diff --git a/packages/generate-text/src/index.ts b/packages/generate-text/src/index.ts
index 05a8fa4..3f5a4aa 100644
--- a/packages/generate-text/src/index.ts
+++ b/packages/generate-text/src/index.ts
@@ -5,6 +5,7 @@ import {
   type FinishReason,
   type Message,
   type Tool,
+  type Usage,
 } from '@xsai/shared-chat'
 
 export interface GenerateTextOptions extends ChatOptions {
@@ -28,13 +29,7 @@ export interface GenerateTextResponse {
   model: string
   object: 'chat.completion'
   system_fingerprint: string
-  usage: GenerateTextResponseUsage
-}
-
-export interface GenerateTextResponseUsage {
-  completion_tokens: number
-  prompt_tokens: number
-  total_tokens: number
+  usage: Usage
 }
 
 export interface ToolCall {
@@ -57,7 +52,7 @@ export interface GenerateTextResult {
   text?: string
   toolCalls: ToolCall[]
   toolResults: ToolResult[]
-  usage: GenerateTextResponseUsage
+  usage: Usage
 }
 
 export interface StepResult {
@@ -66,7 +61,7 @@ export interface StepResult {
   // type: 'continue' | 'initial' | 'tool-result'
   toolCalls: ToolCall[]
   toolResults: ToolResult[]
-  usage: GenerateTextResponseUsage
+  usage: Usage
 }
 
 /** @internal */
diff --git a/packages/shared-chat/src/types/index.ts b/packages/shared-chat/src/types/index.ts
index 33aa846..ba56499 100644
--- a/packages/shared-chat/src/types/index.ts
+++ b/packages/shared-chat/src/types/index.ts
@@ -4,3 +4,4 @@ export type * from './message'
 export type * from './message-part'
 export type * from './tool'
 export type * from './tool-choice'
+export type * from './usage'
diff --git a/packages/shared-chat/src/types/usage.ts b/packages/shared-chat/src/types/usage.ts
new file mode 100644
index 0000000..0a9287c
--- /dev/null
+++ b/packages/shared-chat/src/types/usage.ts
@@ -0,0 +1,5 @@
+export interface Usage {
+  completion_tokens: number
+  prompt_tokens: number
+  total_tokens: number
+}
diff --git a/packages/stream-text/src/index.ts b/packages/stream-text/src/index.ts
index 794317c..9c09e31 100644
--- a/packages/stream-text/src/index.ts
+++ b/packages/stream-text/src/index.ts
@@ -2,10 +2,11 @@ import {
   chat,
   type ChatOptions,
   type FinishReason,
+  type Usage,
 } from '@xsai/shared-chat'
 
 export interface StreamTextOptions extends ChatOptions {
-  onChunk?: (chunk: StreamTextResponse) => Promise<void> | void
+  onChunk?: (chunk: ChunkResult) => Promise<void> | void
   /** if you want to disable stream, use `@xsai/generate-{text,object}` */
   stream?: never
   streamOptions?: {
@@ -18,21 +19,15 @@ export interface StreamTextOptions extends ChatOptions {
   }
 }
 
-export interface StreamTextResponseUsage {
-  completion_tokens: number
-  prompt_tokens: number
-  total_tokens: number
-}
-
 export interface StreamTextResult {
-  chunkStream: ReadableStream<StreamTextResponse>
+  chunkStream: ReadableStream<ChunkResult>
   finishReason?: FinishReason
   textStream: ReadableStream<string>
-  usage?: StreamTextResponseUsage
+  usage?: Usage
 }
 
 // TODO: improve chunk type
-export interface StreamTextResponse {
+export interface ChunkResult {
   choices: {
     delta: {
       content: string
@@ -46,7 +41,7 @@ export interface StreamTextResponse {
   model: string
   object: 'chat.completion.chunk'
   system_fingerprint: string
-  usage?: StreamTextResponseUsage
+  usage?: Usage
 }
 
 const chunkHeaderPrefix = 'data: '
@@ -62,7 +57,7 @@ export const streamText = async (options: StreamTextOptions): Promise<StreamText
   const decoder = new TextDecoder()
 
   let finishReason: string | undefined
-  let usage: StreamTextResponseUsage | undefined
+  let usage: undefined | Usage
   let buffer = ''
 
   // null body handled by import('@xsai/shared-chat').chat()
@@ -92,7 +87,7 @@ export const streamText = async (options: StreamTextOptions): Promise<StreamText
           break
         }
 
-        const chunk: StreamTextResponse = JSON.parse(lineWithoutPrefix)
+        const chunk: ChunkResult = JSON.parse(lineWithoutPrefix)
         controller.enqueue(chunk)
 
         if (options.onChunk)
diff --git a/packages/xsai/src/index.ts b/packages/xsai/src/index.ts
index d04bf16..5dfb2b9 100644
--- a/packages/xsai/src/index.ts
+++ b/packages/xsai/src/index.ts
@@ -6,11 +6,11 @@ export * as providers from './providers'
 export { embed, embedMany, type EmbedManyOptions, type EmbedManyResult, type EmbedOptions, type EmbedResponseUsage, type EmbedResult } from '@xsai/embed'
 export { generateObject, type GenerateObjectOptions, type GenerateObjectResult } from '@xsai/generate-object'
 export { generateSpeech, type GenerateSpeechOptions } from '@xsai/generate-speech'
-export { generateText, type GenerateTextOptions, type GenerateTextResponseUsage, type GenerateTextResult } from '@xsai/generate-text'
+export { generateText, type GenerateTextOptions, type GenerateTextResponse, type GenerateTextResult, type StepResult } from '@xsai/generate-text'
 export { generateTranscription, type GenerateTranscriptionOptions, type GenerateTranscriptionResult } from '@xsai/generate-transcription'
 export { listModels, type ListModelsOptions, type ListModelsResponse, type Model, retrieveModel, type RetrieveModelOptions } from '@xsai/model'
 // shared chat utils
 export * from '@xsai/shared-chat'
 export { streamObject, type StreamObjectOptions, type StreamObjectResult } from '@xsai/stream-object'
-export { streamText, type StreamTextOptions, type StreamTextResponse, type StreamTextResponseUsage, type StreamTextResult } from '@xsai/stream-text'
+export { type ChunkResult, streamText, type StreamTextOptions, type StreamTextResult } from '@xsai/stream-text'
 export { tool, type ToolOptions, type ToolResult } from '@xsai/tool'