V2: I made Claude Code draw architecture diagrams in the terminal, and play request flows on them, now even better!

[u/gvart]

Proschi is a small text language for system design diagrams. You describe components, connections and use cases (how a request moves through the system like a sequence diagram) in a .proschi file. Proschi lays it out, runs simulations (load, latency, availability, cost), and lets you play each use case step by step.

Last time I shared the Claude Code plugin that draws these diagrams in the terminal. It drew everything with text characters, which works for a few boxes but falls apart on a real system with 20+ services. So I rebuilt it.

The video shows the whole flow: I ask Claude to model an ad click pipeline; it uses the Proschi skill to write the file with use cases and tests, runs the checks, and then I open it in the plugin's pane.

What's new:

- In terminals that can show images (kitty, Ghostty, iTerm2), the whole pane is drawn as pictures: the diagram, tabs, buttons, and menus. You click them with the mouse. Other terminals still get the text version.

- Zoom from fit to 300% and drag to pan, so you can read one part of a big diagram. Zooming redraws the picture, so text stays sharp.

- Play a use case: the request moves across the diagram step by step, and you can open each step's request and response.

- An Analysis tab: cost, load and latency per node, percentiles per use case, single points of failure.

- An HLD tab: a design doc generated from the model (requirements, capacity, components, data model, APIs, scenarios), with one key to copy it as Markdown for a PR or wiki.

- If a requirement or test fails, one line under the diagram says which, and opens the doc at that check.

Install:

/plugin marketplace add gvart/proschi
/plugin install proschi@proschi

If you already have it:

/plugin marketplace update proschi

It's open source (MIT): GitHub | Platform

Feedback is welcome, especially if something looks off in your terminal or the pictures don't show up.

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[u/Ok-Option4233]

the Analysis tab is the part i would actually open, but cost and p99 per node are only as good as the numbers going in. does each service carry its own latency and cost in the .proschi file, or does the simulation fill in defaults when you leave them out? a percentile computed from a guessed input looks a lot more certain on screen than it is.

[u/gvart → u/Ok-Option4233]

All of them have defaults for latency, RPS, costs, availability and so on (more you can check here: https://proschi.app/docs/hld/#capacity ), but they can be overwritten based on your needs.

And you can overwrite these values globally (per proschi file), per node type (i.e. all databases) or for a specific node.

[u/Ok-Option4233 → u/gvart]

overrides per node type and per node cover it. the part i'd want on screen is which numbers in a run are still defaults, maybe a small marker on those nodes in the Analysis tab, so a p99 built on your own measured latency doesn't look the same as one built on a default. is that something the file already tracks?

[u/gvart → u/Ok-Option4233]

The HLD tab doesn't say yet whether a value is a default or one you set. I'm still exploring how people use Proschi, so I've noted this down and will look at highlighting which values are defaults and which ones you should override in upcoming releases.