Race condition in concurrent hooks corrupts mind.mv2 (Invalid sketch track magic)

[rafaelcalleja]

Summary

• claude-brain runs multiple hooks in separate processes (PostToolUse, Stop, Task agents).
• Concurrent open/write against the same .claude/mind.mv2 causes transient "Invalid sketch track magic" and "no valid commit footer".
• Mind.open() treats "Invalid" as corruption and recreates the file, which drops frames even when backups are valid.

Environment

• claude-brain 1.0.8
• @memvid/sdk 2.0.146
• Node >= 18
• Observed on Linux (repro likely on any OS with concurrent processes)

Steps to reproduce

In repo root, run this script:

npm install
npm run build
node --input-type=module - <<'EOF'
  import { Mind } from './dist/index.js';
  import { mkdtempSync, rmSync } from 'node:fs';
  import { join } from 'node:path';
  import { tmpdir } from 'node:os';

  const dir = mkdtempSync(join(tmpdir(), 'claude-brain-race-'));
  const memoryPath = join(dir, 'mind.mv2');
  const writes = 20;

  async function writeOnce(i) {
    const mind = await Mind.open({ memoryPath, debug: false });
    await mind.remember({
      type: 'discovery',
      summary: `s${i}`,
      content: `c${i}`,
    });
  }

  Promise.allSettled(Array.from({ length: writes }, (_, i) => writeOnce(i)))
    .then((results) => {
      const failed = results.filter(r => r.status === 'rejected');
      console.log('failed', failed.length);
    })
    .finally(() => rmSync(dir, { recursive: true, force: true }));
EOF

Expected

• All writes succeed; no backups; no "Invalid sketch track magic".

Actual

• Frequent Invalid sketch track magic or no valid commit footer found.
• Mind.open() recreates the file, dropping frames.

Analysis

• This looks like a race: a reader sees an in-flight write, throws "Invalid", and the caller treats it as corruption.
• Since hooks run in parallel processes, we need cross-process serialization around open+write.

Proposed fix

• Use a file lock around Mind.open() and all memvid operations (open, put, read).
• This prevents transient "Invalid" and data loss.