Rebranding: rexlang → Phero Lang

rexlang is now Phero Lang. From 0.3.0 the compiler is pherolang, the crates are phero-*, the serialized artifacts carry pheroVersion, and the repository is yestechgroup/pherolang. The language is unchanged: the grammar, the file extensions, and the surface pipeline are exactly as they were. The spelling rules live in NAMING.md; this page is the mechanical map for an existing user.

The one step you cannot avoid is regenerating artifacts — 0.3 does not read 0.2 artifacts:

PHERO_UPDATE_FIXTURES=1 cargo test --workspace

CLI, install, and repository

Before	After
binary rexlang <command>	pherolang <command>
cargo run -p rex-cli -- <command>	cargo run -p phero-cli -- <command>
cargo install --git https://github.com/yestechgroup/rexlang ... rex-cli	cargo install --git https://github.com/yestechgroup/pherolang --tag vX.Y.Z phero-cli
completions and man pages emitted as rexlang.*	pherolang.*
rexlang --version banner	pherolang --version
repo yestechgroup/rexlang	yestechgroup/pherolang

Every subcommand keeps its name and flags: check, fmt, ir, build, graph, gen, artifact check, explain, vocab fetch, completions, man, lsp.

Environment variables

Before	After	Used by
REX_UPDATE_FIXTURES	PHERO_UPDATE_FIXTURES	golden regeneration across the suite
REX_VERSION	PHERO_VERSION	the test-local version constant (CARGO_PKG_VERSION)
REX_DISK_MIN_GB	PHERO_DISK_MIN_GB	scripts/ci-local.sh free-space warning
REX_EXAMPLES_DIR	PHERO_EXAMPLES_DIR	the examples harness
REX_INSTANCE_OUT	PHERO_INSTANCE_OUT	instance emission in the examples
REX_CURRENCY_INSTANCE_OUT	PHERO_CURRENCY_INSTANCE_OUT	currency-instance emission
REXFMT	PHEROFMT	formatter override

REXFMT is the odd one out: it carries no underscore, so its replacement is PHEROFMT, not PHERO_FMT. Every other name takes the REX_ → PHERO_ prefix mechanically. REX_VERSION is a test-local constant rather than a process variable, but it is renamed with the rest and keeps CARGO_PKG_VERSION as its value source.

Crates and public types

The rule is rex-<name> → phero-<name>, and all 22 workspace crates are covered:

Before	After
rex-syntax	phero-syntax
rex-parser	phero-parser
rex-ir	phero-ir
rex-expr	phero-expr
rex-ifml	phero-ifml
rex-driver	phero-driver
rex-backend-rust	phero-backend-rust
rex-backend-jsonschema	phero-backend-jsonschema
rex-backend-cedar	phero-backend-cedar
rex-backend-cmmn	phero-backend-cmmn
rex-backend-dmn	phero-backend-dmn
rex-backend-common	phero-backend-common
rex-vocab	phero-vocab
rex-lsp	phero-lsp
rex-runtime	phero-runtime
rex-cli	phero-cli
rex-verify	phero-verify
rex-diagnostics	phero-diagnostics
rex-evidence	phero-evidence
rex-strings	phero-strings
rex-dates	phero-dates
rex-testkit	phero-testkit

Three public types rename with the prefix: RexBackend → PheroBackend, RexError → PheroError, RexExpr → PheroExpr. Rust imports follow the module path, so use rex_driver::… becomes use phero_driver::…, and generated Rust links against phero_runtime:: instead of rex_runtime::.

Wire keys and format versions

Surface	Before	After
Provenance key	rexVersion	pheroVersion
Instance discriminator	"$type": "rex.instance"	"$type": "phero.instance"
JSON-Schema $id URN	urn:rex:model:<pkg>:<profile>	urn:phero:model:<pkg>:<profile>
Every format version	"formatVersion": 1	"formatVersion": 2

All ten format constants plus INSTANCE_FORMAT_VERSION go 1 → 2, because every one of those artifacts now carries a different provenance key:

Constant	Artifact
FORMAT_VERSION	Core IR (Model)
ACTOR_MODEL_FORMAT_VERSION	ActorModel
DDD_MODEL_FORMAT_VERSION	DddModel
IFML_MODEL_FORMAT_VERSION	IfmlModel
IFML_MANIFEST_FORMAT_VERSION	control/route manifest
EVENT_MODEL_FORMAT_VERSION	EventModel
DEPLOY_MODEL_FORMAT_VERSION	DeployModel
USE_CASE_MODEL_FORMAT_VERSION	UseCaseModel
CMMN_MODEL_FORMAT_VERSION	CmmnModel
DMN_MODEL_FORMAT_VERSION	DmnModel
INSTANCE_FORMAT_VERSION	canonical instance JSON

Three markers deliberately stay at 1: GRAPH_MODEL_FORMAT_VERSION, the graph query envelope version, and the receipt and proof-register format versions. None of them carries a provenance key, so none of them changes shape; bumping them would invalidate committed graph and receipt artifacts for a rename that never touched them.

Artifact naming and filesystem paths

Before	After
model.rex.json	model.phero.json
target/rex (default build output)	target/phero
tests/conformance/ifml/rexlang/	tests/conformance/ifml/phero/
formal/lean/RexExpr.lean	formal/lean/PheroExpr.lean
target/scratch/rex-examples-test	target/scratch/phero-examples-test
rex-cli-tests-* temp dirs	phero-cli-tests-*

build derives each output name from its input path, so .phero.json is a convention documented in the READMEs, not something the command enforces — an old-named file still builds, it just embeds the new wire generation.

LSP identity

LSP surface	Before	After
Diagnostic source	rexlang	pherolang
Server/client identity (SOURCE_NAME)	rexlang	pherolang
Binary the client launches	…/rexlang lsp	…/pherolang lsp

Client settings keys are unchanged — the VS Code extension still speaks mox.server.path, mox.server.args, and mox.server.languages, because the language id did not move.

What does not change

• Grammar and file extensions. .mox, .ddd, .actor, .dmn, .evt, .uc, .cmmn, .ifml, .deploy.
• The wire rules. camelCase keys, adjacent tagging, the formatVersion gate, and additive-only evolution.
• Fixture namespacing. nz.example.* package names.
• Diagnostic codes. E0104 and the rest of the allocation ledger are numbers, so pherolang explain answers the same codes as before.
• External toolchains. sigil, restingstate/xstate-ir, dsntk, cmmn-rs.
• History. The v0.2.0 tag and every historical CHANGELOG.md section stay under the old name.

0.2 artifacts are rejected

0.3 does not read 0.2 artifacts, and there is no dual-accept window. A saved artifact that still carries rexVersion or "$type": "rex.instance" fails pherolang artifact check with:

0.2-era rexlang artifact — regenerate with pherolang 0.3

To regenerate, run the migration command once:

PHERO_UPDATE_FIXTURES=1 cargo test --workspace

This is the single allowed pre-1.0 wire break. It is a clean break on purpose: renaming the provenance key without bumping formatVersion would leave two artifact generations sharing a version number while differing in shape, which is exactly what the version gate exists to prevent. VERSIONING.md states the policy; the 0.3.0 changelog entry records the break.

Downstream consumers

• Bump the git revision and the package names in your [dependencies]: rex-ir → phero-ir, rex-driver → phero-driver, and so on. The old paths in the pinned revision still resolve, but nothing under them is the new API.
• Regenerate every artifact you commit. Expect pheroVersion in the provenance slot and "formatVersion": 2 in every file.
• If you generate Rust, the emitted code imports phero_runtime::; add phero-runtime to the generated crate’s manifest at the same revision and drop rex-runtime.
• Run pherolang artifact check over your committed artifacts before merging — it names every stale file rather than failing generically.

Operator checklist

Actions that do not appear in a repository diff:

• Rename the GitHub repository yestechgroup/rexlang → yestechgroup/pherolang, then confirm old URLs redirect — owner:
• Set About: description, homepage https://pherolang.com, topics, social preview image — owner:
• Enable GitHub Discussions — owner:
• Point the open web epics (#226–#236) at the new repo and asset names — owner:
• Tag v0.3.0 “Phero Lang” and publish release notes from the changelog — owner:
• Publish renamed release assets (one binary per enabled target, plus SHA256SUMS; the darwin rows wait on macOS runners) — owner:
• 301 rexlang.com → pherolang.com, and docs.rexlang.com → docs.pherolang.com — owner:
• Create the hello@ and security@ aliases (open question on the epic) — owner:
• Secure the @pherolang social handles (same open question) — owner: