# ADR 0002: Project Lock Is Owned By AgentRun

## Status

Accepted.

## Context

The older model effectively made a long-lived teacher/project session hold the project lock. That breaks down once project groups become long-lived collaboration spaces and Claude is invoked on demand.

We need to prevent concurrent Claude executions from modifying the same project, while still allowing teachers to keep discussing the project in the group.

## Decision

Use a project-scoped lock whose owner is the current `AgentRun`.

```text
scope = project_id
owner = run_id
lifetime = one Claude processing task
```

The lock is acquired after `@Claude` creates an `AgentRun`, and released when the run completes, fails, times out or is canceled.

## Consequences

- Group membership, teacher identity and Claude provider session do not directly own the lock.
- The same long-lived `AgentSession` can be reused by many runs.
- `cancel current processing` releases the lock by `run_id`.
- Admin `force release` remains an exceptional operation for stuck runs or lost processes.