modernize-brief

A command that turns findings about an old system into a phased modernization plan for approval and execution.

In plain words
What is it for?
It reads analysis documents, recommends or uses a target technology stack, and produces a Modernization Brief covering the work to be done in stages.
Why use it?
It gathers the required assessment, architecture, and business-rule information into one plan, while exposing missing groundwork before planning begins.

Command

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 commands/anthropics/claude-plugins-official/modernize-brief
Clone the repo
git clone --depth 1 https://github.com/anthropics/claude-plugins-official
Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,135 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 $0.00016 $0.02135
Opus 5 $0.00008 $0.01068
Sonnet 5 $0.00003 $0.00427
Haiku 4.5 $0.00002 $0.00214

Measured yesterday against content hash ec151ac5d0b5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

modernize-brief 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 yesterday.

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.

plugins/code-modernization/commands/modernize-brief.md · 171 lines

How it starts

The opening of the file, as written. The whole thing — 171 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Synthesize everything in analysis/$1/ into a Modernization Brief — the single document a steering committee approves and engineering executes.

Target stack: $2 (if blank, recommend one based on the assessment findings).

Read analysis/$1/ASSESSMENT.md, analysis/$1/topology.json (plus the .mmd files alongside it — do NOT read TOPOLOGY.html, it's an interactive viewer with the data minified inside), and analysis/$1/BUSINESS_RULES.md first. If any are missing, say so and stop — they come from /modernize-assess, /modernize-map, and /modernize-extract-rules respectively. Run those first.

Two more inputs are conditional:

  • analysis/$1/PREFLIGHT.md — read it if it exists. It records two things nothing else has: the human's answers to /modernize-preflight Check 0 (scope, whether they can build and run tests locally and how long CI takes, bespoke build infrastructure, prior attempts, what is off-limits) and the Check 6 scope boundary — whether legacy/$1 is a slice of a larger codebase, and what outside it depends on code inside it. Both constrain this plan more than anything derivable from the source. Never override an answer the human gave there with a guess.
  • analysis/$1/DELTA_CATALOG.mdrequired whenever the target ($2, or your recommendation) is a newer version of the same stack. A same-stack uplift's phase order is decided by its version deltas, not by the topology alone — most of all by whether the existing test suite can even execute on the target runtime. Phasing an uplift without the catalog is planning blind; it is exactly how a test-framework migration ends up scheduled last when it must come first. If the catalog is missing, produce it before phasing — run /modernize-uplift $1 <source> $2 through its Step 3 (the delta-catalog step), or spawn the version-delta-analyst agent directly — then return here. Do not guess at the deltas.

Staleness check: compare modification times. If any input is newer than an existing MODERNIZATION_BRIEF.md, the brief is being justifiably regenerated; but if an existing brief is newer than all inputs and the user re-ran this command anyway, ask what changed. Either way, note the input timestamps in the brief's header so reviewers can see what it was built from.

The Brief

Write analysis/$1/MODERNIZATION_BRIEF.md:

Read the full file on GitHub · 171 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. yesterday First seen · 171 lines · 16 tokens per session scan A ec151ac5d0b5

Subscribe to this mod's changes

modernize-brief is a command published in the GitHub repository anthropics/claude-plugins-official (35,577 stars, last pushed 3d ago), licensed Apache-2.0. It adds 16 tokens to every session and 2,135 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.