diff --git a/.gitignore b/.gitignore
index 8187eebb8..046e458b7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,6 +30,14 @@ subagents/
 
 # Working notes and design spikes — local only, never committed
 docs/plans/
+# Fleet/harness working notes — local only, never committed
+plans/
+
+# Benchmark/eval scratch — local only, never committed
+tb-dataset/
+tb-rerun-50/
+terminal-bench/
+evals/**/__pycache__/
 
 # Scratch repro tests — never committed
 __repro/
diff --git a/src/provider/inference-dependencies.ts b/src/provider/inference-dependencies.ts
index 9a28ad486..ee4b8c58b 100644
--- a/src/provider/inference-dependencies.ts
+++ b/src/provider/inference-dependencies.ts
@@ -19,6 +19,7 @@ import { GROK_RESPONSES_PROVIDER } from "./grok-responses.js";
 import { withAnthropicCacheBreakpoint } from "./anthropic-cache-breakpoint.js";
 import { withReplaySanitizer } from "./replay-sanitizer.js";
 import { isPollOnlyPendingBatch } from "../subagent/poll-exempt.js";
+import { isIdempotentTaskBatch } from "../subagent/idempotent-task-exempt.js";
 import { OPENCODE_GO_PROVIDER_ID } from "../../packages/opencode-go/src/index.js";
 import { BIFROST_PROVIDER } from "./bifrost-adapter.js";
 import { OPENAI_RESPONSES_PROVIDER } from "./openai-responses.js";
@@ -101,7 +102,13 @@ export function createInferenceDependencies(): Promise<Dependencies> {
       .then((deps) => ({
         ...deps,
         fetch: withCodexContentTypeRepair(deps.fetch),
-        isPollOnlyPendingBatch,
+        // Compose the first-party doom-loop exemptions into the single liveness
+        // hook the vendored reactor already consumes: still-pending polls and
+        // idempotent task bookkeeping both reset the repeat streak instead of
+        // counting toward the fail-run threshold.
+        isPollOnlyPendingBatch: (calls, results) =>
+          isPollOnlyPendingBatch(calls, results) ||
+          isIdempotentTaskBatch(calls, results),
       }));
   }
   return cached;
diff --git a/src/subagent/idempotent-task-exempt.test.ts b/src/subagent/idempotent-task-exempt.test.ts
new file mode 100644
index 000000000..947cb82e4
--- /dev/null
+++ b/src/subagent/idempotent-task-exempt.test.ts
@@ -0,0 +1,59 @@
+import { describe, expect, test } from "bun:test";
+import type { ToolCall, ToolResult } from "@intx/types/runtime";
+import { isIdempotentTaskBatch } from "./idempotent-task-exempt.js";
+
+function call(name: string, id = "c1"): ToolCall {
+  return { id, name, arguments: {} };
+}
+
+function taskResult(): ToolResult {
+  return { callId: "c1", content: "{}" };
+}
+
+describe("isIdempotentTaskBatch", () => {
+  test("manage_tasks batch is exempt", () => {
+    expect(isIdempotentTaskBatch([call("manage_tasks")], [taskResult()])).toBe(
+      true,
+    );
+  });
+
+  test("todowrite alias is exempt", () => {
+    expect(isIdempotentTaskBatch([call("todowrite")], [taskResult()])).toBe(
+      true,
+    );
+  });
+
+  test("update_plan hidden alias is exempt", () => {
+    expect(isIdempotentTaskBatch([call("update_plan")], [taskResult()])).toBe(
+      true,
+    );
+  });
+
+  test("repeated task-only batches stay exempt", () => {
+    expect(
+      isIdempotentTaskBatch(
+        [call("todowrite", "c1"), call("todowrite", "c2")],
+        [taskResult(), { callId: "c2", content: "{}" }],
+      ),
+    ).toBe(true);
+  });
+
+  test("a real tool in the batch is never exempt", () => {
+    expect(
+      isIdempotentTaskBatch(
+        [call("todowrite"), call("run_shell")],
+        [taskResult(), { callId: "c2", content: "{}" }],
+      ),
+    ).toBe(false);
+  });
+
+  test("non-task tools are never exempt", () => {
+    expect(isIdempotentTaskBatch([call("run_shell")], [taskResult()])).toBe(
+      false,
+    );
+  });
+
+  test("empty batches are never exempt", () => {
+    expect(isIdempotentTaskBatch([], [])).toBe(false);
+  });
+});
diff --git a/src/subagent/idempotent-task-exempt.ts b/src/subagent/idempotent-task-exempt.ts
new file mode 100644
index 000000000..3a2d7ba1d
--- /dev/null
+++ b/src/subagent/idempotent-task-exempt.ts
@@ -0,0 +1,23 @@
+import { isSameTool } from "../agent/canonical-tool-name.js";
+import type { ToolCall, ToolResult } from "@intx/types/runtime";
+
+/**
+ * Doom-loop exemption for idempotent task bookkeeping. A batch is exempt only
+ * when it is non-empty and every executed call is a task-bookkeeping tool
+ * (`manage_tasks` — `isSameTool` folds the `todowrite` and `update_plan`
+ * aliases onto that engine id).
+ *
+ * Repeating an identical task update is legitimate bookkeeping, not a runaway
+ * loop: "finalize checklist" three times changes nothing and should not
+ * abort an otherwise-finished run under the `fail-run` policy. This resets
+ * the doom-loop streak (same mechanism as the poll exemption) so consecutive
+ * task-only batches never accumulate toward the threshold, while any real
+ * tool in the batch counts normally and always preserves the guard.
+ */
+export function isIdempotentTaskBatch(
+  calls: readonly ToolCall[],
+  _results: readonly ToolResult[],
+): boolean {
+  if (calls.length === 0) return false;
+  return calls.every((call) => isSameTool(call.name, "manage_tasks"));
+}