open-fava

open-fava is a skill for Claude Code from cynco-labs/ai-accounting-skills. It costs 30 tokens per session (378 once invoked), scanned A, original, MIT.

A way to open a Beancount ledger in Fava, a local web interface for browsing accounting books and viewing reports.

In plain words
What is it for?
Validating the ledger, starting Fava on a local address, and viewing income statements, balance sheets, account trees, and journal entries.
Why use it?
It lets users inspect the exported ledger in a browser while keeping client financial data on the local computer.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the accounting-engagement plugin — 45 skills shipped together

Good fit Validating the ledger, starting Fava on a local address, and viewing income statements, balance sheets, account trees, and journal entries.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cynco-labs/ai-accounting-skills/open-fava
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add cynco-labs/ai-accounting-skills --skill open-fava
Clone the repo
git clone --depth 1 https://github.com/cynco-labs/ai-accounting-skills

Made for: Claude Code.

Or install accounting-engagement, the plugin that ships this one along with the rest of its 45 skills.

Wrote 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.

agentmods badge for open-fava

README.md
[![agentmods](https://agentmods.dev/badge/skills/cynco-labs/ai-accounting-skills/open-fava/github.svg)](https://agentmods.dev/skills/cynco-labs/ai-accounting-skills/open-fava)
Your own site
<a href="https://agentmods.dev/skills/cynco-labs/ai-accounting-skills/open-fava"><img src="https://agentmods.dev/badge/skills/cynco-labs/ai-accounting-skills/open-fava/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.

agentmods 80×15 button for open-fava

Your own site · 80×15
<a href="https://agentmods.dev/skills/cynco-labs/ai-accounting-skills/open-fava"><img src="https://agentmods.dev/badge/skills/cynco-labs/ai-accounting-skills/open-fava.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 378 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00030 $0.00378
Opus 5 $0.00015 $0.00189
Sonnet 5 $0.00006 $0.00076
Haiku 4.5 $0.00003 $0.00038

Measured 12d ago against content hash cd4136616830, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

open-fava 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 12d 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.

accounting-engagement/skills/open-fava/SKILL.md · 60 lines

What it actually says

/open-fava

Purpose

Fava is the impressive UI on top of Beancount — local browser, not Excel.

ledger/main.beancount → fava → http://127.0.0.1:5000

Preconditions

  1. Ledger exists (export-beancount first if not)
  2. bean-check PASS (run validate skill)
  3. fava installed: pip install fava beancount

Command

scripts/run_fava.sh path/to/main.beancount
# custom port
scripts/run_fava.sh path/to/main.beancount --port 5001

Or:

fava --host 127.0.0.1 --port 5000 path/to/main.beancount

Agent behavior

  1. Validate ledger first
  2. Start Fava in background if the host supports long-running processes
  3. Tell the user the URL: http://127.0.0.1:5000
  4. Default bind localhost only — do not expose 0.0.0.0 unless user asks
  5. If fava missing: print install one-liner; do not pretend UI is open

What to show the user

  • Income Statement / Balance Sheet in Fava
  • Account tree
  • Journal entries from export

Completion

Done when: bean-check PASS, Fava started (or install instructions), user given localhost URL.

Security

Client financial data stays local. No public tunnel unless explicitly requested.

Changes

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.

  1. 12d ago First seen · 60 lines · 30 tokens per session scan A cd4136616830

Subscribe to this mod's changes

open-fava is a skill published in the GitHub repository cynco-labs/ai-accounting-skills (3 stars, last pushed 2mo ago), licensed MIT. It adds 30 tokens to every session and 378 once invoked, about $0.0002 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 2026-08-31.

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