[dagster] Transient SQLAlchemy >=2.1 bump creates dependency trap: Missing 'psycopg' vs NOTIFY run_events

## Observed symptom Transient bump to SQLAlchemy >=2.1 creates dependency trap: Missing 'psycopg' vs 'NOTIFY run_events, $1' syntax error ### What's the issue? SQLAlchemy transitive bump breaks PostgreSQL storage (psycopg ModuleNotFoundError / NOTIFY $1 error) ## Summary A transitive dependency bump of `sqlalchemy` (to 2.1.x / 2.0.x) introduces a catch-22 / "rock and a hard place" state when using `dagster-postgres`: 1. **`psycopg2` failure:** SQLAlchemy defaults to using `psycopg` (v3). If `psycopg` is missing, Dagster fails on startup with: `ModuleNotFoundError: No module named 'psycopg'` 2. **`psycopg` (v3) failure:** Installing `psycopg` causes Dagster's event log storage to fail on run monitoring with: `sqlalchemy.exc.ProgrammingError: (psycopg.errors.SyntaxError) syntax error at or near "$1"` `[SQL: NOTIFY r ## Literal error text ``` Missing 'psycopg' vs NOTIFY run_events ``` ## Environment GitHub dagster-io/dagster #34232 ## Trigger / context ### What's the issue? SQLAlchemy transitive bump breaks PostgreSQL storage (psycopg ModuleNotFoundError / NOTIFY $1 error) ## Summary A transitive dependency bump of `sqlalchemy` (to 2.1.x / 2.0.x) introduces a catch-22 / "rock and a hard place" state when using `dagster-postgres`: 1. **`psycopg2` failure:** SQLAlchemy defaults to using `psycopg` (v3). If `psycopg` is missing, Dagster fails on startup with: `ModuleNotFoundError: No module named 'psycopg'` 2. **`psycopg` (v3) failure:** Installing `psycopg` causes Dagster's event log storage to fail on run monitoring with: `sqlalchemy.exc.ProgrammingError: (psycopg.errors.SyntaxError) syntax error at or near "$1"` `[SQL: NOTIFY run_events, %(notify_id)s;]` ## Expected Behavior Dagster should gracefully handle PostgreSQL storage without requiring manual driver overrides or breaking when transitive dependencies update SQLAlchemy. ## Workaround Pin `sqlalchemy==2.0.54` ### What did you expect to happen? _No response_ ### ## Source evidence - https://github.com/dagster-io/dagster/issues/34232 (2026-10-01T16:52:30Z) — #34232 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:49:02.645589Z - scout_id: Ca0343faa6a ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.