> ## Documentation Index > Fetch the complete documentation index at: https://langwatch.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Parameter mapping > How every OpenAI chat-completions parameter behaves on each provider lane, and how to control dropping with drop_tuning_params. The gateway speaks the OpenAI chat-completions wire format to every provider. OpenAI-compatible targets (OpenAI, Azure OpenAI, self-hosted vLLM and other custom OpenAI-compatible endpoints) bypass the policy on this page entirely: the request body is forwarded byte-for-byte apart from the gateway-only `drop_tuning_params` field, which is consumed before forwarding, so whatever the provider accepts, you get. For the translated lanes (Anthropic, Bedrock, Gemini, Vertex) the gateway builds the provider-native request itself, and every parameter follows an explicit policy: * **mapped**: translated faithfully to the provider's native field. * **dropped**: a tuning parameter with no equivalent on the lane. By default it is removed, the request proceeds, and the drop is signaled (see below). It is never silently ignored. * **refused**: the request depends on the parameter functionally; honoring the request without it would change what you observably get. These always fail with a clear `400 unsupported_parameter` error naming the parameter, the lane, and why. ## drop\_tuning\_params Send `"drop_tuning_params": false` in the request body to opt into strict mode: any parameter the lane cannot map then refuses instead of dropping. The default is `true`. The field itself is consumed by the gateway and never reaches a provider. ```json theme={null} { "model": "anthropic/claude-haiku-4-5", "messages": [{"role": "user", "content": "hi"}], "seed": 42, "drop_tuning_params": false } ``` ```json theme={null} { "error": { "type": "unsupported_parameter", "code": "unsupported_parameter", "message": "refusing to drop 'seed' for anthropic/claude-haiku-4-5: drop_tuning_params is false and Anthropic has no sampling seed. Remove it, set drop_tuning_params to true, or use a model that supports it" } } ``` ## Drop signals When a parameter is dropped, the drop is visible in three places: * Response body: `extra_fields.params_dropped` lists the dropped parameter names (on streams, on the final usage-bearing chunk). * Response header: `X-LangWatch-Params-Dropped` carries the same list, comma separated. * Trace: the gateway span records `langwatch.gateway.params_dropped`. ## The table | Parameter | anthropic | bedrock | gemini / vertex | Notes | | ------------------------ | --------- | ------- | --------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `audio` | dropped | dropped | dropped | | | `frequency_penalty` | dropped | dropped | mapped | | | `function_call` | refused | refused | refused | | | `functions` | refused | refused | refused | | | `logit_bias` | dropped | dropped | dropped | | | `logprobs` | refused | refused | mapped | | | `metadata` | dropped | dropped | dropped | | | `modalities` | dropped | dropped | dropped | | | `n` | dropped | dropped | dropped | n: 1 passes; n > 1 is reduced to one completion and signaled | | `parallel_tool_calls` | dropped | dropped | dropped | | | `prediction` | dropped | dropped | dropped | | | `presence_penalty` | dropped | dropped | mapped | | | `prompt_cache_key` | dropped | dropped | dropped | | | `prompt_cache_retention` | dropped | dropped | dropped | | | `reasoning_effort` | mapped | mapped | mapped | bedrock: mapped for Anthropic (thinking) and Nova; refused for other families; a customer VPC endpoint maps Anthropic only | | `response_format` | mapped | mapped | mapped | anthropic: json\_schema enforced; json\_object refused (no parseable-JSON guarantee); bedrock: json\_schema enforced; json\_object refused (no parseable-JSON guarantee); a customer VPC endpoint enforces json\_schema for Anthropic models only; gemini: json\_object and json\_schema both enforced | | `safety_identifier` | dropped | dropped | dropped | | | `seed` | dropped | dropped | dropped | | | `service_tier` | dropped | dropped | dropped | anthropic: "auto" passes natively; other values dropped; bedrock: dropped (AWS validates a different enum); gemini: dropped | | `stop` | mapped | mapped | mapped | | | `store` | dropped | dropped | dropped | | | `stream_options` | mapped | mapped | mapped | | | `temperature` | mapped | mapped | mapped | | | `tool_choice` | mapped | mapped | mapped | anthropic: none/auto/required/named mapped; named must exist in tools; allowed\_tools refused; bedrock: none maps by removing tools (Converse has no none mode); named must exist in tools; allowed\_tools refused; gemini: none/auto/required/named mapped; named must exist in tools; allowed\_tools refused | | `tools` | mapped | mapped | mapped | | | `top_logprobs` | refused | refused | mapped | | | `top_p` | mapped | mapped | mapped | anthropic: dropped with a signal when temperature is also set (Anthropic models reject the pair); bedrock: dropped with a signal when temperature is also set on Anthropic models (they reject the pair); other families take both | | `user` | dropped | dropped | dropped | | | `verbosity` | dropped | dropped | dropped | | | `web_search_options` | dropped | dropped | dropped | | | any other key | dropped | dropped | dropped | vendor params with no mapping on translated lanes | ## reasoning\_effort budgets On lanes that map `reasoning_effort` to a thinking budget (Anthropic models without adaptive thinking, on both the anthropic and bedrock lanes), the budget is derived from your output cap: `budget = 1024 + ratio x (max_tokens - 1024)` with ratios `minimal 0.025`, `low 0.15`, `medium 0.425`, `high 0.80`, `xhigh 0.92`, `max 1.0`. Claude Opus and Sonnet 4.6+ use the provider's adaptive thinking with your effort passed through (`minimal` maps to `low`). Gemini thinking models receive the effort natively. Thinking tokens count inside `usage.completion_tokens`.