diff --git a/aider/coders/base_coder.py b/aider/coders/base_coder.py
index 7040a4b19..49a9c61c7 100755
--- a/aider/coders/base_coder.py
+++ b/aider/coders/base_coder.py
@@ -989,7 +989,7 @@ class Coder:
                     return
                 except FinishReasonLength:
                     # We hit the output limit!
-                    if not self.main_model.can_prefill:
+                    if not self.main_model.info.get("supports_assistant_prefill"):
                         exhausted = True
                         break
 
@@ -998,7 +998,9 @@ class Coder:
                     if messages[-1]["role"] == "assistant":
                         messages[-1]["content"] = self.multi_response_content
                     else:
-                        messages.append(dict(role="assistant", content=self.multi_response_content))
+                        messages.append(
+                            dict(role="assistant", content=self.multi_response_content, prefix=True)
+                        )
                 except Exception as err:
                     self.io.tool_error(f"Unexpected error: {err}")
                     traceback.print_exc()
diff --git a/aider/main.py b/aider/main.py
index 72308f7a1..911f09ed7 100644
--- a/aider/main.py
+++ b/aider/main.py
@@ -462,7 +462,7 @@ def main(argv=None, input=None, output=None, force_git_root=None, return_coder=F
             args.model = "claude-3-5-sonnet-20240620"
 
     if args.deepseek_beta:
-        args.model = "deepseek-coder"
+        args.model = "deepseek/deepseek-coder"
         os.environ["DEEPSEEK_API_BASE"] = "https://api.deepseek.com/beta"
 
     main_model = models.Model(args.model, weak_model=args.weak_model)
diff --git a/aider/models.py b/aider/models.py
index 908404343..551d0b9a4 100644
--- a/aider/models.py
+++ b/aider/models.py
@@ -70,7 +70,6 @@ class ModelSettings:
     lazy: bool = False
     reminder_as_sys_msg: bool = False
     examples_as_sys_msg: bool = False
-    can_prefill: bool = False
     extra_headers: Optional[dict] = None
     max_tokens: Optional[int] = None
 
@@ -248,7 +247,6 @@ MODEL_SETTINGS = [
         weak_model_name="claude-3-haiku-20240307",
         use_repo_map=True,
         send_undo_reply=True,
-        can_prefill=True,
     ),
     ModelSettings(
         "openrouter/anthropic/claude-3-opus",
@@ -256,13 +254,11 @@ MODEL_SETTINGS = [
         weak_model_name="openrouter/anthropic/claude-3-haiku",
         use_repo_map=True,
         send_undo_reply=True,
-        can_prefill=True,
     ),
     ModelSettings(
         "claude-3-sonnet-20240229",
         "whole",
         weak_model_name="claude-3-haiku-20240307",
-        can_prefill=True,
     ),
     ModelSettings(
         "claude-3-5-sonnet-20240620",
@@ -270,7 +266,6 @@ MODEL_SETTINGS = [
         weak_model_name="claude-3-haiku-20240307",
         use_repo_map=True,
         examples_as_sys_msg=True,
-        can_prefill=True,
         accepts_images=True,
         max_tokens=8192,
         extra_headers={"anthropic-beta": "max-tokens-3-5-sonnet-2024-07-15"},
@@ -281,7 +276,6 @@ MODEL_SETTINGS = [
         weak_model_name="claude-3-haiku-20240307",
         use_repo_map=True,
         examples_as_sys_msg=True,
-        can_prefill=True,
         max_tokens=8192,
         extra_headers={
             "anthropic-beta": "max-tokens-3-5-sonnet-2024-07-15",
@@ -295,7 +289,6 @@ MODEL_SETTINGS = [
         weak_model_name="openrouter/anthropic/claude-3-haiku-20240307",
         use_repo_map=True,
         examples_as_sys_msg=True,
-        can_prefill=True,
         accepts_images=True,
         max_tokens=8192,
         extra_headers={
@@ -312,7 +305,6 @@ MODEL_SETTINGS = [
         weak_model_name="vertex_ai/claude-3-haiku@20240307",
         use_repo_map=True,
         examples_as_sys_msg=True,
-        can_prefill=True,
         accepts_images=True,
     ),
     ModelSettings(
@@ -321,13 +313,11 @@ MODEL_SETTINGS = [
         weak_model_name="vertex_ai/claude-3-haiku@20240307",
         use_repo_map=True,
         send_undo_reply=True,
-        can_prefill=True,
     ),
     ModelSettings(
         "vertex_ai/claude-3-sonnet@20240229",
         "whole",
         weak_model_name="vertex_ai/claude-3-haiku@20240307",
-        can_prefill=True,
     ),
     # Cohere
     ModelSettings(
@@ -486,14 +476,10 @@ class Model:
         if "gpt-3.5" in model or "gpt-4" in model:
             self.reminder_as_sys_msg = True
 
-        if "anthropic" in model:
-            self.can_prefill = True
-
         if "3.5-sonnet" in model or "3-5-sonnet" in model:
             self.edit_format = "diff"
             self.use_repo_map = True
             self.examples_as_sys_msg = True
-            self.can_prefill = True
 
         # use the defaults
         if self.edit_format == "diff":