Unblock wait_agents on soft interrupt

Soft interrupt leaves the run in flight, and wait status treats
interrupted+inFlight as running so resume cannot collect a stale stamp.
Flip the wait mailbox overlay from interrupt_agent (same as send_input
interrupt:true) so wait returns interrupted without waiting for settle.

Author: TheGreatAxios

CHANGELOG.md

@@ -46,6 +46,8 @@ parallel copies under `docs/` or `scripts/notes/`. At cut time: rename
   longer swallow `--*` or `-h` as their option values.
 - `wait_agents` no longer collects a stale completed or interrupted stamp
   when a followup is already in flight.
+- `interrupt_agent` flips the wait mailbox so soft interrupt unblocks
+  `wait_agents` while the background run is still in flight.
 - Credential-refresh and auth send failures tell the user to log in again
   instead of suggesting `/model`.
 

src/subagent/agent-fleet.test.ts

@@ -1033,8 +1033,10 @@ describe("interrupt_agent unblocks wait_agents", () => {
     });
     const id = spawned.agent_id as string;
 
-    // interruptOne is wait-terminal via session interrupted; collect freezes it.
+    // Soft interrupt leaves the run in flight; the mailbox overlay is what
+    // makes wait terminal (same path interrupt_agent takes).
     expect(deps.sessions.interruptOne(id).ok).toBe(true);
+    deps.fleetRecords.interrupt(id);
     expect(deps.fleetRecords.peek(id)?.status).toBe("interrupted");
 
     const waited = await callTool(wait, { targets: [id], timeout_ms: 5000 });
@@ -1116,6 +1118,10 @@ describe("interrupt_agent unblocks wait_agents", () => {
     fleetRecords.register(worker.id);
     sessions.registerInterrupt(worker.id, () => {});
     sessions.interruptOne(worker.id);
+    // Mirror interrupt_agent: soft interrupt alone projects as running while
+    // in-flight, so the mailbox must flip for wait to see "interrupted".
+    fleetRecords.interrupt(worker.id);
+    fleetRecords.interrupt(worker.id);
 
     const wait = createWaitAgentsTool({ sessions, fleetRecords });
     const waited = await callTool(wait, { targets: [worker.id], timeout_ms: 1000 });

src/subagent/lifecycle-tools.ts

@@ -121,7 +121,7 @@ export type CloseAgentToolDeps = LifecycleToolDeps & {
   fleetRecords: FleetMailboxHandle;
 };
 
-/** interrupt_agent stamps session interrupted; wait JSON projects that lifecycle. */
+/** interrupt_agent stamps session interrupted and flips the wait mailbox overlay. */
 export type InterruptAgentToolDeps = LifecycleToolDeps & {
   fleetRecords: FleetMailboxHandle;
 };
@@ -299,6 +299,10 @@ export function createInterruptAgentTool(deps: InterruptAgentToolDeps): AgentToo
           `Error: cannot interrupt "${target}" (status: ${outcome.status}).`,
         );
       }
+      // Soft interrupt leaves the run in flight; projectWaitStatus treats
+      // interrupted+inFlight as running so resume cannot collect a stale stamp.
+      // Flip the wait mailbox overlay here (same as send_input interrupt:true).
+      deps.fleetRecords.interrupt(target);
       return lifecycleResult(
         call.id,
         JSON.stringify({ agent_id: target, status: "interrupted" satisfies AgentLifecycleStatus }),