refactor(maestro): drop cleanup_on_kill from the wire and the CLI

Nothing has honoured WorktreeSpec.cleanup_on_kill since #56, and after
#79 and #81 survival is decided by what is in a worktree, not by what
the spawn asked for. A field that lies is worse than a missing one.

Removes the field from the protocol, the --cleanup-on-kill flag from
the CLI, and the tests asserting its default.

crates/maestro-cli/src/cli.rs

@@ -102,11 +102,6 @@ pub struct SpawnArgs {
     /// there.
     #[arg(long)]
     pub existing_branch: bool,
-    /// Remove the worktree when the session is killed. Kept for wire
-    /// compatibility (#56): the daemon now always cleans up on kill, guarded
-    /// against unsaved work.
-    #[arg(long, default_value_t = true)]
-    pub cleanup_on_kill: bool,
     /// After spawning, attach immediately.
     #[arg(long, short = 'a')]
     pub attach: bool,
@@ -125,6 +120,11 @@ pub struct AttachArgs {
 pub struct KillArgs {
     /// Session ID to kill.
     pub session_id: Uuid,
+    /// End the session even when its worktree holds unsaved work (#81). The
+    /// worktree is retained — never removed — and enters the retained store;
+    /// the output says where the work went.
+    #[arg(long)]
+    pub force: bool,
 }
 
 fn parse_kv(s: &str) -> Result<(String, String), String> {
@@ -163,7 +163,6 @@ mod tests {
             "/repos/foo",
             "--branch",
             "feat/x",
-            "--cleanup-on-kill",
             "-e",
             "FOO=bar",
             "-e",
@@ -174,7 +173,6 @@ mod tests {
             Command::Spawn(a) => {
                 assert_eq!(a.command, "bash");
                 assert_eq!(a.branch.as_deref(), Some("feat/x"));
-                assert!(a.cleanup_on_kill);
                 assert_eq!(
                     a.env,
                     vec![("FOO".into(), "bar".into()), ("BAZ".into(), "qux".into()),]
@@ -184,27 +182,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn cleanup_on_kill_defaults_true_for_the_wire() {
-        let cli = Cli::try_parse_from([
-            "maestro",
-            "spawn",
-            "--cwd",
-            "/tmp",
-            "--command",
-            "bash",
-            "--worktree-from",
-            "/repos/foo",
-            "--branch",
-            "feat/x",
-        ])
-        .unwrap();
-        match cli.command {
-            Command::Spawn(a) => assert!(a.cleanup_on_kill),
-            _ => panic!("wrong subcommand"),
-        }
-    }
-
     /// Review fix: without a flag the CLI always sent `create_branch: true`,
     /// so the daemon's existing-branch path was unreachable and spawning onto
     /// a branch that already existed just failed.
@@ -256,6 +233,32 @@ mod tests {
         }
     }
 
+    #[test]
+    fn parses_kill_with_force() {
+        let id = "01234567-89ab-cdef-0123-456789abcdef";
+        let cli = Cli::try_parse_from(["maestro", "kill", "--force", id]).unwrap();
+        match cli.command {
+            Command::Kill(a) => {
+                assert!(a.force);
+                assert_eq!(a.session_id.to_string(), id);
+            }
+            _ => panic!("wrong subcommand"),
+        }
+    }
+
+    #[test]
+    fn kill_force_defaults_false() {
+        let id = "01234567-89ab-cdef-0123-456789abcdef";
+        let cli = Cli::try_parse_from(["maestro", "kill", id]).unwrap();
+        match cli.command {
+            Command::Kill(a) => {
+                assert!(!a.force);
+                assert_eq!(a.session_id.to_string(), id);
+            }
+            _ => panic!("wrong subcommand"),
+        }
+    }
+
     #[test]
     fn rejects_env_without_equals() {
         let err = Cli::try_parse_from([

crates/maestro-cli/src/dispatch.rs

@@ -62,8 +62,15 @@ pub async fn dispatch(
             run_attach_url(&daemon.attach_url(args.session_id)?, detach).await?;
         }
         Command::Kill(args) => {
-            run_kill(&daemon, &args).await?;
+            let outcome = run_kill(&daemon, &args).await?;
             println!("killed {}", args.session_id);
+            if let Some(w) = outcome.retained {
+                println!(
+                    "worktree retained at {} (branch {}, force-killed)",
+                    w.path.display(),
+                    w.branch
+                );
+            }
         }
         Command::Worktrees(args) => match args.command {
             WorktreesCommand::List(list_args) => {

crates/maestro-cli/src/sessions.rs

@@ -43,7 +43,6 @@ pub async fn run_spawn(client: &DaemonClient, args: SpawnArgs) -> Result<Session
         (Some(repo), Some(branch)) => Some(WorktreeSpec {
             base_repo: repo.clone(),
             branch: branch.clone(),
-            cleanup_on_kill: args.cleanup_on_kill,
             create_branch: !args.existing_branch,
         }),
         _ => None,
@@ -59,9 +58,14 @@ pub async fn run_spawn(client: &DaemonClient, args: SpawnArgs) -> Result<Session
     client.create_session(&body).await
 }
 
-/// `maestro kill`
-pub async fn run_kill(client: &DaemonClient, args: &KillArgs) -> Result<(), ClientError> {
-    client.kill_session(args.session_id).await
+/// `maestro kill`. A forced kill (#81) retains the guarded worktree instead
+/// of removing it; the outcome names what was kept so dispatch can say where
+/// the work went.
+pub async fn run_kill(
+    client: &DaemonClient,
+    args: &KillArgs,
+) -> Result<maestro_protocol::KillOutcome, ClientError> {
+    client.kill_session(args.session_id, args.force).await
 }
 
 #[allow(clippy::write_literal)]

crates/maestro-cli/tests/against_mock_daemon.rs

@@ -76,7 +76,7 @@ async fn killing_an_unknown_session_reports_the_daemon_reason() {
 
     let err = mock
         .client()
-        .kill_session(Uuid::new_v4())
+        .kill_session(Uuid::new_v4(), false)
         .await
         .expect_err("should fail");
 
@@ -102,6 +102,9 @@ async fn spawn_round_trips_through_the_daemon() {
     assert_eq!(created.command, "bash");
     assert_eq!(mock.session_count(), 1);
 
-    mock.client().kill_session(created.id).await.expect("kill");
+    mock.client()
+        .kill_session(created.id, false)
+        .await
+        .expect("kill");
     assert_eq!(mock.session_count(), 0);
 }

crates/maestro-daemon/src/cli.rs

@@ -56,6 +56,9 @@ async fn run(config_override: Option<PathBuf>) -> Result<(), Box<dyn Error>> {
         Some(p) => Tmux::new().with_tmpdir(p),
         None => Tmux::new(),
     };
+    let retained = std::sync::Arc::new(crate::retained_store::RetainedStore::new(
+        config.retained_worktree_dir(),
+    ));
     let manager = SessionManager::new_with_replay(
         std::sync::Arc::new(tmux),
         sidecar,
@@ -66,7 +69,10 @@ async fn run(config_override: Option<PathBuf>) -> Result<(), Box<dyn Error>> {
     .with_spawn_history(crate::spawn_history::SpawnHistory::new(
         config.spawn_history_path(),
         config.spawn_history_days,
-    ));
+    ))
+    // One store instance shared with the API handlers: forced kills (#81)
+    // record here, `GET /api/worktrees` (#80) reads back from here.
+    .with_retained_store((*retained).clone());
 
     let recovered = manager.recover().await?;
     tracing::info!(recovered, "adopted existing tmux sessions");
@@ -85,9 +91,7 @@ async fn run(config_override: Option<PathBuf>) -> Result<(), Box<dyn Error>> {
         config.home_dir.clone(),
         config.spawn_presets.clone(),
         projects,
-        std::sync::Arc::new(crate::retained_store::RetainedStore::new(
-            config.retained_worktree_dir(),
-        )),
+        retained,
     ));
 
     let listener = TcpListener::bind(config.bind_addr).await?;

crates/maestro-daemon/src/local_api.rs

@@ -101,6 +101,8 @@ fn session_error_status(code: &str) -> StatusCode {
         "invalid_env" => StatusCode::BAD_REQUEST,
         // A guard refusal is the daemon doing its job, not a failure (#79).
         "kill_guarded" => StatusCode::CONFLICT,
+        // The retention record failed before anything was torn down (#81).
+        "retain_failed" => StatusCode::INTERNAL_SERVER_ERROR,
         _ => StatusCode::BAD_GATEWAY,
     }
 }
@@ -179,9 +181,29 @@ async fn create_session(
 /// The full error info is passed through rather than rebuilt from
 /// code + message: a `kill_guarded` refusal (#79) carries the unsaved-work
 /// breakdown clients render as "3 uncommitted files, 2 unpushed commits".
-async fn kill_session(State(s): State<LocalApiState>, Path(id): Path<Uuid>) -> Response {
-    match s.manager.kill(id).await {
-        Ok(()) => StatusCode::NO_CONTENT.into_response(),
+///
+/// With `force=true` (#81) the refusal is overridden and the worktree
+/// retained; the answer is `200` with a [`KillOutcome`] naming what was kept.
+/// Without it the historical `204` stands.
+#[derive(Debug, Deserialize)]
+struct KillQuery {
+    #[serde(default)]
+    force: bool,
+}
+
+async fn kill_session(
+    State(s): State<LocalApiState>,
+    Path(id): Path<Uuid>,
+    Query(q): Query<KillQuery>,
+) -> Response {
+    match s.manager.kill(id, q.force).await {
+        Ok(outcome) => {
+            if q.force {
+                (StatusCode::OK, Json(outcome)).into_response()
+            } else {
+                StatusCode::NO_CONTENT.into_response()
+            }
+        }
         Err(e) => {
             let info = e.to_error_info();
             let status = session_error_status(&info.code);

crates/maestro-daemon/src/session.rs

@@ -12,8 +12,8 @@ use std::time::Duration;
 
 use chrono::Utc;
 use maestro_protocol::{
-    ActivityState, CatalogEvent, CreateSessionRequest, ErrorInfo, Session, SessionStatus,
-    WorktreeSpec,
+    ActivityState, CatalogEvent, CreateSessionRequest, ErrorInfo, KillOutcome, RetainedReason,
+    RetainedWorktree, Session, SessionStatus, WorktreeSpec,
 };
 use tokio::sync::{broadcast, Mutex};
 use uuid::Uuid;
@@ -44,6 +44,11 @@ pub struct SessionRecord {
     /// `base_repo` from the original `WorktreeSpec`. Needed because `git
     /// worktree remove` is invoked from the base repo.
     pub worktree_base_repo: Option<PathBuf>,
+    /// Branch the worktree was created for, recorded at spawn time so a
+    /// forced kill (#81) can name it in the retained store without asking
+    /// git. Sessions adopted from a sidecar have no branch on record and
+    /// fall back to a probe.
+    pub worktree_branch: Option<String>,
     pub bridge: PtyBridge,
 }
 
@@ -66,6 +71,11 @@ pub enum SessionError {
     /// so it stays the operator's handle on their own unfinished work.
     #[error("kill refused: the session's worktree holds unsaved work ({0})")]
     KillGuarded(maestro_protocol::InTheWay),
+    /// A forced kill (#81) records the retained worktree *before* tearing
+    /// anything down; if that write fails nothing was destroyed, and the
+    /// error says so rather than silently dropping unrecorded work.
+    #[error("could not record the retained worktree: {0}")]
+    RetainFailed(String),
 }
 
 impl SessionError {
@@ -78,6 +88,7 @@ impl SessionError {
             SessionError::NotFound(_) => "not_found",
             SessionError::InvalidEnv(_) => "invalid_env",
             SessionError::KillGuarded(_) => "kill_guarded",
+            SessionError::RetainFailed(_) => "retain_failed",
         };
         let unsaved_work = match self {
             SessionError::KillGuarded(b) => Some(*b),
@@ -110,6 +121,9 @@ struct Inner {
     /// `None` when not wired (tests, or before `with_spawn_history`); a present
     /// but disabled (`0`-day) history no-ops internally.
     spawn_history: Option<SpawnHistory>,
+    /// Retained-worktree store (#78). `None` when not wired (tests); a forced
+    /// kill (#81) without one fails rather than destroying unrecorded work.
+    retained: Option<crate::retained_store::RetainedStore>,
     sessions: Mutex<HashMap<Uuid, SessionRecord>>,
     events: broadcast::Sender<CatalogEvent>,
 }
@@ -148,6 +162,7 @@ impl SessionManager {
                 fifo_dir,
                 replay_bytes,
                 spawn_history: None,
+                retained: None,
                 sessions: Mutex::new(HashMap::new()),
                 events,
             }),
@@ -170,6 +185,16 @@ impl SessionManager {
         self
     }
 
+    /// Attach the retained-worktree store (#78). A forced kill (#81) needs it
+    /// to record what it retained; without one, forcing a guarded kill fails
+    /// instead of destroying unrecorded work.
+    pub fn with_retained_store(mut self, store: crate::retained_store::RetainedStore) -> Self {
+        let inner = Arc::get_mut(&mut self.inner)
+            .expect("with_retained_store must be called before the SessionManager is cloned");
+        inner.retained = Some(store);
+        self
+    }
+
     /// Recent working dirs for the spawn form's picker (#24), newest-first and
     /// deduped by dir. Empty when no history is wired or it's disabled.
     pub fn recent_dirs(&self) -> Vec<RecentDir> {
@@ -340,6 +365,7 @@ impl SessionManager {
                     fifo_path,
                     worktree_path,
                     worktree_base_repo,
+                    worktree_branch: req.worktree.as_ref().map(|w| w.branch.clone()),
                     bridge,
                 },
             );
@@ -391,11 +417,17 @@ impl SessionManager {
     /// work, so ending a session that still matters becomes a deliberate
     /// `--force`, which retains rather than destroys (WORKTREES.md).
     ///
+    /// With `force` (#81) the refusal — and nothing else — is overridden:
+    /// the session ends and the guarded worktree is retained into the store
+    /// with reason `force-killed`, never removed. The outcome names what was
+    /// kept so a client can say where the work went. A tree whose guard is
+    /// clear never needed the override; force removes it as usual.
+    ///
     /// This is also how an already-dead session is dismissed. tmux is only
     /// asked to kill something it still has — calling `kill-session` on a
     /// session tmux already lost fails, and that failure is not interesting.
-    pub async fn kill(&self, id: Uuid) -> Result<(), SessionError> {
-        let (worktree, alive) = {
+    pub async fn kill(&self, id: Uuid, force: bool) -> Result<KillOutcome, SessionError> {
+        let (worktree, alive, known_branch) = {
             let sessions = self.inner.sessions.lock().await;
             match sessions.get(&id) {
                 None => return Err(SessionError::NotFound(id)),
@@ -405,26 +437,75 @@ impl SessionManager {
                         .clone()
                         .zip(record.worktree_path.clone()),
                     record.session.status == SessionStatus::Running,
+                    record.worktree_branch.clone(),
                 ),
             }
         };
-        // The guard runs before anything is torn down: refusing must leave the
-        // session running, exactly as the operator left it.
-        if let Some((_, path)) = worktree {
-            let probe = tmux_blocking(move || crate::worktree_probe::in_the_way(&path))
-                .await
-                .map_err(|e| SessionError::Worktree(crate::worktree::WorktreeError::from(e)))?;
-            if !probe.is_clear() {
-                return Err(SessionError::KillGuarded(probe));
+        // The probe runs before anything is torn down: both refusing (#79)
+        // and recording the retention (#81) must see the tree as it stands,
+        // and a refused kill leaves the session running as the operator left
+        // it.
+        let probe = match &worktree {
+            Some((_, path)) => {
+                let path = path.clone();
+                Some(
+                    tmux_blocking(move || crate::worktree_probe::in_the_way(&path))
+                        .await
+                        .map_err(|e| {
+                            SessionError::Worktree(crate::worktree::WorktreeError::from(e))
+                        })?,
+                )
             }
+            None => None,
+        };
+        let guarded = probe.as_ref().is_some_and(|p| !p.is_clear());
+        if guarded && !force {
+            return Err(SessionError::KillGuarded(probe.expect("guarded ⇒ probed")));
         }
+
+        // Record the retention BEFORE tearing down: a failed store write then
+        // leaves the session running and every artifact untouched, instead of
+        // ending a session whose work outlives it unrecorded.
+        let mut retained = None;
+        if guarded {
+            let store =
+                self.inner.retained.clone().ok_or_else(|| {
+                    SessionError::RetainFailed("no retained store is wired".into())
+                })?;
+            let (base_repo, path) = worktree.as_ref().expect("guarded ⇒ worktree");
+            let branch = known_branch
+                .or_else(|| crate::worktree_probe::current_branch(path))
+                .unwrap_or_default();
+            let entry = {
+                let store = store.clone();
+                let base_repo = base_repo.clone();
+                let path = path.clone();
+                tmux_blocking(move || {
+                    store.retain(&path, &base_repo, &branch, RetainedReason::ForceKilled)
+                })
+                .await
+                .map_err(|e| SessionError::RetainFailed(e.to_string()))?
+            };
+            retained = Some((entry, probe.expect("guarded ⇒ probed")));
+        }
+
         let removed = {
             let mut sessions = self.inner.sessions.lock().await;
             sessions.remove(&id)
         };
         let record = removed.ok_or(SessionError::NotFound(id))?;
-        cleanup_record(&self.inner, id, record, alive).await;
-        Ok(())
+        cleanup_record(&self.inner, id, record, alive, retained.is_some()).await;
+        Ok(KillOutcome {
+            retained: retained.map(|(entry, in_the_way)| RetainedWorktree {
+                id: entry.id,
+                path: entry.path,
+                base_repo: entry.base_repo,
+                branch: entry.branch,
+                reason: entry.reason,
+                retained_at: entry.retained_at,
+                in_the_way,
+            }),
+        })
     }
 
     /// Spawn a background task that polls tmux every `interval` and reaps any
@@ -511,6 +592,9 @@ impl SessionManager {
                     // directory blocks that branch forever (#54 review).
                     worktree_path: session.worktree.as_ref().map(|w| w.path.clone()),
                     worktree_base_repo: session.worktree.as_ref().map(|w| w.base_repo.clone()),
+                    // The sidecar carries no branch; a forced kill of a
+                    // recovered session probes git for it at retain time.
+                    worktree_branch: None,
                     bridge,
                 },
             );
@@ -750,7 +834,17 @@ async fn mark_session_dead(inner: &Arc<Inner>, id: Uuid) {
 /// gone from the authoritative in-memory map, so a stray FIFO or sidecar can't
 /// resurrect it. `kill_tmux` is `true` for an explicit kill and `false` for the
 /// liveness reaper (tmux already lost the session).
-async fn cleanup_record(inner: &Arc<Inner>, id: Uuid, record: SessionRecord, kill_tmux: bool) {
+///
+/// `retain_worktree` is `true` for a forced kill (#81) that retained the
+/// worktree instead of removing it: the store entry is already written, so
+/// only the removal is skipped.
+async fn cleanup_record(
+    inner: &Arc<Inner>,
+    id: Uuid,
+    record: SessionRecord,
+    kill_tmux: bool,
+    retain_worktree: bool,
+) {
     if kill_tmux {
         let tmux = inner.tmux.clone();
         let _ = tmux_blocking(move || tmux.kill_session(id)).await;
@@ -759,11 +853,18 @@ async fn cleanup_record(inner: &Arc<Inner>, id: Uuid, record: SessionRecord, kil
     if let Err(e) = inner.sidecar.delete(id) {
         tracing::warn!(error = ?e, %id, "cleanup: failed to delete sidecar");
     }
-    // The kill already passed the unsaved-work guard (#79), so this removal
-    // is unconditional; the manager's own nested-worktree refusal is all that
-    // can still leave a tree on disk, and it says where.
     if let (Some(base), Some(path)) = (&record.worktree_base_repo, &record.worktree_path) {
-        if let Err(e) = inner.worktree_mgr.remove(base, path) {
+        if retain_worktree {
+            tracing::info!(
+                %id,
+                path = %path.display(),
+                "forced kill: worktree retained in the store"
+            );
+        } else if let Err(e) = inner.worktree_mgr.remove(base, path) {
+            // The kill already passed the unsaved-work guard (#79), so this
+            // removal is unconditional; the manager's own nested-worktree
+            // refusal is all that can still leave a tree on disk, and it
+            // says where.
             tracing::warn!(
                 %id,
                 path = %path.display(),

crates/maestro-daemon/src/worktree_probe.rs

@@ -90,6 +90,14 @@ pub fn reclaim(base_repo: &Path, path: &Path) -> Result<(), ProbeError> {
     .map(|_| ())
 }
 
+/// Branch checked out at `path`. Sessions adopted from a sidecar carry no
+/// branch on record, so a forced kill (#81) asks the tree itself when it
+/// needs one for the retained store. `None` when git cannot answer.
+pub fn current_branch(path: &Path) -> Option<String> {
+    let out = run_git(path, ["rev-parse", "--abbrev-ref", "HEAD"]).ok()?;
+    Some(String::from_utf8_lossy(&out.stdout).trim().to_string())
+}
+
 fn run_git<I, S>(dir: &Path, args: I) -> Result<std::process::Output, ProbeError>
 where
     I: IntoIterator<Item = S>,

crates/maestro-daemon/tests/attach.rs

@@ -122,7 +122,7 @@ async fn pty_round_trip_through_real_tmux() {
         "marker not seen in {} bytes",
         got.len()
     );
-    let _ = h.manager.kill(id).await;
+    let _ = h.manager.kill(id, false).await;
 }
 
 #[tokio::test]
@@ -170,7 +170,7 @@ async fn multi_attach_broadcasts_to_every_client() {
         "client B missed marker"
     );
 
-    let _ = h.manager.kill(id).await;
+    let _ = h.manager.kill(id, false).await;
 }
 
 #[tokio::test]
@@ -219,7 +219,7 @@ async fn sends_close_frame_when_session_is_killed() {
     // give the broadcast subscriber a moment to register before killing.
     tokio::time::sleep(Duration::from_millis(100)).await;
 
-    h.manager.kill(id).await.unwrap();
+    h.manager.kill(id, false).await.unwrap();
 
     let mut saw_close = false;
     let deadline = std::time::Instant::now() + Duration::from_secs(2);
@@ -267,7 +267,7 @@ async fn ping_text_frame_gets_pong() {
         }
     }
     assert!(saw_pong, "no Pong frame received");
-    let _ = h.manager.kill(id).await;
+    let _ = h.manager.kill(id, false).await;
 }
 
 #[tokio::test]

crates/maestro-daemon/tests/common/mod.rs

@@ -176,6 +176,11 @@ impl DaemonFixture {
             manager =
                 manager.with_spawn_history(SpawnHistory::new(Self::history_path(&state_dir), days));
         }
+        // Same wiring as production: the manager records retained worktrees
+        // into the same dir the API reads back from (#78/#81).
+        let retained =
+            maestro_daemon::retained_store::RetainedStore::new(Self::retained_path(&state_dir));
+        manager = manager.with_retained_store(retained.clone());
         Self {
             tmux,
             manager,
@@ -187,6 +192,10 @@ impl DaemonFixture {
         state_dir.path().join("spawn-history.jsonl")
     }
 
+    fn retained_path(state_dir: &TempDir) -> PathBuf {
+        state_dir.path().join("retained-worktrees")
+    }
+
     pub fn spawn_history_path(&self) -> PathBuf {
         Self::history_path(&self.state_dir)
     }

crates/maestro-daemon/tests/local_api.rs

@@ -25,6 +25,13 @@ struct Harness {
     _fx: DaemonFixture,
 }
 
+impl Harness {
+    /// Store over the same dir the manager records into.
+    fn fx_retained(&self) -> maestro_daemon::retained_store::RetainedStore {
+        self._fx.retained_store()
+    }
+}
+
 async fn spawn(hostname: &str) -> Harness {
     spawn_with(
         hostname,
@@ -356,7 +363,6 @@ async fn delete_a_session_whose_worktree_holds_unsaved_work_returns_409_with_the
             worktree: Some(WorktreeSpec {
                 base_repo: repo.path().to_path_buf(),
                 branch: "feat/guarded".into(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         })
@@ -386,6 +392,61 @@ async fn delete_a_session_whose_worktree_holds_unsaved_work_returns_409_with_the
     assert!(h.manager.has(session.id).await, "the session keeps running");
 }
 
+/// `?force=true` on the wire (#81): the refusal is overridden, the session
+/// ends, and the answer is 200 with the retained worktree named — path,
+/// branch, reason — while the directory survives on disk.
+#[tokio::test]
+async fn delete_with_force_ends_the_session_and_answers_what_was_retained() {
+    let h = spawn("naps-laptop").await;
+    let repo = tempfile::TempDir::new().unwrap();
+    common::init_repo(repo.path());
+    let wt_path = repo
+        .path()
+        .join("worktrees")
+        .join("feat")
+        .join("guarded")
+        .to_path_buf();
+    let session = h
+        .manager
+        .create(CreateSessionRequest {
+            cwd: repo.path().to_path_buf(),
+            command: "sleep 60".into(),
+            env: HashMap::new(),
+            metadata: HashMap::new(),
+            worktree: Some(WorktreeSpec {
+                base_repo: repo.path().to_path_buf(),
+                branch: "feat/guarded".into(),
+                create_branch: true,
+            }),
+        })
+        .await
+        .unwrap();
+    std::fs::write(wt_path.join("README"), b"unsaved edits\n").unwrap();
+
+    let resp = reqwest::Client::new()
+        .delete(url(h.addr, &format!("/api/sessions/{}", session.id)))
+        .query(&[("force", "true")])
+        .send()
+        .await
+        .unwrap();
+    assert_eq!(resp.status(), reqwest::StatusCode::OK);
+    let body: maestro_protocol::KillOutcome = resp.json().await.unwrap();
+    let retained = body.retained.expect("force names what was kept");
+    assert_eq!(retained.path, wt_path);
+    assert_eq!(retained.branch, "feat/guarded");
+    assert_eq!(
+        retained.reason,
+        maestro_protocol::RetainedReason::ForceKilled
+    );
+
+    // The tree would have blocked; force must not have removed it.
+    assert!(wt_path.exists(), "a forced kill never removes the worktree");
+    // And the store entry exists, so reclaim can find it (#80).
+    let all = h.fx_retained().load_all().unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].id, retained.id);
+}
+
 #[tokio::test]
 async fn attach_ws_streams_pty_bytes() {
     let h = spawn("naps-laptop").await;
@@ -476,7 +537,7 @@ async fn events_ws_sends_a_snapshot_then_streams_deltas() {
         other => panic!("expected SessionAdded, got {other:?}"),
     }
 
-    h.manager.kill(created.id).await.expect("kill");
+    h.manager.kill(created.id, false).await.expect("kill");
 
     // Activity ticks may interleave; the removal is what we are waiting for.
     let deadline = tokio::time::Instant::now() + Duration::from_secs(5);

crates/maestro-daemon/tests/session_decisions.rs

@@ -211,7 +211,7 @@ async fn killing_a_dead_session_dismisses_it_without_touching_tmux() {
     fx.manager.start_liveness_watcher(Duration::from_millis(25));
     wait_for_status(&fx.manager, s.id, SessionStatus::Dead).await;
 
-    fx.manager.kill(s.id).await.expect("dismiss");
+    fx.manager.kill(s.id, false).await.expect("dismiss");
 
     assert!(fx.manager.snapshot().await.is_empty());
     assert!(
@@ -371,7 +371,7 @@ async fn killing_an_unknown_session_is_reported_as_not_found() {
     let fx = Fx::new();
     let err = fx
         .manager
-        .kill(uuid::Uuid::new_v4())
+        .kill(uuid::Uuid::new_v4(), false)
         .await
         .expect_err("should fail");
     assert_eq!(err.to_error_info().code, "not_found");

crates/maestro-daemon/tests/session_manager.rs

@@ -44,7 +44,7 @@ async fn create_then_kill_round_trip() {
     // FIFO should also exist
     assert!(fx.fifo_dir().join(format!("{}.fifo", session.id)).exists());
 
-    fx.manager.kill(session.id).await.expect("kill");
+    fx.manager.kill(session.id, false).await.expect("kill");
     assert!(!fx.manager.has(session.id).await);
     assert!(!fx
         .sidecar_dir()
@@ -79,7 +79,7 @@ async fn create_appends_to_spawn_history() {
     assert_eq!(recents[0].cwd, cwd.path());
     assert_eq!(recents[0].last_command, "sleep 30");
 
-    fx.manager.kill(session.id).await.expect("kill");
+    fx.manager.kill(session.id, false).await.expect("kill");
     // History is durable — it survives the kill that deletes the sidecar.
     assert_eq!(fx.manager.recent_dirs().len(), 1);
 }
@@ -185,7 +185,7 @@ async fn create_captures_initial_output_in_replay_buffer() {
         "first-line marker never reached the replay buffer — pipe-pane raced past the child's initial output",
     );
 
-    fx.manager.kill(s.id).await.unwrap();
+    fx.manager.kill(s.id, false).await.unwrap();
 }
 
 /// Regression for NAP-228: after `recover`, PTY output must reach new
@@ -251,7 +251,7 @@ async fn recover_re_pipes_pane_so_output_reaches_subscribers() {
         String::from_utf8_lossy(&buf),
     );
 
-    revived.kill(s.id).await.unwrap();
+    revived.kill(s.id, false).await.unwrap();
 }
 
 #[tokio::test]
@@ -300,7 +300,7 @@ async fn pty_broadcast_delivers_bytes_to_subscribers() {
     assert!(buf_a.windows(want.len()).any(|w| w == want), "A missed");
     assert!(buf_b.windows(want.len()).any(|w| w == want), "B missed");
 
-    fx.manager.kill(s.id).await.unwrap();
+    fx.manager.kill(s.id, false).await.unwrap();
     let _ = (cwd, PathBuf::from("/"));
 }
 
@@ -359,7 +359,7 @@ async fn liveness_watcher_marks_dead_sessions_and_keeps_them_until_dismissed() {
     );
 
     // Dismissing it is what finally releases the artifacts.
-    fx.manager.kill(s.id).await.expect("dismiss");
+    fx.manager.kill(s.id, false).await.expect("dismiss");
     assert!(!fx.manager.has(s.id).await);
     assert!(!fx.sidecar_dir().join(format!("{}.json", s.id)).exists());
     assert!(!fx.fifo_dir().join(format!("{}.fifo", s.id)).exists());
@@ -385,7 +385,6 @@ async fn kill_removes_worktree_even_when_spec_says_keep() {
             worktree: Some(WorktreeSpec {
                 base_repo: repo.path().to_path_buf(),
                 branch: "feat/keep".into(),
-                cleanup_on_kill: false,
                 create_branch: true,
             }),
         })
@@ -398,7 +397,7 @@ async fn kill_removes_worktree_even_when_spec_says_keep() {
     init_bare_repo(origin.path());
     push_all_to_origin(repo.path(), origin.path());
 
-    fx.manager.kill(s.id).await.expect("kill");
+    fx.manager.kill(s.id, false).await.expect("kill");
     assert!(!wt_path.exists(), "worktree must be removed on kill");
 }
 
@@ -423,7 +422,6 @@ async fn killing_refuses_a_worktree_with_unsaved_work_and_keeps_the_session() {
             worktree: Some(WorktreeSpec {
                 base_repo: repo.path().to_path_buf(),
                 branch: "feat/guarded".into(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         })
@@ -432,7 +430,11 @@ async fn killing_refuses_a_worktree_with_unsaved_work_and_keeps_the_session() {
     std::fs::write(wt_path.join("README"), b"unsaved edits\n").unwrap();
     std::fs::write(wt_path.join("notes.txt"), b"untracked\n").unwrap();
 
-    let err = fx.manager.kill(s.id).await.expect_err("kill must refuse");
+    let err = fx
+        .manager
+        .kill(s.id, false)
+        .await
+        .expect_err("kill must refuse");
     let SessionError::KillGuarded(breakdown) = err else {
         panic!("expected KillGuarded, got {err:?}");
     };
@@ -456,7 +458,10 @@ async fn killing_refuses_a_worktree_with_unsaved_work_and_keeps_the_session() {
     let origin = TempDir::new().unwrap();
     init_bare_repo(origin.path());
     push_all_to_origin(repo.path(), origin.path());
-    fx.manager.kill(s.id).await.expect("kill after saving");
+    fx.manager
+        .kill(s.id, false)
+        .await
+        .expect("kill after saving");
     assert!(!fx.manager.has(s.id).await);
 }
 
@@ -480,14 +485,17 @@ async fn killing_refuses_until_the_branch_is_pushed() {
             worktree: Some(WorktreeSpec {
                 base_repo: repo.path().to_path_buf(),
                 branch: "feat/pushed".into(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         })
         .await
         .expect("create");
 
-    let err = fx.manager.kill(s.id).await.expect_err("unpushed blocks");
+    let err = fx
+        .manager
+        .kill(s.id, false)
+        .await
+        .expect_err("unpushed blocks");
     let SessionError::KillGuarded(breakdown) = err else {
         panic!("expected KillGuarded, got {err:?}");
     };
@@ -499,11 +507,116 @@ async fn killing_refuses_until_the_branch_is_pushed() {
     init_bare_repo(origin.path());
     push_all_to_origin(repo.path(), origin.path());
 
-    fx.manager.kill(s.id).await.expect("pushed branch kills");
+    fx.manager
+        .kill(s.id, false)
+        .await
+        .expect("pushed branch kills");
     assert!(!wt_path.exists());
     assert!(!fx.manager.has(s.id).await);
 }
 
+/// `--force` overrides the refusal and nothing else (#81): the session ends,
+/// but the guarded worktree is RETAINED — never removed — and enters the
+/// retained store with reason `force-killed`. The outcome names what was
+/// kept, so a client can say where the work went.
+#[tokio::test]
+async fn force_killing_a_guarded_worktree_retains_it_in_the_store() {
+    let fx = DaemonFixture::new();
+    let repo = TempDir::new().unwrap();
+    init_repo(repo.path());
+    let wt_path = repo.path().join("worktrees").join("feat").join("forced");
+
+    let s = fx
+        .manager
+        .create(CreateSessionRequest {
+            cwd: repo.path().to_path_buf(),
+            command: "sleep 30".into(),
+            env: HashMap::new(),
+            metadata: HashMap::new(),
+            worktree: Some(WorktreeSpec {
+                base_repo: repo.path().to_path_buf(),
+                branch: "feat/forced".into(),
+                create_branch: true,
+            }),
+        })
+        .await
+        .expect("create");
+    std::fs::write(wt_path.join("README"), b"unsaved edits\n").unwrap();
+
+    // Without force the same kill is refused (#79).
+    assert!(fx.manager.kill(s.id, false).await.is_err());
+
+    let outcome = fx
+        .manager
+        .kill(s.id, true)
+        .await
+        .expect("force overrides the refusal");
+
+    // The tree would have blocked, so force must NOT have removed it...
+    assert!(
+        wt_path.exists(),
+        "a forced kill never removes a tree that would have blocked"
+    );
+    // ...but the session itself still ends.
+    assert!(!fx.manager.has(s.id).await);
+    assert!(!fx.sidecar_dir().join(format!("{}.json", s.id)).exists());
+
+    let retained = outcome.retained.expect("the outcome names what was kept");
+    assert_eq!(retained.path, wt_path);
+    assert_eq!(retained.branch, "feat/forced");
+    assert_eq!(
+        retained.reason,
+        maestro_protocol::RetainedReason::ForceKilled
+    );
+    assert!(
+        retained.in_the_way.uncommitted_files >= 1,
+        "the outcome carries what blocked the unforced kill"
+    );
+
+    // The store holds the same entry, so reclaim can find it later (#80).
+    let all = fx.retained_store().load_all().expect("load_all");
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].id, retained.id);
+    assert_eq!(all[0].path, wt_path);
+    assert_eq!(all[0].branch, "feat/forced");
+}
+
+/// Force overrides the *refusal*, not ordinary cleanup (#81): a tree whose
+/// guard is clear never needed the override, so a forced kill removes it as
+/// usual and retains nothing.
+#[tokio::test]
+async fn force_on_a_clear_worktree_removes_it_as_usual() {
+    let fx = DaemonFixture::new();
+    let repo = TempDir::new().unwrap();
+    init_repo(repo.path());
+    let wt_path = repo.path().join("worktrees").join("feat").join("clear");
+
+    let s = fx
+        .manager
+        .create(CreateSessionRequest {
+            cwd: repo.path().to_path_buf(),
+            command: "sleep 30".into(),
+            env: HashMap::new(),
+            metadata: HashMap::new(),
+            worktree: Some(WorktreeSpec {
+                base_repo: repo.path().to_path_buf(),
+                branch: "feat/clear".into(),
+                create_branch: true,
+            }),
+        })
+        .await
+        .expect("create");
+
+    let origin = TempDir::new().unwrap();
+    init_bare_repo(origin.path());
+    push_all_to_origin(repo.path(), origin.path());
+
+    let outcome = fx.manager.kill(s.id, true).await.expect("kill");
+    assert!(!wt_path.exists(), "a clear tree needs no override");
+    assert_eq!(outcome.retained, None);
+    assert!(fx.retained_store().load_all().unwrap().is_empty());
+}
+
 /// Ignored files NEVER block (#79): build output like `target/` exists in
 /// every Rust checkout, and an ignored-only worktree stays killable.
 #[tokio::test]
@@ -530,7 +643,6 @@ async fn killing_an_ignored_only_worktree_succeeds() {
             worktree: Some(WorktreeSpec {
                 base_repo: repo.path().to_path_buf(),
                 branch: "feat/rusty".into(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         })
@@ -543,7 +655,7 @@ async fn killing_an_ignored_only_worktree_succeeds() {
     push_all_to_origin(repo.path(), origin.path());
 
     fx.manager
-        .kill(s.id)
+        .kill(s.id, false)
         .await
         .expect("ignored files never block");
     assert!(!wt_path.exists());
@@ -587,5 +699,5 @@ async fn liveness_watcher_leaves_running_sessions_alone() {
     tokio::time::sleep(Duration::from_millis(400)).await;
     assert!(fx.manager.has(s.id).await, "live session got reaped");
 
-    fx.manager.kill(s.id).await.unwrap();
+    fx.manager.kill(s.id, false).await.unwrap();
 }

crates/maestro-e2e/src/client.rs

@@ -61,7 +61,7 @@ impl TestClient {
     }
 
     pub async fn kill_session(&self, id: Uuid) -> Result<(), ClientError> {
-        Ok(self.daemon.kill_session(id).await?)
+        Ok(self.daemon.kill_session(id, false).await.map(|_| ())?)
     }
 
     pub async fn list_projects(&self) -> Result<Vec<Project>, ClientError> {

crates/maestro-protocol/src/client.rs

@@ -16,7 +16,7 @@ use uuid::Uuid;
 use crate::routes::{self, UrlError};
 use crate::{
     ApiError, BranchInfo, CreateSessionRequest, DaemonInfo, DirListing, ErrorInfo, GitRoot,
-    Project, RecentDirs, RetainedWorktree, Session,
+    KillOutcome, Project, RecentDirs, RetainedWorktree, Session,
 };
 
 /// Time budget for establishing a TCP connection to the daemon.
@@ -114,12 +114,24 @@ impl DaemonClient {
         self.post(routes::SESSIONS, req).await
     }
 
-    pub async fn kill_session(&self, id: Uuid) -> Result<(), ClientError> {
+    /// Kill a session. With `force`, the daemon overrides the kill refusal
+    /// (#79) and retains the worktree instead of removing it (#81); the
+    /// outcome then names what was kept and where.
+    pub async fn kill_session(&self, id: Uuid, force: bool) -> Result<KillOutcome, ClientError> {
+        let query: &[(&str, &str)] = if force {
+            &[(routes::FORCE_QUERY, "true")]
+        } else {
+            &[]
+        };
         let resp = self
-            .send(Method::DELETE, &routes::session(id), &[], None::<&()>)
+            .send(Method::DELETE, &routes::session(id), query, None::<&()>)
             .await?;
-        check(resp).await?;
-        Ok(())
+        let resp = check(resp).await?;
+        // An unforced kill keeps its historical `204 No Content`.
+        if resp.status() == reqwest::StatusCode::NO_CONTENT {
+            return Ok(KillOutcome { retained: None });
+        }
+        json(resp).await
     }
 
     pub async fn daemon_info(&self) -> Result<DaemonInfo, ClientError> {

crates/maestro-protocol/src/lib.rs

@@ -119,11 +119,6 @@ pub enum ActivityState {
 pub struct WorktreeSpec {
     pub base_repo: PathBuf,
     pub branch: String,
-    /// Kept on the wire for CLI compatibility (#56) but no longer a
-    /// user-facing choice: the daemon always cleans up on kill, guarded
-    /// against unsaved work. Defaults to `true`.
-    #[serde(default = "default_true")]
-    pub cleanup_on_kill: bool,
     /// When false, `branch` must already exist and is checked out as-is
     /// (#56); when true (the default, and what every payload meant before
     /// the field existed) the daemon creates it with `worktree add -b`.
@@ -195,6 +190,19 @@ pub struct RetainedWorktree {
     pub in_the_way: InTheWay,
 }
 
+/// Body of a successful forced `DELETE /api/sessions/:id?force=true` (#81).
+/// A forced kill ends the session and retains its worktree instead of
+/// removing it; this names what was kept, where, and why, so a client can say
+/// where the work went rather than leaving the operator to wonder.
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct KillOutcome {
+    /// Set when the worktree was retained with reason `force-killed`; `None`
+    /// when there was nothing to retain — no worktree at all, or one whose
+    /// guard was clear, which a forced kill removes as usual.
+    #[serde(default)]
+    pub retained: Option<RetainedWorktree>,
+}
+
 impl std::fmt::Display for InTheWay {
     /// "3 uncommitted files, 2 unpushed commits" — zero parts are omitted;
     /// all-zero renders "no unsaved work". This is the phrasing every client
@@ -581,7 +589,6 @@ mod tests {
             worktree: Some(WorktreeSpec {
                 base_repo: PathBuf::from("/home/naps62/projects/maestro"),
                 branch: "feat/foo".into(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         };
@@ -611,7 +618,6 @@ mod tests {
         });
         let spec: WorktreeSpec = serde_json::from_value(json).unwrap();
         assert!(spec.create_branch);
-        assert!(spec.cleanup_on_kill);
     }
 
     #[test]
@@ -619,7 +625,6 @@ mod tests {
         let spec = WorktreeSpec {
             base_repo: PathBuf::from("/work"),
             branch: "feat/foo".into(),
-            cleanup_on_kill: true,
             create_branch: false,
         };
         assert_eq!(spec, round_trip(&spec));
@@ -679,6 +684,22 @@ mod tests {
         );
     }
 
+    #[test]
+    fn kill_outcome_round_trips_a_retained_worktree() {
+        let outcome = KillOutcome {
+            retained: Some(sample_retained_worktree()),
+        };
+        assert_eq!(outcome, round_trip(&outcome));
+    }
+
+    /// A kill with nothing to retain — no worktree, or a clean one removed as
+    /// usual — decodes from an absent field.
+    #[test]
+    fn kill_outcome_defaults_to_nothing_retained() {
+        let outcome: KillOutcome = serde_json::from_value(serde_json::json!({})).unwrap();
+        assert_eq!(outcome.retained, None);
+    }
+
     #[test]
     fn catalog_event_round_trips_and_tags() {
         let session = sample_session();

crates/maestro-protocol/src/routes.rs

@@ -38,6 +38,10 @@ pub const PATH_QUERY: &str = "path";
 /// Name of the query parameter [`NAMES`] takes.
 pub const COUNT_QUERY: &str = "count";
 
+/// Name of the boolean query parameter `DELETE /api/sessions/:id` takes (#81).
+/// `force=true` overrides the kill refusal and retains the worktree.
+pub const FORCE_QUERY: &str = "force";
+
 /// `DELETE /api/sessions/:id`.
 pub fn session(id: Uuid) -> String {
     format!("{SESSIONS}/{id}")

crates/maestro-tui/src/app.rs

@@ -733,8 +733,14 @@ impl App {
     }
 
     async fn submit_kill(&mut self, sid: Uuid) {
-        match self.daemon.kill_session(sid).await {
-            Ok(()) => self.release_session(sid),
+        match self.daemon.kill_session(sid, false).await {
+            Ok(outcome) => {
+                if let Some(w) = outcome.retained {
+                    self.state
+                        .toast(format!("worktree retained: {}", w.path.display()));
+                }
+                self.release_session(sid)
+            }
             Err(e) => self.state.toast(format!("kill failed: {e}")),
         }
     }

crates/maestro-tui/src/draft.rs

@@ -549,7 +549,6 @@ impl DraftPane {
                 WorktreeSpec {
                     base_repo,
                     branch: branch.to_string(),
-                    cleanup_on_kill: true,
                     create_branch: true,
                 }
             }
@@ -562,7 +561,6 @@ impl DraftPane {
                 WorktreeSpec {
                     base_repo,
                     branch: name,
-                    cleanup_on_kill: true,
                     create_branch: false,
                 }
             }
@@ -1689,7 +1687,6 @@ mod tests {
         assert_eq!(wt.base_repo, PathBuf::from("/repos/maestro"));
         assert_eq!(wt.branch, "crimson-otter", "branch defaults to the name");
         assert!(wt.create_branch);
-        assert!(wt.cleanup_on_kill);
     }
 
     #[test]

crates/maestro-tui/src/fast_forward.rs

@@ -80,7 +80,6 @@ impl FastForwardDefaults {
                     .clone()
                     .unwrap_or_else(|| project.path.clone()),
                 branch: name.to_string(),
-                cleanup_on_kill: true,
                 create_branch: true,
             }),
         })

docs/WORKTREES.md

@@ -75,11 +75,16 @@ That is only safe because force retains.
 
 `--force` overrides the refusal and nothing else. It ends the session and
 **retains** the worktree, which enters the retained store with reason
-`force-killed`. Force never removes a tree that would have blocked.
+`force-killed`. Force never removes a tree that would have blocked. A tree
+whose guard is clear never needed the override, so a forced kill removes it as
+usual — force changes what happens to blocked work, not ordinary cleanup.
 
-Ending a session and destroying its work are two separate destructive acts. Each
-is chosen on its own, and the second one — reclaim — is chosen while looking at
-exactly what would be lost.
+Ending a session and destroying its work are two separate destructive acts.
+Each is chosen on its own, and the second one — reclaim — is chosen while
+looking at exactly what would be lost.
+
+A forced kill answers with what was retained and why, so a client can say where
+the work went rather than leaving the operator to wonder.
 
 ### Exiting on its own
 

web/src/fastForward.test.ts

@@ -43,7 +43,6 @@ describe("resolveFastForward (#67)", () => {
     expect(req.worktree).toEqual({
       base_repo: "/repos/fresh",
       branch: "amber-falcon",
-      cleanup_on_kill: true,
       create_branch: true,
     });
   });

web/src/fastForward.ts

@@ -42,7 +42,6 @@ export function buildFastForwardRequest(
     worktree: {
       base_repo: project.base_repo ?? project.path,
       branch: name,
-      cleanup_on_kill: true,
       create_branch: true,
     },
   };

web/src/spawnForm.test.ts

@@ -38,7 +38,6 @@ describe("buildSpawnRequest", () => {
         worktree: {
           base_repo: "/home/user/project",
           branch: "feat/foo",
-          cleanup_on_kill: true,
           create_branch: true,
         },
       },
@@ -63,7 +62,6 @@ describe("buildSpawnRequest", () => {
         worktree: {
           base_repo: "/home/user/project",
           branch: "spawn-v2",
-          cleanup_on_kill: true,
           create_branch: false,
         },
       },

web/src/spawnForm.ts

@@ -75,9 +75,6 @@ export function buildSpawnRequest(
     req.worktree = {
       base_repo: baseRepo,
       branch,
-      // The daemon always cleans up, guarded against unsaved work (#56);
-      // the wire field stays for older daemons.
-      cleanup_on_kill: true,
       // Existing-mode picks must check out as-is; the daemon creates
       // anything else with `worktree add -b` (#56/#61).
       create_branch: mode !== "existing",

web/src/types.ts

@@ -113,7 +113,6 @@ export type Projects = Project[];
 export interface WorktreeSpec {
   base_repo: string;
   branch: string;
-  cleanup_on_kill?: boolean;
   /** When false, `branch` already exists and is checked out as-is (#61).
    * Defaults to true (create a new branch) on older daemons. */
   create_branch?: boolean;