Building with Codex

Case 01 of 03 · Public contribution

Adding S3 ETag support to Inspect AI

I contributed a change to Inspect AI so callers could keep the ETag returned by an S3 write. Review caught a compatibility problem, which needed a repair before the change was merged.

Keep the token from the write

An ETag is a token used to check whether an S3 object has changed. A caller reads a log, writes an update, then wants to make another conditional write. It needs the ETag returned by the first write so it can detect an intervening change.

API shape · illustrative, not a runnable S3 example

result = write_eval_log(log, location)
etag_from_that_write = result.etag

PR #4713 added WriteEvalLogResult to the synchronous and asynchronous write APIs. The ETag comes from the S3 write itself; non-S3 writes return a result whose etag is None. Callers that asserted the whole return value was None need to adapt.

Issue #4699 describes the chained-write requirement. Read the contribution on GitHub.

Review changed the implementation

The first maintainer review requested changes to ETag capture, trace restoration, missing-object handling, documentation of private library coupling and end-to-end tests, and a stale helper docstring. The repair used the classic transfer manager to avoid a transfer path bypassing ETag capture, restored tracing consistently, and normalized missing-object errors.

A subsequent review accepted those five repairs but found a new compatibility problem in the header-only S3 read path. A direct asynchronous S3 get_object call needed an asyncio event loop; Inspect also supported Trio, a different way to run asynchronous Python code.

Make the read work with Trio too

The read path moved to backend-aware AsyncFilesystem.read_file(location), preserving missing-object handling. The regression test test_write_eval_log_async_s3_header_only_supports_trio checked persisted metadata and the returned ETag under Trio.

Read the reviewer’s finding → read the author’s repair reply.

The useful pattern is specific: a write-result change exposed a read-path assumption. Review and a test for the affected backend were needed to establish that this case worked.

What this example shows

  1. 25 August: first changes-requested review.
  2. 26 August: follow-up changes-requested review identified the Trio issue after the earlier repairs.
  3. Trio repair revision, with the scoped explanation in the linked author reply.
  4. 27 August: maintainer approval by @ransomr, followed by merge on 27 August 2026.

The reported test run had two failures. The author's final public report listed 9,965 passes, 4,347 skips and 2 failures, with 1,087 warnings. It attributed the two failures to unchanged file-URL paths containing spaces and reported that they passed in an identical copy without spaces. Those are author-reported results, not an independent rerun for this article.

AI assistance: OpenAI Codex assisted implementation, review and validation. The PR states that the author reviewed the final diff and results before publication. Maintainer review comments disclose AI generation followed by maintainer review before posting.

This public record shows one contribution by Mike Parsons (@TheDarkniteFalls), a repair cycle and maintainer acceptance. It does not establish speed, productivity, general capability or universal reliability. Public source records were checked on 2 October 2026; no S3 operation or test suite was rerun for this walkthrough.