feat(plugin): surface agent and parentAgent in plugin hook input

packages/opencode/src/session/message-v2.ts

@@ -356,6 +356,7 @@ export namespace MessageV2 {
       })
       .optional(),
     agent: z.string(),
+    parentAgent: z.string().optional(),
     model: z.object({
       providerID: z.string(),
       modelID: z.string(),

packages/opencode/src/session/prompt.ts

@@ -98,6 +98,7 @@ export namespace SessionPrompt {
       })
       .optional(),
     agent: z.string().optional(),
+    parentAgent: z.string().optional(),
     noReply: z.boolean().optional(),
     tools: z
       .record(z.string(), z.boolean())
@@ -409,6 +410,8 @@ export namespace SessionPrompt {
             tool: "task",
             sessionID,
             callID: part.id,
+            agent: lastUser.agent,
+            parentAgent: lastUser.parentAgent,
           },
           { args: taskArgs },
         )
@@ -458,6 +461,8 @@ export namespace SessionPrompt {
             sessionID,
             callID: part.id,
             args: taskArgs,
+            agent: lastUser.agent,
+            parentAgent: lastUser.parentAgent,
           },
           result,
         )
@@ -607,6 +612,7 @@ export namespace SessionPrompt {
         processor,
         bypassAgentCheck,
         messages: msgs,
+        parentAgent: lastUser.parentAgent,
       })
 
       // Inject StructuredOutput tool if JSON schema mode enabled
@@ -739,6 +745,7 @@ export namespace SessionPrompt {
     processor: SessionProcessor.Info
     bypassAgentCheck: boolean
     messages: MessageV2.WithParts[]
+    parentAgent?: string
   }) {
     using _ = log.time("resolveTools")
     const tools: Record<string, AITool> = {}
@@ -795,6 +802,8 @@ export namespace SessionPrompt {
               tool: item.id,
               sessionID: ctx.sessionID,
               callID: ctx.callID,
+              agent: ctx.agent,
+              parentAgent: input.parentAgent,
             },
             {
               args,
@@ -817,6 +826,8 @@ export namespace SessionPrompt {
               sessionID: ctx.sessionID,
               callID: ctx.callID,
               args,
+              agent: ctx.agent,
+              parentAgent: input.parentAgent,
             },
             output,
           )
@@ -841,6 +852,8 @@ export namespace SessionPrompt {
             tool: key,
             sessionID: ctx.sessionID,
             callID: opts.toolCallId,
+            agent: ctx.agent,
+            parentAgent: input.parentAgent,
           },
           {
             args,
@@ -863,6 +876,8 @@ export namespace SessionPrompt {
             sessionID: ctx.sessionID,
             callID: opts.toolCallId,
             args,
+            agent: ctx.agent,
+            parentAgent: input.parentAgent,
           },
           result,
         )
@@ -970,6 +985,7 @@ export namespace SessionPrompt {
       },
       tools: input.tools,
       agent: agent.name,
+      parentAgent: input.parentAgent,
       model,
       system: input.system,
       format: input.format,
@@ -1461,6 +1477,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
   export const ShellInput = z.object({
     sessionID: Identifier.schema("session"),
     agent: z.string(),
+    parentAgent: z.string().optional(),
     model: z
       .object({
         providerID: z.string(),
@@ -1620,7 +1637,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
     const cwd = Instance.directory
     const shellEnv = await Plugin.trigger(
       "shell.env",
-      { cwd, sessionID: input.sessionID, callID: part.callID },
+      { cwd, sessionID: input.sessionID, callID: part.callID, agent: input.agent, parentAgent: input.parentAgent },
       { env: {} },
     )
     const proc = spawn(shell, args, {

packages/opencode/src/tool/task.ts

@@ -133,6 +133,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
           providerID: model.providerID,
         },
         agent: agent.name,
+        parentAgent: ctx.agent,
         tools: {
           todowrite: false,
           todoread: false,

packages/opencode/test/plugin/parent-agent.test.ts

@@ -0,0 +1,59 @@
+import { describe, expect, test } from "bun:test"
+import { SessionPrompt } from "../../src/session/prompt"
+import { MessageV2 } from "../../src/session/message-v2"
+
+describe("parentAgent hook input", () => {
+  test("PromptInput accepts parentAgent", () => {
+    const input = SessionPrompt.PromptInput.parse({
+      sessionID: "ses_test",
+      agent: "scout",
+      parentAgent: "coder",
+      parts: [{ type: "text", text: "test" }],
+    })
+    expect(input.parentAgent).toBe("coder")
+  })
+
+  test("PromptInput parentAgent is optional", () => {
+    const input = SessionPrompt.PromptInput.parse({
+      sessionID: "ses_test",
+      agent: "scout",
+      parts: [{ type: "text", text: "test" }],
+    })
+    expect(input.parentAgent).toBeUndefined()
+  })
+
+  test("ShellInput accepts parentAgent", () => {
+    const input = SessionPrompt.ShellInput.parse({
+      sessionID: "ses_test",
+      agent: "coder",
+      parentAgent: "orchestrator",
+      command: "ls",
+    })
+    expect(input.parentAgent).toBe("orchestrator")
+  })
+
+  test("UserMessage stores parentAgent", () => {
+    const msg = MessageV2.User.parse({
+      id: "msg_test",
+      sessionID: "ses_test",
+      role: "user",
+      time: { created: Date.now() },
+      agent: "scout",
+      parentAgent: "coder",
+      model: { providerID: "test", modelID: "test" },
+    })
+    expect(msg.parentAgent).toBe("coder")
+  })
+
+  test("UserMessage parentAgent is optional (top-level agent)", () => {
+    const msg = MessageV2.User.parse({
+      id: "msg_test",
+      sessionID: "ses_test",
+      role: "user",
+      time: { created: Date.now() },
+      agent: "coder",
+      model: { providerID: "test", modelID: "test" },
+    })
+    expect(msg.parentAgent).toBeUndefined()
+  })
+})

packages/plugin/src/index.ts

@@ -182,15 +182,15 @@ export interface Hooks {
     output: { parts: Part[] },
   ) => Promise<void>
   "tool.execute.before"?: (
-    input: { tool: string; sessionID: string; callID: string },
+    input: { tool: string; sessionID: string; callID: string; agent?: string; parentAgent?: string },
     output: { args: any },
   ) => Promise<void>
   "shell.env"?: (
-    input: { cwd: string; sessionID?: string; callID?: string },
+    input: { cwd: string; sessionID?: string; callID?: string; agent?: string; parentAgent?: string },
     output: { env: Record<string, string> },
   ) => Promise<void>
   "tool.execute.after"?: (
-    input: { tool: string; sessionID: string; callID: string; args: any },
+    input: { tool: string; sessionID: string; callID: string; args: any; agent?: string; parentAgent?: string },
     output: {
       title: string
       output: string