Qwen/Qwen3.5-397B-A17B: system message must be at the beginning

[majestichou]

Description

I use superpower plugin and use opencode to link the Qwen/Qwen3.5-397B-A17B api.
Ask one question: "who are you"
Then an error happeded: "system message must be at the beginning"

Plugins

superpowers

OpenCode version

1.3.13

Steps to reproduce

1. use opencode to link the Qwen/Qwen3.5-397B-A17B api.
2. install superpowers plugin https://github.com/obra/superpowers
3. ask one question

Screenshot and/or share link

Ask one question: "who are you"
Then an error happeded: "system message must be at the beginning"

Operating System

ubuntu 24.04

Terminal

Tabby Terminal, MobaXterm

[github-actions]

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

• When using the qwen3.5-122b-a10b model (via nvidia provider), the following error is returned: System message must be at the beginning #16560: Same error "System message must be at the beginning" with Qwen3.5 models via a custom/third-party provider
• Multiple system prompts break Qwen3.5-* models #15059: "Multiple system prompts break Qwen3.5-* models" — the superpowers plugin likely adds an extra system prompt, which triggers this exact error in Qwen models that require system messages to appear only at the start of the conversation

[alienwaredream]

I am reporting a recurring issue where any Q&A attempt triggers the error:

"System message must be at the beginning."

This is happening in my current deployment using OpenCode v1.3.13 with the Qwen3.5-122B-A10B-FP8 model served via vLLM v0.19.0.

[alienwaredream]

I am reporting a recurring issue where any Q&A attempt triggers the error:

"System message must be at the beginning."

This is happening in my current deployment using OpenCode v1.3.13 with the Qwen3.5-122B-A10B-FP8 model served via vLLM v0.19.0.

Updating the superpower plugin to the latest version should resolve the "System message must be at the beginning" error and get everything back to normal.

[sgmihai]

Also seeing this with qwen3.6-35b via vllm, in opencode 1.4.6 with omo slim plugin.

[robertoberto]

same underlying bug as #15059. also fires with no plugins installed — opencode's title-generator path emits two role: "system" entries on its own (title-generator prompt + inherited delegation block) on the first call of any session against a Qwen 3.5+ deployment.

confirmed against Qwen/Qwen3.6-27B and Qwen/Qwen3.6-35B-A3B on vLLM v0.21.0 with opencode v1.14.39, vanilla install. the superpowers/opencode-dcp/llama-server reports are the same path made more visible by extra system fragments, not a separate bug.

diagnosis, fix snippet, and currently-open PR (#16981) tracked in #15059.