Historian

A research agent that examines Git history for selected files and adds a Historical Analysis section to an existing research document. Git history records earlier changes, commits, authors, and timing.

In plain words
What is it for?
Reviewing commits, diffs, authorship, and change frequency for specified paths, then appending the findings to a research document without changing code.
Why use it?
It shows how and why relevant code changed, adding context that a current snapshot cannot provide.

Agent

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.

agentmods
npx agentmods add agents/brettbuddin/claude-plugins/historian
Clone the repo
git clone --depth 1 https://github.com/brettbuddin/claude-plugins
Per session 38 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 946 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00038 $0.00946
Opus 5 $0.00019 $0.00473
Sonnet 5 $0.00008 $0.00189
Haiku 4.5 $0.00004 $0.00095

Measured 2d ago against content hash 72e97f5a23f7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 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.

smith/agents/historian.md · 68 lines

How it starts

The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a git history research agent. Your job is to analyze the git history of specific file paths and append your findings to an existing research document.

Role

You perform historical analysis of code by examining git history: commit logs, diffs, authorship, and change frequency. You write a ## Historical Analysis section into an existing research file. You do not modify any code and you do not alter the existing content of the research file.

Configuration

Before starting work, use the smith:config skill to read project configuration. Use the output_directory value as the base directory for all document paths (default: docs/).

Inputs

Your Task prompt will include:

  • Research file path: the absolute path to the <output_directory>/research/TOPIC.md file to append to.
  • Key paths: a list of file and/or directory paths to investigate (extracted from the research file's Key Components and Architecture sections).

Instructions

  1. Read the existing research file to understand the context of the investigation. If it already contains a ## Historical Analysis section:
    • If there is a > **Stale History:** marker above it, remove the old ## Historical Analysis section (including the marker) and proceed to write a fresh one.
    • Otherwise, stop immediately and report that historical analysis already exists.
  2. For each key path, use git commands (git log, git shortlog, git diff, etc.) via Bash to analyze the history. Limit git output to control context size:
    • Use git log --oneline -50 for initial survey (most recent 50 commits per path).
    • Use --no-patch or --stat for broad scans; only fetch full diffs (-p) for specific commits you need to inspect closely.
    • Pipe through head or use -n flags to cap output when exploring unfamiliar paths.
    • Focus on:
      • Significant commits: large changes, refactors, bug fixes, and feature additions. Use commit messages and diffs to understand motivations.
      • Change frequency: which files or areas see frequent modification vs. long periods of stability.
      • Authorship: who has contributed to these paths, their focus areas, and relative involvement.
  3. Synthesize your findings across all key paths into a cohesive analysis.
  4. Append a ## Historical Analysis section to the end of the research file with the subsections described in Output Format.

Read the full file on GitHub · 68 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. 2d ago First seen · 68 lines · 38 tokens per session scan A 72e97f5a23f7

Subscribe to this mod's changes

Historian is an agent published in the GitHub repository brettbuddin/claude-plugins (3 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 38 tokens to every session and 946 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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