diff --git a/tests/copilot-adapter.test.ts b/tests/copilot-adapter.test.ts
index 2ee4e0b..8ec8f15 100644
--- a/tests/copilot-adapter.test.ts
+++ b/tests/copilot-adapter.test.ts
@@ -115,6 +115,62 @@ describe('CopilotAdapter', () => {
   // =========================================================================
 
   describe('token management', () => {
+    it('uses the device flow when no GitHub token is available', async () => {
+      vi.useFakeTimers()
+      const onDeviceCode = vi.fn()
+      globalThis.fetch = vi.fn()
+        .mockResolvedValueOnce({
+          ok: true,
+          json: () => Promise.resolve({
+            device_code: 'device-code',
+            user_code: 'ABCD-EFGH',
+            verification_uri: 'https://github.com/login/device',
+            interval: 0,
+            expires_in: 600,
+          }),
+        })
+        .mockResolvedValueOnce({
+          ok: true,
+          json: () => Promise.resolve({ access_token: 'oauth_token' }),
+        })
+        .mockResolvedValueOnce({
+          ok: true,
+          json: () => Promise.resolve({
+            token: 'session_from_device_flow',
+            expires_at: Math.floor(Date.now() / 1000) + 3600,
+          }),
+          text: () => Promise.resolve(''),
+        })
+
+      const adapter = new CopilotAdapter({ onDeviceCode })
+      mockCreate.mockResolvedValue(makeCompletion())
+
+      const responsePromise = adapter.chat([textMsg('user', 'Hi')], chatOpts())
+      await vi.runAllTimersAsync()
+      await responsePromise
+
+      expect(onDeviceCode).toHaveBeenCalledWith(
+        'https://github.com/login/device',
+        'ABCD-EFGH',
+      )
+      expect(globalThis.fetch).toHaveBeenNthCalledWith(
+        3,
+        'https://api.github.com/copilot_internal/v2/token',
+        expect.objectContaining({
+          headers: expect.objectContaining({
+            Authorization: 'token oauth_token',
+          }),
+        }),
+      )
+      expect(OpenAIMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          apiKey: 'session_from_device_flow',
+        }),
+      )
+
+      vi.useRealTimers()
+    })
+
     it('exchanges GitHub token for Copilot session token', async () => {
       const fetchMock = mockFetchForToken('session_xyz')
       globalThis.fetch = fetchMock
@@ -344,6 +400,23 @@ describe('CopilotAdapter', () => {
 
       expect(events.filter(e => e.type === 'error')).toHaveLength(1)
     })
+
+    it('handles malformed streamed tool arguments JSON', async () => {
+      mockCreate.mockResolvedValue(makeChunks([
+        {
+          id: 'c1', model: 'gpt-4o',
+          choices: [{ index: 0, delta: { tool_calls: [{ index: 0, id: 'call_1', function: { name: 'search', arguments: '{broken' } }] }, finish_reason: 'tool_calls' }],
+          usage: null,
+        },
+        { id: 'c1', model: 'gpt-4o', choices: [], usage: { prompt_tokens: 5, completion_tokens: 3 } },
+      ]))
+
+      const events = await collectEvents(adapter.stream([textMsg('user', 'Hi')], chatOpts()))
+
+      const toolEvents = events.filter(e => e.type === 'tool_use')
+      expect(toolEvents).toHaveLength(1)
+      expect((toolEvents[0].data as ToolUseBlock).input).toEqual({})
+    })
   })
 
   // =========================================================================
diff --git a/tests/gemini-adapter-contract.test.ts b/tests/gemini-adapter-contract.test.ts
index bfd834f..221b1f0 100644
--- a/tests/gemini-adapter-contract.test.ts
+++ b/tests/gemini-adapter-contract.test.ts
@@ -120,6 +120,29 @@ describe('GeminiAdapter (contract)', () => {
       expect(parts[0].functionResponse.name).toBe('unknown_id')
     })
 
+    it('serializes non-string tool_result content to JSON', async () => {
+      mockGenerateContent.mockResolvedValue(makeGeminiResponse([{ text: 'ok' }]))
+
+      await adapter.chat(
+        [{
+          role: 'user',
+          content: [{
+            type: 'tool_result',
+            tool_use_id: 'call_1',
+            content: { answer: 42 } as never,
+            is_error: false,
+          } as never],
+        }],
+        chatOpts(),
+      )
+
+      const parts = mockGenerateContent.mock.calls[0][0].contents[0].parts
+      expect(parts[0].functionResponse.response).toEqual({
+        content: '{"answer":42}',
+        isError: false,
+      })
+    })
+
     it('converts image blocks to inlineData parts', async () => {
       mockGenerateContent.mockResolvedValue(makeGeminiResponse([{ text: 'ok' }]))
 
@@ -265,6 +288,17 @@ describe('GeminiAdapter (contract)', () => {
 
       expect(result.content).toEqual([])
     })
+
+    it('throws for unsupported message block types', async () => {
+      mockGenerateContent.mockResolvedValue(makeGeminiResponse([{ text: 'ok' }]))
+
+      await expect(adapter.chat([
+        {
+          role: 'user',
+          content: [{ type: 'unsupported' } as never],
+        },
+      ], chatOpts())).rejects.toThrow('Unhandled content block type')
+    })
   })
 
   // =========================================================================
diff --git a/tests/openai-adapter.test.ts b/tests/openai-adapter.test.ts
index a2fb4a1..34a8008 100644
--- a/tests/openai-adapter.test.ts
+++ b/tests/openai-adapter.test.ts
@@ -355,5 +355,31 @@ describe('OpenAIAdapter', () => {
       expect((toolEvents[0].data as ToolUseBlock).name).toBe('search')
       expect((toolEvents[1].data as ToolUseBlock).name).toBe('read')
     })
+
+    it('falls back to extracting tool calls from streamed text when no native tool deltas exist', async () => {
+      mockCreate.mockResolvedValue(makeChunks([
+        textChunk('```json\n{"name":"search","input":{"query":"fallback"}}\n```', 'stop'),
+        { id: 'chatcmpl-123', model: 'gpt-4o', choices: [], usage: { prompt_tokens: 6, completion_tokens: 4 } },
+      ]))
+
+      const events = await collectEvents(
+        adapter.stream(
+          [textMsg('user', 'Search for fallback handling')],
+          chatOpts({ tools: [toolDef('search')] }),
+        ),
+      )
+
+      const toolEvents = events.filter(e => e.type === 'tool_use')
+      expect(toolEvents).toHaveLength(1)
+      expect(toolEvents[0].data).toEqual({
+        type: 'tool_use',
+        id: expect.any(String),
+        name: 'search',
+        input: { query: 'fallback' },
+      })
+
+      const done = events.find(e => e.type === 'done')
+      expect((done!.data as LLMResponse).stop_reason).toBe('tool_use')
+    })
   })
 })