feat: bound changelog fragment entries

BUILDER.md

@@ -141,7 +141,10 @@ triage bug, and the move is to say so on the issue, not to guess.
   cross-repo) — the exact prose that will be published, nothing else: `- `
   bullets, and in a grouped repo the `### Added` / `### Changed` /
   `### Fixed` headings inside the fragment, creating a rarer kind only when
-  a change genuinely is one. Never edit `CHANGELOG.md` for an entry — the
+  a change genuinely is one. Each entry is at most 300 characters after
+  wrapped lines are joined and whitespace is collapsed; a genuinely long
+  change ships as several short `- ` entries in the same fragment, never one
+  long entry. Never edit `CHANGELOG.md` for an entry — the
   release PR assembles the section from the fragments (#112); the monotonic
   guard still refuses anything that deletes a shipped heading.
 - Follow the repo's conventions file and match the code you touch. Tests are

CHANGELOG.md

@@ -5,7 +5,10 @@ published verbatim as that release's body (lib/changelog.sh extracts it),
 so entries say what changed, cite the issue, and stop. Entries arrive as
 fragments — one `changelog.d/<issue>.md` per PR, never an edit to this
 file — and the release PR assembles them into the next section here
-(`bin/changelog-assemble`, #112).
+(`bin/changelog-assemble`, #112). Each entry is at most 300 characters after
+wrapped lines are joined and whitespace is collapsed; a genuinely long
+change ships as several short `- ` entries in the same fragment, never one
+long entry.
 
 ## 0.3.0 — 2026-07-24
 

changelog.d/167.md

@@ -0,0 +1 @@
+- Bound changelog entries at 300 normalized characters in the shared fragment validator, with boundary, wrapping, grouping, and forward-only coverage; document splitting genuinely long changes into several short entries (#167).

lib/changelog.sh

@@ -104,6 +104,9 @@ changelog_fragments() {
 #     a smuggled one would split the published section;
 #   - at least one bullet: a heading is not an entry — the rule the
 #     publisher enforces at release time, moved onto the PR;
+#   - at most 300 characters per normalized entry: prose drift is refused
+#     where it is written (#167), with wrapped continuation lines joined and
+#     whitespace collapsed before measuring;
 #   - no '### ' heading without a bullet before the next heading or EOF:
 #     the dangling grouped heading #98 taught us to refuse.
 changelog_fragment_problem() {
@@ -125,6 +128,44 @@ changelog_fragment_problem() {
     return 1
   fi
 
+  problem="$(
+    awk '
+      function inspect( normalized, preview) {
+        if (entry == "") return
+        normalized = entry
+        gsub(/[[:space:]]+/, " ", normalized)
+        sub(/^ /, "", normalized)
+        sub(/ $/, "", normalized)
+        if (length(normalized) > 300) {
+          preview = substr(normalized, 1, 60)
+          print length(normalized) "\t" preview
+          entry = ""
+          exit
+        }
+      }
+      /^[[:space:]]*[-*][[:space:]]/ {
+        inspect()
+        entry = $0
+        sub(/^[[:space:]]*[-*][[:space:]]+/, "", entry)
+        next
+      }
+      /^### / {
+        inspect()
+        entry = ""
+        next
+      }
+      entry != "" { entry = entry " " $0 }
+      END { inspect() }
+    ' "$file"
+  )"
+  if [ -n "$problem" ]; then
+    local length preview
+    IFS="$(printf '\t')" read -r length preview <<<"$problem"
+    printf "fragment '%s' has an overlong entry '%s…': %s characters, bound 300 — split it into multiple '- ' entries in this same fragment\n" \
+      "$file" "$preview" "$length"
+    return 1
+  fi
+
   problem="$(
     awk '
       /^### / {

test/changelog.test.sh

@@ -259,6 +259,54 @@ check "fragment predicate: a dangling grouped heading is refused, heading named"
   "has an empty heading: '### Added'" \
   changelog_fragment_problem "$PF/22.md"
 
+entry_of_length() {
+  local count="$1"
+  awk -v count="$count" 'BEGIN {
+    printf "%0*d\n", count, 0
+  }'
+}
+
+printf -- '- %s\n' "$(entry_of_length 300)" >"$PF/23.md"
+check "fragment predicate: a 300-character entry passes" 0 "" \
+  changelog_fragment_problem "$PF/23.md"
+
+printf -- '- %s\n' "$(entry_of_length 301)" >"$PF/24.md"
+check "fragment predicate: a 301-character entry is refused with actionable detail" 1 \
+  "301 characters, bound 300 — split it into multiple '- ' entries in this same fragment" \
+  changelog_fragment_problem "$PF/24.md"
+check "fragment predicate: an overlong diagnosis previews the entry" 1 \
+  "000000000000000000000000000000000000000000000000000000000000…" \
+  changelog_fragment_problem "$PF/24.md"
+
+{
+  printf -- '- %s\n' "$(entry_of_length 200)"
+  printf -- '- %s\n' "$(entry_of_length 200)"
+} >"$PF/25.md"
+check "fragment predicate: several bounded entries may total over 300 characters" 0 "" \
+  changelog_fragment_problem "$PF/25.md"
+
+{
+  printf -- '- %s\n' "$(entry_of_length 60)"
+  printf '  %s\n' "$(entry_of_length 60)"
+  printf '  %s\n' "$(entry_of_length 60)"
+  printf '  %s\n' "$(entry_of_length 67)"
+} >"$PF/26.md"
+check "fragment predicate: a roughly 250-character entry may wrap over four lines" 0 "" \
+  changelog_fragment_problem "$PF/26.md"
+
+{
+  printf '### Added\n\n'
+  printf -- '- %s\n\n' "$(entry_of_length 300)"
+  printf '### Fixed\n\n'
+  printf -- '* %s\n' "$(entry_of_length 301)"
+} >"$PF/27.md"
+check "fragment predicate: grouped headings are not counted and grouped bullets are bounded" 1 \
+  "301 characters, bound 300" \
+  changelog_fragment_problem "$PF/27.md"
+
+check "section predicate: published over-bound entries remain unvalidated" 0 "" \
+  changelog_section_problem "$ROOT/CHANGELOG.md" 0.3.0
+
 # --- the assembler (#114) ----------------------------------------------------
 
 assert_assemble() {