test/changelog-assembled.test.sh

@@ -217,6 +217,49 @@ check "a surviving fragment with its entry present fails" 1 "STILL PRESENT" \
 check "the survivor refusal names the file" 1 "changelog.d/9.md" \
   run survivor base
 
+# A release PR can be faithful to its merge base while the target branch moves
+# ahead and gains a fragment during review. That target-only fragment was not
+# available to the ceremony, so merging the PR would strand it for the next
+# release. The guard must read the target ref as well as their merge base.
+seed_flat target-stranded
+ceremony target-stranded 0.2.0 2026-07-24
+commit_head target-stranded
+git -C "$TMP/target-stranded" switch -q base
+printf -- '- Landed while the release was under review (#30).\n' \
+  >"$TMP/target-stranded/changelog.d/30.md"
+git -C "$TMP/target-stranded" add -A
+git -C "$TMP/target-stranded" commit -qm target-fragment
+git -C "$TMP/target-stranded" switch -q main
+check "a target-head fragment the release did not consume fails" 1 \
+  "changelog.d/30.md" run target-stranded base
+check "the target-stranding refusal names the rebase remedy" 1 \
+  "rebase onto the target head" run target-stranded base
+check "the target-stranding refusal names the assembler re-run" 1 \
+  "changelog-assemble '0.2.0'" run target-stranded base
+
+# Removing the target-only fragment makes the same diverged fixture green:
+# target drift itself is not the failure, only a stranded fragment is.
+git -C "$TMP/target-stranded" switch -q base
+rm "$TMP/target-stranded/changelog.d/30.md"
+git -C "$TMP/target-stranded" add -A
+git -C "$TMP/target-stranded" commit -qm target-fragment-removed
+git -C "$TMP/target-stranded" switch -q main
+check "the same target fixture is green once no fragment is stranded" 0 \
+  "byte-for-byte" run target-stranded base
+
+# Spell out the common harmless case independently: the target branch moved,
+# but the advancing commit added no fragment.
+seed_flat target-unrelated
+ceremony target-unrelated 0.2.0 2026-07-24
+commit_head target-unrelated
+git -C "$TMP/target-unrelated" switch -q base
+printf 'unrelated target change\n' >"$TMP/target-unrelated/code.txt"
+git -C "$TMP/target-unrelated" add -A
+git -C "$TMP/target-unrelated" commit -qm target-unrelated
+git -C "$TMP/target-unrelated" switch -q main
+check "a target head advanced without a fragment stays green" 0 \
+  "byte-for-byte" run target-unrelated base
+
 # Fragments consumed, section never stamped: the prose went nowhere.
 seed_flat halfdone
 rm "$TMP/halfdone/changelog.d/12.md" "$TMP/halfdone/changelog.d/9.md"