# Omnigraph v0.4.0

Omnigraph v0.4.0 demotes the Run state machine to commit metadata via the
publisher's CAS, fixing a write-cancellation hole and reducing the engine's
surface area.

## Highlights

- **Direct-to-target writes**: `mutate_as` and `load` write
  directly to the target tables and call
  `ManifestBatchPublisher::publish` once at the end with
  `expected_table_versions`. No more `__run__<id>` staging branches, no
  more `RunRecord` state machine. Cross-table OCC is enforced inside the
  publisher's row-level CAS on `__manifest`.
- **Cancellation safety by construction**: a dropped mutation future
  leaves no graph-level state — only orphaned Lance fragments, reclaimed
  by `omnigraph cleanup`. The "zombie run" cascade documented in
  `.context/zombie-run-investigation.md` is gone.
- **Read-your-writes inside multi-statement mutations**: a `.gq` query
  that inserts and then references a row in the same statement now sees
  its own writes via an in-process `MutationStaging` cache, even though
  no manifest commit happens between ops.
- **Structured conflict surface**: concurrent writers race through the
  publisher's CAS; the loser surfaces as
  `ManifestConflictDetails::ExpectedVersionMismatch { table_key,
  expected, actual }`. The HTTP server maps this to **409 Conflict** with
  a structured `manifest_conflict` body so clients can detect-and-retry
  without parsing the message.

## Removed

This is a breaking release. Pre-0.4.0 / no SLA.

- `omnigraph::db::{RunRecord, RunStatus, RunId}` types and the
  `_graph_runs.lance` / `_graph_run_actors.lance` Lance datasets.
- Engine APIs `begin_run`, `begin_run_as`, `publish_run`,
  `publish_run_as`, `abort_run`, `fail_run`, `terminate_run`,
  `list_runs`, `get_run`.
- HTTP endpoints: `GET /runs`, `GET /runs/{run_id}`, `POST
  /runs/{run_id}/publish`, `POST /runs/{run_id}/abort`. The
  `RunListOutput` and `RunOutput` schemas are removed from the OpenAPI
  document.
- CLI subcommands: `omnigraph run list`, `omnigraph run show`, `omnigraph
  run publish`, `omnigraph run abort`. Use `omnigraph commit list`
  reading the commit graph for audit history.
- Cedar policy actions `run_publish` and `run_abort`. Existing
  `policy.yaml` files referencing these actions will fail validation —
  remove the rules; the `change` action covers the equivalent gating.

## Behavior changes

- `mutate_as` / `load` are now **atomic per query, single publish at the
  end**. A failed mutation leaves the target unchanged with no
  intermediate manifest commits.
- The `OmniError::manifest_conflict` shape produced by concurrent
  writers is now `ExpectedVersionMismatch` (was `MergeConflict::DivergentUpdate`
  via the run merge path). Clients that match on the conflict body must
  switch to inspecting `manifest_conflict.table_key/expected/actual`.

## Known limitation

A multi-statement mutation that writes a Lance fragment in op-N and then
fails in op-N+1 leaves the touched table with Lance HEAD ahead of the
manifest. The next mutation against that table fails with
`ExpectedVersionMismatch`. Most validation runs before any Lance write,
so single-statement mutations are unaffected; the narrow path is
multi-statement queries with late-op failures. Tracked as a follow-up;
see [docs/dev/writes.md](../dev/writes.md#mid-query-partial-failure-closed-by-mr-794)
for the workaround.

## Upgrade notes

- **Stale `__run__*` branches and `_graph_runs.lance`** in legacy v0.3.x
  repos are *inert* — the engine no longer reads them — but they remain
  on disk until production cleanup. This release deliberately does not touch
  legacy bytes.
- The `is_internal_run_branch` predicate is kept as a defense-in-depth
  guard against users naming a branch `__run__*`. It will be removed in
  a follow-up cleanup.
- External scripts hitting `/runs/*` will now receive 404. Migrate them
  to `/commits` for audit history; mutation status is implied by the
  HTTP response on `/change` itself.

## Included Changes

- Demote Run: write directly to target via publisher
- `ManifestBatchPublisher::publish` accepts per-table
  `expected_table_versions`
