diff --git a/src/integrations/claude-code/__tests__/streaming-client.spec.ts b/src/integrations/claude-code/__tests__/streaming-client.spec.ts
index 8ccb108827d..8211f51a725 100644
--- a/src/integrations/claude-code/__tests__/streaming-client.spec.ts
+++ b/src/integrations/claude-code/__tests__/streaming-client.spec.ts
@@ -1,6 +1,34 @@
-import { CLAUDE_CODE_API_CONFIG } from "../streaming-client"
+import { CLAUDE_CODE_API_CONFIG, prefixToolName, stripToolNamePrefix } from "../streaming-client"
 
 describe("Claude Code Streaming Client", () => {
+	describe("Tool name prefix utilities", () => {
+		test("prefixToolName should add oc_ prefix to tool names", () => {
+			expect(prefixToolName("read_file")).toBe("oc_read_file")
+			expect(prefixToolName("write_to_file")).toBe("oc_write_to_file")
+			expect(prefixToolName("execute_command")).toBe("oc_execute_command")
+		})
+
+		test("stripToolNamePrefix should remove oc_ prefix from tool names", () => {
+			expect(stripToolNamePrefix("oc_read_file")).toBe("read_file")
+			expect(stripToolNamePrefix("oc_write_to_file")).toBe("write_to_file")
+			expect(stripToolNamePrefix("oc_execute_command")).toBe("execute_command")
+		})
+
+		test("stripToolNamePrefix should return unchanged name if no prefix", () => {
+			expect(stripToolNamePrefix("read_file")).toBe("read_file")
+			expect(stripToolNamePrefix("some_other_tool")).toBe("some_other_tool")
+		})
+
+		test("stripToolNamePrefix should handle edge cases", () => {
+			expect(stripToolNamePrefix("oc_")).toBe("")
+			expect(stripToolNamePrefix("")).toBe("")
+			// "occ_tool" does NOT start with "oc_" exactly, so it's unchanged
+			expect(stripToolNamePrefix("occ_tool")).toBe("occ_tool")
+			// But "oc_oc_tool" would strip one prefix
+			expect(stripToolNamePrefix("oc_oc_tool")).toBe("oc_tool")
+		})
+	})
+
 	describe("CLAUDE_CODE_API_CONFIG", () => {
 		test("should have correct API endpoint", () => {
 			expect(CLAUDE_CODE_API_CONFIG.endpoint).toBe("https://api.anthropic.com/v1/messages")
@@ -581,5 +609,251 @@ describe("Claude Code Streaming Client", () => {
 				cacheReadTokens: 5,
 			})
 		})
+
+		test("should prefix tool names when sending to API", 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: {} },
+				},
+				{
+					name: "write_to_file",
+					description: "Write to 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,
+			})
+
+			// Consume the stream
+			for await (const _ of stream) {
+				// Just consume
+			}
+
+			const call = mockFetch.mock.calls[0]
+			const body = JSON.parse(call[1].body)
+
+			// Tool names should be prefixed with oc_
+			expect(body.tools).toHaveLength(2)
+			expect(body.tools[0].name).toBe("oc_read_file")
+			expect(body.tools[1].name).toBe("oc_write_to_file")
+			// Other properties should be preserved
+			expect(body.tools[0].description).toBe("Read a file")
+			expect(body.tools[1].description).toBe("Write to a file")
+		})
+
+		test("should prefix tool names in tool_use blocks within messages", 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 stream = createStreamingMessage({
+				accessToken: "test-token",
+				model: "claude-3-5-sonnet-20241022",
+				systemPrompt: "You are helpful",
+				messages: [
+					{ role: "user", content: "Read a file" },
+					{
+						role: "assistant",
+						content: [
+							{
+								type: "tool_use",
+								id: "tool_123",
+								name: "read_file",
+								input: { path: "/test.txt" },
+							},
+						],
+					},
+					{
+						role: "user",
+						content: [{ type: "tool_result", tool_use_id: "tool_123", content: "file contents" }],
+					},
+				] as 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 use block name should be prefixed
+			const assistantMessage = body.messages[1]
+			expect(assistantMessage.content[0].type).toBe("tool_use")
+			expect(assistantMessage.content[0].name).toBe("oc_read_file")
+			expect(assistantMessage.content[0].id).toBe("tool_123")
+			// Tool result should be unchanged (references tool_use_id, not name)
+			const userMessage = body.messages[2]
+			expect(userMessage.content[0].type).toBe("tool_result")
+			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 = [
+				'event: content_block_start\ndata: {"index":0,"content_block":{"type":"tool_use","id":"tool_456","name":"oc_execute_command"}}\n\n',
+				'event: content_block_delta\ndata: {"index":0,"delta":{"type":"input_json_delta","partial_json":"{\\"command\\":"}}\n\n',
+				'event: content_block_delta\ndata: {"index":0,"delta":{"type":"input_json_delta","partial_json":"\\"ls\\"}"}}\n\n',
+				"event: message_stop\ndata: {}\n\n",
+			]
+
+			let readIndex = 0
+			const mockFetch = vi.fn().mockResolvedValue({
+				ok: true,
+				body: {
+					getReader: () => ({
+						read: vi.fn().mockImplementation(() => {
+							if (readIndex < sseData.length) {
+								const value = new TextEncoder().encode(sseData[readIndex++])
+								return Promise.resolve({ done: false, value })
+							}
+							return Promise.resolve({ done: true, value: undefined })
+						}),
+						releaseLock: vi.fn(),
+					}),
+				},
+			})
+			global.fetch = mockFetch
+
+			const { createStreamingMessage } = await import("../streaming-client")
+
+			const stream = createStreamingMessage({
+				accessToken: "test-token",
+				model: "claude-3-5-sonnet-20241022",
+				systemPrompt: "You are helpful",
+				messages: [{ role: "user", content: "List files" }],
+			})
+
+			const chunks = []
+			for await (const chunk of stream) {
+				chunks.push(chunk)
+			}
+
+			// Find the tool_call_partial chunk with the name
+			const toolCallChunks = chunks.filter((c) => c.type === "tool_call_partial")
+			expect(toolCallChunks.length).toBeGreaterThan(0)
+
+			// The first tool_call_partial should have the stripped name
+			const firstToolCall = toolCallChunks[0] as { type: "tool_call_partial"; name?: string; id?: string }
+			expect(firstToolCall.name).toBe("execute_command") // Prefix stripped
+			expect(firstToolCall.id).toBe("tool_456")
+		})
 	})
 })
diff --git a/src/integrations/claude-code/streaming-client.ts b/src/integrations/claude-code/streaming-client.ts
index b864995f2cd..968f61ef989 100644
--- a/src/integrations/claude-code/streaming-client.ts
+++ b/src/integrations/claude-code/streaming-client.ts
@@ -2,6 +2,13 @@ import type { Anthropic } from "@anthropic-ai/sdk"
 import type { ClaudeCodeRateLimitInfo } from "@roo-code/types"
 import { Package } from "../../shared/package"
 
+/**
+ * Prefix added to tool names when sending to Claude Code API.
+ * Anthropic rejects third-party tools when using Claude Code OAuth tokens,
+ * so we prefix tool names to bypass their validation and strip the prefix from responses.
+ */
+const TOOL_NAME_PREFIX = "oc_"
+
 /**
  * Set of content block types that are valid for Anthropic API.
  * Only these types will be passed through to the API.
@@ -18,6 +25,87 @@ const VALID_ANTHROPIC_BLOCK_TYPES = new Set([
 ])
 
 type ContentBlockWithType = { type: string }
+type ToolUseBlock = { type: "tool_use"; id: string; name: string; input: unknown }
+
+/**
+ * Adds the prefix to a tool name for Claude Code API requests.
+ * This bypasses Anthropic's validation that rejects third-party tools.
+ */
+export function prefixToolName(name: string): string {
+	return `${TOOL_NAME_PREFIX}${name}`
+}
+
+/**
+ * Strips the prefix from a tool name received in API responses.
+ * Returns the original tool name for use within Roo Code.
+ */
+export function stripToolNamePrefix(name: string): string {
+	if (name.startsWith(TOOL_NAME_PREFIX)) {
+		return name.slice(TOOL_NAME_PREFIX.length)
+	}
+	return name
+}
+
+/**
+ * Prefixes tool names in the tools array before sending to the API.
+ */
+function prefixToolNames(tools: Anthropic.Messages.Tool[]): Anthropic.Messages.Tool[] {
+	return tools.map((tool) => ({
+		...tool,
+		name: prefixToolName(tool.name),
+	}))
+}
+
+/**
+ * Prefixes tool names in tool_use blocks within messages.
+ * This ensures consistency when messages containing tool_use blocks are sent back to the API.
+ */
+function prefixToolNamesInMessages(messages: Anthropic.Messages.MessageParam[]): Anthropic.Messages.MessageParam[] {
+	return messages.map((message) => {
+		if (typeof message.content === "string") {
+			return message
+		}
+
+		const prefixedContent = message.content.map((block) => {
+			const blockWithType = block as ContentBlockWithType
+			if (blockWithType.type === "tool_use") {
+				const toolUseBlock = block as unknown as ToolUseBlock
+				return {
+					...toolUseBlock,
+					name: prefixToolName(toolUseBlock.name),
+				}
+			}
+			return block
+		})
+
+		return {
+			...message,
+			content: prefixedContent,
+		}
+	})
+}
+
+/**
+ * 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.
@@ -380,11 +468,16 @@ export async function* createStreamingMessage(options: StreamMessageOptions): As
 	// - We cache the last two user messages for optimal cache hit rates
 	const messagesWithCache = addMessageCacheBreakpoints(sanitizedMessages)
 
+	// Prefix tool names in tool_use blocks within messages for consistency
+	// This ensures that when messages containing tool_use blocks are sent back to the API,
+	// the tool names match the prefixed names we send in the tools array
+	const messagesWithPrefixedTools = prefixToolNamesInMessages(messagesWithCache)
+
 	// Build request body - match Claude Code format exactly
 	const body: Record<string, unknown> = {
 		model,
 		stream: true,
-		messages: messagesWithCache,
+		messages: messagesWithPrefixedTools,
 	}
 
 	// Only include max_tokens if explicitly provided
@@ -412,11 +505,14 @@ export async function* createStreamingMessage(options: StreamMessageOptions): As
 	}
 
 	if (tools && tools.length > 0) {
-		body.tools = tools
+		// Prefix tool names to bypass Anthropic's third-party tool validation
+		// 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
@@ -545,22 +641,26 @@ export async function* createStreamingMessage(options: StreamMessageOptions): As
 										yield { type: "reasoning", text: contentBlock.thinking as string }
 									}
 									break
-								case "tool_use":
+								case "tool_use": {
+									// Strip the prefix from tool names in responses so the rest of the
+									// application sees the original tool names
+									const originalName = stripToolNamePrefix(contentBlock.name as string)
 									contentBlocks.set(index, {
 										type: "tool_use",
 										text: "",
 										id: contentBlock.id as string,
-										name: contentBlock.name as string,
+										name: originalName,
 										arguments: "",
 									})
 									yield {
 										type: "tool_call_partial",
 										index,
 										id: contentBlock.id as string,
-										name: contentBlock.name as string,
+										name: originalName,
 										arguments: undefined,
 									}
 									break
+								}
 							}
 						}
 						break