From 12d0363b7598e4bc70976991bda7fff8670e9ada Mon Sep 17 00:00:00 2001
From: robomp-bot <robomp-bot@example.invalid>
Date: Wed, 29 Jul 2026 17:33:52 +0900
Subject: [PATCH] fix(collab-web): make host state authoritative for guest
 liveness

---
 packages/collab-web/CHANGELOG.md              |  4 +++
 .../src/components/shell/Composer.tsx         |  2 +-
 packages/collab-web/src/lib/client.ts         | 10 ++++++-
 packages/collab-web/test/client.test.ts       | 28 +++++++++++++++++++
 4 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/packages/collab-web/CHANGELOG.md b/packages/collab-web/CHANGELOG.md
index cf07b4023..35bbe08f4 100644
--- a/packages/collab-web/CHANGELOG.md
+++ b/packages/collab-web/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed the guest rendering idle while the host agent is running (spinner vanishing mid-turn after a reconnect dropped `agent_start`): host `state` frames are now authoritative for liveness in both directions, and an idle report clears tool cards pinned by a dropped `tool_execution_end`.
+
 ## [17.1.0] - 2026-07-24
 
 ### Fixed
diff --git a/packages/collab-web/src/components/shell/Composer.tsx b/packages/collab-web/src/components/shell/Composer.tsx
index 69b2ca033..01bd1a670 100644
--- a/packages/collab-web/src/components/shell/Composer.tsx
+++ b/packages/collab-web/src/components/shell/Composer.tsx
@@ -117,7 +117,7 @@ export function Composer({ client, snapshot }: ComposerProps): ReactNode {
 	const readOnly = snapshot.readOnly;
 	const uiRequest = snapshot.uiRequest;
 	const canPrompt = live && !readOnly;
-	const busy = snapshot.working || (snapshot.state?.isStreaming ?? false);
+	const busy = snapshot.working;
 	const queued = snapshot.state?.queuedMessageCount ?? 0;
 	const canSend = canPrompt && text.trim().length > 0;
 
diff --git a/packages/collab-web/src/lib/client.ts b/packages/collab-web/src/lib/client.ts
index 6de49294c..0ab8e0e30 100644
--- a/packages/collab-web/src/lib/client.ts
+++ b/packages/collab-web/src/lib/client.ts
@@ -334,8 +334,16 @@ export class GuestClient {
 				break;
 			case "state":
 				this.#state = frame.state;
+				// Host state is authoritative for liveness in both directions: the
+				// payload is built at fire time, so `isStreaming` is never stale.
+				// This is the only path that recovers a stuck-idle guest — a dropped
+				// `agent_start` (most often a mid-stream reconnect) otherwise leaves
+				// `#working` false forever, since nothing else sets it true.
+				this.#working = frame.state.isStreaming;
 				if (!frame.state.isStreaming) {
-					this.#working = false;
+					// Host idle implies no tool can be running, so clear any card
+					// pinned by a dropped `tool_execution_end` off this signal.
+					this.#activeTools = new Map();
 					if (this.#streamDone) {
 						this.#stream = null;
 						this.#streamDone = false;
diff --git a/packages/collab-web/test/client.test.ts b/packages/collab-web/test/client.test.ts
index 11f8ada91..087dc1364 100644
--- a/packages/collab-web/test/client.test.ts
+++ b/packages/collab-web/test/client.test.ts
@@ -192,6 +192,34 @@ describe("GuestClient frame apply", () => {
 		client.applyFrameForTest({ t: "state", state: { ...STATE, isStreaming: false } });
 		expect(client.getSnapshot().working).toBe(false);
 	});
+	it("a state frame recovers a stuck-idle guest when agent_start was dropped", () => {
+		// The host begins streaming mid-turn, but the matching `agent_start`
+		// never arrived (e.g. dropped on a reconnect). Before the fix nothing
+		// set `working` true except `agent_start`, so the guest stayed idle.
+		const client = liveClient();
+		expect(client.getSnapshot().working).toBe(false);
+		client.applyFrameForTest({ t: "state", state: { ...STATE, isStreaming: true } });
+		expect(client.getSnapshot().working).toBe(true);
+	});
+
+	it("an idle state frame clears a pinned tool card when tool_execution_end was dropped", () => {
+		// Host reports idle, but the matching `tool_execution_end` was dropped,
+		// leaving a stuck tool card. The authoritative idle signal must clear it.
+		const client = liveClient();
+		client.applyFrameForTest({
+			t: "event",
+			event: {
+				type: "tool_execution_start",
+				toolCallId: "tc1",
+				toolName: "bash",
+				args: { command: "ls" },
+				intent: "Listing",
+			},
+		});
+		expect(client.getSnapshot().activeTools.size).toBe(1);
+		client.applyFrameForTest({ t: "state", state: { ...STATE, isStreaming: false } });
+		expect(client.getSnapshot().activeTools.size).toBe(0);
+	});
 
 	it("bus progress frames update the progress map", () => {
 		const client = liveClient();