diff --git a/agent/context_compressor.py b/agent/context_compressor.py
index 2baa2731c627..1406aa2197b9 100644
--- a/agent/context_compressor.py
+++ b/agent/context_compressor.py
@@ -891,7 +891,13 @@ def _summarize_tool_result_unguarded(tool_name: str, tool_args: str, tool_conten
             code_preview += "..."
         return f"[execute_code] `{code_preview}` ({line_count} lines output)"
 
-    if tool_name in {"skill_view", "skills_list", "skill_manage"}:
+    if tool_name == "skill_view":
+        name = args.get("name", "?")
+        if content_len > 5000:
+            return f"[skill_view] name={name} ({content_len:,} chars) [SKILL_PRUNED: content lost in compression; reload with skill_view before relying on it]"
+        return f"[skill_view] name={name} ({content_len:,} chars)"
+
+    if tool_name in {"skills_list", "skill_manage"}:
         name = args.get("name", "?")
         return f"[{tool_name}] name={name} ({content_len:,} chars)"
 
diff --git a/agent/prompt_builder.py b/agent/prompt_builder.py
index fc94ca2a6b22..a7340f17279a 100644
--- a/agent/prompt_builder.py
+++ b/agent/prompt_builder.py
@@ -192,7 +192,12 @@ SKILLS_GUIDANCE = (
     "skill with skill_manage so you can reuse it next time.\n"
     "When using a skill and finding it outdated, incomplete, or wrong, "
     "patch it immediately with skill_manage(action='patch') — don't wait to be asked. "
-    "Skills that aren't maintained become liabilities."
+    "Skills that aren't maintained become liabilities.\n"
+    "\n"
+    "## Skill Safety Rule\n"
+    "1. **UNAVAILABLE** — If a skill placeholder contains `[SKILL_PRUNED]`, the skill content was lost in compression and is inaccessible.\n"
+    "2. **RELOAD** — Before performing any action that depends on a skill, re-check its content with `skill_view(name='...')` if it shows `[SKILL_PRUNED]`.\n"
+    "3. **WAIT** — If a skill is loading or was just pruned, wait for the reload confirmation before proceeding."
 )
 
 KANBAN_GUIDANCE = (