diff --git a/packages/api/src/__tests__/bounties_detail.test.ts b/packages/api/src/__tests__/bounties_detail.test.ts
new file mode 100644
index 0000000..c41437a
--- /dev/null
+++ b/packages/api/src/__tests__/bounties_detail.test.ts
@@ -0,0 +1,84 @@
+import { describe, it, expect, beforeAll, vi } from 'vitest';
+import { createApp } from '../app';
+import { verify } from 'hono/jwt';
+import { db } from '../db';
+
+vi.mock('hono/jwt', () => ({
+  verify: vi.fn(),
+}));
+
+vi.mock('../db', () => ({
+  db: {
+    query: {
+      bounties: {
+        findFirst: vi.fn(),
+      },
+      applications: {
+        findMany: vi.fn(),
+      },
+      users: {
+        findFirst: vi.fn(),
+      },
+    },
+  },
+}));
+
+describe('GET /api/bounties/:id', () => {
+  let app: ReturnType<typeof createApp>;
+
+  beforeAll(() => {
+    app = createApp();
+    vi.mocked(verify).mockResolvedValue({
+      sub: 'test-user-id',
+      username: 'testuser',
+      exp: Math.floor(Date.now() / 1000) + 3600,
+    });
+    process.env.JWT_PUBLIC_KEY = '-----BEGIN PUBLIC KEY-----\\nfake\\n-----END PUBLIC KEY-----';
+  });
+
+  it('returns bounty detail with creator, assignee and application_count', async () => {
+    vi.mocked(db.query.bounties.findFirst).mockResolvedValue({
+      id: 'bounty-1',
+      title: 'Fix endpoint',
+      status: 'assigned',
+      creatorId: 'creator-1',
+      assigneeId: 'assignee-1',
+      createdAt: new Date('2025-01-01T00:00:00Z'),
+      updatedAt: new Date('2025-01-02T00:00:00Z'),
+    } as any);
+
+    vi.mocked(db.query.applications.findMany).mockResolvedValue([
+      { id: 'app-1' },
+      { id: 'app-2' },
+    ] as any);
+
+    vi.mocked(db.query.users.findFirst)
+      .mockResolvedValueOnce({ id: 'creator-1', username: 'alice', avatarUrl: 'https://avatar/alice.png' } as any)
+      .mockResolvedValueOnce({ id: 'assignee-1', username: 'bob', avatarUrl: 'https://avatar/bob.png' } as any);
+
+    const res = await app.request('/api/bounties/bounty-1', {
+      headers: { Authorization: 'Bearer valid.token' },
+    });
+
+    expect(res.status).toBe(200);
+    const body = await res.json();
+
+    expect(body.id).toBe('bounty-1');
+    expect(body.status).toBe('assigned');
+    expect(body.application_count).toBe(2);
+    expect(body.creator).toEqual({ username: 'alice', avatar_url: 'https://avatar/alice.png' });
+    expect(body.assignee).toEqual({ username: 'bob', avatar_url: 'https://avatar/bob.png' });
+  });
+
+  it('returns 404 when bounty does not exist', async () => {
+    vi.mocked(db.query.bounties.findFirst).mockResolvedValue(null as any);
+
+    const res = await app.request('/api/bounties/missing', {
+      headers: { Authorization: 'Bearer valid.token' },
+    });
+
+    expect(res.status).toBe(404);
+    const body = await res.json();
+    expect(body.error).toBe('Bounty not found');
+  });
+});
diff --git a/packages/api/src/routes/bounties.ts b/packages/api/src/routes/bounties.ts
index 2f4f6e6..57992ad 100644
--- a/packages/api/src/routes/bounties.ts
+++ b/packages/api/src/routes/bounties.ts
@@ -2,7 +2,7 @@ import { Hono } from 'hono';
 import { Variables } from '../middleware/auth';
 import { ensureBountyCreator, ensureBountyAssignee } from '../middleware/resource-auth';
 import { db } from '../db';
-import { bounties } from '../db/schema';
+import { applications, bounties, users } from '../db/schema';
 import { eq, and, gte, lte, sql, desc, or, lt } from 'drizzle-orm';
 
 const bountiesRouter = new Hono<{ Variables: Variables }>();
@@ -136,7 +136,39 @@ bountiesRouter.get('/:id', async (c) => {
         return c.json({ error: 'Bounty not found' }, 404);
     }
 
-    return c.json(bounty);
+    const [applicationsForBounty, creator, assignee] = await Promise.all([
+        db.query.applications.findMany({
+            where: eq(applications.bountyId, bounty.id),
+            columns: { id: true },
+        }),
+        db.query.users.findFirst({
+            where: eq(users.id, bounty.creatorId),
+            columns: { username: true, avatarUrl: true },
+        }),
+        bounty.assigneeId
+            ? db.query.users.findFirst({
+                where: eq(users.id, bounty.assigneeId),
+                columns: { username: true, avatarUrl: true },
+            })
+            : Promise.resolve(null),
+    ]);
+
+    return c.json({
+        ...bounty,
+        application_count: applicationsForBounty.length,
+        creator: creator
+            ? {
+                username: creator.username,
+                avatar_url: creator.avatarUrl,
+            }
+            : null,
+        assignee: assignee
+            ? {
+                username: assignee.username,
+                avatar_url: assignee.avatarUrl,
+            }
+            : null,
+    });
 });
 
 /**