[opencode-go] deepseek-v4.1-flash: ~30% of API requests stall ~110s then fail with "unexpected EOF" before first token (tiny prompts included) #57270

Description

Description

I use OpenCode Go directly over HTTPS (no OpenCode client/CLI in the loop; a local gateway + raw curl). Since 2026-10-19 06:00 UTC, roughly 30% of requests to deepseek-v4.1-flash never receive response headers: they hang for ~105–115 s, then the connection is closed (unexpected EOF; curl reports HTTP 000). Retrying the identical request immediately usually succeeds in 2–4 s with a warm prompt cache. This also happens with a 46-token prompt, so it is not context/prefill. Once the first token arrives, streaming speed is normal (~200–230 tok/s).

Impact: agent sessions (40–60 sequential calls) take ~1 h instead of ~10–15 min; ~65% of total request time is spent in attempts that produce no output.

Gateway-log evidence (UTC; control = same gateway, DeepSeek official API):

Failure signature: request body written in <1 ms, then no bytes for ~109 s, then EOF, e.g.:

{"status":502,"ms":109288,
 "net":{"own":0.8,"asks":1,"reused":true,"send":0.2},
 "error":"Post \"https://opencode.ai/zen/go/v1/chat/completions\": unexpected EOF"}

Tracer IDs (request start time in UTC → the successful retry's response id right after the stall; no keys/user content included):

• 2026-10-19T06:32:00Z stalled 115.9 s → retry OK, response chatcmpl-4fc06046f0eb430099757544c1050fed
• 2026-10-19T06:39:57Z stalled 102.0 s → retry OK, response gw-a70a2abc01d3-4c4a05
• 2026-10-19T06:46:03Z stalled 104.5 s → retry OK, response gw-a697b26c5509-4caafa

Also observed: mid-stream EOF without finish_reason / [DONE] (39× connection lost mid-reply (unexpected EOF) across sessions) — likely related to #57033.

Not client-specific: reproduced with raw curl/python (no OpenCode client), with x-opencode-session set and an identifying User-Agent; SG / HK / US egress all affected; both /zen/go/v1/chat/completions (gateway default) and the documented /inference/go/openai/v1/chat/completions were tested (in a quiet window both were 20/20 fast — the failure is bursty/time-dependent).

Related: #36889 (intermittent outages / Cloudflare 524 family), #57055 (first-token latency scales with context), #57033 (streams end without finish_reason). Difference from #57055: tiny prompts are affected too, and failed attempts end in EOF after ~110 s rather than a slow first token.

Plugins

None. Not using the OpenCode client; direct HTTP calls to the OpenCode Go API (Go plan, model deepseek-v4.1-flash).

OpenCode version

N/A — no OpenCode client/CLI involved. Client is a local gateway (Magpie 0.1.1290) plus raw curl on macOS.

Steps to reproduce

1. Use a Go-plan API key and run the loop below (tiny prompt, fresh x-opencode-session per request, max_tokens: 8) ~20 times during a busy period.
2. Healthy responses: 2–4 s. Affected responses: no bytes for ~105–115 s, then HTTP 000 / unexpected EOF.
3. Re-run any stalled request immediately: it normally succeeds in 2–4 s.

for i in $(seq 1 20); do
  curl -sS -m 130 -o /dev/null \
    -w "%{http_code} ttfb=%{time_starttransfer} total=%{time_total}\n" \
    -X POST https://opencode.ai/zen/go/v1/chat/completions \
    -H "Authorization: Bearer $OPENCODE_GO_KEY" \
    -H "Content-Type: application/json" \
    -H "User-Agent: my-coding-agent/1.0" \
    -H "x-opencode-session: my-agent-$(uuidgen)" \
    --data '{"model":"deepseek-v4.1-flash","messages":[{"role":"user","content":"Say ok"}],"max_tokens":8,"temperature":0}'
done

Note: as of 2026-10-20 03:40 UTC, 20/20 requests were fast on both endpoints; the issue is intermittent (worst observed hours: 63% and 70% failure).

Screenshot

Attached: opencode-go-evidence.png (summary + failure rate by UTC hour) and opencode-go-evidence.md (sanitized logs, more tracer IDs, cross-client tests).

Operating System

macOS 27.0.1 (26A434), arm64

Terminal

N/A — direct HTTP client (no terminal app; reproduction commands run via shell)

Plugins

No response

OpenCode version

No response

Steps to reproduce

No response

Screenshot

opencode-go-evidence.md

Operating System

No response

Terminal

No response