fix(tui): start the session a sessionless model switch defers into

Launching kigi in a non-project directory (~/Downloads, ~, /tmp — anywhere
`is_project_dir` rejects) leaves the agent view session-less behind the
project-picker question, which only a PLAIN prompt can open. Slash
commands still execute there, so `/model <name> <effort>` stashed its
switch in `deferred_model_switch` — a stash that assumes a create is in
flight — and with none pending it dangled forever with zero feedback:
the picker rendered, the user chose model and effort, and nothing
changed. Not a 0.1.10 regression: 0.1.9 pty-reproduces identically; the
report correlated with the upgrade only because every earlier launch
happened to be from a project directory.

Apply the QueueCommand precedent ("queued slash work bypasses the
picker, so create the deferred session or it never drains") to both
deferral sites — Action::SwitchModel in the router and
set_default_model's no-session branch — via
skip_picker_and_create_session, whose in-flight guard already makes it a
no-op while a create is pending, so the racing-create case is unchanged.
SessionCreated then applies the stash through the existing
apply_deferred_model_switch path; pty-verified end-to-end from
~/Downloads (session created, model changed, effort applied).

crates/codegen/kigi-tui/src/app/dispatch/router.rs

@@ -62,6 +62,7 @@ use super::session::lifecycle::{
     clear_startup_actions, dispatch_agent_type_mismatch_answered, dispatch_exit_session,
     dispatch_new_session, dispatch_new_session_inner, dispatch_new_session_with_id,
     dispatch_new_worktree_session, dispatch_trust_folder, open_new_session_question,
+    skip_picker_and_create_session,
 };
 use super::session::load::{
     dispatch_cycle_session_source_filter, dispatch_load_session, dispatch_pick_content_session,
@@ -749,7 +750,12 @@ pub(crate) fn dispatch(action: Action, app: &mut AppView) -> Vec<Effect> {
             };
             let Some(session_id) = agent.session.session_id.clone() else {
                 agent.session.deferred_model_switch = Some((model_id, effort));
-                return vec![];
+                // No session bound: with a create in flight this is a no-op
+                // and `SessionCreated` applies the stash; with none in flight
+                // (project question pending — only a plain prompt opens it) a
+                // switch would dangle forever, so start the session like the
+                // QueueCommand arm does for queued slash work.
+                return skip_picker_and_create_session(app, id);
             };
             agent.session.model_switch_pending = true;
             vec![Effect::SwitchModel {

crates/codegen/kigi-tui/src/app/dispatch/settings/setters.rs

@@ -1519,12 +1519,20 @@ pub(in crate::app::dispatch) fn set_default_model(
             effort: None,
             prev_model_id: prev_id.clone(),
         });
-    } else if let Some(agent) = app.agents.get_mut(&aid) {
-        // No session id yet — stash for
-        // `EventLoop::on_session_created` to apply once the session
-        // id materialises. Mirrors the deferred-switch handling in
-        // `Action::SwitchModel`.
-        agent.session.deferred_model_switch = Some((new_id, None));
+    } else {
+        if let Some(agent) = app.agents.get_mut(&aid) {
+            // No session id yet — stash for
+            // `EventLoop::on_session_created` to apply once the session
+            // id materialises. Mirrors the deferred-switch handling in
+            // `Action::SwitchModel`.
+            agent.session.deferred_model_switch = Some((new_id, None));
+        }
+        // With no create in flight (project question pending), the stash
+        // would dangle forever — start the session it drains into. No-op
+        // when a create is already pending.
+        effects.extend(
+            crate::app::dispatch::session::lifecycle::skip_picker_and_create_session(app, aid),
+        );
     }
     effects
 }

crates/codegen/kigi-tui/src/app/dispatch/tests/session/lifecycle.rs

@@ -481,7 +481,7 @@ fn session_failed_clears_flag_no_fetches() {
     assert!(!app.agents[&id].pending_extensions_fetch);
 }
 #[test]
-fn switch_model_without_session_does_nothing() {
+fn switch_model_without_session_starts_the_session() {
     let mut app = test_app_with_agent();
     let id = AgentId(0);
     app.agents.get_mut(&id).unwrap().session.session_id = None;
@@ -493,7 +493,14 @@ fn switch_model_without_session_does_nothing() {
         },
         &mut app,
     );
-    assert!(effects.is_empty());
+    // No create was in flight, so the switch starts the session its stash
+    // drains into (the stash alone dangled forever — the /model-in-Downloads
+    // silent no-op). `model_switch_pending` flips on SessionCreated.
+    assert!(
+        effects
+            .iter()
+            .any(|e| matches!(e, Effect::CreateSession { .. }))
+    );
     assert!(!app.agents[&id].session.model_switch_pending);
 }
 #[test]
@@ -668,11 +675,17 @@ fn switch_model_deferred_when_no_session_id() {
         },
         &mut app,
     );
-    assert!(effects.is_empty());
+    // Stashed for SessionCreated — and the session it drains into is started
+    // (no create was in flight; a bare stash never drained).
     assert_eq!(
         app.agents[&id].session.deferred_model_switch,
         Some((model_id, None))
     );
+    assert!(
+        effects
+            .iter()
+            .any(|e| matches!(e, Effect::CreateSession { .. }))
+    );
     assert!(!app.agents[&id].session.model_switch_pending);
 }
 #[test]

crates/codegen/kigi-tui/src/app/dispatch/tests/task_result.rs

@@ -977,6 +977,77 @@ fn switch_model_pending_lifecycle() {
     assert!(!app.agents[&id].session.model_switch_pending);
 }
 
+/// A model switch with no session AND no create in flight (the project-picker
+/// question is pending; only a plain prompt can open it) must start the
+/// deferred session itself, or the stashed switch dangles forever with zero
+/// feedback — `/model X eff` in `~/Downloads` looked like "the model never
+/// changes". Mirrors the `QueueCommand` arm: queued slash work bypasses the
+/// picker and creates the session so the stash drains.
+#[test]
+fn switch_model_without_session_creates_the_deferred_session() {
+    let mut app = test_app_with_agent();
+    let id = AgentId(0);
+    app.agents.get_mut(&id).unwrap().session.session_id = None;
+    // Harness cwd is `/tmp` (a non-project dir); arm the picker gate the way
+    // startup leaves it (the harness pre-marks it shown for other tests).
+    app.project_picker_shown = false;
+    assert!(app.needs_project_picker());
+
+    let model_id = acp::ModelId::new(std::sync::Arc::from("kigi-4.5"));
+    let effects = dispatch(
+        Action::SwitchModel {
+            model_id: model_id.clone(),
+            effort: None,
+        },
+        &mut app,
+    );
+
+    assert_eq!(
+        app.agents[&id].session.deferred_model_switch,
+        Some((model_id, None)),
+        "switch must stay stashed for SessionCreated to apply"
+    );
+    assert!(
+        effects
+            .iter()
+            .any(|e| matches!(e, Effect::CreateSession { .. })),
+        "sessionless switch must start the session the stash drains into"
+    );
+}
+
+/// Same stash path while a create IS in flight (`mcp_init_progress` set):
+/// no duplicate `CreateSession` — the pending create applies the stash.
+#[test]
+fn switch_model_with_create_in_flight_does_not_duplicate_create() {
+    let mut app = test_app_with_agent();
+    let id = AgentId(0);
+    {
+        let agent = app.agents.get_mut(&id).unwrap();
+        agent.session.session_id = None;
+        agent.mcp_init_progress = Some(crate::app::agent_view::McpInitProgress {
+            total: 0,
+            connected: 0,
+            started_at: std::time::Instant::now(),
+        });
+    }
+
+    let effects = dispatch(
+        Action::SwitchModel {
+            model_id: acp::ModelId::new(std::sync::Arc::from("kigi-4.5")),
+            effort: None,
+        },
+        &mut app,
+    );
+
+    assert!(app.agents[&id].session.deferred_model_switch.is_some());
+    assert!(
+        !effects
+            .iter()
+            .any(|e| matches!(e, Effect::CreateSession { .. })),
+        "an in-flight create must not be duplicated"
+    );
+}
+
 #[test]
 fn no_deferred_switch_means_no_extra_effect() {
     // When there is no deferred model switch, SessionCreated should