diff --git a/bin/fm-backlog-handoff.sh b/bin/fm-backlog-handoff.sh
index 882be0b367f..6e345589387 100755
--- a/bin/fm-backlog-handoff.sh
+++ b/bin/fm-backlog-handoff.sh
@@ -61,8 +61,10 @@
 # original batch is retried, so it cannot discard wake intent for work that
 # already moved. No two-phase journal exists.
 # Every newly durable backlog delivery attempts one marked wake to the receiving
-# endpoint. A local route moves directly into the destination backlog, and a
-# missing or rejected local wake makes that command fail with the move intact so
+# endpoint, naming the routed item keys; a remote batch that reuses a
+# still-pending wake adds its keys to that wake's list. A local route moves
+# directly into the destination backlog, and a missing or rejected local wake
+# makes that command fail with the move intact so
 # rerunning the same handoff retries its prepared wake intent. After a durable
 # remote receipt, the outbox is released and the handoff succeeds regardless of
 # the best-effort wake outcome; an undelivered remote wake remains separately
@@ -97,6 +99,80 @@ MAIN_BACKLOG="$DATA/backlog.md"
 
 RECEIVER_WAKE_MESSAGE='New routed work is in your backlog. Run bin/fm-session-start.sh now, then act on the routed task.'
 
+# Names the routed item keys so a receiver can tell a second genuine handoff
+# apart from a duplicate of the first; an unlabeled fixed line once made a
+# receiver block on a real second handoff as an unproven repeat (regression:
+# test_two_consecutive_handoffs_name_their_own_items in
+# tests/fm-backlog-handoff.test.sh). Appended, never inserted, so the fixed
+# sentence itself stays a stable substring for every existing caller and test
+# that greps for it.
+receiver_wake_message() {  # <item-key>...
+  local ids
+  [ "$#" -gt 0 ] || { printf '%s' "$RECEIVER_WAKE_MESSAGE"; return; }
+  ids=$(printf '%s, ' "$@")
+  ids=${ids%, }
+  printf '%s Routed: %s.' "$RECEIVER_WAKE_MESSAGE" "$ids"
+}
+
+# Extracts every item key from a "- [ ] <key> - <title>" backlog/outbox line,
+# in file order, one per line - the same line shape outbox_item_count counts.
+receiver_wake_item_keys_from_file() {  # <path>
+  grep -E '^- \[[ x]\] ' "$1" 2>/dev/null | sed -E 's/^- \[[ x]\] ([^ ]+) .*/\1/'
+}
+
+receiver_wake_message_path() {  # <secondmate-id>
+  printf '%s\n' "$STATE/.backlog-handoff-$1.wake-message"
+}
+
+receiver_wake_message_write() {  # <secondmate-id> <message>
+  local id=$1 message=$2 path tmp
+  path=$(receiver_wake_message_path "$id")
+  tmp=$(umask 077; mktemp "$STATE/.backlog-handoff-wake-message.XXXXXX") || return 1
+  if ! printf '%s' "$message" > "$tmp" || ! chmod 600 "$tmp" || ! mv -f -- "$tmp" "$path"; then
+    rm -f -- "$tmp"
+    return 1
+  fi
+}
+
+# Falls back to the fixed generic line when no per-batch message was ever
+# recorded (a legacy marker predating this, or the bare-`pending` transition
+# in wake_pending_secondmate_receiver, which has no fresh key list to work
+# from) so a receiver is never left without an actionable instruction.
+receiver_wake_message_read() {  # <secondmate-id>
+  local path
+  path=$(receiver_wake_message_path "$1")
+  if [ -f "$path" ] && [ ! -L "$path" ]; then
+    cat "$path"
+  else
+    printf '%s' "$RECEIVER_WAKE_MESSAGE"
+  fi
+}
+
+receiver_wake_message_clear() {  # <secondmate-id>
+  rm -f -- "$(receiver_wake_message_path "$1")"
+}
+
+# A still-pending wake that a later batch reuses must name every item routed
+# since it was recorded, so the new keys are merged into the stored list. A
+# stored generic line names no items and is left as it is.
+receiver_wake_message_add_keys() {  # <secondmate-id> <item-key>...
+  local id=$1 prefix="$RECEIVER_WAKE_MESSAGE Routed: " message key
+  local -a keys=()
+  shift
+  message=$(receiver_wake_message_read "$id")
+  case "$message" in "$prefix"*.) ;; *) return 0 ;; esac
+  message=${message#"$prefix"}
+  message=${message%.}
+  while [ -n "$message" ]; do
+    keys+=("${message%%, *}")
+    case "$message" in *", "*) message=${message#*, } ;; *) message= ;; esac
+  done
+  for key in "$@"; do
+    case " ${keys[*]} " in *" $key "*) ;; *) keys+=("$key") ;; esac
+  done
+  receiver_wake_message_write "$id" "$(receiver_wake_message "${keys[@]}")"
+}
+
 ACTIVE_HANDOFF_LOCK=
 ACTIVE_REGISTRY_LOCK=
 RECEIVER_WAKE_IGNORE_ID=
@@ -384,8 +460,9 @@ receiver_wake_state_write() { # <secondmate-id> <state>
   fi
 }
 
-receiver_wake_mark() { # <secondmate-id> <prepared|pending> [batch-id]
-  local id=$1 wake_phase=$2 batch=${3:-} marker="$STATE/.backlog-handoff-$1.wake-pending" value corr rec
+receiver_wake_mark() { # <secondmate-id> <prepared|pending> [batch-id] [message]
+  local id=$1 wake_phase=$2 batch=${3:-} message=${4:-$RECEIVER_WAKE_MESSAGE}
+  local marker="$STATE/.backlog-handoff-$1.wake-pending" value corr rec
   local wake_state
   case "$wake_phase" in prepared | pending) ;; *) return 1 ;; esac
   if [ -e "$marker" ] || [ -L "$marker" ]; then
@@ -408,7 +485,11 @@ receiver_wake_mark() { # <secondmate-id> <prepared|pending> [batch-id]
     *) return 1 ;;
     esac
   fi
-  corr=$(fm_pending_reply_create "$FM_HOME" "$STATE" "$id" "$RECEIVER_WAKE_MESSAGE") || return 1
+  corr=$(fm_pending_reply_create "$FM_HOME" "$STATE" "$id" "$message") || return 1
+  if ! receiver_wake_message_write "$id" "$message"; then
+    fm_pending_reply_discard_undelivered "$STATE" "$corr" || true
+    return 1
+  fi
   wake_state="$wake_phase:$corr"
   if [ "$wake_phase" = prepared ]; then
     printf '%s' "$batch" | grep -Eq '^[a-f0-9]{16}$' || return 1
@@ -416,16 +497,17 @@ receiver_wake_mark() { # <secondmate-id> <prepared|pending> [batch-id]
   fi
   if ! receiver_wake_state_write "$id" "$wake_state"; then
     fm_pending_reply_discard_undelivered "$STATE" "$corr" || true
+    receiver_wake_message_clear "$id"
     return 1
   fi
 }
 
-receiver_wake_mark_pending() { # <secondmate-id>
-  receiver_wake_mark "$1" pending
+receiver_wake_mark_pending() { # <secondmate-id> [message]
+  receiver_wake_mark "$1" pending "" "${2:-$RECEIVER_WAKE_MESSAGE}"
 }
 
-receiver_wake_mark_prepared() { # <secondmate-id> <batch-id>
-  receiver_wake_mark "$1" prepared "$2"
+receiver_wake_mark_prepared() { # <secondmate-id> <batch-id> [message]
+  receiver_wake_mark "$1" prepared "$2" "${3:-$RECEIVER_WAKE_MESSAGE}"
 }
 
 receiver_wake_discard_prepared() { # <secondmate-id>
@@ -440,6 +522,7 @@ receiver_wake_discard_prepared() { # <secondmate-id>
   *) return 1 ;;
   esac
   fm_pending_reply_discard_undelivered "$STATE" "$corr" || return 1
+  receiver_wake_message_clear "$id"
   rm -f -- "$marker"
 }
 
@@ -470,6 +553,7 @@ receiver_wake_discard_pending() { # <secondmate-id>
   pending) ;;
   *) return 1 ;;
   esac
+  receiver_wake_message_clear "$id"
   rm -f -- "$marker"
 }
 
@@ -535,6 +619,7 @@ receiver_wake_clear_confirmed() { # <secondmate-id>
     return 0
   fi
   if receiver_wake_pending_delivered_valid "$id" || receiver_wake_confirmed_valid "$id"; then
+    receiver_wake_message_clear "$id"
     if ! rm -f -- "$marker"; then
       RECEIVER_WAKE_IGNORE_ID=$id
       printf 'warning: confirmed receiver wake left a stale marker at %s; later handoffs will ignore it\n' "$marker" >&2
@@ -548,7 +633,7 @@ receiver_wake_clear_confirmed() { # <secondmate-id>
 }
 
 wake_secondmate_receiver() { # <secondmate-id> <correlation-id>
-  local id=$1 corr=$2 meta="$STATE/$1.meta" out rc=0
+  local id=$1 corr=$2 meta="$STATE/$1.meta" out rc=0 message
   if [ ! -f "$meta" ] || [ -L "$meta" ]; then
     printf 'error: handed off work to secondmate %s, but no live receiver endpoint is recorded; the destination backlog is durable and the receiver was not woken\n' "$id" >&2
     return 1
@@ -557,9 +642,10 @@ wake_secondmate_receiver() { # <secondmate-id> <correlation-id>
     printf 'error: secondmate %s has non-secondmate endpoint metadata; backlog is durable but the receiver was not woken\n' "$id" >&2
     return 1
   }
+  message=$(receiver_wake_message_read "$id")
   out=$(FM_HOME="$FM_HOME" FM_STATE_OVERRIDE="$STATE" FM_ROOT_OVERRIDE="$FM_ROOT" \
     FM_PENDING_REPLY_EXISTING_CORR="$corr" \
-    "$SCRIPT_DIR/fm-send.sh" "$id" "$RECEIVER_WAKE_MESSAGE" 2>&1) || rc=$?
+    "$SCRIPT_DIR/fm-send.sh" "$id" "$message" 2>&1) || rc=$?
   if [ "$rc" -ne 0 ]; then
     [ -z "$out" ] || printf '%s\n' "$out" >&2
     printf 'error: backlog delivery to secondmate %s succeeded, but its receiver wake failed; retry a tracked remote wake with --resume-pending or a later new handoff, and retry a local wake by rerunning its handoff\n' "$id" >&2
@@ -614,6 +700,7 @@ wake_pending_secondmate_receiver() { # <secondmate-id> [retain-confirmed]
       printf 'error: receiver wake for secondmate %s was confirmed, but pending state could not be cleared\n' "$id" >&2
       return 1
     }
+    receiver_wake_message_clear "$id"
   fi
 }
 
@@ -622,7 +709,8 @@ outbox_item_count() { # <path>
 }
 
 remote_deliver_outbox() { # <secondmate-id> <outbox-path>
-  local id=$1 outbox=$2 remote_rel receive_out snapshot bytes hash generation counter counter_tmp current marker wake_rc=0 wake_state=pending
+  local id=$1 outbox=$2 remote_rel receive_out snapshot bytes hash generation counter counter_tmp current marker wake_rc=0 wake_state=pending key
+  local -a wake_keys=()
   [ -f "$outbox" ] && [ ! -L "$outbox" ] || {
     echo "error: pending outbox is unavailable or unsafe: $outbox" >&2
     return 1
@@ -700,11 +788,22 @@ remote_deliver_outbox() { # <secondmate-id> <outbox-path>
     return 1
   fi
   marker="$STATE/.backlog-handoff-$id.wake-pending"
+  # The outbox's own item lines are the batch's ground truth here, valid
+  # for the fresh-stage call and every later resume alike since resuming
+  # only ever re-reads this same durable file.
+  while IFS= read -r key; do
+    [ -n "$key" ] && wake_keys+=("$key")
+  done < <(receiver_wake_item_keys_from_file "$outbox")
   if [ "$RECEIVER_WAKE_IGNORE_ID" = "$id" ]; then
     wake_state=dropped
     wake_rc=1
-  elif ! receiver_wake_pending_valid "$id" && ! receiver_wake_confirmed_valid "$id"; then
-    receiver_wake_mark_pending "$id" || {
+  elif receiver_wake_pending_valid "$id"; then
+    receiver_wake_message_add_keys "$id" ${wake_keys[@]+"${wake_keys[@]}"} || {
+      wake_state=dropped
+      wake_rc=1
+    }
+  elif ! receiver_wake_confirmed_valid "$id"; then
+    receiver_wake_mark_pending "$id" "$(receiver_wake_message ${wake_keys[@]+"${wake_keys[@]}"})" || {
       wake_state=dropped
       wake_rc=1
     }
@@ -717,6 +816,7 @@ remote_deliver_outbox() { # <secondmate-id> <outbox-path>
     return 1
   }
   if [ "$wake_rc" -eq 0 ]; then
+    receiver_wake_message_clear "$id"
     if ! rm -f -- "$marker"; then
       RECEIVER_WAKE_IGNORE_ID=$id
       echo "warning: remote outbox and receiver wake completed, but a stale confirmed wake marker remains at $marker; later handoffs will ignore it" >&2
@@ -1048,7 +1148,7 @@ if [ -e "$WAKE_PENDING_MARKER" ] || [ -L "$WAKE_PENDING_MARKER" ]; then
     ;;
   esac
 fi
-receiver_wake_mark_prepared "$ID" "$REQUESTED_BATCH" || {
+receiver_wake_mark_prepared "$ID" "$REQUESTED_BATCH" "$(receiver_wake_message "${TO_MOVE[@]}")" || {
   echo "error: receiver wake state for secondmate $ID could not be recorded; nothing was moved" >&2
   exit 1
 }
diff --git a/bin/fm-config-inherit-lib.sh b/bin/fm-config-inherit-lib.sh
index 79ff10605c2..4fe87dbe0aa 100644
--- a/bin/fm-config-inherit-lib.sh
+++ b/bin/fm-config-inherit-lib.sh
@@ -221,6 +221,7 @@ warn_inheritable_config_error() {
 shared_captain_header_valid() {
   local src=$1 head
   head=$(sed -n '1,12p' "$src" 2>/dev/null) || return 1
+  head=$(printf '%s' "$head" | tr '\n' ' ' | tr -s '[:space:]' ' ')
   case "$head" in *main-authoritative*) ;; *) return 1 ;; esac
   case "$head" in *"read-only in secondmate homes"*) ;; *) return 1 ;; esac
   case "$head" in *"must not be edited there"*) ;; *) return 1 ;; esac
diff --git a/bin/fm-remote-inherit-push.sh b/bin/fm-remote-inherit-push.sh
index 518e849b762..aacbcf5ba8d 100755
--- a/bin/fm-remote-inherit-push.sh
+++ b/bin/fm-remote-inherit-push.sh
@@ -29,15 +29,6 @@ sha256_file() {
 file_link_count() {
   if [ "$(uname)" = Darwin ]; then /usr/bin/stat -f %l "$1" 2>/dev/null; else stat -c %h "$1" 2>/dev/null; fi
 }
-shared_captain_header_valid() {
-  local head
-  head=$(sed -n '1,12p' "$1" 2>/dev/null) || return 1
-  case "$head" in *main-authoritative*) ;; *) return 1 ;; esac
-  case "$head" in *"read-only in secondmate homes"*) ;; *) return 1 ;; esac
-  case "$head" in *"must not be edited there"*) ;; *) return 1 ;; esac
-  case "$head" in *"main firstmate"*) ;; *) return 1 ;; esac
-  case "$head" in *"marked status"*|*"document pointer"*) ;; *) return 1 ;; esac
-}
 [ "$#" -eq 2 ] || { echo "usage: fm-remote-inherit-push.sh <secondmate-id> <generation>" >&2; exit 2; }
 ID=$1
 GENERATION=$2
diff --git a/tests/fm-backlog-handoff.test.sh b/tests/fm-backlog-handoff.test.sh
index ef935ef187e..a4d6667025e 100755
--- a/tests/fm-backlog-handoff.test.sh
+++ b/tests/fm-backlog-handoff.test.sh
@@ -48,6 +48,19 @@ inbox_body_stream() { # <state-dir> <task-id>
   done
 }
 
+# One line per durable inbox record's own body (fm_task_inbox_body prints no
+# trailing newline of its own, so inbox_body_stream's concatenation is not
+# usable when a caller needs to tell one record's body apart from another's).
+inbox_bodies_by_record() { # <state-dir> <task-id>
+  local rec
+  for rec in "$1/$2.inbox"/*.msg; do
+    [ -f "$rec" ] || continue
+    bash -c '. "$1"; fm_task_inbox_body "$2"' _ \
+      "$ROOT/bin/fm-task-inbox-lib.sh" "$rec"
+    printf '\n'
+  done
+}
+
 inbox_record_count() { # <state-dir> <task-id>
   find "$1/$2.inbox" -maxdepth 1 -type f -name '*.msg' 2>/dev/null | wc -l | tr -d '[:space:]'
 }
@@ -1344,7 +1357,67 @@ EOF
   pass "registry entry without (home: ...) fails cleanly with has no home"
 }
 
+# Regression for a real 2026-08-25 incident (backlog item
+# handoff-nachricht-nennt-auftrag-nicht): the receiver's wake instruction used
+# to be one fixed line with no indication which task it named, so two
+# handoffs delivered close together were textually identical - the receiver
+# read the second as an unproven repeat of the first and blocked on it.
+test_two_consecutive_handoffs_name_their_own_items() {
+  local home="$TMP_ROOT/two-handoffs-main" sub="$TMP_ROOT/two-handoffs-sub" fakebin
+  local out1 out2 bodies first_line second_line
+  setup_homes "$home" "$sub"
+  mkdir -p "$sub/state" "$sub/data"
+  cat > "$home/data/backlog.md" <<'EOF'
+## Queued
+- [ ] postfach-uebergang-abschliessen - first routed item (repo: alpha)
+- [ ] vault-regelfragen-umsetzung - second routed item (repo: alpha)
+
+## Done
+EOF
+  printf '## Queued\n\n## Done\n' > "$sub/data/backlog.md"
+  fakebin=$(make_fake_tmux "$TMP_ROOT/two-handoffs-fake")
+  out1="$TMP_ROOT/two-handoffs-1.out"
+  out2="$TMP_ROOT/two-handoffs-2.out"
+  FM_HOME="$home" FM_ROOT_OVERRIDE="$ROOT" PATH="$fakebin:$PATH" \
+    FM_FAKE_TMUX_WINDOW='firstmate:fm-design' \
+    FM_FAKE_TMUX_LOG="$TMP_ROOT/two-handoffs-tmux.log" \
+    FM_FAKE_TMUX_CAPTURE="$TMP_ROOT/two-handoffs-fake/pane.txt" \
+    FM_SEND_SETTLE=0 FM_SEND_SLEEP=0 FM_SEND_RETRIES=1 \
+    "$ROOT/bin/fm-backlog-handoff.sh" design postfach-uebergang-abschliessen \
+    > "$out1" 2>&1 \
+    || fail "first handoff failed: $(cat "$out1")"
+  FM_HOME="$home" FM_ROOT_OVERRIDE="$ROOT" PATH="$fakebin:$PATH" \
+    FM_FAKE_TMUX_WINDOW='firstmate:fm-design' \
+    FM_FAKE_TMUX_LOG="$TMP_ROOT/two-handoffs-tmux.log" \
+    FM_FAKE_TMUX_CAPTURE="$TMP_ROOT/two-handoffs-fake/pane.txt" \
+    FM_SEND_SETTLE=0 FM_SEND_SLEEP=0 FM_SEND_RETRIES=1 \
+    "$ROOT/bin/fm-backlog-handoff.sh" design vault-regelfragen-umsetzung \
+    > "$out2" 2>&1 \
+    || fail "second handoff failed: $(cat "$out2")"
+
+  bodies=$(inbox_body_stream "$home/state" design)
+  assert_contains "$bodies" 'New routed work is in your backlog.' \
+    "receiver inbox lost the fixed routed-work instruction"
+  assert_contains "$bodies" 'postfach-uebergang-abschliessen' \
+    "first handoff's message did not name its own item"
+  assert_contains "$bodies" 'vault-regelfragen-umsetzung' \
+    "second handoff's message did not name its own item"
+
+  bodies=$(inbox_bodies_by_record "$home/state" design)
+  first_line=$(printf '%s\n' "$bodies" | grep -F 'postfach-uebergang-abschliessen')
+  second_line=$(printf '%s\n' "$bodies" | grep -F 'vault-regelfragen-umsetzung')
+  [ "$first_line" != "$second_line" ] \
+    || fail "two handoffs for different items produced the same message text: $first_line"
+  printf '%s\n' "$first_line" | grep -qF 'vault-regelfragen-umsetzung' \
+    && fail "the first handoff's message also named the second item: $first_line"
+  printf '%s\n' "$second_line" | grep -qF 'postfach-uebergang-abschliessen' \
+    && fail "the second handoff's message also named the first item: $second_line"
+
+  pass "two consecutive handoffs each name their own item, so they are never textually identical"
+}
+
 test_handoff_wakes_live_local_receiver
+test_two_consecutive_handoffs_name_their_own_items
 test_failed_wake_retries_when_the_item_is_already_present
 test_known_receiver_failure_remains_retryable_after_grace
 test_known_failure_restores_retry_after_reconciliation_race
diff --git a/tests/fm-remote-backlog-handoff.test.sh b/tests/fm-remote-backlog-handoff.test.sh
index f05c1ad14fe..4e5af744c50 100755
--- a/tests/fm-remote-backlog-handoff.test.sh
+++ b/tests/fm-remote-backlog-handoff.test.sh
@@ -102,6 +102,8 @@ command_name=$(perl -MMIME::Base64=decode_base64 -e '$d=decode_base64($ARGV[0]);
 case "${FM_FAKE_SSH_MODE:-normal}:$command_name" in
   *:fm-remote-secondmate-control.sh)
     printf '%s\n' "$command_name" >> "$FM_FAKE_REMOTE_WAKE_LOG"
+    perl -MMIME::Base64=decode_base64 -e '$d=decode_base64($ARGV[0]); $d=~tr/\0\n/  /; print "$d\n"' "$argv_b64" \
+      >> "$FM_FAKE_REMOTE_WAKE_LOG.argv"
     [ "${FM_FAKE_REMOTE_WAKE_RC:-0}" -eq 0 ] || printf 'remote receiver wake failed\n' >&2
     exit "${FM_FAKE_REMOTE_WAKE_RC:-0}"
     ;;
@@ -446,6 +448,11 @@ assert_absent "$PARENT/data/handoff/ios.outbox.md" "permanently lost wake retain
   || fail "later handoff did not retain the same pending wake correlation"
 [ "$(grep -cF fm-remote-secondmate-control.sh "$WAKE_LOG")" -gt "$wakes_after_resume" ] \
   || fail "later handoff did not retry the separately pending wake"
+reused_wake=$(tail -n 1 "$WAKE_LOG.argv")
+assert_contains "$reused_wake" 'wake-permanent-a' \
+  "reused pending wake dropped the earlier batch's item"
+assert_contains "$reused_wake" 'wake-permanent-b' \
+  "reused pending wake did not name the later batch's item"
 pass "a permanently unconfirmable wake never jams later durable handoffs"
 
 RM_FAKEBIN="$TMP_ROOT/rm-fakebin"
diff --git a/tests/fm-shared-captain-inheritance.test.sh b/tests/fm-shared-captain-inheritance.test.sh
index efd61dd804f..d5656d96933 100755
--- a/tests/fm-shared-captain-inheritance.test.sh
+++ b/tests/fm-shared-captain-inheritance.test.sh
@@ -204,6 +204,68 @@ test_unsafe_artifacts_and_failure_restore_readonly_mode() {
   pass "unsafe shared captain artifacts are rejected and failure restores read-only mode"
 }
 
+test_header_validation_tolerates_reflow_but_rejects_missing_phrase() {
+  local rec primary second reflowed err rc
+
+  reflowed=$(mktemp "$TMP_ROOT/reflowed-header.XXXXXX")
+  cat > "$reflowed" <<'EOF'
+# Shared captain preferences
+
+This file is main-authoritative in the main
+firstmate home.
+In secondmate homes it is read-only in secondmate
+homes and must not be edited there.
+Route new captain-preference discoveries to the main firstmate through marked status or a document pointer.
+EOF
+  shared_captain_header_valid "$reflowed" \
+    || fail "a header reflowed mid-phrase should still validate when every phrase's words are intact"
+
+  rec=$(new_home_pair header-reflow)
+  primary=${rec%%|*}
+  second=${rec#*|}
+  write_shared "$primary/data/captain-shared.md" "reflow-carrying shared body"
+  sed -i.bak 's/^This file is main-authoritative in the main firstmate home\.$/This file is main-authoritative in the main\nfirstmate home./' \
+    "$primary/data/captain-shared.md"
+  rm -f "$primary/data/captain-shared.md.bak"
+
+  propagate_secondmate_inheritance "$primary" "$second" >/dev/null 2>"$TMP_ROOT/header-reflow.err" \
+    || fail "reflowed but semantically intact header should still propagate"
+  cmp -s "$primary/data/captain-shared.md" "$second/data/captain-shared.md" \
+    || fail "reflowed header propagation did not converge secondmate shared preferences"
+
+  rm -f "$reflowed"
+  reflowed=$(mktemp "$TMP_ROOT/missing-phrase-header.XXXXXX")
+  cat > "$reflowed" <<'EOF'
+# Shared captain preferences
+
+This file is main-authoritative in the main firstmate home.
+Route new captain-preference discoveries to the main firstmate through marked status or a document pointer.
+EOF
+  if shared_captain_header_valid "$reflowed"; then
+    fail "a header genuinely missing a required phrase must still be rejected"
+  fi
+
+  rec=$(new_home_pair header-missing)
+  primary=${rec%%|*}
+  second=${rec#*|}
+  cat > "$primary/data/captain-shared.md" <<'EOF'
+# Shared captain preferences
+
+This file is main-authoritative in the main firstmate home.
+Route new captain-preference discoveries to the main firstmate through marked status or a document pointer.
+
+missing-phrase shared body
+EOF
+  err="$TMP_ROOT/header-missing.err"
+  propagate_secondmate_inheritance "$primary" "$second" >/dev/null 2>"$err"; rc=$?
+  [ "$rc" -ne 0 ] || fail "header genuinely missing a required phrase should be rejected"
+  assert_grep "primary source header missing required main-authoritative warning" "$err" \
+    "missing-phrase rejection error should be explicit"
+  assert_absent "$second/data/captain-shared.md" "rejected header should not propagate to the secondmate"
+
+  pass "shared captain header validation tolerates mid-phrase reflow but still rejects a genuinely missing phrase"
+}
+
 make_fake_spawn_toolchain() {
   local dir=$1 fakebin
   fakebin="$dir/fakebin"
@@ -396,6 +458,7 @@ test_first_copy_readonly_and_local_files_preserved
 test_drift_quarantine_collision_and_repeated_convergence
 test_missing_source_mirrors_absence_without_losing_local_bytes
 test_unsafe_artifacts_and_failure_restore_readonly_mode
+test_header_validation_tolerates_reflow_but_rejects_missing_phrase
 test_spawn_convergence_point_copies_shared_file
 test_bootstrap_convergence_point_copies_shared_file
 test_config_push_convergence_point_updates_changed_source