JSON API Postinstall/Preflight/Postflight Plan

This plan tracks repeated Ruby-only install behaviours that can be expressed as structured DSL data and exposed through the JSON APIs.

Install step data is stored as an ordered array of step hashes. Ruby hashes preserve insertion order, but the outer array makes JSON ordering explicit for API consumers in any language.

The first implemented high-level DSL is named steps, exposed as post_install_steps for formulae and as preflight_steps, postflight_steps, uninstall_preflight_steps and uninstall_postflight_steps for casks. The blocks are deliberately narrow: they may only contain literal calls to the step DSL, with no wider Ruby execution and no access to the surrounding formula or cask DSL.

The initial step methods shadow common FileUtils naming where practical: mkdir/mkdir_p, touch, move/mv, move_children and symlink/ln_s/ln_sf. Formula steps default mkdir and touch paths to var, and source/target paths to prefix. Cask steps default base, source_base and target_base to staged_path.

Formula post_install_steps may temporarily coexist with post_install so tap conversions can peel supported repeated statements out of larger hooks. Runtime handling runs formula steps first and then runs post_install last for the remaining Ruby work. Cask *flight_steps still replace the matching legacy flight block because cask artifacts already carry replacement semantics and warn when both forms are present. Formula post-install steps run in the same sandboxed subprocess as the remaining post_install hook, preserving its filesystem and network restrictions for structured Ruby operations and any commands they invoke. Future cask work should sandbox all *flight run scripts from non-Homebrew and non-system sources, for example scripts shipped by upstream artifacts.

The final target is not to keep legacy hooks and structured steps side by side. Once homebrew/core and homebrew/cask have been converted, all homebrew/core post_install blocks and all homebrew/cask legacy preflight, postflight, uninstall_preflight and uninstall_postflight blocks should be removed for cases covered by structured steps. After that, Homebrew/brew should reject side-by-side usage again and deprecate post_install and legacy cask flight blocks for third-party tap usage.

During the temporary bridge, structured steps must appear before the matching legacy block to make the runtime order obvious: post_install_steps before post_install, and each cask *flight_steps stanza before its matching legacy *flight stanza.

For each future operation type, check homebrew/core and homebrew/cask separately and add formula support only when needed by homebrew/core or cask support only when needed by homebrew/cask.

Specialised method variants, such as using: :postgresql_initdb, require at least 3 current usages across homebrew/core and homebrew/cask before being added to the structured DSL.

When adding install step DSL methods, update the matching RuboCop allow-list so formula or cask tap syntax checks accept the new method in the same context.

RuboCop autocorrection converts the simplest existing post_install and *flight Ruby blocks to steps blocks when every statement is a supported file preparation operation with literal paths and known bases. Future post-install and *flight DSLs should include the same style of conservative autocorrection from the matching legacy Ruby pattern where possible.

Before opening follow-up PRs, run bundle exec rake lint from docs/ to catch markdown lint issues and run brew style homebrew/core homebrew/cask to catch tap-wide formula or cask opportunities exposed by the new DSLs.

Per-DSL Pull Request Workflow

From PR 5 onwards each new DSL step type ships as four separate commits/branches/PRs rather than one combined change:

Add the new DSL in Homebrew/brew: the step method(s), runner execution, shared step block allow-list entries so tap syntax checks accept the method, JSON API round-tripping, tests and docs. No legacy-to-steps autocorrection.
Add the new RuboCops in Homebrew/brew that enforce and audit the DSL: conflict checks against legacy blocks when the step form replaces them, and conservative autocorrection from the matching legacy Ruby pattern.
Tap homebrew/core: convert formulae to the new DSL.
Tap homebrew/cask: convert casks to the new DSL.

Merge order is 1, 3, 4, 2. PR 1 ships the DSL and its allow-list so taps can adopt it; PR 2 (the enforcing/autocorrecting cops) merges last so it does not flag formulae or casks before the DSL is widely available. After PR 1 is merged and before PRs 3 and 4 are merged, cut a new Homebrew/brew stable release so homebrew/core and homebrew/cask CI have the new DSL.

These four PRs are also a stage gate. Before starting the next numbered DSL operation, implement and test the current operation's enforcing/autocorrecting PR 2, record its commit in this plan and run its cops across both taps. The cop can still merge last, but an operation is not complete while its PR 2 is missing. If no safe legacy pattern exists, record the tap scan, representative filenames and negative cop coverage instead of silently omitting the PR.

Each operation PR should also clone, or create clean local worktrees for, homebrew/core and homebrew/cask, make the corresponding tap changes and verify the changed taps with ./bin/brew style, ./bin/brew audit and ./bin/brew readall. The local-tap workflow is:

Run ./bin/brew tap --force homebrew/core.
Run ./bin/brew tap --force homebrew/cask.
Confirm the edit locations with ./bin/brew --repository homebrew/core and ./bin/brew --repository homebrew/cask.
Edit the tap checkout returned by those commands.
Run targeted ./bin/brew style and ./bin/brew audit for changed formulae or casks, then tap-wide ./bin/brew readall homebrew/core and ./bin/brew readall homebrew/cask.
If either tapped checkout has no modifications after the scan and conversion pass, run ./bin/brew untap homebrew/core or ./bin/brew untap homebrew/cask for the unmodified tap before finishing the Homebrew/brew PR.

Do this local tap pass while implementing the Homebrew/brew DSL PR so tap conversions are not left for a separate reminder. If one tap has no applicable changes for an operation, record that with filenames from the scan rather than leaving the tap unchecked.

Long-term success for each operation PR means a tap conversion can remove the whole legacy hook for the case it targets. For formulae, the temporary bridge also allows partial conversions: move the supported repeated statements into post_install_steps, leave the remaining Ruby in post_install and rely on post_install running last. For casks, the matching *flight block should still disappear because cask steps continue to replace legacy flight blocks. If a candidate formula step only covers one statement in a current hook, either include the remaining repeated behaviour as named steps for the same case or document the remaining legacy work with filenames and use the bridge only while the follow-up named step is being built.

Formula Patterns

Local all-file scan source: homebrew/core at ced17121766b. The scan read all 8,459 files under Formula/. Pattern buckets overlap because one post_install can create directories, write files and run commands.

144 of 8,459 formulae define post_install.
post_install_defined is the only install-time Ruby execution flag exposed through the formula JSON API for bottle installs. I did not find a caskfile-only-style source download gate for other formula DSL at bottle install time; formula source downloads for API-loaded formulae are used for source builds, local patches and resources rather than post-install metadata gaps.
79 create shared directories in var, etc or HOMEBREW_PREFIX. Examples: Formula/g/glib.rb, Formula/l/languagetool.rb and Formula/m/mecab.rb.
112 write or patch default configuration/data files. Examples: Formula/n/node@24.rb, Formula/w/wemux.rb and Formula/p/php.rb.
27 rebuild desktop/cache databases. Examples: Formula/g/gjs.rb, Formula/g/geocode-glib.rb and Formula/e/efl.rb.
19 initialise service data directories. Examples: Formula/m/mariadb.rb, Formula/m/mysql.rb, Formula/p/postgresql@12.rb and Formula/p/percona-server.rb.
17 update certificate/trust state. Examples: Formula/o/openssl@3.rb, Formula/lib/libressl.rb and Formula/g/gnutls.rb.
Marker/touch-only conversion surfaces are now smaller because Formula/i/icecast.rb already uses post_install_steps. Remaining touch examples such as Formula/r/r.rb and Formula/n/nethack.rb also contain symlink or permission work, so they need full-hook coverage before conversion.

Refresh the formula buckets with:

rg -n 'def post_install|\.mkpath|mkdir_p|FileUtils\.mkdir|\bmkdir\b' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'def post_install|\.write\b|\.atomic_write\b|File\.write|\binreplace\b' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'glib-compile-schemas|gio-querymodules|gdk-pixbuf-query-loaders|gtk.*update-icon-cache|update-mime-database|update-desktop-database' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'initdb|mysqld.*initialize-insecure|mysql_install_db|PG_VERSION|general_log\.CSM|mysql/user\.frm' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'c_rehash|cert\.pem|openssl.*rehash|\btrust\b|certifi|ca-certificates' Library/Taps/homebrew/homebrew-core/Formula
rg -n 'FileUtils\.touch|\.touch\b|\btouch\b' Library/Taps/homebrew/homebrew-core/Formula

Cask Patterns

Local all-file scan source: homebrew/cask at 4eee0394c96c. The scan read all 7,741 files under Casks/. Pattern buckets overlap because one flight block can prepare files, change permissions and run commands.

Before language variations were serialised, 193 of 7,741 casks required the Ruby source at install time through Cask#caskfile_only?: 170 because of legacy *flight blocks and 23 because of language blocks only. 27 casks had language blocks in total, so 4 had both language blocks and legacy *flight blocks. Language variation API data removes language blocks as a source download gate; the 4 overlapping casks still need source for their legacy flight blocks.
I did not find other current cask install-time Ruby source download gates. Ordinary artifacts, uninstall/zap directives, caveats, dependencies and on_* variations are serialised through API data. *_steps artifacts are also serialised and should not make caskfile_only? true.
68 flight blocks create directories, touch files or write small files. Examples: Casks/a/android-ndk.rb, Casks/b/blender.rb and Casks/c/chromium.rb.
13 move, copy or symlink files during install or uninstall. Examples: Casks/g/gcloud-cli.rb, Casks/l/libcblite.rb and Casks/m/miniconda.rb.
21 change permissions and 36 change ownership. Examples: Casks/b/bitcoin-core.rb, Casks/a/anaconda.rb and Casks/p/parallels.rb.
8 legacy flight blocks directly invoke /usr/bin/security for keychain certificate cleanup. Examples: Casks/c/charles.rb, Casks/a/autofirma.rb and Casks/b/betwixt.rb.
27 casks use language blocks. Large examples include Casks/f/firefox.rb, Casks/l/libreoffice-language-pack.rb and Casks/t/thunderbird.rb.

Refresh the cask buckets with:

rg -n 'preflight|postflight|FileUtils\.mkdir|mkdir_p|\.mkpath|FileUtils\.touch|\.touch\b|\.write\b|File\.write|atomic_write' Library/Taps/homebrew/homebrew-cask/Casks
rg -n 'FileUtils\.(mv|cp|cp_r|ln_s|ln_sf)|\b(mv|cp|cp_r|ln_s|ln_sf)\b|make_symlink|File\.symlink' Library/Taps/homebrew/homebrew-cask/Casks
rg -n 'set_permissions|chmod|FileUtils\.chmod|set_ownership|chown|FileUtils\.chown' Library/Taps/homebrew/homebrew-cask/Casks
rg -n '/usr/bin/security|system_command\s+"/usr/bin/security"|security\s+(delete|add|find)-' Library/Taps/homebrew/homebrew-cask/Casks
rg -n '^\s*language\b' Library/Taps/homebrew/homebrew-cask/Casks

API Source Download Gates

Formula JSON API installs need to preserve post_install because it is the only install-time Ruby hook recorded for bottle installs. The hook runs from the formula stored in the installed keg, while source builds and local patch handling use Homebrew::API::Formula.source_download_formula for build-time reasons outside this post-install DSL work.

Cask JSON API installs use Homebrew::API::Cask.source_download_cask when Cask#caskfile_only? is true. Legacy preflight, postflight, uninstall_preflight and uninstall_postflight blocks need the source because API data only records that a block exists, not the Ruby body. Current API data stores each language block's locale group, default marker, return value and resulting stanza differences, so language-specific URLs can be resolved before the download is enqueued. Older API data with only the flat languages array continues to download source as a compatibility fallback.

Installed Cask Metadata Format

Store supported installed cask metadata as regular <token>.json, not Ruby caskfiles or internal JSON. Casks with uninstall_preflight or uninstall_postflight Ruby blocks should keep using Ruby caskfiles in the Caskroom until those blocks are ported to structured JSON data. The installed caskfile is a post-install snapshot, so it should only retain data that can be useful after installation has finished. This lets future uninstall, reinstall, upgrade and zap runs reload supported installed metadata without evaluating the original Ruby caskfile.

The installed JSON is deliberately minimal. It relies on INSTALL_RECEIPT.json for receipt-owned data such as the installed cask version and uninstallable artifacts, and only keeps data not otherwise available after installation, such as url_specs.only_path when needed to reconstruct staged artifact sources. It omits the full API snapshot so future JSON API or DSL changes cannot affect post-install operations through fields that are not needed after installation.

The installed JSON omits legacy preflight and postflight Ruby block placeholders because JSON cannot represent their block bodies and they are not needed after installation. Casks with uninstall_preflight or uninstall_postflight Ruby blocks must remain backed by Ruby metadata so those blocks continue to run on uninstall, zap, reinstall and upgrade. The goal is to replace those Ruby blocks with structured uninstall step DSLs so they can be migrated to JSON too.

The brew update migration should convert existing supported Caskroom .rb and .internal.json caskfiles to regular .json caskfiles.

As the cask step DSLs grow, keep migrating post-install behaviour from legacy Ruby flight blocks into structured JSON data so less installed cask behaviour is stripped during metadata serialisation.

Install Step Examples

Formula/l/languagetool.rb: post_install_steps with mkdir "log/languagetool", base: :var.
Formula/i/icecast.rb: post_install_steps with one mkdir and two touch steps under var/"log/icecast".
Formula/o/openssl@3.rb: post_install_steps with a forced symlink from ca-certificates pkgetc/"cert.pem" into the formula pkgetc.
Casks/8/86box.rb: preflight_steps with a home-directory mkdir for the shared ROM directory.
Casks/k/klayout.rb: preflight_steps with move_children from the staged root into the nested KLayout directory.
Casks/l/libcblite.rb: postflight_steps with relative symlink steps marked for uninstall cleanup.

Implementation Checklist

[x] PR 1, shared install steps framework. Commit: Add install steps framework. Scope: shared ordered step data, a confined steps DSL, a shared runner, cask stanza ordering, RuboCop registration, conflict checks and the refactor plan. This PR does not wire formula or cask JSON API output or run steps from install phases. Estimated existing formulae/casks affected: 0 runtime behaviour changes. It creates the guardrails for the later 144 formulae with post_install blocks and 170 casks with flight blocks, but no existing formula or cask opts into the new DSL yet. Notes for the next PRs: keep the step payload as an ordered array; keep _steps blocks literal-only; for formulae, steps run before a remaining post_install hook during the temporary bridge; for casks, steps win over the legacy Ruby block with a runtime warning. Add conservative autocorrection only where every legacy statement maps mechanically.
[x] PR 2, formula post_install_steps. Commit: Add formula install steps. Scope: formula DSL, formula JSON API data, API formula loading, installer and brew postinstall execution, formula cookbook docs and formula fixture. Estimated existing formulae affected: 144 formulae currently define post_install. The first useful conversion surface is roughly 79 formulae creating shared directories; parts of the 19 service data directory and 17 certificate/trust formulae may also move once their operations fit the supported step set. Runtime behaviour changes only for formulae that opt into post_install_steps. Notes for implementation: default mkdir/touch to var and source/target paths to prefix; expose the ordered array through FormulaStruct; make post_install_steps run before any remaining post_install; document that the two forms may coexist only as an incremental conversion bridge. Keep the tap-wide autocorrect audit in a follow-up commit so the implementation can land before converted formulae.
[x] PR 3, cask flight steps. Commit: Add cask install steps. Scope: cask artifacts for preflight_steps, postflight_steps, uninstall_preflight_steps and uninstall_postflight_steps, cask API serialisation through artifact data, installer casts, cask cookbook docs, cask fixture/API loader coverage. Estimated existing casks affected: 170 casks currently use flight blocks. The first useful conversion surface is roughly 68 casks that create/touch files or directories and the supported subset of 13 casks that move or symlink files. Runtime behaviour changes only for casks that opt into the new *_steps stanzas. Notes for implementation: default all relative cask paths to staged_path; keep steps as normal cask artifacts so API loader round-trips work; make steps remove/override the matching Ruby flight artifact with a warning; keep uninstall: true symlink cleanup available for install-phase steps. Keep the tap-wide autocorrect audit in a follow-up commit so the implementation can land before converted casks.
[x] PR 4, desktop and cache rebuild actions. Estimated existing formulae/casks affected: about 27 formulae run rebuild tools such as glib-compile-schemas, gtk*-update-icon-cache, gio-querymodules, gdk-pixbuf-query-loaders, update-mime-database and update-desktop-database; no cask count was identified in the initial scan. Scope: shared named action types for GSettings schemas, GIO modules, GDK Pixbuf loaders, GTK icon caches, MIME databases and desktop databases, runner dispatch through Homebrew-owned tools and docs. Notes for implementation: add named action types rather than raw commands; define idempotence and failure handling; decide whether any action invokes non-Homebrew code and should be ready for future sandboxing. Land RuboCop autocorrection and tap-wide conversions in a separate follow-up after the new DSL methods are available in a stable Homebrew release.
[x] PR 4.1, formula install-step sandboxing. Commit: Sandbox formula install steps. Scope: run structured formula steps inside the existing post-install child process so macOS Seatbelt and Linux Bubblewrap apply the same filesystem and network policy as legacy post_install hooks. This must land before any tap migrations use filesystem-mutating steps.
PR 5, default config and template writes (four-PR workflow above). Estimated existing formulae/casks affected: about 112 formulae write or patch default configuration/data files, and a subset of the 68 file-prep cask flight blocks write small files. Notes for implementation: use scoped token expansion instead of arbitrary Ruby interpolation; require literal templates or API-safe template data; define overwrite, unless_exists and upgrade semantics before adding autocorrection.
- [x] PR 5.1, add the write DSL in Homebrew/brew. Commit: Add install step config writes. Scope: shared write step method with base: and overwrite:, runner execution that skips existing files unless overwrite is set, formula and cask step block allow-list entries, non-interpolated heredoc (dstr) support so write content can use heredocs, runner tests and cookbook docs. Default behaviour preserves existing files so user edits survive upgrades. Content stays a literal template in the JSON API but supports a fixed {{...}} token allow-list (HOMEBREW_PREFIX, prefix, opt_prefix, bin, var, etc, pkgetc, version, version.major_minor; casks add staged_path and appdir) expanded at install time; any other {{...}} is left verbatim. Dynamic interpolation (random cookies, popen-derived paths, File.read rewrites) is intentionally out of scope and stays as legacy Ruby.
- [x] PR 5.2, add the write enforcing RuboCops in Homebrew/brew. Commit: Add install step write cops. Scope: formula and cask RuboCops conservatively autocorrect literal, newline-terminated .write, .atomic_write and File.write legacy blocks to *_steps write calls with overwrite: true. Writes without trailing newlines stay as legacy Ruby because the step DSL appends one.
- [x] PR 5.3, convert homebrew/core formulae to write. Branch install-steps-config-write, commits tronbyt-server: use post_install_steps and node@18: use post_install_steps. tronbyt-server mapped with literal content; node@18 became convertible once {{HOMEBREW_PREFIX}} token expansion landed (its whole post_install was one atomic_write). All other .write formulae interpolate paths, interpolate unsupported values, or run unsupported Ruby (cp_r, inreplace, safe_popen_read, loops).
- [x] PR 5.4, convert homebrew/cask casks to write. Branch install-steps-config-write, commit dnsmonitor: use postflight_steps. Only dnsmonitor had a flight block with literal content. Token expansion does not unblock more casks: the {{appdir}}-content flight writes all target a shimscript local that is also wired to a binary stanza, and the literal-path LibreOffice packs interpolate an unsupported language token and run system_command.
[x] PR 6.1, database and service data directory initialisation. Commit: Add install step data directories. Estimated existing formulae/casks affected: about 19 formulae initialise service data directories. Scope: formula init_data_dir step, runner execution, formula step block allow-list entries, fixture coverage and formula cookbook docs. The step creates service data directories and supports named bootstrap commands for PostgreSQL initdb, MySQL mysqld --initialize-insecure and MariaDB mysql_install_db, including the marker-file and CI-skip guards used by current homebrew/core formulae. Permission and ownership metadata were skipped because current tap usages fit future permission/ownership action work instead. PostgreSQL versioned link maintenance is handled by generic link_dir and link_children steps. MySQL conflicting configuration warnings stay as legacy Ruby until a separate named action is added. Local tap work for this step was prepared with ./bin/brew tap --force homebrew/core and ./bin/brew tap --force homebrew/cask. In this checkout, ./bin/brew --repository homebrew/core resolves to Library/Taps/homebrew/homebrew-core at 369b5855942, and ./bin/brew --repository homebrew/cask resolves to Library/Taps/homebrew/homebrew-cask at 16a3a6e4562. Success target for tap conversions: use the bridge to move database bootstrap statements out of every current MySQL and PostgreSQL hook, including Formula/m/mysql.rb, Formula/m/mysql@8.0.rb, Formula/m/mysql@8.4.rb, Formula/p/postgresql@17.rb and Formula/p/postgresql@18.rb, while their remaining warning or link maintenance work stays in post_install until separate named actions cover it. Fully remove post_install from bootstrap-only formulae such as Formula/m/mariadb.rb, Formula/m/mariadb@10.11.rb, Formula/m/mariadb@10.5.rb, Formula/m/mariadb@10.6.rb, Formula/m/mariadb@11.4.rb, Formula/m/mariadb@11.8.rb, Formula/p/postgresql@12.rb, Formula/p/postgresql@13.rb, Formula/p/postgresql@15.rb and Formula/p/postgresql@16.rb. Verify the homebrew/core conversion with ./bin/brew style homebrew/core, targeted ./bin/brew audit --strict --online --formula ... for the changed formulae and ./bin/brew readall homebrew/core.
[x] PR 6.2, database and link enforcement. Commit: Add install step enforcement cops. Scope: the formula install-step cop conservatively autocorrects recognised PostgreSQL, MySQL and MariaDB bootstrap statements to init_data_dir, and recognised PostgreSQL link maintenance to link_dir or link_children. Partial conversions preserve existing post_install_steps ordering and leave unsupported warning or maintenance work in post_install. Matching Percona bootstrap hooks remain unchanged because they were not part of the recorded MySQL formula conversion.
[x] PR 7.1, certificate and trust store actions. Commit: Add install step keychain cleanup. Estimated existing formulae/casks affected: about 17 formulae update certificate/trust state and 8 cask flight blocks invoke /usr/bin/security for keychain certificate cleanup. Scope: cask delete_keychain_certificate step, runner execution through fixed /usr/bin/security find-certificate and delete-certificate calls, optional local certificate fingerprint matching for selective deletion, cask step block allow-list entries and docs. Formula-owned cert.pem symlinks use the existing ln_sf step with source_formula and source_base: :formula_pkgetc; specialised trust store generation such as ca-certificates bundle regeneration and Mono cert-sync stays legacy Ruby because current repeated usage is below the named-variant threshold.
[x] PR 7.2, certificate and keychain enforcement. Commit: Add install step enforcement cops. Scope: the cask install-step cop converts fixed /usr/bin/security certificate deletion flights to delete_keychain_certificate. The formula cop converts the three direct pkgetc certificate bundle replacements to forced symlink steps using source_formula and source_base: :formula_pkgetc. Dynamic paths, altered commands and specialised certificate generation remain unsupported.
[x] PR 8.1, cask permission and ownership actions. Commit: Add cask permission steps. Estimated existing casks affected: about 21 casks change permissions and 36 change ownership. Scope: cask set_permissions and set_ownership steps, path-array API normalisation, runner execution through chmod and sudo chown, cask installer command routing, App Management checks before ownership changes, cask step block allow-list entries, fixture/API loader coverage and cask cookbook docs. The steps skip missing paths like the existing flight mini-DSL. set_ownership defaults to the current user and staff group unless user: or group: are provided. Local tap work converted pure set_permissions and set_ownership flight blocks in 48 homebrew/cask casks. homebrew/core had no matching formula conversions for the cask-only DSL and was untapped after the clean scan. Remaining cask legacy blocks are Casks/s/starnet++.rb, Casks/h/hummingbird.rb, Casks/m/mplabx-ide.rb and Casks/p/proxy-audio-device.rb; they depend on unsupported local variables, architecture data or additional system_command work.
[x] PR 8.2, permission and ownership enforcement. Commit: Add install step enforcement cops. Scope: the cask install-step cop converts pure legacy flight blocks using set_permissions and set_ownership to matching *_steps blocks. Mixed flights, dynamic paths and unsupported arguments remain unchanged.
[x] PR 9, cask language variations in API data. Commit: Serialise cask language variations. Estimated existing casks affected: 27 casks use language blocks, with large examples including Casks/f/firefox.rb, Casks/l/libreoffice-language-pack.rb and Casks/t/thunderbird.rb. Scope: serialise a deterministic default plus ordered language variation deltas containing locale groups, the default marker, return values and all resulting API stanza changes. Public and internal API loaders select exact or partial locale matches and fall back to the default. Cask downloads use the selected URL and checksum directly, while older API data still falls back to source. Artifact differences are included so all 27 current language casks, including cave-story and wondershare-edrawmax, can use API data.