/* Agent-reported detail (#112): sits after the duration, shrinks with an
+   ellipsis so it never pushes the trailing fragments off the line. */
+.activity-detail {
+  color: var(--faint);
+  flex: 0 1 auto;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
 /* Blocked-work / exited / command fragments recede: the ⚠ glyph already
    signals severity and "exited" dims with the row. */
 .card-flag {