feat(sisyphus-task): inherit parent model for categories and show fallback warning

- Change model priority: user override > parent model > category default
- Add ModelFallbackInfo to track model resolution type
- Show warning toast when category uses inherited or default model
- Add tests for model fallback info in task toast

src/features/task-toast-manager/index.ts

@@ -1,2 +1,2 @@
 export { TaskToastManager, getTaskToastManager, initTaskToastManager } from "./manager"
-export type { TrackedTask, TaskStatus, TaskToastOptions } from "./types"
+export type { TrackedTask, TaskStatus, TaskToastOptions, ModelFallbackInfo } from "./types"

src/features/task-toast-manager/manager.test.ts

@@ -142,4 +142,87 @@ describe("TaskToastManager", () => {
       expect(call.body.message).toContain("Running (1):")
     })
   })
+
+  describe("model fallback info in toast message", () => {
+    test("should display warning when model falls back to default", () => {
+      // #given - a task with model fallback to default
+      const task = {
+        id: "task_1",
+        description: "Task with default model",
+        agent: "Sisyphus-Junior",
+        isBackground: false,
+        modelInfo: { model: "anthropic/claude-sonnet-4-5", type: "default" as const },
+      }
+
+      // #when - addTask is called
+      toastManager.addTask(task)
+
+      // #then - toast should show warning with model info
+      expect(mockClient.tui.showToast).toHaveBeenCalled()
+      const call = mockClient.tui.showToast.mock.calls[0][0]
+      expect(call.body.message).toContain("⚠️")
+      expect(call.body.message).toContain("anthropic/claude-sonnet-4-5")
+      expect(call.body.message).toContain("(default)")
+    })
+
+    test("should display warning when model is inherited from parent", () => {
+      // #given - a task with inherited model
+      const task = {
+        id: "task_2",
+        description: "Task with inherited model",
+        agent: "Sisyphus-Junior",
+        isBackground: false,
+        modelInfo: { model: "cliproxy/claude-opus-4-5", type: "inherited" as const },
+      }
+
+      // #when - addTask is called
+      toastManager.addTask(task)
+
+      // #then - toast should show warning with inherited model
+      expect(mockClient.tui.showToast).toHaveBeenCalled()
+      const call = mockClient.tui.showToast.mock.calls[0][0]
+      expect(call.body.message).toContain("⚠️")
+      expect(call.body.message).toContain("cliproxy/claude-opus-4-5")
+      expect(call.body.message).toContain("(inherited)")
+    })
+
+    test("should not display model info when user-defined", () => {
+      // #given - a task with user-defined model
+      const task = {
+        id: "task_3",
+        description: "Task with user model",
+        agent: "Sisyphus-Junior",
+        isBackground: false,
+        modelInfo: { model: "my-provider/my-model", type: "user-defined" as const },
+      }
+
+      // #when - addTask is called
+      toastManager.addTask(task)
+
+      // #then - toast should NOT show model warning
+      expect(mockClient.tui.showToast).toHaveBeenCalled()
+      const call = mockClient.tui.showToast.mock.calls[0][0]
+      expect(call.body.message).not.toContain("⚠️ Model:")
+      expect(call.body.message).not.toContain("(inherited)")
+      expect(call.body.message).not.toContain("(default)")
+    })
+
+    test("should not display model info when not provided", () => {
+      // #given - a task without model info
+      const task = {
+        id: "task_4",
+        description: "Task without model info",
+        agent: "explore",
+        isBackground: true,
+      }
+
+      // #when - addTask is called
+      toastManager.addTask(task)
+
+      // #then - toast should NOT show model warning
+      expect(mockClient.tui.showToast).toHaveBeenCalled()
+      const call = mockClient.tui.showToast.mock.calls[0][0]
+      expect(call.body.message).not.toContain("⚠️ Model:")
+    })
+  })
 })

src/features/task-toast-manager/manager.ts

@@ -1,5 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
-import type { TrackedTask, TaskStatus } from "./types"
+import type { TrackedTask, TaskStatus, ModelFallbackInfo } from "./types"
 import type { ConcurrencyManager } from "../background-agent/concurrency"
 
 type OpencodeClient = PluginInput["client"]
@@ -25,6 +25,7 @@ export class TaskToastManager {
     isBackground: boolean
     status?: TaskStatus
     skills?: string[]
+    modelInfo?: ModelFallbackInfo
   }): void {
     const trackedTask: TrackedTask = {
       id: task.id,
@@ -34,6 +35,7 @@ export class TaskToastManager {
       startedAt: new Date(),
       isBackground: task.isBackground,
       skills: task.skills,
+      modelInfo: task.modelInfo,
     }
 
     this.tasks.set(task.id, trackedTask)
@@ -105,6 +107,14 @@ export class TaskToastManager {
 
     const lines: string[] = []
 
+    // Show model fallback warning for the new task if applicable
+    if (newTask.modelInfo && newTask.modelInfo.type !== "user-defined") {
+      const icon = "⚠️"
+      const suffix = newTask.modelInfo.type === "inherited" ? " (inherited)" : " (default)"
+      lines.push(`${icon} Model: ${newTask.modelInfo.model}${suffix}`)
+      lines.push("")
+    }
+
     if (running.length > 0) {
       lines.push(`Running (${running.length}):${concurrencyInfo}`)
       for (const task of running) {

src/features/task-toast-manager/types.ts

@@ -1,5 +1,10 @@
 export type TaskStatus = "running" | "queued" | "completed" | "error"
 
+export interface ModelFallbackInfo {
+  model: string
+  type: "user-defined" | "inherited" | "default"
+}
+
 export interface TrackedTask {
   id: string
   description: string
@@ -8,6 +13,7 @@ export interface TrackedTask {
   startedAt: Date
   isBackground: boolean
   skills?: string[]
+  modelInfo?: ModelFallbackInfo
 }
 
 export interface TaskToastOptions {