deer-flow/backend/packages/harness/deerflow/persistence/migrations/AGENTS.md

Schema Migrations (packages/harness/deerflow/persistence/migrations/)

DeerFlow's application tables (runs, threads_meta, feedback, users, run_events, plus the four channel_* tables) are owned by alembic via a hybrid bootstrap strategy. LangGraph's checkpointer tables (checkpoints, checkpoint_blobs, checkpoint_writes, checkpoint_migrations) live in the same database but are owned by LangGraph and excluded from alembic's view via migrations/_env_filters.py::include_object.

Convention: every ORM model change (new column, new table, new index) MUST ship as an alembic revision under migrations/versions/. The Gateway runs alembic upgrade head automatically on startup; routine production upgrades do not require manual Alembic commands. The audited offline recovery below is an exception for the out-of-tree incarnation revision.

Hybrid bootstrap (persistence/bootstrap.py::bootstrap_schema, invoked from persistence/engine.py::init_engine):

DB state	Action
empty (no DeerFlow tables)	create_all + alembic stamp head
legacy (DeerFlow tables, no alembic_version)	create_all (baseline tables only, backfill) + alembic stamp 0001_baseline + upgrade head
versioned (one locally known alembic_version row)	alembic upgrade head
0019_thread_incarnations with all current ORM tables/columns	warn and skip migration
0019_thread_incarnations missing local tables/columns	refuse startup; offline recovery required
unknown revision, empty version table, or multiple version rows	fail closed and refuse to start

The legacy branch handles pre-alembic databases that already have at least one DeerFlow-owned table. create_all runs first because stamping at 0001_baseline makes alembic skip the baseline's own create_table DDL on the subsequent upgrade — so any baseline table introduced into Base.metadata after the user's DB was first provisioned (e.g. the channel_* tables from PR #1930 for users upgrading across multiple releases) would otherwise never be created, and the first request hitting that table would 500 with no such table. The backfill is restricted to _BASELINE_TABLE_NAMES so it does not also create tables that future revisions introduce — those revisions' own op.create_table would otherwise fail with relation already exists. A guard test pins _BASELINE_TABLE_NAMES against 0001_baseline.upgrade()'s actual output, so editing 0001 to add or remove a table forces a matching update to the constant. Column-level shape (pre-#3658 vs post-#3658 vs manual-ALTER for token_usage_by_model) is answered by each versions/*.py revision via the idempotent helpers in migrations/_helpers.py (safe_add_column / safe_drop_column) which no-op when the change is already present and logger.warning on shape drift. Adding a new ORM column / table only requires a new revision file — no edit to bootstrap.py is needed unless the new revision adds a new baseline table (rare; only happens when a new model is part of the baseline rather than introduced by its own revision).

The empty-DB path keeps using create_all because Base.metadata is the only authoritative schema source — create_all renders both SQLite (JSON, type affinity) and Postgres (JSONB, partial indexes) correctly without anyone having to keep a hand-written baseline in lockstep. 0001_baseline.upgrade() is therefore almost never executed in practice; it exists as a stamp target + chain root.

Rolling forward compatibility: the local chain is 0018_oauth_identity_pg_partial → 0019_projects → 0020_threads_meta_project_id → 0021_batch_acceptance → 0019_thread_incarnations. The final revision deliberately retains the exact id audited by the rollback-floor binary; Alembic orders revisions by down_revision, not by the numeric prefix.

The deployed 0020_threads_meta_project_id rollback-floor binary knows neither 0021_batch_acceptance nor 0019_thread_incarnations. It treats only the final incarnation revision as forward-compatible, after reflection confirms every table and column in its own ORM schema. The intervening acceptance columns and the incarnation columns are nullable and have no server default, so old repositories may omit them. Tests must prove old reads and writes across both additive revisions; do not model the rollback binary with 0021 in its local revision set.

The same incarnation revision id existed briefly as an out-of-tree child of 0018. Current and future binaries that know the reused 0019_thread_incarnations id validate a fixed table/column snapshot of the canonical in-tree 0019 schema whenever they see that stamp. The original 0018-plus-incarnation shape is rejected because it lacks Projects and batch-acceptance schema; matching the revision string alone is not proof of the new ancestry. The fixed floor is deliberately not derived from Base.metadata: a future binary may add mapped columns after 0019 and must validate this floor before Alembic adds them. A binary that knows 0019 upgrades normally after the check.

Tests that model the rollback binary by removing 0021_batch_acceptance and 0019_thread_incarnations from the mocked local revision set exercise the unknown-revision branch of the current implementation. They therefore use the new fixed canonical-0019 floor; they do not execute the ORM-derived check from the published 0020 binary. Reflection checks presence only; each migration preflight owns type, nullability, and default compatibility.

Any other unknown revision, an empty version table, or multiple version rows fails closed. Do not broaden the allowlist without proving that the rollback repositories can read, insert, and update through the newer schema. The exception is reviewed only for the additive 0021 JSON columns plus nullable VARCHAR(32) threads_meta.incarnation and mcp_tasks.thread_incarnation columns, all without non-NULL defaults, constraints, or data backfills. The incarnation migration and tests cross-pin its revision id and DDL shape; changing either requires a fresh old-repository compatibility audit. SQLite's stale-upgrade recovery remains available only to a rollback binary whose migration tree owns neither post-0020 revision. A current binary owns both, so migration failures remain fatal.

For an existing database with the original 0018-plus-incarnation shape, use the audited offline recovery procedure. Bootstrap never re-stamps an unknown revision automatically. After stopping all writers, backing up, and verifying the exact additive schema, the operator may purge-stamp the known 0018 parent and apply the Projects, acceptance, and incarnation migrations through the current head; the extra nullable columns and their data remain intact. A regression exercises that procedure from the original schema and verifies repository reads/inserts and preservation of incarnation data.

Concurrency safety: Postgres uses pg_advisory_lock to serialise concurrent Gateway instances. SQLite uses a per-engine asyncio.Lock for same-process startup and is best-effort across processes via SQLite's file-level write lock + PRAGMA busy_timeout; multi-instance deployments should use Postgres. Column revisions in versions/ additionally use idempotent helpers (_helpers.py::safe_add_column, safe_drop_column) so repeated post-baseline changes and retries are no-ops when the change is already present.

Authoring a new revision:

cd backend && make migrate-rev MSG="add foo column to runs"

This invokes alembic revision --autogenerate against the live ORM models. Review the generated file under migrations/versions/ and switch raw op.add_column / op.drop_column calls to the idempotent helpers from _helpers.py before committing. There is no make migrate / make migrate-stamp target on purpose — routine upgrades execute at Gateway startup; the documented offline recovery is reserved for the audited out-of-tree schema.

Extension-owned tables. An extension that persists data owns its schema end to end and must not register models against deerflow.persistence.base.Base — doing so makes the host's empty-DB create_all create the extension's tables on installs that never enabled it. The convention is:

• one MetaData instance private to the extension;

• every table sharing one prefix, declared via the plugins: record's ExtensionSpec.table_prefix field, so alembic revision --autogenerate ignores them instead of reflecting them, finding them absent from Base.metadata, and proposing drop_table. Registration happens in two places on purpose, because two different processes read the filter: extensions/loader.py::load_extensions covers the Gateway, and register_configured_extension_table_prefixes() — called from migrations/env.py — covers the alembic process, which never starts a Gateway and would otherwise see an empty prefix set exactly where include_object consumes it. The alembic side reads the declaration out of config.yaml and never imports extension code: a migration process must not execute third-party code. The Gateway side registers unconditionally, even for a disabled or later-failing spec, because the tables it names may already exist in the database from a previous run. Because those two readers cannot both be right about an empty prefix — the Gateway's truthiness test reads it as "no prefix", a literal reader as one matching every table — ExtensionSpec.table_prefix carries min_length=1, and the alembic-side reader (which parses raw YAML, so pydantic never runs there) skips anything that model would reject rather than raising: an operator does not expect to hear about a malformed config.yaml from alembic, and Gateway startup runs that same module through bootstrap_schema;

  Scope, because it is narrower than it first appears: make migrate-rev is already safe without this. scripts/_autogen_revision.py builds a throwaway SQLite from the migration chain and diffs against that, so no extension table — and no LangGraph table — is ever reflected. The exposed path is running alembic revision --autogenerate directly from the migrations directory, where alembic.ini points sqlalchemy.url at a real ./data/deerflow.db. That is the same path LANGGRAPH_OWNED_TABLES covers, which is why that exclusion exists even though the throwaway-DB script landed in the same commit;

• an independent alembic chain with its own version_table="<prefix>alembic_version", run from ExtensionService.start() against ExtensionRuntimeDeps.session_factory's bind — which is sequenced after the host's own bootstrap by construction, since services start once persistence is ready;

• a Postgres advisory lock around that upgrade, mirroring bootstrap_schema, so concurrent Gateway instances serialise.

Where things live:

• migrations/env.py — alembic env, delegates filter to _env_filters.py, sets render_as_batch=True for SQLite ALTER support
• migrations/_env_filters.py::include_object — drops LangGraph checkpointer tables and any registered extension-owned tables (EXTENSION_TABLE_PREFIXES) from alembic's view
• migrations/_env_filters.py::register_configured_extension_table_prefixes — populates that set inside the alembic process, reading plugins[*].table_prefix from config.yaml and never importing extension code; called at import from migrations/env.py, because load_extensions() only ever runs in the Gateway
• migrations/_helpers.py — safe_add_column / safe_drop_column
• migrations/versions/0001_baseline.py — chain root, matches the schema create_all produces from Base.metadata
• migrations/versions/0002_runs_token_usage.py — fixes issue #3682
• migrations/versions/0004_run_ownership.py — runs multi-worker ownership + the uq_runs_thread_active partial unique index, with a _dedupe_active_runs_per_thread() pre-step so CREATE UNIQUE INDEX cannot fail on a field DB that already has duplicate active rows per thread
• migrations/versions/0007_scheduled_run_active_index.py — the uq_scheduled_task_run_active partial unique index (at most one queued/running scheduled_task_runs row per task_id), with a _dedupe_active_scheduled_runs_per_task() pre-step (keeps the newest active row per task, supersedes the rest to interrupted with an explanatory error + finished_at) mirroring 0004; chains after 0006_agents
• migrations/versions/0008_thread_operation_kind.py — adds runs.operation_kind for durable non-run thread reservations; chains after 0007_scheduled_run_active_index
• migrations/versions/0010_run_cancel_request.py — adds the nullable runs.cancel_action / cancel_requested_at handoff used by non-owning workers; chains after 0009_webhook_dedupe
• migrations/versions/0011_mcp_tasks.py — creates the durable long-running MCP task table and its user/server/remote uniqueness constraint
• migrations/versions/0012_mcp_task_results.py — adds bounded result preview/truncation/artifact fields for ordinary task drivers
• migrations/versions/0013_mcp_task_notifications.py — adds durable Agent-run notification snapshots, delivery leases, idempotency fields, and the separate bounded-retry attempt counter
• migrations/versions/0014_managed_subagents.py — creates the deployment-level managed Subagent catalog table
• migrations/versions/0015_scheduled_task_enqueue.py — interrupts legacy transient queued rows, adds durable scheduled-run launch leases and attempt counts, expands the one-active-occurrence index to queued/launching/running, and migrates the overlap policy from skip to enqueue; chains after 0014_managed_subagents
• migrations/versions/0016_subagent_batches.py — creates durable native-subagent batch and item tables, including owner/submission idempotency, item identity, lease/recovery state, and result fields
• migrations/versions/0017_personal_access_tokens.py — creates the personal access token table for programmatic API access
• migrations/versions/0018_oauth_identity_pg_partial.py — converts idx_users_oauth_identity to a partial index on Postgres (postgresql_where), matching what UserRow.__table_args__ already builds via create_all; 0001_baseline never applied the predicate on Postgres, so every alembic upgrade head-provisioned deployment carried a full index until this revision. Postgres-only, idempotent (checks pg_index.indpred directly), no-op on SQLite (already partial via sqlite_where) and on a DB where the index doesn't exist yet. Originally generated as 0017 and renumbered to 0018 after 0017_personal_access_tokens merged first and kept that slot
• migrations/versions/0019_projects.py — creates the projects table (id/user_id/name/instructions/presentation/status + timestamps) for the Projects Phase-1 organization feature; chains after 0018_oauth_identity_pg_partial
• migrations/versions/0020_threads_meta_project_id.py — adds nullable threads_meta.project_id plus ix_threads_meta_project_id (no FK by design: project delete clears membership first, and the reserved deerflow_project_id metadata key stays in sync); chains after 0019_projects
• migrations/versions/0021_batch_acceptance.py — adds nullable per-item acceptance criteria and verdict JSON columns after 0020_threads_meta_project_id; legacy rows remain unchecked
• migrations/versions/0019_thread_incarnations.py — current head; chains after 0021_batch_acceptance while retaining the exact revision id audited by the rollback-floor binary. Adds nullable threads_meta.incarnation / mcp_tasks.thread_incarnation columns. New thread rows get a random 32-character incarnation. Memory mutations serialize per thread; an overwrite inherits the existing incarnation, while a delete/recreate gets a new one. SQLite MCP task INSERTs copy the owner-or-shared incarnation with a scalar subquery in the same statement. PostgreSQL task creation holds FOR SHARE, which conflicts with both current FOR UPDATE mutations and an older writer's plain owner update (FOR NO KEY UPDATE). Missing or differently owned threads store NULL, old writers may omit both columns, and current API/task serialization hides them. The migration preflights both tables before DDL and its SQLite downgrade cleans only safe remnants from its own interrupted batch-copy attempt
• persistence/bootstrap.py — bootstrap_schema(engine, backend=...), the three-branch provisioning decision, locked revision validation, and the narrow 0019 forward-compatibility exception
• extensions/loader.py::load_extensions — registers each spec's table_prefix with register_extension_table_prefix()
• Tests: tests/test_persistence_bootstrap.py (branches), tests/test_persistence_bootstrap_concurrency.py (concurrency), tests/test_persistence_bootstrap_regression.py (issue #3682), tests/test_persistence_migrations_env.py (filter, including extension-owned tables), tests/test_extension_loader.py::TestTablePrefixRegistration (spec-to-filter wiring), tests/blocking_io/test_persistence_bootstrap.py (asyncio.to_thread anchor), tests/test_migration_0004_run_ownership_dedupe.py + tests/test_migration_0007_scheduled_run_active_dedupe.py (dedupe-before-unique-index pre-steps)