diff --git a/providers/anthropic/anthropic.go b/providers/anthropic/anthropic.go
index 01e049358..2481be5c9 100644
--- a/providers/anthropic/anthropic.go
+++ b/providers/anthropic/anthropic.go
@@ -42,6 +42,11 @@ func betaRequestOptions(flags []string) []option.RequestOption {
 // by Generate and Stream: user-agent, raw tool injection, and any
 // beta API flags.
 func buildRequestOptions(call fantasy.Call, rawTools []json.RawMessage, betaFlags []string) []option.RequestOption {
+	providerOptions := &ProviderOptions{}
+	if v, ok := call.ProviderOptions[Name]; ok {
+		providerOptions, _ = v.(*ProviderOptions)
+	}
+
 	reqOpts := callUARequestOptions(call)
 	if len(rawTools) > 0 {
 		// Tools are injected as raw JSON rather than via params.Tools
@@ -50,6 +55,9 @@ func buildRequestOptions(call fantasy.Call, rawTools []json.RawMessage, betaFlag
 		// this will need updating.
 		reqOpts = append(reqOpts, option.WithJSONSet("tools", rawTools))
 	}
+	for k, v := range providerOptions.ExtraBody {
+		reqOpts = append(reqOpts, option.WithJSONSet(k, v))
+	}
 	if len(betaFlags) > 0 {
 		reqOpts = append(reqOpts, betaRequestOptions(betaFlags)...)
 	}
diff --git a/providers/anthropic/provider_options.go b/providers/anthropic/provider_options.go
index ae643b3c7..4c89a4438 100644
--- a/providers/anthropic/provider_options.go
+++ b/providers/anthropic/provider_options.go
@@ -71,6 +71,7 @@ type ProviderOptions struct {
 	Thinking               *ThinkingProviderOption `json:"thinking"`
 	Effort                 *Effort                 `json:"effort"`
 	DisableParallelToolUse *bool                   `json:"disable_parallel_tool_use"`
+	ExtraBody              map[string]any          `json:"extra_body,omitempty"`
 }
 
 // Options implements the ProviderOptions interface.