diff --git a/openspec/changes/mapgen-studio-bun-server/design.md b/openspec/changes/mapgen-studio-bun-server/design.md
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+# Design — Standalone Bun daemon for the Studio server surface
+
+## Current state (verified 2026-06-12)
+
+- `vite.config.ts` (1,420 lines) carries: ~950 lines of engine code at
+  module scope (queue, two operation stores, instance identity, autoplay /
+  run-in-game / save-deploy engines), 16 legacy REST handlers, and three
+  oRPC mounts (`/rpc` studio-server, `/api/civ7/rpc` control,
+  `/api/recipe-dag/rpc` recipe-DAG via per-request `ssrLoadModule`).
+- The client is already 100% oRPC: zero manual `/api/*` fetches in app
+  source. The only `/api` strings client-side are the two oRPC path
+  constants. (P2 client-data slice did the cutover of reads.)
+- `@civ7/studio-server`'s handler is already the A4-lite fetch shape
+  (`Request`/`Response`); the recipe-DAG handler likewise
+  (`createStudioRecipeDagRpcHandler`). Only the control mount still uses
+  the node adapter (`@orpc/server/node`).
+- Production (`railway.json`/Caddy) serves static `dist` only — no server.
+
+## Topology decision
+
+Blueprint: `tools/gt-stack-inspect` on
+`codex/gt-stack-inspect-dev-live-topology` (read-only prior art) — a Bun
+daemon (`Bun.serve({ fetch })` over a fetch-adapter RPC handler + static
+assets + `/healthz`), a `dev-live` runner spawning daemon then Vite, and a
+Vite proxy for the RPC prefix. The studio adopts the same shape:
+
+```
+bun run dev
+  └─ src/server/daemon/devLive.ts        (runner)
+       ├─ spawns: bun src/server/daemon/daemon.ts --port 5174   (backend)
+       │    Bun.serve fetch router:
+       │      /healthz                → runtime health (json)
+       │      /rpc/*                  → createStudioRpcHandler (studio-server)
+       │      /api/civ7/rpc/*         → control-oRPC fetch handler
+       │      /api/recipe-dag/rpc/*   → recipe-DAG fetch handler (static import)
+       │      /api/*                  → legacy REST compat (same engines)
+       │      static dist (optional, --assets-root; prod story)
+       └─ spawns: vite --port 5173                              (frontend)
+            server.proxy: /rpc → 5174, /api → 5174
+```
+
+- Ports: Vite keeps 5173 (`strictPort`); daemon defaults to 5174.
+  `STUDIO_DEV_RPC_TARGET` overrides the proxy target so `vite` alone still
+  works against an already-running daemon.
+- The daemon resolves `repoRoot` from its own module location by default
+  (`--repo-root` overrides), mirroring the engines' previous
+  `vite.config.ts`-relative resolution.
+- `Bun.serve` is typed via a minimal local `declare const Bun` (blueprint
+  pattern) — no new dependency; the module is executed only under Bun.
+
+## Engine extraction (slice 2 — no topology change)
+
+`createStudioEngines({ repoRoot })` in `src/server/studio/engines.ts` owns
+all process-singleton state and returns the five engine functions plus
+identity. Moved **verbatim** from `vite.config.ts`; the only edits are the
+factory closure and `repoRoot` parameterization (previously recomputed per
+call via `fileURLToPath(new URL("../..", import.meta.url))`).
+
+`createStudioServerContext({ engines, hostCommand })` in
+`src/server/studio/context.ts` is the moved `createStudioServerContextForApp`
+— the `RunInGameHttpError → ORPCError` mapping that preserves the
+non-uniform status codes (arch/10 §1 parity invariants).
+
+Module constraint (load-bearing): `engines.ts` imports
+`@civ7/direct-control` + local server modules only — **never
+`effect-orpc`** — so the interim static import into `vite.config.ts` stays
+node-evaluable. `@civ7/studio-server` is safe (tsup bundles effect-orpc
+into its dist); app-src effect-orpc consumers (the recipe-DAG router) stay
+out of the config graph until the daemon slice removes the need entirely.
+
+Slice 2 leaves Vite hosting everything — the config consumes the extracted
+module at module scope, identical behavior, all transports still share one
+engine instance per process.
+
+## Control-oRPC fetch adapter (slice 3)
+
+`civ7ControlOrpc.ts` re-shapes to mirror `recipeDag/orpc.ts`: canonical
+`createStudioCiv7ControlRpcHandler` on `RPCHandler` from
+`@orpc/server/fetch` (prefix `STUDIO_CIV7_CONTROL_ORPC_PATH`), plus the
+Connect shim over `server/http/nodeWebBridge` for the Vite mount this
+slice. Context construction (`directControl` facade + `endpointDefaults`)
+unchanged. Path contract unchanged.
+
+## Daemon + cutover (slice 4)
+
+- `src/server/daemon/daemon.ts`: arg parsing (`--host`, `--port`,
+  `--repo-root`, `--assets-root`), one `createStudioEngines` instance, the
+  three fetch handlers, the legacy compat router, `/healthz`, optional
+  static serving with SPA fallback. The fetch composition is exported as a
+  pure `createStudioDaemonFetch(deps)` so route dispatch is unit-testable
+  under vitest without `Bun.serve`.
+- `src/server/studio/legacyHttp.ts`: the 16 REST handlers re-expressed as
+  fetch handlers over the same engines — **byte-equal response bodies and
+  status codes**, including the parity pins: run-in-game status 404 echoes
+  `serverInstanceId`/`serverStartedAt`; save-deploy status 404 does not;
+  autoplay/save-deploy/run-in-game non-uniform codes; `live/status` returns
+  200 with per-field embedded `{error}`.
+- `vite.config.ts`: the `configureServer` plugin and every server-side
+  import are deleted; `server.proxy` forwards `/rpc` and `/api` to the
+  daemon. The config no longer drags `@civ7/direct-control` or any engine
+  code — config restarts become cheap and safe (the silent-restart-failure
+  trap documented in the dag-tab addendum loses its teeth).
+- `package.json`: `dev` → dev-live runner; `dev:frontend` → `vite`;
+  `dev:server` → daemon. `build`/`test`/`check` unchanged.
+- `studio.serverInfo.viteCommand` (contract: `z.string()`) is supplied by
+  the host: the daemon passes `"daemon"`. Verified no client branches on
+  the value (display/identity only); `serverInstanceId`/`startedAt` restart
+  detection is unaffected (identity now lives in the daemon process —
+  correct: it owns the operation stores the client reconciles against).
+
+## Legacy retirement list (checkpoint artifact — NOT auto-run)
+
+The compat surface below is pending an explicit user checkpoint before
+deletion. Consumer evidence (repo-wide sweep 2026-06-12): the studio client
+calls none of these (oRPC-only since P2); the single live consumer is
+`scripts/civ7-direct-control/verify-final-surface-parity.ts` (hits
+`GET /api/civ7/run-in-game/status`); `packages/civ7-direct-control/README.md`
+documents three of them as examples.
+
+| # | Legacy path | oRPC equivalent (`/rpc`) |
+| --- | --- | --- |
+| 1 | `GET /api/civ7/status` | `civ7.status` |
+| 2 | `GET /api/civ7/map-summary` | `civ7.mapSummary` |
+| 3 | `GET /api/civ7/gameinfo` | `civ7.gameInfo` |
+| 4 | `GET /api/civ7/live/status` | `civ7.live.status` |
+| 5 | `GET /api/civ7/live/snapshot` | `civ7.live.snapshot` |
+| 6 | `GET /api/civ7/live/entities` | `civ7.live.entities` |
+| 7 | `GET /api/civ7/live/gameinfo` | `civ7.live.gameInfo` |
+| 8 | `POST /api/civ7/autoplay` | `civ7.autoplay` |
+| 9 | `GET /api/studio/server-info` | `studio.serverInfo` |
+| 10 | `GET /api/civ7/setup-config` | `civ7.setupConfig` |
+| 11 | `GET /api/civ7/saved-configs` | `civ7.savedConfigs` |
+| 12 | `GET /api/civ7/setup-catalog` | `civ7.setupCatalog` |
+| 13 | `GET /api/civ7/run-in-game/status` | `runInGame.status` (+ parity script) |
+| 14 | `POST /api/civ7/run-in-game` | `runInGame.start` |
+| 15 | `GET /api/map-configs/status` | `mapConfigs.status` |
+| 16 | `POST /api/map-configs` | `mapConfigs.saveDeploy` |
+
+Retirement slice (post-checkpoint): delete `legacyHttp.ts` + its daemon
+mount + tests; update or retire the parity script's status poll.
+
+## Testing
+
+- Existing pins unchanged: `test/recipeDag/orpc.test.ts` (node transport
+  via the Connect shim), operation-state suites, watch-ignore pins.
+- New: daemon route-dispatch tests over `createStudioDaemonFetch` with
+  injected handlers (prefix routing, healthz, 404 fall-through, static
+  fallback); control fetch-adapter transport test (mirror of the recipe-DAG
+  one); legacy compat parity pins (404-echo asymmetry, non-uniform status
+  codes, `live/status` embedded-error 200); dev-live plan test
+  (`makeDevLivePlan` pure function: commands, ports, proxy env).
+- Live smoke (fresh processes, both run modes): `bun run dev` →
+  generation run completes; pipeline view loads the DAG through the proxy;
+  control readiness poll works; curl pins on `/healthz`, a legacy path, and
+  `studio.serverInfo`.
diff --git a/openspec/changes/mapgen-studio-bun-server/proposal.md b/openspec/changes/mapgen-studio-bun-server/proposal.md
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+# Studio server cutover — standalone Bun daemon owns the server surface
+
+## Why
+
+Today the Studio has no server process of its own: every server-side surface
+(the `@civ7/studio-server` `/rpc` mount, the control-oRPC mount at
+`/api/civ7/rpc`, the recipe-DAG mount at `/api/recipe-dag/rpc`, and 16
+hand-rolled legacy `/api/*` REST handlers) runs as Vite dev middleware, with
+the stateful engines (serialized operation queue, run-in-game + save/deploy
+operation stores, server instance identity) living at module scope inside
+`vite.config.ts`. Production is a static SPA with no server at all, so the
+dev semantics are the only semantics — and they are welded to the dev
+bundler. This was the planned P5a coexistence state; the P5b cutover
+(00-GOAL "Remaining (SUPERVISED)", FRAME §4.7 deferral, user go granted
+2026-06-11) moves the server surface onto a standalone Bun daemon and makes
+Vite frontend-only.
+
+Bun also dissolves a real defect class: `effect-orpc` ships TypeScript
+source as its package entry, which Node cannot load outside Vite's SSR
+pipeline — forcing the recipe-DAG mount through per-request `ssrLoadModule`
+(see `mapgen-studio-dag-tab` design addendum). Bun loads TS natively; the
+daemon imports the same fetch handler statically.
+
+## Target Authority Refs
+
+- `docs/projects/mapgen-studio-redesign/architecture/10-target-architecture.md`
+  (§1 server target + parity invariants, §7 do-not-break registry)
+- `docs/projects/mapgen-studio-redesign/00-GOAL.md` (P5b entry — supervised,
+  go granted)
+- `packages/studio-server/src/{index,handler}.ts` (A4-lite host seam:
+  fetch-adapter `createStudioRpcHandler`)
+- `openspec/changes/mapgen-studio-dag-tab/design.md` addendum (mount
+  constraints + research evidence: fetch handlers are the canonical
+  artifacts, Vite hosting was a dev-era necessity)
+- `tools/gt-stack-inspect` on `codex/gt-stack-inspect-dev-live-topology`
+  (prior-art daemon + dev-live runner + Vite `/rpc` proxy topology;
+  read-only reference — `codex/*` branches are never touched)
+
+## What Changes
+
+- **Engines move out of `vite.config.ts`** into
+  `apps/mapgen-studio/src/server/studio/engines.ts`: a
+  `createStudioEngines({ repoRoot })` factory owning the serialized
+  operation queue, both operation stores, the server instance identity, and
+  the five engine functions (autoplay, run-in-game start/status,
+  save-deploy start/status) — moved verbatim, behavior-parity hard core.
+  The `StudioServerContext` builder moves alongside as
+  `createStudioServerContext`. (This slice changes no topology: Vite still
+  hosts everything, now via the extracted module.)
+- **Control-oRPC mount converts to the fetch adapter**
+  (`@orpc/server/fetch`), mirroring the recipe-DAG mount's shape: canonical
+  fetch handler + thin Connect shim over the shared
+  `server/http/nodeWebBridge`. Path contract `/api/civ7/rpc` unchanged.
+- **Standalone Bun daemon** (`src/server/daemon/daemon.ts`): `Bun.serve`
+  hosting a fetch router that owns `/healthz`, `/rpc` (studio-server),
+  `/api/civ7/rpc` (control-oRPC), `/api/recipe-dag/rpc` (statically
+  imported — the `ssrLoadModule` constraint evaporates under Bun), the
+  legacy `/api/*` REST surface as a compat layer over the same engines, and
+  optional static `dist` serving (the production story's opening, not wired
+  to deploy in this change).
+- **Vite becomes frontend-only**: the `configureServer` plugin and all
+  server-side imports leave `vite.config.ts`; `server.proxy` forwards
+  `/rpc` and `/api` to the daemon. Dev topology: `bun run dev` runs a
+  dev-live runner that spawns the daemon (port 5174), waits for `/healthz`,
+  then spawns Vite (port 5173).
+- **Legacy `/api/*` REST handlers**: ported onto the daemon as a thin compat
+  module (same engines, same response bodies and status codes) so the
+  cutover lands with zero observable surface change. Their **retirement is
+  gated on an explicit user checkpoint** (supervision condition) and is NOT
+  part of this change's auto-run scope; the retirement list and consumer
+  evidence live in `design.md`.
+
+## Non-Goals
+
+- No retirement of the legacy REST surface without the user checkpoint.
+- No Railway/Caddy production deploy changes (the daemon's static serving
+  makes them possible later; wiring them is out of scope).
+- No contract changes to `@civ7/studio-server`, `@civ7/control-orpc`, or
+  the recipe-DAG router; no client-visible transport changes.
+- No re-implementation of engine logic — the engine bodies move verbatim.
+
+## Impact
+
+- Affected specs: `mapgen-studio`
+- Affected code: `apps/mapgen-studio/vite.config.ts` (shrinks to
+  frontend-only), `apps/mapgen-studio/src/server/studio/*` (new: engines,
+  context, legacy compat), `apps/mapgen-studio/src/server/daemon/*` (new:
+  daemon, dev-live runner), `apps/mapgen-studio/src/server/civ7ControlOrpc.ts`
+  (fetch adapter), `apps/mapgen-studio/package.json` (dev scripts),
+  `apps/mapgen-studio/test/devServer/*` + `test/server/*` (new pins)
diff --git a/openspec/changes/mapgen-studio-bun-server/specs/mapgen-studio/spec.md b/openspec/changes/mapgen-studio-bun-server/specs/mapgen-studio/spec.md
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+++ b/openspec/changes/mapgen-studio-bun-server/specs/mapgen-studio/spec.md
@@ -0,0 +1,75 @@
+## ADDED Requirements
+
+### Requirement: The Studio Server Surface Runs As A Standalone Bun Daemon
+
+The Studio's server surface SHALL be owned by a standalone Bun daemon
+process hosting the studio-server `/rpc` mount, the control-oRPC mount at
+`/api/civ7/rpc`, the recipe-DAG mount at `/api/recipe-dag/rpc`, and the
+legacy `/api/*` REST compat surface, with the Vite dev server reduced to a
+frontend-only role that proxies `/rpc` and `/api` to the daemon. All path
+contracts and client transports are unchanged by the cutover.
+
+#### Scenario: One-command dev runs both processes
+
+- **WHEN** the developer runs the studio dev script
+- **THEN** the daemon starts and reports healthy before Vite starts, the
+  app is served on the Vite port, and every `/rpc` and `/api` request is
+  answered by the daemon process
+
+#### Scenario: Recipe-DAG mount loads natively under Bun
+
+- **WHEN** the daemon serves a recipe-DAG RPC request
+- **THEN** the handler is a statically imported module (no SSR loader
+  indirection) and the response matches the previous Vite-hosted mount
+
+#### Scenario: Frontend-only Vite config
+
+- **WHEN** the Vite config is evaluated (dev or build)
+- **THEN** it imports no engine, direct-control, or server-handler modules
+  and registers no server middleware beyond the proxy
+
+### Requirement: Studio Server State Lives In One Process
+
+The Studio SHALL keep the serialized operation queue, the run-in-game and
+save/deploy operation stores, and the server instance identity in exactly
+one place — the daemon process — shared by every transport (oRPC mounts
+and legacy compat); no studio server state may live in the Vite process. The engine
+behaviors move verbatim: non-uniform error status codes are preserved
+per-procedure, run-in-game status 404 echoes the server instance identity
+while save/deploy status 404 does not, and `live/status` returns 200 with
+per-field embedded errors.
+
+#### Scenario: Both transports observe one queue
+
+- **WHEN** a run-in-game operation is active and a save/deploy request
+  arrives on either the oRPC mount or the legacy compat surface
+- **THEN** the request is rejected with the 409 dual-mutex semantics
+  naming the active operation
+
+#### Scenario: Restart detection identity
+
+- **WHEN** the daemon restarts and a client polls a stale run-in-game
+  request id
+- **THEN** the 404 response carries the new process's `serverInstanceId`
+  and `serverStartedAt`
+
+### Requirement: Legacy REST Surface Survives The Cutover Until The Retirement Checkpoint
+
+The legacy `/api/*` REST handlers SHALL remain available through the
+cutover as a daemon-hosted compat layer with response bodies and status
+codes identical to the Vite-hosted handlers, and SHALL NOT be retired
+without an explicit user-approved retirement decision recorded in this
+workstream.
+
+#### Scenario: Compat parity
+
+- **WHEN** a legacy endpoint is requested after the cutover
+- **THEN** the response status and body shape match the pre-cutover
+  Vite-hosted handler for the same engine state
+
+#### Scenario: Retirement is gated
+
+- **WHEN** the cutover slices land without a recorded user checkpoint
+  decision
+- **THEN** the compat surface is still mounted and the retirement remains
+  an open follow-up in the workstream record
diff --git a/openspec/changes/mapgen-studio-bun-server/tasks.md b/openspec/changes/mapgen-studio-bun-server/tasks.md
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+## 1. Frame
+
+- [ ] 1.1 Workstream record + proposal/design/tasks/spec deltas committed
+      (`design/bun-server-frame`), `--strict` valid.
+
+## 2. Engine extraction (`design/bun-server-engines`) — no topology change
+
+- [ ] 2.1 `src/server/studio/engines.ts`: `createStudioEngines({ repoRoot })`
+      — queue, both operation stores, instance identity, five engine fns
+      moved VERBATIM from `vite.config.ts`. No effect-orpc in its import
+      graph (config must stay node-evaluable).
+- [ ] 2.2 `src/server/studio/context.ts`: `createStudioServerContext`
+      (moved `createStudioServerContextForApp`; non-uniform error mapping
+      intact).
+- [ ] 2.3 `vite.config.ts` consumes the extracted modules at module scope;
+      legacy handlers and all three mounts behave identically.
+- [ ] 2.4 Gates: tsc, studio tests, mod tests, build + worker bundle,
+      fresh-process live smoke (run loop + pipeline view + readiness poll).
+
+## 3. Control-oRPC fetch adapter (`design/bun-control-fetch`)
+
+- [ ] 3.1 `civ7ControlOrpc.ts` → canonical fetch handler
+      (`@orpc/server/fetch`) + Connect shim over `nodeWebBridge`,
+      mirroring `recipeDag/orpc.ts`; path contract unchanged.
+- [ ] 3.2 Transport test (node:http + shim → fetch handler), mirroring the
+      recipe-DAG transport pins.
+- [ ] 3.3 Gates: tsc, studio tests, live smoke (readiness/control poll).
+
+## 4. Daemon + cutover (`design/bun-server-daemon`)
+
+- [ ] 4.1 `src/server/daemon/daemon.ts`: arg parsing, one engines
+      instance, `createStudioDaemonFetch(deps)` (pure, testable) routing
+      `/healthz`, `/rpc`, `/api/civ7/rpc`, `/api/recipe-dag/rpc` (static
+      import), legacy compat, optional static assets; `Bun.serve` entry.
+- [ ] 4.2 `src/server/studio/legacyHttp.ts`: 16 REST handlers as fetch
+      adapters over the shared engines — identical bodies/status codes
+      (404-echo asymmetry, non-uniform codes, live/status embedded-error
+      200).
+- [ ] 4.3 `src/server/daemon/devLive.ts`: spawn daemon → wait `/healthz` →
+      spawn Vite; signal forwarding; `makeDevLivePlan` pure.
+- [ ] 4.4 `vite.config.ts`: delete the server plugin + server imports; add
+      `server.proxy` for `/rpc` + `/api` (`STUDIO_DEV_RPC_TARGET`
+      override). `package.json`: `dev` → runner, `dev:frontend`,
+      `dev:server`.
+- [ ] 4.5 Tests: daemon route dispatch; legacy compat parity pins;
+      dev-live plan; existing transport/operation pins green unchanged.
+- [ ] 4.6 Gates: tsc, studio tests, mod tests, build + worker bundle.
+- [ ] 4.7 Live verification on FRESH processes: `bun run dev` boots both;
+      generation run completes; pipeline view loads DAG via proxy; control
+      readiness poll works; curl pins (`/healthz`, one legacy path,
+      `studio.serverInfo`); dark theme visual unchanged.
+
+## 5. Retirement checkpoint (SUPERVISED — not auto-run)
+
+- [ ] 5.1 Present the retirement list (design.md table + consumer
+      evidence) to the user; record the decision in the workstream record.
+- [ ] 5.2 (post-approval) `design/bun-legacy-retire`: delete
+      `legacyHttp.ts` + mount + compat tests; update
+      `scripts/civ7-direct-control/verify-final-surface-parity.ts`.
diff --git a/openspec/changes/mapgen-studio-bun-server/workstream/workstream-record.md b/openspec/changes/mapgen-studio-bun-server/workstream/workstream-record.md
new file mode 100644
index 0000000000..d0ea9e4cec
--- /dev/null
+++ b/openspec/changes/mapgen-studio-bun-server/workstream/workstream-record.md
@@ -0,0 +1,50 @@
+# Systematic Workstream Record
+
+## Frame
+
+- Objective: Move the Studio's server surface off the Vite dev middleware
+  onto a standalone Bun daemon (P5b cutover, user go granted 2026-06-11),
+  making Vite frontend-only and dissolving the effect-orpc TS-source
+  loading constraint — with zero observable behavior change for the app or
+  the legacy REST surface.
+- Future state: `bun run dev` runs a daemon (owning every `/rpc` + `/api`
+  byte and all server state) plus a Vite frontend that proxies to it; the
+  daemon can also serve the built SPA, opening a real production server
+  story.
+- Non-goals: legacy retirement without the user checkpoint; deploy/Caddy
+  changes; any contract or client transport change; engine rewrites.
+- Hard core: behavior parity (run/poll/localStorage/transport semantics);
+  arch/10 §1 parity invariants (non-uniform status codes, 404-echo
+  asymmetry, live/status embedded-error 200, `assertNoRawControlFields`,
+  serialized queue + dual mutex, fingerprint dedup→202); path contracts
+  (`/rpc`, `/api/civ7/rpc`, `/api/recipe-dag/rpc`); single engine instance
+  per server process.
+- Exterior: `codex/*` branches (read-only prior art); placement-stack
+  resources vertical; the live-control lane's stack.
+
+## Authority
+
+- `docs/projects/mapgen-studio-redesign/architecture/10-target-architecture.md`
+  (§1 server target, §7 do-not-break registry)
+- `docs/projects/mapgen-studio-redesign/00-GOAL.md` (P5b — supervised)
+- `packages/studio-server/src/{index,handler}.ts` (A4-lite fetch seam)
+- `openspec/changes/mapgen-studio-dag-tab/design.md` addendum (mount
+  research: fetch handlers canonical, Vite hosting dev-era)
+- `tools/gt-stack-inspect` @ `codex/gt-stack-inspect-dev-live-topology`
+  (daemon + dev-live + proxy blueprint)
+
+## Plan
+
+- Phase 1 (`design/bun-server-frame`): this record + proposal/design/tasks
+  + spec deltas, `--strict` valid.
+- Phase 2 (`design/bun-server-engines`): engine extraction, no topology
+  change.
+- Phase 3 (`design/bun-control-fetch`): control mount → fetch adapter.
+- Phase 4 (`design/bun-server-daemon`): daemon + dev-live + Vite
+  frontend-only cutover + legacy compat port.
+- Phase 5 (checkpoint, SUPERVISED): retirement decision; then
+  `design/bun-legacy-retire`.
+
+## Evidence
+
+- (per phase, appended as slices close)