diff --git a/README.md b/README.md
index e01d54b3..b4a2861f 100644
--- a/README.md
+++ b/README.md
@@ -704,8 +704,24 @@ npm/                 - NPM package wrapper for distribution
 - **Google Vertex** - Claude on Vertex AI
 - **OpenRouter** - Multi-provider router
 - **Vercel AI** - Vercel AI SDK models
+- **Custom** - Any OpenAI-compatible endpoint via `--provider-url`
 - **Auto-routed** - Any provider from models.dev database
 
+### Custom Provider
+
+Use `custom/custom` when pointing Kit at any OpenAI-compatible endpoint with `--provider-url`:
+
+```bash
+kit --provider-url "http://localhost:8080/v1" "Hello"
+```
+
+This automatically defaults to `custom/custom` without needing to specify a model. The custom provider routes through fantasy's `openaicompat` provider and supports:
+
+- Zero cost tracking (input/output = 0)
+- 262K context window, 65K output limit
+- Reasoning and temperature support
+- Optional `CUSTOM_API_KEY` environment variable or `--provider-api-key` flag
+
 ### Model String Format
 
 ```bash
diff --git a/www/pages/providers.md b/www/pages/providers.md
index cbe4f4f4..a45339b0 100644
--- a/www/pages/providers.md
+++ b/www/pages/providers.md
@@ -20,6 +20,7 @@ Kit supports a wide range of LLM providers through a unified `provider/model` st
 | **Google Vertex** | `google-vertex-anthropic/` | Claude on Vertex AI |
 | **OpenRouter** | `openrouter/` | Multi-provider router |
 | **Vercel AI** | `vercel/` | Vercel AI SDK models |
+| **Custom** | `custom/` | Any OpenAI-compatible endpoint |
 | **Auto-routed** | any | Any provider from the models.dev database |
 
 ## Model string format
@@ -132,6 +133,16 @@ For self-hosted or proxy endpoints:
 kit --provider-url "https://my-proxy.example.com/v1" --model openai/gpt-4o
 ```
 
+When `--provider-url` is provided without `--model`, Kit automatically defaults to `custom/custom`:
+
+```bash
+kit --provider-url "http://localhost:8080/v1" "Hello"
+```
+
+The `custom/custom` model has zero cost, 262K context window, and supports reasoning. It routes through fantasy's `openaicompat` provider and accepts any OpenAI-compatible API endpoint.
+
+Optionally set `CUSTOM_API_KEY` environment variable or use `--provider-api-key` for endpoints requiring authentication.
+
 ## Model database
 
 Kit ships with a local model database that maps provider names to API configurations. You can manage it with: