feat(pierre): sanity check

internal/pierre/judge.go

@@ -88,6 +88,10 @@ If project guidelines are provided, treat them as hard rules that must be respec
 // It tries to split on file boundaries ("diff --git") first, then on hunk boundaries (@@),
 // and finally on a hard byte limit.
 func splitDiffIntoChunks(diff []byte, maxSize int) []string {
+	// Preserve the file header for each chunk when a single file's diff is split across multiple chunks.
+	// The header is the portion before the first hunk marker "@@" (including the "diff --git" line).
+	// When we need to split by hunks, we prepend this header to every resulting sub‑chunk.
+
 	if len(diff) <= maxSize {
 		return []string{string(diff)}
 	}
@@ -107,22 +111,31 @@ func splitDiffIntoChunks(diff []byte, maxSize int) []string {
 			current.Reset()
 		}
 		if len(seg) > maxSize {
-			// Split further by hunks
-			hunks := strings.Split(seg, "\n@@ ")
-			for j, h := range hunks {
-				var hseg string
-				if j == 0 {
-					// First hunk segment already contains the preceding content (including any needed newline)
-					hseg = h
-				} else {
-					// Subsequent hunks need the leading newline and "@@ " marker restored
-					hseg = "\n@@ " + h
+			// Determine if there is a hunk marker. If not, fall back to simple size‑based chunking.
+			headerEnd := strings.Index(seg, "\n@@ ")
+			if headerEnd == -1 {
+				// No hunk marker – split purely by size.
+				remaining := seg
+				for len(remaining) > maxSize {
+					chunks = append(chunks, remaining[:maxSize])
+					remaining = remaining[maxSize:]
 				}
+				current.WriteString(remaining)
+				continue
+			}
+			// Preserve the header up to the first hunk.
+			header := seg[:headerEnd+1] // include newline before "@@"
+			// Split the rest of the segment into hunks (excluding the header part).
+			hunks := strings.Split(strings.TrimPrefix(seg, header), "\n@@ ")
+			for _, h := range hunks {
+				// Reconstruct each hunk with its header and "@@ " prefix.
+				hseg := header + "@@ " + h
 				if current.Len()+len(hseg) > maxSize && current.Len() > 0 {
 					chunks = append(chunks, current.String())
 					current.Reset()
 				}
 				if len(hseg) > maxSize {
+					// If a single hunk exceeds maxSize, split it further.
 					for len(hseg) > maxSize {
 						chunks = append(chunks, hseg[:maxSize])
 						hseg = hseg[maxSize:]