Freeze class, selector, condition and mode semantics #447

Goal and background

The current language selects intent from the complete entry and preserves authored query units and ordered wrappers. The old RC report in #444 does not establish that the current implementation has the same defect.

Parent tracker: #445
Baseline: 70444b18c8102fa7a9d811ec51ef96902573792c
Phase: 2.0 freeze

Ownership and scope

mastercss-engine, mastercss-lexer, mastercss-compiler, @master/css, and tooling

Dependencies

• Define the 2.0 freeze contract and audit baseline #446

Implementation tasks

• Freeze entry resolution for named tokens, raw properties, aliases, enums, negative values, escapes, and groups.
• Validate combinations, ordering, and diagnostics for pseudo selectors, variants, modes, media, supports, and containers. Do not infer undefined names.
• Cover flex, flex:1, flex:hover, and display:flex:hover so native values cannot be mistaken for states.
• Reference Stacked mode + breakpoint variants (e.g. @dark@sm) emit invalid media query: missing and between media features #444: reproduce mode plus breakpoint behavior using current @mode definitions, and separately verify rejection and migration of the old settings. Do not create a duplicate bug.

Acceptance criteria

• Native and Wasm execution agree for the same manifest and class.
• Valid compound conditions emit parseable CSS; invalid or unknown conditions produce consistent diagnostics.
• Old RC behavior and current behavior are recorded separately. Do not close Stacked mode + breakpoint variants (e.g. @dark@sm) emit invalid media query: missing and between media features #444 before verification.

Validation

Focused engine, lexer, and compiler tests; @master/css tests; condition ordering tests; native/Wasm parity.

Completion report

Include source and test evidence, PRs, actual commands and results, and any CSS/API/syntax/migration impact. Checks that were not run or were blocked must not be reported as passing.

Final acceptance (2026-09-28)

The compiler issue 447 matrix covers 27 matched and seven diagnostic/unmatched cases across native/Wasm compiler-engine combinations. Rust mode-plus-breakpoint coverage emits valid CSS and roundtrips its Manifest. This certifies current source behavior; the separately published RC report #444 remains open.

Merged into rust through PR #461 at 262adb809b928af7082107e1b5633d945cb7f427. The verified candidate is 16a90bdde96ef08ba4312e5d94aaf36d50048dca; removal commit 9d9817241 is preserved through integration merge e231a700e.

Final CI passes Linux package tests/lint/types (111/111 tasks), site build/CSS contract/Playground/lint/types and examples (36/36); Windows package tests (59/59 tasks, including Vite 676/676) and examples (36/36); Rust fmt/Clippy/workspace/codegen/parity; eight native targets; and Linux runtime/Next E2E. Runtime E2E passes 432 cases across Chromium, Firefox and WebKit, plus 10 Next cases.

Both deployments at this exact candidate pass page, canonical and removal-notice checks: Cloudflare and Vercel. Cloudflare health passes. Visual checks on the preceding candidate cover identical production site sources.

The dated audit preserves scoped commands and historical failures; this final result supersedes its pending CI status. The Compose integration review and site CSS review explain intentional contract changes. Site lint has 265 existing warnings and zero errors. No npm publication, package rename, version bump, lockfile change or release-workflow change is included.