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Nicky LeachandPaperclip
ed8075b535
## Thinking Path > - Paperclip is the open source app people use to manage AI agents for work > - Agent adapters can run through a sandbox process-session bridge > - The bridge writes streamed standard input to files before the remote process reads them > - Concurrent file writes can make a later chunk visible before an earlier chunk > - The remote process can then parse a tail fragment and wait forever for the missing head > - This pull request serializes host writes and makes an unexpected file gap a loud error > - The benefit is ordered input with a bounded failure path for sandbox ACP sessions ## Linked Issues or Issue Description No public GitHub issue exists for this change. The description below follows `.github/ISSUE_TEMPLATE/bug_report.yml`. **What happened?** A sandbox ACP process-session bridge could stall after its handshake when a run sent a large prompt. The host sent one un-awaited file write for each standard input chunk. A small later chunk could finish before a large earlier chunk. The remote poller then sent the tail bytes first. The agent parser raised an error on the tail fragment, and the head bytes stayed buffered without a newline. **Expected behavior** The bridge must expose standard input files in sequence. The remote poller must report a clear error when an earlier file remains missing beyond the retry budget. **Steps to reproduce** 1. Start an ACP session through a sandbox process-session bridge. 2. Send a prompt that produces multiple standard input file chunks. 3. Delay finalization of an earlier chunk while a later chunk completes. 4. Observe that the remote parser can receive the later chunk first and the session can stop without a clear error. **Paperclip version or commit** The change targets the current `master` branch at the submitted commit. **Deployment mode** The bug affects sandbox execution. **Agent adapter(s) involved** The failure affects the ACP process-session bridge. **Database mode** Not database-related. **Additional context** The fix keeps the existing per-file atomic write behavior. It adds ordering at the host write boundary and a bounded ordering check in the shared wrapper poll tail. ## What Changed - Add a per-session promise chain for host standard input file writes. - Keep a failed write from blocking later chain entries. - Track the next expected sequence number in the shared wrapper poll tail. - Hold later files while an earlier file is missing within the existing retry budget. - Emit a loud error and advance after the retry budget expires. - Add regression tests for host ordering, gap holding, and the loud error path. ## Verification - `npx vitest run packages/adapter-utils/src/execution-target-stdin-race.test.ts` — 9 tests passed. - `npx vitest run packages/adapter-utils/src/execution-target-sandbox.test.ts` — 43 tests passed. - `pnpm --filter @paperclipai/adapter-utils typecheck` — clean. - With the source fix reverted, the 3 new tests fail and the 6 original tests pass. - CI must pass on the pull request before merge. ## Risks Low risk. - The host now serializes writes for each session, which can reduce write parallelism. - A failed write still emits one error and destroys the socket, as before. - The wrapper can emit a loud error after the existing retry budget when a file gap persists. - The change does not alter the atomic per-file write behavior. ## Model Used OpenAI GPT-5, model ID `gpt-5`, with tool use and code execution. The context window and internal reasoning details are not disclosed. ## 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>