ICU Semantics Proof: Source to Runtime

Palamedes preserves ICU MessageFormat semantics across every pipeline stage it controls:

source -> extraction -> macro transform -> PO catalog -> catalog compile -> runtime render

That scope is deliberate. A translation management system sits outside the Palamedes boundary, so its import and export behavior depends on the chosen product, file format, and project configuration.

Re-run the claim

pnpm proof:icu

The command uses the checked fixture under proof/icu-semantics. It does not call a hosted service or use a mocked TMS.

The fixture contains a plural nested inside both branches of a select. The proof asserts:

extraction returns the exact source ICU message and context;
the macro transform binds role and count to the generated runtime call and emits the same compiled message ID as the catalog compiler;
a PO catalog update retains the exact msgid, msgctxt, and German translation;
source and translation retain the same argument names, selector kinds, branch keys, nesting, and # substitutions;
catalog compilation emits the exact translated ICU message without missing entries or ICU errors;
the transformed fixture is imported and renders six checked combinations across both select branches and the =0, one, and other plural branches.

The script prints hashes, the normalized selector shape, and the number of runtime scenarios after all assertions pass.

The claim boundary

Safe public wording:

Palamedes keeps ICU semantics intact from source code through PO catalogs to runtime. Within the stages Palamedes controls, nested selectors are not flattened into a proprietary plural model.

Avoid claiming that every TMS preserves arbitrary ICU messages. Palamedes can provide a lossless boundary on both sides of a TMS exchange, but only the selected TMS can determine what happens during its import, editing, and export steps.

Public market snapshot

The following examples are a documentation snapshot checked on 2026-07-23, not a permanent or exhaustive ranking:

Product	Publicly documented ICU behavior
React Intl	Uses ICU Message syntax as its native message model, including `plural`, `select`, and `selectordinal`.
i18next	Uses its own interpolation format by default. ICU is available through an i18n-format plugin; i18next documents that format plugins replace its native plural, interpolation, and context behavior.
Crowdin	Documents editor support for ICU arguments, nested plurals, target-language plural categories, previews, and syntax errors.
Phrase TMS	Parses ICU for supported formats when enabled; parsing is an all-or-nothing file/template setting, and ICU messages cannot be split or joined.
Weblate	Documents ICU syntax and placeholder validation as a quality check enabled by a flag and automatically enabled for ARB and FormatJS JSON.

Direct sources, all checked 2026-07-23:

The broader research notes remain under docs/research/competitors. Re-check their dates and primary sources before promoting another comparison claim to the public site.