fix(ai/providers): restricted service tier usage to OpenAI-compatible providers

- Replaced service-tier gating in OpenAI provider request builders with provider-aware checks before writing params.service_tier.
- Updated the shared service-tier helper to accept provider context and only return true for flex, scale, or priority on openai/openai-codex providers.

packages/ai/src/providers/azure-openai-responses.ts

@@ -10,11 +10,11 @@ import {
 	type Api,
 	type AssistantMessage,
 	type Context,
-	isSpecialServiceTier,
 	type Model,
 	type ServiceTier,
 	type StreamFunction,
 	type StreamOptions,
+	shouldSendServiceTier,
 	type Tool,
 	type ToolChoice,
 } from "../types";
@@ -298,7 +298,7 @@ function buildParams(
 	if (options?.repetitionPenalty !== undefined) {
 		params.repetition_penalty = options.repetitionPenalty;
 	}
-	if (isSpecialServiceTier(options?.serviceTier)) {
+	if (shouldSendServiceTier(options?.serviceTier, model.provider)) {
 		params.service_tier = options.serviceTier;
 	}
 

packages/ai/src/providers/openai-codex-responses.ts

@@ -19,12 +19,12 @@ import {
 	type Api,
 	type AssistantMessage,
 	type Context,
-	isSpecialServiceTier,
 	type Model,
 	type ProviderSessionState,
 	type ServiceTier,
 	type StreamFunction,
 	type StreamOptions,
+	shouldSendServiceTier,
 	type TextContent,
 	type ThinkingContent,
 	type Tool,
@@ -493,7 +493,7 @@ async function buildTransformedCodexRequestBody(
 	if (options?.repetitionPenalty !== undefined) {
 		params.repetition_penalty = options.repetitionPenalty;
 	}
-	if (isSpecialServiceTier(options?.serviceTier)) {
+	if (shouldSendServiceTier(options?.serviceTier, model.provider)) {
 		params.service_tier = options.serviceTier;
 	}
 	if (context.tools && context.tools.length > 0) {

packages/ai/src/providers/openai-completions.ts

@@ -14,7 +14,6 @@ import { getEnvApiKey } from "../stream";
 import {
 	type AssistantMessage,
 	type Context,
-	isSpecialServiceTier,
 	type Message,
 	type MessageAttribution,
 	type Model,
@@ -23,6 +22,7 @@ import {
 	type StopReason,
 	type StreamFunction,
 	type StreamOptions,
+	shouldSendServiceTier,
 	type TextContent,
 	type ThinkingContent,
 	type Tool,
@@ -811,7 +811,7 @@ function buildParams(
 	if (options?.repetitionPenalty !== undefined) {
 		params.repetition_penalty = options.repetitionPenalty;
 	}
-	if (isSpecialServiceTier(options?.serviceTier)) {
+	if (shouldSendServiceTier(options?.serviceTier, model.provider)) {
 		params.service_tier = options.serviceTier;
 	}
 

packages/ai/src/providers/openai-responses.ts

@@ -11,13 +11,13 @@ import {
 	type AssistantMessage,
 	type CacheRetention,
 	type Context,
-	isSpecialServiceTier,
 	type MessageAttribution,
 	type Model,
 	type ProviderSessionState,
 	type ServiceTier,
 	type StreamFunction,
 	type StreamOptions,
+	shouldSendServiceTier,
 	type Tool,
 	type ToolChoice,
 } from "../types";
@@ -384,7 +384,7 @@ function buildParams(
 	if (options?.repetitionPenalty !== undefined) {
 		params.repetition_penalty = options.repetitionPenalty;
 	}
-	if (isSpecialServiceTier(options?.serviceTier)) {
+	if (shouldSendServiceTier(options?.serviceTier, model.provider)) {
 		params.service_tier = options.serviceTier;
 	}
 

packages/ai/src/types.ts

@@ -152,7 +152,13 @@ export type CacheRetention = "none" | "short" | "long";
 /** OpenAI service tier for processing priority. Only applies to OpenAI-compatible APIs. */
 export type ServiceTier = "auto" | "default" | "flex" | "scale" | "priority";
 
-export function isSpecialServiceTier(serviceTier?: ServiceTier | null): serviceTier is "flex" | "scale" | "priority" {
+export function shouldSendServiceTier(
+	serviceTier?: ServiceTier | null,
+	provider?: Provider,
+): serviceTier is "flex" | "scale" | "priority" {
+	if (provider !== "openai" && provider !== "openai-codex") {
+		return false;
+	}
 	return serviceTier === "flex" || serviceTier === "scale" || serviceTier === "priority";
 }