fix(relay): stream non-JSON upstream error bodies safely

[luvs01]

Motivation

• The deferred-request logging path previously called response.text() for any status >= 400, which buffers the entire upstream body and creates a DoS surface for large or never-ending non-JSON error responses.
• The intent is to capture useful diagnostics while avoiding unbounded memory/time consumption and still forward the full response to the client.

Description

• Stop using response.text() for all error statuses and restrict full-text inspection to application/json responses only by changing the JSON-branch guard to contentType.includes("application/json") and keeping JSON inspection unchanged.
• Add a streaming fallback for non-JSON error responses that forwards chunks to the client immediately while retaining only an in-memory prefix (8 KiB) for logging, implemented with getReader() and a ReadableStream wrapper.
• Introduce MAX_NON_JSON_ERROR_INSPECTION_BYTES = 8192 as the byte cap for retained diagnostic data and finalize logging on EOF, read error, or cancellation without buffering the whole body.
• Add regression tests in tests/request-log.test.ts that assert non-JSON error bodies stream the first chunk immediately and that oversized error bodies are preserved downstream while only a bounded prefix is logged.

Testing

• Ran bun run typecheck and it completed with no type errors.
• Ran focused tests with OCX_TEST_NO_QUEUE=1 bun run test -- tests/request-log.test.ts and the modified request-log suite passed (47 tests).
• Ran the full test harness (OCX_TEST_NO_QUEUE=1 bun run test) and observed the test run complete with tests passing in this run.
• Ran bun run privacy:scan which passed with no privacy issues detected.

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.
To continue using code reviews, add credits to your account and enable them for code reviews in your settings.

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Team

Run ID: 7b03125f-e0be-46ad-b864-1174d6e75a25

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

✅ Deterministic PR hygiene checks passed.

[github-actions]

✅ READY

• all PR quality gates passed.

Hygiene

✅ Deterministic PR hygiene checks passed.

[luvs01]

Consolidated into #177 as the single main work item. Its checklist now carries this proposal’s requirements and relevant unresolved review concerns. Closing this duplicate tracking item does not mean the combined implementation is finished. The branch and review history are retained.