MR-794 step 2: docs — runs/invariants/architecture/execution + cleanup

Refresh user-facing and agent-facing docs for the staged-write rewire
and clean up stale Run-state-machine references that survived MR-771.

MR-794-specific updates:
* docs/runs.md — remove "Known limitation: mid-query partial failure"
  section; document the in-memory accumulator + D₂ rule + the
  LoadMode::Overwrite residual.
* docs/invariants.md §VI.25 — flip from aspirational/open to
  upheld for inserts/updates. Within-query read-your-writes is now
  load-bearing for the publisher CAS contract.
* docs/architecture.md — add "Mutation atomicity — in-memory
  accumulator (MR-794)" subsection with per-op flow; refresh the
  engine + state diagrams to drop RunRegistry and add MutationStaging.
* docs/execution.md — rewrite the mutation flow sequence diagram
  for the staged-write path; updated the LoadMode table to call
  out per-mode commit semantics; rewrote load vs ingest.
* docs/query-language.md — document the D₂ parse-time rule.
* docs/errors.md — add the D₂ BadRequest rejection path.
* docs/testing.md — extend the runs.rs row to cover the new MR-794
  contract tests; add the staged_writes.rs row.
* docs/releases/v0.4.1.md (new) — release note covering the rewire,
  test additions, residuals, and files changed.
* AGENTS.md (CLAUDE.md symlink) — update the atomic-per-query
  description and the L2 capability matrix row.

Stale-reference cleanup (MR-771 leftovers):
* docs/storage.md — drop live _graph_runs.lance / _graph_run_actors.lance
  from the layout diagram and prose; mark legacy.
* docs/branches-commits.md — move __run__<id> to a legacy note;
  remove publish_run from the publish-trigger list.
* docs/audit.md — refresh _as API list (drop begin_run_as / publish_run_as);
  legacy RunRecord.actor_id moved to a historical note.
* docs/constants.md — mark run registry / branch-prefix rows as legacy.
* docs/cli.md — replace the legacy omnigraph run * quickstart block
  with omnigraph commit list/show.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -32,7 +32,7 @@ OmniGraph is a typed property-graph engine built as a coordination layer over ma
 - **Languages**: a `.pg` schema language and a `.gq` query language, both Pest-based, with a typed IR.
 - **Multi-modal querying**: vector ANN (`nearest`), full-text (`search`/`fuzzy`/`match_text`/`bm25`), Reciprocal Rank Fusion (`rrf`), and graph traversal (`Expand`, anti-join `not { … }`) in one runtime.
 - **Branches and commits across the whole graph**: Git-style — every successful publish appends to a commit DAG; merges are three-way at the row level.
-- **Atomic per-query writes**: `mutate_as` and `load` capture per-table `expected_table_versions` before writing and call `ManifestBatchPublisher::publish` once at the end. Cross-table OCC enforced inside the publisher's row-level CAS; no staging branches, no run state machine.
+- **Atomic per-query writes**: `mutate_as` and `load` accumulate insert/update batches into an in-memory `MutationStaging.pending` per touched table; one `stage_*` + `commit_staged` per table runs at end-of-query, then `ManifestBatchPublisher::publish` commits the manifest atomically with per-table `expected_table_versions` CAS. A mid-query failure leaves Lance HEAD untouched on staged tables — no drift, no run state machine, no staging branches. Deletes still inline-commit; D₂ at parse time prevents inserts/updates and deletes from coexisting in one query.
 - **HTTP server**: Axum + utoipa OpenAPI, bearer auth (SHA-256 hashed, optional AWS Secrets Manager), Cedar policy gating.
 - **CLI** driven by a single `omnigraph.yaml`; multi-format output (json/jsonl/csv/kv/table).
 
@@ -211,7 +211,7 @@ omnigraph policy explain --actor act-alice --action change --branch main
 | Query language | — | `.gq` + Pest grammar + IR + lowering + linter |
 | Schema migration planning | — | `plan_schema_migration` + `apply_schema` step types + `__schema_apply_lock__` |
 | Commit graph (DAG) across whole repo | — | `_graph_commits.lance` with linear + merge parents, ULID ids, actor map |
-| Per-query atomic writes | — | `MutationStaging` accumulator + `commit_with_expected` publisher CAS, single commit per `mutate_as` / `load` |
+| Per-query atomic writes | — | In-memory `MutationStaging.pending` accumulator + `stage_*` / `commit_staged` per touched table at end-of-query + publisher CAS via `commit_with_expected` (single manifest commit per `mutate_as` / `load`); D₂ parse-time rule keeps inserts/updates and deletes from mixing |
 | Three-way row-level merge | — | `OrderedTableCursor` + `StagedTableWriter`, structured `MergeConflictKind` |
 | Change feeds | — | `diff_between` / `diff_commits` with manifest fast path + ID streaming |
 | Cedar policy | — | 8 actions, branch / target_branch / protected scopes, validate/test/explain CLI |

docs/architecture.md

@@ -63,7 +63,7 @@ flowchart TB
     subgraph engine[omnigraph engine]
         plan[exec query and mutation]:::l2
         gi[graph index CSR/CSC<br/>RuntimeCache LRU 8]:::l2
-        coord[coordinator<br/>ManifestRepo · CommitGraph · RunRegistry]:::l2
+        coord[coordinator<br/>ManifestRepo · CommitGraph]:::l2
     end
 
     subgraph storage[storage trait — wraps Lance]
@@ -134,7 +134,7 @@ flowchart TB
         coord[GraphCoordinator]:::l2
         mr[ManifestRepo<br/>db/manifest.rs]:::l2
         cg[CommitGraph<br/>_graph_commits.lance]:::l2
-        rr[RunRegistry<br/>_graph_runs.lance]:::l2
+        stg[MutationStaging<br/>per-query in-memory accumulator<br/>exec/staging.rs]:::l2
     end
 
     subgraph idx[graph index]
@@ -149,17 +149,18 @@ flowchart TB
 
     eq --> gi
     eq --> ts
+    em --> stg
     em --> ts
+    ld --> stg
     ld --> ts
     eq --> mr
     em --> mr
     coord --> mr
     coord --> cg
-    coord --> rr
     ts --> st
 ```
 
-The engine binds the compiler IR to Lance. It owns multi-dataset coordination, the graph topology index, the run registry, and the snapshot/manifest read path.
+The engine binds the compiler IR to Lance. It owns multi-dataset coordination, the graph topology index, the per-query staging accumulator, and the snapshot/manifest read path.
 
 Code paths:
 
@@ -169,6 +170,46 @@ Code paths:
 - Graph index: `crates/omnigraph/src/graph_index/`
 - Loader: `Omnigraph::ingest` at `crates/omnigraph/src/loader/mod.rs:74`
 
+### Mutation atomicity — in-memory accumulator (MR-794)
+
+Inserts and updates inside `mutate_as` and the bulk loader's
+Append/Merge modes go through `MutationStaging`
+([`crates/omnigraph/src/exec/staging.rs`](../crates/omnigraph/src/exec/staging.rs)),
+a per-query in-memory accumulator. No Lance HEAD advance happens during
+op execution; one `stage_*` + `commit_staged` per touched table runs
+at end-of-query, then the publisher commits the manifest atomically.
+
+```
+op-1 (insert/update) → push RecordBatch → MutationStaging.pending[table]
+op-2 (insert/update) → read committed via Lance + pending via DataFusion
+                       MemTable (read-your-writes) → push batch
+op-N → push batch
+─── end of query ───────────────────────────────────────
+finalize: per pending table:
+   concat batches → stage_append OR stage_merge_insert → commit_staged
+publisher: ManifestBatchPublisher::publish (one cross-table CAS)
+```
+
+A failed op leaves Lance HEAD untouched on the staged tables: the next
+mutation proceeds normally with no drift to reconcile. Concrete
+contracts:
+
+- `D₂` parse-time rule: a query is either insert/update-only or
+  delete-only. Mixed → reject. Deletes still inline-commit (Lance
+  4.0.0 has no public two-phase delete); D₂ keeps the inline path safe.
+- `LoadMode::Overwrite` keeps the inline-commit path
+  (truncate-then-append doesn't fit the staged shape; overwrite has no
+  in-flight read-your-writes requirement).
+- Read sites consume `TableStore::scan_with_pending`, which Lance-scans
+  the committed snapshot at the captured `expected_version` and unions
+  with a DataFusion `MemTable` over the pending batches.
+
+This pattern realizes [docs/invariants.md §VI.25](invariants.md)
+(read-your-writes within a multi-statement mutation) and §VI.32
+(failure scope bounded) for inserts/updates by construction at the
+writer layer. See [docs/runs.md](runs.md) for the publisher CAS
+contract this builds on.
+
 ### Storage trait — today vs. roadmap
 
 ```mermaid
@@ -256,13 +297,13 @@ Throughout the docs, capabilities are split into:
 - **MVCC**: every Lance write bumps a per-dataset version; the OmniGraph manifest version coordinates which sub-table versions are visible together.
 - **Snapshot isolation**: a query holds one `Snapshot` for its lifetime; concurrent writes don't leak in.
 - **Cross-branch isolation**: copy-on-write means readers and writers on different branches don't block each other.
-- **Run isolation**: each transactional run lives on its own `__run__<id>` branch.
+- **Per-query staging**: `mutate_as` and `load` (Append/Merge) accumulate insert/update batches in an in-memory `MutationStaging`; one `stage_*` + `commit_staged` per touched table runs at end-of-query, then the publisher commits the manifest atomically. A mid-query failure leaves Lance HEAD untouched on staged tables. (MR-794; pre-v0.4.0 used a `__run__<id>` staging branch + Run state machine, removed in MR-771.)
 - **Schema-apply lock**: `__schema_apply_lock__` system branch serializes schema migrations.
 - **Fail-points** (`failpoints` cargo feature): `failpoints::maybe_fail("operation.step")?` in `branch_create`, publish, etc., for deterministic failure injection in tests.
 
 ## Workspace crates
 
 - `omnigraph-compiler` — schema and query grammars, catalog, IR, lowering, type checker, lint, migration planner, OpenAI-style embedding client.
-- `omnigraph` (engine, published as `omnigraph-engine` on crates.io since v0.2.2) — the Lance-backed runtime: manifest, commit graph, run registry, snapshot, exec, merge, loader, Gemini embedding client.
+- `omnigraph` (engine, published as `omnigraph-engine` on crates.io since v0.2.2) — the Lance-backed runtime: manifest, commit graph, snapshot, exec (incl. per-query `MutationStaging` accumulator), merge, loader, Gemini embedding client.
 - `omnigraph-cli` — the `omnigraph` binary.
 - `omnigraph-server` — the `omnigraph-server` binary (Axum HTTP server).

docs/audit.md

@@ -1,6 +1,7 @@
 # Audit / Actor tracking
 
 - `Omnigraph::audit_actor_id: Option<String>` is the actor in effect.
-- `_as` variants of every write API let callers override the actor: `begin_run_as`, `publish_run_as`, `ingest_as`, `mutate_as`, `branch_merge_as`, etc.
+- `_as` variants of every write API let callers override the actor: `mutate_as`, `ingest_as`, `branch_merge_as`, `apply_schema_as`, etc.
-- Actor IDs are persisted both on `RunRecord.actor_id` and on `GraphCommit.actor_id`, with optional split storage in `_graph_commit_actors.lance` and `_graph_run_actors.lance`.
+- Actor IDs are persisted on `GraphCommit.actor_id` with split storage in `_graph_commit_actors.lance` (the commit graph is split into `_graph_commits.lance` for the linkage and `_graph_commit_actors.lance` for the actor map).
 - HTTP server uses the bearer-token actor automatically; CLI uses the local user / explicit env (no implicit actor).
+- Pre-v0.4.0 repos also stored actor IDs on `RunRecord.actor_id` in `_graph_runs.lance` / `_graph_run_actors.lance`. The Run state machine was removed in MR-771; those files are inert post-v0.4.0 and reclaimed by MR-770's production sweep.

docs/branches-commits.md

@@ -37,7 +37,7 @@ Storage is split across two Lance datasets (both with stable row IDs):
 
 Notes:
 
-- Every successful publish (load / change / merge / schema_apply / publish_run) appends one commit.
+- Every successful publish (load / change / merge / schema_apply) appends one commit.
 - Merge commits have two parents; linear commits have one.
 - API: `list_commits(branch)`, `get_commit(id)`, `head_commit_id_for_branch(branch)`.
 
@@ -53,5 +53,5 @@ Notes:
 
 Filtered from `branch_list()` but visible to internals:
 
-- `__run__<run-id>` — ephemeral isolation branch for a transactional run.
 - `__schema_apply_lock__` — serializes schema migrations.
+- `__run__<run-id>` — legacy from the pre-v0.4.0 Run state machine (removed in MR-771). The branch-name guard predicate `is_internal_run_branch` is kept as defense-in-depth so users cannot create a branch matching the legacy prefix; the filter will be removed once production legacy branches are swept (MR-770).

docs/cli.md

@@ -56,12 +56,12 @@ omnigraph policy validate --config ./omnigraph.yaml
 omnigraph policy test --config ./omnigraph.yaml
 omnigraph policy explain --config ./omnigraph.yaml --actor act-alice --action read --branch main
 
-omnigraph run list ./repo.omni --json
+omnigraph commit list ./repo.omni --json
-omnigraph run show --uri ./repo.omni <run-id> --json
+omnigraph commit show --uri ./repo.omni <commit-id> --json
-omnigraph run publish --uri ./repo.omni <run-id> --json
-omnigraph run abort --uri ./repo.omni <run-id> --json
 ```
 
+(The legacy `omnigraph run list/show/publish/abort` subcommands were removed in MR-771; mutations and loads publish atomically and the commit graph (`omnigraph commit list`) is the audit surface.)
+
 `query lint` and `query check` are the same command surface. In v1, repo-backed
 lint uses local or `s3://` repo URIs; HTTP targets are only supported when you
 also pass `--schema`.

docs/constants.md

@@ -4,8 +4,8 @@
 |---|---|---|
 | `MANIFEST_DIR` | `__manifest` | `db/manifest/layout.rs` |
 | Commit graph dir | `_graph_commits.lance` | `db/commit_graph.rs` |
-| Run registry dir | `_graph_runs.lance` | `db/run_registry.rs` |
+| Run registry dir (legacy, removed MR-771) | `_graph_runs.lance` | inert post-v0.4.0; reclaimed by MR-770 |
-| Run branch prefix | `__run__` | `db/run_registry.rs` |
+| Run branch prefix (legacy, removed MR-771) | `__run__` | filtered by `is_internal_run_branch` defense-in-depth |
 | Schema apply lock | `__schema_apply_lock__` | `db/mod.rs` |
 | Manifest publisher retry budget | `PUBLISHER_RETRY_BUDGET = 5` | `db/manifest/publisher.rs` |
 | Internal manifest schema version | `INTERNAL_MANIFEST_SCHEMA_VERSION = 2` | `db/manifest/migrations.rs` |

docs/errors.md

@@ -9,6 +9,7 @@
 - `Manifest(ManifestError { kind: BadRequest|NotFound|Conflict|Internal, details: Option<ManifestConflictDetails>, … })`
   - `ManifestConflictDetails::ExpectedVersionMismatch { table_key, expected, actual }` — caller's `expected_table_versions` did not match the manifest's current latest non-tombstoned version (set by `OmniError::manifest_expected_version_mismatch`).
   - `ManifestConflictDetails::RowLevelCasContention` — Lance row-level CAS rejected the publish because a concurrent writer landed the same `object_id`. Retried internally by the publisher; only surfaces if the retry budget exhausts.
+  - **D₂ parse-time rejection** (MR-794): a single mutation query that mixes inserts/updates with deletes errors out *before any I/O* with kind `BadRequest`. Message: `mutation '<name>' on the same query mixes inserts/updates and deletes; split into separate mutations: (1) inserts and updates, then (2) deletes`. See [docs/query-language.md](query-language.md) for the rule and [docs/runs.md](runs.md) for the underlying staged-write rationale.
 - `MergeConflicts(Vec<MergeConflict>)`
 
 Compiler-side `NanoError` covers parse / catalog / type / storage / plan / execution / arrow / lance / IO / manifest / unique-constraint, each with structured spans (`SourceSpan { start, end }`) for ariadne-style diagnostics.

docs/execution.md

@@ -79,13 +79,16 @@ Hybrid example: `order { rrf(nearest($d.embedding, $q), bm25($d.body, $q_text))
 
 ## Mutation execution (`exec/mutation.rs`)
 
-Resolves expression values to literals, converts to typed Arrow arrays (`literal_to_typed_array(lit, DataType, num_rows)`), then writes:
+Resolves expression values to literals, converts to typed Arrow arrays (`literal_to_typed_array(lit, DataType, num_rows)`), then writes via Lance's two-phase distributed-write API at end-of-query:
 
-- `insert` → Lance `WriteMode::Append`
+- `insert` (no `@key`, edges) → accumulate into `MutationStaging.pending` (Append mode); finalize calls `stage_append` once per touched table.
-- `update` → Lance `merge_insert(WhenMatched::Update)`
+- `insert` (`@key` node) → accumulate into `pending` (Merge mode); finalize calls `stage_merge_insert` once per touched table.
-- `delete` → Lance `merge_insert(WhenMatched::Delete)` (logical) or filtered overwrite.
+- `update` → scan committed via Lance + pending via DataFusion `MemTable` (read-your-writes), apply assignments, accumulate into `pending` (Merge mode).
+- `delete` → still inline-commits via `delete_where` (Lance 4.0.0 has no public two-phase delete); recorded into `MutationStaging.inline_committed`.
 
-Multi-statement mutations are atomic at the manifest commit boundary.
+**D₂ parse-time rule.** A single mutation query is either insert/update-only or delete-only. Mixed → reject before any I/O. The check fires in `enforce_no_mixed_destructive_constructive(&ir)` inside `execute_named_mutation`.
+
+Multi-statement mutations are atomic at the publisher commit boundary: every insert/update batch lives in memory until end-of-query, then exactly one `stage_*` + `commit_staged` runs per touched table, then `ManifestBatchPublisher::publish` commits the manifest atomically with per-table `expected_table_versions` CAS.
 
 ### Mutation flow — sequence
 
@@ -93,57 +96,58 @@ Multi-statement mutations are atomic at the manifest commit boundary.
 sequenceDiagram
     autonumber
     participant client as Client
-    participant og as Omnigraph::mutate<br/>(mutation.rs:511)
+    participant og as Omnigraph::mutate_as<br/>(mutation.rs)
     participant cmp as omnigraph-compiler
-    participant runs as RunRegistry
+    participant stg as MutationStaging<br/>(exec/staging.rs)
     participant ts as table_store
     participant lance as Lance dataset
-    participant mr as ManifestRepo<br/>(manifest.rs:280)
+    participant pub as ManifestBatchPublisher
 
-    client->>og: mutate(target, source, name, params)
+    client->>og: mutate_as(branch, source, name, params, actor_id)
-    og->>cmp: parse + typecheck_query
+    og->>cmp: parse + typecheck + lower_mutation_query
-    cmp-->>og: CheckedQuery (Mutation IR)
+    cmp-->>og: MutationIR
-    og->>runs: begin_run(target, op_hash)<br/>fork __run__<id> from target head
+    og->>og: enforce_no_mixed_destructive_constructive (D₂)
-    runs-->>og: RunRecord
+    loop for each mutation op
-    loop for each mutation statement (on __run__<id>)
+        og->>og: resolve literals + build batch
-        og->>og: resolve expression literals<br/>literal_to_typed_array(lit, type, n)
+        alt insert / update (accumulate)
-        alt insert
+            og->>ts: open dataset @ pre-write version (first touch)
-            og->>ts: append RecordBatches
+            og->>stg: ensure_path + append_batch (PendingMode)
-            ts->>lance: WriteMode::Append → new fragment(s)
+            opt update — scan committed + pending
-        else update
+                og->>ts: scan_with_pending (Lance + DataFusion MemTable union)
-            og->>ts: merge_insert keyed by id
+                ts-->>og: matched batches
-            ts->>lance: merge_insert(WhenMatched::Update)
+            end
-        else delete
+        else delete (inline-commit, D₂ keeps separate)
-            og->>ts: merge_insert with delete predicate
+            og->>ts: delete_where (advances Lance HEAD)
-            ts->>lance: merge_insert(WhenMatched::Delete)
+            og->>stg: record_inline (SubTableUpdate)
         end
-        lance-->>ts: new dataset version
-        og->>mr: commit_updates(SubTableUpdate)<br/>per-statement commit on __run__<id>
-        mr-->>og: ack
     end
-    og->>og: OCC: target head unchanged since begin_run?
+    og->>stg: finalize(db, branch)
-    og->>og: publish_run(run_id)
+    loop per pending table
-    alt fast path (target hasn't moved)
+        stg->>ts: stage_append OR stage_merge_insert (one per table)
-        og->>mr: commit_updates_on_branch(target, updates)<br/>promote run snapshot
+        ts-->>stg: StagedWrite (transaction + fragments)
-    else merge path (target advanced)
+        stg->>ts: commit_staged (advances Lance HEAD)
-        og->>og: branch_merge_internal(__run__<id>, target)<br/>three-way merge
+        ts-->>stg: new Dataset
     end
-    mr-->>og: new target snapshot
+    stg-->>og: (updates: Vec<SubTableUpdate>, expected_versions)
-    og->>runs: terminate_run(Published)
+    og->>pub: commit_updates_on_branch_with_expected
+    pub->>pub: publisher CAS (cross-table OCC on __manifest)
+    pub-->>og: new manifest version
     og-->>client: MutationResult
 ```
 
 **Code paths:**
 
-- Entry: `Omnigraph::mutate` at `crates/omnigraph/src/exec/mutation.rs:511`
+- Entry: `Omnigraph::mutate_as` at `crates/omnigraph/src/exec/mutation.rs`
-- Per-mutation orchestration: `mutate_with_current_actor` at `crates/omnigraph/src/exec/mutation.rs:539`
+- Per-mutation orchestration: `mutate_with_current_actor` at `crates/omnigraph/src/exec/mutation.rs`
-- Per-statement commit on the run-branch: `commit_updates` (called from `execute_insert` / `execute_update` / `execute_delete` in `crates/omnigraph/src/exec/mutation.rs`)
+- D₂ check: `enforce_no_mixed_destructive_constructive` (in the same file)
-- Run publish: `Omnigraph::publish_run` at `crates/omnigraph/src/db/omnigraph.rs:858`
+- Per-op execution: `execute_insert`, `execute_update`, `execute_delete_node`, `execute_delete_edge`
-- Manifest commit primitive: `ManifestRepo::commit` at `crates/omnigraph/src/db/manifest.rs:280` (called from both per-statement `commit_updates` and the publish path)
+- Pending-aware reads: `TableStore::scan_with_pending` / `count_rows_with_pending` at `crates/omnigraph/src/table_store.rs`
+- Edge cardinality with pending: `validate_edge_cardinality_with_pending` at `crates/omnigraph/src/exec/mutation.rs`
+- Per-query accumulator: `crates/omnigraph/src/exec/staging.rs` (`MutationStaging`, `PendingTable`, `PendingMode`, `finalize`)
+- End-of-query Lance commit: `TableStore::stage_append`, `stage_merge_insert`, `commit_staged` at `crates/omnigraph/src/table_store.rs`
+- Manifest commit primitive: `commit_updates_on_branch_with_expected` at `crates/omnigraph/src/db/omnigraph/table_ops.rs`
 
-Multi-statement mutations don't get atomicity from a single final `commit` — they get it from the **run-branch + publish_run** pattern. By default a mutation forks a fresh `__run__<id>` branch (`begin_run`); each statement individually commits its sub-table updates to that run-branch. After all statements complete, an OCC pre-check verifies the target hasn't moved since the run started, then `publish_run` atomically promotes the run-branch into the target — either via the fast path (direct promotion if the target hasn't moved) or a three-way merge. That final publish is what gives multi-statement mutations their atomicity guarantee (per [`docs/invariants.md`](invariants.md) §VI.26). If anything fails mid-run, the run is failed and the run-branch is dropped without affecting the target.
+Atomicity guarantee for multi-statement mutations: a mid-query failure leaves Lance HEAD untouched on staged tables (no inline commit happened during op execution), so the next mutation proceeds normally with no `ExpectedVersionMismatch`. The publisher CAS at the very end either succeeds (manifest advances atomically across all touched sub-tables) or fails with a typed `ManifestConflictDetails::ExpectedVersionMismatch` (no partial publish). See [docs/invariants.md §VI.25 / §VI.32](invariants.md) and [docs/runs.md](runs.md).
-
-One exception: if the caller already targets a `__run__<id>` branch (mutation.rs:555), the mutation runs directly on that branch with no nested run wrapping — the assumption is the caller is managing the surrounding run lifecycle themselves. See [runs.md](runs.md) for the full run lifecycle.
 
 ## Bulk loader (`loader/mod.rs`)
 
@@ -156,19 +160,18 @@ One exception: if the caller already targets a `__run__<id>` branch (mutation.rs
 
 ## Load modes (`LoadMode`)
 
-| Mode | Semantics |
+| Mode | Semantics | Path (post-MR-794) |
-|---|---|
+|---|---|---|
-| `Overwrite` | Replace all data in the target tables on the branch |
+| `Overwrite` | Replace all data in the target tables on the branch | Inline-commit per type, then publisher CAS at end-of-load. Truncate-then-append doesn't fit the staged shape; documented residual. |
-| `Append` | Strict insert; duplicates error |
+| `Append` | Strict insert; duplicates error | In-memory `MutationStaging` accumulator; one `stage_append` + `commit_staged` per touched table at end-of-load; publisher CAS. |
-| `Merge` | Upsert by id (`merge_insert`) |
+| `Merge` | Upsert by `id` (`merge_insert`) | Same accumulator; one `stage_merge_insert` per touched table at end-of-load (Merge mode dedupes by `id`, last-write-wins); publisher CAS. |
+
+For Append/Merge, a mid-load failure (RI / cardinality violation, validation error) leaves Lance HEAD untouched on the staged tables — the next load on the same tables proceeds normally with no `ExpectedVersionMismatch`. For Overwrite, a mid-load failure can still leave Lance HEAD on a partially-truncated table; the next overwrite replaces it.
 
 ## `load` vs `ingest`
 
-- `load(branch, data, mode)` — direct load to a branch.
+- `load(branch, data, mode)` — direct load to a branch (single publisher commit per call).
-- `ingest(branch, from, data, mode)` — branch-creating, transactional load:
+- `ingest(branch, from, data, mode)` — branch-creating wrapper: if `branch` doesn't exist, fork it from `from` (default `main`) via `branch_create_from`, then call `load(branch, data, mode)`.
-  1. If target advanced since the run started, fork a fresh run branch from `from`.
-  2. Load into the run branch (Append).
-  3. If target hasn't moved, fast-publish; otherwise abort.
 - Returns `IngestResult { branch, base_branch, branch_created, mode, tables[] }`.
 - `ingest_as(actor_id)` records the actor on the resulting commit.
 

docs/invariants.md

@@ -110,7 +110,7 @@ Specific defaults (timeout values, memory caps, TTL windows) are *configuration*
     *Status: aspirational — referential integrity at scale requires SIP-backed cross-table validation; not yet implemented. Cross-batch / cross-version uniqueness tracked in MR-714.*
 
 25. **Isolation: per-query snapshot; read-your-writes within and across queries in a session.** Each query reads from one consistent manifest version. Within a multi-statement mutation, the read subplan inside each write operator sees the writes from earlier statements. Across queries in a session, reads always resolve the latest manifest version — no reader pinning to older snapshots.
-    *Status: open — read-your-writes within a multi-statement mutation requires Kuzu-style local-uncommitted scan path; deferred per MR-737 §10.10.*
+    *Status: upheld for inserts/updates after MR-794 step 2+ — `MutationStaging`'s in-memory accumulator + `TableStore::scan_with_pending` (DataFusion `MemTable` union with the committed Lance scan) implements read-your-writes within a multi-statement mutation. Delete-touching mutations are limited to delete-only by parse-time D₂; closing the within-query RYW gap for deletes requires Lance's two-phase delete API (tracked: MR-793 / Lance-upstream).*
 
 26. **Durability before acknowledgement.** Commit returns only after the substrate has confirmed durable persistence. No "fast" or "fire-and-forget" durability levels.
 

docs/query-language.md

@@ -64,6 +64,14 @@ Used inside MATCH or as expressions inside RETURN/ORDER:
 
 `<value>` is a literal, `$param`, or `now()`. Multi-statement mutations execute atomically (added in v0.2.0).
 
+### D₂ — mixed insert/update + delete is rejected at parse time
+
+A single mutation query must be **either insert/update-only or delete-only**. Mixed → rejected before any I/O with the message:
+
+> `mutation '<name>' on the same query mixes inserts/updates and deletes; split into separate mutations: (1) inserts and updates, then (2) deletes. This restriction lifts when Lance exposes a two-phase delete API (tracked: MR-793 / Lance-upstream).`
+
+Reason: under the staged-write rewire (MR-794), inserts and updates accumulate in memory and commit at end-of-query, while deletes still inline-commit (Lance 4.0.0 has no public two-phase delete). Mixing creates ordering hazards (same-row insert→delete becomes a no-op because the staged insert isn't visible to delete; cascading deletes of just-inserted edges break referential integrity by silent design). Until Lance exposes `DeleteJob::execute_uncommitted`, the parse-time rejection keeps both paths atomic and correct. See [docs/runs.md](runs.md) and [docs/invariants.md §VI.25](invariants.md).
+
 ## IR (Intermediate Representation)
 
 `QueryIR { name, params, pipeline: Vec<IROp>, return_exprs, order_by, limit }`

docs/releases/v0.4.1.md

@@ -0,0 +1,138 @@
+# Omnigraph v0.4.1
+
+Omnigraph v0.4.1 closes the multi-statement-mutation atomicity gap that
+v0.4.0 documented as a known limitation. Inserts and updates now route
+through an in-memory `MutationStaging` accumulator and commit via Lance's
+two-phase distributed-write API at end-of-query. A failed mid-query op
+no longer leaves Lance HEAD drifted on the touched table — the next
+mutation proceeds normally.
+
+## Highlights
+
+- **Staged-write rewire (MR-794)**: `mutate_as` and `load` (Append /
+  Merge modes) accumulate insert/update batches into
+  `MutationStaging.pending` per touched table. No Lance HEAD advance
+  happens during op execution; one `stage_*` + `commit_staged` per
+  table runs at end-of-query, then `ManifestBatchPublisher::publish`
+  commits the manifest atomically. A mid-query failure leaves Lance
+  HEAD untouched on staged tables.
+- **D₂ parse-time rule**: a single mutation query is either
+  insert/update-only or delete-only. Mixed → rejected with a clear
+  error directing the caller to split into two queries. Lance 4.0.0
+  has no public two-phase delete; deletes still inline-commit, and D₂
+  keeps that path safe.
+- **Read-your-writes via DataFusion `MemTable`**: read sites in
+  multi-statement mutations consume `TableStore::scan_with_pending`,
+  which Lance-scans the committed snapshot at the captured
+  `expected_version` and unions with a DataFusion `MemTable` over the
+  pending batches. Replaces the previous "reopen at staged Lance
+  version" pattern.
+- **Coordinator swap-restore eliminated** from `mutate_with_current_actor`.
+  Branch is threaded explicitly through the per-op execution path
+  (`execute_named_mutation`, `execute_insert`, `execute_update`,
+  `execute_delete*`, `validate_edge_insert_endpoints`,
+  `ensure_node_id_exists`). The `swap_coordinator_for_branch` /
+  `restore_coordinator` API and `CoordinatorRestoreGuard` are removed
+  from `mutation.rs`. (`merge.rs` keeps its own swap pattern; that's
+  a separate workflow tracked in MR-793.)
+- **`docs/invariants.md` §VI.25** flips from `aspirational/open` to
+  `upheld for inserts/updates`. The within-query read-your-writes
+  guarantee is now load-bearing for the publisher CAS contract.
+
+## Behavior changes
+
+- A failed multi-statement mutation no longer surfaces
+  `ExpectedVersionMismatch` on the *next* mutation against the same
+  table. The next call proceeds normally — Lance HEAD on staged
+  tables is unchanged.
+- Mixed insert/update + delete in one query is rejected at parse
+  time. Existing test queries that mixed both must be split.
+- `MutationStaging`'s shape changed: `pending: HashMap<String, PendingTable>`
+  + `inline_committed: HashMap<String, SubTableUpdate>` replaces the
+  previous `latest: HashMap<String, StagedTable>`. This is an internal
+  type; no public API impact.
+
+## Residual / out of scope
+
+- **`LoadMode::Overwrite`** keeps the legacy inline-commit path
+  (truncate-then-append doesn't fit the staged shape). A mid-overwrite
+  failure can still drift Lance HEAD on a partially-truncated table;
+  the next overwrite replaces it. Operator-driven, rare.
+- **Delete-only multi-statement mutations** still inline-commit per op.
+  D₂ keeps inserts/updates from coexisting with deletes, so the
+  inline path remains atomic per op but not per query for delete-only
+  cascades. Closing this requires Lance to expose
+  `DeleteJob::execute_uncommitted`; tracked in MR-793 / Lance-upstream.
+- **`schema_apply`, `branch_merge_internal`, `ensure_indices`** still
+  use Lance's inline-commit APIs. The two-phase pattern is in
+  `mutate_as` and `load` only; hoisting it to a storage-trait
+  invariant covering all writers is MR-793.
+
+## Tests added
+
+- `tests/runs.rs::partial_failure_leaves_target_queryable_and_unblocks_next_mutation`
+  (replaces the old `partial_failure_observably_rolls_back_but_blocks_next_mutation_on_same_table`)
+- `tests/runs.rs::mutation_rejects_mixed_insert_and_delete_at_parse_time`
+- `tests/runs.rs::mixed_insert_and_update_on_same_person_coalesces_to_one_merge`
+- `tests/runs.rs::multiple_appends_to_same_edge_coalesce_to_one_append`
+- `tests/runs.rs::multi_statement_inserts_publish_exactly_once`
+- `tests/runs.rs::load_with_bad_edge_reference_unblocks_next_load`
+- `tests/runs.rs::load_with_cardinality_violation_unblocks_next_load`
+
+## Files changed
+
+- `crates/omnigraph/src/exec/staging.rs` (NEW) — `MutationStaging`,
+  `PendingTable`, `PendingMode`, `StagedTablePath`,
+  `dedupe_merge_batches_by_id`.
+- `crates/omnigraph/src/exec/mutation.rs` — D₂ check; per-op
+  rewires (`execute_insert`, `execute_update`, `execute_delete*`);
+  branch threading; coordinator-swap removal; helper
+  `validate_edge_cardinality_with_pending`; helper
+  `concat_match_batches_to_schema`; `apply_assignments` updated to
+  copy unassigned blob columns from full-schema scans.
+- `crates/omnigraph/src/loader/mod.rs` — `load_jsonl_reader` split:
+  staged path for Append/Merge, legacy inline-commit path for
+  Overwrite. Helpers `collect_node_ids_with_pending` and
+  `validate_edge_cardinality_with_pending_loader`.
+- `crates/omnigraph/src/table_store.rs` — `scan_with_pending`,
+  `count_rows_with_pending` (DataFusion `MemTable`-backed union with
+  Lance scan).
+- `Cargo.toml` (workspace) + `crates/omnigraph/Cargo.toml` — added
+  `datafusion = "52"` direct dep (transitively pulled by Lance
+  already; required for `MemTable`).
+- `docs/runs.md` — removed "Known limitation" section; documented
+  the new accumulator + D₂ + LoadMode::Overwrite residual.
+- `docs/invariants.md` — §VI.25 status flipped to `upheld for
+  inserts/updates`.
+- `docs/architecture.md` — added "Mutation atomicity — in-memory
+  accumulator (MR-794)" subsection; refreshed the engine + state
+  diagrams to drop `RunRegistry` and add `MutationStaging`.
+- `docs/execution.md` — rewrote the mutation flow sequence diagram
+  for the staged-write path; updated the `LoadMode` table to call
+  out per-mode commit semantics; rewrote `load` vs `ingest`.
+- `docs/query-language.md` — documented the D₂ parse-time rule.
+- `docs/errors.md` — added the D₂ `BadRequest` rejection path.
+- `docs/storage.md` — dropped the live `_graph_runs.lance` reference
+  (legacy from MR-771) from the layout diagram and prose.
+- `docs/branches-commits.md` — moved `__run__<id>` to a legacy note;
+  removed `publish_run` from the publish-trigger list.
+- `docs/audit.md` — current `_as` API list refreshed; legacy
+  `RunRecord.actor_id` moved to a historical note.
+- `docs/constants.md` — marked the run registry / branch-prefix rows
+  as legacy.
+- `docs/cli.md` — replaced the legacy `omnigraph run *` quickstart
+  block with `omnigraph commit list/show`.
+- `docs/testing.md` — extended the `runs.rs` row to cover the new
+  MR-794 contract tests; added the `staged_writes.rs` row.
+- `AGENTS.md` (CLAUDE.md symlink) — updated the atomic-per-query
+  description and the L2 capability matrix row.
+
+## Included Changes
+
+- MR-794 step 2+ — rewire `mutate_as` and `load` via in-memory
+  `MutationStaging` + `stage_*` / `commit_staged` per touched table at
+  end-of-query.
+- (MR-794 step 1 shipped in v0.4.0's PR #67 — `StagedWrite`,
+  `stage_append`, `stage_merge_insert`, `commit_staged`,
+  `scan_with_staged`, `count_rows_with_staged` — and is the substrate
+  this release builds on.)

docs/runs.md

@@ -20,22 +20,60 @@ publisher's row-level CAS on `__manifest` is the single fence.
 
 A `.gq` query with multiple ops (e.g. `insert Person … insert Knows …`)
 must observe earlier ops' writes when validating later ops (referential
-integrity, edge cardinality). After demotion this is implemented via an
+integrity, edge cardinality). After MR-794 step 2+ this is implemented
-in-process `MutationStaging` accumulator in
+via an in-memory `MutationStaging` accumulator in
-`crates/omnigraph/src/exec/mutation.rs`:
+[`crates/omnigraph/src/exec/staging.rs`](../crates/omnigraph/src/exec/staging.rs),
+shared by both `mutate_as` and the bulk loader:
 
 - On the first touch of each table, the pre-write manifest version is
-  captured into `expected_versions[table_key]`.
+  captured into `expected_versions[table_key]` (the publisher's CAS
-- Subsequent ops on the same table re-open the dataset at the locally
+  fence at end-of-query).
-  staged Lance version (bypassing the manifest, which has not been
+- Each insert/update op pushes a `RecordBatch` into the per-table
-  committed yet) so they see prior writes.
+  pending accumulator. Lance HEAD does **not** advance during op
-- One `commit_with_expected(updates, expected_versions)` at the end
+  execution.
-  publishes the lot atomically. Cross-table conflicts surface as
+- Read sites (validation, predicate matching for `update`) consume
+  `TableStore::scan_with_pending`, which scans committed via Lance
+  and applies the same SQL filter to the pending batches via DataFusion
+  `MemTable`. Same-query writes are visible to subsequent reads.
+- At end-of-query, `MutationStaging::finalize` issues exactly one
+  `stage_*` + `commit_staged` per touched table (concatenating
+  accumulated batches; merge-mode dedupes by `id`, last-write-wins),
+  and the publisher publishes the manifest atomically across all
+  touched sub-tables. Cross-table conflicts surface as
   `ManifestConflictDetails::ExpectedVersionMismatch`.
+- **Deletes still inline-commit.** Lance's `Dataset::delete` is not
+  exposed as a two-phase op in 4.0.0; deletes go through `delete_where`
+  immediately and record their post-write state in
+  `MutationStaging.inline_committed`. The parse-time D₂ rule (below)
+  prevents inserts/updates from coexisting with deletes in one query,
+  so the inline path is safe for delete-only mutations.
 
 This upholds [docs/invariants.md §VI.23](invariants.md) (atomicity per
-query) and §VI.25 (read-your-writes within a multi-statement mutation —
+query) and §VI.25 (read-your-writes within a multi-statement mutation,
-previously aspirational, now upheld).
+upheld).
+
+### D₂ — parse-time mixed-mode rejection
+
+A single mutation query is either insert/update-only or delete-only.
+Mixed → rejected at parse time with a clear error directing the user to
+split the query. Reason: mixing creates ordering hazards
+(insert→delete on the same row would silently no-op because the staged
+insert isn't visible to delete; cascading deletes of just-inserted
+edges break referential integrity). Until Lance exposes a two-phase
+delete API, the parse-time rejection keeps both paths atomic and
+correct. Tracked: MR-793, plus a Lance-upstream ticket.
+
+### `LoadMode::Overwrite` residual
+
+The bulk loader's Append and Merge modes use the staged-write path
+described above. `LoadMode::Overwrite` keeps the legacy inline-commit
+path: truncate-then-append doesn't fit the staged shape cleanly in
+Lance 4.0.0, and overwrite has no in-flight read-your-writes
+requirement (the prior data is being wiped). A mid-overwrite failure
+can leave Lance HEAD on a partially-truncated table; the next overwrite
+will replace it. Operator-driven (rare in agent workloads); document
+permanently until Lance exposes `Operation::Overwrite { fragments }` as
+a two-phase op.
 
 ## Conflict shape
 
@@ -59,40 +97,32 @@ list`.
 `_graph_runs.lance` belongs in MR-770 (the production sweep) — this PR
 stops *creating* run state but does not destroy legacy bytes on disk.
 
-## Known limitation: mid-query partial failure on the same table
+## Mid-query partial failure: closed by MR-794
 
-A multi-statement `.gq` mutation where op-N writes a Lance fragment
+The pre-MR-794 design had a known limitation: a multi-statement `.gq`
-successfully and op-N+1 then fails leaves the touched table at
+mutation where op-N inline-committed a Lance fragment and op-N+1 then
-`Lance HEAD = manifest_version + 1`. The query is atomic at the manifest
+failed left the touched table at `Lance HEAD = manifest_version + 1`,
-level (the publisher never publishes, so reads at the pinned manifest
+blocking the next mutation with `ExpectedVersionMismatch`.
-version do *not* see op-N's data), but the *next* mutation against the
-same table fails loudly with
-`ManifestConflictDetails::ExpectedVersionMismatch` because
-`ensure_expected_version` enforces strict equality between Lance HEAD and
-the manifest's pinned version.
 
-**Why the engine doesn't auto-rollback**: Lance's `Dataset::restore()` is
+MR-794 (step 1 + step 2+) closed this for inserts/updates **by
-*not* a rewind — it appends a new commit (containing the desired
+construction at the writer layer**: insert and update batches accumulate
-historical version's data) and advances HEAD further. There is no Lance
+in memory; no Lance HEAD advance happens during op execution; one
-API to delete a committed version. A proper fix requires writing each
+`stage_*` + `commit_staged` per touched table runs at end-of-query, and
-mutation's per-table fragments to a *transient Lance branch* on the
+only after every op succeeded. A failed op leaves Lance HEAD untouched
-sub-table, then fast-forwarding main on success or dropping the branch
+on the staged tables, so the next mutation proceeds normally with no
-on failure. That work is tracked as a follow-up to MR-771; in the
+drift to reconcile.
-meantime:
 
-- **In practice this is rare.** Most schema-language validation
+The cancellation case (future drop mid-mutation) inherits the same
-  (`@key`, `@enum`, `@range`, intra-batch uniqueness, edge-endpoint
+guarantee — the in-memory accumulator evaporates with the dropped task
-  existence) runs *before* any Lance write inside the failing op, so
+and no Lance write was ever issued.
-  single-statement mutations never trip this. The narrow path is
-  multi-statement queries (`insert ... insert ...`,
-  `insert ... update ...`) where a late op fails on validation that
-  depends on earlier ops' staged data.
-- **Workaround**: callers that hit this should refresh the handle and
-  retry the mutation; if Lance HEAD remains drifted the
-  `omnigraph cleanup` command will GC the orphan version once a later
-  successful commit on the same table moves HEAD past it. (`cleanup`
-  cannot reclaim an orphan that *is* the current Lance HEAD; that case
-  needs the per-table-branch follow-up to fully heal.)
 
-The cancellation case (future drop mid-mutation) has the same shape and
+For delete-touching mutations the legacy inline-commit shape is
-the same workaround.
+preserved (Lance has no public two-phase delete in 4.0.0) — the same
+narrow window remains. The parse-time D₂ rule prevents inserts/updates
+from coexisting with deletes in one query, so a pure-delete failure
+cannot drift any staged-table state. If a delete-only multi-table
+mutation fails mid-cascade, the same workaround as before applies
+(retry; rely on `omnigraph cleanup` once a later successful commit
+moves HEAD past the orphan version). Closing this requires Lance to
+expose `DeleteJob::execute_uncommitted`; tracked in MR-793 and a
+Lance-upstream ticket.

docs/storage.md

@@ -22,7 +22,7 @@ OmniGraph is **not** a single Lance dataset; it is a *graph* of datasets coordin
   - `edges/{fnv1a64-hex(edge_type_name)}` — one Lance dataset per edge type
   - `__manifest/` — the catalog of all sub-tables and their published versions
   - `_graph_commits.lance` / `_graph_commit_actors.lance` — the commit graph and its actor map
-  - `_graph_runs.lance` / `_graph_run_actors.lance` — the run registry and its actor map
+  - (legacy `_graph_runs.lance` / `_graph_run_actors.lance` from pre-v0.4.0 repos are inert; the run state machine was removed in MR-771 and these files are cleaned up via MR-770's production sweep)
 - **Manifest row schema** (`object_id, object_type, location, metadata, base_objects, table_key, table_version, table_branch, row_count`):
   - `object_type` ∈ `table | table_version | table_tombstone`
   - `table_key` ∈ `node:<TypeName> | edge:<EdgeName>`
@@ -63,14 +63,12 @@ flowchart TB
     nodes["nodes/{fnv1a64-hex}/<br/>one dataset per node type"]:::l2
     edges["edges/{fnv1a64-hex}/<br/>one dataset per edge type"]:::l2
     cgraph["_graph_commits.lance/<br/>_graph_commit_actors.lance/"]:::l2
-    runs["_graph_runs.lance/<br/>_graph_run_actors.lance/"]:::l2
     refs["_refs/branches/{name}.json<br/>graph-level branches"]:::l2
 
     repo --> manifest
     repo --> nodes
     repo --> edges
     repo --> cgraph
-    repo --> runs
     repo --> refs
 
     subgraph dataset[Inside each Lance dataset — L1]
@@ -91,7 +89,7 @@ flowchart TB
 - **Repo root** is one directory (or S3 prefix). Everything below is part of one OmniGraph repo.
 - **`__manifest/`** is a Lance dataset whose rows describe which sub-table version is published at which graph-branch. Reading a snapshot starts here.
 - **`nodes/`** and **`edges/`** are sibling directories holding one Lance dataset per declared type. Names are `fnv1a64-hex` of the type name to keep paths fixed-length and case-safe.
-- **`_graph_commits.lance` / `_graph_runs.lance`** are L2 datasets that record the graph-level commit DAG and run registry respectively (each has a paired `*_actors.lance` for the actor map).
+- **`_graph_commits.lance`** is an L2 dataset that records the graph-level commit DAG, with a paired `_graph_commit_actors.lance` for the actor map. (Pre-v0.4.0 repos also have inert `_graph_runs.lance` / `_graph_run_actors.lance` from the removed Run state machine; MR-770 sweeps these in production.)
 - **`_refs/branches/{name}.json`** is graph-level branch metadata — pointers from a branch name to the manifest version it heads.
 - **Inside each Lance dataset** (orange): the standard Lance directory layout. `_versions/{n}.manifest` records every commit; `data/` holds the actual Arrow fragments; `_indices/{uuid}/` holds index segments with their own `fragment_bitmap` for partial coverage; `_refs/` holds Lance-native per-dataset branches and tags.
 

docs/testing.md

@@ -19,7 +19,8 @@ The engine's `tests/` is the principal coverage surface; most graph-shaped behav
 |---|---|
 | `end_to_end.rs` | Full init → load → query/mutate flow |
 | `branching.rs` | Branch create / list / delete, lazy fork |
-| `runs.rs` | Transactional runs (begin/publish/abort), idempotency |
+| `runs.rs` | Direct-publish writes: cancellation, concurrent-writer CAS, multi-statement atomicity, MR-794 staged-write rewire (D₂ rejection, insert+update coalesce, multi-append coalesce, partial-failure recovery, load RI/cardinality recovery) |
+| `staged_writes.rs` | TableStore staged-write primitives (`stage_append`, `stage_merge_insert`, `commit_staged`, `scan_with_staged`, `count_rows_with_staged`) — primitive-level only; engine code uses the in-memory `MutationStaging` accumulator instead |
 | `lifecycle.rs` | Repo lifecycle, schema state |
 | `point_in_time.rs` | Snapshots, time travel (`snapshot_at_version`, `entity_at`) |
 | `changes.rs` | `diff_between` / `diff_commits` |