diff --git a/src/agent/promptAssets.ts b/src/agent/promptAssets.ts
index a531653..41602c5 100644
--- a/src/agent/promptAssets.ts
+++ b/src/agent/promptAssets.ts
@@ -279,6 +279,18 @@ export async function validateSystemPromptPreset(
   );
 }
 
+/**
+ * Returns true if the agent is not on the current default preset
+ * and would benefit from switching to `/system default`.
+ */
+export function shouldRecommendDefaultPrompt(
+  currentPrompt: string,
+  memoryMode: MemoryPromptMode,
+): boolean {
+  const defaultPrompt = buildSystemPrompt("default", memoryMode);
+  return currentPrompt !== defaultPrompt;
+}
+
 /**
  * Resolve a prompt ID and build the full system prompt with memory addon.
  * Known presets are rebuilt deterministically; unknown IDs (subagent names)
diff --git a/src/cli/App.tsx b/src/cli/App.tsx
index 4cdd308..f948a09 100644
--- a/src/cli/App.tsx
+++ b/src/cli/App.tsx
@@ -59,7 +59,10 @@ import {
   getModelShortName,
   type ModelReasoningEffort,
 } from "../agent/model";
-import { INTERRUPT_RECOVERY_ALERT } from "../agent/promptAssets";
+import {
+  INTERRUPT_RECOVERY_ALERT,
+  shouldRecommendDefaultPrompt,
+} from "../agent/promptAssets";
 import { recordSessionEnd } from "../agent/sessionHistory";
 import { SessionStats } from "../agent/stats";
 import {
@@ -1022,6 +1025,15 @@ export default function App({
     setAgentState((prev) => (prev ? { ...prev, name } : prev));
   }, []);
 
+  // Check if the current agent would benefit from switching to the default prompt
+  const shouldShowDefaultPromptTip = useCallback(() => {
+    if (!agentState?.id || !agentState.system) return false;
+    const memMode = settingsManager.isMemfsEnabled(agentState.id)
+      ? "memfs"
+      : ("standard" as const);
+    return shouldRecommendDefaultPrompt(agentState.system, memMode);
+  }, [agentState]);
+
   const projectDirectory = process.cwd();
 
   // Track current conversation (always created fresh on startup)
@@ -3093,6 +3105,8 @@ export default function App({
         ? `Resuming conversation with **${agentName}**`
         : `Starting new conversation with **${agentName}**`;
 
+      const showPromptTip = shouldShowDefaultPromptTip();
+
       // Command hints - vary based on agent state:
       // - Resuming: show /new (they may want a fresh conversation)
       // - New session + unpinned: show /pin (they should save their agent)
@@ -3104,6 +3118,9 @@ export default function App({
             "→ **/new**       start a new conversation",
             "→ **/init**      initialize your agent's memory",
             "→ **/remember**  teach your agent",
+            ...(showPromptTip
+              ? ["→ **/system**    upgrade to the latest default prompt"]
+              : []),
           ]
         : isPinned
           ? [
@@ -3112,6 +3129,9 @@ export default function App({
               "→ **/memory**    view your agent's memory",
               "→ **/init**      initialize your agent's memory",
               "→ **/remember**  teach your agent",
+              ...(showPromptTip
+                ? ["→ **/system**    upgrade to the latest default prompt"]
+                : []),
             ]
           : [
               "→ **/agents**    list all agents",
@@ -3119,6 +3139,9 @@ export default function App({
               "→ **/pin**       save + name your agent",
               "→ **/init**      initialize your agent's memory",
               "→ **/remember**  teach your agent",
+              ...(showPromptTip
+                ? ["→ **/system**    upgrade to the latest default prompt"]
+                : []),
             ];
 
       // Build status lines with optional release notes above header
@@ -3154,6 +3177,7 @@ export default function App({
     agentProvenance,
     resumedExistingConversation,
     releaseNotes,
+    shouldShowDefaultPromptTip,
   ]);
 
   // Fetch llmConfig when agent is ready
@@ -12840,6 +12864,9 @@ If using apply_patch, use this exact relative patch path: ${applyPatchRelativePa
           ? `Starting new conversation with **${agentName}**`
           : "Creating a new agent";
 
+      // Only show prompt tip for existing agents, not brand new ones
+      const showPromptTip = continueSession && shouldShowDefaultPromptTip();
+
       // Command hints - for pinned agents show /memory, for unpinned show /pin
       const commandHints = isPinned
         ? [
@@ -12848,6 +12875,9 @@ If using apply_patch, use this exact relative patch path: ${applyPatchRelativePa
             "→ **/memory**    view your agent's memory",
             "→ **/init**      initialize your agent's memory",
             "→ **/remember**  teach your agent",
+            ...(showPromptTip
+              ? ["→ **/system**    upgrade to the latest default prompt"]
+              : []),
           ]
         : [
             "→ **/agents**    list all agents",
@@ -12855,6 +12885,9 @@ If using apply_patch, use this exact relative patch path: ${applyPatchRelativePa
             "→ **/pin**       save + name your agent",
             "→ **/init**      initialize your agent's memory",
             "→ **/remember**  teach your agent",
+            ...(showPromptTip
+              ? ["→ **/system**    upgrade to the latest default prompt"]
+              : []),
           ];
 
       // Build status lines with optional release notes above header
@@ -12889,6 +12922,7 @@ If using apply_patch, use this exact relative patch path: ${applyPatchRelativePa
     agentState,
     refreshDerived,
     releaseNotes,
+    shouldShowDefaultPromptTip,
   ]);
 
   const liveTrajectorySnapshot =
diff --git a/src/tests/agent/memoryPrompt.test.ts b/src/tests/agent/memoryPrompt.test.ts
index 606106d..e072ed1 100644
--- a/src/tests/agent/memoryPrompt.test.ts
+++ b/src/tests/agent/memoryPrompt.test.ts
@@ -5,6 +5,7 @@ import {
   isKnownPreset,
   SYSTEM_PROMPT_MEMFS_ADDON,
   SYSTEM_PROMPT_MEMORY_ADDON,
+  shouldRecommendDefaultPrompt,
   swapMemoryAddon,
 } from "../../agent/promptAssets";
 
@@ -151,3 +152,32 @@ describe("swapMemoryAddon", () => {
     expect(countOccurrences(twice, "# See what changed")).toBe(1);
   });
 });
+
+describe("shouldRecommendDefaultPrompt", () => {
+  test("returns false when prompt matches current default (standard)", () => {
+    const current = buildSystemPrompt("default", "standard");
+    expect(shouldRecommendDefaultPrompt(current, "standard")).toBe(false);
+  });
+
+  test("returns false when prompt matches current default (memfs)", () => {
+    const current = buildSystemPrompt("default", "memfs");
+    expect(shouldRecommendDefaultPrompt(current, "memfs")).toBe(false);
+  });
+
+  test("returns true for a different preset", () => {
+    const current = buildSystemPrompt("letta-claude", "standard");
+    expect(shouldRecommendDefaultPrompt(current, "standard")).toBe(true);
+  });
+
+  test("returns true for a fully custom prompt", () => {
+    expect(
+      shouldRecommendDefaultPrompt("You are a custom agent.", "standard"),
+    ).toBe(true);
+  });
+
+  test("returns true for a modified default prompt", () => {
+    const current = buildSystemPrompt("default", "standard");
+    const modified = `${current}\n\nExtra instructions added by user.`;
+    expect(shouldRecommendDefaultPrompt(modified, "standard")).toBe(true);
+  });
+});