## Problem
Hundreds of DB-backed tests build a fresh in-memory store in
`beforeEach` and call `db.init()`, which replays `SCHEMA_SQL` + **~129
migrations every single test** (~40ms each). Across thousands of tests
this is minutes of pure setup. The slowest core store suites are
dominated entirely by this.
## Approach (Option A: serialize/deserialize snapshot)
`node:sqlite` (and `bun:sqlite`) expose `serialize()`/`deserialize()`. I
migrate **one** in-memory DB per test file, serialize it to a byte
buffer, and register it via a test-only hook. Every subsequent in-memory
`Database` deserializes the snapshot at open time, so `init()` finds
`schemaVersion === SCHEMA_VERSION` plus the matching compat fingerprint
and short-circuits `migrate()` + all backfills.
Why this over the existing truncate-based
`createSharedTaskStoreTestHarness`: the snapshot keeps the **exact same
per-test isolation model** — each test still constructs its own
brand-new, fully-isolated DB — so suites that reassign their store/db
inside test bodies (both targets do) need no restructuring. Only the
migration cost is amortized. Disk-backed (production) DBs are never
touched; the hook is `null` in production, so behavior is unchanged.
### Harness API
```ts
beforeAll(() => installInMemoryDbSnapshot());
afterAll(() => clearInMemoryDbSnapshot());
// existing per-test `new <Store>({ inMemoryDb: true }); init()` stays as-is
```
- `packages/core/src/__tests__/store-test-helpers.ts` — core suites
- `packages/dashboard/src/__tests__/db-snapshot-helper.ts` — dashboard
suites (core `__tests__` is a private cross-package dir, so it mirrors
via the new public `setInMemoryTemplateSnapshot` export)
## Before / after
Raw `db.init()` microbenchmark: **43.4ms → 5.4ms (8x)**.
| Suite | Tests | Before | After | Note |
|---|---|---|---|---|
| `agent-store.test.ts` | 199 | 13.12s | **3.32s** | ~4x; init-dominated
|
| `mission-store.test.ts` | 261 | 17.62s | **5.69s** | ~3x; min of 3 |
| `workflow-routes.test.ts` | 53 | tests 4.38s | **tests 2.79s** | min
of 5; not init-dominated, so a smaller (~36%) but real win — most of its
time is express/route logic, not DB init |
All converted suites pass with **0 failures** and every original
assertion preserved. `db.test.ts` (which tests init/migration directly)
is intentionally left unconverted and still passes. Core + dashboard
typecheck clean; lint clean.
> Honest note: `workflow-routes` machine timings were noisy (same config
varied 5–13s under load); the `tests`-portion min-of-5 is the reliable
signal. The snapshot helps every in-memory suite, but the suite-level
win scales with how init-dominated the suite is.
## No changeset
Changes are test-infra only and behavior-preserving for the published
bundle — the snapshot hook is a no-op (`null`) in production. Per
AGENTS.md, no changeset for behavior-preserving/internal changes.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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## Summary by CodeRabbit
* **Chores**
* Improved in-memory database handling for test runs by reusing a
prepared snapshot instead of rebuilding it repeatedly.
* Added snapshot support to the database layer and SQLite adapter to
speed up initialization in test environments.
* Updated core and dashboard test suites to use shared setup/teardown
for the cached database state.
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