bug: an object-store 404 with an empty reason phrase makes a missing transcript a 502 instead of a 404 #4984

Provide environment information

Not environment-specific: found in the webapp source at main @ c2b7a72 and reproduced with the webapp's own Vitest suite (macOS arm64, pnpm).

Describe the bug

A missing transcript can return 502 instead of 404 when the object store's 404 response has an empty reason phrase.

• Aws4FetchClient.getObjectResponse (apps/webapp/app/v3/objectStoreClient.server.ts:135-141) throws an error built only from response.statusText and discards response.status:

  throw new Error(`Failed to download from object store: ${response.statusText}`);

• isTranscriptNotFound (apps/webapp/app/services/realtime/transcriptDownload.server.ts:46-54) recognizes this adapter's missing object only by matching the message against /^Failed to download(?: range)? from object store: Not Found$/.

A valid HTTP/1.1 404 with no reason phrase gives the message Failed to download from object store: . It isn't classified as not found, so the route answers with a download failure (502).

Expected: a 404 from the object store is recognized by its status code, whatever the reason phrase says.

Reproduction repo

N/A (test against this repo, below)

To reproduce

In transcriptDownload.server.test.ts, start a local TCP server that replies HTTP/1.1 404 \r\nContent-Length: 0\r\n\r\n. Point ObjectStoreClient.create({ baseUrl: "http://127.0.0.1:<port>", service: "s3", ... }) at it, then:

await expect(client.getObjectResponse(key)).rejects.toSatisfy(isTranscriptNotFound);

On main this fails, because the error message is Failed to download from object store: and it isn't recognized.

Additional information

A fix with this regression test and a .server-changes note is ready locally:

• the thrown error carries status: 404;
• isTranscriptNotFound checks the status first.

The transcript suite (8 passed), oxfmt, oxlint and webapp typecheck pass. I'll open it as a draft PR with fixes #<this> once the account is vouched.

Prepared with AI assistance (Claude) from the breken-ai account.