Sampling: Make add_bos_token override concise

Also set the default to None so text completions follows the same
pattern.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

common/sampling.py

@@ -205,7 +205,7 @@ class BaseSamplerRequest(BaseModel):
     )
 
     add_bos_token: Optional[bool] = Field(
-        default_factory=lambda: get_default_sampler_value("add_bos_token", True)
+        default_factory=lambda: get_default_sampler_value("add_bos_token")
     )
 
     ban_eos_token: Optional[bool] = Field(

endpoints/OAI/types/chat_completion.py

@@ -84,7 +84,7 @@ class ChatCompletionRequest(CommonCompletionRequest):
 
     # Chat completions requests do not have a BOS token preference. Backend
     # respects the tokenization config for the individual model.
-    add_bos_token: Optional[bool] = Field(default=None)
+    add_bos_token: Optional[bool] = None
 
     @field_validator("add_bos_token", mode="after")
     def force_bos_token(cls, v):

sampler_overrides/sample_preset.yml

@@ -131,7 +131,7 @@ mirostat_eta:
 
 # MARK: Token options
 add_bos_token:
-  override: true
+  override:
   force: false
 ban_eos_token:
   override: false