Summary

This PR fixes two performance regressions introduced in PRs #50 and #53 that caused noticeable lag when opening transcripts and performing session searches in local mode.

Problem 1 — Transcript loading blocked by readAgentConfigs (introduced in #50)

Symptom: Clicking a transcript would hang with a loading spinner for a noticeable delay before anything rendered. This was most pronounced on macOS due to filesystem security checks on first directory access.

Root cause: fetchSessionDetail in sessionDetailSlice.ts awaited api.readAgentConfigs(projectRoot) on the critical render path — nothing could render until the IPC round-trip to read .claude/agents/ completed. Additionally, the project-level cache used a single module-level string, so switching between two projects triggered a new filesystem read on every switch.

Fix: Made the call fire-and-forget. The transcript now renders immediately; subagent type color badges update asynchronously once configs arrive. The cache key is set optimistically before the async call to prevent duplicate in-flight requests during rapid navigation.

// Before — blocks rendering
const configs = await api.readAgentConfigs(projectRoot);
if (requestGeneration !== sessionDetailFetchGeneration) return;
agentConfigsCachedForProject = projectRoot;
set({ agentConfigs: configs });

// After — non-blocking
agentConfigsCachedForProject = projectRoot; // optimistic, prevents duplicate fetches
api.readAgentConfigs(projectRoot)
  .then((configs) => { set({ agentConfigs: configs }); })
  .catch((err) => { logger.error(...); agentConfigsCachedForProject = ''; });

Problem 2 — Redundant stat() per session file on every search (introduced in #53)

Symptom: Session search felt slower than expected in local mode.

Root cause: SearchTextCache requires mtimeMs per session file for cache invalidation. LocalFileSystemProvider.readdir() returned FsDirent entries without mtimeMs (Node's readdir with withFileTypes doesn't include stat info). The new SessionSearcher.searchSessions() has a fallback — await fsProvider.stat(filePath) — which triggered for every session file on every search in local mode, adding N extra filesystem round-trips.

Fix: LocalFileSystemProvider.readdir() now stats all entries concurrently during the readdir call, populating mtimeMs on every returned entry. The stat fallback in SessionSearcher is never triggered for local mode.

// Before — mtimeMs always undefined in local mode → stat() called per file at search time
return entries.map((entry) => ({
  name: entry.name,
  isFile: () => entry.isFile(),
  isDirectory: () => entry.isDirectory(),
}));

// After — mtimeMs populated upfront via concurrent stats
return Promise.all(
  entries.map(async (entry) => {
    let mtimeMs: number | undefined;
    try {
      const stat = await fs.promises.stat(`${dirPath}/${entry.name}`);
      mtimeMs = stat.mtimeMs;
    } catch { /* ignore */ }
    return { name: entry.name, mtimeMs, isFile: ..., isDirectory: ... };
  })
);

Files Changed

Test Plan

• Open the app and click through several projects — session lists should load without delay
• Click a transcript — content should render immediately (no hang before the loading spinner resolves)
• Switch between two different projects and open a transcript in each — no regression on second project
• Run a session search — results should return without noticeable extra delay in local mode
• Subagent color badges still render correctly (may appear briefly without color, then update)

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