From 6501b7696dbae91df5ffffa5d21b90a7df49225f Mon Sep 17 00:00:00 2001
From: gpotter2 <10530980+gpotter2@users.noreply.github.com>
Date: Wed, 5 Aug 2026 19:05:21 +0200
Subject: [PATCH] copilot: document 'extraBody'

---
 docs/agent-customization/language-models.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/agent-customization/language-models.md b/docs/agent-customization/language-models.md
index 73c0214fbc..0e24d9e472 100644
--- a/docs/agent-customization/language-models.md
+++ b/docs/agent-customization/language-models.md
@@ -276,6 +276,7 @@ In addition to the [common model properties](#model-configuration-reference) the
 | `contextWindow` | _(Optional)_ The model's full context window (input + output) in tokens, for example `1000000` for a 1M-token model. When set, you can omit `maxInputTokens` and VS Code derives it as `contextWindow - maxOutputTokens`. |
 | `modelOptions` | _(Optional)_ An object of request parameters sent with every request to the model, such as `temperature` and `top_p`. For example, `"modelOptions": { "temperature": 0.2 }`. |
 | `requestHeaders` | _(Optional)_ An object of additional HTTP headers to include with requests to this model, for example to authenticate through a gateway or vanity domain. See [Custom authentication headers](#custom-authentication-headers). |
+| `extraBody` | _(Optional)_ Additional JSON properties to include in the request parameters. This allows to support custom parameters engines might support, such as vLLM's `top_k`, QwenCloud's `enable_thinking` or SGLang's `chat_template_kwargs`. (for example, `extraBody: {"ttl": 300}` or `extraBody: {"chat_template_kwargs": {"enable_thinking": false}}`) |
 
 ##### Endpoint URL resolution
 
@@ -422,6 +423,7 @@ Each model in the `models` array supports the following properties:
 | `supportsReasoningEffort` | _(Optional)_ An array of reasoning effort levels the model accepts (for example, `["low", "medium", "high"]`). When set, a **Thinking Effort** picker is shown in the model picker. Common levels are `minimal`, `low`, `medium`, `high`. |
 | `reasoningEffortFormat` | _(Optional)_ Body shape used to forward reasoning effort to the model. `chat-completions` sends a top-level `reasoning_effort` string, `responses` sends a nested `reasoning.effort` object, and `messages` sends `output_config.effort`. When unset, the format follows the URL. |
 | `requestHeaders` | _(Optional)_ An object of additional HTTP headers to include with requests to this model. Certain reserved headers (forbidden, forwarding, and internal headers) are not allowed and are ignored if present. |
+| `extraBody` | _(Optional)_ Additional JSON properties to include in the request parameters. This is more useful with custom endpoints (see [Custom endpoint](#add-a-custom-endpoint-model)), but you can also provide undocumented request parameters if instructed by the provider. |
 
 > [!NOTE]
 > The sum of `maxInputTokens` and `maxOutputTokens` must not exceed the model's context window. VS Code uses the sum of these two values as the model's total context window, for example to show context usage in the Chat view. Typically, you set `maxInputTokens` to the model's context window size minus `maxOutputTokens`. Check your provider's model documentation for the context window size.