openai: gpt-5.6-sol WebSocket inbound queue overflows #49523

Description

GPT-5.6 Sol intermittently fills OpenCode's inbound Responses WebSocket queue. The TUI shows:

Retry due · attempt 2 · WebSocket inbound queue overflow

The current turn recovered on retry. The same machine previously recorded the identical error as a terminal Failed to drain Session, so this can also fail the whole turn.

The background service and API were healthy. OpenCode v2.0.5 creates a bounded 128-frame queue, then raises queue-overflow when another frame arrives: https://github.com/anomalyco/opencode/blob/v2.0.5/packages/ai/src/route/transport/websocket.ts#L212-L254

The current v2 branch has the same file byte-for-byte. Existing tests correctly require poisoning rather than silently dropping frames, but an ordinary provider stream should not reach this internal guard. Temporary consumer lag should use safe backpressure, larger/batched buffering, or recovery that does not terminate the turn.

A repository search found no matching bug report. #42572 concerns oversized outbound requests/code 1009; #48690 concerns xAI close code 1006. Neither covers inbound queue exhaustion.

Relevant prior server log, with paths and session ID redacted:

timestamp=2026-09-11T10:23:38.384Z level=ERROR run=a062b3ef
message="Failed to drain Session"
cause="AI.Error: WebSocket inbound queue overflow"
[cause]: AI.Error.Transport: WebSocket inbound queue overflow
role=server sessionID=ses_…

Plugins

github:0x4nur4g/opencode-v2-model-discovery (no project-local plugins)

OpenCode version

2.0.5, latest channel

Steps to reproduce

1. Use the TUI against the shared background service.
2. Select openai/gpt-5.6-sol, variant max.
3. Send a prompt. The failure is intermittent.
4. Observe Retry due · attempt 2 · WebSocket inbound queue overflow.

Observed twice locally: the current retrying turn and a previous terminal drain failure on 2026-09-11.

Screenshot and/or share link

No public share link; session contains private workspace context. Exact error and redacted server log are above.

Operating System

Ubuntu 24.04.2, Linux 7.0.0-29-generic x86_64

Terminal

TERM=xterm-256color, COLORTERM=truecolor, shell /bin/zsh; terminal application unavailable.