diff --git a/package.json b/package.json
index 2d8f20a..e3b0d18 100644
--- a/package.json
+++ b/package.json
@@ -2,9 +2,10 @@
   "name": "pediatric-ai-scribe",
   "version": "6.21.0",
   "description": "AI-powered pediatric clinical documentation platform",
-  "main": "server.js",
+  "main": "dist/server.js",
   "scripts": {
-    "start": "node server.js",
+    "start": "node dist/server.js",
+    "prebuild": "rm -rf dist",
     "build": "tsc",
     "typecheck": "tsc --noEmit",
     "dev": "ts-node-dev --respawn --transpile-only server.ts",
diff --git a/server.js b/server.ts
similarity index 100%
rename from server.js
rename to server.ts
diff --git a/shared/types.ts b/shared/types.ts
new file mode 100644
index 0000000..802b8e2
--- /dev/null
+++ b/shared/types.ts
@@ -0,0 +1,234 @@
+// ============================================================
+// SHARED TYPES — consumed by both server (src/routes/*.ts) and
+// client (client/src/*). A response-shape change here breaks the
+// build on both sides until they agree.
+//
+// This is the single most important file in the TypeScript
+// migration. Three of the bugs we hit before this point were
+// response-shape mismatches (refine returned `content` vs
+// `refined`, sick-visit endpoint path mismatch, hospital-course
+// key mismatch). Typing the wire protocol makes them compile-time
+// errors.
+//
+// Keep this file strictly about wire protocol — no DB row shapes,
+// no server-internal helpers. Anything that crosses the network.
+// ============================================================
+
+// ── Envelope ─────────────────────────────────────────────────
+// Every route returns either `{success: true, ...extraFields}` or
+// `{success: false, error: string}`. The generic `T` is the shape
+// of the extra fields on success. Client code does:
+//   const r: ApiResponse<HpiOk> = await fetch(...).then(r => r.json());
+//   if (r.success) console.log(r.hpi);
+//   else           showToast(r.error);
+export interface ApiErr {
+  success: false;
+  error: string;
+}
+export type ApiResponse<T> = ({ success: true } & T) | ApiErr;
+
+// Model tag accompanies every AI response — LiteLLM pass-through.
+export interface WithModel {
+  model: string;
+}
+
+// ── AI generation responses ──────────────────────────────────
+// Keys match exactly what each route returns today. Do not rename
+// without updating the server-side res.json() call in the same commit.
+
+// /api/generate-hpi-encounter
+// /api/generate-hpi-dictation
+export interface HpiOk extends WithModel {
+  hpi: string;
+}
+
+// /api/generate-soap
+export interface SoapOk extends WithModel {
+  soap: string;
+}
+
+// /api/sick-visit/note   (NOT /api/generate-sick-visit — that path does not exist)
+// /api/well-visit/note
+export interface VisitNoteOk extends WithModel {
+  note: string;
+}
+
+// /api/generate-hospital-course
+export interface HospitalCourseOk extends WithModel {
+  hospitalCourse: string;
+  format?: string;
+}
+
+// /api/generate-chart-review
+export interface ChartReviewOk extends WithModel {
+  review: string;
+}
+
+// /api/generate-pe-narrative
+export interface PeNarrativeOk extends WithModel {
+  narrative: string;
+  summary: {
+    normal: number;
+    abnormal: number;
+    notAssessed: number;
+  };
+}
+
+// /api/generate-milestone-narrative
+export interface MilestoneNarrativeOk extends WithModel {
+  narrative: string;
+  summary: {
+    achieved: number;
+    notAchieved: number;
+    notAssessed: number;
+  };
+}
+
+// /api/generate-milestone-summary
+export interface MilestoneSummaryOk extends WithModel {
+  summary: string;
+}
+
+// /api/well-visit/shadess
+export interface ShadessOk extends WithModel {
+  assessment: string;
+}
+
+// /api/refine
+export interface RefineOk extends WithModel {
+  refined: string;
+}
+
+// /api/shorten  (via refine.js router)
+export interface ShortenOk extends WithModel {
+  shortened: string;
+}
+
+// /api/clarify and /hospital-course/clarify
+export interface ClarifyOk extends WithModel {
+  questions: string;
+}
+
+// /api/suggest-billing-codes
+export interface BillingCodesOk extends WithModel {
+  icd10: Array<{ code: string; description: string; reason?: string }>;
+  cpt: Array<{ code: string; description: string; reason?: string }>;
+}
+
+// /api/transcribe
+export interface TranscribeOk {
+  text: string;
+  provider: string;
+  duration: number;
+}
+
+// /api/tts
+export interface TtsOk {
+  audioBase64: string;
+}
+
+// /api/models
+export interface ModelsOk {
+  models: Array<{ id: string; label?: string }>;
+}
+
+// ── Auth ─────────────────────────────────────────────────────
+export interface AuthUser {
+  id: number;
+  email: string;
+  name: string;
+  role?: string;
+  isVerified?: boolean;
+  has2FA?: boolean;
+}
+
+// /api/auth/login (two-phase: may also return requires2FA / needsVerification)
+export interface LoginOk {
+  token: string;
+  user: AuthUser;
+  sessionId?: string;
+}
+
+export interface LoginRequires2FA {
+  success: true;
+  requires2FA: true;
+}
+
+export interface LoginNeedsVerification {
+  success: true;
+  needsVerification: true;
+}
+
+// /api/auth/me
+export interface MeOk {
+  user: AuthUser;
+}
+
+// ── Sessions ─────────────────────────────────────────────────
+export interface SessionRow {
+  id: string;
+  userAgent?: string;
+  ipAddress?: string;
+  createdAt: string;
+  lastUsedAt?: string;
+}
+export interface SessionsOk {
+  sessions: SessionRow[];
+  currentSessionId: string | null;
+}
+
+// ── Extensions (pagers/directory) ────────────────────────────
+export interface Extension {
+  id: number;
+  location: string;
+  name: string;
+  number: string;
+  type: 'extension' | 'pager';
+  notes?: string;
+  deletedAt?: string | null;
+}
+export interface ExtensionsListOk {
+  items: Extension[];
+}
+
+// ── Memories (saved templates / style hints) ─────────────────
+export interface Memory {
+  id: number;
+  category: string;
+  name: string;
+  content: string;
+}
+export interface MemoriesListOk {
+  items: Memory[];
+}
+
+// ── Learning hub ─────────────────────────────────────────────
+export interface LearningContentItem {
+  id: number | string;
+  slug?: string;
+  title: string;
+  category?: string;
+  excerpt?: string;
+  body?: string;
+}
+export interface LearningFeedOk {
+  content: LearningContentItem[];
+  total?: number;
+}
+
+// ── Encounters (saved drafts) ────────────────────────────────
+export interface EncounterSummary {
+  id: number;
+  label: string;
+  type: 'encounter' | 'dictation' | 'hospital' | 'chart' | 'wellvisit' | 'sickvisit' | 'soap';
+  createdAt: string;
+  updatedAt: string;
+}
+export interface EncountersListOk {
+  items: EncounterSummary[];
+}
+
+// ── Health ───────────────────────────────────────────────────
+export interface HealthOk {
+  ok: boolean;
+}
diff --git a/tsconfig.json b/tsconfig.json
index bde40cd..0ecf971 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -23,6 +23,7 @@
     }
   },
   "include": [
+    "server.ts",
     "server.js",
     "src/**/*.js",
     "src/**/*.ts",