perf(main): share lead session tail reads

src/main/services/team/TeamDataService.ts

@@ -3245,20 +3245,12 @@ export class TeamDataService {
     return sessionIds;
   }
 
-  private async extractLeadAssistantTextsFromJsonl(
-    jsonlPath: string,
-    leadName: string,
-    leadSessionId: string,
-    maxTexts: number
-  ): Promise<InboxMessage[]> {
-    if (maxTexts <= 0) return [];
-
+  private async readLeadSessionJsonlTailLines(jsonlPath: string): Promise<string[]> {
     const MAX_SCAN_BYTES = 8 * 1024 * 1024;
     const INITIAL_SCAN_BYTES = 256 * 1024;
 
     const rawLinesReversed: string[] = [];
     const seenRawLines = new Set<string>();
-    const seenMessageIds = new Set<string>();
     const handle = await fs.promises.open(jsonlPath, 'r');
     try {
       const stat = await handle.stat();
@@ -3289,7 +3281,17 @@ export class TeamDataService {
       await handle.close();
     }
 
-    const rawLines = rawLinesReversed.reverse();
+    return rawLinesReversed.reverse();
+  }
+
+  private async extractLeadAssistantTextsFromJsonlLines(
+    rawLines: readonly string[],
+    leadName: string,
+    leadSessionId: string,
+    maxTexts: number
+  ): Promise<InboxMessage[]> {
+    if (maxTexts <= 0) return [];
+    const seenMessageIds = new Set<string>();
     const texts: InboxMessage[] = [];
     let syntheticBuffer: {
       firstMsg: Record<string, unknown>;
@@ -3475,13 +3477,15 @@ export class TeamDataService {
     }
 
     const parse = async (): Promise<InboxMessage[]> => {
+      const rawLines = await this.readLeadSessionJsonlTailLines(jsonlPath);
       const [assistantTexts, commandResults] = await Promise.all([
-        this.extractLeadAssistantTextsFromJsonl(jsonlPath, leadName, leadSessionId, maxTexts),
+        this.extractLeadAssistantTextsFromJsonlLines(rawLines, leadName, leadSessionId, maxTexts),
         extractLeadSessionMessagesFromJsonl({
           jsonlPath,
           leadName,
           leadSessionId,
           maxMessages: maxTexts,
+          rawLines,
         }),
       ]);
       const combined = [...assistantTexts, ...commandResults];

src/main/services/team/leadSessionMessageExtractor.ts

@@ -16,6 +16,7 @@ interface LeadSessionMessageExtractorOptions {
   leadName: string;
   leadSessionId: string;
   maxMessages: number;
+  rawLines?: readonly string[];
 }
 
 function getMessageText(message: ParsedMessage): string {
@@ -98,50 +99,61 @@ export async function extractLeadSessionMessagesFromJsonl({
   leadName,
   leadSessionId,
   maxMessages,
+  rawLines,
 }: LeadSessionMessageExtractorOptions): Promise<InboxMessage[]> {
   if (maxMessages <= 0) return [];
 
   const parsedMessagesReversed: ParsedMessage[] = [];
   const seenScanKeys = new Set<string>();
-  const handle = await fs.promises.open(jsonlPath, 'r');
+  const collectLine = (rawLine: string | undefined): void => {
+    const trimmed = rawLine?.trim();
+    if (!trimmed) return;
 
-  try {
-    const stat = await handle.stat();
-    const fileSize = stat.size;
-
-    let scanBytes = Math.min(INITIAL_SCAN_BYTES, fileSize);
-    while (scanBytes <= MAX_SCAN_BYTES) {
-      const start = Math.max(0, fileSize - scanBytes);
-      const buffer = Buffer.alloc(scanBytes);
-      await handle.read(buffer, 0, scanBytes, start);
-      const chunk = buffer.toString('utf8');
-
-      const lines = chunk.split(/\r?\n/);
-      const fromIndex = start > 0 ? 1 : 0;
-
-      for (let i = lines.length - 1; i >= fromIndex; i--) {
-        const trimmed = lines[i]?.trim();
-        if (!trimmed) continue;
-
-        let parsed: ParsedMessage | null = null;
-        try {
-          parsed = parseJsonlLine(trimmed);
-        } catch {
-          parsed = null;
-        }
-        if (!parsed || parsed.isSidechain) continue;
-
-        const scanKey = buildScanKey(parsed, trimmed);
-        if (seenScanKeys.has(scanKey)) continue;
-        seenScanKeys.add(scanKey);
-        parsedMessagesReversed.push(parsed);
-      }
-
-      if (scanBytes === fileSize) break;
-      scanBytes = Math.min(fileSize, scanBytes * 2);
+    let parsed: ParsedMessage | null = null;
+    try {
+      parsed = parseJsonlLine(trimmed);
+    } catch {
+      parsed = null;
+    }
+    if (!parsed || parsed.isSidechain) return;
+
+    const scanKey = buildScanKey(parsed, trimmed);
+    if (seenScanKeys.has(scanKey)) return;
+    seenScanKeys.add(scanKey);
+    parsedMessagesReversed.push(parsed);
+  };
+
+  if (rawLines) {
+    for (let i = rawLines.length - 1; i >= 0; i--) {
+      collectLine(rawLines[i]);
+    }
+  } else {
+    const handle = await fs.promises.open(jsonlPath, 'r');
+
+    try {
+      const stat = await handle.stat();
+      const fileSize = stat.size;
+
+      let scanBytes = Math.min(INITIAL_SCAN_BYTES, fileSize);
+      while (scanBytes <= MAX_SCAN_BYTES) {
+        const start = Math.max(0, fileSize - scanBytes);
+        const buffer = Buffer.alloc(scanBytes);
+        await handle.read(buffer, 0, scanBytes, start);
+        const chunk = buffer.toString('utf8');
+
+        const lines = chunk.split(/\r?\n/);
+        const fromIndex = start > 0 ? 1 : 0;
+
+        for (let i = lines.length - 1; i >= fromIndex; i--) {
+          collectLine(lines[i]);
+        }
+
+        if (scanBytes === fileSize) break;
+        scanBytes = Math.min(fileSize, scanBytes * 2);
+      }
+    } finally {
+      await handle.close();
     }
-  } finally {
-    await handle.close();
   }
 
   const parsedMessages = parsedMessagesReversed.reverse();

test/main/services/team/leadSessionMessageExtractor.test.ts

@@ -145,4 +145,38 @@ describe('extractLeadSessionMessagesFromJsonl', () => {
       text: 'Detached output',
     });
   });
+
+  it('extracts command outputs from preloaded raw lines without reading the jsonl file', async () => {
+    const rawLines = [
+      createUserEntry(
+        'user-slash-raw',
+        '2026-03-27T12:00:00.000Z',
+        '<command-name>/cost</command-name><command-message>cost</command-message><command-args></command-args>'
+      ),
+      createUserEntry(
+        'stdout-raw',
+        '2026-03-27T12:00:01.000Z',
+        '<local-command-stdout>Total cost: $1.23</local-command-stdout>'
+      ),
+    ].map((entry) => JSON.stringify(entry));
+
+    const messages = await extractLeadSessionMessagesFromJsonl({
+      jsonlPath: path.join(os.tmpdir(), 'missing-lead-session.jsonl'),
+      leadName: 'team-lead',
+      leadSessionId: 'lead-1',
+      maxMessages: 20,
+      rawLines,
+    });
+
+    expect(messages).toHaveLength(1);
+    expect(messages[0]).toMatchObject({
+      from: 'team-lead',
+      messageKind: 'slash_command_result',
+      commandOutput: {
+        stream: 'stdout',
+        commandLabel: '/cost',
+      },
+      text: 'Total cost: $1.23',
+    });
+  });
 });