OpenAI gateway 503s uncompressed request bodies over ~1 MiB, byte-cliff tests show
esafak · ghdev · 2026-10-12
A new opencode issue tracks a diagnosed-but-unfixed OpenAI gateway bug: uncompressed request bodies over 1 MiB to api.openai.com/v1/responses deterministically fail with a 503 Envoy error, contradicting the documented 128 MiB limit.
- Byte-cliff test: an identical JSON payload succeeds at 1,048,575 bytes and 503s at 1,048,577 bytes; the same body succeeds when compressed.
- Failures start around 59-61% context usage; retries don't help (identical bytes are resent), only compaction temporarily recovers the session.
- The official Codex CLI is unaffected because it zstd-compresses requests by default.
- A same-signature issue in openai/codex was acknowledged by a maintainer as a server-side problem.
Likely a gateway bug OpenAI will fix, but enabling zstd compression is a free workaround.
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