fix: GitHub raw dict helper + PostableObject history cache

- Extract _build_raw_message() in GitHub adapter (was duplicated between
  post_message and edit_message)
- PostableObject posts now cached in message history for both Thread and
  Channel, so Plan objects appear in messages()/all_messages() like
  regular posts. Uses fallback text as the cached message content.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: patrick-chinchill

src/chat_sdk/adapters/github/adapter.py

@@ -476,24 +476,10 @@ async def post_message(self, thread_id: str, message: AdapterPostableMessage) ->
                 {"body": body},
             )
 
-        raw: dict[str, Any] = {
-            "type": "review_comment" if decoded.review_comment_id else "issue_comment",
-            "comment": comment,
-            "repository": {
-                "id": 0,
-                "name": decoded.repo,
-                "full_name": f"{decoded.owner}/{decoded.repo}",
-                "owner": {"id": 0, "login": decoded.owner, "type": "User"},
-            },
-            "pr_number": decoded.pr_number,
-        }
-        if not decoded.review_comment_id:
-            raw["thread_type"] = decoded.type or "pr"
-
         return RawMessage(
             id=str(comment["id"]),
             thread_id=thread_id,
-            raw=raw,
+            raw=self._build_raw_message(decoded, comment),
         )
 
     async def edit_message(self, thread_id: str, message_id: str, message: AdapterPostableMessage) -> RawMessage:
@@ -518,24 +504,10 @@ async def edit_message(self, thread_id: str, message_id: str, message: AdapterPo
                 {"body": body},
             )
 
-        raw: dict[str, Any] = {
-            "type": "review_comment" if decoded.review_comment_id else "issue_comment",
-            "comment": comment,
-            "repository": {
-                "id": 0,
-                "name": decoded.repo,
-                "full_name": f"{decoded.owner}/{decoded.repo}",
-                "owner": {"id": 0, "login": decoded.owner, "type": "User"},
-            },
-            "pr_number": decoded.pr_number,
-        }
-        if not decoded.review_comment_id:
-            raw["thread_type"] = decoded.type or "pr"
-
         return RawMessage(
             id=str(comment["id"]),
             thread_id=thread_id,
-            raw=raw,
+            raw=self._build_raw_message(decoded, comment),
         )
 
     async def stream(
@@ -553,6 +525,24 @@ async def stream(
                 text += chunk.text
         return await self.post_message(thread_id, {"markdown": text})
 
+    @staticmethod
+    def _build_raw_message(decoded: Any, comment: dict[str, Any]) -> dict[str, Any]:
+        """Build the raw message dict for post/edit responses."""
+        raw: dict[str, Any] = {
+            "type": "review_comment" if decoded.review_comment_id else "issue_comment",
+            "comment": comment,
+            "repository": {
+                "id": 0,
+                "name": decoded.repo,
+                "full_name": f"{decoded.owner}/{decoded.repo}",
+                "owner": {"id": 0, "login": decoded.owner, "type": "User"},
+            },
+            "pr_number": decoded.pr_number,
+        }
+        if not decoded.review_comment_id:
+            raw["thread_type"] = decoded.type or "pr"
+        return raw
+
     async def delete_message(self, thread_id: str, message_id: str) -> None:
         """Delete a message."""
         decoded = self.decode_thread_id(thread_id)

src/chat_sdk/channel.py

@@ -284,6 +284,13 @@ async def post(
         """
         if is_postable_object(message):
             await self._handle_postable_object(message)
+            # Cache fallback text in history so the plan appears in channel.messages()
+            if self._message_history is not None:
+                fallback_text = message.get_fallback_text() if hasattr(message, "get_fallback_text") else ""
+                fallback_msg = _to_message(
+                    self._create_sent_message("postable-obj", PostableMarkdown(markdown=fallback_text))
+                )
+                await self._message_history.append(self._id, fallback_msg)
             return message
 
         if _is_async_iterable(message):

src/chat_sdk/thread.py

@@ -443,6 +443,14 @@ async def post(
         # Handle PostableObject (e.g. Plan)
         if is_postable_object(message):
             await self._handle_postable_object(message)
+            # Cache the fallback text in message history so the plan appears
+            # in thread.messages() / all_messages() like regular posts.
+            if self._message_history is not None:
+                fallback_text = message.get_fallback_text() if hasattr(message, "get_fallback_text") else ""
+                fallback_msg = _to_message(
+                    self._create_sent_message("postable-obj", PostableMarkdown(markdown=fallback_text), self._id)
+                )
+                await self._message_history.append(self._id, fallback_msg)
             return message
 
         # Handle AsyncIterable (streaming)