diff --git a/DECISIONS.md b/DECISIONS.md
index 51169d5..4254c28 100644
--- a/DECISIONS.md
+++ b/DECISIONS.md
@@ -282,3 +282,9 @@ Implementation decisions not spelled out in `memory-bank/implementation-plan.md`
 - **`storeDispatch` is shared by every dispatch kind:** it inserts the dispatch, records the accepted contract, and deducts the record's fuel cost (0 for tutorial runs).
 - **Sim validation reasons are returned as `409` with their own code** and a player-facing message from `src/game/messages.ts`.
 - **`404 unknown-contract` and `404 unknown-skill`** join `not-found` as the codes that map to 404.
+
+## Step 6.5
+
+- **Ship names** are "Adjective Noun" from fixed word lists, picked by a generator seeded with `deriveSeed(worldSeed, "ship-name:<n>")`, where n is how many ships the player owned before this one. They are stable per world (decision 0.5.14) and are not unique; duplicates are acceptable. Word lists live in the server (`src/game/names.ts`) because they are not tuning numbers.
+- **New ships always appear at Earth**, as the plan says, whatever the player's bays.
+- **`spend()` checks and deducts credits inside the player lock**, so a failed purchase changes nothing (`409 insufficient-funds`). Unknown models return `404 not-found`.
diff --git a/apps/server/src/app.ts b/apps/server/src/app.ts
index 72c0db1..53d7627 100644
--- a/apps/server/src/app.ts
+++ b/apps/server/src/app.ts
@@ -8,6 +8,7 @@ import { requirePlayerId } from "./http/session";
 import type { AppContext } from "./routes/context";
 import { registerBoardRoutes } from "./routes/boards";
 import { registerDispatchRoutes } from "./routes/dispatches";
+import { registerFleetRoutes } from "./routes/fleet";
 import { registerPlayerRoutes } from "./routes/player";
 
 export interface AppDeps {
@@ -43,6 +44,7 @@ export function buildApp(config: ServerConfig, deps: AppDeps = {}): FastifyInsta
   registerPlayerRoutes(app, ctx);
   registerBoardRoutes(app, ctx);
   registerDispatchRoutes(app, ctx);
+  registerFleetRoutes(app, ctx);
 
   return app;
 }
diff --git a/apps/server/src/game/fleet.ts b/apps/server/src/game/fleet.ts
new file mode 100644
index 0000000..a49be70
--- /dev/null
+++ b/apps/server/src/game/fleet.ts
@@ -0,0 +1,71 @@
+import { randomUUID } from "node:crypto";
+import { content } from "@deadhead/content";
+import type { Ship } from "@deadhead/schema";
+import type { RealTime } from "@deadhead/sim";
+import { count, eq, sql } from "drizzle-orm";
+import type { Queryable } from "../db/client";
+import { companies, players, ships } from "../db/schema";
+import { gameError } from "../http/errors";
+import { shipName } from "./names";
+
+/** Where newly bought ships appear. */
+export const SHIPYARD_LOCATION_ID = "earth";
+
+export async function requireCompany(tx: Queryable, playerId: string) {
+  const [company] = await tx.select().from(companies).where(eq(companies.playerId, playerId));
+  if (!company) throw new Error(`Player ${playerId} has no company`);
+  return company;
+}
+
+export async function requirePlayer(tx: Queryable, playerId: string) {
+  const [player] = await tx.select().from(players).where(eq(players.id, playerId));
+  if (!player) throw new Error(`Player ${playerId} not found`);
+  return player;
+}
+
+/** Deducts credits, or throws `insufficient-funds` without changing anything. */
+export async function spend(tx: Queryable, playerId: string, amount: number, what: string) {
+  const company = await requireCompany(tx, playerId);
+  if (company.credits < amount) {
+    throw gameError("insufficient-funds", `Not enough credits for ${what} (${amount} needed).`);
+  }
+  await tx
+    .update(companies)
+    .set({ credits: sql`${companies.credits} - ${amount}` })
+    .where(eq(companies.playerId, playerId));
+}
+
+/** Buys a ship model: it appears idle at Earth with no pilot (Step 6.5). */
+export async function buyShip(
+  tx: Queryable,
+  playerId: string,
+  modelId: string,
+  now: RealTime,
+): Promise<Ship> {
+  const model = content.shipModel(modelId);
+  if (!model) throw gameError("not-found", `No ship model "${modelId}".`);
+  await spend(tx, playerId, model.price, `a ${model.name}`);
+
+  const player = await requirePlayer(tx, playerId);
+  const [owned] = await tx.select({ n: count() }).from(ships).where(eq(ships.playerId, playerId));
+  const [ship] = await tx
+    .insert(ships)
+    .values({
+      id: randomUUID(),
+      playerId,
+      modelId,
+      name: shipName(player.worldSeed, owned!.n),
+      locationId: SHIPYARD_LOCATION_ID,
+      createdAt: now,
+    })
+    .returning();
+  return {
+    id: ship!.id,
+    modelId: ship!.modelId,
+    name: ship!.name,
+    status: "idle",
+    locationId: ship!.locationId,
+    dispatchId: null,
+    pilotId: null,
+  };
+}
diff --git a/apps/server/src/game/names.ts b/apps/server/src/game/names.ts
new file mode 100644
index 0000000..54f2cc4
--- /dev/null
+++ b/apps/server/src/game/names.ts
@@ -0,0 +1,86 @@
+import { createRng, deriveSeed, type Seed } from "@deadhead/sim";
+
+const SHIP_ADJECTIVES = [
+  "Dusty",
+  "Rusty",
+  "Lucky",
+  "Stubborn",
+  "Quiet",
+  "Restless",
+  "Patient",
+  "Wandering",
+  "Crooked",
+  "Faithful",
+  "Midnight",
+  "Copper",
+  "Iron",
+  "Silver",
+  "Old",
+  "Brave",
+];
+const SHIP_NOUNS = [
+  "Mule",
+  "Ox",
+  "Heron",
+  "Comet",
+  "Lantern",
+  "Drifter",
+  "Kettle",
+  "Anchor",
+  "Sparrow",
+  "Badger",
+  "Tortoise",
+  "Pilgrim",
+  "Barge",
+  "Nomad",
+  "Hauler",
+  "Wren",
+];
+const FIRST_NAMES = [
+  "Rae",
+  "Jonah",
+  "Mira",
+  "Tobias",
+  "Ines",
+  "Kofi",
+  "Lena",
+  "Arjun",
+  "Sasha",
+  "Dmitri",
+  "Yuki",
+  "Nadia",
+  "Emeka",
+  "Freya",
+  "Mateo",
+  "Priya",
+];
+const LAST_NAMES = [
+  "Okafor",
+  "Lindqvist",
+  "Moreau",
+  "Tanaka",
+  "Reyes",
+  "Novak",
+  "Haddad",
+  "Kowalski",
+  "Mbeki",
+  "Castillo",
+  "Sorensen",
+  "Iyer",
+  "Brennan",
+  "Vasquez",
+  "Kim",
+  "Abara",
+];
+
+/** The nth ship name in a world (decision 0.5.14): stable for a given seed and n. */
+export function shipName(worldSeed: Seed, n: number): string {
+  const rng = createRng(deriveSeed(worldSeed, `ship-name:${n}`));
+  return `${rng.pick(SHIP_ADJECTIVES)} ${rng.pick(SHIP_NOUNS)}`;
+}
+
+/** The nth hired pilot's name in a world: stable for a given seed and n. */
+export function pilotName(worldSeed: Seed, n: number): string {
+  const rng = createRng(deriveSeed(worldSeed, `pilot-name:${n}`));
+  return `${rng.pick(FIRST_NAMES)} ${rng.pick(LAST_NAMES)}`;
+}
diff --git a/apps/server/src/routes/fleet.ts b/apps/server/src/routes/fleet.ts
new file mode 100644
index 0000000..fc9a9f6
--- /dev/null
+++ b/apps/server/src/routes/fleet.ts
@@ -0,0 +1,15 @@
+import { routes } from "@deadhead/schema";
+import type { FastifyInstance } from "fastify";
+import { buyShip } from "../game/fleet";
+import { registerRoute } from "../http/route";
+import type { AppContext } from "./context";
+import { withPlayer } from "./with-player";
+
+/** Ships, bays and pilots. */
+export function registerFleetRoutes(app: FastifyInstance, ctx: AppContext): void {
+  registerRoute(app, routes.buyShip, ctx.options, async (input, { playerId }) =>
+    withPlayer(ctx, playerId, async (tx, now) => ({
+      ship: await buyShip(tx, playerId, input.modelId, now),
+    })),
+  );
+}
diff --git a/apps/server/test/buy-ship.test.ts b/apps/server/test/buy-ship.test.ts
new file mode 100644
index 0000000..5fbc44f
--- /dev/null
+++ b/apps/server/test/buy-ship.test.ts
@@ -0,0 +1,65 @@
+import { content } from "@deadhead/content";
+import { errorResponseSchema, shipResponseSchema } from "@deadhead/schema";
+import { describe, expect, it } from "vitest";
+import { shipName } from "../src/game/names";
+import { setCredits, useTestDatabase } from "./db";
+import { call, getState, signUp, useTestApp } from "./game";
+
+const database = useTestDatabase();
+const testApp = useTestApp(database);
+
+describe("buy a ship", () => {
+  it("deducts the price and adds an idle, uncrewed ship at Earth", async () => {
+    const { app } = testApp();
+    const guest = await signUp(app);
+    const price = content.shipModel("courier")!.price;
+    await setCredits(database().db, guest.playerId, price + 500);
+
+    const response = await call(app, guest, "POST", "/api/ships", { modelId: "courier" });
+    expect(response.statusCode).toBe(200);
+    const { ship } = shipResponseSchema.parse(response.json());
+    expect(ship).toMatchObject({
+      modelId: "courier",
+      status: "idle",
+      locationId: "earth",
+      pilotId: null,
+      dispatchId: null,
+    });
+    expect(ship.name.length).toBeGreaterThan(0);
+
+    const state = await getState(app, guest);
+    expect(state.company.credits).toBe(500);
+    expect(state.ships.map((s) => s.id)).toEqual([ship.id]);
+  });
+
+  it("returns insufficient-funds and changes nothing without enough credits", async () => {
+    const { app } = testApp();
+    const guest = await signUp(app);
+    const price = content.shipModel("freighter")!.price;
+    await setCredits(database().db, guest.playerId, price - 1);
+
+    const response = await call(app, guest, "POST", "/api/ships", { modelId: "freighter" });
+    expect(response.statusCode).toBe(409);
+    expect(errorResponseSchema.parse(response.json()).error.code).toBe("insufficient-funds");
+
+    const state = await getState(app, guest);
+    expect(state.company.credits).toBe(price - 1);
+    expect(state.ships).toHaveLength(0);
+  });
+
+  it("rejects an unknown model", async () => {
+    const { app } = testApp();
+    const guest = await signUp(app);
+    const response = await call(app, guest, "POST", "/api/ships", { modelId: "x-wing" });
+    expect(response.statusCode).toBe(404);
+    expect(errorResponseSchema.parse(response.json()).error.code).toBe("not-found");
+  });
+});
+
+describe("ship names", () => {
+  it("are stable for a world seed and differ between ships", () => {
+    expect(shipName(42, 0)).toBe(shipName(42, 0));
+    const names = new Set(Array.from({ length: 10 }, (_, i) => shipName(42, i)));
+    expect(names.size).toBeGreaterThan(1);
+  });
+});
diff --git a/memory-bank/progress.md b/memory-bank/progress.md
index e59c4ce..d2bd36b 100644
--- a/memory-bank/progress.md
+++ b/memory-bank/progress.md
@@ -58,7 +58,7 @@
 - [x] **Step 6.2 — Get full player state.** Endpoint from Step 5.5 plus lazy resolution; test covers a player with one ship in flight and one idle (crewed by a hired pilot), checking ships, pilots (XP, level, skills, points, assignment, status, location), bays, dispatches, summaries and schema validity.
 - [x] **Step 6.3 — Tutorial board endpoint.** `GET /api/tutorial/board` (`src/routes/boards.ts`, `src/game/boards.ts`): stored per (period, loaner location) on first request, accepted contracts hidden, `409 not-in-tutorial` after the tutorial. Every game route now runs through `withPlayer` (lock + lazy resolution).
 - [x] **Step 6.4 — Tutorial dispatch.** `POST /api/dispatches` with `kind: "tutorial"` (`src/game/dispatch.ts`): avatar + loaner, sim validation, no fuel, one run at a time; contract marked accepted. Arrival pays the stored tutorial payout and moves loaner and avatar.
-- [ ] Step 6.5 — Buy a ship
+- [x] **Step 6.5 — Buy a ship.** `POST /api/ships` (`src/game/fleet.ts`, `src/routes/fleet.ts`): deducts the price, adds an idle uncrewed ship at Earth named from the world seed (`src/game/names.ts`); `409 insufficient-funds` changes nothing.
 - [ ] Step 6.6 — Lease a bay
 - [ ] Step 6.7 — End tutorial
 - [ ] Step 6.8 — Hire and assign pilots