Reasoning is printed with a newline between each word using OpenCode w Copilot gpt 5.5

[viblo]

What version of HAPI is running?

0.17.4

What platform is your computer?

Linux 6.12.0-16000.8-default x86_64 unknown

What issue are you seeing?

Any time the agent prints out reasoning, its displayed with newlines between each step as shown in this screenshot:

What steps can reproduce the bug?

It happens for any task I ask it to do as long as some reasoning text comes back.

What is the expected behavior?

Not newlines between each word in the reasoning output.

Additional information

This was tried with OpenCode, using the Github Copilot GPT 5.5 model.

[github-actions]

Thanks for the report. I found the relevant OpenCode/ACP path in the codebase.

HAPI currently forwards every ACP agent_thought_chunk as its own reasoning message. The web timeline then turns each reasoning message into its own reasoning block, without coalescing adjacent chunks. So if OpenCode/Copilot GPT 5.5 emits reasoning as very small chunks (for example word-sized chunks), HAPI will preserve those chunk boundaries in the reasoning output. That matches the symptom shown here.

I did not find a coalescing/buffering step for OpenCode reasoning chunks in the current path.

Relevant code:

• cli/src/agent/backends/acp/AcpMessageHandler.ts:369 - handles ACP agent_thought_chunk updates.
• cli/src/agent/backends/acp/AcpMessageHandler.ts:385 - forwards each non-empty thought text chunk immediately as { type: 'reasoning', text: ... }.
• cli/src/agent/messageConverter.ts:27 - converts each reasoning message to the wire-level { type: 'reasoning', message, id } format.
• web/src/chat/reducerTimeline.ts:189 - converts each wire-level reasoning message into one agent reasoning content block.
• web/src/lib/assistant-runtime.ts:65 - renders each agent-reasoning block as an assistant reasoning message.
• cli/src/agent/backends/acp/AcpMessageHandler.test.ts:729 - test currently expects sequential thought chunks to remain separate reasoning messages.

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HAPI Bot