diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 251e1aff..3a47e78c 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -2,6 +2,9 @@
 
 ## [Unreleased]
 
+### Fixed
+- Fixed 422 error with non-standard providers (gatewayz.ai, chutes.ai, etc.) by adding `supportsStreamOptions` compatibility flag and conditionally sending `stream_options` parameter.
+
 ## [0.42.0] - 2026-01-09
 
 ### Added
diff --git a/packages/ai/src/providers/openai-completions.ts b/packages/ai/src/providers/openai-completions.ts
index 0c32784d..53cf6d19 100644
--- a/packages/ai/src/providers/openai-completions.ts
+++ b/packages/ai/src/providers/openai-completions.ts
@@ -367,9 +367,12 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 		model: model.id,
 		messages,
 		stream: true,
-		stream_options: { include_usage: true },
 	};
 
+	if (compat.supportsStreamOptions) {
+		(params as any).stream_options = { include_usage: true };
+	}
+
 	if (compat.supportsStore) {
 		params.store = false;
 	}
@@ -641,7 +644,8 @@ function detectCompatFromUrl(baseUrl: string): Required<OpenAICompat> {
 		baseUrl.includes("cerebras.ai") ||
 		baseUrl.includes("api.x.ai") ||
 		baseUrl.includes("mistral.ai") ||
-		baseUrl.includes("chutes.ai");
+		baseUrl.includes("chutes.ai") ||
+		baseUrl.includes("gatewayz.ai");
 
 	const useMaxTokens = baseUrl.includes("mistral.ai") || baseUrl.includes("chutes.ai");
 
@@ -653,6 +657,7 @@ function detectCompatFromUrl(baseUrl: string): Required<OpenAICompat> {
 		supportsStore: !isNonStandard,
 		supportsDeveloperRole: !isNonStandard,
 		supportsReasoningEffort: !isGrok,
+		supportsStreamOptions: !isNonStandard,
 		maxTokensField: useMaxTokens ? "max_tokens" : "max_completion_tokens",
 		requiresToolResultName: isMistral,
 		requiresAssistantAfterToolResult: false, // Mistral no longer requires this as of Dec 2024
@@ -673,6 +678,7 @@ function getCompat(model: Model<"openai-completions">): Required<OpenAICompat> {
 		supportsStore: model.compat.supportsStore ?? detected.supportsStore,
 		supportsDeveloperRole: model.compat.supportsDeveloperRole ?? detected.supportsDeveloperRole,
 		supportsReasoningEffort: model.compat.supportsReasoningEffort ?? detected.supportsReasoningEffort,
+		supportsStreamOptions: model.compat.supportsStreamOptions ?? detected.supportsStreamOptions,
 		maxTokensField: model.compat.maxTokensField ?? detected.maxTokensField,
 		requiresToolResultName: model.compat.requiresToolResultName ?? detected.requiresToolResultName,
 		requiresAssistantAfterToolResult:
diff --git a/packages/ai/src/types.ts b/packages/ai/src/types.ts
index 75ba8a6b..d3198a6a 100644
--- a/packages/ai/src/types.ts
+++ b/packages/ai/src/types.ts
@@ -207,6 +207,8 @@ export interface OpenAICompat {
 	supportsDeveloperRole?: boolean;
 	/** Whether the provider supports `reasoning_effort`. Default: auto-detected from URL. */
 	supportsReasoningEffort?: boolean;
+	/** Whether the provider supports `stream_options`. Default: auto-detected from URL. */
+	supportsStreamOptions?: boolean;
 	/** Which field to use for max tokens. Default: auto-detected from URL. */
 	maxTokensField?: "max_completion_tokens" | "max_tokens";
 	/** Whether tool results require the `name` field. Default: auto-detected from URL. */