Catalog Formats

Palamedes currently exposes two catalog storage formats:

PO

PO is the default because it is familiar, human-editable, and supported by the current Vite and Next loader paths. A minimal config does not need a format field:

locales: [en, de]
source-locale: en
catalogs:
  - path: src/locales/{locale}
    include: [src]

That writes src/locales/en.po and src/locales/de.po.

PO output can be configured per catalog with the nested po object: set line-breaks: "off" to disable automatic width folding. Catalog order is not configurable — Ferrocat sorts both PO and FCL catalogs by source message and then gettext context using the CLDR root collation. See Configuration for the schema and the JavaScript spellings.

One divergence is worth knowing about when catalogs move between Palamedes and gettext tooling: Ferrocat keeps a short value with embedded newlines in the compact msgid "First line\n" plus continuation-line form under both auto and off. GNU gettext and pofile commonly use a leading empty msgid "" or msgstr "" line for the same value. Set line-breaks: "off" to avoid additional width-driven folding. Both spellings parse to the same message, but the difference can show up as mechanical diffs.

FCL

FCL means Ferrocat Catalog Lines. It is a line-oriented Ferrocat catalog format that Palamedes treats as canonical generated storage. Use it when the catalog files are mostly maintained by pmds extract, merge drivers, or automation rather than hand-edited as gettext PO files.

Opt in per catalog:

locales: [en, de]
source-locale: en
catalogs:
  - path: src/locales/{locale}
    format: fcl
    include: [src]

That writes src/locales/en.fcl and src/locales/de.fcl.

FCL is not NDJSON. The older ndjson config value is intentionally rejected; use format: fcl instead.

For existing projects moving from old NDJSON catalog settings, see Migrating to Palamedes 1.0.

Runtime Loading

Catalog storage and framework module loading are related but separate:

• pmds extract, pmds audit, pmds catalog merge, and native compile APIs understand both PO and FCL through the Palamedes config.
• The current first-party Vite and Next import loaders are still .po import loaders. Keep app-facing imports on PO unless the host adapter explicitly documents FCL imports.
• pmds catalog convert can write .fcl files beside existing .po files so teams can trial FCL storage before changing config.

Converting Existing Catalogs

Convert one catalog:

pmds catalog convert src/locales/de.po --to fcl --output src/locales/de.fcl

Convert every configured PO catalog:

pmds catalog convert --config palamedes.yaml --to fcl

After conversion, update the matching catalog config to format: fcl. Config mode derives each output through the target-format resolver, so a path that already ends in .po produces .po.fcl; keep the configured path unchanged and switch only its format.

The full 1.0 migration checklist, including merge-driver cleanup and metadata shape changes, lives in Migrating to Palamedes 1.0.