fix: make invalid source retries actionable

agent_platform/runtime/loop.py

@@ -409,7 +409,15 @@ def python_source_error(arguments: dict[str, Any]) -> str | None:
         ast.parse(content, filename=path)
     except SyntaxError as exc:
         location = f"line {exc.lineno}" if exc.lineno else "unknown line"
-        return f"{exc.msg} ({location})"
+        source_lines = content.splitlines()
+        snippet = ""
+        if exc.lineno:
+            first = max(1, exc.lineno - 1)
+            last = min(len(source_lines), exc.lineno + 1)
+            snippet = "\n" + "\n".join(
+                f"{line_number}: {source_lines[line_number - 1][:240]}" for line_number in range(first, last + 1)
+            )
+        return f"{exc.msg} ({location}). Source around the error:{snippet}"
     return None
 
 
@@ -580,6 +588,7 @@ class AgentLoop:
         unresolved_execution_failure: str | None = None
         failed_execution_revisions: dict[str, int] = {}
         successful_write_fingerprints: set[str] = set()
+        failed_write_fingerprints: set[str] = set()
         consecutive_checkpoint_rejections = 0
         for iteration in range(max_iterations):
             await recorder.emit(
@@ -697,6 +706,9 @@ class AgentLoop:
                 ):
                     blocked_call_reasons[call_id] = "duplicate_write"
                     continue
+                if fingerprint in failed_write_fingerprints:
+                    blocked_call_reasons[call_id] = "failed_write_retry"
+                    continue
                 if fingerprint:
                     batch_write_fingerprints.add(fingerprint)
                 key = execution_call_key(name, arguments) if isinstance(arguments, dict) else None
@@ -760,6 +772,10 @@ class AgentLoop:
                     key = execution_call_key(name, arguments) if isinstance(arguments, dict) else None
                     if key:
                         failed_execution_revisions[key] = mutation_count
+                if not result.get("ok", False):
+                    fingerprint = write_call_fingerprint(name, arguments) if isinstance(arguments, dict) else None
+                    if fingerprint and not result.get("policy_duplicate", False):
+                        failed_write_fingerprints.add(fingerprint)
                 messages.append(
                     {
                         "role": "tool",
@@ -913,6 +929,15 @@ class AgentLoop:
                     "already requested it without an intervening repair."
                 ),
             }
+        elif blocked_reason == "failed_write_retry":
+            result = {
+                "ok": False,
+                "policy_duplicate": True,
+                "error": (
+                    "Execution policy skipped this unchanged write because identical content already failed "
+                    "validation in this run. Inspect the prior validation error and make a real source change."
+                ),
+            }
         elif blocked_reason == "failed_retry":
             result = {
                 "ok": False,