> ## Documentation Index
> Fetch the complete documentation index at: https://docs.obversa.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# How Do Two Agents Share One File?

> They do not. A stage names the files it may write, and parallel attempts run in separate worktrees.

They don't, by design. A writing stage names the files it may write, and
a file it changed that the workflow declared for another stage fails the
stage. Attempts that must not touch each other run in separate worktrees,
and only the winner lands. Obversa does not lock a file between two
processes you started outside a workflow, and a file the workflow never
declared is not part of the check.

## In Obversa

The write stage declares its two files, and nothing else is its to change:

```ts examples/teams/writer-reviewer-pair.ts (excerpt) {3} theme={null}
      stage('write', {
        agent: 'write',
        writes: ['src/add.mjs', 'test/add.test.mjs'],
        desc: 'Write the function and its test from the brief.',
        gate: 'The files named in the brief exist in the workspace.',
        retry: 1,
      }),
```

Declared writes are what the reviewer and the test stage read, and what
the record shows the stage produced.

## Workflow file

The declarations live in the workflow file, beside the roles and the
stages. [Should team rules live in AGENTS.md?](/glossary/workflow-file) says
what belongs there.

## Next steps

* [Workspace](/concepts/workspace): a worktree per writer, captured and verified.
* [Three candidates, one winner](/patterns/tournament): parallel attempts in their own worktrees.