1 files changed, 97 insertions, 1 deletions

diff --git a/src/features/chat/reasoning-effort.ts b/src/features/chat/reasoning-effort.ts
index 1eb77b6..39e1c5a 100644
--- a/src/features/chat/reasoning-effort.ts
+++ b/src/features/chat/reasoning-effort.ts
@@ -36,7 +36,7 @@ export function effectiveEffort(persisted: ReasoningEffort | null): ReasoningEff
   return persisted ?? DEFAULT_REASONING_EFFORT;
 }
 
-/** One `<option>` of the selector. */
+/** One `<option>` of the effort ladder. */
 export interface EffortOption {
   readonly value: ReasoningEffort;
   readonly label: string;
@@ -64,3 +64,99 @@ export type ReasoningEffortSaveResult =
 export type SaveReasoningEffort = (
   level: ReasoningEffort,
 ) => Promise<ReasoningEffortSaveResult | null>;
+
+// ── Thinking on/off (a SEPARATE axis from the effort level) ─────────────────
+//
+// Per the umans API (and the user's mental model), "thinking off" is NOT a
+// zero-effort level — it is a distinct "disable extended thinking entirely"
+// signal. The umans route expresses it as `reasoning_effort: "none"`; Dispatch
+// surfaces it as a SEPARATE per-conversation boolean so the effort LEVEL is
+// preserved across an off→on toggle (turning thinking back on restores the
+// previously-chosen depth). The per-conversation selector CONFLATES the two
+// axes into one `<select>` (UX), but the WIRE keeps them separate.
+//
+// ⚠️ BACKEND CONTRACT GAP — see `backend-handoff.md`. The `thinking` endpoint +
+// wire types below are the PROPOSED shape; the backend has NOT shipped them yet.
+// They are defined FE-local (mirroring the shipped `ReasoningEffortResponse` /
+// `SetReasoningEffortRequest` shape) so the FE is built + tested against the
+// target contract. Re-pin + re-mirror once the backend ships them.
+
+/**
+ * Response of `GET /conversations/:id/thinking` (PROPOSED). `thinking` is null
+ * when never set (the server then resolves turns with thinking ON — the
+ * default), `false` when explicitly disabled, `true` when explicitly enabled.
+ */
+export interface ThinkingResponse {
+  readonly conversationId: string;
+  readonly thinking: boolean | null;
+}
+
+/** Body of `PUT /conversations/:id/thinking` (PROPOSED). */
+export interface SetThinkingRequest {
+  readonly thinking: boolean;
+}
+
+/**
+ * The per-conversation selector's value: `"off"` (thinking disabled — the
+ * separate axis) or a reasoning-effort LEVEL. NOT a widened ladder: `"off"` is
+ * not a degree of effort, it is the absence of thinking.
+ */
+export type ThinkingSelection = "off" | ReasoningEffort;
+
+/** One `<option>` of the combined selector (off or a level). */
+export interface SelectionOption {
+  readonly value: ThinkingSelection;
+  readonly label: string;
+}
+
+/**
+ * The selector's options: `"off"` first (the separate disable signal), then the
+ * effort ladder with the server default marked `(default)`. A never-set
+ * conversation (thinking on, effort null) reads "high (default)".
+ */
+export function selectionOptions(): readonly SelectionOption[] {
+  return [{ value: "off", label: "Off" }, ...effortOptions()];
+}
+
+/** Narrow an untrusted `<select>` value to a {@link ThinkingSelection}. */
+export function isThinkingSelection(value: string): value is ThinkingSelection {
+  return value === "off" || isReasoningEffort(value);
+}
+
+/**
+ * The selection the per-conversation selector should show as selected: `"off"`
+ * when thinking is explicitly disabled (`persistedThinking === false`), else the
+ * effective effort level. `persistedThinking === null` (never set) ⇒ thinking
+ * ON (the default) ⇒ the effort level is shown — NOT "off".
+ */
+export function effectiveSelection(
+  persistedEffort: ReasoningEffort | null,
+  persistedThinking: boolean | null,
+): ThinkingSelection {
+  if (persistedThinking === false) return "off";
+  return effectiveEffort(persistedEffort);
+}
+
+// ── Injected port for the combined selector (off OR a level) ─────────────────
+
+/** Outcome of persisting a {@link ThinkingSelection} (one or two PUTs). */
+export type ThinkingSelectionSaveResult =
+  | { readonly ok: true; readonly selection: ThinkingSelection }
+  | { readonly ok: false; readonly error: string };
+
+/**
+ * Persist a thinking selection (consumer-defines-port; the composition root
+ * adapts the store's `PUT .../thinking` + `PUT .../reasoning-effort` to this).
+ * - `"off"` → disable thinking (the separate signal); the effort level is left
+ *   untouched so an off→on toggle restores it.
+ * - a level → set the effort level AND ensure thinking is ON (the level is
+ *   meaningless while thinking is off).
+ */
+export type SaveThinkingSelection = (
+  selection: ThinkingSelection,
+) => Promise<ThinkingSelectionSaveResult | null>;
+
+/** Outcome of `PUT /conversations/:id/thinking`. */
+export type ThinkingSaveResult =
+  | { readonly ok: true; readonly thinking: boolean }
+  | { readonly ok: false; readonly error: string };