## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work.
> - The package-local host boundary is ready for a concrete ACP
implementation, but the first production profile is Codex only.
> - ACPX must not inherit the server process environment or choose an
executable by pathname after admission.
> - Codex must not re-enable ambient apps, memory, skills, MCP
configuration, or instructions inside its isolated home.
> - This pull request pins only the two required production packages and
applies narrowly tested host patches.
> - The benefit is a minimal dependency boundary that follows the
repository's CI-owned lockfile process.
## Linked Issues or Issue Description
**Agent or provider**
Codex through `acpx@0.13.1` and `@agentclientprotocol/codex-acp@1.6.2`.
**Why this adapter is useful**
The injected runtime host needs a concrete ACP session manager and the
exact reviewed Codex ACP server. Upstream ACPX does not yet expose a
host-owned spawn callback, and upstream Codex ACP does not yet apply
Paperclip's isolated instruction, MCP, app, memory, and skill boundary.
Both behaviors are required before the dependency can execute inside the
runner.
**How the agent is invoked**
The next pull request will adapt these pinned packages to the private
runtime host. ACPX receives a host-owned callback that consumes the
already verified executable lease. Codex receives only the isolated
environment, explicit base instructions, explicit MCP servers, and the
skills rooted in its private `CODEX_HOME`. This pull request alone does
not spawn either package or register an adapter.
**Additional context**
This pull request is stacked on #12399. It adds no Pi, Claude, AWS, SDK,
lab, browser, or UI dependency. It intentionally does not commit
`pnpm-lock.yaml`: the repository policy job regenerates a manifest-only
PR lockfile artifact for downstream frozen installs, and the lockfile
bot updates master separately.
## What Changed
- Pin `acpx` to `0.13.1` and the Codex ACP server to `1.6.2` in the
runner package.
- Register both patches in the pnpm 9 root configuration and newer-pnpm
workspace configuration.
- Preserve the existing embedded-Postgres and ACPX 0.12 patch entries
used by other packages.
- Patch ACPX to evaluate an allowlisted environment at child-spawn time
and keep spawn cwd out of provider-visible session identity.
- Patch ACPX to accept a host-owned spawn callback with the resolved
arguments and options, allowing the verified command lease to own
execution.
- Patch Codex ACP to retain runner-owned MCP server identity in
permission requests.
- Patch Codex ACP to pass explicit Paperclip base instructions on both
start and resume.
- In isolated mode, disable ambient apps, memory, and existing MCP
configuration; load skills only from `CODEX_HOME`; and configure only
requested servers.
- Add a package contract test that enforces exact versions, Codex-only
dependency scope, both pnpm patch registries, and every required patch
hook.
## Verification
- Both patch files dry-apply successfully to fresh published tarballs
for `acpx@0.13.1` and `@agentclientprotocol/codex-acp@1.6.2`.
- A local no-lockfile install applied both patches; their runtime
markers and exact installed versions were inspected.
- Runner TypeScript typecheck — passed against the patched packages.
- Runner package tests — passed: 16 Node protocol/package tests and 426
Vitest tests.
- `pnpm -r typecheck` — passed for all applicable workspaces.
- `pnpm build` — passed, including runner binary, server, UI, and
workspace packages.
- `git diff --check` — passed.
- The diff contains 6 files and does not change `pnpm-lock.yaml`, a
GitHub workflow, server selection, or UI behavior.
## Risks
The primary risk is drift between published package contents and
checked-in compiled patches. Exact versions are pinned, both patches are
exercised by package-contract gates, and CI performs the authoritative
regenerated-lockfile frozen install. The spawn callback does not grant a
new executable path: the following adapter must consume the opaque
verified command lease. Codex isolation changes activate only when
`PAPERCLIP_ACPX_ISOLATED_CONTEXT=1`, so existing direct Codex adapters
are unaffected.
## Model Used
OpenAI Codex with GPT-5 and repository tool use.
## 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 linked an existing public item or described the
issue in this PR
- [x] I have not referenced internal or instance-local Paperclip issues
or links
- [x] My branch name describes the change and contains no internal task
identifier
- [x] I have run the affected tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have documented the dependency, patch, isolation, and lockfile
boundaries
- [ ] All applicable GitHub Actions are green
- [ ] Greptile is 5/5 with every actionable comment resolved
- [x] I will address all review findings before requesting merge
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