diff --git a/build/versions.env b/build/versions.env
index 0db349e..45e8061 100644
--- a/build/versions.env
+++ b/build/versions.env
@@ -4,7 +4,9 @@
 # Toolchain bundle version. Each publish is an immutable, version-tagged
 # release `v<TOOLCHAIN_VERSION>` holding the whole set; consumers pin this one
 # number, and the cache is keyed by it (cache/yeet/toolchain/v<N>/<arch>/). CI
-# bumps it by 0.1 on every publish (which only happens when build/ changes).
+# computes it as semver (vMAJOR.MINOR.PATCH) from the [bump:*] markers on the
+# commits since the last release (default minor); see the README. Republished
+# only when build/ changes.
 TOOLCHAIN_VERSION=0.1
 
 # Where a consumer fetches assets from: the version-tagged release. The fetch