# Stage: archive

## Purpose
Publish durable run/session state to object storage, then atomically advance remote current state.

## Inputs and Outputs
Inputs:
- session manifest and prerequisite stage records
- run root contents under `runs/{run_id}/`
- promotion rules with artifact `source` IDs and archive `dest` paths (`archive.promote_artifacts`)
- session-level `previous/**` cache files when present

Outputs:
- uploaded run files under `{session_prefix}/runs/{run_id}/...`
- uploaded promoted artifacts under `{session_prefix}/...`
- uploaded session previous-cache files under `{session_prefix}/previous/...` when present
- `{session_prefix}/current/manifest.json`
- `{session_prefix}/current/run_id.txt` written last

## Boundaries
Owns:
- Archive enable/disable gate behavior
- Prerequisite stage success enforcement
- Run file collection and upload (excluding `audio/`)
- Promotion rule resolution and upload
- Session previous-cache file collection/upload
- Commit pointer publish order

Does not own:
- Stage execution before archive
- Post-archive local cleanup policy execution (handled by app cleanup logic)

## Config Fields Used
- `pipeline.archive.enabled`
- `pipeline.archive.upload_run`
- `pipeline.archive.promote_artifacts`
- `pipeline.storage.s3.bucket`
- `pipeline.storage.s3.root_prefix`
- `pipeline.workspace.root`
- `session.campaign`
- `session.session_id`

## External Adapters Used
- Object storage backend (`env.ObjectStore`) for upload/list primitives.

## State and Manifest Behavior
- Requires `prepare`, `transcribe`, `merge`, `polish`, `normalize`, `trim`, and `analyze` status `succeeded`.
- Resolves bucket/prefix from manifest identity first, then config fallback.
- Uploads session `previous/**` files as durable session state when the local `previous/` directory exists.
- Writes metadata including:
  - upload counts/paths
  - `previous_files_uploaded` and `previous_uploaded_paths`
  - `current_manifest_key`
  - `current_run_id_key`
  - `current_pointer_written`
- On skipped archive path, returns metadata with `skipped=true` and pointer not written.

## Skip and Resume Behavior
- Stage may self-skip (metadata skip) when archive disabled or run upload disabled.
- Runner-level skip also applies for previously succeeded stage unless forced.

## Failure Behavior
- Fails on missing prerequisite success, missing object store when required, missing run root, missing required promotion source, upload failures, or pointer write failures.
- Pointer semantics are fail-safe: `current/run_id.txt` is not written if prior required uploads fail.

## Tests to Inspect Before Changing
- `internal/stage/archive_test.go`
- `internal/app/post_archive_cleanup_test.go`

## Architectural Invariants
- Run upload excludes `audio/` subtree.
- Session `previous/**` is archiveable durable input/provenance state, not run-local output.
- `current/manifest.json` uploads before `current/run_id.txt`.
- `current/run_id.txt` is the remote publish commit marker.