fix(opencode): set x-initiator header for compaction and synthetic messages

Author: aklajnert

packages/opencode/src/plugin/github-copilot/copilot.ts

@@ -316,7 +316,13 @@ export async function CopilotAuthPlugin(input: PluginInput): Promise<Hooks> {
         output.headers["anthropic-beta"] = "interleaved-thinking-2025-05-14"
       }
 
-      const parts = await sdk.session
+      const agentName = typeof incoming.agent === "string" ? incoming.agent : (incoming.agent as { name: string }).name
+      if (agentName === "compaction") {
+        output.headers["x-initiator"] = "agent"
+        return
+      }
+
+      const msg = await sdk.session
         .message({
           path: {
             id: incoming.message.sessionID,
@@ -325,11 +331,14 @@ export async function CopilotAuthPlugin(input: PluginInput): Promise<Hooks> {
           query: {
             directory: input.directory,
           },
-          throwOnError: true,
         })
         .catch(() => undefined)
 
-      if (parts?.data.parts?.some((part) => part.type === "compaction")) {
+      const parts = msg?.data?.parts
+      const synthetic =
+        !!parts?.length && parts.every((p) => "synthetic" in p && (p as { synthetic?: boolean }).synthetic === true)
+
+      if (parts?.some((part) => part.type === "compaction") || synthetic) {
         output.headers["x-initiator"] = "agent"
         return
       }
@@ -342,10 +351,9 @@ export async function CopilotAuthPlugin(input: PluginInput): Promise<Hooks> {
           query: {
             directory: input.directory,
           },
-          throwOnError: true,
         })
         .catch(() => undefined)
-      if (!session || !session.data.parentID) return
+      if (!session || !session.data?.parentID) return
       // mark subagent sessions as agent initiated matching standard that other copilot tools have
       output.headers["x-initiator"] = "agent"
     },

packages/opencode/test/plugin/github-copilot.test.ts

@@ -0,0 +1,129 @@
+import { describe, expect, mock, test } from "bun:test"
+import type { Hooks, PluginInput } from "@opencode-ai/plugin"
+import { CopilotAuthPlugin } from "../../src/plugin/github-copilot/copilot"
+
+type ChatInput = Parameters<NonNullable<Hooks["chat.headers"]>>[0]
+type ChatOutput = Parameters<NonNullable<Hooks["chat.headers"]>>[1]
+
+function model() {
+  return {
+    providerID: "github-copilot",
+    api: {
+      npm: "@ai-sdk/github-copilot",
+    },
+  } as ChatInput["model"]
+}
+
+function incoming(input?: Partial<ChatInput>): ChatInput {
+  return {
+    sessionID: "session",
+    agent: "build",
+    model: model(),
+    provider: {} as ChatInput["provider"],
+    message: {
+      id: "message",
+      sessionID: "session",
+    } as ChatInput["message"],
+    ...input,
+  }
+}
+
+async function plugin(input?: { message?: () => Promise<unknown>; session?: () => Promise<unknown> }) {
+  const client = {
+    session: {
+      message: mock(input?.message ?? (() => Promise.resolve({ data: { parts: [] } }))),
+      get: mock(input?.session ?? (() => Promise.resolve({ data: {} }))),
+    },
+  }
+
+  const hooks = await CopilotAuthPlugin({
+    client: client as unknown as PluginInput["client"],
+    directory: "/tmp",
+    project: {} as PluginInput["project"],
+    worktree: "/tmp",
+    serverUrl: new URL("http://localhost:4096"),
+    $: Bun.$,
+  })
+
+  return { hooks, client }
+}
+
+describe("plugin.github-copilot", () => {
+  test("marks compaction agent requests as agent initiated", async () => {
+    const { hooks, client } = await plugin({
+      message: () => Promise.reject(new Error("should not fetch message")),
+    })
+    const output: ChatOutput = { headers: {} }
+
+    await hooks["chat.headers"]?.(
+      incoming({
+        agent: "compaction",
+      }),
+      output,
+    )
+
+    expect(output.headers["x-initiator"]).toBe("agent")
+    expect(client.session.message).not.toHaveBeenCalled()
+    expect(client.session.get).not.toHaveBeenCalled()
+  })
+
+  test("marks synthetic-only follow-up messages as agent initiated", async () => {
+    const { hooks } = await plugin({
+      message: () =>
+        Promise.resolve({
+          data: {
+            parts: [{ type: "text", synthetic: true }],
+          },
+        }),
+    })
+    const output: ChatOutput = { headers: {} }
+
+    await hooks["chat.headers"]?.(incoming(), output)
+
+    expect(output.headers["x-initiator"]).toBe("agent")
+  })
+
+  test("marks auto-compaction marker messages as agent initiated", async () => {
+    const { hooks } = await plugin({
+      message: () =>
+        Promise.resolve({
+          data: {
+            parts: [
+              {
+                type: "text",
+                text: "[auto-compaction-followup]",
+                synthetic: true,
+              },
+              {
+                type: "text",
+                text: "Continue if you have next steps",
+                synthetic: true,
+              },
+            ],
+          },
+        }),
+    })
+    const output: ChatOutput = { headers: {} }
+
+    await hooks["chat.headers"]?.(incoming(), output)
+
+    expect(output.headers["x-initiator"]).toBe("agent")
+  })
+
+  test("does not override normal top-level user messages", async () => {
+    const { hooks } = await plugin({
+      message: () =>
+        Promise.resolve({
+          data: {
+            parts: [{ type: "text", text: "hello" }],
+          },
+        }),
+      session: () => Promise.resolve({ data: {} }),
+    })
+    const output: ChatOutput = { headers: {} }
+
+    await hooks["chat.headers"]?.(incoming(), output)
+
+    expect(output.headers["x-initiator"]).toBeUndefined()
+  })
+})