diff --git a/src/pages/AiProvidersClaudeEditLayout.tsx b/src/pages/AiProvidersClaudeEditLayout.tsx
index 7025e0e..2701bb4 100644
--- a/src/pages/AiProvidersClaudeEditLayout.tsx
+++ b/src/pages/AiProvidersClaudeEditLayout.tsx
@@ -13,6 +13,7 @@ import { areKeyValueEntriesEqual, areModelEntriesEqual, areStringArraysEqual } f
 import { excludedModelsToText, parseExcludedModels } from '@/components/providers/utils';
 import { modelsToEntries } from '@/components/ui/modelInputListUtils';
 import type { ClaudeEditBaseline } from '@/stores/useClaudeEditDraftStore';
+import { parseRouteIndexParam } from '@/utils/routeParams';
 
 type LocationState = { fromAiProviders?: boolean } | null;
 
@@ -53,12 +54,6 @@ const buildEmptyForm = (): ProviderFormState => ({
   excludedText: '',
 });
 
-const parseIndexParam = (value: string | undefined) => {
-  if (!value) return null;
-  const parsed = Number.parseInt(value, 10);
-  return Number.isFinite(parsed) ? parsed : null;
-};
-
 const getErrorMessage = (err: unknown) => {
   if (err instanceof Error) return err.message;
   if (typeof err === 'string') return err;
@@ -122,7 +117,7 @@ export function AiProvidersClaudeEditLayout() {
 
   const params = useParams<{ index?: string }>();
   const hasIndexParam = typeof params.index === 'string';
-  const editIndex = useMemo(() => parseIndexParam(params.index), [params.index]);
+  const editIndex = useMemo(() => parseRouteIndexParam(params.index), [params.index]);
   const invalidIndexParam = hasIndexParam && editIndex === null;
 
   const connectionStatus = useAuthStore((state) => state.connectionStatus);
diff --git a/src/pages/AiProvidersCodexEditPage.tsx b/src/pages/AiProvidersCodexEditPage.tsx
index 98a37d8..b1abe1e 100644
--- a/src/pages/AiProvidersCodexEditPage.tsx
+++ b/src/pages/AiProvidersCodexEditPage.tsx
@@ -17,6 +17,7 @@ import { useAuthStore, useConfigStore, useNotificationStore } from '@/stores';
 import type { ProviderKeyConfig } from '@/types';
 import { buildHeaderObject, headersToEntries, normalizeHeaderEntries } from '@/utils/headers';
 import { areKeyValueEntriesEqual, areModelEntriesEqual, areStringArraysEqual } from '@/utils/compare';
+import { parseRouteIndexParam } from '@/utils/routeParams';
 import { entriesToModels, modelsToEntries } from '@/components/ui/modelInputListUtils';
 import { excludedModelsToText, parseExcludedModels } from '@/components/providers/utils';
 import type { ProviderFormState } from '@/components/providers';
@@ -40,12 +41,6 @@ const buildEmptyForm = (): ProviderFormState => ({
   excludedText: '',
 });
 
-const parseIndexParam = (value: string | undefined) => {
-  if (!value) return null;
-  const parsed = Number.parseInt(value, 10);
-  return Number.isFinite(parsed) ? parsed : null;
-};
-
 const getErrorMessage = (err: unknown) => {
   if (err instanceof Error) return err.message;
   if (typeof err === 'string') return err;
@@ -121,7 +116,7 @@ export function AiProvidersCodexEditPage() {
   const modelDiscoveryRequestIdRef = useRef(0);
 
   const hasIndexParam = typeof params.index === 'string';
-  const editIndex = useMemo(() => parseIndexParam(params.index), [params.index]);
+  const editIndex = useMemo(() => parseRouteIndexParam(params.index), [params.index]);
   const invalidIndexParam = hasIndexParam && editIndex === null;
 
   const initialData = useMemo(() => {
diff --git a/src/pages/AiProvidersGeminiEditPage.tsx b/src/pages/AiProvidersGeminiEditPage.tsx
index 8dd3ce3..2ca6b15 100644
--- a/src/pages/AiProvidersGeminiEditPage.tsx
+++ b/src/pages/AiProvidersGeminiEditPage.tsx
@@ -16,6 +16,7 @@ import { useAuthStore, useConfigStore, useNotificationStore } from '@/stores';
 import type { GeminiKeyConfig } from '@/types';
 import { buildHeaderObject, headersToEntries, normalizeHeaderEntries } from '@/utils/headers';
 import { areKeyValueEntriesEqual, areModelEntriesEqual, areStringArraysEqual } from '@/utils/compare';
+import { parseRouteIndexParam } from '@/utils/routeParams';
 import type { ModelInfo } from '@/utils/models';
 import { entriesToModels, modelsToEntries } from '@/components/ui/modelInputListUtils';
 import { excludedModelsToText, parseExcludedModels } from '@/components/providers/utils';
@@ -37,12 +38,6 @@ const buildEmptyForm = (): GeminiFormState => ({
   excludedText: '',
 });
 
-const parseIndexParam = (value: string | undefined) => {
-  if (!value) return null;
-  const parsed = Number.parseInt(value, 10);
-  return Number.isFinite(parsed) ? parsed : null;
-};
-
 const stripGeminiModelResourceName = (value: string) => {
   return String(value ?? '')
     .trim()
@@ -116,7 +111,7 @@ export function AiProvidersGeminiEditPage() {
   const modelDiscoveryRequestIdRef = useRef(0);
 
   const hasIndexParam = typeof params.index === 'string';
-  const editIndex = useMemo(() => parseIndexParam(params.index), [params.index]);
+  const editIndex = useMemo(() => parseRouteIndexParam(params.index), [params.index]);
   const invalidIndexParam = hasIndexParam && editIndex === null;
 
   const initialData = useMemo(() => {
diff --git a/src/pages/AiProvidersOpenAIEditLayout.tsx b/src/pages/AiProvidersOpenAIEditLayout.tsx
index 6ef9997..8abef23 100644
--- a/src/pages/AiProvidersOpenAIEditLayout.tsx
+++ b/src/pages/AiProvidersOpenAIEditLayout.tsx
@@ -10,6 +10,7 @@ import type { ApiKeyEntry, OpenAIProviderConfig } from '@/types';
 import type { ModelInfo } from '@/utils/models';
 import { buildHeaderObject, headersToEntries, normalizeHeaderEntries } from '@/utils/headers';
 import { areKeyValueEntriesEqual, areModelEntriesEqual } from '@/utils/compare';
+import { parseRouteIndexParam } from '@/utils/routeParams';
 import { buildApiKeyEntry } from '@/components/providers/utils';
 import type { ModelEntry, OpenAIFormState } from '@/components/providers/types';
 import type { KeyTestStatus, OpenAIEditBaseline } from '@/stores/useOpenAIEditDraftStore';
@@ -52,12 +53,6 @@ const buildEmptyForm = (): OpenAIFormState => ({
   testModel: undefined,
 });
 
-const parseIndexParam = (value: string | undefined) => {
-  if (!value) return null;
-  const parsed = Number.parseInt(value, 10);
-  return Number.isFinite(parsed) ? parsed : null;
-};
-
 const getErrorMessage = (err: unknown) => {
   if (err instanceof Error) return err.message;
   if (typeof err === 'string') return err;
@@ -140,7 +135,7 @@ export function AiProvidersOpenAIEditLayout() {
 
   const params = useParams<{ index?: string }>();
   const hasIndexParam = typeof params.index === 'string';
-  const editIndex = useMemo(() => parseIndexParam(params.index), [params.index]);
+  const editIndex = useMemo(() => parseRouteIndexParam(params.index), [params.index]);
   const invalidIndexParam = hasIndexParam && editIndex === null;
 
   const connectionStatus = useAuthStore((state) => state.connectionStatus);
diff --git a/src/pages/AiProvidersVertexEditPage.tsx b/src/pages/AiProvidersVertexEditPage.tsx
index be0c3c1..8ad87e8 100644
--- a/src/pages/AiProvidersVertexEditPage.tsx
+++ b/src/pages/AiProvidersVertexEditPage.tsx
@@ -16,6 +16,7 @@ import type { ProviderKeyConfig } from '@/types';
 import { excludedModelsToText, parseExcludedModels } from '@/components/providers/utils';
 import { buildHeaderObject, headersToEntries, normalizeHeaderEntries } from '@/utils/headers';
 import { areKeyValueEntriesEqual, areModelEntriesEqual, areStringArraysEqual } from '@/utils/compare';
+import { parseRouteIndexParam } from '@/utils/routeParams';
 import type { VertexFormState } from '@/components/providers';
 import layoutStyles from './AiProvidersEditLayout.module.scss';
 
@@ -33,12 +34,6 @@ const buildEmptyForm = (): VertexFormState => ({
   excludedText: '',
 });
 
-const parseIndexParam = (value: string | undefined) => {
-  if (!value) return null;
-  const parsed = Number.parseInt(value, 10);
-  return Number.isFinite(parsed) ? parsed : null;
-};
-
 const normalizeModelEntries = (entries: Array<{ name: string; alias: string }>) =>
   (entries ?? []).reduce<Array<{ name: string; alias: string }>>((acc, entry) => {
     const name = String(entry?.name ?? '').trim();
@@ -93,7 +88,7 @@ export function AiProvidersVertexEditPage() {
   const [baseline, setBaseline] = useState(() => buildVertexBaseline(buildEmptyForm()));
 
   const hasIndexParam = typeof params.index === 'string';
-  const editIndex = useMemo(() => parseIndexParam(params.index), [params.index]);
+  const editIndex = useMemo(() => parseRouteIndexParam(params.index), [params.index]);
   const invalidIndexParam = hasIndexParam && editIndex === null;
 
   const initialData = useMemo(() => {
diff --git a/src/utils/routeParams.ts b/src/utils/routeParams.ts
new file mode 100644
index 0000000..4131a90
--- /dev/null
+++ b/src/utils/routeParams.ts
@@ -0,0 +1,10 @@
+const ROUTE_INDEX_PATTERN = /^(0|[1-9]\d*)$/;
+
+export function parseRouteIndexParam(value: string | undefined): number | null {
+  // Route indexes must be canonical digits only; parseInt would accept values like "1abc"
+  // and could route a malformed URL to a real provider entry.
+  if (!value || !ROUTE_INDEX_PATTERN.test(value)) return null;
+
+  const parsed = Number(value);
+  return Number.isSafeInteger(parsed) ? parsed : null;
+}