[ClayMav]

Summary

A new client cannot recover a known SQL execution through the public driver API. The driver only reattaches queries already tracked in that process, which blocks MCP's Postgres-backed restart recovery.

Add cursor.attach(execution_id, store=original_store) on a connection to the original SQL session. Fetching and cancellation reuse the existing recovery machinery. Attaching sends retrieve_results with attach, never execute_sql. Missing or cancelled executions preserve their existing errors, and a rejected duplicate attach preserves the current execution and both cursors' result handlers.

Related Issues

WBC-1934, a prerequisite for WBC-996 in Modern MCP architecture.

Verification

• uv run pytest tests/test_attach.py tests/test_cursor.py tests/test_reconnect.py -q: 140 passed after the duplicate-attach fix, including preservation of pending/completed executions and successful replacement.
• uv run pytest -q: 349 passed before the final duplicate-attach fix on Python 3.11, with two existing WebSocket deprecation warnings. Covers public attachment to running/completed executions, stored results, cancellation, missing executions, duplicate tracking, invalid IDs, old-session polling, and another transport loss.
• uv run pre-commit run --all-files: all hooks passed.
• uv build: source distribution and wheel built successfully.
• A task-local TLS WebSocket fixture received one execution from a subprocess, which exited abruptly. A new subprocess attached using the saved execution ID and recovered its stored result. The fixture observed exactly one execute_sql and one retrieve_results request with the same ID, with no replay. Both clients, server, and temporary TLS files were cleaned up.

Independent adversarial review of the implementation and duplicate-attach fix found no substantive issues. The fix review independently passed 10 focused tests and an immediate-result check.

On b9763530db0209523fe2dec422392028ec51d765, CI passed on Python 3.10 through 3.14, hosted pre-commit passed, and Salty reviewed with no findings.

No live SQL session, Postgres database, cloud credential, or deployed service was used. Authentication and real server orphan-grace/result-retention behavior need integration qualification. This API neither extends result retention nor provides a durable job store. The remaining MCP work must persist execution identity safely and reconcile uncertain submissions without replaying writes.

---

Requester Checklist

• I have self-reviewed my own code
• I have added/updated tests that prove my fix/feature works
• I have included visual proof (screenshot, video, or test output) if applicable
• All CI checks are passing
• PR size is S/M, OR I have justified the size and added a walkthrough
• I have updated documentation if needed

Visual Proof

Local restart smoke output:

new client recovered the original stored result
one execution, one attach, no replay after process exit: PASS

Size Justification (if L/XL)

The change includes connection and cursor integration plus lifecycle tests. The cursor resets execution state through one shared method so execute and attach preserve the same result isolation.

---

Reviewer Checklist

• Requester checklist above is complete
• All CI checks are passing
• Tests adequately cover the changes

Implemented by GPT-6.1 Sol through T3 Code's Codex harness, with an independent agent review.

[ClayMav]

@salty-hambot review

[salty-hambot]

Reviewed by Salty Hambot 🤖🧂 at b976353

No issues found.
_{💰 $0.1836 · 182.8k in / 3.3k out tokens · ⏱️ 33.7s · us.openai.gpt-6-sol high, prompt coverage-v1
💬 To request a re-review, comment @salty-hambot review}

[ClayMav]

@salty-hambot review

[ClayMav]

Yes. This PR exposes the existing attach primitive: it transfers event ownership, and its duplicate guard is connection-local. It does not fence other live connections. I’ll document those caller obligations in a follow-up. For MCP recovery, a Postgres lease alone is insufficient; before enabling takeover we need server-enforced ownership/generation checks so stale workers cannot reattach or cancel the recovered execution. That remains part of WBC-996.

[ClayMav]

@salty-hambot review