own /effort: respawn-with-resume carrying --effort, picker UX (T-412)

Spike result (probed claude 2.1.175 over stream-json): there is NO
set_effort/set_thinking_effort control subtype — both are rejected. The
lever is the `--effort <level>` spawn flag (low/medium/high/xhigh/max;
settings.json effortLevel is the persisted default). So changing effort
restarts the process: respawn-with-resume keeps the conversation and
carries the flag — the same continuity /clear and /resume already rely on.

- SpawnSpec.effort → orchestrator appends `--effort <level>`.
- claude_pane: /effort <level> validates and respawns (toast explains the
  restart); bare /effort opens a picker; the pane re-applies its effort on
  every later respawn. Invalid level → local notice listing levels.
- ModelPickerCard generalised minimally (title + isCurrent predicate) so
  the effort picker reuses it; effort needs exact matching because `high`
  is a substring of `xhigh` and alias-containment would mis-mark it.
- SessionStatus.effort + StreamJsonSession.noteEffort: the wire never
  reports effort, so the spawner records what it set; status/sidebar read
  it from the normal status stream.
- Routing: effort moves from the TUI-only catalog to kClideOwnedCommands.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/builtin/claude/src/claude_pane.dart

@@ -91,6 +91,11 @@ class _ClaudePaneState extends State<ClaudePane> {
   /// (T-408). An open prompt takes precedence; the picker shows once it
   /// resolves.
   bool _modelPickerOpen = false;
+  bool _effortPickerOpen = false;
+
+  /// Effort level this pane's session runs at (`--effort`, T-412). Null =
+  /// the CLI default. Set by /effort; carried by every respawn.
+  String? _effort;
 
   bool _spawned = false;
 
@@ -249,6 +254,7 @@ class _ClaudePaneState extends State<ClaudePane> {
     _modelErrorSub?.cancel();
     _modelErrorSub = null;
     _modelPickerOpen = false;
+    _effortPickerOpen = false;
     await activeSessionOrchestrator?.close(_orchId); // kills the old repo's session
     _conversation = null;
     _session = null;
@@ -296,7 +302,14 @@ class _ClaudePaneState extends State<ClaudePane> {
       _sessionId ??= freshSessionId();
       try {
         managed = await orch.spawn(
-          SpawnSpec(id: _orchId, role: 'fork ${widget.secondaryIndex}', sessionId: _sessionId!, cwd: repoRoot, forkSourceSessionId: forkSource),
+          SpawnSpec(
+            id: _orchId,
+            role: 'fork ${widget.secondaryIndex}',
+            sessionId: _sessionId!,
+            cwd: repoRoot,
+            forkSourceSessionId: forkSource,
+            effort: _effort,
+          ),
         );
       } catch (e) {
         if (mounted) setState(() => _error = 'Could not start fork: $e');
@@ -327,6 +340,7 @@ class _ClaudePaneState extends State<ClaudePane> {
             cwd: repoRoot,
             resume: resume,
             transcriptPath: resume ? transcriptFile : null,
+            effort: _effort,
           ),
         );
       } catch (e) {
@@ -339,6 +353,9 @@ class _ClaudePaneState extends State<ClaudePane> {
 
     _session = managed.session;
     _conversation = managed.conversation;
+    // The wire never reports effort — record what this session was spawned
+    // with so the status line / sidebar can show it (T-412).
+    if (_effort != null) managed.session.noteEffort(_effort!);
     // Diagnostic (T-274 follow-up): record how this pane bound its session —
     // a fresh spawn vs connecting to existing on-disk history (the seed read
     // from the transcript/sidecar). Surfaces the resume path in `make run`.
@@ -397,6 +414,9 @@ class _ClaudePaneState extends State<ClaudePane> {
       case 'model':
         _modelCommand(slashCommandArg(text) ?? '');
         return;
+      case 'effort':
+        _effortCommand(slashCommandArg(text) ?? '');
+        return;
     }
     // Route the rest (T-411): a known TUI-only builtin never reaches the
     // session — forwarded it would error (or, un-advertised, bracket-paste to
@@ -431,6 +451,41 @@ class _ClaudePaneState extends State<ClaudePane> {
     _composerFocus.requestFocus();
   }
 
+  /// clide-owned `/effort` (T-412): with a level, respawn-with-resume carrying
+  /// `--effort`; bare, open the picker. No set_effort control subtype exists
+  /// (probed 2.1.175), so the respawn IS the mechanism — resume keeps the
+  /// conversation, only the process restarts.
+  void _effortCommand(String arg) {
+    if (_session == null) return;
+    if (arg.isEmpty) {
+      setState(() => _effortPickerOpen = true);
+      return;
+    }
+    if (!kEffortLevels.any((l) => l.value == arg)) {
+      _session!.addLocalNotice('unknown effort "$arg" — levels: ${kEffortLevels.map((l) => l.value).join(', ')}');
+      return;
+    }
+    _setEffort(arg);
+  }
+
+  void _pickEffort(String value) {
+    _closeEffortPicker();
+    _setEffort(value);
+  }
+
+  void _closeEffortPicker() {
+    setState(() => _effortPickerOpen = false);
+    _composerFocus.requestFocus();
+  }
+
+  void _setEffort(String level) {
+    final sid = _sessionId;
+    if (sid == null) return;
+    _effort = level;
+    _kernel?.notify.info('effort $level — restarting the session to apply', title: 'effort');
+    unawaited(_respawnWithSession(sid));
+  }
+
   /// Record a submitted prompt in the active session's history (T-163),
   /// de-duping immediate repeats. Empty/whitespace prompts are skipped.
   void _appendHistory(String text) {
@@ -455,7 +510,7 @@ class _ClaudePaneState extends State<ClaudePane> {
   /// background tap must never pull focus from (or resurrect) the composer
   /// over an open prompt.
   void _focusComposerOnTap() {
-    if (_session?.pendingPrompt != null || _modelPickerOpen) return;
+    if (_session?.pendingPrompt != null || _modelPickerOpen || _effortPickerOpen) return;
     _composerFocus.requestFocus();
   }
 
@@ -530,6 +585,7 @@ class _ClaudePaneState extends State<ClaudePane> {
     _modelErrorSub?.cancel();
     _modelErrorSub = null;
     _modelPickerOpen = false;
+    _effortPickerOpen = false;
     await activeSessionOrchestrator?.close(_orchId); // kills the old session
     // Erase only after the process is dead, so claude isn't mid-write.
     final root = _repoRoot;
@@ -612,6 +668,16 @@ class _ClaudePaneState extends State<ClaudePane> {
                   onPick: _pickModel,
                   onCancel: _closeModelPicker,
                 )
+              else if (_effortPickerOpen && _session != null)
+                ModelPickerCard(
+                  title: 'effort',
+                  models: kEffortLevels,
+                  currentModel: _status.effort,
+                  // Exact match — containment would mark `high` inside `xhigh`.
+                  isCurrent: (o, c) => c != null && o.value == c,
+                  onPick: _pickEffort,
+                  onCancel: _closeEffortPicker,
+                )
               else
                 StreamBuilder<bool>(
                   stream: _session?.busyStream,

lib/builtin/claude/src/model_picker_card.dart

@@ -25,7 +25,15 @@ bool modelOptionIsCurrent(ModelOption option, String? currentModel) {
 }
 
 class ModelPickerCard extends StatefulWidget {
-  const ModelPickerCard({super.key, required this.models, this.currentModel, required this.onPick, required this.onCancel});
+  const ModelPickerCard({
+    super.key,
+    required this.models,
+    this.currentModel,
+    required this.onPick,
+    required this.onCancel,
+    this.title = 'model',
+    this.isCurrent = modelOptionIsCurrent,
+  });
 
   /// Selectable entries, in display order. Callers pass [kFallbackModels]
   /// when the session hasn't reported its list yet.
@@ -40,6 +48,15 @@ class ModelPickerCard extends StatefulWidget {
   /// Called when the user dismisses the picker without choosing.
   final VoidCallback onCancel;
 
+  /// Header label. The /effort picker reuses this card with its own title
+  /// and an exact-match [isCurrent] (T-412).
+  final String title;
+
+  /// Marks the active entry. The model default ([modelOptionIsCurrent]) also
+  /// alias-matches (`sonnet` ⊂ `claude-sonnet-4-6`); effort needs exact match
+  /// (`high` would falsely match inside `xhigh`).
+  final bool Function(ModelOption option, String? current) isCurrent;
+
   @override
   State<ModelPickerCard> createState() => _ModelPickerCardState();
 }
@@ -49,7 +66,7 @@ class _ModelPickerCardState extends State<ModelPickerCard> {
 
   int _initialHighlight() {
     for (var i = 0; i < widget.models.length; i++) {
-      if (modelOptionIsCurrent(widget.models[i], widget.currentModel)) return i;
+      if (widget.isCurrent(widget.models[i], widget.currentModel)) return i;
     }
     return 0;
   }
@@ -130,7 +147,7 @@ class _ModelPickerCardState extends State<ModelPickerCard> {
           children: [
             Row(
               children: [
-                ClideText('model', fontSize: clideFontSmall, fontFamily: clideMonoFamily, color: tokens.statusInfo),
+                ClideText(widget.title, fontSize: clideFontSmall, fontFamily: clideMonoFamily, color: tokens.statusInfo),
                 const Spacer(),
                 ClideText('↑↓ · 1-${widget.models.length} · Enter · Esc', fontSize: clideFontMeta, fontFamily: clideMonoFamily, color: tokens.globalTextMuted),
               ],
@@ -152,7 +169,7 @@ class _ModelPickerCardState extends State<ModelPickerCard> {
 
   Widget _row(SurfaceTokens tokens, int i) {
     final m = widget.models[i];
-    final current = modelOptionIsCurrent(m, widget.currentModel);
+    final current = widget.isCurrent(m, widget.currentModel);
     final highlighted = i == _highlight;
     return Padding(
       padding: const EdgeInsets.only(bottom: 4),

lib/builtin/claude/src/session_orchestrator.dart

@@ -49,6 +49,7 @@ class SpawnSpec {
     this.team = false,
     this.memberName,
     this.forkSourceSessionId,
+    this.effort,
   });
 
   final String id;
@@ -81,6 +82,12 @@ class SpawnSpec {
   /// Takes precedence over [resume]/[sessionId] for arg selection.
   final String? forkSourceSessionId;
 
+  /// Effort level passed to `claude --effort` (low/medium/high/xhigh/max,
+  /// T-412). Null spawns without the flag — the CLI uses its configured
+  /// default (settings.json `effortLevel`). No set_effort control subtype
+  /// exists, so changing effort means respawn-with-resume carrying this.
+  final String? effort;
+
   /// Whether this spec spawns a forked session.
   bool get isFork => forkSourceSessionId != null;
 }
@@ -238,7 +245,13 @@ class ClaudeSessionOrchestrator extends ChangeNotifier {
       preambles.add(_teamSystemPrompt(name, spec.role));
     }
     final bootstrap = agentBootstrap(spec.cwd, base: spec.env);
-    sessionArgs = ['--append-system-prompt', preambles.join('\n\n'), ...bootstrap.extraArgs, ...sessionArgs];
+    sessionArgs = [
+      '--append-system-prompt',
+      preambles.join('\n\n'),
+      ...bootstrap.extraArgs,
+      if (spec.effort != null) ...['--effort', spec.effort!],
+      ...sessionArgs,
+    ];
 
     final proc = await _factory(sessionArgs: sessionArgs, cwd: spec.cwd, env: bootstrap.envDelta);
     final session = StreamJsonSession(proc, mcpServers: mcpServers)..start();

lib/builtin/claude/src/slash_commands.dart

@@ -32,8 +32,10 @@ bool isKnownSlashCommand(String text, Iterable<String> known) {
 /// transcript reader can't follow, so clide owns the semantics (T-156).
 /// `/fork` branches the current session into a new pane (T-172). `/model`
 /// is interactive in the CLI's TUI only — forwarded it does nothing — so
-/// clide owns it as a set_model control request / picker (T-408).
-const Set<String> kClideOwnedCommands = {'clear', 'resume', 'fork', 'model'};
+/// clide owns it as a set_model control request / picker (T-408). `/effort`
+/// has no control subtype, so clide owns it as a respawn-with-resume
+/// carrying `--effort` (T-412).
+const Set<String> kClideOwnedCommands = {'clear', 'resume', 'fork', 'model', 'effort'};
 
 /// The clide-owned command in [text] (a single-line leading-slash token in
 /// [kClideOwnedCommands]), or null.
@@ -64,7 +66,7 @@ enum SlashRoute {
 /// model as literal text). Value = the clide-native pointer shown in the
 /// notice card. Commands clide later implements move to [kClideOwnedCommands].
 const Map<String, String> kTuiOnlyCommands = {
-  'effort': 'the session effort level is set at spawn time; clide support is tracked in T-412',
+  'effort': '', // owned (T-412) — only routes here if ever removed from owned
   'status': 'session status lives in the Claude sidebar (Activity tab)',
   'cost': 'cost and context usage live in the Claude sidebar (Activity tab)',
   'context': '', // advertised on current CLIs — only routes here on older ones

lib/builtin/claude/src/stream_json_session.dart

@@ -162,6 +162,18 @@ class ModelOption {
   final String description;
 }
 
+/// Effort levels `claude --effort` accepts (probed against 2.1.175). There is
+/// NO set_effort control subtype (probed: rejected), so changing effort
+/// respawns the session with the flag — resume keeps the conversation (T-412).
+/// Expressed as [ModelOption]s so the /effort picker reuses the /model card.
+const List<ModelOption> kEffortLevels = [
+  ModelOption(value: 'low', displayName: 'low', description: 'fastest, minimal thinking'),
+  ModelOption(value: 'medium', displayName: 'medium', description: 'balanced'),
+  ModelOption(value: 'high', displayName: 'high', description: 'thorough'),
+  ModelOption(value: 'xhigh', displayName: 'xhigh', description: 'deeper reasoning'),
+  ModelOption(value: 'max', displayName: 'max', description: 'maximum thinking budget'),
+];
+
 /// Fallback picker entries for when the `initialize` response hasn't arrived
 /// (or carried no models): the stable aliases every claude build accepts
 /// (T-408). `default` resets to the CLI's configured model.
@@ -801,6 +813,11 @@ class StreamJsonSession {
     _items.add(AssistantTextMessage(uuid: 'local-${_localSeq++}', timestamp: DateTime.now(), isSidechain: false, text: text, synthetic: true));
   }
 
+  /// Record the effort level this session was spawned with (`--effort`,
+  /// T-412). The wire never reports effort, so the spawner tells the status
+  /// what it set; the status line / sidebar read it from [SessionStatus].
+  void noteEffort(String level) => _mergeStatus(SessionStatus(effort: level));
+
   /// Interrupt the running turn (the escape hatch for a runaway — D-78). Sends
   /// the `interrupt` control_request; claude cancels the current turn and ends
   /// it with a `result`, which clears [busy]. Safe to call when idle.

lib/builtin/claude/src/transcript_reader.dart

@@ -433,7 +433,7 @@ class TranscriptReader {
 /// (T-145, T-168). All fields nullable — a chunk only carries what it saw,
 /// and the reader [merge]s deltas into a running status.
 class SessionStatus {
-  const SessionStatus({this.model, this.permissionMode, this.contextTokens, this.cost, this.contextWindow, this.rateLimitInfo});
+  const SessionStatus({this.model, this.permissionMode, this.contextTokens, this.cost, this.contextWindow, this.rateLimitInfo, this.effort});
 
   /// Assistant `message.model`, e.g. `claude-opus-4-7`.
   final String? model;
@@ -458,7 +458,13 @@ class SessionStatus {
   /// `"rate limited — resets 14:32"` (T-168). Null when not rate-limited.
   final String? rateLimitInfo;
 
-  bool get isEmpty => model == null && permissionMode == null && contextTokens == null && cost == null && contextWindow == null && rateLimitInfo == null;
+  /// The session's effort level (`--effort`, T-412). The wire never reports
+  /// it — clide records what it spawned with via [StreamJsonSession.noteEffort];
+  /// null means the CLI default (settings.json `effortLevel`).
+  final String? effort;
+
+  bool get isEmpty =>
+      model == null && permissionMode == null && contextTokens == null && cost == null && contextWindow == null && rateLimitInfo == null && effort == null;
 
   /// Overlay [other]'s non-null fields onto this one.
   SessionStatus merge(SessionStatus other) => SessionStatus(
@@ -468,6 +474,7 @@ class SessionStatus {
     cost: other.cost ?? cost,
     contextWindow: other.contextWindow ?? contextWindow,
     rateLimitInfo: other.rateLimitInfo ?? rateLimitInfo,
+    effort: other.effort ?? effort,
   );
 
   @override
@@ -478,10 +485,11 @@ class SessionStatus {
       other.contextTokens == contextTokens &&
       other.cost == cost &&
       other.contextWindow == contextWindow &&
-      other.rateLimitInfo == rateLimitInfo;
+      other.rateLimitInfo == rateLimitInfo &&
+      other.effort == effort;
 
   @override
-  int get hashCode => Object.hash(model, permissionMode, contextTokens, cost, contextWindow, rateLimitInfo);
+  int get hashCode => Object.hash(model, permissionMode, contextTokens, cost, contextWindow, rateLimitInfo, effort);
 }
 
 /// Result of [parseTranscriptChunk]: items, version-drift warnings, and