diff --git a/packages/coding-agent/src/modes/acp/acp-agent.ts b/packages/coding-agent/src/modes/acp/acp-agent.ts
index 86d2dca49..966bedcd8 100644
--- a/packages/coding-agent/src/modes/acp/acp-agent.ts
+++ b/packages/coding-agent/src/modes/acp/acp-agent.ts
@@ -703,7 +703,13 @@ export class AcpAgent implements Agent {
 			return;
 		}
 
-		await record.session.prompt(text, { images });
+		const agentInvoked = await record.session.prompt(text, { images });
+		// Extension and custom-TS commands are handled locally inside session.prompt()
+		// without calling the LLM, so no agent_end event fires and the turn would hang.
+		// Finish it here when the session confirms no agent was invoked.
+		if (!agentInvoked) {
+			this.#finishPrompt(record, { stopReason: "end_turn" });
+		}
 	}
 
 	async #tryRunSkillCommand(record: ManagedSessionRecord, text: string): Promise<boolean> {
diff --git a/packages/coding-agent/src/session/agent-session.ts b/packages/coding-agent/src/session/agent-session.ts
index a86fce63f..9200b0f0b 100644
--- a/packages/coding-agent/src/session/agent-session.ts
+++ b/packages/coding-agent/src/session/agent-session.ts
@@ -4398,21 +4398,28 @@ export class AgentSession {
 	 * @throws Error if streaming and no streamingBehavior specified
 	 * @throws Error if no model selected or no API key available (when not streaming)
 	 */
-	async prompt(text: string, options?: PromptOptions): Promise<void> {
+	/**
+	 * Returns `false` when the command was fully handled locally (extension or
+	 * custom-TS command consumed without calling the LLM). Returns `true` when
+	 * the prompt was forwarded to the agent — either directly or queued as a
+	 * steer/follow-up. Callers that render a UI or manage turn lifecycle (e.g.
+	 * the ACP agent) use this to know whether to expect an `agent_end` event.
+	 */
+	async prompt(text: string, options?: PromptOptions): Promise<boolean> {
 		const expandPromptTemplates = options?.expandPromptTemplates ?? true;
 
 		// Handle extension commands first (execute immediately, even during streaming)
 		if (expandPromptTemplates && text.startsWith("/")) {
 			const handled = await this.#tryExecuteExtensionCommand(text);
 			if (handled) {
-				return;
+				return false;
 			}
 
 			// Try custom commands (TypeScript slash commands)
 			const customResult = await this.#tryExecuteCustomCommand(text);
 			if (customResult !== null) {
 				if (customResult === "") {
-					return;
+					return false;
 				}
 				text = customResult;
 			}
@@ -4446,7 +4453,7 @@ export class AgentSession {
 			for (const notice of keywordNotices) {
 				await this.sendCustomMessage(notice, { deliverAs: options.streamingBehavior });
 			}
-			return;
+			return true;
 		}
 
 		// Skip eager todo prelude when the user has already queued a directive
@@ -4486,6 +4493,7 @@ export class AgentSession {
 		if (!options?.synthetic) {
 			await this.#enforcePlanModeToolDecision();
 		}
+		return true;
 	}
 
 	async promptCustomMessage<T = unknown>(
diff --git a/packages/coding-agent/test/agent-session-empty-stop-guard.test.ts b/packages/coding-agent/test/agent-session-empty-stop-guard.test.ts
index eb9495ef0..b96391ae4 100644
--- a/packages/coding-agent/test/agent-session-empty-stop-guard.test.ts
+++ b/packages/coding-agent/test/agent-session-empty-stop-guard.test.ts
@@ -136,7 +136,7 @@ function reminderMessages(messages: AgentMessage[]): AgentMessage[] {
 	});
 }
 
-async function expectPromptCompletes(prompt: Promise<void>): Promise<void> {
+async function expectPromptCompletes(prompt: Promise<boolean>): Promise<void> {
 	await Promise.race([
 		prompt,
 		Bun.sleep(1_000).then(() => {
diff --git a/packages/coding-agent/test/issue-927-repro.test.ts b/packages/coding-agent/test/issue-927-repro.test.ts
index 5e1c9c5c5..25fa740dd 100644
--- a/packages/coding-agent/test/issue-927-repro.test.ts
+++ b/packages/coding-agent/test/issue-927-repro.test.ts
@@ -44,7 +44,7 @@ describe("issue #927 optimistic pending spinner", () => {
 			settings: Settings.isolated(),
 			modelRegistry,
 		});
-		vi.spyOn(session, "prompt").mockResolvedValue(undefined);
+		vi.spyOn(session, "prompt").mockResolvedValue(true);
 		mode = new InteractiveMode(session, "test");
 		mode.addMessageToChat = vi.fn();
 		mode.ui.requestRender = vi.fn();
diff --git a/packages/coding-agent/test/main-interactive-input.test.ts b/packages/coding-agent/test/main-interactive-input.test.ts
index 835a97a13..754d91ea2 100644
--- a/packages/coding-agent/test/main-interactive-input.test.ts
+++ b/packages/coding-agent/test/main-interactive-input.test.ts
@@ -21,7 +21,7 @@ describe("submitInteractiveInput", () => {
 			checkShutdownRequested: vi.fn(async () => {}),
 		};
 		const session = {
-			prompt: vi.fn(async () => {}),
+			prompt: vi.fn(async () => true),
 			promptCustomMessage: vi.fn(async () => {}),
 		};
 		const input = createInput({ text: "resume now", started: true, synthetic: true });
@@ -42,7 +42,7 @@ describe("submitInteractiveInput", () => {
 			checkShutdownRequested: vi.fn(async () => {}),
 		};
 		const session = {
-			prompt: vi.fn(async () => {}),
+			prompt: vi.fn(async () => true),
 			promptCustomMessage: vi.fn(async () => {}),
 		};
 		const input = createInput();
@@ -63,7 +63,7 @@ describe("submitInteractiveInput", () => {
 			checkShutdownRequested: vi.fn(async () => {}),
 		};
 		const session = {
-			prompt: vi.fn(async () => {}),
+			prompt: vi.fn(async () => true),
 			promptCustomMessage: vi.fn(async () => {}),
 		};
 		const input = createInput({ text: "continue goal", customType: "goal-continuation" });
diff --git a/packages/coding-agent/test/task/executor-wall-clock.test.ts b/packages/coding-agent/test/task/executor-wall-clock.test.ts
index fed13d140..1a5f6ec56 100644
--- a/packages/coding-agent/test/task/executor-wall-clock.test.ts
+++ b/packages/coding-agent/test/task/executor-wall-clock.test.ts
@@ -41,6 +41,7 @@ function createHangingSession(): HangingSessionHandle {
 		subscribe: (_listener: (event: AgentSessionEvent) => void) => () => {},
 		prompt: async (_text: string, _options?: PromptOptions) => {
 			await hang;
+			return true;
 		},
 		waitForIdle: async () => {
 			await hang;
@@ -140,7 +141,7 @@ describe("runSubprocess wall clock (task.maxRuntimeMs)", () => {
 				});
 				return () => {};
 			},
-			prompt: async () => {},
+			prompt: async () => true,
 			waitForIdle: async () => {},
 			getLastAssistantMessage: () => undefined,
 			abort: async () => {},
@@ -218,6 +219,7 @@ describe("runSubprocess wall clock (task.maxRuntimeMs)", () => {
 			},
 			prompt: async (_text: string, _options?: PromptOptions) => {
 				await hang;
+				return true;
 			},
 			waitForIdle: async () => {
 				await hang;
@@ -294,7 +296,7 @@ describe("runSubprocess wall clock (task.maxRuntimeMs)", () => {
 				});
 				return () => {};
 			},
-			prompt: async () => {},
+			prompt: async () => true,
 			waitForIdle: async () => {},
 			getLastAssistantMessage: () => undefined,
 			abort: async () => {},