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+Title: App-wide Settings Page — Design
+
+Summary
+
+Add an admin-only Settings page where operators can change app-wide configuration that affects server functions and runtime behavior (feature flags, execution modes, thresholds, API keys for integrations). Settings are persisted in the database and reflected immediately via an in-process cache + event broadcaster so server functions read updated values without restart.
+
+Goals
+
+- Provide a single UI for operators to view and change app-wide settings.
+- Persist settings reliably and safely (DB-backed) and version/track changes.
+- Ensure changes propagate to server functions quickly and predictably.
+- Secure the UI and APIs (admin-only).
+- Test coverage (unit + E2E).
+
+Chosen approach (Recommended)
+
+DB-backed settings with a Settings Service:
+- Persist settings in a new Prisma model/table (AppSetting).
+- Expose server-side SettingsService with get/set/getAll, an in-memory cache, and an EventEmitter to notify subscribers on change.
+- Admin UI: route at /settings (app/routes/settings.tsx) with a guarded admin page to edit values.
+- Server functions import SettingsService.get("key") or subscribe to change events when they need dynamic behavior.
+
+Why DB-backed
+
+- Atomic persistence, multi-instance safe when coupled with a small invalidation strategy (see below).
+- Auditable (store updatedAt, updatedBy, description).
+- Fits existing repo (prisma/ exists).
+
+Data model (Prisma example)
+
+model AppSetting {
+  id         Int      @id @default(autoincrement())
+  key        String   @unique
+  value      Json
+  description String?
+  updatedAt  DateTime @updatedAt
+  updatedBy  String?  // optional admin id/email
+}
+
+Backend: SettingsService
+
+- File: app/lib/settings.server.ts
+- Exports:
+  - async getSetting(key: string): Promise<any>
+  - async setSetting(key: string, value: any, opts?: { updatedBy?: string })
+  - async getAllSettings(): Promise<Record<string, any>>
+  - subscribe(cb: (key,value)=>void) => unsubscribe
+
+Implementation notes:
+- On startup, load all settings into an in-memory Map cache.
+- getSetting reads from cache (fast). setSetting updates DB then cache and emits event.
+- To support multiple instances, setSetting also writes a lightweight "manifest" or uses DB trigger; for now plan: setSetting updates DB and callers of getSetting should tolerate eventual consistency, or a periodic poll (1s) or Redis pub/sub can be added later.
+
+API endpoints
+
+- GET /api/admin/settings -> list all settings (admin-only)
+- PUT /api/admin/settings/:key -> update a single setting (admin-only)
+- POST /api/admin/settings -> create/replace settings (admin-only)
+
+Server route files: app/routes/api/admin/settings/index.ts (GET, POST), app/routes/api/admin/settings/[key].ts (PUT)
+
+Frontend: Settings page
+
+- File: app/routes/settings.tsx (route available only to admins).
+- UI: table/list of settings (key, value editor (text/json/toggle), description, last updated, updatedBy) and a Save button.
+- Support types: boolean toggles, numeric inputs, string inputs, JSON editor for advanced values.
+- Client calls API endpoints and displays toasts on success/failure.
+- When updated, UI will optimistically update local state; eventual confirmation comes from API.
+
+Security
+
+- Protect API endpoints and the /settings route with admin guard. If the app has user sessions with roles, require isAdmin. Otherwise gate with an env-based ADMIN_TOKEN for now.
+- Validate input server-side: schema for known keys; generic JSON allowed for advanced keys but validated.
+
+Testing
+
+- Unit tests for SettingsService (get/set/cache behavior). New tests under app/lib/__tests__.
+- Integration test for API endpoints (app/routes/api/admin/settings tests).
+- E2E Playwright test: toggling a setting that affects behavior (e.g., feature flag that hides/shows a UI element) should reflect immediately.
+
+Migration
+
+- Add Prisma model and generate migration: `npx prisma migrate dev --name add_app_setting`
+- Run `npx prisma generate` and deploy migration.
+
+Rollout
+
+- Start with critical settings (e.g., ENABLE_TRADING=false, ANALYSIS_BACKGROUND=true, PRICE_STREAM_URL).
+- Add a feature flag toggle to hide advanced JSON edits behind "advanced" switch.
+
+Next steps after approval
+
+1) Write this spec file into docs (done). (current step)
+2) Create PR: add Prisma model, SettingsService, API routes, UI route + components, tests.
+3) Run migrations locally and in staging, verify behavior.
+4) Add audit logging for changes.
+
+Notes
+
+- Multi-instance real-time propagation: simple approach (polling or Redis pub/sub) is deferred to future work if needed.
+- Keep settings small and typed where possible to avoid fragile JSON edits.
+
+Files to create/change (implementation plan will enumerate exact edits)
+
+- prisma/schema.prisma (add AppSetting model)
+- app/lib/settings.server.ts (service)
+- app/routes/api/admin/settings/index.ts
+- app/routes/api/admin/settings/[key].ts
+- app/routes/settings.tsx
+- tests: unit + integration + e2e
+
+Please review and confirm; after approval I'll: 1) commit this spec, 2) produce an implementation plan (writing-plans skill) and then implement if you ask.