Backport: add caching provider option to GatewayProviderOptions

.changeset/gateway-caching-provider-option.md

@@ -0,0 +1,5 @@
+---
+"@ai-sdk/gateway": patch
+---
+
+feat(gateway): add `caching` provider option to `GatewayProviderOptions`

packages/gateway/src/gateway-provider-options.ts

@@ -108,6 +108,15 @@ const gatewayProviderOptions = lazySchema(() =>
        * default.
        */
       serviceTier: z.enum(['flex', 'priority']).optional(),
+      /**
+       * Enables automatic prompt caching across providers. When set to
+       * `'auto'`, the gateway applies the appropriate caching strategy for
+       * the routed provider: it adds a `cache_control` breakpoint to static
+       * content for providers that require explicit markers (such as
+       * Anthropic), while providers with implicit caching cache
+       * automatically. Leave unset to pass requests through unmodified.
+       */
+      caching: z.literal('auto').optional(),
     }),
   ),
 );