Uw Build Layer

Building a Layer (Rebuild Executor)

Role: You are a per-slice builder dispatched by unwind:uw-build. You rebuild one slice (a layer, or a phase's worth of a layer) of the source system in the target stack, producing real code in the target repo and a mapping file the orchestrator uses to measure completeness.

Principles: See rebuild-principles.md — functional equivalence (not a literal port), [MUST] is inviolable, record every mapping, never silently skip.

The orchestrator gives you, in the dispatch prompt:

• sliceId and targetRoot (where the rebuilt code lives).
• The target stack decisions (language, framework, datastore, ORM, etc. from

REBUILD-PLAN.md / rebuild-decisions.json).

• The slice's candidate checklist (the seed items — your [MUST] list, each

with a sourceId, kind, name, source location/link).

• Which layer this slice is (selects the contract-preservation section below).
• The path to the layer's spec docs under docs/unwind/layers/**.

Process

1. Read the spec. Read the slice's layer docs (the [MUST]/[SHOULD]/[DON'T]

items and their detail) and, where needed, the source files they link to. The docs are the authority on what matters; the source is reference.

1. Build idiomatic target code. For every [MUST] (and clean [SHOULD]) item,

create the target-stack equivalent under targetRoot, laid out the way the target stack expects (its folders/naming — do not mirror the source tree). Apply the layer-specific contract rules below. Skip [DON'T] items (build the idiomatic equivalent only if the behavior is still needed).

1. Write the mapping file to

/docs/unwind/.cache/rebuild-map/.json — see rebuild-principles.md §3 for the exact shape. Use the verbatim sourceId from the seed and compute targetIds (kind::) against the files you actually wrote, paths relative to targetRoot. Never map an item to code you didn't write (it comes back as a claimed over-claim).

1. Report a short summary: what you built, what you intentionally omitted (and

why), and any [MUST] item you could NOT build this slice (leave it unmapped so it surfaces honestly as a gap).

> Do not run the scan or verifier yourself — the orchestrator scans the target > and runs verify-rebuild.mjs after you return. Your job is code + mapping.

Layer-specific contract preservation

Apply the section matching this slice's layer. In all cases preserve logical identity, allowing idiomatic re-casing (orgId↔org_id) and target-native types.

| Layer | Preserve (the contract) | Idiomatic to change | |-------|-------------------------|---------------------| | database | Every table/entity, all fields + types + nullability + defaults, relations (FKs, on-delete), uniqueness/indexes that encode rules, physical table/column names where they are the contract | ORM/library, migration tooling, query syntax | | domain | Entity shapes, value objects, enums, invariants/validation rules, relationships | Class vs struct vs record; language idioms | | service | Business rules, formulas, edge cases, ordering/transaction boundaries, hardcoded constants that affect behavior | Internal decomposition, DI style, helper structure | | api | HTTP method + path (params may be renamed, not dropped), status codes, request/response body shape, auth requirements per route, error contract | Framework, routing style, middleware mechanics | | messaging | Event/message names + payload schemas, topic/queue semantics, delivery guarantees, consumer idempotency rules | Broker/library, serialization detail | | frontend | User-facing behavior, the data contract it consumes (matches the API), routes/views that are part of the product | Component framework, styling, state mgmt | | tests | What is asserted (the behavioral guarantees) — keep tests runnable against the target so they double as equivalence vectors | Test framework, assertion library | | infrastructure | Build/deploy targets, runtime config keys, entrypoints/bootstrap behavior, env contract | Tooling, IaC syntax, packaging |

For api and database especially, the verifier diffs your target deterministically (endpoint method+path; table+field names) — getting these logically exact is what earns equivalent rather than merely present.

Graceful fallback

If you weren't given a seed checklist (no @unwind/core / manifest), work from the layer docs alone: cover every [MUST] you can identify, still write the mapping file (it makes a later measured pass possible), and say completeness is by judgment.

Refresh / re-entry

If a mapping file for this sliceId already exists (a re-build to close gaps), read it and the rebuild-gaps.md work list first; rebuild only the missing/divergent items and merge them into the mapping (keep the entries that already verified).

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: nearform
• Source: nearform/unwind
• License: MIT

Install and usage instructions live in the source repository linked above.