diff --git a/packages/jupyter-ai/jupyter_ai/chat_handlers/base.py b/packages/jupyter-ai/jupyter_ai/chat_handlers/base.py
index 107b5a000..c844650ad 100644
--- a/packages/jupyter-ai/jupyter_ai/chat_handlers/base.py
+++ b/packages/jupyter-ai/jupyter_ai/chat_handlers/base.py
@@ -521,6 +521,7 @@ async def stream_reply(
         self,
         input: Input,
         human_msg: HumanChatMessage,
+        pending_msg="Generating response",
         config: Optional[RunnableConfig] = None,
     ):
         """
@@ -538,6 +539,9 @@ async def stream_reply(
 
         - `config` (optional): A `RunnableConfig` object that specifies
         additional configuration when streaming from the runnable.
+
+         - `pending_msg` (optional): Changes the default pending message from
+        "Generating response".
         """
         assert self.llm_chain
         assert isinstance(self.llm_chain, Runnable)
@@ -551,7 +555,7 @@ async def stream_reply(
         merged_config: RunnableConfig = merge_runnable_configs(base_config, config)
 
         # start with a pending message
-        with self.pending("Generating response", human_msg) as pending_message:
+        with self.pending(pending_msg, human_msg) as pending_message:
             # stream response in chunks. this works even if a provider does not
             # implement streaming, as `astream()` defaults to yielding `_call()`
             # when `_stream()` is not implemented on the LLM class.
diff --git a/packages/jupyter-ai/jupyter_ai/chat_handlers/fix.py b/packages/jupyter-ai/jupyter_ai/chat_handlers/fix.py
index 4daf70e03..390b93cf6 100644
--- a/packages/jupyter-ai/jupyter_ai/chat_handlers/fix.py
+++ b/packages/jupyter-ai/jupyter_ai/chat_handlers/fix.py
@@ -2,7 +2,6 @@
 
 from jupyter_ai.models import CellWithErrorSelection, HumanChatMessage
 from jupyter_ai_magics.providers import BaseProvider
-from langchain.chains import LLMChain
 from langchain.prompts import PromptTemplate
 
 from .base import BaseChatHandler, SlashCommandRoutingType
@@ -64,6 +63,7 @@ class FixChatHandler(BaseChatHandler):
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
+        self.prompt_template = None
 
     def create_llm_chain(
         self, provider: Type[BaseProvider], provider_params: Dict[str, str]
@@ -73,13 +73,11 @@ def create_llm_chain(
             **(self.get_model_parameters(provider, provider_params)),
         }
         llm = provider(**unified_parameters)
-
         self.llm = llm
-        # TODO: migrate this class to use a LCEL `Runnable` instead of
-        # `Chain`, then remove the below ignore comment.
-        self.llm_chain = LLMChain(  # type:ignore[arg-type]
-            llm=llm, prompt=FIX_PROMPT_TEMPLATE, verbose=True
-        )
+        prompt_template = FIX_PROMPT_TEMPLATE
+
+        runnable = prompt_template | llm  # type:ignore
+        self.llm_chain = runnable
 
     async def process_message(self, message: HumanChatMessage):
         if not (message.selection and message.selection.type == "cell-with-error"):
@@ -96,16 +94,13 @@ async def process_message(self, message: HumanChatMessage):
         extra_instructions = message.prompt[4:].strip() or "None."
 
         self.get_llm_chain()
-        with self.pending("Analyzing error", message):
-            assert self.llm_chain
-            # TODO: migrate this class to use a LCEL `Runnable` instead of
-            # `Chain`, then remove the below ignore comment.
-            response = await self.llm_chain.apredict(  # type:ignore[attr-defined]
-                extra_instructions=extra_instructions,
-                stop=["\nHuman:"],
-                cell_content=selection.source,
-                error_name=selection.error.name,
-                error_value=selection.error.value,
-                traceback="\n".join(selection.error.traceback),
-            )
-        self.reply(response, message)
+        assert self.llm_chain
+
+        inputs = {
+            "extra_instructions": extra_instructions,
+            "cell_content": selection.source,
+            "traceback": "\n".join(selection.error.traceback),
+            "error_name": selection.error.name,
+            "error_value": selection.error.value,
+        }
+        await self.stream_reply(inputs, message, pending_msg="Analyzing error")