diff --git a/src/services/api/client.test.ts b/src/services/api/client.test.ts
new file mode 100644
index 00000000..4927c381
--- /dev/null
+++ b/src/services/api/client.test.ts
@@ -0,0 +1,87 @@
+import { describe, expect, mock, test } from 'bun:test'
+
+mock.module('src/utils/http.js', () => ({
+  getAuthHeaders: mock(() => ({})),
+  getMCPUserAgent: mock(() => 'client-test-agent'),
+  getUserAgent: mock(() => 'client-test-agent'),
+  getWebFetchUserAgent: mock(() => 'client-test-agent'),
+  withOAuth401Retry: mock(async <T>(fn: () => Promise<T>) => fn()),
+}))
+
+describe('resolveAnthropicClientApiKey', () => {
+  test('does not inherit a local api key when a provider auth token is explicit', async () => {
+    const { resolveAnthropicClientApiKey } = await import('./client.js')
+    const getFallbackApiKey = mock(() => 'sk-keychain-fallback')
+
+    const apiKey = resolveAnthropicClientApiKey({
+      envAuthToken: 'provider-bearer-token',
+      envApiKey: undefined,
+      getFallbackApiKey,
+    })
+
+    expect(apiKey).toBeNull()
+    expect(getFallbackApiKey).not.toHaveBeenCalled()
+  })
+
+  test('preserves an explicit api key when the caller opts into dual auth', async () => {
+    const { resolveAnthropicClientApiKey } = await import('./client.js')
+    const getFallbackApiKey = mock(() => 'sk-keychain-fallback')
+
+    const apiKey = resolveAnthropicClientApiKey({
+      explicitApiKey: 'sk-explicit-api-key',
+      envAuthToken: 'provider-bearer-token',
+      getFallbackApiKey,
+    })
+
+    expect(apiKey).toBe('sk-explicit-api-key')
+    expect(getFallbackApiKey).not.toHaveBeenCalled()
+  })
+
+  test('falls back to the local api key when no provider auth token is present', async () => {
+    const { resolveAnthropicClientApiKey } = await import('./client.js')
+    const getFallbackApiKey = mock(() => 'sk-keychain-fallback')
+
+    const apiKey = resolveAnthropicClientApiKey({
+      envAuthToken: undefined,
+      envApiKey: undefined,
+      getFallbackApiKey,
+    })
+
+    expect(apiKey).toBe('sk-keychain-fallback')
+    expect(getFallbackApiKey).toHaveBeenCalled()
+  })
+})
+
+describe('getAnthropicClient', () => {
+  test('passes bearer-token provider auth without an SDK api key', async () => {
+    const { getAnthropicClient } = await import('./client.js')
+    const originalAuthToken = process.env.ANTHROPIC_AUTH_TOKEN
+    const originalApiKey = process.env.ANTHROPIC_API_KEY
+    const originalSimple = process.env.CLAUDE_CODE_SIMPLE
+
+    process.env.ANTHROPIC_AUTH_TOKEN = 'provider-bearer-token'
+    process.env.CLAUDE_CODE_SIMPLE = '1'
+    delete process.env.ANTHROPIC_API_KEY
+
+    try {
+      const client = await getAnthropicClient({
+        maxRetries: 0,
+        model: 'claude-sonnet-4-6',
+      })
+
+      expect(client.apiKey).toBeNull()
+      expect(client._options.defaultHeaders).toMatchObject({
+        Authorization: 'Bearer provider-bearer-token',
+      })
+    } finally {
+      if (originalAuthToken === undefined) delete process.env.ANTHROPIC_AUTH_TOKEN
+      else process.env.ANTHROPIC_AUTH_TOKEN = originalAuthToken
+
+      if (originalApiKey === undefined) delete process.env.ANTHROPIC_API_KEY
+      else process.env.ANTHROPIC_API_KEY = originalApiKey
+
+      if (originalSimple === undefined) delete process.env.CLAUDE_CODE_SIMPLE
+      else process.env.CLAUDE_CODE_SIMPLE = originalSimple
+    }
+  })
+})
diff --git a/src/services/api/client.ts b/src/services/api/client.ts
index b26e8b3f..62fc6c9b 100644
--- a/src/services/api/client.ts
+++ b/src/services/api/client.ts
@@ -91,6 +91,24 @@ function createStderrLogger(): ClientOptions['logger'] {
   }
 }
 
+export function resolveAnthropicClientApiKey({
+  explicitApiKey,
+  envAuthToken = process.env.ANTHROPIC_AUTH_TOKEN,
+  envApiKey = process.env.ANTHROPIC_API_KEY,
+  getFallbackApiKey = getAnthropicApiKey,
+}: {
+  explicitApiKey?: string
+  envAuthToken?: string
+  envApiKey?: string
+  getFallbackApiKey?: () => string | null
+}): string | null {
+  if (envAuthToken && !explicitApiKey && !envApiKey) {
+    return null
+  }
+
+  return explicitApiKey || getFallbackApiKey()
+}
+
 export async function getAnthropicClient({
   apiKey,
   maxRetries,
@@ -319,7 +337,7 @@ export async function getAnthropicClient({
       ? null
       : usingOpenAICodex
         ? OPENAI_OAUTH_DUMMY_KEY
-        : apiKey || getAnthropicApiKey(),
+        : resolveAnthropicClientApiKey({ explicitApiKey: apiKey }),
     authToken: isClaudeAISubscriber()
       ? getClaudeAIOAuthTokens()?.accessToken
       : undefined,