fix: replace removed MessageContent import with ContentBlock from langchain_core

apps/agent/agent/middleware/open_pr.py

@@ -32,6 +32,7 @@ from ..utils.github import (
     git_push,
 )
 from ..utils.linear import comment_on_linear_issue
+from ..utils.messages import extract_text_content
 from ..utils.sandbox_state import get_sandbox_backend
 
 logger = logging.getLogger(__name__)
@@ -78,9 +79,9 @@ async def open_pr_if_needed(
         if messages:
             last_message = messages[-1]
             if isinstance(last_message, dict):
-                last_message_content = last_message.get("content", "")
+                last_message_content = extract_text_content(last_message.get("content", ""))
             elif hasattr(last_message, "content"):
-                last_message_content = last_message.content
+                last_message_content = extract_text_content(last_message.content)
 
         linear_issue = configurable.get("linear_issue", {})
         linear_issue_id = linear_issue.get("id")

apps/agent/agent/middleware/post_to_linear.py

@@ -14,6 +14,7 @@ from langgraph.config import get_config
 from langgraph.runtime import Runtime
 
 from ..utils.linear import comment_on_linear_issue
+from ..utils.messages import extract_text_content
 from .check_message_queue import LinearNotifyState
 
 logger = logging.getLogger(__name__)
@@ -96,12 +97,13 @@ async def post_to_linear_after_model(  # noqa: PLR0911, PLR0912
             if prev_role not in ("human", "user"):
                 return None
 
-        if not content or not isinstance(content, str):
+        content_text = extract_text_content(content)
+        if not content_text:
             return None
 
         comment = f"""🤖 **Agent Response**
 
-{content}"""
+{content_text}"""
         logger.info("Posting AI response to Linear issue %s", linear_issue_id)
         success = await comment_on_linear_issue(linear_issue_id, comment)
 

apps/agent/agent/utils/messages.py

@@ -0,0 +1,28 @@
+"""Helpers for normalizing message content across model providers."""
+
+from __future__ import annotations
+
+from langchain_core.messages import ContentBlock
+
+
+def extract_text_content(content: str | list[ContentBlock]) -> str:
+    """Extract human-readable text from model message content.
+
+    Supports:
+    - Plain strings
+    - OpenAI-style content blocks (list of {"type": "text", "text": ...})
+    - Dict wrappers with nested "content" or "text"
+    """
+
+    if isinstance(content, str):
+        return content.strip()
+
+    if not isinstance(content, list):
+        return ""
+
+    text = ""
+    for item in content:
+        if isinstance(item, dict) and "text" in item:
+            text += item["text"]
+
+    return text.strip()