diff --git a/package.json b/package.json
index d03438f..0af1caf 100644
--- a/package.json
+++ b/package.json
@@ -1,27 +1,28 @@
 {
-  "name": "debug-api",
-  "module": "index.ts",
-  "type": "module",
-  "devDependencies": {
-    "@biomejs/biome": "^1.8.3",
-    "@types/bun": "latest",
-    "@types/react": "18.3.4",
-    "next": "^14.2.5",
-    "redaxios": "^0.5.1"
-  },
-  "peerDependencies": {
-    "typescript": "^5.0.0"
+  "name": "fake-algora",
+  "version": "1.0.0",
+  "description": "A fake/mock Algora API server for testing bounty integrations",
+  "main": "dist/index.js",
+  "scripts": {
+    "build": "tsc",
+    "start": "node dist/index.js",
+    "dev": "ts-node-dev --respawn --transpile-only src/index.ts",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "dependencies": {
-    "winterspec": "^0.0.86",
-    "zod": "^3.23.8",
-    "zustand": "^4.5.5",
-    "zustand-hoist": "^2.0.1"
+    "express": "^4.18.2",
+    "zod": "^3.22.4",
+    "uuid": "^9.0.0"
   },
-  "scripts": {
-    "start": "bun run dev",
-    "dev": "winterspec dev",
-    "build": "winterspec bundle -o dist/bundle.js",
-    "next:dev": "next dev"
+  "devDependencies": {
+    "@types/express": "^4.17.21",
+    "@types/node": "^20.11.5",
+    "@types/uuid": "^9.0.7",
+    "ts-node-dev": "^2.0.0",
+    "typescript": "^5.3.3",
+    "vitest": "^1.2.2",
+    "supertest": "^6.3.4",
+    "@types/supertest": "^6.0.2"
   }
 }
diff --git a/src/app.ts b/src/app.ts
new file mode 100644
index 0000000..e309eb9
--- /dev/null
+++ b/src/app.ts
@@ -0,0 +1,27 @@
+import express from "express"
+import { bountiesRouter } from "./routes/bounties"
+import { paymentsRouter } from "./routes/payments"
+import { errorHandler, notFound } from "./middleware/errorHandler"
+
+export function createApp(): express.Application {
+  const app = express()
+
+  // ─── Global middleware ──────────────────────────────────────────────────────
+  app.use(express.json())
+  app.use(express.urlencoded({ extended: true }))
+
+  // ─── Health check ───────────────────────────────────────────────────────────
+  app.get("/health", (_req, res) => {
+    res.json({ status: "ok", service: "fake-algora" })
+  })
+
+  // ─── API routes ─────────────────────────────────────────────────────────────
+  app.use("/api/bounties", bountiesRouter)
+  app.use("/api/payments", paymentsRouter)
+
+  // ─── Error handling ─────────────────────────────────────────────────────────
+  app.use(notFound)
+  app.use(errorHandler)
+
+  return app
+}
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..672bebd
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,15 @@
+import { createApp } from "./app"
+
+const PORT = process.env.PORT ? parseInt(process.env.PORT, 10) : 3000
+
+const app = createApp()
+
+app.listen(PORT, () => {
+  console.log(`🚀 fake-algora server running on http://localhost:${PORT}`)
+  console.log(`   Health: GET  /health`)
+  console.log(`   Bounties: GET|POST /api/bounties`)
+  console.log(`             GET      /api/bounties/:id`)
+  console.log(`   Payments: POST     /api/payments`)
+  console.log(`             GET      /api/payments`)
+  console.log(`             GET      /api/payments/:id`)
+})
diff --git a/src/middleware/errorHandler.ts b/src/middleware/errorHandler.ts
new file mode 100644
index 0000000..41f15ac
--- /dev/null
+++ b/src/middleware/errorHandler.ts
@@ -0,0 +1,44 @@
+import type { Request, Response, NextFunction } from "express"
+import type { ApiErrorResponse } from "../types"
+
+export interface AppError extends Error {
+  statusCode?: number
+  code?: string
+}
+
+export function errorHandler(
+  err: AppError,
+  _req: Request,
+  res: Response,
+  _next: NextFunction
+): void {
+  const statusCode = err.statusCode ?? 500
+  const body: ApiErrorResponse = {
+    error: {
+      message: err.message ?? "Internal server error",
+      code: err.code ?? "INTERNAL_ERROR",
+    },
+  }
+  res.status(statusCode).json(body)
+}
+
+export function notFound(_req: Request, res: Response): void {
+  const body: ApiErrorResponse = {
+    error: {
+      message: "Route not found",
+      code: "NOT_FOUND",
+    },
+  }
+  res.status(404).json(body)
+}
+
+export function createError(
+  message: string,
+  statusCode: number,
+  code: string
+): AppError {
+  const err: AppError = new Error(message)
+  err.statusCode = statusCode
+  err.code = code
+  return err
+}
diff --git a/src/routes/bounties.test.ts b/src/routes/bounties.test.ts
new file mode 100644
index 0000000..cf0eb4d
--- /dev/null
+++ b/src/routes/bounties.test.ts
@@ -0,0 +1,99 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import request from "supertest";
+import { app } from "../app";
+import { store } from "../store";
+
+beforeEach(() => {
+  store.reset();
+});
+
+// ── /bounties ──────────────────────────────────────────────────────────────
+
+describe("GET /bounties", () => {
+  it("returns the seeded bounties", async () => {
+    const res = await request(app).get("/bounties");
+    expect(res.status).toBe(200);
+    expect(Array.isArray(res.body.data)).toBe(true);
+    expect(res.body.data.length).toBeGreaterThanOrEqual(3);
+  });
+
+  it("includes expected fields on each bounty", async () => {
+    const res = await request(app).get("/bounties");
+    const bounty = res.body.data[0];
+    expect(bounty).toHaveProperty("id");
+    expect(bounty).toHaveProperty("title");
+    expect(bounty).toHaveProperty("amount_usd");
+    expect(bounty).toHaveProperty("currency");
+    expect(bounty).toHaveProperty("status");
+  });
+});
+
+describe("GET /bounties/:id", () => {
+  it("returns a single bounty by id", async () => {
+    const listRes = await request(app).get("/bounties");
+    const { id } = listRes.body.data[0];
+
+    const res = await request(app).get(`/bounties/${id}`);
+    expect(res.status).toBe(200);
+    expect(res.body.data.id).toBe(id);
+  });
+
+  it("returns 404 for an unknown id", async () => {
+    const res = await request(app).get("/bounties/does-not-exist");
+    expect(res.status).toBe(404);
+    expect(res.body).toHaveProperty("error");
+  });
+});
+
+describe("POST /bounties", () => {
+  it("creates a new bounty and returns 201", async () => {
+    const payload = {
+      title: "New bounty",
+      description: "A fresh bounty created in tests",
+      amount_usd: 200,
+      currency: "USD",
+    };
+    const res = await request(app).post("/bounties").send(payload);
+    expect(res.status).toBe(201);
+    expect(res.body.data).toMatchObject({
+      title: payload.title,
+      description: payload.description,
+      amount_usd: payload.amount_usd,
+      currency: payload.currency,
+      status: "open",
+    });
+    expect(res.body.data).toHaveProperty("id");
+    expect(res.body.data).toHaveProperty("created_at");
+  });
+
+  it("returns 400 when required fields are missing", async () => {
+    const res = await request(app).post("/bounties").send({ title: "Only title" });
+    expect(res.status).toBe(400);
+    expect(res.body).toHaveProperty("error");
+    expect(res.body).toHaveProperty("details");
+  });
+
+  it("returns 400 when amount_usd is not a positive number", async () => {
+    const res = await request(app).post("/bounties").send({
+      title: "Bad amount",
+      description: "desc",
+      amount_usd: -10,
+      currency: "USD",
+    });
+    expect(res.status).toBe(400);
+    expect(res.body).toHaveProperty("error");
+  });
+
+  it("persists the new bounty so it appears in GET /bounties", async () => {
+    await request(app).post("/bounties").send({
+      title: "Persisted bounty",
+      description: "Should show up in list",
+      amount_usd: 50,
+      currency: "USD",
+    });
+
+    const listRes = await request(app).get("/bounties");
+    const titles = listRes.body.data.map((b: { title: string }) => b.title);
+    expect(titles).toContain("Persisted bounty");
+  });
+});
diff --git a/src/routes/bounties.ts b/src/routes/bounties.ts
new file mode 100644
index 0000000..fa16826
--- /dev/null
+++ b/src/routes/bounties.ts
@@ -0,0 +1,40 @@
+import { Router } from "express";
+import { z } from "zod";
+import { store } from "../store";
+
+export const bountiesRouter = Router();
+
+const CreateBountySchema = z.object({
+  title: z.string().min(1),
+  description: z.string().min(1),
+  amount_usd: z.number().positive(),
+  currency: z.string().min(1).default("USD"),
+  recipient_username: z.string().optional(),
+});
+
+/** GET /bounties — list all bounties */
+bountiesRouter.get("/", (_req, res) => {
+  res.json({ data: store.listBounties() });
+});
+
+/** GET /bounties/:id — get a single bounty */
+bountiesRouter.get("/:id", (req, res) => {
+  const bounty = store.getBounty(req.params.id);
+  if (!bounty) {
+    return res.status(404).json({ error: "Bounty not found" });
+  }
+  return res.json({ data: bounty });
+});
+
+/** POST /bounties — create a new bounty */
+bountiesRouter.post("/", (req, res) => {
+  const result = CreateBountySchema.safeParse(req.body);
+  if (!result.success) {
+    return res.status(400).json({
+      error: "Invalid request body",
+      details: result.error.format(),
+    });
+  }
+  const bounty = store.createBounty(result.data);
+  return res.status(201).json({ data: bounty });
+});
diff --git a/src/routes/payments.test.ts b/src/routes/payments.test.ts
new file mode 100644
index 0000000..a56c3a0
--- /dev/null
+++ b/src/routes/payments.test.ts
@@ -0,0 +1,166 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import request from "supertest";
+import { app } from "../app";
+import { store } from "../store";
+
+beforeEach(() => {
+  store.reset();
+});
+
+// ── helpers ────────────────────────────────────────────────────────────────
+
+/** Create a bounty via the API and return it. */
+async function createBounty(overrides: Partial<{
+  title: string;
+  description: string;
+  amount_usd: number;
+  currency: string;
+  recipient_username: string;
+}> = {}) {
+  const payload = {
+    title: "Test bounty",
+    description: "A bounty for testing payments",
+    amount_usd: 100,
+    currency: "USD",
+    ...overrides,
+  };
+  const res = await request(app).post("/bounties").send(payload);
+  expect(res.status).toBe(201);
+  return res.body.data;
+}
+
+// ── GET /payments ──────────────────────────────────────────────────────────
+
+describe("GET /payments", () => {
+  it("returns an empty list when no payments exist", async () => {
+    const res = await request(app).get("/payments");
+    expect(res.status).toBe(200);
+    expect(res.body.data).toEqual([]);
+  });
+
+  it("lists payments after one has been sent", async () => {
+    const bounty = await createBounty({ recipient_username: "alice" });
+    await request(app).post("/payments/send").send({ bounty_id: bounty.id });
+
+    const res = await request(app).get("/payments");
+    expect(res.status).toBe(200);
+    expect(res.body.data.length).toBe(1);
+  });
+});
+
+// ── GET /payments/:id ──────────────────────────────────────────────────────
+
+describe("GET /payments/:id", () => {
+  it("returns a payment by id", async () => {
+    const bounty = await createBounty({ recipient_username: "carol" });
+    const sendRes = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+    const paymentId: string = sendRes.body.data.id;
+
+    const res = await request(app).get(`/payments/${paymentId}`);
+    expect(res.status).toBe(200);
+    expect(res.body.data.id).toBe(paymentId);
+  });
+
+  it("returns 404 for an unknown payment id", async () => {
+    const res = await request(app).get("/payments/does-not-exist");
+    expect(res.status).toBe(404);
+    expect(res.body).toHaveProperty("error");
+  });
+});
+
+// ── POST /payments/send ────────────────────────────────────────────────────
+
+describe("POST /payments/send", () => {
+  it("creates a payment and marks the bounty as paid", async () => {
+    const bounty = await createBounty({ recipient_username: "dave" });
+
+    const res = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+
+    expect(res.status).toBe(201);
+    expect(res.body.data).toMatchObject({
+      bounty_id: bounty.id,
+      amount_usd: bounty.amount_usd,
+      currency: bounty.currency,
+      recipient_username: "dave",
+    });
+    expect(res.body.data).toHaveProperty("id");
+    expect(res.body.data).toHaveProperty("created_at");
+
+    // The bounty should now be marked as paid
+    const bountyRes = await request(app).get(`/bounties/${bounty.id}`);
+    expect(bountyRes.body.data.status).toBe("paid");
+  });
+
+  it("derives amount/currency from the bounty (not the request body)", async () => {
+    const bounty = await createBounty({
+      recipient_username: "eve",
+      amount_usd: 250,
+      currency: "USD",
+    });
+
+    const res = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+
+    expect(res.status).toBe(201);
+    expect(res.body.data.amount_usd).toBe(250);
+    expect(res.body.data.currency).toBe("USD");
+    expect(res.body.data.recipient_username).toBe("eve");
+  });
+
+  it("returns 400 when bounty_id is missing", async () => {
+    const res = await request(app).post("/payments/send").send({});
+    expect(res.status).toBe(400);
+    expect(res.body).toHaveProperty("error");
+    expect(res.body).toHaveProperty("details");
+  });
+
+  it("returns 404 when the bounty does not exist", async () => {
+    const res = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: "nonexistent-id" });
+    expect(res.status).toBe(404);
+    expect(res.body).toHaveProperty("error");
+  });
+
+  it("returns 422 when the bounty has no recipient assigned", async () => {
+    // Create a bounty WITHOUT a recipient_username
+    const bounty = await createBounty();
+
+    const res = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+
+    expect(res.status).toBe(422);
+    expect(res.body).toHaveProperty("error");
+  });
+
+  it("returns 409 when the bounty has already been paid (double-payment guard)", async () => {
+    const bounty = await createBounty({ recipient_username: "frank" });
+
+    // First payment — should succeed
+    const first = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+    expect(first.status).toBe(201);
+
+    // Second payment — should be rejected
+    const second = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: bounty.id });
+    expect(second.status).toBe(409);
+    expect(second.body).toHaveProperty("error");
+  });
+
+  it("also rejects payment for a seeded bounty that is already paid", async () => {
+    // seed data includes bounty-seed-3 with status "paid"
+    const res = await request(app)
+      .post("/payments/send")
+      .send({ bounty_id: "bounty-seed-3" });
+    expect(res.status).toBe(409);
+  });
+});
diff --git a/src/routes/payments.ts b/src/routes/payments.ts
new file mode 100644
index 0000000..e9c82c2
--- /dev/null
+++ b/src/routes/payments.ts
@@ -0,0 +1,78 @@
+import { Router } from "express";
+import { z } from "zod";
+import { store } from "../store";
+
+export const paymentsRouter = Router();
+
+/** GET /payments — list all payments */
+paymentsRouter.get("/", (_req, res) => {
+  res.json({ data: store.listPayments() });
+});
+
+/** GET /payments/:id — get a single payment */
+paymentsRouter.get("/:id", (req, res) => {
+  const payment = store.getPayment(req.params.id);
+  if (!payment) {
+    return res.status(404).json({ error: "Payment not found" });
+  }
+  return res.json({ data: payment });
+});
+
+const SendPaymentSchema = z.object({
+  bounty_id: z.string().min(1),
+});
+
+/**
+ * POST /payments/send
+ *
+ * Sends a payment for the given bounty. All payment fields
+ * (amount_usd, currency, recipient_username) are derived from the
+ * bounty record to prevent inconsistent data.
+ *
+ * Rules:
+ *  - The bounty must exist.
+ *  - The bounty must have a recipient_username assigned.
+ *  - The bounty must not already be paid (idempotency guard).
+ *  - On success the bounty status is updated to "paid".
+ */
+paymentsRouter.post("/send", (req, res) => {
+  const result = SendPaymentSchema.safeParse(req.body);
+  if (!result.success) {
+    return res.status(400).json({
+      error: "Invalid request body",
+      details: result.error.format(),
+    });
+  }
+
+  const { bounty_id } = result.data;
+
+  const bounty = store.getBounty(bounty_id);
+  if (!bounty) {
+    return res.status(404).json({ error: "Bounty not found" });
+  }
+
+  if (!bounty.recipient_username) {
+    return res
+      .status(422)
+      .json({ error: "Bounty has no recipient assigned; cannot send payment" });
+  }
+
+  if (bounty.status === "paid") {
+    return res
+      .status(409)
+      .json({ error: "Payment already sent for this bounty" });
+  }
+
+  // Derive all monetary / recipient fields directly from the bounty
+  const payment = store.createPayment({
+    bounty_id,
+    amount_usd: bounty.amount_usd,
+    currency: bounty.currency,
+    recipient_username: bounty.recipient_username,
+  });
+
+  // Mark the bounty as paid
+  store.updateBountyStatus(bounty_id, "paid");
+
+  return res.status(201).json({ data: payment });
+});
diff --git a/src/store.ts b/src/store.ts
new file mode 100644
index 0000000..1266a4d
--- /dev/null
+++ b/src/store.ts
@@ -0,0 +1,138 @@
+import { randomUUID } from "crypto";
+import type { Bounty, BountyStatus, Payment } from "./types";
+
+interface CreateBountyInput {
+  title: string;
+  description: string;
+  amount_usd: number;
+  currency: string;
+  recipient_username?: string;
+}
+
+interface CreatePaymentInput {
+  bounty_id: string;
+  amount_usd: number;
+  currency: string;
+  recipient_username: string;
+}
+
+class Store {
+  private bounties: Map<string, Bounty> = new Map();
+  private payments: Map<string, Payment> = new Map();
+
+  constructor() {
+    this.seed();
+  }
+
+  private seed() {
+    const now = new Date().toISOString();
+    const seedBounties: Bounty[] = [
+      {
+        id: "bounty-seed-1",
+        title: "Fix login bug",
+        description: "The login page throws a 500 on bad credentials.",
+        amount_usd: 50,
+        currency: "USD",
+        status: "open",
+        created_at: now,
+        updated_at: now,
+      },
+      {
+        id: "bounty-seed-2",
+        title: "Add dark mode",
+        description: "Implement a system-level dark mode toggle.",
+        amount_usd: 100,
+        currency: "USD",
+        status: "claimed",
+        recipient_username: "alice",
+        created_at: now,
+        updated_at: now,
+      },
+      {
+        id: "bounty-seed-3",
+        title: "Write API docs",
+        description: "Document all REST endpoints with OpenAPI.",
+        amount_usd: 75,
+        currency: "USD",
+        status: "paid",
+        recipient_username: "bob",
+        created_at: now,
+        updated_at: now,
+      },
+    ];
+    for (const b of seedBounties) {
+      this.bounties.set(b.id, b);
+    }
+  }
+
+  // ── Bounty helpers ─────────────────────────────────────────────────────────
+
+  listBounties(): Bounty[] {
+    return Array.from(this.bounties.values());
+  }
+
+  getBounty(id: string): Bounty | undefined {
+    return this.bounties.get(id);
+  }
+
+  createBounty(input: CreateBountyInput): Bounty {
+    const now = new Date().toISOString();
+    const bounty: Bounty = {
+      id: randomUUID(),
+      title: input.title,
+      description: input.description,
+      amount_usd: input.amount_usd,
+      currency: input.currency,
+      status: "open",
+      recipient_username: input.recipient_username,
+      created_at: now,
+      updated_at: now,
+    };
+    this.bounties.set(bounty.id, bounty);
+    return bounty;
+  }
+
+  updateBountyStatus(id: string, status: BountyStatus): Bounty | undefined {
+    const bounty = this.bounties.get(id);
+    if (!bounty) return undefined;
+    const updated: Bounty = {
+      ...bounty,
+      status,
+      updated_at: new Date().toISOString(),
+    };
+    this.bounties.set(id, updated);
+    return updated;
+  }
+
+  // ── Payment helpers ────────────────────────────────────────────────────────
+
+  listPayments(): Payment[] {
+    return Array.from(this.payments.values());
+  }
+
+  getPayment(id: string): Payment | undefined {
+    return this.payments.get(id);
+  }
+
+  createPayment(input: CreatePaymentInput): Payment {
+    const payment: Payment = {
+      id: randomUUID(),
+      bounty_id: input.bounty_id,
+      amount_usd: input.amount_usd,
+      currency: input.currency,
+      recipient_username: input.recipient_username,
+      created_at: new Date().toISOString(),
+    };
+    this.payments.set(payment.id, payment);
+    return payment;
+  }
+
+  /** Reset all state — useful in tests */
+  reset() {
+    this.bounties.clear();
+    this.payments.clear();
+    this.seed();
+  }
+}
+
+export const store = new Store();
diff --git a/src/types.ts b/src/types.ts
new file mode 100644
index 0000000..0bb1274
--- /dev/null
+++ b/src/types.ts
@@ -0,0 +1,40 @@
+export type BountyStatus = "open" | "claimed" | "paid";
+
+export interface Bounty {
+  id: string;
+  title: string;
+  description: string;
+  amount_usd: number;
+  currency: string;
+  status: BountyStatus;
+  recipient_username?: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface Payment {
+  id: string;
+  bounty_id: string;
+  amount_usd: number;
+  currency: string;
+  recipient_username: string;
+  created_at: string;
+}
+
+export interface ApiError {
+  error: string;
+  details?: string | Record<string, unknown>;
+}
+
+export interface ApiSuccess<T> {
+  data: T;
+}
+
+export type CreateBountyInput = Pick<
+  Bounty,
+  "title" | "description" | "amount_usd" | "currency"
+> & { recipient_username?: string };
+
+export interface SendPaymentInput {
+  bounty_id: string;
+}
diff --git a/tsconfig.json b/tsconfig.json
index cbcc783..bb5605d 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,39 +1,19 @@
 {
   "compilerOptions": {
-    // Enable latest features
-    "lib": [
-      "ESNext",
-      "DOM"
-    ],
-    "target": "ESNext",
-    "module": "ESNext",
-    "moduleDetection": "force",
-    "jsx": "preserve",
-    "allowJs": true,
-    "baseUrl": ".",
-    // Bundler mode
-    "moduleResolution": "bundler",
-    "allowImportingTsExtensions": true,
-    "verbatimModuleSyntax": true,
-    "noEmit": true,
-    // Best practices
+    "target": "ES2020",
+    "module": "commonjs",
+    "lib": ["ES2020"],
+    "outDir": "./dist",
+    "rootDir": "./src",
     "strict": true,
-    "skipLibCheck": true,
-    "noFallthroughCasesInSwitch": true,
-    // Some stricter flags (disabled by default)
-    "noUnusedLocals": false,
-    "noUnusedParameters": false,
-    "noPropertyAccessFromIndexSignature": false,
-    "incremental": true,
     "esModuleInterop": true,
-    "resolveJsonModule": true
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true
   },
-  "include": [
-    "next-env.d.ts",
-    "**/*.ts",
-    "**/*.tsx"
-  ],
-  "exclude": [
-    "node_modules"
-  ]
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist", "**/*.test.ts"]
 }