diff --git a/src/host-sweep.test.ts b/src/host-sweep.test.ts
index bd2e233..155b1b1 100644
--- a/src/host-sweep.test.ts
+++ b/src/host-sweep.test.ts
@@ -7,12 +7,7 @@ import Database from 'better-sqlite3';
 import { describe, expect, it } from 'vitest';
 
 import { deleteOrphanProcessingClaims, getProcessingClaims } from './db/session-db.js';
-import {
-  ABSOLUTE_CEILING_MS,
-  CLAIM_STUCK_MS,
-  _resetStuckProcessingRowsForTesting,
-  decideStuckAction,
-} from './host-sweep.js';
+import { ABSOLUTE_CEILING_MS, CLAIM_STUCK_MS, resetStuckProcessingRows, decideStuckAction } from './host-sweep.js';
 import type { Session } from './types.js';
 
 const BASE = Date.parse('2026-04-20T12:00:00.000Z');
@@ -253,7 +248,7 @@ describe('resetStuckProcessingRows — orphan claim cleanup', () => {
     // Sanity: the orphan claim is what would trip claim-stuck.
     expect(getProcessingClaims(outDb)).toHaveLength(1);
 
-    _resetStuckProcessingRowsForTesting(inDb, outDb, fakeSession(), 'absolute-ceiling');
+    resetStuckProcessingRows(inDb, outDb, fakeSession(), 'absolute-ceiling', outDb);
 
     // Regression assertion: orphan claim is gone — next sweep tick will see
     // an empty claims list and not kill the freshly respawned container.
@@ -285,7 +280,7 @@ describe('resetStuckProcessingRows — orphan claim cleanup', () => {
       .run(claimedAt, future);
     outDb.prepare("INSERT INTO processing_ack VALUES ('m-2', 'processing', ?)").run(claimedAt);
 
-    _resetStuckProcessingRowsForTesting(inDb, outDb, fakeSession(), 'claim-stuck');
+    resetStuckProcessingRows(inDb, outDb, fakeSession(), 'claim-stuck', outDb);
 
     expect(getProcessingClaims(outDb)).toEqual([]);
     const row = inDb.prepare('SELECT tries FROM messages_in WHERE id = ?').get('m-2') as { tries: number };
diff --git a/src/host-sweep.ts b/src/host-sweep.ts
index 09c82ac..b10ee0d 100644
--- a/src/host-sweep.ts
+++ b/src/host-sweep.ts
@@ -250,20 +250,28 @@ function enforceRunningContainerSla(
   resetStuckProcessingRows(inDb, outDb, session, 'claim-stuck');
 }
 
-export function _resetStuckProcessingRowsForTesting(
-  inDb: Database.Database,
-  outDb: Database.Database,
-  session: Session,
-  reason: string,
-): void {
-  resetStuckProcessingRows(inDb, outDb, session, reason);
-}
-
-function resetStuckProcessingRows(
+/**
+ * Reset retries on inbound rows the container claimed but never acked, and
+ * delete the orphan `processing_ack` rows so the next sweep tick doesn't
+ * see them.
+ *
+ * Safe to call only when the container that owned `outbound.db` is dead —
+ * production callers invoke this either in the `!alive` branch or right
+ * after `killContainer`. Without that guarantee, the orphan-claim delete
+ * would race the container's own writer.
+ *
+ * `writableOutDb` is the same handle outbound writes go through. When
+ * omitted (typical production path) the function reopens `outbound.db`
+ * read-write by session path for the delete and closes that handle on
+ * exit. Callers that already hold a writable handle — including tests
+ * using in-memory DBs — can pass it in to skip the reopen.
+ */
+export function resetStuckProcessingRows(
   inDb: Database.Database,
   outDb: Database.Database,
   session: Session,
   reason: string,
+  writableOutDb?: Database.Database,
 ): void {
   const claims = getProcessingClaims(outDb);
   const now = Date.now();
@@ -300,19 +308,17 @@ function resetStuckProcessingRows(
   // would re-read them, see the old status_changed timestamp, conclude the
   // freshly respawned container is stuck, and SIGKILL it before its
   // agent-runner has a chance to run clearStaleProcessingAcks() on startup.
-  // We're safe to write outbound.db here because we just killed the container
-  // that owned it (or it crashed and left no writer behind).
-  // outDb was opened readonly for reads above; reopen with write access for this delete.
-  let outDbRw: Database.Database | null = null;
+  const ownsDb = !writableOutDb;
+  let useDb: Database.Database | null = writableOutDb ?? null;
   try {
-    outDbRw = openOutboundDbRw(session.agent_group_id, session.id);
-    const cleared = deleteOrphanProcessingClaims(outDbRw);
+    if (!useDb) useDb = openOutboundDbRw(session.agent_group_id, session.id);
+    const cleared = deleteOrphanProcessingClaims(useDb);
     if (cleared > 0) {
       log.info('Cleared orphan processing claims', { sessionId: session.id, cleared, reason });
     }
   } catch (err) {
     log.warn('Failed to clear orphan processing claims', { sessionId: session.id, err });
   } finally {
-    outDbRw?.close();
+    if (ownsDb) useDb?.close();
   }
 }