fix: prefix tool_choice.name when type is tool

Addresses review feedback: when tool_choice specifies a specific tool
(type: 'tool'), the name must also be prefixed to match the prefixed
tool names in the tools array.

src/integrations/claude-code/__tests__/streaming-client.spec.ts

@@ -719,6 +719,92 @@ describe("Claude Code Streaming Client", () => {
 			expect(userMessage.content[0].tool_use_id).toBe("tool_123")
 		})
 
+		test("should prefix tool name in tool_choice when type is tool", async () => {
+			const mockFetch = vi.fn().mockResolvedValue({
+				ok: true,
+				body: {
+					getReader: () => ({
+						read: vi.fn().mockResolvedValue({ done: true, value: undefined }),
+						releaseLock: vi.fn(),
+					}),
+				},
+			})
+			global.fetch = mockFetch
+
+			const { createStreamingMessage } = await import("../streaming-client")
+
+			const tools = [
+				{
+					name: "read_file",
+					description: "Read a file",
+					input_schema: { type: "object" as const, properties: {} },
+				},
+			]
+
+			const stream = createStreamingMessage({
+				accessToken: "test-token",
+				model: "claude-3-5-sonnet-20241022",
+				systemPrompt: "You are helpful",
+				messages: [{ role: "user", content: "Read a file" }],
+				tools,
+				toolChoice: { type: "tool", name: "read_file" },
+			})
+
+			// Consume the stream
+			for await (const _ of stream) {
+				// Just consume
+			}
+
+			const call = mockFetch.mock.calls[0]
+			const body = JSON.parse(call[1].body)
+
+			// tool_choice.name should be prefixed to match the prefixed tool names
+			expect(body.tool_choice).toEqual({ type: "tool", name: "oc_read_file" })
+		})
+
+		test("should not modify tool_choice when type is auto or any", async () => {
+			const mockFetch = vi.fn().mockResolvedValue({
+				ok: true,
+				body: {
+					getReader: () => ({
+						read: vi.fn().mockResolvedValue({ done: true, value: undefined }),
+						releaseLock: vi.fn(),
+					}),
+				},
+			})
+			global.fetch = mockFetch
+
+			const { createStreamingMessage } = await import("../streaming-client")
+
+			const tools = [
+				{
+					name: "read_file",
+					description: "Read a file",
+					input_schema: { type: "object" as const, properties: {} },
+				},
+			]
+
+			const stream = createStreamingMessage({
+				accessToken: "test-token",
+				model: "claude-3-5-sonnet-20241022",
+				systemPrompt: "You are helpful",
+				messages: [{ role: "user", content: "Hello" }],
+				tools,
+				toolChoice: { type: "any" },
+			})
+
+			// Consume the stream
+			for await (const _ of stream) {
+				// Just consume
+			}
+
+			const call = mockFetch.mock.calls[0]
+			const body = JSON.parse(call[1].body)
+
+			// tool_choice with type "any" should be unchanged
+			expect(body.tool_choice).toEqual({ type: "any" })
+		})
+
 		test("should strip prefix from tool names in streaming responses", async () => {
 			// Simulate a tool_use response from the API with prefixed name
 			const sseData = [

src/integrations/claude-code/streaming-client.ts

@@ -85,6 +85,28 @@ function prefixToolNamesInMessages(messages: Anthropic.Messages.MessageParam[]):
 	})
 }
 
+/**
+ * Prefixes tool name in tool_choice when type is "tool".
+ * This ensures consistency with the prefixed tool names in the tools array.
+ */
+function prefixToolChoice(
+	toolChoice: Anthropic.Messages.ToolChoice | undefined,
+): Anthropic.Messages.ToolChoice | undefined {
+	if (!toolChoice) {
+		return toolChoice
+	}
+
+	// Only prefix when tool_choice specifies a specific tool by name
+	if (toolChoice.type === "tool" && "name" in toolChoice) {
+		return {
+			...toolChoice,
+			name: prefixToolName(toolChoice.name),
+		}
+	}
+
+	return toolChoice
+}
+
 /**
  * Filters out non-Anthropic content blocks from messages before sending to the API.
  *
@@ -487,9 +509,10 @@ export async function* createStreamingMessage(options: StreamMessageOptions): As
 		// when using Claude Code OAuth tokens
 		body.tools = prefixToolNames(tools)
 		// Default tool_choice to "auto" when tools are provided (as per spec example)
-		body.tool_choice = toolChoice || { type: "auto" }
+		// Prefix tool name in tool_choice if it specifies a specific tool
+		body.tool_choice = prefixToolChoice(toolChoice) || { type: "auto" }
 	} else if (toolChoice) {
-		body.tool_choice = toolChoice
+		body.tool_choice = prefixToolChoice(toolChoice)
 	}
 
 	// Build minimal headers