refactor: drop request-body token override, keep env-only config

The unauthenticated /api/validate-model endpoint should not let callers
raise the token budget; the env var / admin setting alone fixes #883.
Also import the shared constants in the settings registry instead of
duplicating them, and move the setting to the Features group alongside
the other validation settings.

app/api/validate-model/route.ts

@@ -32,9 +32,6 @@ interface ValidateRequest {
     awsRegion?: string
     // Vertex AI specific
     vertexApiKey?: string // Express Mode API key
-    // Optional test token budget override
-    maxTokens?: number
-    max_tokens?: number
 }
 
 export async function POST(req: Request) {
@@ -52,8 +49,6 @@ export async function POST(req: Request) {
             vertexApiKey,
         } = body
         const validationMaxTokens = resolveModelValidationMaxTokens(
-            body.maxTokens,
-            body.max_tokens,
             process.env.MODEL_VALIDATION_MAX_TOKENS,
         )
 

lib/admin/settings-registry.ts

@@ -10,6 +10,11 @@
 // - ADMIN_PASSWORD / SETTINGS_FILE: bootstrap values, env-only to avoid lockout
 // - Per-provider reasoning/thinking tuning vars: env-only (see env.example)
 
+import {
+    DEFAULT_MODEL_VALIDATION_MAX_TOKENS,
+    MAX_MODEL_VALIDATION_MAX_TOKENS,
+} from "@/lib/model-validation"
+
 export type SettingType = "string" | "secret" | "number" | "boolean" | "enum"
 
 export interface SettingDef {
@@ -88,17 +93,6 @@ export const SETTINGS_REGISTRY: SettingDef[] = [
         label: "Max Output Tokens",
         min: 1,
     },
-    {
-        key: "MODEL_VALIDATION_MAX_TOKENS",
-        group: "generation",
-        type: "number",
-        label: "Model Validation Max Tokens",
-        description:
-            "Token budget for model test requests. Increase for reasoning models that may emit thinking tokens first.",
-        min: 1,
-        max: 64000,
-        default: "1000",
-    },
 
     // ── Access Control ───────────────────────────────────────────────
     {
@@ -134,6 +128,17 @@ export const SETTINGS_REGISTRY: SettingDef[] = [
         label: "Validation Timeout (ms)",
         min: 1000,
     },
+    {
+        key: "MODEL_VALIDATION_MAX_TOKENS",
+        group: "features",
+        type: "number",
+        label: "Model Validation Max Tokens",
+        description:
+            "Token budget for model test requests. Increase for reasoning models that may emit thinking tokens first.",
+        min: 1,
+        max: MAX_MODEL_VALIDATION_MAX_TOKENS,
+        default: String(DEFAULT_MODEL_VALIDATION_MAX_TOKENS),
+    },
     {
         key: "ENABLE_HISTORY_XML_REPLACE",
         group: "features",

lib/model-validation.ts

@@ -7,22 +7,16 @@ export function parseModelValidationMaxTokens(value: unknown): number | null {
     const numeric =
         typeof value === "number" ? value : Number(String(value).trim())
 
-    if (
-        !Number.isFinite(numeric) ||
-        !Number.isInteger(numeric) ||
-        numeric < 1
-    ) {
+    if (!Number.isInteger(numeric) || numeric < 1) {
         return null
     }
 
     return Math.min(numeric, MAX_MODEL_VALIDATION_MAX_TOKENS)
 }
 
-export function resolveModelValidationMaxTokens(...sources: unknown[]): number {
-    for (const source of sources) {
-        const parsed = parseModelValidationMaxTokens(source)
-        if (parsed !== null) return parsed
-    }
-
-    return DEFAULT_MODEL_VALIDATION_MAX_TOKENS
+export function resolveModelValidationMaxTokens(value: unknown): number {
+    return (
+        parseModelValidationMaxTokens(value) ??
+        DEFAULT_MODEL_VALIDATION_MAX_TOKENS
+    )
 }

tests/unit/model-validation.test.ts

@@ -8,14 +8,23 @@ import {
 
 describe("model validation token budget", () => {
     it("defaults to a larger reasoning-friendly budget", () => {
-        expect(resolveModelValidationMaxTokens()).toBe(
+        expect(resolveModelValidationMaxTokens(undefined)).toBe(
             DEFAULT_MODEL_VALIDATION_MAX_TOKENS,
         )
     })
 
-    it("prefers the first valid source", () => {
-        expect(resolveModelValidationMaxTokens(2000, 3000)).toBe(2000)
-        expect(resolveModelValidationMaxTokens("bad", "3000")).toBe(3000)
+    it("parses valid env values", () => {
+        expect(resolveModelValidationMaxTokens("2000")).toBe(2000)
+        expect(resolveModelValidationMaxTokens(" 300 ")).toBe(300)
+    })
+
+    it("falls back to the default on invalid values", () => {
+        expect(resolveModelValidationMaxTokens("abc")).toBe(
+            DEFAULT_MODEL_VALIDATION_MAX_TOKENS,
+        )
+        expect(resolveModelValidationMaxTokens("")).toBe(
+            DEFAULT_MODEL_VALIDATION_MAX_TOKENS,
+        )
     })
 
     it("rejects invalid values", () => {