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Live Sync: Keep the Index Current

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Goal

Every markdown change in the brain repo is searchable within minutes, automatically, with no manual intervention.

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What the User Gets

Without this: you correct a hallucination in a brain page, but the vector DB keeps serving the old text because nobody ran modusbrain sync. Stale search results erode trust. The brain becomes unreliable. With this: edits show up in search within minutes. The vector DB stays current with the brain repo automatically. You never have to remember to run sync.

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Implementation

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Prerequisite: a reachable direct connection

ModusBrain is tuned for the Supabase Transaction pooler (port 6543): it auto-disables prepared statements there and routes engine.transaction() (migrations, DDL, sync imports) to a derived direct connection (db.<ref>.supabase.co:5432). That direct host is IPv6-only, so on an IPv4-only host, reads work but sync silently skips most pages. This is the number one cause of “sync ran but nothing happened.” Fix: make the direct connection reachable over IPv4. Either set MODUSBRAIN_DIRECT_DATABASE_URL to the Session pooler string (port 5432 on the pooler.supabase.com host, IPv4), or enable Supabase’s IPv4 add-on. Verify by running modusbrain sync and checking that the page count in modusbrain stats matches the syncable file count in the repo.

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The Primitives

Always chain sync + embed:
  • modusbrain sync --repo &lt;path&gt; — one-shot incremental sync. Detects changes via git diff, imports only what changed. For small changesets (<= 100 files), embeddings are generated inline during import.
  • modusbrain embed --stale — backfill embeddings for any chunks that don’t have them. Safety net for large syncs (>100 files) or prior --no-embed runs.
  • modusbrain sync --watch --repo &lt;path&gt; — foreground polling loop, every 60s (configurable with --interval N). Embeds inline for small changesets. Exits after 5 consecutive failures, so run under a process manager or pair with a cron fallback.
Run every 5-30 minutes. Works with any cron scheduler.
OpenClaw:
Hermes:

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Approach 2: Long-Lived Watcher

For near-instant sync (60s polling). Run under a process manager that auto-restarts on exit. Pair with a cron fallback since --watch exits on repeated failures.

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Approach 3: Git Hook / Webhook

Triggers sync on push events for instant sync (< 5s).
  • GitHub webhook: Set up the webhook to call modusbrain sync --repo /data/brain && modusbrain embed --stale. Verify X-Hub-Signature-256 against a shared secret.
  • Git post-receive hook: If the brain repo is on the same machine.

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What Gets Synced

Sync only indexes “syncable” markdown files. These are excluded by design:
  • Hidden paths (.git/, .raw/, etc.)
  • The ops/ directory
  • Meta files: README.md, index.md, schema.md, log.md

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Sync is Idempotent

Concurrent runs are safe. Two syncs on the same commit no-op because content hashes match. If both a cron and --watch fire simultaneously, no conflict.

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Tricky Spots

  1. Always chain sync + embed. Running modusbrain sync without modusbrain embed --stale leaves new chunks without embeddings. They exist in the database but are invisible to vector search. Always run both commands together. The && ensures embed only runs if sync succeeds.
  2. —watch polls, it doesn’t stream. The --watch flag polls every 60s (configurable). It is not a filesystem watcher or git hook. It exits after 5 consecutive failures, so it needs a process manager (systemd, pm2) or a cron fallback to stay alive. Don’t assume it runs forever.
  3. Webhook needs the server running. If you use a GitHub webhook for instant sync, the receiving server must be running and reachable. If the server is down when a push happens, that sync is missed. Pair webhooks with a cron fallback that catches anything the webhook missed.
  4. A single un-parseable file can’t wedge all indexing. When a file fails to import (malformed YAML frontmatter, an unquoted colon, etc.), sync holds the bookmark and tells you exactly which file broke — a fresh failure fails closed so nothing is silently dropped. But a file that fails the same way MODUSBRAIN_SYNC_AUTOSKIP_AFTER consecutive syncs (default 3, set 0 to disable) is auto-skipped so the rest of the brain keeps indexing past it. Skipped files don’t disappear: modusbrain doctor keeps warning until you fix or delete them, and fixing the file clears it on the next sync. A repository history rewrite still hard-blocks even with --skip-failed. Run modusbrain sync --skip-failed to acknowledge a known-bad set yourself.

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How to Verify

  1. Edit a file and search for the change. Edit a brain markdown file, commit, and push. Wait for the next sync cycle (cron interval or --watch poll). Run modusbrain search "&lt;text from the edit&gt;". The updated content should appear in results. If it returns old content, sync failed.
  2. Compare page count to file count. Run modusbrain stats and count the syncable markdown files in the brain repo. The page count in the database should match. If they diverge, files are being silently skipped (likely an unreachable direct connection on IPv4 — see the prerequisite above).
  3. Check embedded chunk count. In modusbrain stats, the embedded chunk count should be close to the total chunk count. A large gap means modusbrain embed --stale isn’t running after sync, leaving chunks invisible to vector search.
Part of the ModusBrain Skillpack.