docs: add The Grid custom LLM guide

fern/customization/custom-llm/thegrid.mdx

@@ -0,0 +1,78 @@
+---
+title: The Grid
+subtitle: Use The Grid instruments in Vapi through the custom-llm provider
+description: Wire The Grid, an OpenAI-compatible inference marketplace, into Vapi with the custom-llm provider and Custom Credentials.
+slug: customization/custom-llm/thegrid
+---
+
+The Grid is an inference marketplace that serves models from several labs behind one OpenAI-compatible API. Its instrument IDs describe capability tiers rather than specific lab models.
+
+`text-standard`, `code-prime`, and `agent-max` each route to a current model for that tier. When The Grid replaces an underlying model, an assistant can keep using the same instrument ID.
+
+The Grid exposes an OpenAI-compatible Chat Completions API, so you can connect it to Vapi as a [custom LLM](/customization/custom-llm/fine-tuned-openai-models).
+
+Before starting, create an account with The Grid and a [Consumption API key](https://thegrid.ai/docs/api-reference/authentication).
+
+## Add your credential
+
+Send the following body to `POST https://api.vapi.ai/credential`. Use your [Vapi private API key](/security-and-privacy/api-keys) in the `Authorization: Bearer <VAPI_PRIVATE_KEY>` header:
+
+```json
+{
+  "provider": "custom-llm",
+  "apiKey": "<YOUR THE GRID API KEY>"
+}
+```
+
+Save the credential `id` from the response. Add it to the assistant's `credentialIds` to select that credential.
+
+## Create the assistant
+
+Send this body to `POST https://api.vapi.ai/assistant` with the same Vapi private API key. Set `model.url` to The Grid's base URL and `model.model` to an instrument ID:
+
+```json
+{
+  "name": "My Assistant",
+  "credentialIds": ["<YOUR THE GRID CREDENTIAL ID>"],
+  "model": {
+    "provider": "custom-llm",
+    "url": "https://api.thegrid.ai/v1",
+    "model": "text-standard",
+    "metadataSendMode": "off",
+    "maxTokens": 600,
+    "messages": [
+      {
+        "role": "system",
+        "content": "You are a helpful voice assistant. Keep replies short."
+      }
+    ]
+  }
+}
+```
+
+Setting `metadataSendMode` to `off` keeps Vapi call metadata out of requests to The Grid.
+
+## Choose an instrument
+
+`GET https://api.thegrid.ai/v1/models` lists available instrument IDs. Check [instrument specifications](https://thegrid.ai/instruments) and [pricing](https://thegrid.ai/pricing) for current details. Examples include:
+
+| Instrument | Use it for |
+| --- | --- |
+| `text-standard` | General conversation. The usual starting point. |
+| `text-prime`, `text-max` | More demanding questions; compare current speed and price. |
+| `agent-standard`, `agent-max` | Multi-step tool use. |
+| `code-standard`, `code-prime` | Assistants that read or write code. |
+
+## Set `maxTokens` for spoken replies
+
+Vapi uses `250` for `maxTokens` when it is omitted and sends the value to The Grid as `max_tokens`. A low cap can cut off a response.
+
+The `600` value in the example is a starting point. Test your chosen instrument with representative spoken turns and raise the limit if replies are truncated. Keep the system prompt explicit about brevity.
+
+## Tool calling
+
+The Grid's API supports OpenAI-style function calling. To configure Vapi tools, see the [tool calling integration guide](/customization/tool-calling-integration). Test a tool call with your chosen instrument before relying on it.
+
+## Verify the assistant
+
+Start a test call and ask the assistant a short question. Confirm it speaks a complete answer. Check the call logs for custom LLM errors. If you attached a tool, request an action that uses it. Confirm the tool runs.

fern/docs.yml

@@ -858,6 +858,8 @@ navigation:
                     path: providers/model/openrouter.mdx
                   - page: Perplexity
                     path: providers/model/perplexity.mdx
+                  - page: The Grid
+                    path: customization/custom-llm/thegrid.mdx
                   - page: TogetherAI
                     path: providers/model/togetherai.mdx
                   - page: xAI

fern/providers/model/overview.mdx

@@ -31,19 +31,14 @@ The provider string is the exact value you pass in `model.provider`.
 | [OpenAI](/providers/model/openai#language-model) | `openai` |
 | [OpenRouter](/providers/model/openrouter#language-model) | `openrouter` |
 | [Perplexity](/providers/model/perplexity#language-model) | `perplexity-ai` |
+| [The Grid](/customization/custom-llm/thegrid) | `custom-llm` |
 | [Together AI](/providers/model/togetherai#language-model) | `together-ai` |
 | [xAI](/providers/model/xai#language-model) | `xai` |
 
 <Note>
 The **Assistant → Model** dropdown in the [Vapi Dashboard](https://dashboard.vapi.ai) is the most current list of selectable models.
 </Note>
 
-{/* verify: access mode is feature-flag gated per provider; confirm current state before publishing.
-Some providers are Vapi-managed (selectable without your own key); others require your own key
-added under Integrations. Anthropic and Anthropic (Bedrock) are two routes to the same Claude
-models, kept as separate pages. Vapi (white-label model) is omitted because it is gated by the enable-vapi-model
-flag and not generally visible. Mistral is dashboard-only (not in the public API model union). */}
-
 ## Related
 
 <CardGroup cols={2}>