diff --git a/client/src/lib/engagementRules.js b/client/src/lib/engagementRules.js
index 5611e80..7e1eb59 100644
--- a/client/src/lib/engagementRules.js
+++ b/client/src/lib/engagementRules.js
@@ -101,15 +101,56 @@ export function segmentChoicesFor(trigger, ceilings, segments) {
  */
 export function describeReach(preview) {
   if (!preview) return ''
-  if (preview.dormant) return `Resolves to nobody right now — ${preview.reason || 'dormant'}.`
+  const why = operatorWords(preview.reason)
+  if (preview.dormant) return `Resolves to nobody right now — ${why || 'dormant'}.`
   if (preview.permitted === false) {
     return `Reaches ${preview.count}, but this trigger does not permit that audience — saving will be refused.`
   }
-  if (preview.reason) return `${preview.count} right now — ${preview.reason}.`
+  if (why) return `${preview.count} right now — ${why}.`
   if (preview.capped) return `At least ${preview.count} people (the preview stops counting there).`
   return preview.count === 1 ? '1 person right now.' : `${preview.count} people right now.`
 }
 
+/**
+ * The server says "segment"; these screens say "saved audience".
+ *
+ * The API, the schema and the docs all call it a segment and should keep doing
+ * so - it is one word for one table. But an operator meets the concept here,
+ * under a heading that says "Audiences", and a sentence that switches vocabulary
+ * mid-screen reads as a sentence about something else.
+ */
+export function operatorWords(text) {
+  if (!text) return text
+  // Word-wise rather than a regex, so "segmented" and the like are left alone.
+  const swap = { segment: 'saved audience', segments: 'saved audiences' }
+  return String(text)
+    .split(' ')
+    .map((word) => swap[word] || word)
+    .join(' ')
+}
+
+/**
+ * The one audience choice that silently reaches nobody, said out loud.
+ *
+ * `members` is the ceiling for "a module-declared list". Without a saved
+ * audience naming WHICH list there is no list, and core knows no game vocabulary
+ * with which to guess - so the rule resolves to the empty set every time it
+ * fires. It is also the DEFAULT the moment an operator picks a `members`-ceiling
+ * trigger, which is what makes it a trap rather than a curiosity: the rule saves,
+ * switches on, and mails nobody, with nothing on the screen saying so unless the
+ * operator happens to press Preview.
+ *
+ * Returns a sentence, or null when there is nothing to warn about.
+ */
+export function audienceWarning(form) {
+  if (!form) return null
+  if (form.audienceSegmentId) return null
+  if (form.audience === 'members') {
+    return 'This reaches nobody as it stands. “Members of a module-declared list” needs a saved audience naming which list.'
+  }
+  return null
+}
+
 // ── Segment expressions ────────────────────────────────────────────────────
 
 /**
@@ -127,7 +168,16 @@ export function notPlacementError(expression) {
     if (!node || typeof node !== 'object') return null
     if (!node.op) return null
     if (node.op === 'not' && !underAnd) {
-      return 'A "not" can only be used inside an "all of" group — on its own it would mean "everyone except…".'
+      return 'An excluded audience can only be used alongside an included one — on its own it would mean “everyone except…”.'
+    }
+    // The same rule from the other side: a group of nothing but exclusions has
+    // no set to take them from. The composer offers "exclude" on every row, so
+    // this is one checkbox away at all times and is worth saying before the
+    // round trip - the server refuses it, correctly, but only after a save.
+    if ((node.op === 'and' || node.op === 'or') && (node.nodes || []).length) {
+      if ((node.nodes || []).every((c) => c && c.op === 'not')) {
+        return 'At least one audience has to be included — a list made only of exclusions has nothing to exclude from.'
+      }
     }
     for (const child of node.nodes || []) {
       const err = walk(child, node.op === 'and')
diff --git a/client/src/routes/admin/views/EngagementAudiences.jsx b/client/src/routes/admin/views/EngagementAudiences.jsx
index 0bd892b..de09168 100644
--- a/client/src/routes/admin/views/EngagementAudiences.jsx
+++ b/client/src/routes/admin/views/EngagementAudiences.jsx
@@ -50,12 +50,13 @@ const toGroup = (expression) =>
 
 // ── One leaf: an audience and its declared parameters ──────────────────────
 
-function LeafRow({ audiences, node, onChange, onRemove, negated, onToggleNegate, canNegate }) {
+function LeafRow({ audiences, node, onChange, onRemove, negated, onToggleNegate, canNegate, first }) {
   const declared = audiences.find((a) => a.id === node.audienceId)
   return (
     <div style={{ display: 'flex', gap: 8, marginBottom: 8, flexWrap: 'wrap', alignItems: 'flex-end' }}>
       <label style={{ flex: '1 1 240px' }}>
-        <span className="field-label">Audience</span>
+        {/* The heading belongs to the group, not to every line in it. */}
+        {first && <span className="field-label">Audience</span>}
         <select
           className="select"
           value={node.audienceId || ''}
@@ -198,6 +199,7 @@ function SegmentEditor({ audiences, segment, onSaved, onCancel }) {
           return (
             <LeafRow
               key={i}
+              first={i === 0}
               audiences={audiences}
               node={leaf}
               negated={negated}
diff --git a/client/src/routes/admin/views/EngagementRules.jsx b/client/src/routes/admin/views/EngagementRules.jsx
index d4ebd52..1382a2e 100644
--- a/client/src/routes/admin/views/EngagementRules.jsx
+++ b/client/src/routes/admin/views/EngagementRules.jsx
@@ -8,6 +8,7 @@ import {
   segmentChoicesFor,
   describeReach,
   describeRule,
+  audienceWarning,
   conditionRowsFrom,
   conditionsFromRows,
   operatorsForType,
@@ -201,9 +202,14 @@ function RuleEditor({ catalog, segments, rule, onSaved, onCancel }) {
           <select
             className="select"
             value={form.audienceSegmentId ? '' : form.audience}
-            disabled={Boolean(form.audienceSegmentId)}
+            disabled={Boolean(form.audienceSegmentId) || !audienceChoices.length}
             onChange={(e) => { set({ audience: e.target.value, audienceSegmentId: null }); setPreview(null) }}
           >
+            {/* Without a trigger there is no ceiling, so there is nothing this
+                may legitimately offer — and a select with zero options renders
+                as a control that is broken rather than as one that is waiting. */}
+            {!audienceChoices.length && <option value="">Choose a trigger first…</option>}
+            {Boolean(form.audienceSegmentId) && <option value="">Using the saved audience →</option>}
             {audienceChoices.map((c) => (
               <option key={c.id} value={c.id}>{c.label}</option>
             ))}
@@ -241,6 +247,15 @@ function RuleEditor({ catalog, segments, rule, onSaved, onCancel }) {
           {describeReach(preview)}
         </p>
       )}
+      {/* The `members`-with-no-saved-audience trap, said before the save rather
+          than discovered after it. It is the DEFAULT the moment a
+          members-ceiling trigger is chosen, and the rule it produces saves,
+          switches on and mails nobody. */}
+      {!preview && audienceWarning(form) && (
+        <p className="sans" style={{ margin: '10px 0 0', fontSize: '0.84rem', color: 'var(--accent)' }}>
+          {audienceWarning(form)}
+        </p>
+      )}
       {trigger && audienceChoices.length <= 1 && (
         <p className="sans" style={{ margin: '10px 0 0', fontSize: '0.8rem', color: 'var(--muted)' }}>
           This event only permits “{trigger.ceiling}”. The audience a rule may use is capped by the
@@ -260,8 +275,8 @@ function RuleEditor({ catalog, segments, rule, onSaved, onCancel }) {
             {form.channels.includes(c.id) && (
               <input
                 className="input"
-                style={{ marginTop: 6 }}
-                placeholder="template key (optional until Phase 5)"
+                style={{ marginTop: 6, width: '100%' }}
+                placeholder="template key (optional)"
                 value={form.templateKeys[c.id] || ''}
                 onChange={(e) => set({ templateKeys: { ...form.templateKeys, [c.id]: e.target.value } })}
               />
diff --git a/client/test/engagementRules.test.js b/client/test/engagementRules.test.js
index 7245878..611ac4c 100644
--- a/client/test/engagementRules.test.js
+++ b/client/test/engagementRules.test.js
@@ -9,6 +9,8 @@ import {
   describeRule,
   describeExpression,
   notPlacementError,
+  audienceWarning,
+  operatorWords,
   conditionRowsFrom,
   conditionsFromRows,
   operatorsForType,
@@ -218,6 +220,34 @@ test('a single stored comparison is one editable row', () => {
 
 // ── Segment composition ────────────────────────────────────────────────────
 
+test('a members audience with no saved audience is warned about BEFORE the save', () => {
+  // The trap the browser walk found: it is the default the moment a
+  // members-ceiling trigger is chosen, and the rule it produces saves, switches
+  // on and mails nobody. Nothing on the screen said so unless you pressed
+  // Preview.
+  assert.match(audienceWarning({ audience: 'members', audienceSegmentId: null }), /reaches nobody/)
+  assert.equal(audienceWarning({ audience: 'members', audienceSegmentId: 4 }), null)
+  assert.equal(audienceWarning({ audience: 'owner', audienceSegmentId: null }), null)
+})
+
+test('the server says "segment"; the screens say "saved audience"', () => {
+  // One word for one table in the API, the schema and the docs. But an operator
+  // meets the concept under a heading that says "Audiences", and a sentence that
+  // switches vocabulary mid-screen reads as being about something else.
+  assert.equal(operatorWords('audience segment is dormant'), 'audience saved audience is dormant')
+  assert.match(describeReach({ count: 0, dormant: true, reason: 'audience segment is dormant' }), /saved audience/)
+  // and it does not maul a word that merely contains it
+  assert.equal(operatorWords('segmented data'), 'segmented data')
+})
+
+test('a list of nothing but exclusions is refused before the round trip', () => {
+  // One checkbox away at all times, because the composer offers "exclude" on
+  // every row including the only one. The server refuses it correctly — but
+  // only after a save.
+  const err = notPlacementError({ op: 'and', nodes: [{ op: 'not', nodes: [{ audienceId: 'a' }] }] })
+  assert.match(err, /at least one audience/i)
+})
+
 test('a bare not is refused before it reaches the server', () => {
   assert.ok(notPlacementError({ op: 'not', nodes: [{ audienceId: 'uo.governors' }] }))
   assert.ok(notPlacementError({ op: 'or', nodes: [{ audienceId: 'a' }, { op: 'not', nodes: [{ audienceId: 'b' }] }] }))