[FEATURE]: Improve ACP output to mimic Junie or other native agents

[nesl247]

Feature hasn't been suggested before.

• [x] I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

JetBrains just announced ACP support is available today (https://blog.jetbrains.com/ai/2025/12/bring-your-own-ai-agent-to-jetbrains-ides/). With this we can start using opencode in the AI chat. However, the output is really not great.

As you can see the command is hidden, and then the output of the command isn't being shown in the pretty box. I'm assuming this is caused by opencode and not a bug/limitation of the ACP support, but if that isn't the case I can always open an issue with JetBrains.

FYI they are listing a opencode as an example in their documentation which is what I used.

[github-actions[bot]]

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

• #4990: Output from agent is frequently hidden - similar issue where output is not displayed properly
• #4315: Memory stays unbounded: ACP session map + compacted tool outputs - ACP-specific output handling issues
• #546: Print formatted output rather than raw ANSI escape sequences - related to output formatting issues

Feel free to ignore if none of these address your specific case.

[rekram1-node]

Ill do some acp work soon, I haven't managed to get time to do a lot of updates since we launched it. Thanks for raising issue!