diff --git a/src/main/apiServer/adapters/__tests__/AiSdkToAnthropicSSE.test.ts b/src/main/apiServer/adapters/__tests__/AiSdkToAnthropicSSE.test.ts
new file mode 100644
index 0000000000..766677b60d
--- /dev/null
+++ b/src/main/apiServer/adapters/__tests__/AiSdkToAnthropicSSE.test.ts
@@ -0,0 +1,538 @@
+import type { RawMessageStreamEvent } from '@anthropic-ai/sdk/resources/messages'
+import type { FinishReason, LanguageModelUsage, TextStreamPart, ToolSet } from 'ai'
+import { describe, expect, it, vi } from 'vitest'
+
+import { AiSdkToAnthropicSSE, formatSSEDone, formatSSEEvent } from '../AiSdkToAnthropicSSE'
+
+// Helper to create properly typed mock events with all required fields
+const createTextDelta = (text: string, id = 'text_0'): TextStreamPart<ToolSet> => ({
+  type: 'text-delta',
+  id,
+  text
+})
+
+const createTextStart = (id = 'text_0'): TextStreamPart<ToolSet> => ({
+  type: 'text-start',
+  id
+})
+
+const createTextEnd = (id = 'text_0'): TextStreamPart<ToolSet> => ({
+  type: 'text-end',
+  id
+})
+
+const createFinish = (
+  finishReason: FinishReason | undefined = 'stop',
+  totalUsage?: Partial<LanguageModelUsage>
+): TextStreamPart<ToolSet> => {
+  const defaultUsage: LanguageModelUsage = {
+    inputTokens: 0,
+    outputTokens: 0,
+    totalTokens: 0
+  }
+  const event: TextStreamPart<ToolSet> = {
+    type: 'finish',
+    finishReason: finishReason || 'stop',
+    totalUsage: { ...defaultUsage, ...totalUsage }
+  }
+  return event
+}
+
+// Helper to create stream from extended events
+// Note: The adapter runtime accepts both standard and extended events
+function createMockStream(events: readonly TextStreamPart<ToolSet>[]) {
+  return new ReadableStream<TextStreamPart<ToolSet>>({
+    start(controller) {
+      for (const event of events) {
+        controller.enqueue(event)
+      }
+      controller.close()
+    }
+  })
+}
+
+describe('AiSdkToAnthropicSSE', () => {
+  describe('Text Processing', () => {
+    it('should emit message_start and process text-delta events', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      // Create a mock stream with text events
+      const stream = createMockStream([createTextDelta('Hello'), createTextDelta(' world'), createFinish('stop')])
+
+      await adapter.processStream(stream)
+
+      // Verify message_start
+      expect(events[0]).toMatchObject({
+        type: 'message_start',
+        message: {
+          role: 'assistant',
+          model: 'test:model'
+        }
+      })
+
+      // Verify content_block_start for text
+      expect(events[1]).toMatchObject({
+        type: 'content_block_start',
+        content_block: { type: 'text' }
+      })
+
+      // Verify text deltas
+      expect(events[2]).toMatchObject({
+        type: 'content_block_delta',
+        delta: { type: 'text_delta', text: 'Hello' }
+      })
+      expect(events[3]).toMatchObject({
+        type: 'content_block_delta',
+        delta: { type: 'text_delta', text: ' world' }
+      })
+
+      // Verify content_block_stop
+      expect(events[4]).toMatchObject({
+        type: 'content_block_stop'
+      })
+
+      // Verify message_delta with stop_reason
+      expect(events[5]).toMatchObject({
+        type: 'message_delta',
+        delta: { stop_reason: 'end_turn' }
+      })
+
+      // Verify message_stop
+      expect(events[6]).toMatchObject({
+        type: 'message_stop'
+      })
+    })
+
+    it('should handle text-start and text-end events', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([
+        createTextStart(),
+        createTextDelta('Test'),
+        createTextEnd(),
+        createFinish('stop')
+      ])
+
+      await adapter.processStream(stream)
+
+      // Should have content_block_start, delta, and content_block_stop
+      const blockEvents = events.filter((e) => e.type.startsWith('content_block'))
+      expect(blockEvents.length).toBeGreaterThanOrEqual(3)
+    })
+
+    it('should auto-start text block if not explicitly started', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([createTextDelta('Auto-started'), createFinish('stop')])
+
+      await adapter.processStream(stream)
+
+      // Should automatically emit content_block_start
+      expect(events.some((e) => e.type === 'content_block_start')).toBe(true)
+    })
+  })
+
+  describe('Tool Call Processing', () => {
+    it('should emit tool_use block for tool-call events', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([
+        {
+          type: 'tool-call',
+          toolCallId: 'call_123',
+          toolName: 'get_weather',
+          input: { location: 'SF' }
+        },
+        createFinish('tool-calls')
+      ])
+
+      await adapter.processStream(stream)
+
+      // Find tool_use block events
+      const blockStart = events.find((e) => {
+        if (e.type === 'content_block_start') {
+          return e.content_block.type === 'tool_use'
+        }
+        return false
+      })
+      expect(blockStart).toBeDefined()
+      if (blockStart && blockStart.type === 'content_block_start') {
+        expect(blockStart.content_block).toMatchObject({
+          type: 'tool_use',
+          id: 'call_123',
+          name: 'get_weather'
+        })
+      }
+
+      // Should emit input_json_delta
+      const delta = events.find((e) => {
+        if (e.type === 'content_block_delta') {
+          return e.delta.type === 'input_json_delta'
+        }
+        return false
+      })
+      expect(delta).toBeDefined()
+
+      // Should have stop_reason as tool_use
+      const messageDelta = events.find((e) => e.type === 'message_delta')
+      if (messageDelta && messageDelta.type === 'message_delta') {
+        expect(messageDelta.delta.stop_reason).toBe('tool_use')
+      }
+    })
+
+    it('should not create duplicate tool blocks', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const toolCallEvent: TextStreamPart<ToolSet> = {
+        type: 'tool-call',
+        toolCallId: 'call_123',
+        toolName: 'test_tool',
+        input: {}
+      }
+      const stream = createMockStream([toolCallEvent, toolCallEvent, createFinish()])
+
+      await adapter.processStream(stream)
+
+      // Should only have one tool_use block
+      const toolBlocks = events.filter((e) => {
+        if (e.type === 'content_block_start') {
+          return e.content_block.type === 'tool_use'
+        }
+        return false
+      })
+      expect(toolBlocks.length).toBe(1)
+    })
+  })
+
+  describe('Reasoning/Thinking Processing', () => {
+    it('should emit thinking block for reasoning events', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([
+        { type: 'reasoning-start', id: 'reason_1' },
+        { type: 'reasoning-delta', id: 'reason_1', text: 'Thinking...' },
+        { type: 'reasoning-end', id: 'reason_1' },
+        createFinish()
+      ])
+
+      await adapter.processStream(stream)
+
+      // Find thinking block events
+      const blockStart = events.find((e) => {
+        if (e.type === 'content_block_start') {
+          return e.content_block.type === 'thinking'
+        }
+        return false
+      })
+      expect(blockStart).toBeDefined()
+
+      // Should emit thinking_delta
+      const delta = events.find((e) => {
+        if (e.type === 'content_block_delta') {
+          return e.delta.type === 'thinking_delta'
+        }
+        return false
+      })
+      expect(delta).toBeDefined()
+      if (delta && delta.type === 'content_block_delta' && delta.delta.type === 'thinking_delta') {
+        expect(delta.delta.thinking).toBe('Thinking...')
+      }
+    })
+
+    it('should handle multiple thinking blocks', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([
+        { type: 'reasoning-start', id: 'reason_1' },
+        { type: 'reasoning-delta', id: 'reason_1', text: 'First thought' },
+        { type: 'reasoning-start', id: 'reason_2' },
+        { type: 'reasoning-delta', id: 'reason_2', text: 'Second thought' },
+        { type: 'reasoning-end', id: 'reason_1' },
+        { type: 'reasoning-end', id: 'reason_2' },
+        createFinish()
+      ])
+
+      await adapter.processStream(stream)
+
+      // Should have two thinking blocks
+      const thinkingBlocks = events.filter((e) => {
+        if (e.type === 'content_block_start') {
+          return e.content_block.type === 'thinking'
+        }
+        return false
+      })
+      expect(thinkingBlocks.length).toBe(2)
+    })
+  })
+
+  describe('Finish Reasons', () => {
+    it('should map finish reasons correctly', async () => {
+      const testCases: Array<{
+        aiSdkReason: FinishReason
+        expectedReason: string
+      }> = [
+        { aiSdkReason: 'stop', expectedReason: 'end_turn' },
+        { aiSdkReason: 'length', expectedReason: 'max_tokens' },
+        { aiSdkReason: 'tool-calls', expectedReason: 'tool_use' },
+        { aiSdkReason: 'content-filter', expectedReason: 'refusal' }
+      ]
+
+      for (const { aiSdkReason, expectedReason } of testCases) {
+        const events: RawMessageStreamEvent[] = []
+        const adapter = new AiSdkToAnthropicSSE({
+          model: 'test:model',
+          onEvent: (event) => events.push(event)
+        })
+
+        const stream = createMockStream([createFinish(aiSdkReason)])
+
+        await adapter.processStream(stream)
+
+        const messageDelta = events.find((e) => e.type === 'message_delta')
+        if (messageDelta && messageDelta.type === 'message_delta') {
+          expect(messageDelta.delta.stop_reason).toBe(expectedReason)
+        }
+      }
+    })
+  })
+
+  describe('Usage Tracking', () => {
+    it('should track token usage', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        inputTokens: 100,
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([
+        createTextDelta('Hello'),
+        createFinish('stop', {
+          inputTokens: 100,
+          outputTokens: 50,
+          cachedInputTokens: 20
+        })
+      ])
+
+      await adapter.processStream(stream)
+
+      const messageDelta = events.find((e) => e.type === 'message_delta')
+      if (messageDelta && messageDelta.type === 'message_delta') {
+        expect(messageDelta.usage).toMatchObject({
+          input_tokens: 100,
+          output_tokens: 50,
+          cache_creation_input_tokens: 20
+        })
+      }
+    })
+  })
+
+  describe('Non-Streaming Response', () => {
+    it('should build complete message for non-streaming', async () => {
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: vi.fn()
+      })
+
+      const stream = createMockStream([
+        createTextDelta('Hello world'),
+        {
+          type: 'tool-call',
+          toolCallId: 'call_1',
+          toolName: 'test',
+          input: { arg: 'value' }
+        },
+        createFinish('tool-calls', { inputTokens: 10, outputTokens: 20 })
+      ])
+
+      await adapter.processStream(stream)
+
+      const response = adapter.buildNonStreamingResponse()
+
+      expect(response).toMatchObject({
+        type: 'message',
+        role: 'assistant',
+        model: 'test:model',
+        stop_reason: 'tool_use'
+      })
+
+      expect(response.content).toHaveLength(2)
+      expect(response.content[0]).toMatchObject({
+        type: 'text',
+        text: 'Hello world'
+      })
+      expect(response.content[1]).toMatchObject({
+        type: 'tool_use',
+        id: 'call_1',
+        name: 'test',
+        input: { arg: 'value' }
+      })
+
+      expect(response.usage).toMatchObject({
+        input_tokens: 10,
+        output_tokens: 20
+      })
+    })
+  })
+
+  describe('Error Handling', () => {
+    it('should throw on error events', async () => {
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: vi.fn()
+      })
+
+      const testError = new Error('Test error')
+      const stream = createMockStream([{ type: 'error', error: testError }])
+
+      await expect(adapter.processStream(stream)).rejects.toThrow('Test error')
+    })
+  })
+
+  describe('Edge Cases', () => {
+    it('should handle empty stream', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = new ReadableStream<TextStreamPart<ToolSet>>({
+        start(controller) {
+          controller.close()
+        }
+      })
+
+      await adapter.processStream(stream)
+
+      // Should still emit message_start, message_delta, and message_stop
+      expect(events.some((e) => e.type === 'message_start')).toBe(true)
+      expect(events.some((e) => e.type === 'message_delta')).toBe(true)
+      expect(events.some((e) => e.type === 'message_stop')).toBe(true)
+    })
+
+    it('should handle empty text deltas', async () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      const stream = createMockStream([createTextDelta(''), createTextDelta(''), createFinish()])
+
+      await adapter.processStream(stream)
+
+      // Should not emit deltas for empty text
+      const deltas = events.filter((e) => e.type === 'content_block_delta')
+      expect(deltas.length).toBe(0)
+    })
+  })
+
+  describe('Utility Functions', () => {
+    it('should format SSE events correctly', () => {
+      const event: RawMessageStreamEvent = {
+        type: 'message_start',
+        message: {
+          id: 'msg_123',
+          type: 'message',
+          role: 'assistant',
+          content: [],
+          model: 'test',
+          stop_reason: null,
+          stop_sequence: null,
+          usage: {
+            input_tokens: 10,
+            output_tokens: 0,
+            cache_creation_input_tokens: 0,
+            cache_read_input_tokens: 0,
+            server_tool_use: null
+          }
+        }
+      }
+
+      const formatted = formatSSEEvent(event)
+
+      expect(formatted).toContain('event: message_start')
+      expect(formatted).toContain('data: ')
+      expect(formatted).toContain('"type":"message_start"')
+      expect(formatted.endsWith('\n\n')).toBe(true)
+    })
+
+    it('should format SSE done marker correctly', () => {
+      const done = formatSSEDone()
+
+      expect(done).toBe('data: [DONE]\n\n')
+    })
+  })
+
+  describe('Message ID', () => {
+    it('should use provided message ID', () => {
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        messageId: 'custom_msg_123',
+        onEvent: vi.fn()
+      })
+
+      expect(adapter.getMessageId()).toBe('custom_msg_123')
+    })
+
+    it('should generate message ID if not provided', () => {
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: vi.fn()
+      })
+
+      const messageId = adapter.getMessageId()
+      expect(messageId).toMatch(/^msg_/)
+    })
+  })
+
+  describe('Input Tokens', () => {
+    it('should allow setting input tokens', () => {
+      const events: RawMessageStreamEvent[] = []
+      const adapter = new AiSdkToAnthropicSSE({
+        model: 'test:model',
+        onEvent: (event) => events.push(event)
+      })
+
+      adapter.setInputTokens(500)
+
+      const stream = createMockStream([createFinish()])
+
+      return adapter.processStream(stream).then(() => {
+        const messageStart = events.find((e) => e.type === 'message_start')
+        if (messageStart && messageStart.type === 'message_start') {
+          expect(messageStart.message.usage.input_tokens).toBe(500)
+        }
+      })
+    })
+  })
+})