diff --git a/agent/prompt_builder.py b/agent/prompt_builder.py
index 2a21043494..8e061f831b 100644
--- a/agent/prompt_builder.py
+++ b/agent/prompt_builder.py
@@ -350,7 +350,13 @@ PLATFORM_HINTS = {
     ),
     "cli": (
         "You are a CLI AI Agent. Try not to use markdown but simple text "
-        "renderable inside a terminal."
+        "renderable inside a terminal. "
+        "File delivery: there is no attachment channel — the user reads your "
+        "response directly in their terminal. Do NOT emit MEDIA:/path tags "
+        "(those are only intercepted on messaging platforms like Telegram, "
+        "Discord, Slack, etc.; on the CLI they render as literal text). "
+        "When referring to a file you created or changed, just state its "
+        "absolute path in plain text; the user can open it from there."
     ),
     "sms": (
         "You are communicating via SMS. Keep responses concise and use plain text "
diff --git a/tests/agent/test_prompt_builder.py b/tests/agent/test_prompt_builder.py
index 0962060313..11712b9519 100644
--- a/tests/agent/test_prompt_builder.py
+++ b/tests/agent/test_prompt_builder.py
@@ -789,6 +789,24 @@ class TestPromptBuilderConstants:
         assert "cron" in PLATFORM_HINTS
         assert "cli" in PLATFORM_HINTS
 
+    def test_cli_hint_does_not_suggest_media_tags(self):
+        # Regression: MEDIA:/path tags are intercepted only by messaging
+        # gateway platforms. On the CLI they render as literal text and
+        # confuse users. The CLI hint must steer the agent away from them.
+        cli_hint = PLATFORM_HINTS["cli"]
+        assert "MEDIA:" in cli_hint, (
+            "CLI hint should mention MEDIA: in order to tell the agent "
+            "NOT to use it (negative guidance)."
+        )
+        # Must contain explicit "don't" language near the MEDIA reference.
+        assert any(
+            marker in cli_hint.lower()
+            for marker in ("do not emit media", "not intercepted", "do not", "don't")
+        ), "CLI hint should explicitly discourage MEDIA: tags."
+        # Messaging hints should still advertise MEDIA: positively (sanity
+        # check that this test is calibrated correctly).
+        assert "include MEDIA:" in PLATFORM_HINTS["telegram"]
+
 
 # =========================================================================
 # Environment hints