[Bug] Streaming requests to opencode.ai hang with HTTP/2 SSE (200s timeout → 502/499, Codex stuck on 'thinking')

[flyinsz]

Client or integration

• Codex CLI
• Direct HTTP/API client (curl)

Area

• Proxy and routing
• Streaming

Summary

Requests proxied to opencode.ai (/zen/go/v1) hang forever in streaming mode (stream: true). The proxy waits the full 200s timeout, then reports connection reset / 502 upstream_server_error / 499 client_closed_request. On the client side (Codex CLI) the UI just shows "thinking" indefinitely.

This is not a proxy/DNS/network issue on the user's machine — all direct connections work fine. It is a protocol-level incompatibility between Bun's HTTP/2 fetch and the Cloudflare edge in front of opencode.ai for SSE streaming responses.

Reproduction

Same endpoint, same payload, only the HTTP version differs:

# HTTP/1.1 + stream=true  → WORKS (SSE flows, ~3s)
curl --http1.1 -N https://opencode.ai/zen/go/v1/chat/completions \
  -H "Authorization: Bearer <key>" -H "Content-Type: application/json" \
  -d '{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"hi"}],"max_tokens":5,"stream":true}'
# → HTTP 200, SSE chunks received

# HTTP/2 + stream=true   → HANGS (no bytes at all, times out)
curl --http2 -N https://opencode.ai/zen/go/v1/chat/completions \
  -H "Authorization: Bearer <key>" -H "Content-Type: application/json" \
  -d '{"model":"deepseek-v4-flash","messages":[{"role":"user","content":"hi"}],"max_tokens":5,"stream":true}'
# → 0 bytes until client timeout (20s+)

# Bun fetch + stream=true (what opencodex actually does) → HANGS
# Bun's fetch negotiates HTTP/2 by default with this origin.

Non-streaming (stream: false) works over both HTTP/1.1 and HTTP/2 (~2s).

opencodex forwards all chat completions with stream: true (confirmed via ocx debug provider logs):

[ocx:openai-chat:request] {"host":"opencode.ai","model":"deepseek-v4-flash","stream":true,...}

Version

2.15.0 (@bitkyc08/opencodex, bundled Bun 1.3.14, node_modules/bun/bin/bun.exe)

Operating system

macOS (darwin)

Provider and model

opencode.ai (opencode-go → https://opencode.ai/zen/go/v1, adapter openai-chat) / deepseek-v4-flash; Codex runtime: codex 0.147.0-alpha.6.5 (ChatGPT.app); outbound: direct connection (NO_PROXY set, no proxy vars).

Logs or error output

• service.log: repeated [upstream-retry] connection reset (opencode.ai) — retrying (2/3)
• usage.jsonl (recent, ~100 requests): status=502 durationMs≈200000 errorCode=upstream_server_error and status=499 closeReason=client_cancel (client abandons after ~90–160s)
• Provider model discovery (GET /models) succeeds; only the streaming POST hangs.

Redacted configuration

{
  "provider": "opencode-go",
  "baseURL": "https://opencode.ai/zen/go/v1",
  "adapter": "openai-chat",
  "model": "deepseek-v4-flash"
}

Expected behavior

Streaming responses from opencode.ai should work over whatever HTTP version Bun negotiates. Either:

1. opencodex should force HTTP/1.1 for SSE upstreams (Bun fetch supports protocol: "http1.1"/"h1"), or
2. expose a config option to force HTTP/1.1 per provider, or
3. investigate whether opencode.ai's Cloudflare edge is misbehaving with HTTP/2 SSE.

Notes

• Verified the opencodex process connects directly to 172.65.90.20:443 (opencode.ai real IP, Cloudflare range) — no system/HTTP proxy involved. macOS system proxy (FlClash :7890) was ruled out via lsof and side-by-side tests.
• Reproducible with both opencode-zen and opencode-go (same origin opencode.ai).
• Worth checking if other Cloudflare-fronted SSE providers are affected by Bun's HTTP/2 fetch too.

Checks

• I searched existing issues and documentation.
• I removed secrets, tokens, account details, request credentials, and personal data.

[coderabbitai]

🔗 Related PRs

#749 - fix(responses): reject expired forward continuations [merged]
#966 - fix(codex): keep pre-connection DNS/network failures off account health (#914) [open]
#1006 - fix(deepseek): apply bounded JSON policy on HTTP SSE for Flash [open]
#1487 - perf: route ChatGPT Codex upstream turns over responses_websockets [open]
#1558 - perf: route ChatGPT Codex upstream turns over responses_websockets [merged]

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[github-actions]

Issue reopened

The report now contains the information required by the automated check. Thanks for updating it.