Context

Phase 5 Community Detection (epic #1222, issue #1228) relies on the extraction_count metadata value to trigger periodic community detection.

Problem

The extraction counter increment in semantic.rs uses two separate SQL statements:

1. INSERT INTO graph_metadata ... ON CONFLICT DO NOTHING
2. UPDATE graph_metadata SET value = CAST(CAST(value AS INTEGER) + 1 AS TEXT)

This is not atomic — under concurrent access, two tasks could both execute the INSERT (one succeeds, one is no-op) then both UPDATE. SQLite WAL serializes writers so double-increment is unlikely in practice, but the pattern depends on SQLite serialization guarantees.

Suggested Fix

Merge into a single atomic statement:

INSERT INTO graph_metadata (key, value) VALUES ('extraction_count', '1')
ON CONFLICT(key) DO UPDATE SET value = CAST(CAST(value AS INTEGER) + 1 AS TEXT)

This is atomic in SQLite and eliminates the two-statement pattern.

Source

PERF-04 from Phase 5 performance analysis.