diff --git a/tests/integration/idle-costs-nothing.test.ts b/tests/integration/idle-costs-nothing.test.ts
index b5c386cf..2374627e 100644
--- a/tests/integration/idle-costs-nothing.test.ts
+++ b/tests/integration/idle-costs-nothing.test.ts
@@ -88,11 +88,36 @@ describe('an idle brain costs nothing', () => {
     }
 
     // (a) + (b): nothing ran, nothing was said.
-    expect(logged.filter((l) => /All indexes flushed to disk/.test(l))).toEqual([])
-    expect(logged.filter((l) => /Flushing Brainy indexes/.test(l))).toEqual([])
+    //
+    // THE SPIES COME FIRST, AND THEY ARE THE ATTRIBUTABLE HALF. They are bound
+    // to THIS brain's providers, so they answer "did this brain flush?" and
+    // nothing else. The console filters below cannot: the gate config runs the
+    // whole suite in ONE process (`pool: 'forks'`, `singleFork: true`), so
+    // `console.log` carries the narration of every brain alive in that
+    // process — including one a previous file opened and never closed, whose
+    // unref'd cadence timer is still doing honest work. A neighbour narrating
+    // is a REAL finding about suite hygiene, but it is not this brain failing
+    // its own law, and the two must not be reported as the same thing.
+    //
+    // So: spies first (whose failure means the engine broke the law), console
+    // second (whose failure means SOMETHING in the process narrated), and the
+    // console assertion carries the captured lines in its message. vitest's
+    // stdout blocks are prefixed `stdout | <file> > <test>`, so those lines
+    // plus the surrounding gate log name the brain that printed them.
     expect(countsSpy).not.toHaveBeenCalled()
     expect(metadataSpy).not.toHaveBeenCalled()
     expect(graphSpy).not.toHaveBeenCalled()
+
+    const flushChatter = logged.filter(
+      (l) => /All indexes flushed to disk/.test(l) || /Flushing Brainy indexes/.test(l)
+    )
+    expect(
+      flushChatter,
+      `a flush narrated during the ${IDLE_WATCH_MS}ms idle window. This brain's own ` +
+        `providers were NOT called (asserted above), so the lines below were printed by ` +
+        `another brain alive in this process — find it by the 'stdout | <file> > <test>' ` +
+        `prefix in the run log:\n${flushChatter.join('\n')}`
+    ).toEqual([])
   }, 180_000)
 
   it('an explicit flush over a clean brain calls no provider and prints nothing', async () => {