diff --git a/server/src/engine/human-responses.test.ts b/server/src/engine/human-responses.test.ts
new file mode 100644
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+++ b/server/src/engine/human-responses.test.ts
@@ -0,0 +1,88 @@
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { waitForHumanResponse, submitHumanResponse, getPendingChallenge, clearAllPending } from './human-responses.js'
+import type { Challenge } from './challenges.js'
+
+const mockChallenge: Challenge = {
+  type: 'bitcoin_trivia',
+  label: 'Bitcoin Trivia',
+  prompt: 'What year was Bitcoin launched?',
+  answers: ['2009'],
+  scoring: 'factual',
+  timeout_ms: 8000,
+  difficulty: 'medium',
+  choices: ['2009', '2010', '2008'],
+}
+
+afterEach(() => {
+  clearAllPending()
+})
+
+describe('waitForHumanResponse race condition fix', () => {
+  it('pending challenge is stored synchronously before promise resolves', () => {
+    // Call waitForHumanResponse — this must store the pending challenge
+    // SYNCHRONOUSLY (inside Promise constructor), not in a microtask
+    const { promise, choices } = waitForHumanResponse('fight-1', 'bot-1', mockChallenge, 1)
+
+    // IMMEDIATELY after, getPendingChallenge must find it
+    // (no await needed — this proves it's synchronous)
+    const pending = getPendingChallenge('fight-1', 'bot-1')
+    expect(pending).not.toBeNull()
+    expect(pending!.prompt).toBe('What year was Bitcoin launched?')
+    expect(pending!.choices).toEqual(choices)
+
+    // Clean up by submitting
+    submitHumanResponse('fight-1', 'bot-1', '2009')
+  })
+
+  it('choices are returned from waitForHumanResponse for SSE inclusion', () => {
+    const { choices } = waitForHumanResponse('fight-2', 'bot-2', mockChallenge, 1)
+
+    // Choices must be non-empty and include the correct answer
+    expect(choices.length).toBeGreaterThanOrEqual(2)
+    expect(choices).toContain('2009')
+
+    submitHumanResponse('fight-2', 'bot-2', '2009')
+  })
+})
+
+describe('waitForHumanResponse timeout', () => {
+  it('times out and resolves with null answer', async () => {
+    vi.useFakeTimers()
+    const shortChallenge = { ...mockChallenge, timeout_ms: 100 }
+    const { promise } = waitForHumanResponse('fight-3', 'bot-3', shortChallenge, 1)
+
+    // Advance past timeout (100ms challenge + 5000ms human extra)
+    vi.advanceTimersByTime(5200)
+    const result = await promise
+    expect(result.timedOut).toBe(true)
+    expect(result.answer).toBeNull()
+    vi.useRealTimers()
+  })
+})
+
+describe('submitHumanResponse', () => {
+  it('accepts submission and resolves promise', async () => {
+    const { promise } = waitForHumanResponse('fight-4', 'bot-4', mockChallenge, 1)
+
+    const accepted = submitHumanResponse('fight-4', 'bot-4', '2009', 'Bitcoin fixes this')
+    expect(accepted).toBe(true)
+
+    const result = await promise
+    expect(result.answer).toBe('2009')
+    expect(result.trashTalk).toBe('Bitcoin fixes this')
+    expect(result.timedOut).toBe(false)
+  })
+
+  it('returns false for unknown fight/bot', () => {
+    const accepted = submitHumanResponse('nonexistent', 'nobody', 'answer')
+    expect(accepted).toBe(false)
+  })
+
+  it('truncates long answers to 2000 chars', async () => {
+    const { promise } = waitForHumanResponse('fight-5', 'bot-5', mockChallenge, 1)
+    const longAnswer = 'x'.repeat(3000)
+    submitHumanResponse('fight-5', 'bot-5', longAnswer)
+    const result = await promise
+    expect(result.answer!.length).toBe(2000)
+  })
+})