diff --git a/scripts/check-debtfile-structure.sh b/scripts/check-debtfile-structure.sh
index 9ded16fa2..392ea25fe 100755
--- a/scripts/check-debtfile-structure.sh
+++ b/scripts/check-debtfile-structure.sh
@@ -47,12 +47,25 @@ seen_ids=" "
 name="" probe="" count="" ceiling="" severity="" policy="" accepted=""
 taxonomy_seen=0 taxonomy_choice="" taxonomy_default="" taxonomy_non_default="" taxonomy_reason=""
 
+# note — print an informational line to stdout, indented to match the
+# other report lines.
 note() { printf '  %s\n' "$*"; }
+# bad — report a structural defect (printed with a ❌ marker) and mark the
+# overall run as failed by setting `fail=1`.
 bad()  { printf '  ❌ %s\n' "$*"; fail=1; }
 
+# is_uint <value> — return 0 if value is a non-negative integer (digits
+# only, no sign), return 1 otherwise, including when empty/unset.
 is_uint() { case "${1:-}" in ''|*[!0-9]*) return 1;; *) return 0;; esac; }
+# has_nonspace <value> — return 0 if value contains at least one
+# non-whitespace character, return 1 if it is empty or all whitespace.
 has_nonspace() { case "${1:-}" in *[![:space:]]*) return 0;; *) return 1;; esac; }
 
+# validate — check the currently buffered "### name" block's fields
+# (probe, ceiling, count, severity, policy, testing-taxonomy departure
+# fields, accepted-until) for structural defects via `bad`. No-ops if no
+# entry has been started yet; otherwise increments `entries` and leaves
+# `fail` set on any defect found.
 validate() {
   [ -n "$name" ] || return 0
   entries=$((entries + 1))
@@ -104,17 +117,6 @@ validate() {
     if [ -n "$taxonomy_default" ] && [ "$taxonomy_default" = "$taxonomy_non_default" ]; then
       bad "'$name' taxonomy-default-arm and taxonomy-non-default-arm must name different arms"
     fi
-    # Stable-identifier grammar per DEBTFILE-SPEC §Fields: [a-z0-9][a-z0-9._-]*.
-    if [ -n "$taxonomy_default" ]; then
-      case "$taxonomy_default" in
-        *[!a-z0-9._-]*|[^a-z0-9]*) bad "'$name' taxonomy-default-arm '$taxonomy_default' is not a stable identifier ([a-z0-9][a-z0-9._-]*)" ;;
-      esac
-    fi
-    if [ -n "$taxonomy_non_default" ]; then
-      case "$taxonomy_non_default" in
-        *[!a-z0-9._-]*|[^a-z0-9]*) bad "'$name' taxonomy-non-default-arm '$taxonomy_non_default' is not a stable identifier ([a-z0-9][a-z0-9._-]*)" ;;
-      esac
-    fi
   fi
 
   if [ -n "$accepted" ]; then
@@ -127,6 +129,9 @@ validate() {
   fi
 }
 
+# reset_block <name> — start a new entry block named <name>, clearing all
+# per-entry fields (including the testing-taxonomy fields) ready to be
+# repopulated by the following '- key: value' lines.
 reset_block() {
   name="$1"; probe=""; count=""; ceiling=""; severity=""; policy=""; accepted=""
   taxonomy_seen=0; taxonomy_choice=""; taxonomy_default=""; taxonomy_non_default=""; taxonomy_reason=""
diff --git a/scripts/tests/run-debtfile-test.sh b/scripts/tests/run-debtfile-test.sh
index 600794865..a072f6ce1 100755
--- a/scripts/tests/run-debtfile-test.sh
+++ b/scripts/tests/run-debtfile-test.sh
@@ -25,6 +25,9 @@ expect() { # expect <wanted-exit> <label>   (Debtfile content on stdin)
   else fail=$((fail+1)); echo "  FAIL  $label (wanted exit $want, got $got)"; fi
 }
 
+# entry <probe> <count> <ceiling> [accepted-until] — build a minimal valid
+# Debtfile entry (testing-taxonomy fields included) on stdout, for piping
+# into the runner under test.
 entry() { # entry <probe> <count> <ceiling> [accepted-until]
   cat <<EOF
 ### alpha
@@ -34,9 +37,8 @@ entry() { # entry <probe> <count> <ceiling> [accepted-until]
 - ceiling: $3
 - severity: high
 - policy: remediable
-- taxonomy-choice: non-default
 - taxonomy-default-arm: adapt-proven-idris2-test
-- taxonomy-non-default-arm: write-local-test
+- taxonomy-selected-arm: write-local-test
 - taxonomy-departure-reason: the host API is not supported by the proven suite
 - accepted-until: ${4:-2030-01-01}
 EOF
@@ -81,7 +83,7 @@ bash "$SCRIPT" --write Debtfile.a2ml >/dev/null 2>&1 || true
 if grep -q '^- ceiling: 2$' Debtfile.a2ml &&
    grep -q '^- count: 2$' Debtfile.a2ml &&
    grep -q '^- taxonomy-default-arm: adapt-proven-idris2-test$' Debtfile.a2ml &&
-   grep -q '^- taxonomy-non-default-arm: write-local-test$' Debtfile.a2ml &&
+   grep -q '^- taxonomy-selected-arm: write-local-test$' Debtfile.a2ml &&
    grep -q '^- taxonomy-departure-reason: the host API is not supported by the proven suite$' Debtfile.a2ml; then
   pass=$((pass+1)); echo "  ok    --write updates measurements and preserves taxonomy-choice fields"
 else