fix(amp): address PR review - stream thinking suppression, SSE detection, test init

- Call suppressAmpThinking in rewriteStreamEvent for streaming path
- Handle nil return from suppressAmpThinking to skip suppressed events
- Narrow looksLikeSSEChunk to line-prefix detection (HasPrefix vs Contains)
- Initialize suppressedContentBlock map in test

internal/api/modules/amp/response_rewriter.go

@@ -36,14 +36,14 @@ func NewResponseRewriter(w gin.ResponseWriter, originalModel string) *ResponseRe
 const maxBufferedResponseBytes = 2 * 1024 * 1024 // 2MB safety cap
 
 func looksLikeSSEChunk(data []byte) bool {
-	return bytes.Contains(data, []byte("data:")) ||
+	for _, line := range bytes.Split(data, []byte("\n")) {
-		bytes.Contains(data, []byte("event:")) ||
+		trimmed := bytes.TrimSpace(line)
-		bytes.Contains(data, []byte("message_start")) ||
+		if bytes.HasPrefix(trimmed, []byte("data:")) ||
-		bytes.Contains(data, []byte("message_delta")) ||
+			bytes.HasPrefix(trimmed, []byte("event:")) {
-		bytes.Contains(data, []byte("content_block_start")) ||
+			return true
-		bytes.Contains(data, []byte("content_block_delta")) ||
+		}
-		bytes.Contains(data, []byte("content_block_stop")) ||
+	}
-		bytes.Contains(data, []byte("\n\n"))
+	return false
 }
 
 func (rw *ResponseRewriter) enableStreaming(reason string) error {
@@ -250,11 +250,15 @@ func (rw *ResponseRewriter) rewriteStreamChunk(chunk []byte) []byte {
 			}
 
 			if dataIdx >= 0 {
-				// Found event+data pair - process through model rewriter only
+				// Found event+data pair - process through rewriter
-				// (no thinking suppression for streaming)
 				jsonData := bytes.TrimPrefix(bytes.TrimSpace(lines[dataIdx]), []byte("data: "))
 				if len(jsonData) > 0 && jsonData[0] == '{' {
 					rewritten := rw.rewriteStreamEvent(jsonData)
+					if rewritten == nil {
+						// Event suppressed (e.g. thinking block), skip event+data pair
+						i = dataIdx + 1
+						continue
+					}
 					// Emit event line
 					out = append(out, line)
 					// Emit blank lines between event and data
@@ -280,7 +284,9 @@ func (rw *ResponseRewriter) rewriteStreamChunk(chunk []byte) []byte {
 			jsonData := bytes.TrimPrefix(trimmed, []byte("data: "))
 			if len(jsonData) > 0 && jsonData[0] == '{' {
 				rewritten := rw.rewriteStreamEvent(jsonData)
-				out = append(out, append([]byte("data: "), rewritten...))
+				if rewritten != nil {
+					out = append(out, append([]byte("data: "), rewritten...))
+				}
 				i++
 				continue
 			}
@@ -296,9 +302,13 @@ func (rw *ResponseRewriter) rewriteStreamChunk(chunk []byte) []byte {
 
 // rewriteStreamEvent processes a single JSON event in the SSE stream.
 // It rewrites model names and ensures signature fields exist.
-// Unlike rewriteModelInResponse, it does NOT suppress thinking blocks
-// in streaming mode - they are passed through with signature injection.
 func (rw *ResponseRewriter) rewriteStreamEvent(data []byte) []byte {
+	// Suppress thinking blocks before any other processing.
+	data = rw.suppressAmpThinking(data)
+	if len(data) == 0 {
+		return nil
+	}
+
 	// Inject empty signature where needed
 	data = ensureAmpSignature(data)
 

internal/api/modules/amp/response_rewriter_test.go

@@ -101,7 +101,7 @@ func TestRewriteStreamChunk_MessageModel(t *testing.T) {
 }
 
 func TestRewriteStreamChunk_SuppressesThinkingContentBlockFrames(t *testing.T) {
-	rw := &ResponseRewriter{}
+	rw := &ResponseRewriter{suppressedContentBlock: make(map[int]struct{})}
 
 	chunk := []byte("event: content_block_start\ndata: {\"type\":\"content_block_start\",\"index\":0,\"content_block\":{\"type\":\"thinking\",\"thinking\":\"\"}}\n\nevent: content_block_delta\ndata: {\"type\":\"content_block_delta\",\"index\":0,\"delta\":{\"type\":\"thinking_delta\",\"thinking\":\"abc\"}}\n\nevent: content_block_stop\ndata: {\"type\":\"content_block_stop\",\"index\":0}\n\nevent: content_block_start\ndata: {\"type\":\"content_block_start\",\"index\":1,\"content_block\":{\"type\":\"tool_use\",\"name\":\"bash\",\"input\":{}}}\n\n")
 	result := rw.rewriteStreamChunk(chunk)