fix: classify landed file mutations with diagnostics

agent/display.py

@@ -14,6 +14,7 @@ from difflib import unified_diff
 from pathlib import Path
 
 from utils import safe_json_loads
+from agent.tool_result_classification import file_mutation_result_landed
 
 # ANSI escape codes for coloring tool failure indicators
 _RED = "\033[31m"
@@ -810,6 +811,8 @@ def _detect_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str]
     """
     if result is None:
         return False, ""
+    if file_mutation_result_landed(tool_name, result):
+        return False, ""
 
     if tool_name == "terminal":
         data = safe_json_loads(result)

agent/tool_guardrails.py

@@ -14,6 +14,7 @@ from dataclasses import dataclass, field
 from typing import Any, Mapping
 
 from utils import safe_json_loads
+from agent.tool_result_classification import file_mutation_result_landed
 
 
 IDEMPOTENT_TOOL_NAMES = frozenset(
@@ -196,6 +197,8 @@ def classify_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str
     """
     if result is None:
         return False, ""
+    if file_mutation_result_landed(tool_name, result):
+        return False, ""
 
     if tool_name == "terminal":
         data = safe_json_loads(result)

agent/tool_result_classification.py

@@ -0,0 +1,26 @@
+"""Shared helpers for classifying tool result payloads."""
+
+from __future__ import annotations
+
+import json
+from typing import Any
+
+
+FILE_MUTATING_TOOL_NAMES = frozenset({"write_file", "patch"})
+
+
+def file_mutation_result_landed(tool_name: str, result: Any) -> bool:
+    """Return True when a file mutation result proves the write landed."""
+    if tool_name not in FILE_MUTATING_TOOL_NAMES or not isinstance(result, str):
+        return False
+    try:
+        data = json.loads(result.strip())
+    except Exception:
+        return False
+    if not isinstance(data, dict) or data.get("error"):
+        return False
+    if tool_name == "write_file":
+        return "bytes_written" in data
+    if tool_name == "patch":
+        return data.get("success") is True
+    return False