fix(guardrails): preserve display _detect_tool_failure semantics

The initial guardrail PR consolidated failure classification by pointing
display._detect_tool_failure at the new classify_tool_failure helper,
which was strictly broader: it flagged any JSON result with
"success": false / "failed": true / non-empty "error", plus plain-text
"traceback" and "error:" prefixes. That would uptick the user-visible
[error] tag on tools that return {"success": false} as a benign signal
(memory fullness, todo state, etc.) and feed the failure-streak counter
at the same time.

Restore display._detect_tool_failure to its pre-PR semantics verbatim.
Tighten classify_tool_failure (the guardrail's internal safety-fallback
used only when callers don't pass failed=) to match _detect_tool_failure
exactly, so the two never disagree. Production callers in run_agent.py
already pass an explicit failed= derived from _detect_tool_failure, so
the guardrail counter is driven by the same signal the CLI shows.

agent/display.py

@@ -14,7 +14,6 @@ from difflib import unified_diff
 from pathlib import Path
 
 from utils import safe_json_loads
-from agent.tool_guardrails import classify_tool_failure
 
 # ANSI escape codes for coloring tool failure indicators
 _RED = "\033[31m"
@@ -809,7 +808,30 @@ def _detect_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str]
     like ``" [exit 1]"`` for terminal failures, or ``" [error]"`` for generic
     failures.  On success, returns ``(False, "")``.
     """
-    return classify_tool_failure(tool_name, result)
+    if result is None:
+        return False, ""
+
+    if tool_name == "terminal":
+        data = safe_json_loads(result)
+        if isinstance(data, dict):
+            exit_code = data.get("exit_code")
+            if exit_code is not None and exit_code != 0:
+                return True, f" [exit {exit_code}]"
+        return False, ""
+
+    # Memory-specific: distinguish "full" from real errors
+    if tool_name == "memory":
+        data = safe_json_loads(result)
+        if isinstance(data, dict):
+            if data.get("success") is False and "exceed the limit" in data.get("error", ""):
+                return True, " [full]"
+
+    # Generic heuristic for non-terminal tools
+    lower = result[:500].lower()
+    if '"error"' in lower or '"failed"' in lower or result.startswith("Error"):
+        return True, " [error]"
+
+    return False, ""
 
 
 def get_cute_tool_message(

agent/tool_guardrails.py

@@ -186,7 +186,14 @@ def canonical_tool_args(args: Mapping[str, Any]) -> str:
 
 
 def classify_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str]:
-    """Classify a tool result using shared display/runtime semantics."""
+    """Safety-fallback classifier used only when callers don't pass ``failed``.
+
+    Mirrors ``agent.display._detect_tool_failure`` exactly so the guardrail
+    never disagrees with the CLI's user-visible ``[error]`` tag. Production
+    callers in ``run_agent.py`` always pass an explicit ``failed=`` derived
+    from ``_detect_tool_failure``; this function exists so standalone callers
+    (tests, tooling) still get consistent behavior.
+    """
     if result is None:
         return False, ""
 
@@ -196,31 +203,18 @@ def classify_tool_failure(tool_name: str, result: str | None) -> tuple[bool, str
             exit_code = data.get("exit_code")
             if exit_code is not None and exit_code != 0:
                 return True, f" [exit {exit_code}]"
-            if data.get("success") is False or data.get("failed") is True:
-                return True, " [error]"
-            error = data.get("error")
-            if error is not None and error != "":
-                return True, " [error]"
         return False, ""
 
+    if tool_name == "memory":
         data = safe_json_loads(result)
         if isinstance(data, dict):
-        if tool_name == "memory":
-            error = data.get("error", "")
-            if data.get("success") is False and isinstance(error, str) and "exceed the limit" in error:
+            if data.get("success") is False and "exceed the limit" in data.get("error", ""):
                 return True, " [full]"
-        if data.get("success") is False or data.get("failed") is True:
-            return True, " [error]"
-        error = data.get("error")
-        if error is not None and error != "":
-            return True, " [error]"
-        return False, ""
 
     lower = result[:500].lower()
-    if "traceback" in lower or lower.startswith("error:"):
-        return True, " [error]"
     if '"error"' in lower or '"failed"' in lower or result.startswith("Error"):
         return True, " [error]"
+
     return False, ""