diff --git a/packages/paperclip-runner/src/live/runnerd-codex-transport.test.ts b/packages/paperclip-runner/src/live/runnerd-codex-transport.test.ts
index 99c26734f8..1b00e118cf 100644
--- a/packages/paperclip-runner/src/live/runnerd-codex-transport.test.ts
+++ b/packages/paperclip-runner/src/live/runnerd-codex-transport.test.ts
@@ -643,6 +643,46 @@ it("retargets only composed instruction framing and retains legacy custom instru
 
 });
 
+it.each([false, true])("preserves ACPX asset framing across cold, warm, and post-idle attachment (guidance=%s)", (guidance) => {
+  const source = assignedRuntimeContext("/controller/skills", "/controller/bundle");
+  const cold = assignedRuntimeContext("/boat/skills", "/boat/context/cold");
+  const resumed = assignedRuntimeContext("/boat/skills", "/boat/context/resumed");
+  const custom = "Managed instructions with literal /controller/bundle example.";
+  const original = composeNativeSystemInstructions(source, custom);
+  const coldText = runnerdRecoveryInternals.retargetComposedInstructions(
+    runnerdRecoveryInternals.withComputerProcessInstructions(original, guidance, source),
+    source,
+    cold,
+  );
+  const suffix = (context: NativeRuntimeContextSnapshot) =>
+    composeNativeSystemInstructions(context, "").slice(context.prompt.text.length);
+  expect(coldText.endsWith(suffix(cold))).toBe(true);
+  const state = { runAttachTemplate: { provider: {
+    kind: "acpx", agent: "claude", runId: "cold-run", runtimeContext: cold, instructions: coldText,
+  } } };
+  const desired = {
+    runnerInstanceId: "runner", environmentLeaseId: "workspace", runId: "warm-run",
+    normalizedSessionId: "same-session", turnId: "turn", itemId: "item",
+  };
+  const warm = runnerdRecoveryInternals.rotatedRunAttachPayload(state, desired, null, undefined);
+  expect((warm.provider as { instructions: string }).instructions).toBe(coldText);
+  const recover = (text: string) => runnerdRecoveryInternals.rotatedRunAttachPayload(
+    { runAttachTemplate: warm }, { ...desired, runId: "post-idle-run" }, null, undefined, resumed,
+    { text, context: source },
+  ).provider as { instructions: string; runtimeContext: NativeRuntimeContextSnapshot };
+  const recovered = recover(composeNativeSystemInstructions(source, custom));
+  expect(recovered.runtimeContext).toEqual(resumed);
+  expect(recovered.instructions.endsWith(suffix(resumed))).toBe(true);
+  // This is the immutable-prefix equality required by Claude's guest guard.
+  expect(recovered.instructions.slice(0, -suffix(resumed).length))
+    .toBe(coldText.slice(0, -suffix(cold).length));
+  expect(recovered.instructions).toContain(custom);
+  expect(recovered.instructions).not.toContain("Read-only instruction sibling root: /controller/");
+  // Never silently substitute old managed instructions for current grants.
+  expect(recover(composeNativeSystemInstructions(source, "Changed managed instructions")).instructions)
+    .toContain("Changed managed instructions");
+});
+
 it("replays the durable run attachment outcome and latest provider identity", () => {
   expect(
     runnerdRecoveryInternals.recoveredRunAttachment({