How to use Claude to run parallel coding sessions
ChatML gives parallel Claude Code tasks separate Git worktrees, branches, and working directories. The team used the workflow for most of ChatML and reports merging over 750 generated pull requests.
news.ycombinator.com
Prompt to try
Editorial adaptation, not the source author’s exact prompt. Replace bracketed inputs and review tool permissions first.
Use ChatML to split [repository work] into [independent tasks]. Give each task its own Git worktree, branch, and Claude Code session. Run the tasks concurrently, then present each branch’s changes and verification results for review before integration.
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See placements →What happened
The team reports building most of ChatML with parallel agent sessions and merging over 750 pull requests generated through that workflow.
Reported by mcastilho on Hacker NewsHow the agent did it
- Chose Git worktrees to isolate agents that otherwise shared a filesystem directory.
- Built ChatML to assign each task a branch, directory, and Claude Code session.
- Used parallel sessions to build most of ChatML itself.
Where a person stepped in
The team merged generated pull requests and received bug and security feedback; the post does not describe specific review checks.
A person approved each step before the agent continued.
ChatML grew out of a problem its author encountered while using Claude Code: agents operating in the same working directory could interfere with one another's edits. Running concurrent tasks meant manually managing branches and directories. The author chose Git worktrees as the isolation mechanism and built a desktop application around them.
Each ChatML task receives its own branch and working directory, with a Claude Code session running through the Agent SDK. This allows tasks such as tests, feature work, and bug investigation to proceed in parallel within the same repository. The post presents that separation as the practical basis for avoiding agents stepping on each other's changes.
The team used this workflow to build most of ChatML itself and reported merging more than 750 pull requests generated through parallel agent sessions. The project is open source and focused on macOS. The author said Windows and Linux versions were running with some bugs and invited cross-platform contributions. The post does not describe the review process for those merged pull requests. Who it's for: developers coordinating multiple coding-agent tasks against a single repository who need separate working directories for concurrent edits.
Prompt
Suggested prompt (written by Agents In Use, not the author's)
Source: Hacker News · mcastilho
Frequently asked questions
How are parallel Claude Code tasks isolated?
Each task gets its own Git worktree, branch, and working directory. ChatML runs a Claude Code session through the Agent SDK for that task.
What evidence of using the workflow did the author report?
The team built most of ChatML using this workflow and merged over 750 pull requests generated through parallel agent sessions. The post does not specify the pull-request review process.
More details
Remaining steps
- Merged more than 750 pull requests generated through those sessions.
About this account
Multiple Claude Code sessions work concurrently in isolated worktrees, with each task receiving its own branch and directory.
Platform: Hacker News. Attribution: https://news.ycombinator.com/item?id=47303711. Prompt: Suggested (written by Agents In Use, not the author's). Sourced by the Agents In Use pipeline.
Credit: mcastilho on Hacker News
Source published 9 Mar 2026
Source checked 14 Oct 2026
Tools and topics
ChatML · Claude Code · Git worktrees · Agent SDK
Git worktrees · Parallel agents · Desktop app
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.