diff --git a/backend/api/routers/profiles.py b/backend/api/routers/profiles.py
index a4483beb..80f497aa 100644
--- a/backend/api/routers/profiles.py
+++ b/backend/api/routers/profiles.py
@@ -73,6 +73,17 @@ async def create_profile(
                 raise ValueError("not an object")
         except ValueError:
             raise HTTPException(status_code=422, detail="vd_states must be a JSON object")
+        # Root-cause close for #983: a design profile must never be PERSISTED
+        # with a partial vd_states shape, regardless of which client (older
+        # frontend build, hand-edited payload, third-party API caller) created
+        # it — a missing category key crashes DesignMethodPanel's render on
+        # every future client that selects this profile. CATEGORY_ORDER is the
+        # same single source of truth the frontend's CATEGORIES keys mirror
+        # (core/describe_voice.py), so this can't drift from the picker.
+        from core.describe_voice import CATEGORY_ORDER
+        for _cat in CATEGORY_ORDER:
+            parsed.setdefault(_cat, "Auto")
+        vd_states = _json.dumps(parsed)
         # An all-Auto design (every category left on "Auto") yields an empty
         # instruct — that's still a valid, saveable voice: synthesis falls back
         # to neutral instruct-only conditioning (see generation.py design path).
diff --git a/frontend/src/components/clone/DesignMethodPanel.jsx b/frontend/src/components/clone/DesignMethodPanel.jsx
index 57c37ba8..26a863b2 100644
--- a/frontend/src/components/clone/DesignMethodPanel.jsx
+++ b/frontend/src/components/clone/DesignMethodPanel.jsx
@@ -147,6 +147,13 @@ export default function DesignMethodPanel({
           {Object.entries(CATEGORIES).map(([key, options]) => {
             const many = options.length > 6;
             const optLabel = (val) => {
+              // #983: a profile/localStorage-restored vdStates can carry a
+              // partial shape (missing category keys) — val is then undefined
+              // here even though the 'Auto' check above only catches the
+              // literal sentinel. Guard before .replace() rather than crash;
+              // 'Auto' matches how the rest of the component (the ternary
+              // above, the chip/select fallbacks) treats an unset category.
+              if (typeof val !== 'string' || !val) return 'Auto';
               const tKey = `clone.opt_${val.replace(/[ -]/g, '_')}`;
               const tl = t(tKey);
               return tl !== tKey ? tl : val;
@@ -180,9 +187,13 @@ export default function DesignMethodPanel({
                     aria-label={t(`clone.cat_${key}`)}
                   >
                     {options.map((opt, i) => {
-                      const optTKey = `clone.opt_${opt.replace(/[ -]/g, '_')}`;
+                      // `opt` is always a hardcoded CATEGORIES string today,
+                      // never undefined — guarded anyway for consistency with
+                      // the identical pattern above (#983).
+                      const safeOpt = typeof opt === 'string' && opt ? opt : 'Auto';
+                      const optTKey = `clone.opt_${safeOpt.replace(/[ -]/g, '_')}`;
                       const optTl = t(optTKey);
-                      const optLabel = optTl !== optTKey ? optTl : opt;
+                      const optLabel = optTl !== optTKey ? optTl : safeOpt;
                       const checked = vdStates[key] === opt;
                       // Roving tabindex: the checked chip is the group's
                       // single tab stop (first chip if nothing matches).
diff --git a/frontend/src/components/clone/DesignMethodPanel.test.jsx b/frontend/src/components/clone/DesignMethodPanel.test.jsx
new file mode 100644
index 00000000..936e5e71
--- /dev/null
+++ b/frontend/src/components/clone/DesignMethodPanel.test.jsx
@@ -0,0 +1,68 @@
+import React from 'react';
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import DesignMethodPanel from './DesignMethodPanel';
+
+// #983: "Cannot read properties of undefined (reading 'replace')" — the
+// identity panel crashed whenever vdStates was missing one of the 6
+// CATEGORIES keys (a design profile saved by an older/foreign client, or a
+// stale localStorage shape). The label helper called `val.replace(...)` on
+// an undefined category value. This regression-tests the render guard added
+// to DesignMethodPanel.jsx directly, independent of the upstream data-shape
+// fixes in useProfiles.js / useAppData.js / profiles.py.
+
+// A minimal i18next-compatible mock: returns the defaultValue if given, else
+// echoes the key back (mirrors i18next's behavior for a missing translation,
+// which is what `optLabel`'s `tl !== tKey` check relies on).
+const t = (key, opts) => opts?.defaultValue ?? key;
+
+function setup(vdStates, props = {}) {
+  return render(
+    <DesignMethodPanel
+      t={t}
+      describeText=""
+      onDescribeChange={vi.fn()}
+      describeMatchedAny={false}
+      describeUnmatched={[]}
+      chipPersonalities={[]}
+      activePersonality={null}
+      applyPersonality={vi.fn()}
+      applyPreset={vi.fn()}
+      identityOpen={true}
+      setIdentityOpen={vi.fn()}
+      identityRecipe="test recipe"
+      vdStates={vdStates}
+      setVdStates={vi.fn()}
+      onChipKeyDown={vi.fn()}
+      showSaveProfile={false}
+      setShowSaveProfile={vi.fn()}
+      profileName=""
+      setProfileName={vi.fn()}
+      handleSaveDesignProfile={vi.fn()}
+      instruct=""
+      language="Auto"
+      {...props}
+    />,
+  );
+}
+
+describe('DesignMethodPanel — #983 partial vdStates crash', () => {
+  it('does not throw when vdStates is missing 5 of the 6 CATEGORIES keys', () => {
+    // Only Gender is set — Age, Pitch, Style, EnglishAccent, ChineseDialect
+    // are all undefined, exercising both the chip-based and <select>-based
+    // ("many" options) render paths.
+    expect(() => setup({ Gender: 'male' })).not.toThrow();
+  });
+
+  it('does not throw when vdStates is a fully empty object', () => {
+    expect(() => setup({})).not.toThrow();
+  });
+
+  it('still renders category labels and the identity recipe with a partial shape', () => {
+    const { container } = setup({ Gender: 'male' });
+    expect(screen.getByText('test recipe')).toBeInTheDocument();
+    // The label text sits alongside a sibling <span> kicker, so assert via
+    // textContent rather than getByText's exact-node matching.
+    expect(container.textContent).toContain('clone.cat_Gender');
+  });
+});
diff --git a/frontend/src/hooks/useAppData.js b/frontend/src/hooks/useAppData.js
index 8b10ed6b..f66d1381 100644
--- a/frontend/src/hooks/useAppData.js
+++ b/frontend/src/hooks/useAppData.js
@@ -8,6 +8,7 @@ import { listExportHistory } from '../api/exports';
 import { modelStatus as apiModelStatus } from '../api/system';
 import { useModelStatus } from '../api/hooks';
 import useRealtimeEvents from './useRealtimeEvents';
+import { mergeDescribedAttrs } from '../utils/voiceInstruct';
 
 /**
  * Encapsulates all data-loading effects, localStorage persistence,
@@ -174,7 +175,12 @@ export default function useAppData() {
         setDefineMethod('design');
       } else if (saved.mode) setMode(saved.mode);
       if (saved.defineMethod) setDefineMethod(saved.defineMethod);
-      if (saved.vdStates) setVdStates(saved.vdStates);
+      // #983: legacy localStorage state had no shape validation at all — a
+      // partial/corrupt saved.vdStates crashed DesignMethodPanel on restore.
+      // Mirror useProfiles.js's guard: require a plain object, then complete
+      // it to the full CATEGORIES shape (missing/unknown keys → 'Auto').
+      if (saved.vdStates && typeof saved.vdStates === 'object')
+        setVdStates(mergeDescribedAttrs(saved.vdStates));
       if (saved.language) setLanguage(saved.language);
       if (saved.isSidebarCollapsed !== undefined) setIsSidebarCollapsed(saved.isSidebarCollapsed);
       if (saved.sidebarTab) setSidebarTab(saved.sidebarTab);
diff --git a/frontend/src/hooks/useProfiles.js b/frontend/src/hooks/useProfiles.js
index f7588f0e..c422c28d 100644
--- a/frontend/src/hooks/useProfiles.js
+++ b/frontend/src/hooks/useProfiles.js
@@ -11,7 +11,7 @@ import { generateSpeech, audioUrlWithCacheBust } from '../api/generate';
 import { apiFetch } from '../api/client';
 import { playBlobAudio } from '../utils/media';
 import { PRESETS } from '../utils/constants';
-import { instructToFormValue } from '../utils/voiceInstruct';
+import { instructToFormValue, mergeDescribedAttrs } from '../utils/voiceInstruct';
 import { askConfirm } from '../utils/dialog';
 import { toast } from 'react-hot-toast';
 import { recordValueMoment } from '../utils/donationMoments';
@@ -96,7 +96,12 @@ export default function useProfiles({ loadHistory, loadProfiles }) {
       if (profile.kind === 'design' && profile.vd_states) {
         try {
           const parsed = JSON.parse(profile.vd_states);
-          if (parsed && typeof parsed === 'object') setVdStates(parsed);
+          // #983: a profile saved by an older/foreign client (or hand-edited)
+          // can carry a partial shape — mergeDescribedAttrs (already used for
+          // the "describe your voice" restore path) guarantees every
+          // CATEGORIES key is present, defaulting missing/unknown ones to
+          // 'Auto', so DesignMethodPanel never sees an undefined category.
+          if (parsed && typeof parsed === 'object') setVdStates(mergeDescribedAttrs(parsed));
         } catch {
           /* malformed stored state — sliders keep their current values */
         }
diff --git a/tests/frontend/describeVoice.test.mjs b/tests/frontend/describeVoice.test.mjs
index 2d7efbf4..431f70af 100644
--- a/tests/frontend/describeVoice.test.mjs
+++ b/tests/frontend/describeVoice.test.mjs
@@ -61,3 +61,19 @@ test('empty / missing attrs yields all-Auto', () => {
     for (const cat of ALL_CATS) assert.equal(out[cat], 'Auto');
   }
 });
+
+test('#983 — a partial vdStates shape (as restored from a saved profile or '
+  + 'localStorage) is completed to all 6 CATEGORIES keys', () => {
+  // Mirrors the exact partial shape from issue #983: only Gender survives
+  // (e.g. a design profile saved by an older client, or a hand-edited
+  // payload), the other 5 category keys are simply absent from the object.
+  // useProfiles.js/useAppData.js now run any restored vd_states through this
+  // helper before calling setVdStates, so DesignMethodPanel's render never
+  // sees an undefined category value.
+  const out = mergeDescribedAttrs({ Gender: 'male' });
+  assert.deepEqual(Object.keys(out).sort(), [...ALL_CATS].sort());
+  assert.equal(out.Gender, 'male');
+  for (const cat of ALL_CATS) {
+    if (cat !== 'Gender') assert.equal(out[cat], 'Auto');
+  }
+});
diff --git a/tests/test_profile_design_save_decouple.py b/tests/test_profile_design_save_decouple.py
index bb35dc1d..3e8537f2 100644
--- a/tests/test_profile_design_save_decouple.py
+++ b/tests/test_profile_design_save_decouple.py
@@ -81,7 +81,11 @@ def test_design_save_creates_row_when_model_unavailable(iso, monkeypatch):
     assert row["kind"] == "design"
     # Sample is pending — no rendered identity wav was forced at save time.
     assert not row["ref_audio_path"]
-    assert json.loads(row["vd_states"]) == _VD
+    # #983: vd_states is completed to all 6 known categories before persisting
+    # (missing ones default to 'Auto') — _VD only sets 3, so the stored value
+    # is a superset of it, not an exact match.
+    stored = json.loads(row["vd_states"])
+    assert stored == {**_VD, "Style": "Auto", "EnglishAccent": "Auto", "ChineseDialect": "Auto"}
 
 
 def test_all_auto_design_is_saveable(iso, monkeypatch):
diff --git a/tests/test_profile_unification.py b/tests/test_profile_unification.py
index 4d520bc6..d0bc23bc 100644
--- a/tests/test_profile_unification.py
+++ b/tests/test_profile_unification.py
@@ -170,12 +170,41 @@ def test_design_create_renders_sample_and_stores_params(app_client, fake_render)
     assert body["kind"] == "design"
     profile = client.get(f"/profiles/{body['id']}").json()
     assert profile["kind"] == "design"
-    assert json.loads(profile["vd_states"]) == _VD
+    # #983: the server now completes vd_states to all 6 known categories
+    # (missing ones default to 'Auto') before persisting — _VD only sets 3,
+    # so the stored value is a superset of it, not an exact match.
+    stored = json.loads(profile["vd_states"])
+    assert stored == {**_VD, "Style": "Auto", "EnglishAccent": "Auto", "ChineseDialect": "Auto"}
     assert profile["seed"] == 42  # deterministic identity sample
     wav = os.path.join(cfg.VOICES_DIR, profile["ref_audio_path"])
     assert os.path.exists(wav) and os.path.getsize(wav) > 0
 
 
+def test_design_normalizes_partial_vd_states_to_all_categories(app_client, fake_render):
+    """#983: a design profile must never persist with a partial vd_states shape.
+
+    A client (older frontend build, hand-edited payload, third-party API
+    caller) that only sends a subset of the 6 known category keys used to be
+    saved as-is — selecting that profile later handed the frontend an
+    incomplete vdStates object, crashing DesignMethodPanel's render
+    ("Cannot read properties of undefined (reading 'replace')"). The server
+    now fills every missing category with 'Auto' before persisting, so the
+    stored vd_states is always complete regardless of which client wrote it.
+    """
+    client, _ = app_client
+    r = client.post(
+        "/profiles",
+        data={"name": "Partial", "kind": "design", "vd_states": json.dumps({"Gender": "male"})},
+    )
+    assert r.status_code == 200, r.text
+    profile = client.get(f"/profiles/{r.json()['id']}").json()
+    stored = json.loads(profile["vd_states"])
+    assert set(stored) == {"Gender", "Age", "Pitch", "Style", "EnglishAccent", "ChineseDialect"}
+    assert stored["Gender"] == "male"
+    for cat in ("Age", "Pitch", "Style", "EnglishAccent", "ChineseDialect"):
+        assert stored[cat] == "Auto"
+
+
 # ── Migration 0005 ───────────────────────────────────────────────────────────
 
 def _run_alembic(direction: str, db_path: str, target: str = "head"):