Seven stages between your prompt and a working app.
VULK isn't a single LLM call. It's a pipeline that understands, plans, routes, generates, validates, repairs, previews and publishes — with a model picked for each stage and a repair loop when a file fails.
- 01
Your chosen model
Understand the prompt and plan the app
Your chosen model reads the request in one typed pass: which surface you want — web app, Flutter mobile app, Shopify theme, marketing site, internal tool — and what the app needs. The plan lists features, routes, data model and acceptance criteria. A wrong surface is the most expensive failure, so nothing is generated before the plan exists.
- 02
Router (deterministic)
Route models per phase
Your chosen model writes the code. Auto applies VULK's model policy: Claude Opus 5.5 on paid plans, Claude Fable 5.1 for 3D. Narrative site plans and the file picks for an edit go to Claude Sonnet 5.5.
- 03
Generator (per-phase model)
Generate the code
VULK generates the files the plan defines, checks each one and records the accepted files. Changes stay within the planned project, and accepted work remains available for later edits and recovery.
- 04
Validator (esbuild / Dart analysis)
Validate every file
Each file is bundled with esbuild as soon as it lands, so a syntax or import error is caught before the preview boots. Flutter projects go through Dart analysis. Failures route into the repairer; passes go straight to preview.
- 05
Repairer (same writer)
Repair the failures
When a file fails, the repairer reads the actual error output and edits the file that failed. It loops until green or until the repair budget ends; accepted files are never touched.
- 06
Boot the microVM preview
Your web preview runs in an isolated Firecracker microVM with Node and Vite. Flutter previews come from VULK's own build service as a compiled web build.
- 07
Publish where it lives
Publish to a live URL — the frontend is built inside the microVM and served through Cloudflare — or export the code and push it to GitHub. Flutter builds Android APK and AAB, with signing handled inside VULK.
Which model runs which stage.
Routing follows explicit policies for the task, the plan and the model you choose. The table shows today's defaults.
| Stage | Model | Why |
|---|---|---|
| Understanding and planning | Your chosen model; Claude Sonnet 5.5 for narrative site plans | Reads the request and writes the plan before any code |
| Generation (web) | Your chosen model (Auto: Claude Opus 5.5) | Tightest output rules |
| Generation (mobile) | Your chosen model (Auto: Claude Opus 5.5) | Widget-tree correctness over brevity |
| Generation (3D) | Your chosen model (Auto: Claude Fable 5.1, one pass) | Demands correct geometry and shaders |
| Edit (surgical) | Claude Sonnet 5.5 picks the files; your chosen model writes | Smaller diff window, must keep the file alive |
| Repair | Targeted calls on the same writer | Reads compile errors as input |
What happens when generation goes wrong.
Most AI app builders stream code, hand it back, and hope. VULK assumes a first generation can fail and treats recovery as a step of its own.
- Bundle every file first. Each generated file is bundled with esbuild as it lands. Cheaper than a full build, and it catches syntax and import errors before the preview boots.
- Build with the real toolchain. Publishing runs the project's own build. Flutter goes through Dart analysis and a compiled web build, and a rejected analysis goes back into the repair flow.
- Capture the error verbatim. The repairer reads the actual compiler output, not a paraphrased summary.
- Surgical edit. The repair flow uses the validation error to correct the file that failed. Files that already passed are kept as they are.
- Loop until green or until the budget ends. Repair has a bounded budget. If a file still fails, VULK reports the diagnostic, keeps the accepted files and lets you retry the interrupted generation.
Want to feel it?
The fastest way to understand the pipeline is to watch it run. Start on a paid plan — full plan credits, cancel anytime.
Last reviewed: November 4, 2026