diff --git a/src/headless-triage.ts b/src/headless-triage.ts
index 85a51bb2c..d97873ea1 100644
--- a/src/headless-triage.ts
+++ b/src/headless-triage.ts
@@ -443,6 +443,11 @@ async function defaultAgentRunner(
 			tools: options.tools ?? agent.tools,
 		}) ?? agent.systemPrompt;
 	const appendedPrompt = `${composed}\n\n## Task Input\n\n${task}`;
+	// noOutputTimeoutMs = 60000 (60s): without this, a hung session.prompt
+	// (sf-mp8e02m1-zpk903 — Promise deadlock pre-LLM-dispatch with 0 syscall
+	// activity) blocks for the full timeoutMs (8min) before the parent
+	// abort fires. 60s no-output captures the hang fast enough to keep the
+	// autonomous loop moving while the root-cause investigation continues.
 	const result = await runSubagent(
 		{
 			systemPrompt: appendedPrompt,
@@ -452,7 +457,7 @@ async function defaultAgentRunner(
 			name: agent.name,
 		},
 		task,
-		{ timeoutMs: DEFAULT_AGENT_TIMEOUT_MS },
+		{ timeoutMs: DEFAULT_AGENT_TIMEOUT_MS, noOutputTimeoutMs: 60_000 },
 	);
 	return {
 		ok: result.ok,