Fix BadRequestError due to unvalid max_tokens

This patch ensures if max tokens is not defined it is set to None.
This avoid some providers to fail, as they don't have protection for
it being set to 0

Issue: #3666

Author: luis5tb

docs/static/deprecated-llama-stack-spec.html

@@ -4218,7 +4218,6 @@
                     },
                     "max_tokens": {
                         "type": "integer",
-                        "default": 0,
                         "description": "The maximum number of tokens that can be generated in the completion. The token count of your prompt plus max_tokens cannot exceed the model's context length."
                     },
                     "repetition_penalty": {

docs/static/deprecated-llama-stack-spec.yaml

@@ -3068,7 +3068,6 @@ components:
           description: The sampling strategy.
         max_tokens:
           type: integer
-          default: 0
           description: >-
             The maximum number of tokens that can be generated in the completion.
             The token count of your prompt plus max_tokens cannot exceed the model's

docs/static/experimental-llama-stack-spec.html

@@ -2713,7 +2713,6 @@
                     },
                     "max_tokens": {
                         "type": "integer",
-                        "default": 0,
                         "description": "The maximum number of tokens that can be generated in the completion. The token count of your prompt plus max_tokens cannot exceed the model's context length."
                     },
                     "repetition_penalty": {

docs/static/experimental-llama-stack-spec.yaml

@@ -1927,7 +1927,6 @@ components:
           description: The sampling strategy.
         max_tokens:
           type: integer
-          default: 0
           description: >-
             The maximum number of tokens that can be generated in the completion.
             The token count of your prompt plus max_tokens cannot exceed the model's

docs/static/stainless-llama-stack-spec.html

@@ -14753,7 +14753,6 @@
                     },
                     "max_tokens": {
                         "type": "integer",
-                        "default": 0,
                         "description": "The maximum number of tokens that can be generated in the completion. The token count of your prompt plus max_tokens cannot exceed the model's context length."
                     },
                     "repetition_penalty": {

docs/static/stainless-llama-stack-spec.yaml

@@ -10909,7 +10909,6 @@ components:
           description: The sampling strategy.
         max_tokens:
           type: integer
-          default: 0
           description: >-
             The maximum number of tokens that can be generated in the completion.
             The token count of your prompt plus max_tokens cannot exceed the model's

llama_stack/apis/inference/inference.py

@@ -96,7 +96,7 @@ class SamplingParams(BaseModel):
 
     strategy: SamplingStrategy = Field(default_factory=GreedySamplingStrategy)
 
-    max_tokens: int | None = 0
+    max_tokens: int | None = None
     repetition_penalty: float | None = 1.0
     stop: list[str] | None = None
 

tests/integration/eval/test_eval.py

@@ -55,6 +55,7 @@ def test_evaluate_rows(llama_stack_client, text_model_id, scoring_fn_id):
                 "model": text_model_id,
                 "sampling_params": {
                     "temperature": 0.0,
+                    "max_tokens": 512,
                 },
             },
         },
@@ -88,6 +89,7 @@ def test_evaluate_benchmark(llama_stack_client, text_model_id, scoring_fn_id):
                 "model": text_model_id,
                 "sampling_params": {
                     "temperature": 0.0,
+                    "max_tokens": 128,
                 },
             },
         },