## What
Wires the run-ops split into the webapp: database topology, environment
flags, split-mode gating, and the control-plane resolver/cache layer
that the run-store and run-engine seams from the previous PR plug into.
- **DB topology & env** (`apps/webapp/app/db.server.ts`,
`env.server.ts`, `entry.server.tsx`): adds the run-ops database
clients/topology and the environment variables that configure and gate
the split.
- **runOpsMigration module** (new
`apps/webapp/app/v3/runOpsMigration/`): the webapp-side machinery —
`splitMode.server.ts`, `controlPlaneResolver.server.ts` +
`controlPlaneCache.server.ts`, `readThrough.server.ts`,
`crossSeamGuard.server.ts`, `distinctDbSentinel.server.ts`, id-minting
helpers (`mintBatchFriendlyId`, `runOpsMintKind`,
`resolveInheritedMintKind`), `runOpsCascadeCleanup.server.ts`, the split
read gate, and route/unblock catalogs.
- **Store/engine wiring** (`app/v3/runStore.server.ts`,
`runEngine.server.ts`, `runEngineHandlers.server.ts` + new
`runEngineHandlersShared.server.ts`): points the webapp's store/engine
construction at the resolver, and factors shared handler logic out so
both seams use one path.
- **Read-path touch-ups**: `runtimeEnvironment.server.ts`,
`eventRepository/index.server.ts`, `taskRunHeartbeatFailed.server.ts`,
`engineVersion.server.ts` route their run/environment lookups
read-through the resolver.
- `413a94511` — interlocks split mode against the native realtime
backend so the two aren't enabled in an incompatible combination (see
`.server-changes/run-ops-split-realtime-interlock.md`).
- `dc74c57fd` — drops the earlier "known-migrated" read layer; residency
is determined by id-shape only.
## Why
PR5 of the run-ops split stack. This is the webapp foundation layer: it
stands up the DB topology, flags, and resolver/cache the rest of the
stack depends on, and repoints webapp read paths through the resolver.
Additive when the split is not enabled (existing single-DB behavior
preserved behind flags); behavior-changing on the read-through paths and
the realtime interlock.
## Tests
New vitest coverage across `apps/webapp/test/` and colocated
`*.server.test.ts` files: db topology, split mode, split read gate,
cross-seam guard, mint cutover / flip latency, control-plane cache,
control-plane resolver, distinct-db sentinel, read-through loaders
(route loaders, run-detail loaders, `findEnvironmentFromRun`), and the
run-engine handlers. Testcontainers-backed; no mocks. `pnpm-lock.yaml`
synced for the two new webapp deps.
## Notes
Draft, **stacked on #4116** (`runops/pr04-store-engine`). Review that
first; this diff is against it.
Server-change / changeset note to be added at stack-assembly time.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Daniel Sutton