Fix compacted tool history for resumed sessions

src/agent_runtime.py

@@ -37,7 +37,7 @@ from .agent_prompting import (
     build_system_prompt_parts,
     render_system_prompt,
 )
-from .agent_session import AgentSessionState
+from .agent_session import AgentSessionState, sanitize_model_message_sequence
 from .agent_slash_commands import preprocess_slash_command
 from .agent_tools import (
     AgentTool,
@@ -2468,7 +2468,9 @@ class LocalCodingAgent:
         if compact_end <= prefix_count:
             return False
         candidates = session.messages[prefix_count:compact_end]
-        preserved_tail = list(session.messages[compact_end:])
+        preserved_tail = sanitize_model_message_sequence(
+            list(session.messages[compact_end:])
+        )
         if not candidates:
             return False
         compacted_tokens = sum(
@@ -2492,13 +2494,13 @@ class LocalCodingAgent:
             turn_index=turn_index,
             estimated_tokens_before=usage_total,
             estimated_tokens_removed=compacted_tokens,
-            preserved_tail_count=tail_count,
+            preserved_tail_count=len(preserved_tail),
             preserved_tail=preserved_tail,
         )
         session.messages = (
             session.messages[:prefix_count]
             + [compact_message]
-            + session.messages[compact_end:]
+            + preserved_tail
         )
         stream_events.append(
             {
@@ -2507,7 +2509,7 @@ class LocalCodingAgent:
                 'compacted_message_count': len(candidates),
                 'estimated_tokens_before': usage_total,
                 'estimated_tokens_removed': compacted_tokens,
-                'preserved_tail_count': tail_count,
+                'preserved_tail_count': len(preserved_tail),
                 'preserved_tail_ids': [
                     message.message_id for message in preserved_tail if message.message_id
                 ],