fynapp-modify

name	fynapp-modify
description	Modify an existing FynApp — change rendering, add/consume/author middleware, adjust exposes or dependencies. Use whenever the user asks to change, extend, fix, or add a feature to a FynApp (any app whose rollup.config imports create-fynapp). NOT for creating a new FynApp (use the create-fynapp CLI) and NOT for a kernel-wide API migration (use fynapp-migrate-kernel).

Modify an existing FynApp

FynApps are micro-frontends loaded by the fynmesh kernel. Modifying one requires understanding its code, so it's your job — there is no code-mod for it.

The contract and guide ship inside the installed create-fynapp package (paths below are node_modules/create-fynapp/...; in the fynmesh monorepo itself they are dev-tools/create-fynapp/...). Curated examples live in the FynMesh repository.

Do this

1. Read the contract first — authoritative and verifiable: node_modules/create-fynapp/agent/CONTRACT.md (FynUnit lifecycle, rollup.config.ts, consuming/providing middleware, render results, package/tsconfig shape). Fuller guide: node_modules/create-fynapp/agent/GUIDE.md.

2. Copy the closest pattern from the FynMesh examples: react-minimal, middleware-consumer, middleware-provider, vanilla.

3. Make a surgical edit. Touch only what the request needs. src/main.ts exports const main implementing FynUnit (required execute(runtime); optional initialize/shutdown). Read consumed middleware via runtime.middlewareContext.get("<name>"). There is no runtime.kernel — use globalThis.fynMeshKernel. Adding an exposed module or dependency is a trivial edit to rollup.config.ts / package.json.

4. Check — required before you call it done:

   cd <fynapp> && cfa check
   

   (builds via rollup + checks dist/fynapp-entry.js and a valid dist/fynapp.manifest.json exposing ./main; --no-build checks an existing dist/). If the app renders UI, also load it in the browser to confirm it actually renders.

Guardrails

• Match the app's existing style; don't refactor unrelated code.
• React apps import and depend on the public react/react-dom packages. Repository demos may explicitly opt into local ESM adapters; don't copy that demo-only setting into public scaffolds.
• FynModule/FynModuleRuntime are deprecated aliases; use FynUnit/FynUnitRuntime.
• If a change needs a kernel API that doesn't exist yet, stop and surface it — don't invent kernel methods.