feat: implement stability fixes and enhance error handling

src/lib/antigravity/thinking-utils.ts

@@ -0,0 +1,116 @@
+/**
+ * Thinking Block Utilities
+ * Handles validation and graceful degradation of thinking blocks
+ *
+ * Problem: Invalid signatures cause thinking blocks to be dropped, losing content
+ * Solution: Validate and convert invalid blocks to text instead of dropping
+ */
+
+/** Minimum length for a valid thought signature */
+const MIN_SIGNATURE_LENGTH = 10;
+
+export interface ThinkingBlock {
+  type: 'thinking';
+  thinking: string;
+  signature?: string;
+}
+
+export interface TextBlock {
+  type: 'text';
+  text: string;
+}
+
+export type ContentBlock = ThinkingBlock | TextBlock | { type: string; [key: string]: any };
+
+/**
+ * Check if a thinking block has a valid signature
+ *
+ * Rules:
+ * - Empty thinking + any signature = valid (trailing signature case)
+ * - Non-empty thinking + signature >= MIN_SIGNATURE_LENGTH = valid
+ * - Non-empty thinking + no/short signature = invalid
+ * - Non-thinking blocks = always valid
+ *
+ * @param block - Content block to validate
+ * @returns true if block is valid or not a thinking block
+ */
+export function hasValidSignature(block: ContentBlock): boolean {
+  if (block.type !== 'thinking') {
+    return true; // Non-thinking blocks are always valid
+  }
+
+  const thinkingBlock = block as ThinkingBlock;
+
+  // Empty thinking + any signature = valid (trailing signature)
+  if (!thinkingBlock.thinking || thinkingBlock.thinking.length === 0) {
+    return (
+      thinkingBlock.signature !== undefined &&
+      thinkingBlock.signature !== null &&
+      thinkingBlock.signature.length >= MIN_SIGNATURE_LENGTH
+    );
+  }
+
+  // Non-empty thinking needs a long enough signature
+  return (
+    thinkingBlock.signature !== undefined &&
+    thinkingBlock.signature !== null &&
+    thinkingBlock.signature.length >= MIN_SIGNATURE_LENGTH
+  );
+}
+
+/**
+ * Gracefully degrade an invalid thinking block
+ *
+ * - Valid blocks: return as-is
+ * - Invalid with content: convert to text block
+ * - Invalid without content: return null (should be dropped)
+ *
+ * @param block - Content block to process
+ * @returns Processed block or null if should be dropped
+ */
+export function gracefulDegradeThinking(block: ContentBlock): ContentBlock | null {
+  if (block.type !== 'thinking') {
+    return block;
+  }
+
+  const thinkingBlock = block as ThinkingBlock;
+
+  if (hasValidSignature(block)) {
+    return block;
+  }
+
+  // Invalid signature - check if we have content to preserve
+  if (thinkingBlock.thinking && thinkingBlock.thinking.length > 0) {
+    // Convert to text block to preserve content
+    console.info(
+      `[Thinking-Utils] Converting invalid thinking block to text. Content length: ${thinkingBlock.thinking.length}`,
+    );
+    return {
+      type: 'text',
+      text: thinkingBlock.thinking,
+    };
+  }
+
+  // Empty content + invalid signature = drop
+  console.debug('[Thinking-Utils] Dropping empty thinking block with invalid signature');
+  return null;
+}
+
+/**
+ * Process an array of content blocks, applying graceful degradation
+ *
+ * @param blocks - Array of content blocks
+ * @returns Processed array with invalid thinking blocks handled
+ */
+export function processThinkingBlocks(blocks: ContentBlock[]): ContentBlock[] {
+  const result: ContentBlock[] = [];
+
+  for (const block of blocks) {
+    const processed = gracefulDegradeThinking(block);
+    if (processed !== null) {
+      result.push(processed);
+    }
+  }
+
+  return result;
+}