feat: pre-call sanitization and post-call tool guardrails (#1732)

Salvage of PR #1321 by @alireza78a (cherry-picked concept, reimplemented
against current main).

Phase 1 — Pre-call message sanitization:
  _sanitize_api_messages() now runs unconditionally before every LLM call.
  Previously gated on context_compressor being present, so sessions loaded
  from disk or running without compression could accumulate dangling
  tool_call/tool_result pairs causing API errors.

Phase 2a — Delegate task cap:
  _cap_delegate_task_calls() truncates excess delegate_task calls per turn
  to MAX_CONCURRENT_CHILDREN. The existing cap in delegate_tool.py only
  limits the task array within a single call; this catches multiple
  separate delegate_task tool_calls in one turn.

Phase 2b — Tool call deduplication:
  _deduplicate_tool_calls() drops duplicate (tool_name, arguments) pairs
  within a single turn when models stutter.

All three are static methods on AIAgent, independently testable.
29 tests covering happy paths and edge cases.

run_agent.py

@@ -1957,7 +1957,124 @@ class AIAgent:
             prompt_parts.append(PLATFORM_HINTS[platform_key])
 
         return "\n\n".join(prompt_parts)
-    
+
+    # =========================================================================
+    # Pre/post-call guardrails (inspired by PR #1321 — @alireza78a)
+    # =========================================================================
+
+    @staticmethod
+    def _get_tool_call_id_static(tc) -> str:
+        """Extract call ID from a tool_call entry (dict or object)."""
+        if isinstance(tc, dict):
+            return tc.get("id", "") or ""
+        return getattr(tc, "id", "") or ""
+
+    @staticmethod
+    def _sanitize_api_messages(messages: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
+        """Fix orphaned tool_call / tool_result pairs before every LLM call.
+
+        Runs unconditionally — not gated on whether the context compressor
+        is present — so orphans from session loading or manual message
+        manipulation are always caught.
+        """
+        surviving_call_ids: set = set()
+        for msg in messages:
+            if msg.get("role") == "assistant":
+                for tc in msg.get("tool_calls") or []:
+                    cid = AIAgent._get_tool_call_id_static(tc)
+                    if cid:
+                        surviving_call_ids.add(cid)
+
+        result_call_ids: set = set()
+        for msg in messages:
+            if msg.get("role") == "tool":
+                cid = msg.get("tool_call_id")
+                if cid:
+                    result_call_ids.add(cid)
+
+        # 1. Drop tool results with no matching assistant call
+        orphaned_results = result_call_ids - surviving_call_ids
+        if orphaned_results:
+            messages = [
+                m for m in messages
+                if not (m.get("role") == "tool" and m.get("tool_call_id") in orphaned_results)
+            ]
+            logger.debug(
+                "Pre-call sanitizer: removed %d orphaned tool result(s)",
+                len(orphaned_results),
+            )
+
+        # 2. Inject stub results for calls whose result was dropped
+        missing_results = surviving_call_ids - result_call_ids
+        if missing_results:
+            patched: List[Dict[str, Any]] = []
+            for msg in messages:
+                patched.append(msg)
+                if msg.get("role") == "assistant":
+                    for tc in msg.get("tool_calls") or []:
+                        cid = AIAgent._get_tool_call_id_static(tc)
+                        if cid in missing_results:
+                            patched.append({
+                                "role": "tool",
+                                "content": "[Result unavailable — see context summary above]",
+                                "tool_call_id": cid,
+                            })
+            messages = patched
+            logger.debug(
+                "Pre-call sanitizer: added %d stub tool result(s)",
+                len(missing_results),
+            )
+
+        return messages
+
+    @staticmethod
+    def _cap_delegate_task_calls(tool_calls: list) -> list:
+        """Truncate excess delegate_task calls to MAX_CONCURRENT_CHILDREN.
+
+        The delegate_tool caps the task list inside a single call, but the
+        model can emit multiple separate delegate_task tool_calls in one
+        turn.  This truncates the excess, preserving all non-delegate calls.
+
+        Returns the original list if no truncation was needed.
+        """
+        from tools.delegate_tool import MAX_CONCURRENT_CHILDREN
+        delegate_count = sum(1 for tc in tool_calls if tc.function.name == "delegate_task")
+        if delegate_count <= MAX_CONCURRENT_CHILDREN:
+            return tool_calls
+        kept_delegates = 0
+        truncated = []
+        for tc in tool_calls:
+            if tc.function.name == "delegate_task":
+                if kept_delegates < MAX_CONCURRENT_CHILDREN:
+                    truncated.append(tc)
+                    kept_delegates += 1
+            else:
+                truncated.append(tc)
+        logger.warning(
+            "Truncated %d excess delegate_task call(s) to enforce "
+            "MAX_CONCURRENT_CHILDREN=%d limit",
+            delegate_count - MAX_CONCURRENT_CHILDREN, MAX_CONCURRENT_CHILDREN,
+        )
+        return truncated
+
+    @staticmethod
+    def _deduplicate_tool_calls(tool_calls: list) -> list:
+        """Remove duplicate (tool_name, arguments) pairs within a single turn.
+
+        Only the first occurrence of each unique pair is kept.
+        Returns the original list if no duplicates were found.
+        """
+        seen: set = set()
+        unique: list = []
+        for tc in tool_calls:
+            key = (tc.function.name, tc.function.arguments)
+            if key not in seen:
+                seen.add(key)
+                unique.append(tc)
+            else:
+                logger.warning("Removed duplicate tool call: %s", tc.function.name)
+        return unique if len(unique) < len(tool_calls) else tool_calls
+
     def _repair_tool_call(self, tool_name: str) -> str | None:
         """Attempt to repair a mismatched tool name before aborting.
 
@@ -4992,11 +5109,10 @@ class AIAgent:
                 api_messages = apply_anthropic_cache_control(api_messages, cache_ttl=self._cache_ttl)
 
             # Safety net: strip orphaned tool results / add stubs for missing
-            # results before sending to the API.  The compressor handles this
-            # during compression, but orphans can also sneak in from session
-            # loading or manual message manipulation.
-            if hasattr(self, 'context_compressor') and self.context_compressor:
-                api_messages = self.context_compressor._sanitize_tool_pairs(api_messages)
+            # results before sending to the API.  Runs unconditionally — not
+            # gated on context_compressor — so orphans from session loading or
+            # manual message manipulation are always caught.
+            api_messages = self._sanitize_api_messages(api_messages)
 
             # Calculate approximate request size for logging
             total_chars = sum(len(str(msg)) for msg in api_messages)
@@ -6026,7 +6142,15 @@ class AIAgent:
                     
                     # Reset retry counter on successful JSON validation
                     self._invalid_json_retries = 0
-                    
+
+                    # ── Post-call guardrails ──────────────────────────
+                    assistant_message.tool_calls = self._cap_delegate_task_calls(
+                        assistant_message.tool_calls
+                    )
+                    assistant_message.tool_calls = self._deduplicate_tool_calls(
+                        assistant_message.tool_calls
+                    )
+
                     assistant_msg = self._build_assistant_message(assistant_message, finish_reason)
                     
                     # If this turn has both content AND tool_calls, capture the content