Claude Code Parallel Agents: How to Run Multiple Sessions at Once

Claude Code parallel agents refers to running multiple Claude Code sessions simultaneously, with each session working on a separate workstream. You open two windows, start two sessions, and both are making progress at the same time. This is distinct from the subagents that Claude Code can spawn internally during a complex task - those are automatic and happen within one session. Parallel agents is a deliberate choice you make when you have two things that can be built at the same time without getting in each other's way.

The value is compounded when you have independent tasks. If you need a new API route built and a new UI component built and neither depends on the other yet, there is no reason to wait. Run them in parallel and you finish both in the time it would have taken to finish one. The constraint is isolation - the two sessions cannot be editing the same files, or you will create conflicts that take longer to resolve than the time you saved.

The Fork Method is the decision framework I use before starting any multi-part build to figure out whether work should run in parallel or in sequence. The question is not just 'can these run at the same time?' - it is 'will they step on each other?' If the answer is no, fork. If yes, sequence.

Git worktrees are the infrastructure layer that makes Claude Code parallel agents safe and conflict-free. A worktree lets you check out a second branch of the same repository into a completely separate directory - so you have two copies of the codebase on disk at the same time, each on its own branch. You point one Claude Code session at the first directory and a second session at the second directory. They read and write completely independently.

To create a worktree, run 'git worktree add ../project-feature-b feature-b' from your main project directory. This creates a new directory called project-feature-b with the feature-b branch checked out. Open Claude Code there and start the second workstream. When both are done, merge the branches normally - any conflicts are real logical conflicts, not accidental file collisions from two sessions stepping on each other.

You can run two Claude Code sessions in the same working directory without worktrees, but it requires more discipline. Both sessions see the same files. If session A is building out a new module and session B is only working in a completely separate part of the codebase - different directories, different files - the risk is low and you can skip the worktree overhead. The rule is: if either session could plausibly touch a file the other is touching, use a worktree.

Where this pattern works cleanly without worktrees is tasks at different abstraction levels. Session A builds the backend endpoint. Session B writes the documentation and the README for a different feature entirely. They are never going to conflict because they are in different files. Session A owns the code, session B owns the markdown. No worktree needed, no collision risk.

Claude Code has a built-in mechanism for dispatching parallel work from within a single session: it can spawn subagents to handle concurrent tasks when it determines a problem can be parallelized. You do not need to manage this manually - Claude Code figures out when to use it. But you can encourage it by structuring your prompts to make the independence of tasks explicit.

If you tell Claude Code 'build these three components - they are independent of each other, none of them share a file', it will recognize that parallelism is available and may dispatch them as concurrent subtasks. The result comes back faster than if it had done them sequentially. This is different from the two-session Fork Method - it is parallelism within one session, managed by Claude Code itself, not by you opening multiple windows.

The merge step is where parallel sessions pay off or cost you. If you used worktrees and the tasks were genuinely independent, merging is clean - you merge two branches that never touched the same lines of code. If you did not use worktrees and there are conflicts, you work through them the same way you would any git merge: look at each conflict, decide which version wins or how to combine them, and commit the resolution.

One habit that makes the merge step easier is having each parallel session commit frequently with descriptive messages. When you are looking at a merge conflict, knowing that 'session A last committed auth middleware' and 'session B last committed the user list component' gives you immediate context for what each side of the conflict is trying to accomplish. Small commits are always good practice - in parallel session workflows they become essential.

The Fork Method is one part of the broader Claude Code workflow system taught inside the Claude Code Club. Members get the complete playbook for structuring multi-session builds, managing worktrees, and shipping faster without creating merge chaos.