fix(fleet): 24 of the 25 "stranded" locations were merged PRs

scripts/fleet/stranded-work.sh

@@ -88,9 +88,34 @@ scan_repo() {
   # Unpushed: measured against the upstream when there is one, else against the
   # remote default branch. A branch that was never pushed is the worse case, not
   # an exempt one — that is where four of fleetcrown's commits were hiding.
-  local base unpushed_count=0 unpushed_age=-1 oldest_commit
-  if git -C "$dir" rev-parse --verify -q '@{u}' >/dev/null 2>&1; then
-    base='@{u}'
+  #
+  # But "no upstream" and "upstream gone" are opposite facts, and conflating
+  # them made this guard report the whole fleet as stranded. The fleet's normal
+  # end of life for a branch is: push, PR, squash-merge, GitHub deletes the
+  # remote branch, a later `fetch --prune` drops the tracking ref. The local
+  # branch is left with `branch.<n>.merge` still configured and nothing to
+  # resolve it to. Falling through to origin/main then counts the pre-squash
+  # commit as unpushed FOREVER — it is not reachable from main and never will
+  # be, because main got a different commit with the same content.
+  #
+  # Measured 2026-08-26: 24 of the 25 locations this reported as stranded were
+  # merged PRs. Every one. `gh pr list --state all` said MERGED for all 24, the
+  # oldest 25 days — i.e. the guard's loudest number was entirely false, and it
+  # would have stayed false for as long as those worktrees existed.
+  #
+  # A configured-but-unresolvable upstream is therefore proof the branch DID
+  # leave the machine, which is exactly what puts it out of scope: this guard
+  # looks for work GitHub cannot see. Whether that pushed branch was merged or
+  # abandoned is a question for `gh`, not for a filesystem scan.
+  local base unpushed_count=0 unpushed_age=-1 oldest_commit upstream
+  upstream="$(git -C "$dir" for-each-ref --format='%(upstream:short)' \
+    "refs/heads/$branch" 2>/dev/null)"
+  if [ -n "$upstream" ]; then
+    if git -C "$dir" rev-parse --verify -q "refs/remotes/$upstream" >/dev/null 2>&1; then
+      base="$upstream"
+    else
+      base=''          # pushed, then the remote branch was deleted — not stranded
+    fi
   elif git -C "$dir" rev-parse --verify -q origin/main >/dev/null 2>&1; then
     base='origin/main'
   elif git -C "$dir" rev-parse --verify -q origin/master >/dev/null 2>&1; then

scripts/fleet/test-stranded-work.sh

@@ -187,6 +187,70 @@ out="$(FLEET_ROOT="$wt_root" STRANDED_DAYS=3 bash "$SCRIPT" --check 2>&1)"; rc=$
   && ok "the main checkout is not re-scanned as its own worktree" \
   || no "expected exactly one withwt line (out='$out')"
 
+echo
+echo "merged branches — the false positive that made the whole report noise:"
+
+# On 2026-08-26 this guard named 25 stranded locations. Twenty-four of them were
+# MERGED PRs (`gh pr list --state all`, all 24, oldest 25 days). The mechanism:
+# the fleet squash-merges, GitHub deletes the remote branch, `fetch --prune`
+# drops the tracking ref, and the local branch keeps a `branch.*.merge` config
+# pointing at a ref that no longer resolves. The old code read that as "no
+# upstream" and fell through to origin/main, where the pre-squash commit is
+# unreachable by construction — so it counted as unpushed permanently.
+#
+# These three pin the distinction the fix turns on: upstream GONE is not
+# upstream ABSENT.
+mrepo="$TMP/merged"; mkdir -p "$mrepo"
+git init -q --bare "$TMP/merged.git"
+d="$(mkrepo_at "$TMP" merged)"
+git -C "$d" remote add origin "$TMP/merged.git"
+git -C "$d" branch -M main
+git -C "$d" push -q -u origin main
+
+git -C "$d" checkout -q -b feat/squashed
+echo work > "$d/f.txt"; git -C "$d" add -A
+GIT_COMMITTER_DATE="$(date -d '20 days ago' -Iseconds)" \
+  git -C "$d" -c user.email=t@t -c user.name=t commit -qm "merged work" \
+  --no-verify --date="$(date -d '20 days ago' -Iseconds)"
+git -C "$d" push -q -u origin feat/squashed
+# main gets the CONTENT under a different sha, exactly as a squash-merge does
+git -C "$d" push -q origin --delete feat/squashed
+git -C "$d" fetch -q --prune origin
+
+git -C "$d" config --get branch.feat/squashed.merge >/dev/null \
+  && ok "the fixture reproduces it: upstream still configured after the prune" \
+  || no "fixture is wrong — upstream config should survive a prune"
+
+line="$(scan_repo "$d")"
+u="$(printf '%s' "$line" | cut -f4)"
+[ "$u" = "0" ] \
+  && ok "a pushed-then-deleted branch is not stranded — it already left the machine" \
+  || no "merged branch must scan as 0 unpushed, got $u ('$line')"
+
+# The other half: never pushed at all is still the worst case and must fire.
+git -C "$d" checkout -q -b feat/never-pushed main
+echo other > "$d/g.txt"; git -C "$d" add -A
+GIT_COMMITTER_DATE="$(date -d '20 days ago' -Iseconds)" \
+  git -C "$d" -c user.email=t@t -c user.name=t commit -qm "real stranded work" \
+  --no-verify --date="$(date -d '20 days ago' -Iseconds)"
+line="$(scan_repo "$d")"
+u="$(printf '%s' "$line" | cut -f4)"; uage="$(printf '%s' "$line" | cut -f5)"
+[ "$u" = "1" ] && [ "$uage" -ge 19 ] \
+  && ok "a branch that never had an upstream still counts (${uage}d)" \
+  || no "never-pushed work must still be found, got u=$u age=$uage"
+
+# And a live upstream still measures against itself, not the default branch.
+git -C "$d" push -q -u origin feat/never-pushed
+echo more >> "$d/g.txt"; git -C "$d" add -A
+GIT_COMMITTER_DATE="$(date -d '20 days ago' -Iseconds)" \
+  git -C "$d" -c user.email=t@t -c user.name=t commit -qm "ahead of upstream" \
+  --no-verify --date="$(date -d '20 days ago' -Iseconds)"
+line="$(scan_repo "$d")"
+u="$(printf '%s' "$line" | cut -f4)"
+[ "$u" = "1" ] \
+  && ok "a resolvable upstream is measured against, not origin/main" \
+  || no "expected 1 commit ahead of upstream, got $u ('$line')"
+
 echo
 echo "end to end:"