Changelog

v2.1.0 — 2026-09-15

Prompt generation — butter compile writes a Markdown system-prompt document (.prompt.md) by default.
Format cleanup — htmltree and simulator output formats removed.
Quoted HTTP methods — Endpoint method values must be quoted strings (e.g. method "POST"); bare verbs are rejected.
Formatter fixes — Consistent blank-line placement above comment and app/feature/endpoint blocks, with trailing blank lines preserved.
Windows support — Lexer handles CRLF line endings.

Canonical spec alignment — Butter targets the canonical specification language exclusively.
rules block — App-level rules use a rules block with bare quoted strings.
returns (plural) — Endpoint return mappings use returns (singular return removed).
enforce support — Enforce children under actions recognized with keyword + string scopes.
product removed — app is the only top-level root keyword.
Canonical types — string, integer, double, boolean, enum, array. Aliases removed.
IntelliSense — Completion, hover, and definitions updated.

Minimal grammar — Bare <name> <type> params, bare quoted action strings, PascalCase response headers, bare method keyword.
Removed verbosity — param, type, required, default, validate, length, action, route, response, field, listener all removed.
Endpoint route in header — endpoint Name "/path".

Selective compilation — --only and --exclude flags for targeted extraction of features and endpoints.

endpoint blocks — HTTP transport contracts with method, params, responses, actions, and returns.
response blocks — Named schemas with typed fields, supporting nested sub-fields.
return mapping — Status codes to response references or string payloads.

Sim extension — Interactive spec simulation with AI-powered code generation.
opencode provider — Free AI code generation via the opencode CLI.

Pluggable output extensions — Output formats registered via a Go interface. New formats are single-file implementations.

Semantic analysis — Catches duplicate names, type mismatches, invalid HTTP methods, and more.