diff --git a/src/content/changelog/ai-gateway/2026-05-18-rest-api.mdx b/src/content/changelog/ai-gateway/2026-05-18-rest-api.mdx
new file mode 100644
index 000000000000000..0bd29c50f7885d7
--- /dev/null
+++ b/src/content/changelog/ai-gateway/2026-05-18-rest-api.mdx
@@ -0,0 +1,32 @@
+---
+title: Call any AI model through AI Gateway's new REST API
+description: Call third-party and Workers AI models through one Cloudflare REST API, with AI Gateway features applied automatically.
+products:
+  - ai-gateway
+date: 2026-05-19
+---
+
+AI Gateway now uses the AI REST API on `api.cloudflare.com`. You can call any model — whether from OpenAI, Anthropic, Google, or hosted on Workers AI — through one unified API, using the same endpoints and authentication regardless of provider. Three endpoints are available:
+
+- `POST /ai/run` — universal endpoint for all models and modalities
+- `POST /ai/v1/chat/completions` — OpenAI SDK compatible
+- `POST /ai/v1/responses` — OpenAI Responses API compatible
+- `POST /ai/v1/messages` — Anthropic SDK compatible
+
+```bash
+curl -X POST "https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/chat/completions" \
+  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
+  --header "Content-Type: application/json" \
+  --data '{
+    "model": "openai/gpt-5.5",
+    "messages": [{"role": "user", "content": "What is Cloudflare?"}]
+  }'
+```
+
+All AI Gateway features — logging, caching, rate limiting, and guardrails — are applied automatically. Third-party models are billed through [Unified Billing](/ai-gateway/features/unified-billing/), so you do not need to manage separate provider API keys.
+
+Every request through the REST API is routed through your account's default gateway, which is created automatically on first use. To route requests through a specific gateway, add the `cf-aig-gateway-id` header.
+
+If you are already calling Workers AI models through the existing REST API, that path (`/ai/run/@cf/{model}`) continues to work. To call Workers AI models through AI Gateway, replace it with `/ai/run` and move the model name into the request body with `"provider": "cloudflare"`.
+
+For more details and examples, refer to the [REST API documentation](/ai-gateway/usage/rest-api/).
diff --git a/src/content/docs/ai-gateway/usage/rest-api.mdx b/src/content/docs/ai-gateway/usage/rest-api.mdx
index c948966cfa84708..c4f05d7773f604f 100644
--- a/src/content/docs/ai-gateway/usage/rest-api.mdx
+++ b/src/content/docs/ai-gateway/usage/rest-api.mdx
@@ -16,13 +16,14 @@ No provider SDKs or API keys are needed. Authentication and billing are handled
 
 ## Endpoints
 
-Three endpoints are available, each suited to different use cases:
+Four endpoints are available, each suited to different use cases:
 
 | Endpoint | Format | Use case |
 | -------- | ------ | -------- |
 | `POST /ai/run` | Envelope with `model`, `provider`, `input` | All models and modalities (LLM, image, TTS, ASR) |
 | `POST /ai/v1/chat/completions` | OpenAI chat completions | LLMs — OpenAI SDK compatible |
 | `POST /ai/v1/responses` | OpenAI Responses API | Agentic workflows — OpenAI SDK compatible |
+| `POST /ai/v1/messages` | Anthropic Messages API | LLMs — Anthropic SDK compatible |
 
 ## Authentication
 
@@ -178,6 +179,43 @@ const response = await openai.responses.create({
 });
 ```
 
+## `/ai/v1/messages` — Anthropic compatible
+
+Uses the Anthropic Messages API format. Compatible with the Anthropic SDK.
+
+```bash
+curl -X POST "https://api.cloudflare.com/client/v4/accounts/$CLOUDFLARE_ACCOUNT_ID/ai/v1/messages" \
+  --header "Authorization: Bearer $CLOUDFLARE_API_TOKEN" \
+  --header "Content-Type: application/json" \
+  --data '{
+    "model": "anthropic/claude-sonnet-4-5",
+    "max_tokens": 512,
+    "messages": [
+      {
+        "role": "user",
+        "content": "What is Cloudflare?"
+      }
+    ]
+  }'
+```
+
+Point the Anthropic SDK `baseURL` at the Cloudflare API:
+
+```javascript
+import Anthropic from "@anthropic-ai/sdk";
+
+const anthropic = new Anthropic({
+  apiKey: CLOUDFLARE_API_TOKEN,
+  baseURL: `https://api.cloudflare.com/client/v4/accounts/${ACCOUNT_ID}/ai/v1`,
+});
+
+const message = await anthropic.messages.create({
+  model: "anthropic/claude-sonnet-4-5",
+  max_tokens: 512,
+  messages: [{ role: "user", content: "What is Cloudflare?" }],
+});
+```
+
 ## Specify a gateway
 
 By default, third-party model requests route through your account's default AI Gateway. To use a specific gateway, include the `cf-aig-gateway-id` header: