Turso is an in-process SQL database written in Rust that is compatible with SQLite and also accepts PostgreSQL syntax through an experimental frontend. It is for applications and organizations that need an embeddable database engine with support for multiple languages, platforms, and database features. The catalogue entries are skills and instructions for working with Turso.
Borrowing it
Nothing to install: this file belongs to tursodatabase/turso. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/tursodatabase/turso/main/.claude/skills/mvcc/SKILL.mdgit clone --depth 1 https://github.com/tursodatabase/tursoWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/tursodatabase/turso/mvcc)<a href="https://agentmods.dev/skills/tursodatabase/turso/mvcc"><img src="https://agentmods.dev/badge/skills/tursodatabase/turso/mvcc.svg" alt="Measured on agentmods" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to medium
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- medium Rogue Agent · line 54 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00017 | $0.00692 |
| Opus 5 | $0.00009 | $0.00346 |
| Sonnet 5 | $0.00003 | $0.00138 |
| Haiku 4.5 | $0.00002 | $0.00069 |
Grade A, and why
mvcc scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MVCC Guide (Experimental)
Multi-Version Concurrency Control. Work in progress, not production-ready.
CRITICAL: Ignore MVCC when debugging unless the bug is MVCC-specific.
Enabling MVCC
PRAGMA journal_mode = 'mvcc';
Runtime configuration, not a compile-time feature flag. Per-database setting.
How It Works
Standard WAL: single version per page, readers see snapshot at read mark time.
MVCC: multiple row versions, snapshot isolation. Each transaction sees consistent snapshot at begin time.
Key Differences from WAL
| Aspect | WAL | MVCC |
|---|---|---|
| Write granularity | Every commit writes full pages | Affected rows only |
| Readers/Writers | Don't block each other | Don't block each other |
| Persistence | .db-wal |
.db-log (logical log) |
| Isolation | Snapshot (page-level) | Snapshot (row-level) |
Versioning
Each row version tracks:
begin- timestamp when visibleend- timestamp when deleted/replacedbtree_resident- existed before MVCC enabled
Architecture
Database
└─ mv_store: MvStore
├─ rows: SkipMap<RowID, Vec<RowVersion>>
├─ txs: SkipMap<TxID, Transaction>
├─ Storage (.db-log file)
└─ CheckpointStateMachine
Per-connection: mv_tx tracks current MVCC transaction.
Shared: MvStore with lock-free crossbeam_skiplist structures.
Key Files
core/mvcc/mod.rs- Module overviewcore/mvcc/database/mod.rs- Main implementation (~3000 lines)core/mvcc/cursor.rs- Merged MVCC + B-tree cursorcore/mvcc/persistent_storage/logical_log.rs- Disk formatcore/mvcc/database/checkpoint_state_machine.rs- Checkpoint logic
Checkpointing
Flushes row versions to B-tree periodically.
PRAGMA mvcc_checkpoint_threshold = <pages>;
Process: acquire lock → begin pager txn → write rows → commit → truncate log → fsync → release.
Current Limitations
Not implemented:
- Garbage collection (old versions accumulate)
- Recovery from logical log on restart
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 8d ago First seen · 107 lines · 17 tokens per session scan A 5abdeb34cb08
mvcc is a skill published in the GitHub repository tursodatabase/turso (24,201 stars, last pushed today), licensed MIT. It adds 17 tokens to every session and 692 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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