[macOS v1.17.18] gpt-5.6-sol-fast/high repeatedly fails with reasoning part rs_*:0 not found

[li-keli]

Description

On macOS, a fresh OpenCode CLI session using OpenAI via Codex OAuth repeatedly aborts while streaming reasoning with:

reasoning part rs_<redacted>:0 not found

The session used openai/gpt-5.6-sol-fast with the high reasoning variant. The first failure occurred after approximately 52 reasoning/tool loops in an active session. Retrying the same turn three times produced the same error shape with a different rs_* ID each time.

This appears related to #33934 and #27987, but expands the affected environment from Windows/Desktop with gpt-5.5-fast/xhigh to macOS/CLI with gpt-5.6-sol-fast/high on the latest OpenCode release.

Plugins

No explicitly configured plugins.

OpenCode version

1.17.18

Steps to reproduce

1. Run OpenCode CLI on macOS and authenticate to OpenAI using Codex OAuth.
2. Select openai/gpt-5.6-sol-fast with reasoning variant high.
3. Start a fresh plan agent session with a codebase investigation that performs repeated reasoning and tool calls.
4. Allow the session to continue for many tool/reasoning loops. In this case it failed at approximately step 52.
5. Retry the failed turn. The stream aborts again with reasoning part rs_*:0 not found, using a new reasoning ID on each retry.

Sanitized log shape

stream providerID=openai modelID=gpt-5.6-sol-fast small=false agent=plan mode=primary
llm runtime selected llm.runtime=ai-sdk llm.provider=openai llm.model=gpt-5.6-sol-fast
process error="reasoning part rs_<redacted>:0 not found"

Expected behavior

OpenCode should reconcile repeated reasoning segments/start-end cycles for the same OpenAI Responses reasoning item, or safely tolerate an unmatched reasoning-end event without aborting the session.

Actual behavior

The assistant stream terminates with reasoning part rs_*:0 not found. Retrying does not recover the session.

Screenshot and/or share link

None.

Operating System

macOS 26.5.1, Darwin 25.5.0, arm64

Terminal

Ghostty

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [Windows/Desktop v1.17.11] OpenAI gpt-5.5-fast xhigh fails with reasoning part rs_*:0 not found #33934: Same error reasoning part rs_*:0 not found on Windows/Desktop with gpt-5.5-fast/xhigh — same root cause, different platform/model variant
• processor.ts: merge multiple reasoning-start/end cycles into one part #27987: Tracks merging multiple reasoning-start/end cycles into one part, which appears to be the underlying fix needed

You already referenced these in your report — this issue may be best tracked as a follow-up or environment confirmation on those threads rather than a separate issue. Please coordinate with maintainers there.

[LysanderdeJong]

Running into the same issue.

[cjmanca]

Happening to me on windows with just gpt-5.6-sol (non-fast), all reasoning variants I've tried. It'll sometimes go for a long time without doing it, and then encounter a specific chain of reasoning that causes it to happen, at which point it'll continue happening every time I try to make it continue that same session unless I change what it's thinking about.

Right now it's happening enough that I think I'll have to change to codex until it's fixed since it's continually interrupting sessions.

[dsbrgg]

having the same issue here as well

[Kidsunbo]

same issue as well