diff --git a/src/agents/sisyphus-junior.ts b/src/agents/sisyphus-junior.ts
index 671983a10..690b3eeba 100644
--- a/src/agents/sisyphus-junior.ts
+++ b/src/agents/sisyphus-junior.ts
@@ -84,13 +84,14 @@ export const SISYPHUS_JUNIOR_DEFAULTS = {
 } as const
 
 export function createSisyphusJuniorAgentWithOverrides(
-  override: AgentOverrideConfig | undefined
+  override: AgentOverrideConfig | undefined,
+  systemDefaultModel?: string
 ): AgentConfig {
   if (override?.disable) {
     override = undefined
   }
 
-  const model = override?.model ?? SISYPHUS_JUNIOR_DEFAULTS.model
+  const model = override?.model ?? systemDefaultModel ?? SISYPHUS_JUNIOR_DEFAULTS.model
   const temperature = override?.temperature ?? SISYPHUS_JUNIOR_DEFAULTS.temperature
 
   const promptAppend = override?.prompt_append
diff --git a/src/agents/utils.ts b/src/agents/utils.ts
index 808a6ef36..d831caa87 100644
--- a/src/agents/utils.ts
+++ b/src/agents/utils.ts
@@ -192,7 +192,7 @@ export function createBuiltinAgents(
 
   if (!disabledAgents.includes("orchestrator-sisyphus")) {
     const orchestratorOverride = agentOverrides["orchestrator-sisyphus"]
-    const orchestratorModel = orchestratorOverride?.model
+    const orchestratorModel = orchestratorOverride?.model ?? systemDefaultModel
     let orchestratorConfig = createOrchestratorSisyphusAgent({
       model: orchestratorModel,
       availableAgents,
diff --git a/src/features/task-toast-manager/index.ts b/src/features/task-toast-manager/index.ts
index f779eee8c..26d91af03 100644
--- a/src/features/task-toast-manager/index.ts
+++ b/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"
diff --git a/src/features/task-toast-manager/manager.test.ts b/src/features/task-toast-manager/manager.test.ts
index 1e813ba85..9558fe8d2 100644
--- a/src/features/task-toast-manager/manager.test.ts
+++ b/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:")
+    })
+  })
 })
diff --git a/src/features/task-toast-manager/manager.ts b/src/features/task-toast-manager/manager.ts
index 66a03b2a2..20086c6ab 100644
--- a/src/features/task-toast-manager/manager.ts
+++ b/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) {
diff --git a/src/features/task-toast-manager/types.ts b/src/features/task-toast-manager/types.ts
index de4aca0a0..5132e1479 100644
--- a/src/features/task-toast-manager/types.ts
+++ b/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 {
diff --git a/src/plugin-handlers/config-handler.ts b/src/plugin-handlers/config-handler.ts
index 96ff156f6..55c4f24e5 100644
--- a/src/plugin-handlers/config-handler.ts
+++ b/src/plugin-handlers/config-handler.ts
@@ -154,7 +154,8 @@ export function createConfigHandler(deps: ConfigHandlerDeps) {
       };
 
       agentConfig["Sisyphus-Junior"] = createSisyphusJuniorAgentWithOverrides(
-        pluginConfig.agents?.["Sisyphus-Junior"]
+        pluginConfig.agents?.["Sisyphus-Junior"],
+        config.model as string | undefined
       );
 
       if (builderEnabled) {
diff --git a/src/tools/sisyphus-task/tools.ts b/src/tools/sisyphus-task/tools.ts
index d4b720793..127560e9e 100644
--- a/src/tools/sisyphus-task/tools.ts
+++ b/src/tools/sisyphus-task/tools.ts
@@ -9,6 +9,7 @@ import { findNearestMessageWithFields, findFirstMessageWithAgent, MESSAGE_STORAG
 import { resolveMultipleSkills } from "../../features/opencode-skill-loader/skill-content"
 import { createBuiltinSkills } from "../../features/builtin-skills/skills"
 import { getTaskToastManager } from "../../features/task-toast-manager"
+import type { ModelFallbackInfo } from "../../features/task-toast-manager/types"
 import { subagentSessions, getSessionAgent } from "../../features/claude-code-session-state"
 import { log } from "../../shared/logger"
 
@@ -60,7 +61,8 @@ type ToolContextWithMetadata = {
 
 function resolveCategoryConfig(
   categoryName: string,
-  userCategories?: CategoriesConfig
+  userCategories?: CategoriesConfig,
+  parentModelString?: string
 ): { config: CategoryConfig; promptAppend: string } | null {
   const defaultConfig = DEFAULT_CATEGORIES[categoryName]
   const userConfig = userCategories?.[categoryName]
@@ -70,10 +72,12 @@ function resolveCategoryConfig(
     return null
   }
 
+  // Model priority: user override > parent model (inherit) > category default > hardcoded fallback
+  // Parent model takes precedence over category default so custom providers work out-of-box
   const config: CategoryConfig = {
     ...defaultConfig,
     ...userConfig,
-    model: userConfig?.model ?? defaultConfig?.model ?? "anthropic/claude-sonnet-4-5",
+    model: userConfig?.model ?? parentModelString ?? defaultConfig?.model ?? "anthropic/claude-sonnet-4-5",
   }
 
   let promptAppend = defaultPromptAppend
@@ -329,12 +333,27 @@ ${textContent || "(No text output)"}`
       let categoryModel: { providerID: string; modelID: string; variant?: string } | undefined
       let categoryPromptAppend: string | undefined
 
+      const parentModelString = parentModel
+        ? `${parentModel.providerID}/${parentModel.modelID}`
+        : undefined
+
+      let modelInfo: ModelFallbackInfo | undefined
+
       if (args.category) {
-        const resolved = resolveCategoryConfig(args.category, userCategories)
+        const resolved = resolveCategoryConfig(args.category, userCategories, parentModelString)
         if (!resolved) {
           return `❌ Unknown category: "${args.category}". Available: ${Object.keys({ ...DEFAULT_CATEGORIES, ...userCategories }).join(", ")}`
         }
 
+        const userHasDefinedCategory = userCategories?.[args.category]?.model !== undefined
+        if (userHasDefinedCategory) {
+          modelInfo = { model: resolved.config.model, type: "user-defined" }
+        } else if (parentModelString) {
+          modelInfo = { model: parentModelString, type: "inherited" }
+        } else if (DEFAULT_CATEGORIES[args.category]?.model) {
+          modelInfo = { model: DEFAULT_CATEGORIES[args.category].model, type: "default" }
+        }
+
         agentToUse = SISYPHUS_JUNIOR_AGENT
         const parsedModel = parseModelString(resolved.config.model)
         categoryModel = parsedModel
@@ -448,6 +467,7 @@ System notifies on completion. Use \`background_output\` with task_id="${task.id
             agent: agentToUse,
             isBackground: false,
             skills: args.skills,
+            modelInfo,
           })
         }