[Feature]: add presence_penalty and frequency_penalty fields to Responses API (#38613)

Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

vllm/entrypoints/openai/responses/protocol.py

@@ -173,6 +173,24 @@ class ResponsesRequest(OpenAIBaseModel):
     user: str | None = None
     skip_special_tokens: bool = True
     include_stop_str_in_output: bool = False
+    presence_penalty: float | None = Field(
+        default=None,
+        ge=-2.0,
+        le=2.0,
+        description=(
+            "The presence penalty that was used to penalize new tokens based on "
+            "whether they appear in the text so far."
+        ),
+    )
+    frequency_penalty: float | None = Field(
+        default=None,
+        ge=-2.0,
+        le=2.0,
+        description=(
+            "The frequency penalty that was used to penalize new tokens based on "
+            "their frequency in the text so far."
+        ),
+    )
     prompt_cache_key: str | None = Field(
         default=None,
         description=(
@@ -328,6 +346,12 @@ class ResponsesRequest(OpenAIBaseModel):
         if (repetition_penalty := self.repetition_penalty) is None:
             repetition_penalty = default_sampling_params.get("repetition_penalty", 1.0)
 
+        if (presence_penalty := self.presence_penalty) is None:
+            presence_penalty = default_sampling_params.get("presence_penalty", 0.0)
+
+        if (frequency_penalty := self.frequency_penalty) is None:
+            frequency_penalty = default_sampling_params.get("frequency_penalty", 0.0)
+
         stop_token_ids = default_sampling_params.get("stop_token_ids")
 
         # Structured output
@@ -367,6 +391,8 @@ class ResponsesRequest(OpenAIBaseModel):
             logprobs=self.top_logprobs if self.is_include_output_logprobs() else None,
             stop_token_ids=stop_token_ids,
             stop=stop,
+            frequency_penalty=frequency_penalty,
+            presence_penalty=presence_penalty,
             repetition_penalty=repetition_penalty,
             seed=self.seed,
             ignore_eos=self.ignore_eos,
@@ -496,6 +522,25 @@ class ResponsesResponse(OpenAIBaseModel):
     usage: ResponseUsage | None = None
     user: str | None = None
 
+    presence_penalty: float | None = Field(
+        default=None,
+        ge=-2.0,
+        le=2.0,
+        description=(
+            "The presence penalty that was used to penalize new tokens based on "
+            "whether they appear in the text so far."
+        ),
+    )
+    frequency_penalty: float | None = Field(
+        default=None,
+        ge=-2.0,
+        le=2.0,
+        description=(
+            "The frequency penalty that was used to penalize new tokens based on "
+            "their frequency in the text so far."
+        ),
+    )
+
     # vLLM-specific fields that are not in OpenAI spec
     kv_transfer_params: dict[str, Any] | None = Field(
         default=None, description="KVTransfer parameters."
@@ -574,6 +619,8 @@ class ResponsesResponse(OpenAIBaseModel):
             prompt=request.prompt,
             reasoning=request.reasoning,
             service_tier=request.service_tier,
+            presence_penalty=sampling_params.presence_penalty,
+            frequency_penalty=sampling_params.frequency_penalty,
             status=status,
             text=request.text,
             top_logprobs=sampling_params.logprobs,