feat(subagent): increase default timeout from 10 min to 30 min

A subagent that times out loses all its work, so a generous default
reduces wasted compute. Update the constant, tool description, system
prompt guidelines, and documentation to reflect the new 1800s default.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/agent/subagent/README.md

@@ -123,7 +123,7 @@ The subagent system allows a parent agent to spawn isolated child agents that ru
 | `announce.ts` | System prompt builder, findings reader, message formatter, delivery |
 | `announce-queue.ts` | Debounced queue for batching announcements when parent is busy |
 | `command-queue.ts` | Concurrency limiter for subagent lane slots |
-| `lanes.ts` | Lane config: max concurrency (10), default timeout (600s) |
+| `lanes.ts` | Lane config: max concurrency (10), default timeout (1800s) |
 | `types.ts` | Shared types: SubagentRunRecord, SubagentRunOutcome, etc. |
 | `registry-store.ts` | Persistence: save/load runs to disk for crash recovery |
 
@@ -159,10 +159,10 @@ Child run error (e.g., missing API key for provider)
 
 ## Timeout Behavior
 
-Default: 600s (10 min). System prompt guides the parent LLM:
-- Simple tasks: 600s (default)
-- Moderate tasks: 900-1200s (15-20 min)
-- Complex tasks: 1200-1800s (20-30 min)
+Default: 1800s (30 min). System prompt guides the parent LLM:
+- Simple tasks: 1800s (default)
+- Moderate tasks: 1800-2400s (30-40 min)
+- Complex tasks: 2400-3600s (40-60 min)
 
 On timeout:
 1. Timeout timer fires in `watchChildAgent()`

packages/core/src/agent/subagent/lanes.ts

@@ -10,8 +10,8 @@ export const DEFAULT_SUBAGENT_MAX_CONCURRENT = 10;
 // Timeout defaults
 // ---------------------------------------------------------------------------
 
-/** Default subagent timeout: 10 minutes. */
-export const DEFAULT_SUBAGENT_TIMEOUT_SECONDS = 600;
+/** Default subagent timeout: 30 minutes. */
+export const DEFAULT_SUBAGENT_TIMEOUT_SECONDS = 1800;
 
 /** Maximum safe value for setTimeout (~24.8 days). */
 const MAX_SAFE_TIMEOUT_MS = 2_147_000_000;
@@ -19,7 +19,7 @@ const MAX_SAFE_TIMEOUT_MS = 2_147_000_000;
 /**
  * Resolve the effective timeout in milliseconds for a subagent run.
  *
- * - `undefined` / negative → default (600 s)
+ * - `undefined` / negative → default (1800 s)
  * - `0`                    → no timeout (MAX_SAFE_TIMEOUT_MS)
  * - positive number        → use as-is, clamped to safe range
  */

packages/core/src/agent/subagent/registry.ts

@@ -273,7 +273,7 @@ function watchChildAgent(record: SubagentRunRecord, timeoutSeconds?: number): Pr
       resolveSlot(); // Release the queue slot
     };
 
-    // Always set a timeout (default 10 min, 0 = ~24 days via resolveSubagentTimeoutMs)
+    // Always set a timeout (default 30 min, 0 = ~24 days via resolveSubagentTimeoutMs)
     const timeoutTimer = setTimeout(() => {
       cleanup({ status: "timeout" });
 

packages/core/src/agent/system-prompt/sections.ts

@@ -299,9 +299,9 @@ export function buildConditionalToolSections(
       "",
       "### Timeout Guidelines",
       "Set timeoutSeconds generously — a sub-agent that times out loses all its work.",
-      "- Simple tasks (search, read, summarize): 600 (10 min, the default)",
-      "- Moderate tasks (multi-step research, file downloads + analysis): 900–1200 (15–20 min)",
-      "- Complex tasks (code generation, PDF creation, multi-file operations): 1200–1800 (20–30 min)",
+      "- Simple tasks (search, read, summarize): 1800 (30 min, the default)",
+      "- Moderate tasks (multi-step research, file downloads + analysis): 1800–2400 (30–40 min)",
+      "- Complex tasks (code generation, PDF creation, multi-file operations): 2400–3600 (40–60 min)",
       "When in doubt, use a longer timeout.",
       "",
     );

packages/core/src/agent/tools/sessions-spawn.ts

@@ -29,7 +29,7 @@ const SessionsSpawnSchema = Type.Object({
   timeoutSeconds: Type.Optional(
     Type.Number({
       description:
-        "Execution timeout in seconds. Default: 600 (10 min). " +
+        "Execution timeout in seconds. Default: 1800 (30 min). " +
         "Set to 0 for no timeout (useful for complex, long-running tasks). " +
         "The subagent will be terminated if it exceeds this limit.",
       minimum: 0,