Borrowing it
Nothing to install: this file belongs to wbrown/janus-datalog. 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/wbrown/janus-datalog/main/.claude/skills/datalog/SKILL.mdgit clone --depth 1 https://github.com/wbrown/janus-datalogWrote 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/wbrown/janus-datalog/datalog)<a href="https://agentmods.dev/skills/wbrown/janus-datalog/datalog"><img src="https://agentmods.dev/badge/skills/wbrown/janus-datalog/datalog/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/wbrown/janus-datalog/datalog"><img src="https://agentmods.dev/badge/skills/wbrown/janus-datalog/datalog.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00167 | $0.07354 |
| Opus 5.5 | $0.00067 | $0.02942 |
| Sonnet 5.5 | $0.00033 | $0.01471 |
| Haiku 4.5 | $0.00017 | $0.00735 |
Grade A, and why
datalog 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 2d 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 — 623 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Datalog Query
Query janus-datalog databases for debugging and data exploration.
The user will provide a database path — a BadgerDB directory, an .edn dump, or a .jdzl (binary) dump — and describe what they want to know. Use the datalog CLI to run queries against the database. A path ending in .edn or .jdzl is loaded into a temporary database automatically (writes are discarded on exit).
Data Model
janus-datalog is a Datomic-style EAV (Entity-Attribute-Value) store. All data is stored as datoms: [entity attribute value tx]. There are no tables — entities are just collections of attribute-value pairs, connected by shared entity IDs.
Attributes follow a namespaced keyword convention: :namespace/name (e.g., :person/name, :order/total). This means attributes cluster by namespace, which is useful when exploring unknown databases.
Storage is CRDT-backed (Conflict-free Replicated Data Types). Every write is preserved with a unique ElementID. Attribute cardinality determines conflict resolution:
| Cardinality | Behavior | Example |
|---|---|---|
| One | Last-Writer-Wins — only the latest value is returned by default | :person/name, :person/age |
| Many | Add-Wins Set — all distinct values are returned | :person/tag, :person/role |
| Vector | RGA — ordered list with deterministic merge | :product/tags, :playlist/songs |
Because all writes are preserved, you can time-travel: db.History() returns all raw datoms (no CRDT resolution), and db.AsOf(elementID) queries CRDT-resolved state as of a specific transaction.
Tool
Binary: ~/go/bin/datalog
Install if missing:
go install github.com/wbrown/janus-datalog/cmd/datalog@latest
Invocation
-db <path> accepts a BadgerDB database directory, an .edn dump file, or a .jdzl (compressed binary) dump file.
# Run a query
~/go/bin/datalog -db <path> -query '<EDN query>'
# With input bindings (repeatable, one per :in parameter after $)
~/go/bin/datalog -db <path> -query '<EDN query with :in>' -in '<EDN value>' [-in '<EDN value>' ...]
# With performance annotations
~/go/bin/datalog -db <path> -verbose -query '<EDN query>'
# Plan without executing: the compiled algebra, every optimizer rewrite
# decision (applied or declined with the reason), and the physical plan
~/go/bin/datalog -db <path> -plan-only -query '<EDN query>'
# Export entire database to readable EDN (useful for small DBs)
~/go/bin/datalog -db <path> -export <output.edn>
# Export to compressed binary JDZL instead (smaller, faster than EDN)
~/go/bin/datalog -db <path> -export-bin <output.jdzl>
# Per-attribute statistics: cardinality, value sizes, duplication, CRDT ops
~/go/bin/datalog -db <path> -stats
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.
- 2d ago Changed · +61 lines · +4 tokens per session 111897dbb715
- 1mo ago First seen · 562 lines · 163 tokens per session scan A 257567275977
datalog is a skill published in the GitHub repository wbrown/janus-datalog (54 stars, last pushed today), licensed Apache-2.0. It adds 167 tokens to every session and 7,354 once invoked, about $0.0007 per session on Opus 5.5. 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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