v2026.4.8 — Phase Sigils and the :script Profile

v2026.4.8 — Phase Sigils and the :script Profile

Release date: 2026-04-22 Profiles affected: :core, :service, :script (new) Status: Standard release (6-month support)

This release codifies a language-level clarification that has been developing across the last two weeks and opens a new rung at the bottom of the profile ladder for quick, throwaway-or-promote programs.

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The Three-Sigil Phase System

Janus now encodes phase directly in its sigils. Every sigil belongs to exactly one world; no sigil crosses worlds.

Sigil	World	What it does	Examples
§	Compile-time	Structural computation, type reflection, code generation	§size_of(T), §type_info(T), §{ ... }
$	Extraction	Runtime pattern capture (regex, PEG, positional scripting)	$1, $2, $*
@	Metadata	FFI bindings, attributes, capability declarations	@ffi(path: ..., lang: .c), @requires(...)

What changes for existing code:

• Compile-time builtins migrate from $ to §. $size_of is deprecated with warning W5001 in favor of §size_of. Same for $align_of, $offset_of, $is_integral, $is_float, and similar.
• The $ sigil is now exclusively reserved for extraction — runtime pattern capture and the :script profile positional system.
• @ is declaration-time only. let x = @ffi(...) was never valid and is now explicitly rejected; @ffi(...) attaches to an extern func declaration, nothing else.

Why this matters: The old convention overloaded $ for two unrelated phases — compile-time introspection and runtime extraction. That ambiguity meant readers had to infer which world a $name lived in from context. Splitting the worlds into three sigils with one purpose each makes every expression self-identifying about when it runs.

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The :script Profile

A new profile sits at the bottom of the ladder, below :core:

:sovereign  → bare-metal
:compute    → SIMD, tensors, device offload
:cluster    → actors, supervision, distribution
:service    → daemons, networking, structured concurrency
:core       → deterministic micro-systems
:script     → interactive scripting            (NEW)

:script is :core with three additions and zero subtractions:

1. Implicit defaults — entry point, allocator, capability set, common imports are all inferred.
2. A bounded sugar surface — top-level statements, $-family positional arguments ($1, $2, $*), ergonomics that desugar mechanically into legal :core.
3. AOT-cached execution — janus path/to/file.jans feels instant via content-addressed cache. No interpreter, no JIT, no second semantics.

The Script Law: Every :script program is a syntactically valid :core program after janus desugar. The transformation is purely additive. Promotion from :script to :core never requires a rewrite.

What :script is deliberately NOT:

• Not dynamically typed
• No meta.eval("code") — reflection is typed-AST only
• No hot reload
• No second error system (!T propagation remains the only mechanism)
• No second concurrency primitive (nurseries remain the only concurrency mechanism)
• Cannot be published through Hinge — :script artifacts are local-only

Status: Rough around the edges, but working. Suitable for throwaway scripts, one-off tooling, and quick prototypes that may later promote to :core.

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The Language Reference is now canonical

Janus/.agents/architecture/LANGUAGE-REFERENCE.md is the single-source doctrine for writing Janus code — for humans and AI agents alike. It covers :core and :service completely, and :script as draft.

Two laws now sit at the foundation of the syntax:

Law 1 — do...end for control flow (imperative, vertical):

if cond do ... end
while cond do ... end
for iter do |x| ... end
func name() do ... end
test "name" do ... end

Law 2 — { } for data structures (declarative, containers):

struct { field: type }
enum { Variant }
match expr { pattern => value }
extern struct { field: type }

These two laws are non-negotiable. No exceptions. Every syntactic question in Janus answers itself once you ask: is this control flow, or is this a container?

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Other notable items

• Doc comments use bare keys, not sigils: param:, returns:, error:, capability:, since:, see:, deprecated:, safety:, complexity:. No @ prefix — @ is reserved for metadata declarations, and documentation is not metadata.
• discard keyword for explicit value discarding at statement level — replaces Zig’s _ = expr. Clear intent: “I am intentionally ignoring this result.”
• test is a reserved keyword. test "name" do ... end is the only valid use. Naming a function, variable, or type test is a parse error.

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Upgrade notes

• Compile-time builtins using $ prefix ($size_of etc.) will emit warning W5001. Migrate to §size_of at your convenience — warnings, not errors.
• Existing :core and :service code should compile unchanged (modulo the $→§ deprecation).
• Files using test as an identifier need renaming. The parser will flag these clearly.

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Binary version: 2026.4.8 Git hash: 84133fa Built on: 2026-04-22