## Thinking Path
> - Paperclip is the open source control plane people use to manage AI
agents for work.
> - Local agent heartbeats need durable process identity so the server
can supervise them.
> - The ACPX runtime owns the child process used by `codex_local`
sessions.
> - ACPX did not expose the child PID and start time to the Paperclip
adapter.
> - Warm ACPX runtimes can also serve a later heartbeat without a new
spawn event.
> - A hot restart could therefore classify a live Codex run as lost
because its heartbeat row had no process identity.
> - This pull request forwards ACPX spawn identity, reuses it for
compatible warm heartbeats, and fails closed when identity cannot be
persisted.
> - The benefit is reliable hot-restart adoption for eligible local
Codex runs.
## Linked Issues or Issue Description
No matching public GitHub issue was found.
**What happened?**
A `codex_local` heartbeat could run through ACPX without a persisted
`processPid` or `processStartedAt`. A Paperclip hot restart then had no
durable identity for the live ACP child. Recovery could classify the run
as `process_lost` even while the child was still alive.
**Expected behavior**
ACPX reports the real child PID and start time before the first prompt.
A compatible warm runtime reports the same known identity to each later
heartbeat that reuses the child. ACPX stops the child if the identity is
invalid or persistence fails. Hot-restart recovery can then adopt the
live run.
**Steps to reproduce**
1. Start a `codex_local` heartbeat through the ACPX execution lane.
2. Keep the run active during a Paperclip hot restart.
3. Inspect the heartbeat row before this change.
4. Observe that the process identity can be null and recovery cannot
adopt the live child.
**Reproduced on**
- Paperclip `master` before this change.
- Linux source deployment.
- `codex_local` with ACPX `0.12.0`.
## What Changed
- Add an awaited `onAgentSpawn` lifecycle hook to the patched ACPX
runtime.
- Forward the ACP child PID and start time through the adapter `onSpawn`
callback.
- Keep a mutable callback sink for cached runtimes so a later respawn
updates the current heartbeat.
- Reuse the last known process identity when a compatible warm heartbeat
reuses the existing child.
- Kill the ACP child and fail session startup when the PID is invalid or
identity persistence rejects.
- Add ACPX and heartbeat recovery tests for callback ordering, warm
reuse, failure cleanup, durable row identity, and hot-restart adoption.
- Document the one-time drain required when an installed pre-fix run
already lacks process metadata.
## Verification
-
`PAPERCLIP_HOME="$PAPERCLIP_RUN_SCRATCH_DIR/test-home-execute-escalated"
pnpm exec vitest run
packages/adapter-utils/src/acpx-engine/execute.test.ts` — 89 passed.
-
`PAPERCLIP_HOME="$PAPERCLIP_RUN_SCRATCH_DIR/test-home-recovery-escalated"
pnpm exec vitest run
server/src/__tests__/heartbeat-process-recovery.test.ts` — 92 passed.
-
`PAPERCLIP_HOME="$PAPERCLIP_RUN_SCRATCH_DIR/test-home-remote-smoke-escalated"
pnpm exec vitest run
packages/adapter-utils/src/acpx-engine/remote-spawn-smoke.test.ts` — 3
passed.
-
`PAPERCLIP_HOME="$PAPERCLIP_RUN_SCRATCH_DIR/test-home-ci-repro-escalated"
pnpm exec vitest run
server/src/__tests__/heartbeat-dependency-scheduling.test.ts` — 6
passed.
- `pnpm --filter @paperclipai/adapter-utils typecheck` — passed.
- Reverse and forward dry-run application of `patches/acpx@0.12.0.patch`
— passed.
- `git diff --check` — passed.
- `git diff --exit-code origin/master...HEAD -- pnpm-lock.yaml` —
passed.
- `git diff --exit-code origin/master...HEAD -- .github/workflows` —
passed.
## Risks
- Runtime risk is low to moderate. ACPX now awaits process-identity
persistence during child startup.
- ACPX kills the child when persistence fails. This prevents an
unsupervised process, but it makes that heartbeat fail visibly.
- A compatible warm heartbeat reuses the identity of the existing ACP
child. Regression tests verify that identity is persisted before the
next prompt.
- The change updates the vendored ACPX patch. Package installation must
apply that patch.
- There are no schema, migration, public API, UI, workflow, or lockfile
changes.
> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.
## Model Used
- OpenAI Codex used GPT-5.3-Codex for the earlier implementation.
- OpenAI Codex used GPT-5 for the lifecycle-hook revision and the
current fail-closed review fix. The runtime did not expose a more
specific snapshot ID or context-window size. Both runs used reasoning,
repository tools, and code execution.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
---------
Co-authored-by: Paperclip <noreply@paperclip.ing>
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