utsushi.studio

Utsushi.

写し — Legacy, remastered.

Your legacy systems, understood by AI, regenerated as modern microservices.

The premise

AI doesn't patch your legacy.
It rewrites it.

Most migration frameworks assume rewriting is expensive. So they wrap, proxy, and strangle — leaving you with two systems to maintain instead of one.

Utsushi takes the opposite bet: AI can read, understand, and regenerate your entire system into a clean, modern, opinionated microservices stack. No cohabitation. No dual-run. Big-bang, assisted by AI.

The system

Four instruments, one craft.

Program

Utsushi

The whole — a faithful reproduction through deep understanding. The AI reads your legacy and regenerates it.

Target Stack

Kumiki

Interlocking pieces, no nails. Modular microservices that fit together through contracts — OpenAPI, AsyncAPI, MCP.

Migration Robot

Mitate

Reinterpretation — reading one thing in another form. Six AI agents analyze, plan, generate, validate.

Orchestrator

Shidō

Guidance. Coordinates agents, manages human gates, handles checkpointing. A coach, not an executor.

Non-negotiable

Opinionated by design.

Open source, always

No paid product in production. Every component is OSS with a clear license. No exceptions.

One stack, imposed

One server language, one framework, one ORM, one frontend runtime. Deviations require an architecture decision record.

Standards, nothing else

If the legacy uses a standardized concept — CMIS, BPMN, OIDC — we enforce the standard. No proprietary shortcuts.

KISS

Every tool must justify its existence. When in doubt, remove it. Fewer moving parts, fewer failures.

AI-native migration

No Strangler Fig. No incremental crawl. The AI reads the whole, then regenerates the whole. Big-bang, or nothing.

Tenant-ready

Multitenant from day one. The client can modify the application for themselves — BPMN workflows, custom extensions, private tenant.

Kumiki stack

What gets built.

Seven architectural layers. Ten enforced patterns. Every service is a Self-Contained Service — backend, MCP, UI, BPMN templates, OPA policies, shipped as one bundle.

Python 3.12 FastAPI Pydantic v2 SQLAlchemy async Redpanda Debezium CDC Lit Web Components Apache APISIX Keycloak OPA Flowable BPMN LangGraph SeaweedFS Crossplane PostgreSQL

Building in the open

First prototype
in progress.

Architecture defined. 15 decisions recorded. Stack validated on paper. POC underway.