# Migration from legacy packs

This project is meant to replace legacy `.pck` or EterPack-style content
delivery gradually, not through a single risky cutover.

## Target state

- Linux builds produce `.m2p`
- the client loads `.m2p` first
- runtime master key delivery is required
- silent fallback to legacy packs is disabled in production

## Suggested migration phases

### Phase 1: parallel loader

- keep the legacy loader in the client
- add `.m2p` support beside it
- verify the new loader against real content sets
- keep fallback only in development if needed

### Phase 2: pipeline validation

- build `.m2p` from the same source tree as legacy packs
- run `verify` for every archive
- run `diff` between the source tree and `.m2p`
- compare in-game behavior between legacy and `.m2p`

### Phase 3: runtime delivery

- stop embedding a real content key in the client
- deliver the runtime key through launcher, environment, or mapping
- verify startup failure behavior when the runtime key is missing

### Phase 4: production cutover

- package only `.m2p` for release clients
- disable silent fallback to legacy packs
- remove stale pack generation from release CI
- keep extract/debug tools only for internal use

## Recommended checks

- duplicate normalized paths
- invalid relative paths
- case-collision problems on Windows
- decompression failures
- manifest signature failures
- key mismatch by `key_id`

## Practical migration loop

1. Pick one legacy pack group.
2. Rebuild it as `.m2p`.
3. Verify it.
4. Diff it against the source tree.
5. Boot the client with runtime keys.
6. Validate asset loads in logs and in-game.
7. Move to the next pack group.

## Risk notes

- Do not mix silent fallback with production security claims.
- Do not ship a client that accepts `.m2p` without runtime key enforcement.
- Do not keep real secret keys inside the repository.