fix: improve error handling and logging in summary and transcript processing

- Enhanced error handling in summary generation by using fallback messages for missing assistant messages.
- Updated the `buildSummaryPrompt` function to streamline the retrieval of the last assistant message.
- Improved the `extractLastMessage` function to log errors when transcript files are missing or empty, and to ensure proper handling of messages without content.
- Added checks to ensure that messages of the specified role are found in the transcript, with appropriate logging for missing messages.
- Refactored the logging mechanism to provide clearer insights into processing failures and successes.

src/sdk/prompts.ts

@@ -177,10 +177,10 @@ export function buildObservationPrompt(obs: Observation): string {
  * Build prompt to generate progress summary
  */
 export function buildSummaryPrompt(session: SDKSession): string {
-  const lastAssistantMessage = happy_path_error__with_fallback(
+  const lastAssistantMessage = session.last_assistant_message || happy_path_error__with_fallback(
     'Missing last_assistant_message in session for summary prompt',
     session,
-    session.last_assistant_message || ''
+    ''
   );
 
   return `PROGRESS SUMMARY CHECKPOINT

src/shared/transcript-parser.ts

@@ -1,5 +1,6 @@
 import { readFileSync, existsSync } from 'fs';
 import { logger } from '../utils/logger.js';
+import { happy_path_error__with_fallback } from '../utils/silent-debug.js';
 
 /**
  * Extract last message of specified role from transcript JSONL file
@@ -13,42 +14,73 @@ export function extractLastMessage(
   stripSystemReminders: boolean = false
 ): string {
   if (!transcriptPath || !existsSync(transcriptPath)) {
+    happy_path_error__with_fallback(
+      'Transcript path missing or file does not exist',
+      { transcriptPath, role }
+    );
     return '';
   }
 
   try {
     const content = readFileSync(transcriptPath, 'utf-8').trim();
-    if (!content) return '';
+    if (!content) {
+      happy_path_error__with_fallback(
+        'Transcript file exists but is empty',
+        { transcriptPath, role }
+      );
+      return '';
+    }
 
     const lines = content.split('\n');
+    let foundMatchingRole = false;
 
     for (let i = lines.length - 1; i >= 0; i--) {
       try {
         const line = JSON.parse(lines[i]);
-        if (line.type === role && line.message?.content) {
-          let text = '';
-          const msgContent = line.message.content;
+        if (line.type === role) {
+          foundMatchingRole = true;
 
-          if (typeof msgContent === 'string') {
-            text = msgContent;
-          } else if (Array.isArray(msgContent)) {
-            text = msgContent
-              .filter((c: any) => c.type === 'text')
-              .map((c: any) => c.text)
-              .join('\n');
+          if (line.message?.content) {
+            let text = '';
+            const msgContent = line.message.content;
+
+            if (typeof msgContent === 'string') {
+              text = msgContent;
+            } else if (Array.isArray(msgContent)) {
+              text = msgContent
+                .filter((c: any) => c.type === 'text')
+                .map((c: any) => c.text)
+                .join('\n');
+            }
+
+            if (stripSystemReminders) {
+              text = text.replace(/<system-reminder>[\s\S]*?<\/system-reminder>/g, '');
+              text = text.replace(/\n{3,}/g, '\n\n').trim();
+            }
+
+            // Log if we found the role but the text is empty after processing
+            if (!text || text.trim() === '') {
+              happy_path_error__with_fallback(
+                'Found message but content is empty after processing',
+                { role, transcriptPath, msgContentType: typeof msgContent, stripSystemReminders }
+              );
+            }
+
+            return text;
           }
-
-          if (stripSystemReminders) {
-            text = text.replace(/<system-reminder>[\s\S]*?<\/system-reminder>/g, '');
-            text = text.replace(/\n{3,}/g, '\n\n').trim();
-          }
-
-          return text;
         }
       } catch {
         continue;
       }
     }
+
+    // If we searched the whole transcript and didn't find any message of this role
+    if (!foundMatchingRole) {
+      happy_path_error__with_fallback(
+        'No message found for role in transcript',
+        { role, transcriptPath, totalLines: lines.length }
+      );
+    }
   } catch (error) {
     logger.error('HOOK', 'Failed to read transcript', { transcriptPath }, error as Error);
   }