preview

A command that starts a local web server for the current milestone's prototype files. Localhost means the preview is served on the developer's own computer.

In plain words
What is it for?
Use it to preview milestone designs locally, choose a port, and optionally open the preview automatically.
Why use it?
It lets you inspect the current prototype in a browser without publishing it or serving it publicly.

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/benrben/mpga/preview
Clone the repo
git clone --depth 1 https://github.com/benrben/MPGA
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 114 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 $0.00000 $0.00114
Opus 5 $0.00000 $0.00057
Sonnet 5 $0.00000 $0.00023
Haiku 4.5 $0.00000 $0.00011

Measured 2d ago against content hash d95fb1b4d605, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

preview 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.

mpga-plugin/commands/preview.md · 17 lines

What it actually says

/mpga:preview

Serve the current milestone prototype locally. Localhost only. Safe. Fast. Tremendous.

Steps

  1. Run mpga preview
  2. Bind to 127.0.0.1:8420 by default
  3. Serve files from MPGA/milestones/<current>/design/prototypes/
  4. Optionally pass --open to open the browser automatically

Usage

/mpga:preview
/mpga:preview --port 8421 --open
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 · 17 lines · 0 tokens per session scan A d95fb1b4d605

Subscribe to this mod's changes

preview is a command published in the GitHub repository benrben/MPGA (5 stars, last pushed 4mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 114 tokens. 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.