diff --git a/src/converters/streaming.ts b/src/converters/streaming.ts
index 78445ab..39729a3 100644
--- a/src/converters/streaming.ts
+++ b/src/converters/streaming.ts
@@ -3,6 +3,7 @@ import { FastifyReply } from 'fastify';
 import { Stream } from 'openai/streaming';
 import {
     AnthropicMessageResponse,
+    AnthropicStreamEvent,
     AnthropicUsage,
 } from '../types/anthropic';
 import { OpenAIStreamChunk, OpenAIStreamToolCall } from '../types/openai';
@@ -216,7 +217,7 @@ function processToolCallDelta(
 }
 
 function sendMessageStart(state: StreamingState, raw: any): void {
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'message_start',
         message: {
             id: state.messageId,
@@ -229,10 +230,12 @@ function sendMessageStart(state: StreamingState, raw: any): void {
             usage: {
                 input_tokens: state.inputTokens,
                 output_tokens: state.outputTokens,
-                cache_read_input_tokens: state.cachedInputTokens,
-            },
+            } as AnthropicUsage,
         },
     };
+    if (state.cachedInputTokens > 0) {
+        event.message.usage.cache_read_input_tokens = state.cachedInputTokens;
+    }
     sendSSE(event, raw);
 }
 
@@ -256,7 +259,7 @@ function sendContentBlockStart(
         };
     }
 
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'content_block_start',
         index,
         content_block: contentBlock,
@@ -265,7 +268,7 @@ function sendContentBlockStart(
 }
 
 function sendTextDelta(index: number, text: string, raw: any): void {
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'content_block_delta',
         index,
         delta: {
@@ -277,7 +280,7 @@ function sendTextDelta(index: number, text: string, raw: any): void {
 }
 
 function sendInputJsonDelta(index: number, partialJson: string, raw: any): void {
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'content_block_delta',
         index,
         delta: {
@@ -289,7 +292,7 @@ function sendInputJsonDelta(index: number, partialJson: string, raw: any): void
 }
 
 function sendContentBlockStop(index: number, raw: any): void {
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'content_block_stop',
         index,
     };
@@ -313,21 +316,23 @@ function finishStream(state: StreamingState, raw: any): void {
     });
 
     // Send message_delta
-    const deltaEvent = {
+    const usage: any = {
+        output_tokens: state.outputTokens,
+    };
+    if (state.cachedInputTokens > 0) {
+        usage.cache_read_input_tokens = state.cachedInputTokens;
+    }
+    const deltaEvent: AnthropicStreamEvent = {
         type: 'message_delta',
         delta: {
-            stop_reason: stopReason,
-            stop_sequence: null,
-        },
-        usage: {
-            output_tokens: state.outputTokens,
-            cache_read_input_tokens: state.cachedInputTokens,
+            stop_reason: stopReason as 'end_turn' | 'max_tokens' | 'stop_sequence' | 'tool_use',
         },
+        usage,
     };
     sendSSE(deltaEvent, raw);
 
     // Send message_stop
-    sendSSE({ type: 'message_stop' }, raw);
+    sendSSE({ type: 'message_stop' } as AnthropicStreamEvent, raw);
 
     raw.end();
 }
@@ -341,7 +346,7 @@ function sendErrorEvent(error: Error, state: StreamingState, raw: any): void {
         streaming: true
     });
 
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'error',
         error: {
             type: 'api_error',
@@ -352,7 +357,7 @@ function sendErrorEvent(error: Error, state: StreamingState, raw: any): void {
     raw.end();
 }
 
-function sendSSE(data: any, raw: any): void {
+function sendSSE(data: AnthropicStreamEvent, raw: any): void {
     raw.write(`event: ${data.type}\n`);
     raw.write(`data: ${JSON.stringify(data)}\n\n`);
 }
diff --git a/src/converters/xmlStreaming.ts b/src/converters/xmlStreaming.ts
index 8646606..68f860d 100644
--- a/src/converters/xmlStreaming.ts
+++ b/src/converters/xmlStreaming.ts
@@ -3,6 +3,7 @@
 
 import { FastifyReply } from 'fastify';
 import { Stream } from 'openai/streaming';
+import { AnthropicStreamEvent, AnthropicUsage } from '../types/anthropic';
 import { OpenAIStreamChunk } from '../types/openai';
 import { generateToolUseId } from './tools';
 import { recordUsage } from '../utils/tokenUsage';
@@ -175,7 +176,7 @@ function cleanToolArgs(args: string): string {
 
 function emitTextBlock(text: string, state: BufferedState, raw: any): void {
     // Start text block
-    const startEvent = {
+    const startEvent: AnthropicStreamEvent = {
         type: 'content_block_start',
         index: state.contentBlockIndex,
         content_block: { type: 'text', text: '' },
@@ -183,7 +184,7 @@ function emitTextBlock(text: string, state: BufferedState, raw: any): void {
     sendSSE(startEvent, raw);
 
     // Send text delta
-    const deltaEvent = {
+    const deltaEvent: AnthropicStreamEvent = {
         type: 'content_block_delta',
         index: state.contentBlockIndex,
         delta: { type: 'text_delta', text },
@@ -191,7 +192,7 @@ function emitTextBlock(text: string, state: BufferedState, raw: any): void {
     sendSSE(deltaEvent, raw);
 
     // Stop text block
-    const stopEvent = {
+    const stopEvent: AnthropicStreamEvent = {
         type: 'content_block_stop',
         index: state.contentBlockIndex,
     };
@@ -204,7 +205,7 @@ function emitToolUseBlock(toolName: string, args: string, state: BufferedState,
     const toolId = generateToolUseId();
 
     // Start tool_use block
-    const startEvent = {
+    const startEvent: AnthropicStreamEvent = {
         type: 'content_block_start',
         index: state.contentBlockIndex,
         content_block: {
@@ -217,7 +218,7 @@ function emitToolUseBlock(toolName: string, args: string, state: BufferedState,
     sendSSE(startEvent, raw);
 
     // Send complete input as single delta
-    const deltaEvent = {
+    const deltaEvent: AnthropicStreamEvent = {
         type: 'content_block_delta',
         index: state.contentBlockIndex,
         delta: {
@@ -228,7 +229,7 @@ function emitToolUseBlock(toolName: string, args: string, state: BufferedState,
     sendSSE(deltaEvent, raw);
 
     // Stop tool_use block
-    const stopEvent = {
+    const stopEvent: AnthropicStreamEvent = {
         type: 'content_block_stop',
         index: state.contentBlockIndex,
     };
@@ -239,7 +240,7 @@ function emitToolUseBlock(toolName: string, args: string, state: BufferedState,
 }
 
 function sendMessageStart(state: BufferedState, raw: any): void {
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'message_start',
         message: {
             id: state.messageId,
@@ -252,10 +253,12 @@ function sendMessageStart(state: BufferedState, raw: any): void {
             usage: {
                 input_tokens: state.inputTokens,
                 output_tokens: state.outputTokens,
-                cache_read_input_tokens: state.cachedInputTokens,
-            },
+            } as AnthropicUsage,
         },
     };
+    if (state.cachedInputTokens > 0) {
+        event.message.usage.cache_read_input_tokens = state.cachedInputTokens;
+    }
     sendSSE(event, raw);
 }
 
@@ -275,21 +278,23 @@ function finishStream(state: BufferedState, raw: any): void {
     });
 
     // Send message_delta
-    const deltaEvent = {
+    const usage: any = {
+        output_tokens: state.outputTokens,
+    };
+    if (state.cachedInputTokens > 0) {
+        usage.cache_read_input_tokens = state.cachedInputTokens;
+    }
+    const deltaEvent: AnthropicStreamEvent = {
         type: 'message_delta',
         delta: {
-            stop_reason: stopReason,
-            stop_sequence: null,
-        },
-        usage: {
-            output_tokens: state.outputTokens,
-            cache_read_input_tokens: state.cachedInputTokens,
+            stop_reason: stopReason as 'end_turn' | 'max_tokens' | 'stop_sequence' | 'tool_use',
         },
+        usage,
     };
     sendSSE(deltaEvent, raw);
 
     // Send message_stop
-    sendSSE({ type: 'message_stop' }, raw);
+    sendSSE({ type: 'message_stop' } as AnthropicStreamEvent, raw);
 
     raw.end();
 }
@@ -303,7 +308,7 @@ function sendErrorEvent(error: Error, state: BufferedState, raw: any): void {
         streaming: true
     });
 
-    const event = {
+    const event: AnthropicStreamEvent = {
         type: 'error',
         error: {
             type: 'api_error',
@@ -314,7 +319,7 @@ function sendErrorEvent(error: Error, state: BufferedState, raw: any): void {
     raw.end();
 }
 
-function sendSSE(data: any, raw: any): void {
+function sendSSE(data: AnthropicStreamEvent, raw: any): void {
     raw.write(`event: ${data.type}\n`);
     raw.write(`data: ${JSON.stringify(data)}\n\n`);
 }