**fix(runtime): simplify scanner buffer allocation in executor implementations**

internal/runtime/executor/claude_executor.go

@@ -219,8 +219,7 @@ func (e *ClaudeExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.A
 		// If from == to (Claude → Claude), directly forward the SSE stream without translation
 		if from == to {
 			scanner := bufio.NewScanner(decodedBody)
-			buf := make([]byte, 20_971_520)
-			scanner.Buffer(buf, 20_971_520)
+			scanner.Buffer(nil, 20_971_520)
 			for scanner.Scan() {
 				line := scanner.Bytes()
 				appendAPIResponseChunk(ctx, e.cfg, line)
@@ -243,8 +242,7 @@ func (e *ClaudeExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.A
 
 		// For other formats, use translation
 		scanner := bufio.NewScanner(decodedBody)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/codex_executor.go

@@ -205,8 +205,7 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 			}
 		}()
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/gemini_cli_executor.go

@@ -319,8 +319,7 @@ func (e *GeminiCLIExecutor) ExecuteStream(ctx context.Context, auth *cliproxyaut
 			}()
 			if opts.Alt == "" {
 				scanner := bufio.NewScanner(resp.Body)
-				buf := make([]byte, 20_971_520)
-				scanner.Buffer(buf, 20_971_520)
+				scanner.Buffer(nil, 20_971_520)
 				var param any
 				for scanner.Scan() {
 					line := scanner.Bytes()

internal/runtime/executor/gemini_executor.go

@@ -251,8 +251,7 @@ func (e *GeminiExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.A
 			}
 		}()
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/gemini_vertex_executor.go

@@ -240,8 +240,7 @@ func (e *GeminiVertexExecutor) ExecuteStream(ctx context.Context, auth *cliproxy
 			}
 		}()
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/iflow_executor.go

@@ -199,8 +199,7 @@ func (e *IFlowExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 		}()
 
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/openai_compat_executor.go

@@ -205,8 +205,7 @@ func (e *OpenAICompatExecutor) ExecuteStream(ctx context.Context, auth *cliproxy
 			}
 		}()
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()

internal/runtime/executor/qwen_executor.go

@@ -181,8 +181,7 @@ func (e *QwenExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Aut
 			}
 		}()
 		scanner := bufio.NewScanner(httpResp.Body)
-		buf := make([]byte, 20_971_520)
-		scanner.Buffer(buf, 20_971_520)
+		scanner.Buffer(nil, 20_971_520)
 		var param any
 		for scanner.Scan() {
 			line := scanner.Bytes()