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The Windows WSL job is the critical path of every CI run (589 to 752 s). Its checkout sits on the Windows drive, which WSL reaches over 9P, and writing node_modules there is what makes npm ci take about three minutes where the Linux job takes 23 s. The step now copies the tree onto the distro's ext4 filesystem before installing and building, as Microsoft's WSL guidance recommends for I/O-heavy work. The e2e job downloaded the full Chromium build (about 165 MB) on every run, but a headless run with no channel launches chromium-headless-shell and never opens it. `--only-shell` skips that download. Every tsconfig now lists the @types packages it uses (node, bun, vite/client, dom-speech-recognition) instead of relying on TypeScript auto-including everything under node_modules/@types. On TypeScript 5.9 this is a no-op: identical diagnostics across all 48 projects and byte-identical emitted .d.ts files. It is a prerequisite for TypeScript 7, which drops the auto-inclusion; with these lists the Go compiler passes all 48 projects, so that upgrade becomes a version bump once TypeDoc supports it. Two cache-based approaches were evaluated and rejected: an npm cache for the WSL job (npm ci is slow there because of 9P, not downloads, and a prefix-restored cache grows without bound) and a Playwright browser cache (Playwright's docs advise against it; the download is under 10 s). |
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| src | ||
| .gitignore | ||
| grid-cell.png | ||
| main.ts | ||
| mcp-app.html | ||
| package.json | ||
| README.md | ||
| screenshot.png | ||
| server.ts | ||
| tsconfig.json | ||
| tsconfig.server.json | ||
| vite.config.ts | ||
Example: SaaS Scenario Modeler
A React-based demo MCP App that lets users adjust SaaS business parameters and see real-time 12-month projections of revenue, costs, and profitability with comparison against pre-built scenario templates.
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MCP Client Configuration
Add to your MCP client configuration (stdio transport):
{
"mcpServers": {
"scenario-modeler": {
"command": "npx",
"args": [
"-y",
"--silent",
"--registry=https://registry.npmjs.org/",
"@modelcontextprotocol/server-scenario-modeler",
"--stdio"
]
}
}
}
Local Development
To test local modifications, use this configuration (replace ~/code/ext-apps with your clone path):
{
"mcpServers": {
"scenario-modeler": {
"command": "bash",
"args": [
"-c",
"cd ~/code/ext-apps/examples/scenario-modeler-server && npm run build >&2 && node dist/index.js --stdio"
]
}
}
}
Features
- Interactive Parameters: 5 sliders for Starting MRR, Growth Rate, Churn Rate, Gross Margin, and Fixed Costs
- 12-Month Projections: Line chart showing MRR, Gross Profit, and Net Profit over time
- Scenario Templates: 5 pre-built business strategies (Bootstrapped, VC Rocketship, Cash Cow, Turnaround, Efficient Growth)
- Template Comparison: Overlay dashed lines to compare your scenario against any template
- Summary Metrics: Key metrics including Ending MRR, Total Revenue, Total Profit, and break-even month
- Theme Support: Adapts to light/dark mode preferences
Running
-
Install dependencies:
npm install -
Build and start the server:
npm run start:http # for Streamable HTTP transport # OR npm run start:stdio # for stdio transport -
View using the
basic-hostexample or another MCP Apps-compatible host.
Architecture
Server (server.ts)
Exposes a single get-scenario-data tool that returns:
- 5 pre-built scenario templates with parameters, projections, and summaries
- Default input values for the sliders
- Optionally computes custom projections when
customInputsare provided
The tool is linked to a UI resource via _meta.ui.resourceUri.
App (src/)
- Built with React for reactive slider updates and derived state management
- Uses Chart.js for the line chart visualization
- All projection calculations run client-side for instant slider feedback
- Components:
SliderRow,MetricCard,ProjectionChart - Template comparison shown as dashed overlay lines on the chart