* feat(persistence): wire alembic migrations + bootstrap schema on startup
Closes#3682. Pre-#3658 DBs lack the `runs.token_usage_by_model` column
because alembic was never wired up — startup only ran `create_all`,
which never ALTERs existing tables.
Adds a hybrid bootstrap in FastAPI lifespan (replaces bare `create_all`):
- empty DB → create_all + stamp head
- legacy DB → stamp 0001_baseline + upgrade head
- versioned DB → upgrade head
Concurrency: Postgres `pg_advisory_lock` (cross-process); SQLite
per-engine `asyncio.Lock` + 30s `PRAGMA busy_timeout` on both prod and
alembic engines. Column revisions use `safe_add_column` /
`safe_drop_column` idempotent helpers as fallback.
Other bits:
- 0001 baseline (chain root) + 0002 add `runs.token_usage_by_model`
- `include_object` filter so alembic ignores LangGraph checkpointer tables
- `make migrate-rev MSG="..."` for authoring new revisions
(no migrate/stamp targets — startup is the only execution path)
- Tests: three-branch decision, concurrency, #3682 regression, env
filter, blocking-IO gate anchor
- CLAUDE.md: new "Schema migrations" section
* fix(style): fix lint error
* perf(persistence): address review feedback on alembic bootstrap
Behavioural fixes
- _SQLITE_LOCKS now keyed via WeakKeyDictionary so id-reuse after GC
cannot return a stale, loop-bound lock and the cache cannot leak one
entry per disposed engine.
- safe_add_column compares nullable / server_default against the desired
column when the name already exists and emits a warning on drift,
surfacing manual-ALTER workarounds instead of silently no-op'ing.
- _postgres_lock issues SET LOCAL idle_in_transaction_session_timeout=0
before pg_advisory_lock, so managed Postgres cannot kill the idle
lock-holding session mid-upgrade and silently release the advisory
lock.
- legacy branch now backfills missing baseline tables via a restricted
create_all (Base.metadata.create_all scoped to _BASELINE_TABLE_NAMES).
Restores pre-#1930 upgraders whose channel_* tables were never
provisioned, without pre-empting future create_table revisions for
newly-added models.
Schema parity
- runs.token_usage_by_model gains server_default=text("'{}'") in both
the ORM model and the 0001_baseline create_table, matching what 0002
adds via ALTER. create_all and alembic-upgrade paths now produce
identical column definitions.
- New parity test compares Base.metadata.create_all output against a
pure alembic upgrade base->head, asserting column-set, nullable, and
server_default agree across all tables (normalized through the same
helper safe_add_column's drift check uses).
Guards
- test_baseline_table_names_constant_matches_0001 pins
_BASELINE_TABLE_NAMES to 0001_baseline.upgrade()'s actual output --
the constant cannot drift silently when someone edits 0001.
- test_legacy_backfill_skips_non_baseline_tables verifies the restricted
backfill does not create a phantom table on Base.metadata, modelling
a future revision that would otherwise collide on op.create_table.
Doc residuals
- Three-branch decision table is now consistent across bootstrap.py
top docstring, engine.py comment, test module docstring, and
CLAUDE.md.
- Stale test anchor in blocking_io/test_persistence_engine_sqlite.py
docstring now points at the real file.
* fix(style): fix lint error
* fix(persistence): close drift detection holes
- _check_column_drift compares column type via a family equivalence
allowlist ({JSON, JSONB}). Catches the wrong-type workaround
`TEXT NOT NULL DEFAULT '{}'` that previously slipped through silently,
while keeping Postgres JSON/JSONB dialect reflection quiet. Reflected
and desired type are also echoed in every drift warning's payload for
operator triage.
- Extract _escape_url_for_alembic so bootstrap._alembic_safe_url and
scripts/_autogen_revision share the ConfigParser % escape rule
instead of duplicating it.
- backend/README.md: add `make migrate-rev MSG=...` to Commands and a
Schema Migrations section per the repo's README/CLAUDE.md sync policy.
- test_base_to_dict.py: scope the test ORM class to an isolated MetaData
so the create_all-vs-alembic parity test (added in the previous
commit) is not polluted by the phantom table on the full pytest
session.
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