historian

historian is a skill for Claude Code from faizanmohiuddin482/bullpen. It costs 184 tokens per session (1,576 once invoked), scanned A, a copy of historian, MIT.

A code-history review method for understanding why unusual code exists before deleting or refactoring it. It uses Git history, callers, linked issues, pull requests, and tests to investigate the code's purpose.

In plain words
What is it for?
Use it before removing retries, timeouts, guards, workarounds, defensive copies, special branches, or other code whose purpose is not clear.
Why use it?
A check that looks redundant may protect against a past bug or unusual production condition. Understanding its history reduces the risk of removing behavior that the system still needs.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter.

Part of the bullpen plugin — 10 skills shipped together

Good fit Use it before removing retries, timeouts, guards, workarounds, defensive copies, special branches, or other code whose purpose is not clear.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/faizanmohiuddin482/bullpen/historian
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 faizanmohiuddin482/bullpen --skill historian
Clone the repo
git clone --depth 1 https://github.com/faizanmohiuddin482/bullpen

Made for: Claude Code.

Or install bullpen, the plugin that ships this one along with the rest of its 10 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 historian

README.md
[![agentmods](https://agentmods.dev/badge/skills/faizanmohiuddin482/bullpen/historian/github.svg)](https://agentmods.dev/skills/faizanmohiuddin482/bullpen/historian)
Your own site
<a href="https://agentmods.dev/skills/faizanmohiuddin482/bullpen/historian"><img src="https://agentmods.dev/badge/skills/faizanmohiuddin482/bullpen/historian/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 historian

Your own site · 80×15
<a href="https://agentmods.dev/skills/faizanmohiuddin482/bullpen/historian"><img src="https://agentmods.dev/badge/skills/faizanmohiuddin482/bullpen/historian.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 184 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,576 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 100% copy Near-identical to another mod 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 $0.00184 $0.01576
Opus 5 $0.00092 $0.00788
Sonnet 5 $0.00037 $0.00315
Haiku 4.5 $0.00018 $0.00158

Measured 10d ago against content hash 4384fb05f943, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

historian 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 10d 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.

Origin

This is a copy

100% identical to historian — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/historian/SKILL.md · 117 lines

How it starts

The opening of the file, as written. The whole thing — 117 lines — stays where its author put it; the contents beside it link to each section on GitHub.

The Historian

You are the engineer who has been burned by his own cleanup. You once deleted a three-line hack that "did nothing," shipped the tidy diff, and spent the next outage learning what it did. Now you never rip out a fence until you know who built it and why. Old code is a message from someone who knew something you don't — usually a past engineer at 3am, sometimes you.

A confident deletion of a load-bearing hack is the worst kind of small diff: it reviews clean and it takes down prod.

When the fence goes up

Not every line has a history worth chasing. Code you wrote this session, code you can prove is dead (no references, no tests, no telemetry), a genuinely orphaned file — remove it, one line, move on. The fence goes up the moment you're about to remove or rewrite code you can't fully explain:

  • a retry, timeout, or backoff that looks excessive
  • a branch that "can never be reached"
  • a null-check, clamp, or guard with no obvious trigger
  • an ugly workaround, a magic constant, a // don't touch this
  • a sleep, a re-order, a defensive copy that seems pointless
  • a check that duplicates one you already see upstream

Obvious purpose, or provably dead → no investigation needed. YAGNI applies to archaeology too — don't blame a variable rename.

The dig

Don't trust the diff's tidiness — find out why the code is there before you touch it. The commit that added it was solving something:

  1. Blame the line. git blame / git log -S to the commit that introduced it. Read the message. Half the time it names the bug outright.
  2. Follow the thread. Commit → PR → linked issue. "Added retry for flaky payments upstream (#4821)" is the whole answer.
  3. Find the callers. grep the references, run the tests, check who actually hits this path. "Looks unused" is a hypothesis — references, tests, and telemetry are the fact.
  4. Reproduce the reason. If it guards an edge case, can you still trigger it? Remove it on a branch and run the test that should now fail. If nothing fails, ask why the test doesn't exist before you trust the silence.

Read the full file on GitHub · 117 lines

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. 10d ago First seen · 117 lines · 184 tokens per session scan A 4384fb05f943

Subscribe to this mod's changes

historian is a skill published in the GitHub repository faizanmohiuddin482/bullpen (3 stars, last pushed 1mo ago), licensed MIT. It adds 184 tokens to every session and 1,576 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to historian, differing in 0 lines, and is treated as a copy.

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