@@ -210,6 +210,25 @@ not executed here.
      failures via `console.error` (the app has no Sentry/structured-logging infra today). Routing these
      through a real logging path with error IDs is a cross-app concern, out of scope for the summary.
 
+- **Phase 9 review items deferred (out of scope for the wizard phase).** The Phase 9
+  reviewers surfaced three follow-ups left for later, all low practical risk:
+  1. **Cross-action atomicity of versioning.** The wizard calls `addConfigurationSnapshot`
+     then `applyConfigurationForward` as two sequential store actions, predicting the new
+     version as `configurationHistory.length + 1`. The calls are synchronous on the current
+     animal, so the version is correct in practice; but if the second action ever threw, an
+     orphan empty snapshot would remain. **Follow-up:** have `addConfigurationSnapshot`
+     return the created version (or add a combined create-and-apply action) so the two can't
+     desynchronize. Out of scope here (the plan deliberately kept creation and assignment
+     as separate actions).
+  2. **`appliedToDays` as a derived value.** It is currently a denormalized cache kept in
+     sync by `applyConfigurationForward`, with `reconcileAppliedToDays` providing the
+     trustworthy derived view (`updateDay({configurationVersion})` bypasses the stored
+     lists). **Follow-up:** consider dropping the stored field entirely and always deriving
+     it, removing the partition-maintenance burden. A data-model change, out of scope here.
+  3. **Wizard UX niceties for long studies.** Select-all/deselect-all controls and
+     relative/human-readable day labels for animals with 60–200+ days, and an explicit
+     success confirmation. Deferred to the [Phase 10](phase-10-a11y-keyboard.md) pass.
+
 ## Plan revisions
 
 - **2026-06-03 — parity model corrected; a byte-parity phase inserted after export.** Pre-Phase-5
 
@@ -30,7 +30,7 @@ import './DayEditor.scss';
  *   `applyConfigurationForward`); when provided, the reconfiguration wizard is available.
  * @returns {JSX.Element}
  */
-export default function DevicesStep({ animal, day, mergedDay, onFieldUpdate, animalDays, actions }) {
+export default function DevicesStep({ animal, day, mergedDay, onFieldUpdate, animalDays = undefined, actions = undefined }) {
   const electrodeGroups = animal.devices?.electrode_groups || [];
   const [wizardOpen, setWizardOpen] = useState(false);
 
@@ -215,26 +215,34 @@ export default function DevicesStep({ animal, day, mergedDay, onFieldUpdate, ani
         <a href={`#/animal/${animal.id}/editor`}>Edit at Animal Level</a>
       </div>
 
-      {/* Configuration-version indicator + reconfiguration entry point */}
+      {/* Configuration-version indicator + reconfiguration entry point. The wizard
+          is a sibling of the bar (not nested inside the flex layout div) so the
+          dialog is not a descendant of a layout container. */}
       {reconfig && (
-        <div className="config-version-bar">
-          <div className="config-version-info">
-            <span className="config-version-label">
-              Configuration version {reconfig.version}
-              {reconfig.snapshot ? `: ${reconfig.snapshot.description} (${reconfig.snapshot.date})` : ''}
-            </span>
-            <span className="config-version-applied">
-              Applied to {reconfig.appliedCount} {reconfig.appliedCount === 1 ? 'day' : 'days'}
-            </span>
+        <>
+          <div className="config-version-bar">
+            <div className="config-version-info">
+              <span className="config-version-label">
+                Configuration version {reconfig.version}
+                {reconfig.snapshot
+                  ? `: ${reconfig.snapshot.description || 'No description'} (${reconfig.snapshot.date || 'date unknown'})`
+                  : ''}
+              </span>
+              <span className="config-version-applied">
+                Applied to {reconfig.appliedCount} {reconfig.appliedCount === 1 ? 'day' : 'days'}
+              </span>
+            </div>
+            <button
+              type="button"
+              className="config-reconfig-button"
+              onClick={() => setWizardOpen(true)}
+            >
+              Reconfigure devices…
+            </button>
           </div>
-          <button
-            type="button"
-            className="config-reconfig-button"
-            onClick={() => setWizardOpen(true)}
-          >
-            Reconfigure devices…
-          </button>
           <ReconfigWizard
+            // Remount per day/version so reopening shows fresh form state.
+            key={`${day.id}-${reconfig.version}`}
             isOpen={wizardOpen}
             onClose={() => setWizardOpen(false)}
             animal={animal}
@@ -243,7 +251,7 @@ export default function DevicesStep({ animal, day, mergedDay, onFieldUpdate, ani
             candidateDays={reconfig.candidateDays}
             actions={actions}
           />
-        </div>
+        </>
       )}
 
       {/* Electrode groups (accordion) */}
@@ -371,11 +379,12 @@ DevicesStep.propTypes = {
   }).isRequired,
   mergedDay: PropTypes.object.isRequired,
   onFieldUpdate: PropTypes.func.isRequired,
+  // animalDays + actions are supplied together by DayEditorStepper to enable the
+  // configuration-version indicator and reconfiguration wizard; omitting both (e.g.
+  // in isolated unit renders) simply hides that section.
   animalDays: PropTypes.arrayOf(PropTypes.object),
-  actions: PropTypes.object,
-};
-
-DevicesStep.defaultProps = {
-  animalDays: undefined,
-  actions: undefined,
+  actions: PropTypes.shape({
+    addConfigurationSnapshot: PropTypes.func,
+    applyConfigurationForward: PropTypes.func,
+  }),
 };
@@ -5,6 +5,24 @@ import { resolveDayConfig } from '../../state/workspaceUtils';
 import { diffProbeConfigs } from '../../state/configDiff';
 import './ReconfigWizard.scss';
 
+/**
+ * Human-readable labels for the electrode-group fields a diff may flag as changed,
+ * so a scientist sees "brain region" rather than the raw `location` key. Unmapped
+ * keys fall through to the raw name.
+ */
+const GROUP_FIELD_LABELS = {
+  location: 'brain region',
+  device_type: 'probe type',
+  description: 'description',
+  targeted_location: 'targeted region',
+  targeted_x: 'ML coordinate',
+  targeted_y: 'AP coordinate',
+  targeted_z: 'DV coordinate',
+  units: 'coordinate units',
+};
+
+const labelField = (field) => GROUP_FIELD_LABELS[field] || field;
+
 /**
  * Probe-reconfiguration wizard.
  *
@@ -20,17 +38,27 @@ import './ReconfigWizard.scss';
  *
  * @param {object} props
  * @param {boolean} props.isOpen - Whether the dialog is shown.
- * @param {Function} props.onClose - Called on cancel/ESC/overlay and after a successful apply.
+ * @param {Function} props.onClose - Called (no args) on cancel/ESC/overlay and after a successful apply.
  * @param {object} props.animal - Animal whose live `devices` form the "next" config.
  * @param {object} props.day - The day being reconfigured (the default earliest applied day).
- * @param {object|null} props.prevDay - The chronologically previous day, or null.
+ * @param {object|null} [props.prevDay] - The chronologically previous day, or null.
  * @param {object[]} props.candidateDays - This day and all chronologically later days (apply-forward set).
  * @param {object} props.actions - Store actions: `addConfigurationSnapshot`, `applyConfigurationForward`.
  * @returns {JSX.Element|null}
  */
-export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay, candidateDays, actions }) {
+export default function ReconfigWizard({
+  isOpen,
+  onClose,
+  animal,
+  day,
+  prevDay = null,
+  candidateDays,
+  actions,
+}) {
   const baseId = useId();
   const titleId = `${baseId}-title`;
+  const summaryId = `${baseId}-summary`;
+  const errorId = `${baseId}-error`;
 
   const nextConfig = useMemo(
     () => ({
@@ -51,6 +79,7 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
   const [error, setError] = useState('');
 
   const toggleDay = (id) => {
+    if (error) setError('');
     setSelectedIds((prev) => {
       const next = new Set(prev);
       if (next.has(id)) next.delete(id);
@@ -71,7 +100,9 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
     }
 
     // Version the change, then assign it forward. The new snapshot takes the next
-    // sequential version (matching addConfigurationSnapshot's own numbering).
+    // sequential version (matching addConfigurationSnapshot's own numbering). These
+    // two calls are synchronous and read the current animal, so the version is
+    // correct; see the cross-action atomicity follow-up in the v3 plan overview.
     const newVersion = (animal.configurationHistory?.length || 0) + 1;
     actions.addConfigurationSnapshot(animal.id, {
       date,
@@ -82,22 +113,35 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
     const orderedIds = candidateDays.map((d) => d.id).filter((id) => selectedIds.has(id));
     actions.applyConfigurationForward(animal.id, newVersion, orderedIds);
 
-    onClose({ applied: true, version: newVersion, dayIds: orderedIds });
+    onClose();
   };
 
   if (!isOpen) return null;
 
   return (
-    <Modal isOpen={isOpen} onClose={onClose} title="Reconfigure devices" titleId={titleId} className="reconfig-wizard">
+    <Modal
+      isOpen={isOpen}
+      onClose={onClose}
+      title="Reconfigure devices"
+      titleId={titleId}
+      // A consequential action (reassigns configuration across many recording days).
+      role="alertdialog"
+      describedById={diff.hasChanges ? summaryId : 'reconfig-no-change'}
+      className="reconfig-wizard"
+    >
       {!diff.hasChanges ? (
-        <p className="reconfig-no-change" data-testid="reconfig-no-change">
+        <p id="reconfig-no-change" className="reconfig-no-change" data-testid="reconfig-no-change">
           No configuration change detected between{' '}
           {prevDay ? `${prevDay.date}` : 'the baseline'} and the current animal
           configuration. Edit the electrode groups in the Animal Editor first, then
           reopen this wizard to version the change.
         </p>
       ) : (
         <div className="reconfig-diff">
+          <p id={summaryId} className="reconfig-summary">
+            This versions the current device configuration and applies it to the days
+            you select below. Days before this one are not affected. Review the changes:
+          </p>
           <ConfigDiffView diff={diff} />
         </div>
       )}
@@ -114,9 +158,13 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
           <input
             type="text"
             value={description}
-            onChange={(e) => setDescription(e.target.value)}
+            onChange={(e) => {
+              if (error) setError('');
+              setDescription(e.target.value);
+            }}
             placeholder="e.g. Lowered CA1 tetrodes by 40 µm"
             disabled={!diff.hasChanges}
+            aria-describedby={error ? errorId : undefined}
           />
         </label>
 
@@ -132,6 +180,10 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
 
         <fieldset className="reconfig-days" disabled={!diff.hasChanges}>
           <legend>Apply to days</legend>
+          <p className="reconfig-days-hint">
+            All days from {day.date} onward are selected by default. To change an
+            earlier day, open its Day Editor individually.
+          </p>
           {candidateDays.map((d) => (
             <label key={d.id} className="reconfig-day-option">
               <input
@@ -145,17 +197,22 @@ export default function ReconfigWizard({ isOpen, onClose, animal, day, prevDay,
         </fieldset>
 
         {error && (
-          <p className="reconfig-error" role="alert">
+          <p id={errorId} className="reconfig-error" role="alert">
             {error}
           </p>
         )}
 
         <div className="form-actions">
-          <button type="button" className="btn-cancel" onClick={onClose}>
+          <button
+            type="button"
+            className="btn-cancel"
+            onClick={() => onClose()}
+            aria-label="Cancel and close"
+          >
             Cancel
           </button>
           <button type="submit" className="btn-primary" disabled={!diff.hasChanges}>
-            Apply forward
+            Apply to {selectedIds.size} {selectedIds.size === 1 ? 'day' : 'days'}
           </button>
         </div>
       </form>
@@ -176,15 +233,11 @@ ReconfigWizard.propTypes = {
   }).isRequired,
 };
 
-ReconfigWizard.defaultProps = {
-  prevDay: null,
-};
-
 /**
  * Read-only rendering of a {@link diffProbeConfigs} result.
  *
  * @param {object} props
- * @param {object} props.diff - The structured diff.
+ * @param {import('../../state/workspaceTypes').ProbeConfigDiff} props.diff - The structured diff.
  * @returns {JSX.Element}
  */
 function ConfigDiffView({ diff }) {
@@ -208,7 +261,7 @@ function ConfigDiffView({ diff }) {
         ))}
         {electrodeGroups.changed.map((c) => (
           <p key={`c-${c.id}`} className="diff-changed">
-            ~ Group {c.id} changed: {c.fields.join(', ')}
+            ~ Group {c.id} changed: {c.fields.map(labelField).join(', ')}
           </p>
         ))}
       </section>
 
@@ -8,6 +8,17 @@
     padding: 0.75rem 1rem;
   }
 
+  .reconfig-summary {
+    margin: 0 0 0.75rem;
+    color: #333;
+  }
+
+  .reconfig-days-hint {
+    margin: 0 0 0.5rem;
+    font-size: 0.8rem;
+    color: #555;
+  }
+
   .config-diff {
     section {
       margin-bottom: 1rem;
@@ -37,7 +48,8 @@
     }
 
     .diff-none {
-      color: #777;
+      /* #666 keeps AA contrast (≥4.5:1) for this small italic text on white. */
+      color: #666;
       font-style: italic;
       font-family: inherit;
     }
 
@@ -44,7 +44,7 @@ describe('ReconfigWizard [integration]', () => {
     expect(screen.getByText(/Added ntrode 3/)).toBeInTheDocument();
 
     await user.type(screen.getByLabelText(/change description/i), 'Lowered CA1 tetrodes');
-    await user.click(screen.getByRole('button', { name: /apply forward/i }));
+    await user.click(screen.getByRole('button', { name: /apply to/i }));
 
     // Creates the snapshot from the live (v2) config...
     expect(actions.addConfigurationSnapshot).toHaveBeenCalledTimes(1);
@@ -77,7 +77,7 @@ describe('ReconfigWizard [integration]', () => {
     );
 
     expect(screen.getByTestId('reconfig-no-change')).toBeInTheDocument();
-    expect(screen.getByRole('button', { name: /apply forward/i })).toBeDisabled();
+    expect(screen.getByRole('button', { name: /apply to/i })).toBeDisabled();
   });
 });
 
 
@@ -101,6 +101,21 @@ describe('applyConfigurationForward', () => {
     expect(JSON.stringify(result.current.model.workspace)).toBe(before);
   });
 
+  it('ignores day ids not in the workspace (no phantom entries in appliedToDays)', () => {
+    const { result, animalId, dayIds } = renderStore();
+
+    act(() => {
+      result.current.actions.applyConfigurationForward(animalId, 1, [dayIds.day3, 'no-such-day']);
+    });
+
+    const v1 = snapshot(result, animalId, 1);
+    expect(v1.appliedToDays).not.toContain('no-such-day');
+    expect(v1.appliedToDays).toContain(dayIds.day3);
+    expect(daysOf(result)[dayIds.day3].configurationVersion).toBe(1);
+    // The phantom id created no day entry.
+    expect(daysOf(result)['no-such-day']).toBeUndefined();
+  });
+
   it('throws on an unknown animal id', () => {
     const { result, dayIds } = renderStore();