diff --git a/internal/providers/openai.go b/internal/providers/openai.go
index 97ac6fe2..ed51c8ff 100644
--- a/internal/providers/openai.go
+++ b/internal/providers/openai.go
@@ -103,6 +103,7 @@ func (p *OpenAIProvider) ChatStream(ctx context.Context, req ChatRequest, onChun
 	accumulators := make(map[int]*toolCallAccumulator)
 
 	scanner := bufio.NewScanner(respBody)
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024) // 1MB max line for large tool call / thinking chunks
 	for scanner.Scan() {
 		line := scanner.Text()
 		if !strings.HasPrefix(line, "data:") {
@@ -185,11 +186,6 @@ func (p *OpenAIProvider) ChatStream(ctx context.Context, req ChatRequest, onChun
 		return nil, fmt.Errorf("%s: stream read error: %w", p.name, err)
 	}
 
-	// Check for scanner errors (timeout, connection reset, etc.)
-	if err := scanner.Err(); err != nil {
-		return nil, fmt.Errorf("%s: stream read error: %w", p.name, err)
-	}
-
 	// Parse accumulated tool call arguments
 	for i := 0; i < len(accumulators); i++ {
 		acc := accumulators[i]