Status: accepted (2026-08-20; contract-identity amendment 2026-08-24).
Context
Protocol artifacts already carry protocol_revision as a digest-covered
member. Identifier-level version tokens (module names like V2Decoder,
paths like priv/v1/, function names like decode_v2) would create a
second, uncoordinated versioning axis — the classic drift surface where
two names claim to be current and neither is.
Decision
No version token appears in any shipped identifier: module segment,
function or macro name, atom, struct key, corpus path, or config key.
The Hex package's semantic version and its exact mix.exs package-tag source
reference are the sole permitted version-bearing durable identities. Enforced
mechanically: the identifier-naming gate reds on every
conventional token form (leading v<N>, snake-boundary _v<N>,
CamelCase hump V<N>) and on path segments. ADR filenames are
slug-only (no numeric sequence prefixes) for the same reason — document
sequence numbers are a versioning axis.
Consequences
Evolution happens at the revision boundary inside the artifact, where
it is digest-covered and negotiation-gated; the code surface stays
version-free and rename-stable. The mechanical gate makes regressions
loud. The accepted package surfaces live in mix.exs: Hex semver and the exact
source_ref: "v#{@version}" tag identity. Path, source kind, and spelling are
part of the mechanical allowlist; a lookalike in any other location is rejected.
Wire revisions remain digest-covered data. No module, function, path, config key,
queue, event, database object, or internal compatibility branch may derive its
name from a release, task, or implementation sequence.