diff --git a/src/api/providers/__tests__/opencode-go.spec.ts b/src/api/providers/__tests__/opencode-go.spec.ts
index 828ffb8655..7415ea73b1 100644
--- a/src/api/providers/__tests__/opencode-go.spec.ts
+++ b/src/api/providers/__tests__/opencode-go.spec.ts
@@ -22,6 +22,7 @@ import {
 import { OpencodeGoHandler } from "../opencode-go"
 import { getModels } from "../fetchers/modelCache"
 import { ApiHandlerOptions } from "../../../shared/api"
+import { Package } from "../../../shared/package"
 import { asyncStreamFrom, collectStream } from "../../../test-utils/stream"
 import { clearAllMocks } from "../../../test-utils/reset"
 
@@ -94,6 +95,7 @@ describe("OpencodeGoHandler", () => {
 			expect.objectContaining({
 				baseURL: "https://opencode.ai/zen/go/v1",
 				apiKey: "test-key",
+				defaultHeaders: expect.objectContaining({ "User-Agent": `ZooCode/${Package.version}` }),
 			}),
 		)
 	})
@@ -106,6 +108,7 @@ describe("OpencodeGoHandler", () => {
 				// NOT include the trailing `/v1` used by the OpenAI client.
 				baseURL: "https://opencode.ai/zen/go",
 				apiKey: "test-key",
+				defaultHeaders: expect.objectContaining({ "User-Agent": `ZooCode/${Package.version}` }),
 			}),
 		)
 	})
@@ -208,6 +211,17 @@ describe("OpencodeGoHandler", () => {
 			)
 		})
 
+		it("sends the stable conversation ID to chat completions", async () => {
+			const handler = new OpencodeGoHandler(mockOptions)
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hi" }]
+
+			await collectStream(handler.createMessage("sys", messages, { taskId: "conversation-123" }))
+
+			expect(mockCreate.mock.calls[0][1]?.headers).toMatchObject({
+				"x-opencode-session": "conversation-123",
+			})
+		})
+
 		it("forwards the model's default reasoning_effort for reasoning-capable models", async () => {
 			const handler = new OpencodeGoHandler(mockOptions)
 			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hi" }]
@@ -478,6 +492,17 @@ describe("OpencodeGoHandler", () => {
 			expect(mockCreate).not.toHaveBeenCalled()
 		})
 
+		it("sends the stable conversation ID to the Anthropic messages endpoint", async () => {
+			const handler = new OpencodeGoHandler(anthropicOptions)
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hi" }]
+
+			await collectStream(handler.createMessage("sys", messages, { taskId: "conversation-123" }))
+
+			expect(mockAnthropicCreate.mock.calls[0][1]?.headers).toMatchObject({
+				"x-opencode-session": "conversation-123",
+			})
+		})
+
 		it("streams text, tool-call, usage and cost chunks from the Anthropic stream", async () => {
 			const handler = new OpencodeGoHandler(anthropicOptions)
 			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hi" }]
@@ -845,7 +870,10 @@ describe("OpencodeGoHandler", () => {
 				handler.createMessage("sys", messages, { taskId: "test-task", abortSignal: controller.signal }),
 			)
 
-			expect(mockResponsesCreate.mock.calls[0][1]).toEqual({ signal: controller.signal })
+			expect(mockResponsesCreate.mock.calls[0][1]).toEqual({
+				signal: controller.signal,
+				headers: { "x-opencode-session": "test-task" },
+			})
 		})
 
 		it("closes the Responses iterator when the consumer stops early", async () => {
diff --git a/src/api/providers/opencode-go.ts b/src/api/providers/opencode-go.ts
index 1f4faa45d6..bbfa63780a 100644
--- a/src/api/providers/opencode-go.ts
+++ b/src/api/providers/opencode-go.ts
@@ -247,7 +247,11 @@ export class OpencodeGoHandler extends RouterProvider implements SingleCompletio
 			}),
 		}
 
-		const completion = await this.client.chat.completions.create(body)
+		const completion = metadata?.taskId
+			? await this.client.chat.completions.create(body, {
+					headers: { "x-opencode-session": metadata.taskId },
+				})
+			: await this.client.chat.completions.create(body)
 
 		for await (const chunk of completion) {
 			const delta = chunk.choices[0]?.delta
@@ -378,7 +382,10 @@ export class OpencodeGoHandler extends RouterProvider implements SingleCompletio
 
 		let stream: AsyncIterable<OpenAI.Responses.ResponseStreamEvent>
 		try {
-			stream = await this.client.responses.create(requestBody, { signal: metadata?.abortSignal })
+			stream = await this.client.responses.create(requestBody, {
+				signal: metadata?.abortSignal,
+				headers: metadata?.taskId ? { "x-opencode-session": metadata.taskId } : undefined,
+			})
 		} catch (error) {
 			if (error instanceof Error) {
 				throw new Error(`Opencode Go completion error: ${error.message}`)
@@ -505,7 +512,11 @@ export class OpencodeGoHandler extends RouterProvider implements SingleCompletio
 		// errors propagate unchanged, matching the OpenAI streaming path.
 		let stream
 		try {
-			stream = await this.anthropicClient.messages.create(requestParams)
+			stream = metadata?.taskId
+				? await this.anthropicClient.messages.create(requestParams, {
+						headers: { "x-opencode-session": metadata.taskId },
+					})
+				: await this.anthropicClient.messages.create(requestParams)
 		} catch (error) {
 			if (error instanceof Error) {
 				throw new Error(`Opencode Go completion error: ${error.message}`)