OpenCode Go: GPT-5.6 Luna truncates streaming tool-call responses

Description

Summary

GPT-5.6 Luna through the OpenCode Go provider fails when a request uses streaming together with tool definitions. The upstream stream emits response.created and then fails or terminates during a tool call. The same model works when the request is non-streaming/buffered.

Environment

• Provider: OpenCode Go
• Endpoint: https://opencode.ai/zen/go/v1
• Model: gpt-5.6-luna
• Client/proxy: OpenCodex 2.10.2
• OS: macOS
• Adapter: OpenAI-compatible chat adapter; same behavior observed through a Responses adapter

Reproduction matrix

Request	Result
stream:false + tools	Works
stream:true + no tools	Works
stream:true + tools	Fails with HTTP 502 / truncated tool-call stream

Observed error: upstream stream ended mid tool call without a terminal signal — possible truncation

Expected behavior

A streaming tool request should produce a complete terminal tool-call event sequence, or return a normal structured API error.

Workaround

Buffer upstream (stream:false) and reframe the completed response as downstream SSE. This removes token-by-token output but allows the tool loop to complete.

Plugins

OpenCode Go provider (openai-chat adapter); OpenCodex 2.10.2

OpenCode version

OpenCode Go endpoint; OpenCodex 2.10.2 client/proxy

Steps to reproduce

1. Send a request to the OpenCode Go endpoint using model gpt-5.6-luna, at least one function tool, and streaming enabled.
2. Observe response.created, followed by HTTP 502 or stream termination during the tool call.
3. Repeat with stream:false + the same tool: it completes.
4. Repeat with streaming but no tools: it completes.

Screenshot and/or share link

No response

Operating System

macOS

Terminal

Codex Desktop integrated environment

Start at the OpenAI-compatible chat adapter and the Responses adapter entry points, then reproduce the listed matrix with GPT-5.6 Luna, tools, and streaming enabled. Trace where the stream ends after response.created and compare it with the buffered path. Done means complete terminal tool-call events or a normal structured API error instead of truncation or HTTP 502.