diff --git a/src/lib/selector-prefs-storage.test.ts b/src/lib/selector-prefs-storage.test.ts
new file mode 100644
index 0000000000..514ca59550
--- /dev/null
+++ b/src/lib/selector-prefs-storage.test.ts
@@ -0,0 +1,76 @@
+import { beforeEach, describe, expect, it } from "vitest"
+
+import {
+  getSavedModeId,
+  getSavedPrefsForConnect,
+  saveConfigPreference,
+  saveModePreference,
+} from "./selector-prefs-storage"
+
+const STORAGE_KEY = "codeg:selector-prefs"
+
+beforeEach(() => {
+  localStorage.clear()
+})
+
+describe("selector preference persistence", () => {
+  it("round-trips mode and config preferences", () => {
+    saveModePreference("codex", {
+      current_mode_id: "plan",
+      available_modes: [],
+    })
+    saveConfigPreference("codex", "reasoning_effort", "high")
+
+    expect(getSavedModeId("codex")).toBe("plan")
+    expect(getSavedPrefsForConnect("codex")).toEqual({
+      modeId: "plan",
+      configValues: { reasoning_effort: "high" },
+    })
+  })
+
+  it.each(["{not json", "null", "[]", '"text"', "42"])(
+    "falls back safely for an invalid top-level value: %s",
+    (stored) => {
+      localStorage.setItem(STORAGE_KEY, stored)
+
+      expect(getSavedModeId("codex")).toBeNull()
+      expect(getSavedPrefsForConnect("codex")).toEqual({
+        modeId: null,
+        configValues: null,
+      })
+
+      expect(() =>
+        saveModePreference("codex", {
+          current_mode_id: "default",
+          available_modes: [],
+        })
+      ).not.toThrow()
+      expect(getSavedModeId("codex")).toBe("default")
+    }
+  )
+
+  it("keeps valid nested fields and drops values with the wrong type", () => {
+    localStorage.setItem(
+      STORAGE_KEY,
+      JSON.stringify({
+        codex: {
+          modeId: 7,
+          configValues: {
+            reasoning_effort: "medium",
+            approval_policy: false,
+          },
+        },
+        claude_code: ["plan"],
+      })
+    )
+
+    expect(getSavedPrefsForConnect("codex")).toEqual({
+      modeId: null,
+      configValues: { reasoning_effort: "medium" },
+    })
+    expect(getSavedPrefsForConnect("claude_code")).toEqual({
+      modeId: null,
+      configValues: null,
+    })
+  })
+})
diff --git a/src/lib/selector-prefs-storage.ts b/src/lib/selector-prefs-storage.ts
index 6c20368a14..c6e5965321 100644
--- a/src/lib/selector-prefs-storage.ts
+++ b/src/lib/selector-prefs-storage.ts
@@ -28,11 +28,43 @@ interface SelectorPrefs {
 
 type AllPrefs = Record<string, SelectorPrefs>
 
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null && !Array.isArray(value)
+}
+
+function parseConfigValues(value: unknown): Record<string, string> | undefined {
+  if (!isRecord(value)) return undefined
+
+  const entries = Object.entries(value).filter(
+    (entry): entry is [string, string] => typeof entry[1] === "string"
+  )
+  return entries.length > 0 ? Object.fromEntries(entries) : undefined
+}
+
+function parseAllPrefs(value: unknown): AllPrefs {
+  if (!isRecord(value)) return {}
+
+  const entries: Array<[string, SelectorPrefs]> = []
+  for (const [agentType, rawPrefs] of Object.entries(value)) {
+    if (!isRecord(rawPrefs)) continue
+
+    const prefs: SelectorPrefs = {}
+    if (typeof rawPrefs.modeId === "string") {
+      prefs.modeId = rawPrefs.modeId
+    }
+    const configValues = parseConfigValues(rawPrefs.configValues)
+    if (configValues) prefs.configValues = configValues
+    entries.push([agentType, prefs])
+  }
+
+  return Object.fromEntries(entries)
+}
+
 function readAll(): AllPrefs {
   if (typeof window === "undefined") return {}
   try {
     const raw = localStorage.getItem(STORAGE_KEY)
-    return raw ? (JSON.parse(raw) as AllPrefs) : {}
+    return raw ? parseAllPrefs(JSON.parse(raw) as unknown) : {}
   } catch {
     return {}
   }
@@ -67,7 +99,7 @@ function updatePrefs(
 
 // ── Read ──
 
-/** Read saved mode id for an agent (no validation, just the raw value). */
+/** Read the validated saved mode id for an agent. */
 export function getSavedModeId(agentType: string): string | null {
   const all = readAll()
   return all[agentType]?.modeId ?? null