2 files changed, 73 insertions, 0 deletions

diff --git a/src/core/chunks/reducer.test.ts b/src/core/chunks/reducer.test.ts
index 35a586c..a346545 100644
--- a/src/core/chunks/reducer.test.ts
+++ b/src/core/chunks/reducer.test.ts
@@ -7,6 +7,7 @@ import type {
 	TurnReasoningDeltaEvent,
 	TurnSealedEvent,
 	TurnStartEvent,
+	TurnSteeringEvent,
 	TurnTextDeltaEvent,
 	TurnToolCallEvent,
 	TurnToolResultEvent,
@@ -437,6 +438,59 @@ describe("foldEvent — user-message (the turn's user prompt; backend CR-3)", ()
 	});
 });
 
+describe("foldEvent — steering (mid-turn steering injection)", () => {
+	const steering = (text: string): TurnSteeringEvent => ({
+		type: "steering",
+		conversationId: "c1",
+		turnId: "t1",
+		text,
+	});
+
+	it("appends a provisional user bubble + keeps generating", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, toolResult("t1", "tc1", "read", "output"));
+		s = foldEvent(s, steering("actually, use a different file"));
+		const chunks = selectChunks(s);
+		const last = chunks[chunks.length - 1];
+		expect(last?.role).toBe("user");
+		expect(last?.chunk).toEqual({ type: "text", text: "actually, use a different file" });
+		expect(last?.provisional).toBe(true);
+		expect(s.generating).toBe(true);
+	});
+
+	it("does NOT dedup against the sender's queue (unlike user-message)", () => {
+		// The sender enqueued the message via `chat.queue` — the queue SURFACE
+		// showed it. The `steering` event places it in the transcript; the surface
+		// separately clears on drain. No de-dup here (the transcript never showed
+		// the queued message).
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, steering("steer once"));
+		s = foldEvent(s, steering("steer again"));
+		const users = selectChunks(s).filter((c) => c.role === "user");
+		expect(users).toHaveLength(2);
+	});
+
+	it("ignores an empty steering event", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, steering(""));
+		expect(selectChunks(s)).toHaveLength(0);
+		expect(s.generating).toBe(true); // turn-start already set it
+	});
+
+	it("flushes an accumulating chunk before appending the steering bubble", () => {
+		let s = initialState();
+		s = foldEvent(s, turnStart("t1"));
+		s = foldEvent(s, textDelta("t1", "partial response"));
+		s = foldEvent(s, steering("mid-turn correction"));
+		expect(s.accumulating).toBeNull();
+		const roles = selectChunks(s).map((c) => c.role);
+		expect(roles).toEqual(["assistant", "user"]);
+	});
+});
+
 describe("applyHistory", () => {
 	it("orders committed chunks by seq", () => {
 		const s = initialState();
diff --git a/src/core/chunks/reducer.ts b/src/core/chunks/reducer.ts
index 0a57839..035846c 100644
--- a/src/core/chunks/reducer.ts
+++ b/src/core/chunks/reducer.ts
@@ -83,6 +83,8 @@ export function applyHistory(
  * - `reasoning-delta` extends the current accumulating ThinkingChunk (or starts one).
  * - `tool-call` / `tool-result` / `error` finalize any accumulating chunk and
  *   add a new provisional chunk.
+ * - `steering` appends a user bubble mid-turn (drained from the message queue
+ *   at a tool-result boundary; the queue surface separately clears on drain).
  * - `usage` stores the latest Usage.
  * - `done` finalizes any accumulating chunk (turn still provisional).
  * - `turn-sealed` finalizes any accumulating chunk and sets sealedTurnId.
@@ -239,6 +241,23 @@ export function foldEvent(state: TranscriptState, event: AgentEvent): Transcript
 				generating: false,
 			};
 		}
+
+		case "steering": {
+			// A steering message drained from the queue at a tool-result boundary
+			// (the model sees it alongside the tool results). Append a user bubble
+			// to the provisional transcript; the turn is still in flight. The queue
+			// surface clears separately on drain (a different channel) — no de-dup
+			// here (unlike `user-message`, steering is never optimistically echoed
+			// into the transcript by the sender).
+			if (event.text.length === 0) return state;
+			const provisional = flushAccumulating(state.provisional, state.accumulating);
+			return {
+				...state,
+				provisional: [...provisional, { role: "user", chunk: { type: "text", text: event.text } }],
+				accumulating: null,
+				generating: true,
+			};
+		}
 	}
 }