diff --git a/docs/roadmaps/entries/PMAT-5843.yaml b/docs/roadmaps/entries/PMAT-5843.yaml
new file mode 100644
index 0000000000..252e4b79a5
--- /dev/null
+++ b/docs/roadmaps/entries/PMAT-5843.yaml
@@ -0,0 +1,19 @@
+- id: PMAT-5843
+  github_issue: 5843
+  item_type: task
+  title: 'MQ feeder: every 5 min enqueue the oldest green non-draft PR when the merge queue is empty'
+  status: planned
+  priority: high
+  assigned_to: null
+  created: 2026-10-21T10:55:00Z
+  updated: 2026-10-21T10:55:00Z
+  spec: null
+  acceptance_criteria:
+  - 'scripts/mq_feeder.sh --self-test green; timer live; kicked PRs re-read at 30s and skipped'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 5510
diff --git a/docs/roadmaps/entries/PMAT-5846.yaml b/docs/roadmaps/entries/PMAT-5846.yaml
new file mode 100644
index 0000000000..e0f6dd5bc1
--- /dev/null
+++ b/docs/roadmaps/entries/PMAT-5846.yaml
@@ -0,0 +1,19 @@
+- id: PMAT-5846
+  github_issue: 5846
+  item_type: task
+  title: 'arm_pr_automerge.sh: stale guard-tree check name (default must be x86-main)'
+  status: planned
+  priority: high
+  assigned_to: null
+  created: 2026-10-21T10:13:29Z
+  updated: 2026-10-21T10:13:29Z
+  spec: null
+  acceptance_criteria:
+  - 'default GUARD_CHECK_NAME names a check run that exists on PR heads; --self-test fixtures updated'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 5510
diff --git a/docs/roadmaps/roadmap.yaml b/docs/roadmaps/roadmap.yaml
index 5530309f23..fd9b5d5d2c 100644
--- a/docs/roadmaps/roadmap.yaml
+++ b/docs/roadmaps/roadmap.yaml
@@ -25359,6 +25359,44 @@ Not done, pending the ruling: moving the 31 fixture files to an obviously synthe
   - kind:code
   notes: null
   epic: 5510
+- id: PMAT-5843
+  github_issue: 5843
+  item_type: task
+  title: 'MQ feeder: every 5 min enqueue the oldest green non-draft PR when the merge queue is empty'
+  status: planned
+  priority: high
+  assigned_to: null
+  created: 2026-10-21T10:55:00Z
+  updated: 2026-10-21T10:55:00Z
+  spec: null
+  acceptance_criteria:
+  - 'scripts/mq_feeder.sh --self-test green; timer live; kicked PRs re-read at 30s and skipped'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 5510
+- id: PMAT-5846
+  github_issue: 5846
+  item_type: task
+  title: 'arm_pr_automerge.sh: stale guard-tree check name (default must be x86-main)'
+  status: planned
+  priority: high
+  assigned_to: null
+  created: 2026-10-21T10:13:29Z
+  updated: 2026-10-21T10:13:29Z
+  spec: null
+  acceptance_criteria:
+  - 'default GUARD_CHECK_NAME names a check run that exists on PR heads; --self-test fixtures updated'
+  phases: []
+  subtasks: []
+  estimated_effort: null
+  labels:
+  - kind:code
+  notes: null
+  epic: 5510
 - id: PMAT-5873
   github_issue: 5873
   item_type: task
diff --git a/scripts/mq_feeder.sh b/scripts/mq_feeder.sh
new file mode 100755
index 0000000000..931983a68e
--- /dev/null
+++ b/scripts/mq_feeder.sh
@@ -0,0 +1,179 @@
+#!/usr/bin/env bash
+# mq_feeder.sh -- PMAT-5843. If the merge queue on main is EMPTY, enqueue the oldest green non-draft PR
+# through scripts/arm_pr_automerge.sh and post one line to the cop inbox. Run by a local systemd user timer
+# every 5 min (not a workflow). Operator, verbatim (10:29Z): "a job checks MQ every 5 min; if empty, it
+# enqueues the oldest green non-draft PR (arm_pr_automerge.sh) and posts to the cop inbox. Reversible, 2 h window."
+# Gotcha: on a CLEAN PR `gh pr merge --squash --auto` prints "merge strategy is set by the merge queue" and
+# does nothing; arm_pr_automerge.sh uses plain `gh pr merge`. This script then READS mergeQueueEntry back.
+# Kill switch: touch "$STATE/disabled" (or `systemctl --user disable --now mq-feeder.timer`).
+# Usage: mq_feeder.sh [--dry-run] | --self-test        Exit: 0 ok/noop, 2 ENV
+set -uo pipefail
+REPO="${MQ_FEEDER_REPO:-paiml/aprender}"
+STATE="${MQ_FEEDER_STATE:-${XDG_STATE_HOME:-$HOME/.local/state}/mq-feeder}"
+INBOX="${MQ_FEEDER_INBOX:-/mnt/nvme-raid0/cop-inbox/inbox.md}"
+ARM="${MQ_FEEDER_ARM:-$(dirname "$0")/arm_pr_automerge.sh}"
+# guard-tree is a section inside x86-main, not a check run on PR heads (arm_pr_automerge.sh refused every PR as "absent"): judge x86-main
+export GUARD_CHECK_NAME="${GUARD_CHECK_NAME:-x86-main}"
+TRIES="${MQ_FEEDER_TRIES:-3}"
+dry=0
+Q='query($o:String!,$n:String!){repository(owner:$o,name:$n){mergeQueue(branch:"main"){entries(first:1){totalCount}} pullRequests(states:OPEN,first:100,orderBy:{field:CREATED_AT,direction:ASC}){nodes{number isDraft baseRefName mergeStateStatus autoMergeRequest{enabledAt} mergeQueueEntry{position}}}}}'
+# candidates JSON -> "QUEUE_BUSY" | one PR number per line, oldest first (CLEAN, non-draft, base main, not armed, not queued)
+pick() {
+  jq -r '.data.repository as $r
+    | if ($r.mergeQueue.entries.totalCount // 0) > 0 then "QUEUE_BUSY"
+      else $r.pullRequests.nodes[] | select(.isDraft==false and .baseRefName=="main" and .mergeStateStatus=="CLEAN" and .autoMergeRequest==null and .mergeQueueEntry==null) | .number end' <<<"$1"
+}
+# gate_paths FILES -> 0 when any path is gate content (a gate change needs 2 non-author seats bound to the head).
+# Wide on purpose: every path under scripts/, ci/ and .github/ (the explicit-test fragments run arbitrary scripts) plus root build/lint config.
+gate_paths() { grep -qE '(^|/)(Cargo\.toml$|build\.rs$|\.?clippy\.toml$|deny\.toml$|rust-toolchain|\.cargo/|\.?rustfmt\.toml$|\.gitignore$|\.?codecov\.yml$)|^(\.github/|ci/|scripts/|Cargo\.toml$|Cargo\.lock$|Makefile$|rust-toolchain|\.config/nextest|\.cargo/|deny\.toml$|clippy\.toml$|\.clippy\.toml$|\.pmat-gates\.toml$)' <<<"$1"; }
+# (The request-changes word list is best-effort; the hard vetoes are the CHANGES_REQUESTED state and not arming.)
+# Review format the feeder accepts (a quorum receipt only; seats are not read). Positive anchors AT THE START OF THE BODY:
+#   quorum:  "quorum 3/3 [AGREED] PASS"    (or APPROVE/APPROVED); PASS/APPROVE is the verdict direction
+# followed ONLY by optional punctuation and an optional " @<sha>" up to the end of the body. A body with a quote mark, a negation/deferral/failure word or a
+# carried-over marker anywhere is rejected, so quoted evidence and "APPROVE once X lands" never count.
+NEG='\b(NOT|NO|NEED|NEEDS|PENDING|REQUIRED|MISSING|AWAITING|WITHOUT|UNTIL|IF|ONCE|AFTER|WHEN|UNLESS|CANNOT|FAIL|FAILS|FAILED|REJECT|REJECTED|BLOCK|BLOCKS|BLOCKING|CARRIED|PREVIOUS|EARLIER|PRIOR)\b|REQUEST[-_ ]?CHANGES|[0-2]/3|"'"'"'`'
+END='[.;:,!]?([[:space:]]+@[0-9a-f]{7,40})?[.;:,!]?[[:space:]]*$'
+# quorum_receipts REVIEWS -> count of reviews that are exactly a "quorum 3/3 [AGREED] PASS|APPROVE(D)" receipt (see above)
+quorum_receipts() {
+  grep -iE "^(COMMENTED|APPROVED)"$'\t'"quorum[: ]+3/3[ :,;-]+(AGREED[ :,;-]+)?(PASS|APPROVED?)${END}" <<<"$1" | grep -viE "$NEG" | wc -l
+}
+# needs_seats PR HEAD -> prints the skip reason and returns 0 (skip) unless the PR is NON-gate content AND holds a
+# "quorum 3/3 [AGREED] PASS" receipt review bound to HEAD with no request-changes/FAIL/BLOCKING bound to HEAD.
+# Gate-content PRs are never enqueued by the feeder (operator/arbiter arms them; 16:18Z #5849 was enqueued
+# without a receipt). FAILS CLOSED: unreadable file list or review list, or an empty HEAD, means skip.
+needs_seats() {
+  local f rv rc q
+  [ -n "$2" ] || { echo "skip (head unreadable)"; return 0; }
+  f=$(gh api "repos/$REPO/pulls/$1/files" --paginate --jq '.[]|.filename, (.previous_filename // empty)' 2>/dev/null) || { echo "skip (files unreadable)"; return 0; }
+  [ -n "$f" ] || { echo "skip (file list empty)"; return 0; }
+  gate_paths "$f" && { echo "skip (gate content: the feeder never enqueues a gate change)"; return 0; }
+  # reviews bound to HEAD (commit_id); one body per line, newlines folded
+  rv=$(gh api "repos/$REPO/pulls/$1/reviews" --paginate --jq ".[]|select(.commit_id==\"$2\" and (.state==\"COMMENTED\" or .state==\"APPROVED\" or .state==\"CHANGES_REQUESTED\"))|[.state,(.body|gsub(\"[\\n\\r]+\";\" \"))]|@tsv" 2>/dev/null) || { echo "needs seats (reviews unreadable)"; return 0; }
+  rc=$(grep -ciE '^CHANGES_REQUESTED|REQUEST[-_ ]?CHANGES|\bFAIL|\bREJECT|\bBLOCKING\b|\bBLOCKER|\bBLOCKS\b|NO[-_ ]?GO|DO[-_ ]?N(OT|.?T)[-_ ]MERGE|CHANGES[-_ ]REQUESTED' <<<"$rv")
+  q=$(quorum_receipts "$rv")
+  { [ "${rc:-0}" -eq 0 ] && [ "${q:-0}" -ge 1 ]; } && return 1
+  echo "skip (no quorum receipt at ${2:0:10}: quorum 3/3 PASS receipts $q/1, $rc request-changes)"
+}
+inbox() { mkdir -p "$STATE"; printf '%s %s\n' "$(date +%s)" "$1" >> "$STATE/acts.log"; printf '%s | %s | %s | %s\n' "$(date -u +%H:%MZ)" mq-feeder PMAT-5843 "$1" >> "$INBOX"; }
+if [ "${1:-}" = --self-test ]; then
+  fail=0
+  mk() { printf '{"data":{"repository":{"mergeQueue":{"entries":{"totalCount":%s}},"pullRequests":{"nodes":[%s]}}}}' "$1" "$2"; }
+  pr() { printf '{"number":%s,"isDraft":%s,"baseRefName":"%s","mergeStateStatus":"%s","autoMergeRequest":%s,"mergeQueueEntry":null}' "$1" "$2" "$3" "$4" "$5"; }
+  eq() { [ "$2" = "$3" ] || { echo "FAIL $1: got '$2' want '$3'"; fail=1; }; }
+  eq 'busy queue -> nothing enqueued' "$(pick "$(mk 2 "$(pr 1 false main CLEAN null)")")" QUEUE_BUSY
+  eq 'oldest clean first' "$(pick "$(mk 0 "$(pr 7 false main CLEAN null),$(pr 9 false main CLEAN null)")" | head -1)" 7
+  eq 'draft skipped' "$(pick "$(mk 0 "$(pr 7 true main CLEAN null),$(pr 9 false main CLEAN null)")" | head -1)" 9
+  eq 'BEHIND/BLOCKED/DIRTY skipped' "$(pick "$(mk 0 "$(pr 1 false main BEHIND null),$(pr 2 false main BLOCKED null),$(pr 3 false main DIRTY null)")")" ''
+  eq 'non-main base skipped' "$(pick "$(mk 0 "$(pr 4 false feat CLEAN null)")")" ''
+  eq 'already armed skipped' "$(pick "$(mk 0 "$(pr 5 false main CLEAN '{"enabledAt":"x"}')")")" ''
+  eq 'no PRs' "$(pick "$(mk 0 '')")" ''
+  gate_paths $'docs/x.md\nscripts/check_foo.sh' || { echo "FAIL gate_paths check_"; fail=1; }
+  gate_paths $'docs/x.md\ncrates/a/src/lib.rs' && { echo "FAIL gate_paths non-gate"; fail=1; }
+  for p in ci/explicit-test-commands.d/1.cmd scripts/guard_tree.sh scripts/ci_mg_reuse.sh scripts/lib/x.sh scripts/ci/x.sh scripts/mq_feeder.sh scripts/systemd/mq-feeder.service Cargo.toml Makefile ci/vendor/sovereign-ci.yml; do gate_paths "$p" || { echo "FAIL gate_paths $p"; fail=1; }; done
+  # gate_paths: scripts the explicit-test fragments run are gate content (triage 38b290a66f)
+  for p in scripts/contracts_gate.sh scripts/mutate_foo_guard.sh scripts/lib_baseline_ratchet.sh scripts/pv_bin.sh scripts/pmat_bin.sh scripts/tests/x.sh; do gate_paths "$p" || { echo "FAIL gate_paths $p"; fail=1; }; done
+  # needs_seats with a stubbed gh: REVIEWS is "STATE<TAB>body" lines, FILES the PR file list
+  # FILES lines are "name" or "name<TAB>previous_name"; the stub feeds them through the REAL --jq filter, so the filter is under test
+  gh() { case "$2" in */files) [ "${CASE:-}" = filefail ] && return 1; local flt=; while [ $# -gt 0 ]; do [ "$1" = --jq ] && flt=$2; shift; done
+      printf '%s\n' "${FILES:-docs/x.md}" | jq -Rn '[inputs|split("\t")|{filename:.[0]}+(if length>1 then {previous_filename:.[1]} else {} end)]' | jq -r "$flt";;
+    */reviews) printf '%b' "${REVIEWS:-}";; esac; }
+  ns() { REPO=r needs_seats 1 H >/dev/null; echo $?; }   # 0 = skip (not armable), 1 = armable
+  Q3='COMMENTED\tquorum 3/3 AGREED PASS\n'
+  eq 'receipt on a non-gate PR -> armable' "$(REVIEWS="$Q3" ns)" 1
+  eq 'no receipt (non-gate PR) -> skip' "$(REVIEWS='' ns)" 0
+  eq 'two seats but no receipt -> skip' "$(REVIEWS='COMMENTED\tseat w1 APPROVE\nCOMMENTED\tseat w2 APPROVE\n' ns)" 0
+  eq 'gate content + receipt -> skip (never enqueued by the feeder)' "$(FILES=scripts/x.sh REVIEWS="$Q3" ns)" 0
+  eq 'gate content among docs + receipt -> skip' "$(FILES=$'docs/x.md\n.github/workflows/ci.yml' REVIEWS="$Q3" ns)" 0
+  eq 'files unreadable -> skip (fail closed)' "$(CASE=filefail REVIEWS="$Q3" ns)" 0
+  eq 'receipt + request-changes at head -> skip' "$(REVIEWS="${Q3}CHANGES_REQUESTED\tseat w3 RC\n" ns)" 0
+  eq 'receipt + FAIL review at head -> skip' "$(REVIEWS="${Q3}COMMENTED\tseat w3 FAIL\n" ns)" 0
+  eq 'rename OUT of a gate path + receipt -> skip (previous_filename)' "$(FILES=$'docs/old_guard.sh\tscripts/check_guard.sh' REVIEWS="$Q3" ns)" 0
+  eq 'plain non-gate rename + receipt -> armable' "$(FILES=$'docs/b.md\tdocs/a.md' REVIEWS="$Q3" ns)" 1
+  for p in rustfmt.toml .rustfmt.toml .gitignore codecov.yml build.rs crates/foo/Cargo.toml crates/foo/build.rs; do
+    eq "gate path $p + receipt -> skip" "$(FILES=$p REVIEWS="$Q3" ns)" 0
+  done
+  for r in 'seat w3 BLOCKER' 'NO-GO' 'seat w3 BLOCKS' 'DO NOT MERGE'; do
+    eq "review '$r' at head -> skip" "$(REVIEWS="${Q3}COMMENTED\t$r\n" ns)" 0
+  done
+  for p in crates/foo/.clippy.toml crates/foo/clippy.toml crates/foo/deny.toml crates/foo/rust-toolchain.toml crates/foo/.cargo/config.toml; do
+    eq "gate path $p + receipt -> skip" "$(FILES=$p REVIEWS="$Q3" ns)" 0
+  done
+  for r in 'changes-requested' 'changes_requested' 'do_not_merge' 'NO_GO' 'do-not-merge' 'NO GO' "don't merge" 'changes requested' 'do not merge'; do
+    eq "review '$r' at head -> skip" "$(REVIEWS="${Q3}COMMENTED\t$r\n" ns)" 0
+  done
+  eq 'receipt "quorum 3/3 APPROVED" -> armable' "$(REVIEWS='COMMENTED\tquorum 3/3 APPROVED\n' ns)" 1
+  eq 'receipt with trailing @sha -> armable' "$(REVIEWS='COMMENTED\tquorum 3/3 AGREED PASS @abcdef1234\n' ns)" 1
+  eq 'receipt with punctuation -> armable' "$(REVIEWS='COMMENTED\tquorum 3/3 AGREED PASS.\n' ns)" 1
+  eq 'receipt with punctuation then @sha -> armable' "$(REVIEWS='COMMENTED\tquorum 3/3 AGREED PASS. @abcdef1234\n' ns)" 1
+  for q in 'quorum 3/3 pending' 'quorum 3/3 required' 'quorum 3/3 missing' 'need quorum 3/3' 'AGREED 3/3' 'quorum 3/3' 'quorum NOT 3/3' 'quorum 2/3 AGREED PASS' \
+      'quorum 3/3 AGREED: FAIL (B1 blocks)' 'quorum 3/3 AGREED to reject' 'quorum 3/3 AGREED on 2 BLOCKING findings' 'quorum 3/3 AGREED?' 'quorum 3/3 AGREED cannot arm yet' \
+      'quorum 3/3 REJECT' 'quorum 3/3 PASS, if seats' 'quorum 3/3 PASS; cannot arm' 'quorum 3/3 PASS the following' 'quorum 3/3 PASS. Nothing was verified by me' \
+      'quorum 3/3 PASS @abcdef1234 (RC on a later head)' 'carried from round 3: quorum 3/3 PASS' 'quorum 3/3 PASS once B1 lands' 'see quorum 3/3 PASS above' 'on "quorum 3/3 PASS" pasted evidence' 'quorum 3/3 PASS but FAIL'; do
+    eq "row '$q' is not a receipt" "$(REVIEWS="COMMENTED\t$q\n" ns)" 0
+  done
+  unset -f gh
+  # subprocess: the whole feeder against a stub gh and a stub ARM. REFUSE (rc 3), a missing receipt and gate content must NEVER
+  # call ARM or post "enqueued"; an ARM rc 0 control with a receipt does enqueue (proves the harness can see an enqueue).
+  d=$(mktemp -d) || exit 2
+  cat > "$d/gh" <<'GHEOF'
+#!/usr/bin/env bash
+case "$*" in
+  *rate_limit*) echo 5000;;
+  *"mergeQueue(branch"*) printf '{"data":{"repository":{"mergeQueue":{"entries":{"totalCount":0}},"pullRequests":{"nodes":[{"number":7,"isDraft":false,"baseRefName":"main","mergeStateStatus":"CLEAN","autoMergeRequest":null,"mergeQueueEntry":null}]}}}}';;
+  *graphql*) echo QUEUED;;
+  "pr view"*) echo deadbeefdeadbeef;;
+  */files*) printf '%s\n' "$T_FILES";;
+  */reviews*) printf '%b' "$T_REVIEWS";;
+  */commits*) echo 0;;
+esac
+GHEOF
+  printf '#!/usr/bin/env bash\necho "$1" >> "$T_MARK"\n[ "$T_ARMRC" = 3 ] && echo "refuse: guard check not green"\nexit "$T_ARMRC"\n' > "$d/arm"
+  chmod +x "$d/gh" "$d/arm"
+  run_feeder() { rm -f "${d:?}/mark" "${d:?}/inbox" "${d:?}/st/kicked"; : > "$d/inbox"
+    T_FILES=$1 T_REVIEWS=$2 T_ARMRC=$3 T_MARK="$d/mark" PATH="$d:$PATH" MQ_FEEDER_STATE="$d/st" MQ_FEEDER_INBOX="$d/inbox" MQ_FEEDER_ARM="$d/arm" MQ_FEEDER_RECHECK=0 bash "$0" >/dev/null 2>&1
+    echo "armed=$([ -e "$d/mark" ] && echo yes || echo no) enq=$(grep -c 'enqueued oldest' "$d/inbox")"; }
+  eq 'feeder: REFUSE (arm rc 3) with a receipt never enqueues' "$(run_feeder docs/x.md "$Q3" 3)" 'armed=yes enq=0'
+  eq 'feeder: no receipt never calls ARM' "$(run_feeder docs/x.md '' 0)" 'armed=no enq=0'
+  eq 'feeder: gate content with a receipt never calls ARM' "$(run_feeder scripts/x.sh "$Q3" 0)" 'armed=no enq=0'
+  eq 'feeder: request-changes at head never calls ARM' "$(run_feeder docs/x.md "${Q3}CHANGES_REQUESTED\tx\n" 0)" 'armed=no enq=0'
+  eq 'feeder control: receipt + ARM rc 0 enqueues' "$(run_feeder docs/x.md "$Q3" 0)" 'armed=yes enq=1'
+  rm -rf "${d:?}"
+  [ "$fail" -eq 0 ] && echo "ok: self-test"; exit "$fail"
+fi
+[ "${1:-}" = --dry-run ] && dry=1
+if [ "${1:-}" = --summary ]; then
+  mkdir -p "$STATE"; since=$(($(date +%s) - 3600))  # bashrs disable-line=DET002 (runtime window, not a build stamp)
+  t=$(awk -v s="$since" '$1>=s' "$STATE/ticks.log" 2>/dev/null | wc -l); e=$(awk -v s="$since" '$1>=s && /enqueued oldest/' "$STATE/acts.log" 2>/dev/null | wc -l); k=$(awk -v s="$since" '$1>=s && /KICKED/' "$STATE/acts.log" 2>/dev/null | wc -l)
+  inbox "summary 1h: $t ticks, $e enqueued, $k kicked"; exit 0
+fi
+mkdir -p "$STATE" || exit 2
+[ -x "$ARM" ] || { inbox "mq-feeder: arm script $ARM missing or not executable (install both scripts with scripts/mq_feeder_install.sh)"; exit 2; }
+[ -e "$STATE/disabled" ] && exit 0
+date +%s >> "$STATE/ticks.log"
+rem=$(gh api rate_limit --jq .resources.graphql.remaining 2>/dev/null) || exit 2
+[ "${rem:-0}" -ge 500 ] || exit 0
+json=$(gh api graphql -f query="$Q" -f o="${REPO%/*}" -f n="${REPO#*/}" 2>/dev/null) || exit 2
+cands=$(pick "$json") || exit 2
+[ "$cands" = QUEUE_BUSY ] && exit 0
+[ -n "$cands" ] || exit 0
+n=0 why=""
+for pr in $cands; do
+  head=$(gh pr view "$pr" --repo "$REPO" --json headRefOid --jq .headRefOid 2>/dev/null || true)
+  grep -qx "$pr $head" "$STATE/kicked" 2>/dev/null && continue   # kicked at THIS head: a pushed fix is a new head and clears it
+  n=$((n + 1)); [ "$n" -le "$TRIES" ] || break
+  if r=$(needs_seats "$pr" "$head"); then why="$why #$pr: $r;"; printf '%s skip #%s %s\n' "$(date +%s)" "$pr" "$r" >> "$STATE/acts.log"; continue; fi
+  mc=$(gh api "repos/$REPO/pulls/$pr/commits" --paginate --jq '[.[]|select((.parents|length)>1)]|length' 2>/dev/null | paste -sd+ | bc 2>/dev/null || true)
+  if [ "${mc:-0}" -gt 0 ] 2>/dev/null; then r="has $mc merge commit(s); REBASE needs clean commits (operator 07:57Z)"; why="$why #$pr: $r;"; printf '%s skip #%s %s\n' "$(date +%s)" "$pr" "$r" >> "$STATE/acts.log"; continue; fi
+  if [ "$dry" = 1 ]; then echo "would arm #$pr"; exit 0; fi
+  out=$(bash "$ARM" "$pr" 2>&1); rc=$?
+  if [ "$rc" -eq 0 ]; then
+    sleep "${MQ_FEEDER_RECHECK:-30}"
+    st=$(gh api graphql -f query='query($o:String!,$n:String!,$p:Int!){repository(owner:$o,name:$n){pullRequest(number:$p){state mergeQueueEntry{position} timelineItems(last:3,itemTypes:[REMOVED_FROM_MERGE_QUEUE_EVENT]){nodes{... on RemovedFromMergeQueueEvent{reason createdAt}}}}}}' -f o="${REPO%/*}" -f n="${REPO#*/}" -F p="$pr" --jq '.data.repository.pullRequest | if .state=="MERGED" then "merged" elif .mergeQueueEntry then "queued pos \(.mergeQueueEntry.position)" else "KICKED: \(.timelineItems.nodes[-1].reason // "unknown")" end' 2>/dev/null || echo unread)
+    case "$st" in KICKED*) echo "$pr $head" >> "$STATE/kicked"; inbox "queue was empty: enqueued #$pr, then $st within ${MQ_FEEDER_RECHECK:-30}s; skipped at this head until a new push" ;; *) inbox "queue was empty: enqueued oldest green PR #$pr ($st)" ;; esac
+    exit 0
+  fi
+  if [ "$rc" -eq 3 ]; then why="$why #$pr: $(printf '%s' "$out" | grep -m1 -E "^refuse" | cut -c1-110);"; printf '%s skip #%s %s\n' "$(date +%s)" "$pr" "$(printf '%s' "$out" | grep -m1 -E "^refuse" | cut -c1-110)" >> "$STATE/acts.log"; continue; fi
+  inbox "queue empty, arm of #$pr failed rc=$rc: $(printf '%s' "$out" | tail -n 1 | cut -c1-120)"; exit 0
+done
+inbox "queue empty, no PR enqueued: $((n > TRIES ? TRIES : n)) CLEAN candidate(s) refused:$why"
+exit 0
diff --git a/scripts/mq_feeder_install.sh b/scripts/mq_feeder_install.sh
new file mode 100755
index 0000000000..f31a843ce4
--- /dev/null
+++ b/scripts/mq_feeder_install.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+# mq_feeder_install.sh -- PMAT-5843. Install the feeder AND the arm script it calls into the path the user units run
+# (%h/.local/libexec/mq-feeder). The feeder resolves arm_pr_automerge.sh next to itself, so both must be there.
+# Run from a checkout of origin/main; re-run after either script changes (forjar converges the same files on the hosts).
+# Usage: mq_feeder_install.sh [DEST]
+set -euo pipefail
+src="$(cd "$(dirname "$0")" && pwd)"
+dest="${1-$HOME/.local/libexec/mq-feeder}"
+# SEC010 (bashrs): the install target is an argument, so it must be absolute (so an explicit empty arg is refused too) and free of `..`.
+case "$dest" in
+  /*) ;;
+  *) echo "mq_feeder_install: DEST must be an absolute path, got '$dest'" >&2; exit 2 ;;
+esac
+case "/$dest/" in
+  */../*) echo "mq_feeder_install: DEST must not contain '..': $dest" >&2; exit 2 ;;
+esac
+mkdir -p "$dest"
+for s in mq_feeder.sh arm_pr_automerge.sh; do
+  install -m 0755 "$src/$s" "$dest/$s"
+done
+sha256sum "$dest/mq_feeder.sh" "$dest/arm_pr_automerge.sh" > "$dest/INSTALLED.sha256"
+echo "installed to $dest"
diff --git a/scripts/systemd/mq-feeder-summary.service b/scripts/systemd/mq-feeder-summary.service
new file mode 100644
index 0000000000..077884f34d
--- /dev/null
+++ b/scripts/systemd/mq-feeder-summary.service
@@ -0,0 +1,5 @@
+[Unit]
+Description=mq-feeder hourly summary line (PMAT-5843)
+[Service]
+Type=oneshot
+ExecStart=%h/.local/libexec/mq-feeder/mq_feeder.sh --summary
diff --git a/scripts/systemd/mq-feeder-summary.timer b/scripts/systemd/mq-feeder-summary.timer
new file mode 100644
index 0000000000..2048dcc0f7
--- /dev/null
+++ b/scripts/systemd/mq-feeder-summary.timer
@@ -0,0 +1,6 @@
+[Unit]
+Description=mq-feeder summary at :45
+[Timer]
+OnCalendar=*:45:00
+[Install]
+WantedBy=timers.target
diff --git a/scripts/systemd/mq-feeder.service b/scripts/systemd/mq-feeder.service
new file mode 100644
index 0000000000..14af345c30
--- /dev/null
+++ b/scripts/systemd/mq-feeder.service
@@ -0,0 +1,5 @@
+[Unit]
+Description=mq-feeder: enqueue the oldest green PR when the merge queue is empty (PMAT-5843)
+[Service]
+Type=oneshot
+ExecStart=%h/.local/libexec/mq-feeder/mq_feeder.sh
diff --git a/scripts/systemd/mq-feeder.timer b/scripts/systemd/mq-feeder.timer
new file mode 100644
index 0000000000..98b888a67b
--- /dev/null
+++ b/scripts/systemd/mq-feeder.timer
@@ -0,0 +1,8 @@
+[Unit]
+Description=mq-feeder tick, every 5 min (PMAT-5843)
+[Timer]
+OnBootSec=2min
+OnUnitActiveSec=5min
+AccuracySec=10s
+[Install]
+WantedBy=timers.target