CLAUDE.md section ownership

Project-root CLAUDE.md is read by Claude Code as part of project context. Most teams want some of it to be hand-written and stable (project overview, conventions) and some of it to vary by active profile (a “dev” profile might want one set of agent instructions; a “ci” profile a different set).

C3P solves this with a managed block: a marker pair inside CLAUDE.md whose contents are owned by the active profile, while everything outside the markers is yours.

How it looks on disk

# My project

User-authored content lives here, untouched by C3P.

<!-- c3p:v1:begin -->
<!-- Managed block. Do not edit between markers — changes are overwritten on next `c3p use`. -->

…profile-managed content goes here…

<!-- c3p:v1:end -->

More user-authored content here, also untouched.

The bytes above and below the markers are exact-preserved on every swap. The bytes between the markers come from the active profile’s contributions to project-root CLAUDE.md.

How a profile contributes content

Place a CLAUDE.md file as a peer of profile.json:

.claude-profiles/
└── dev/
    ├── profile.json
    ├── CLAUDE.md          # ← profile-managed project-root content
    └── .claude/
        └── ...

On c3p use dev, the contents of that CLAUDE.md are spliced into the managed block of project-root CLAUDE.md.

If dev extends base and base also has a profile-root CLAUDE.md, both contribute — same layering rules as any other file (extends, includes).

What if no profile contributes?

If the active profile (and none of its contributors) supplies a profile-root CLAUDE.md, project-root CLAUDE.md is never opened, written, or stat’d by c3p use. Back-compat with non-CLAUDE.md profiles is byte-exact.

First-time setup

c3p init injects the marker pair into your project-root CLAUDE.md (or creates the file with just the markers, if absent). c3p validate checks that the markers are present when a profile is active.

If you remove the markers by accident, run c3p init again — it’s idempotent and will re-add them without touching your other content.

Migrating from earlier C3P versions

If you have profiles from before this feature shipped, see the cw6 migration guide.