fix(persistence): derive SCHEMA_VERSION from the migrations directory

db.py hardcoded SCHEMA_VERSION = 26 while migrations/ had already reached
v29 (v27 dispatcher floor-drop counter, v28 mesh_observations, v29 IPAWS).
The migration runner globs the directory and applies every vN.sql it finds
regardless of the constant, so a fresh DB actually landed at 29 while the
constant claimed 26 -- a three-version drift that three tests were
correctly catching.

Derive it from the highest vN.sql present instead of bumping the literal,
so it cannot drift again the next time someone adds a migration. Falls back
to 0 if the directory is missing so import never fails; the migrations dir
sits alongside db.py and ships with the package (Dockerfile COPYs meshai/).

Adds a regression guard asserting the constant matches the highest
migration file, and updates three tests that hardcoded 26 as a literal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

work/meshai/persistence/db.py

@@ -30,9 +30,11 @@ logger = logging.getLogger(__name__)
 
 DEFAULT_DB_PATH = "/data/meshai.sqlite"
 MESHAI_DB_PATH_ENV = "MESHAI_DB_PATH"
-SCHEMA_VERSION = 26
 SCHEMA_META_TABLE = "schema_meta"
 MIGRATIONS_DIR = Path(__file__).parent / "migrations"
+# SCHEMA_VERSION is derived below (after _read_migration_files is defined)
+# from the highest vN.sql present in MIGRATIONS_DIR, so it can never drift
+# from what a fresh DB actually lands at -- see _derive_schema_version().
 
 # Per-thread connection pool. Each thread that calls get_db() gets its
 # own sqlite3.Connection cached on threading.local. Tests can clear
@@ -163,6 +165,22 @@ def _read_migration_files() -> list[tuple[int, str, str]]:
     return out
 
 
+def _derive_schema_version() -> int:
+    """Highest migration version present in MIGRATIONS_DIR, i.e. the
+    version a fresh DB lands at once _apply_migrations() runs (it applies
+    every vN.sql it finds, independent of any hardcoded constant). Falls
+    back to 0 if the directory is missing/empty so import never fails;
+    that would only happen in a broken packaging layout, since
+    MIGRATIONS_DIR sits alongside this file and is copied/installed with
+    the rest of the meshai package (see Dockerfile: `COPY meshai/ ./meshai/`
+    then `pip install -e .`)."""
+    versions = [n for n, _, _ in _read_migration_files()]
+    return max(versions) if versions else 0
+
+
+SCHEMA_VERSION = _derive_schema_version()
+
+
 def _current_version(conn: sqlite3.Connection) -> int:
     """Return the highest applied migration version, or 0 if none."""
     # Does the schema_meta table exist?

work/tests/test_observer_locations.py

@@ -14,8 +14,11 @@ from meshai.persistence.observer_locations import (
 
 # -- schema / migration -------------------------------------------------------
 
-def test_schema_version_is_25():
-    assert SCHEMA_VERSION == 26
+def test_schema_version_is_current():
+    # SCHEMA_VERSION is derived from the highest vN.sql in migrations/, so
+    # this just guards against the derivation returning something bogus
+    # (e.g. 0, which would mean the migrations dir wasn't found).
+    assert SCHEMA_VERSION >= 23
 
 
 def test_observer_locations_table_exists():
@@ -30,7 +33,7 @@ def test_schema_meta_at_current():
     conn = get_db()
     row = conn.execute(
         "SELECT value FROM schema_meta WHERE key='version'").fetchone()
-    assert int(row["value"]) == 26
+    assert int(row["value"]) == SCHEMA_VERSION
 
 
 # -- accessors ----------------------------------------------------------------

work/tests/test_persistence.py

@@ -90,6 +90,23 @@ def test_schema_version_recorded(tmp_db):
     assert int(row["value"]) == SCHEMA_VERSION
 
 
+def test_schema_version_matches_highest_migration_file():
+    """SCHEMA_VERSION is derived from migrations/ at import time (see
+    db._derive_schema_version); this test independently re-derives the
+    expected value straight off the filenames so a future regression
+    (e.g. someone re-hardcoding the constant) is caught even if the
+    derivation logic itself is what breaks."""
+    import re
+
+    versions = []
+    for p in persistence_db.MIGRATIONS_DIR.iterdir():
+        m = re.match(r"^v(\d+)", p.stem)
+        if p.suffix.lower() == ".sql" and m:
+            versions.append(int(m.group(1)))
+    assert versions, "no vN.sql migration files found"
+    assert SCHEMA_VERSION == max(versions)
+
+
 def test_migration_idempotent_rerun(tmp_db):
     init_db()
     # Force a "second startup" by closing the connection and clearing the

work/tests/test_satpass_persisted_timer.py

@@ -99,9 +99,11 @@ def _ingest_envelope(norad_id=25544, observer="Boise", max_el=72.5,
 # ── schema / migration ───────────────────────────────────────────────
 
 def test_schema_version_is_current():
-    # Bumped to 26 by the generic-source migration (v26 generic_events); v24
-    # avalanche_events, v25 ducting_events; was 23 at native-satpass (v23).
-    assert SCHEMA_VERSION == 26
+    # SCHEMA_VERSION is derived from the highest vN.sql in migrations/, so
+    # this just guards against the derivation returning something bogus
+    # (e.g. 0, which would mean the migrations dir wasn't found). The v22
+    # migration (this file's focus) must always be <= the current version.
+    assert SCHEMA_VERSION >= 22
 
 
 def test_v22_migration_applies_and_adds_due_at_column(tmp_path, monkeypatch):
@@ -114,7 +116,7 @@ def test_v22_migration_applies_and_adds_due_at_column(tmp_path, monkeypatch):
     close_thread_connection()
     conn = init_db()
     row = conn.execute("SELECT value FROM schema_meta WHERE key='version'").fetchone()
-    assert int(row["value"]) == 26
+    assert int(row["value"]) == SCHEMA_VERSION
     cols = {r["name"] for r in conn.execute("PRAGMA table_info(satpass_pending)")}
     assert "due_at" in cols
     close_thread_connection()