diff --git a/src/features/background-agent/manager.test.ts b/src/features/background-agent/manager.test.ts
index e340af68..6d2f61e7 100644
--- a/src/features/background-agent/manager.test.ts
+++ b/src/features/background-agent/manager.test.ts
@@ -674,3 +674,95 @@ describe("LaunchInput.skillContent", () => {
     expect(input.skillContent).toBe("You are a playwright expert")
   })
 })
+
+describe("BackgroundManager.notifyParentSession - agent context preservation", () => {
+  test("should not pass agent field when parentAgent is undefined", async () => {
+    // #given
+    const task: BackgroundTask = {
+      id: "task-no-agent",
+      sessionID: "session-child",
+      parentSessionID: "session-parent",
+      parentMessageID: "msg-parent",
+      description: "task without agent context",
+      prompt: "test",
+      agent: "explore",
+      status: "completed",
+      startedAt: new Date(),
+      completedAt: new Date(),
+      parentAgent: undefined,
+      parentModel: { providerID: "anthropic", modelID: "claude-opus" },
+    }
+
+    // #when
+    const promptBody = buildNotificationPromptBody(task)
+
+    // #then
+    expect("agent" in promptBody).toBe(false)
+    expect(promptBody.model).toEqual({ providerID: "anthropic", modelID: "claude-opus" })
+  })
+
+  test("should include agent field when parentAgent is defined", async () => {
+    // #given
+    const task: BackgroundTask = {
+      id: "task-with-agent",
+      sessionID: "session-child",
+      parentSessionID: "session-parent",
+      parentMessageID: "msg-parent",
+      description: "task with agent context",
+      prompt: "test",
+      agent: "explore",
+      status: "completed",
+      startedAt: new Date(),
+      completedAt: new Date(),
+      parentAgent: "Sisyphus",
+      parentModel: { providerID: "anthropic", modelID: "claude-opus" },
+    }
+
+    // #when
+    const promptBody = buildNotificationPromptBody(task)
+
+    // #then
+    expect(promptBody.agent).toBe("Sisyphus")
+  })
+
+  test("should not pass model field when parentModel is undefined", async () => {
+    // #given
+    const task: BackgroundTask = {
+      id: "task-no-model",
+      sessionID: "session-child",
+      parentSessionID: "session-parent",
+      parentMessageID: "msg-parent",
+      description: "task without model context",
+      prompt: "test",
+      agent: "explore",
+      status: "completed",
+      startedAt: new Date(),
+      completedAt: new Date(),
+      parentAgent: "Sisyphus",
+      parentModel: undefined,
+    }
+
+    // #when
+    const promptBody = buildNotificationPromptBody(task)
+
+    // #then
+    expect("model" in promptBody).toBe(false)
+    expect(promptBody.agent).toBe("Sisyphus")
+  })
+})
+
+function buildNotificationPromptBody(task: BackgroundTask): Record<string, unknown> {
+  const body: Record<string, unknown> = {
+    parts: [{ type: "text", text: `[BACKGROUND TASK COMPLETED] Task "${task.description}" finished.` }],
+  }
+
+  if (task.parentAgent !== undefined) {
+    body.agent = task.parentAgent
+  }
+
+  if (task.parentModel?.providerID && task.parentModel?.modelID) {
+    body.model = { providerID: task.parentModel.providerID, modelID: task.parentModel.modelID }
+  }
+
+  return body
+}
diff --git a/src/features/background-agent/manager.ts b/src/features/background-agent/manager.ts
index 392d6775..ccc7ddc6 100644
--- a/src/features/background-agent/manager.ts
+++ b/src/features/background-agent/manager.ts
@@ -199,6 +199,7 @@ export class BackgroundManager {
     parentSessionID: string
     description: string
     agent?: string
+    parentAgent?: string
   }): BackgroundTask {
     const task: BackgroundTask = {
       id: input.taskId,
@@ -214,6 +215,7 @@ export class BackgroundManager {
         toolCalls: 0,
         lastUpdate: new Date(),
       },
+      parentAgent: input.parentAgent,
     }
 
     this.tasks.set(task.id, task)
@@ -440,19 +442,25 @@ export class BackgroundManager {
       }
 
       try {
-        // Use only parentModel/parentAgent - don't fallback to prevMessage
-        // This prevents accidentally changing parent session's model/agent
-        const modelField = task.parentModel?.providerID && task.parentModel?.modelID
-          ? { providerID: task.parentModel.providerID, modelID: task.parentModel.modelID }
-          : undefined
+        const body: {
+          agent?: string
+          model?: { providerID: string; modelID: string }
+          parts: Array<{ type: "text"; text: string }>
+        } = {
+          parts: [{ type: "text", text: message }],
+        }
+
+        if (task.parentAgent !== undefined) {
+          body.agent = task.parentAgent
+        }
+
+        if (task.parentModel?.providerID && task.parentModel?.modelID) {
+          body.model = { providerID: task.parentModel.providerID, modelID: task.parentModel.modelID }
+        }
 
         await this.client.session.prompt({
           path: { id: task.parentSessionID },
-          body: {
-            agent: task.parentAgent,
-            model: modelField,
-            parts: [{ type: "text", text: message }],
-          },
+          body,
           query: { directory: this.directory },
         })
         log("[background-agent] Successfully sent prompt to parent session:", { parentSessionID: task.parentSessionID })
diff --git a/src/tools/background-task/tools.ts b/src/tools/background-task/tools.ts
index 9dd39447..1f916937 100644
--- a/src/tools/background-task/tools.ts
+++ b/src/tools/background-task/tools.ts
@@ -74,7 +74,7 @@ export function createBackgroundTask(manager: BackgroundManager): ToolDefinition
           parentSessionID: ctx.sessionID,
           parentMessageID: ctx.messageID,
           parentModel,
-          parentAgent: prevMessage?.agent,
+          parentAgent: ctx.agent ?? prevMessage?.agent,
         })
 
         ctx.metadata?.({