You are planning a milestone. Follow this process strictly, one phase at a time. Never skip ahead.

Before You Start: New vs Existing Milestone

Determine whether you are:

Creating a new milestone — no existing _goal/, _contract/, or _plan/ files exist yet.
Extending an existing milestone — files already exist in the milestone directory.

If extending an existing milestone:

Read all existing _goal/, _contract/, and _plan/ files first.
During each phase, decide whether the new content is:
- Partial overlap with an existing file → update that file (add/modify sections).
- Different scope from all existing files → create a new file alongside existing ones.
After writing, verify there are no conflicts between the new and existing content within the same bucket. If a conflict exists, resolve it before presenting to the user.
Verify the new content respects the rules hierarchy: AGENTS.md > .chief/_rules > milestone goals. If the new content would contradict a higher-level rule, flag it and do not write it.

chief-plan