fix(model-config): keep model selection valid and fix admin panel edge cases

- Fall back to the default server model when a saved one disappears
- Sync model config across tabs
- Validation uses the base path and sends the access code
- Model ids edited as drafts (no empty, duplicate or padded ids)
- Credential changes reset validation; stale validation results are dropped
- Admin: generateId over HTTP, env-locked group switches, discard and toggle fixes,
  clearing a secret field keeps the saved key, first provider not auto-default when .env sets AI_MODEL
- Model selector items use unique values

tests/unit/admin-secret-input.test.tsx

@@ -0,0 +1,87 @@
+import { cleanup, fireEvent, render, screen } from "@testing-library/react"
+import type { ReactNode } from "react"
+import { afterEach, describe, expect, it, vi } from "vitest"
+import { SecretInput, SettingField } from "@/app/[lang]/admin/setting-field"
+import { DictionaryProvider } from "@/hooks/use-dictionary"
+import type { SettingDef } from "@/lib/admin/settings-registry"
+import type { Dictionary } from "@/lib/i18n/dictionaries"
+import en from "@/lib/i18n/dictionaries/en.json"
+
+const STORED = { isSet: true as const, hint: "…abcd" }
+
+function withDict(node: ReactNode) {
+    return (
+        <DictionaryProvider dictionary={en as unknown as Dictionary}>
+            {node}
+        </DictionaryProvider>
+    )
+}
+
+function typeInto(label: string, text: string) {
+    fireEvent.change(screen.getByLabelText(label, { selector: "input" }), {
+        target: { value: text },
+    })
+}
+
+afterEach(cleanup)
+
+describe("SecretInput", () => {
+    it("reverts to a key saved after mount instead of deleting it", () => {
+        const onChange = vi.fn()
+        const props = { id: "secret", keepOnEmpty: true, onChange }
+        // New provider: nothing stored at mount, then saved
+        const { rerender } = render(
+            withDict(
+                <>
+                    <label htmlFor="secret">secret</label>
+                    <SecretInput {...props} value={undefined} />
+                </>,
+            ),
+        )
+        rerender(
+            withDict(
+                <>
+                    <label htmlFor="secret">secret</label>
+                    <SecretInput {...props} value={STORED} />
+                </>,
+            ),
+        )
+        rerender(
+            withDict(
+                <>
+                    <label htmlFor="secret">secret</label>
+                    <SecretInput {...props} value="abc" />
+                </>,
+            ),
+        )
+
+        typeInto("secret", "")
+        expect(onChange).toHaveBeenLastCalledWith(STORED)
+    })
+})
+
+describe("SettingField secret", () => {
+    const def: SettingDef = {
+        key: "LANGFUSE_SECRET_KEY",
+        group: "observability",
+        type: "secret",
+        label: "Langfuse Secret Key",
+    }
+
+    it("drops the pending change when a saved secret is typed over and cleared", () => {
+        const onChange = vi.fn()
+        const props = {
+            def,
+            state: { key: def.key, source: "file" as const, value: STORED },
+            disabled: false,
+            onChange,
+        }
+        const { rerender } = render(
+            withDict(<SettingField {...props} pendingValue={undefined} />),
+        )
+        rerender(withDict(<SettingField {...props} pendingValue="a" />))
+
+        typeInto(en.admin.settings.LANGFUSE_SECRET_KEY.label, "")
+        expect(onChange).toHaveBeenLastCalledWith(undefined)
+    })
+})

tests/unit/use-model-config.test.tsx

@@ -0,0 +1,133 @@
+import { act, cleanup, renderHook, waitFor } from "@testing-library/react"
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
+import { useModelConfig } from "@/hooks/use-model-config"
+import type { FlattenedServerModel } from "@/lib/server-model-config"
+import { STORAGE_KEYS } from "@/lib/storage"
+import type { MultiModelConfig } from "@/lib/types/model-config"
+
+const SERVER_MODELS: FlattenedServerModel[] = [
+    {
+        id: "server:openai-main:gpt-4o-mini",
+        modelId: "gpt-4o-mini",
+        provider: "openai",
+        providerLabel: "OpenAI Main",
+        isDefault: false,
+    },
+    {
+        id: "server:openai-main:gpt-4o",
+        modelId: "gpt-4o",
+        provider: "openai",
+        providerLabel: "OpenAI Main",
+        isDefault: true,
+    },
+]
+
+const USER_CONFIG: MultiModelConfig = {
+    version: 1,
+    providers: [
+        {
+            id: "p1",
+            provider: "openai",
+            apiKey: "sk-test",
+            models: [{ id: "m1", modelId: "gpt-4o" }],
+        },
+    ],
+}
+
+function storeConfig(config: MultiModelConfig) {
+    localStorage.setItem(STORAGE_KEYS.modelConfigs, JSON.stringify(config))
+}
+
+async function renderLoaded() {
+    const hook = renderHook(() => useModelConfig())
+    await waitFor(() => expect(hook.result.current.isLoaded).toBe(true))
+    return hook
+}
+
+beforeEach(() => {
+    localStorage.clear()
+    vi.stubGlobal(
+        "fetch",
+        vi.fn(async () => ({
+            ok: true,
+            json: async () => ({ models: SERVER_MODELS }),
+        })),
+    )
+})
+
+afterEach(() => {
+    cleanup()
+    vi.unstubAllGlobals()
+})
+
+describe("useModelConfig server model selection", () => {
+    it("replaces a saved server model that no longer exists", async () => {
+        storeConfig({
+            ...USER_CONFIG,
+            selectedModelId: "server:openai-production:gpt-4o",
+        })
+        const { result } = await renderLoaded()
+        expect(result.current.selectedModelId).toBe("server:openai-main:gpt-4o")
+    })
+
+    it("keeps a saved server model that still exists", async () => {
+        storeConfig({
+            ...USER_CONFIG,
+            selectedModelId: "server:openai-main:gpt-4o-mini",
+        })
+        const { result } = await renderLoaded()
+        expect(result.current.selectedModelId).toBe(
+            "server:openai-main:gpt-4o-mini",
+        )
+    })
+
+    it("keeps a selected user model", async () => {
+        storeConfig({ ...USER_CONFIG, selectedModelId: "m1" })
+        const { result } = await renderLoaded()
+        expect(result.current.selectedModelId).toBe("m1")
+    })
+
+    it("falls back to the default server model when the selected model is deleted", async () => {
+        storeConfig({ ...USER_CONFIG, selectedModelId: "m1" })
+        const { result } = await renderLoaded()
+        act(() => result.current.deleteModel("p1", "m1"))
+        expect(result.current.selectedModelId).toBe("server:openai-main:gpt-4o")
+    })
+
+    it("falls back to the default server model when the selected provider is deleted", async () => {
+        storeConfig({ ...USER_CONFIG, selectedModelId: "m1" })
+        const { result } = await renderLoaded()
+        act(() => result.current.deleteProvider("p1"))
+        expect(result.current.selectedModelId).toBe("server:openai-main:gpt-4o")
+    })
+})
+
+describe("useModelConfig across tabs", () => {
+    it("reloads the config when another tab saves it", async () => {
+        storeConfig({ ...USER_CONFIG, selectedModelId: "m1" })
+        const { result } = await renderLoaded()
+
+        const fromOtherTab: MultiModelConfig = {
+            ...USER_CONFIG,
+            providers: [
+                ...USER_CONFIG.providers,
+                {
+                    id: "p2",
+                    provider: "anthropic",
+                    apiKey: "sk-ant",
+                    models: [{ id: "m2", modelId: "claude-sonnet-4-5" }],
+                },
+            ],
+            selectedModelId: "m2",
+        }
+        act(() => {
+            storeConfig(fromOtherTab)
+            window.dispatchEvent(
+                new StorageEvent("storage", { key: STORAGE_KEYS.modelConfigs }),
+            )
+        })
+
+        expect(result.current.selectedModelId).toBe("m2")
+        expect(result.current.config.providers).toHaveLength(2)
+    })
+})