diff --git a/config/quality/file-size-baseline.json b/config/quality/file-size-baseline.json
index d2a5990b436..2fbf0cfbf1f 100644
--- a/config/quality/file-size-baseline.json
+++ b/config/quality/file-size-baseline.json
@@ -1,5 +1,6 @@
 {
   "_comment": "Catraca de tamanho (check-file-size.mjs). frozen so pode encolher; arquivos novos <= cap. --update ratcheta.",
+  "_rebaseline_2026_06_20_4023_web_cookie_noauth_validation": "PR #4023 (oyi77) own growth: src/lib/providers/validation.ts 4450->4518 (+68 = a new validateWebCookieProvider that probes the provider's /models endpoint — 401/403 => AUTH_007 SESSION_EXPIRED, any other status => valid session, empty cookie => invalid, provider-not-in-registry => unsupported — plus a local STANDARD_USER_AGENT const for the probe). Cohesive validator at the validateProviderApiKey dispatch; not extractable. Covered by tests/unit/provider-validation-web-cookie-auth007.test.ts. Heavily curated on merge — the PR's branch was badly stale-based (squash-base-stale), so its tree was DESTRUCTIVE: providers/index.ts deleted live providers openadapter/dit/tokenrouter (added by #4313) and the executor/base.ts edits reverted release fixes (#4037 duckduckgo host, theoldllm gpt5 models, base.ts fetch-start-timeout). Only the purely-additive validation feature was kept (validation.ts validateWebCookieProvider + errorCodes AUTH_007 + the test). Dropped: 5 malformed new registry entries (used non-RegistryEntry fields defaultModel/auth + referenced non-existent executors -> tsc TS2353), the destructive providers/index.ts + executor reverts, the unrelated pr-*.sh automation scripts, and evals/types.ts (belongs to the deferred evals modularization #4422). Also removed the PR's fragile 'Phase 2' executor probe (ran a live upstream chat during validation + classified any 'auth'-containing error as SESSION_EXPIRED) and rewrote the test to install its fetch mock before module load (the original mocked too late and silently hit live chatgpt.com).",
   "_rebaseline_2026_06_20_3368_pool_tools": "PR #3368 own growth: open-sse/mcp-server/server.ts 1468->1509 (+41 = register the web-session pool observability tools — poolStatus/poolSessions/poolWarm — at the existing createMcpServer registration chokepoint, with their read:health/write:resilience scope wiring). Reconciled late: the server.ts bump was a separate commit that did not ride along when the feature commit was cherry-picked onto release/v3.8.32 (squash-base-stale rebuild). Thin cohesive registration at the single tool-registration boundary; not extractable. Covered by tests/unit/mcp-pool-tools-3368.test.ts.",
   "_rebaseline_2026_06_20_4401_webfetch_validators": "PR #4401 own growth: src/lib/providers/validation.ts 4428->4450 (+22 = two new API-key validators — Firecrawl + Jina Reader — each a cohesive provider validator branch mirroring the existing ones; 401/403->invalid else->valid). Not extractable (it IS the per-provider validator list). Covered by tests/unit/provider-validation-webfetch-4401.test.ts.",
   "_rebaseline_2026_06_20_4380_parse_once": "PR #4380 own growth: src/sse/handlers/chat.ts 1486->1491 (+5 = thread the once-parsed request body from the route guard into handleChat, replacing the duplicate re-parse). The reusable body accessor lives in the new src/sse/handlers/requestBody.ts (<cap). Thin wiring at the single entry chokepoint; not extractable. Covered by tests/unit/chat-request-body-parse-once-4380.test.ts.",
@@ -171,7 +172,7 @@
     "src/lib/evals/evalRunner.ts": 961,
     "src/lib/memory/retrieval.ts": 1171,
     "src/lib/modelsDevSync.ts": 934,
-    "src/lib/providers/validation.ts": 4450,
+    "src/lib/providers/validation.ts": 4518,
     "src/lib/tailscaleTunnel.ts": 1202,
     "src/lib/usage/callLogs.ts": 975,
     "src/lib/usage/providerLimits.ts": 949,
diff --git a/src/lib/providers/validation.ts b/src/lib/providers/validation.ts
index 73ba1948173..c6904d715cc 100644
--- a/src/lib/providers/validation.ts
+++ b/src/lib/providers/validation.ts
@@ -20,6 +20,7 @@ import {
   isOpenAICompatibleProvider,
   isSelfHostedChatProvider,
   providerAllowsOptionalApiKey,
+  WEB_COOKIE_PROVIDERS,
 } from "@/shared/constants/providers";
 import {
   SAFE_OUTBOUND_FETCH_PRESETS,
@@ -190,6 +191,10 @@ function normalizeGigachatChatUrl(baseUrl: string) {
   return `${normalized}/chat/completions`;
 }
 
+// Standardized desktop Chrome UA for web-cookie/no-auth session probes (minimizes anti-bot detection).
+const STANDARD_USER_AGENT =
+  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36";
+
 function getCustomUserAgent(providerSpecificData: any = {}) {
   if (typeof providerSpecificData?.customUserAgent !== "string") return null;
   const customUserAgent = providerSpecificData.customUserAgent.trim();
@@ -3932,6 +3937,60 @@ async function validateInnerAiProvider({ apiKey, providerSpecificData = {} }: an
     return toValidationErrorResult(error);
   }
 }
+/**
+ * Validates web-cookie providers by performing a ping request to check if the session is still valid.
+ * Returns SESSION_EXPIRED error code if the upstream returns 401/403.
+ */
+export async function validateWebCookieProvider({
+  provider,
+  apiKey,
+  providerSpecificData = {},
+}: any) {
+  try {
+    const entry = getRegistryEntry(provider);
+    if (!entry) {
+      return { valid: false, error: "Provider not found in registry", unsupported: true };
+    }
+
+    // For web-cookie providers, apiKey contains the cookie string
+    const cookie = (apiKey || "").trim();
+    if (!cookie) {
+      return { valid: false, error: "Cookie required for web-cookie provider", unsupported: false };
+    }
+
+    // Attempt a minimal request to check if the session is valid
+    // Use /models endpoint or a minimal completion request depending on the provider
+    const baseUrl = entry.baseUrl || "";
+    const testUrl = `${baseUrl}/models`;
+
+    const res = await directHttpsRequest(
+      testUrl,
+      {
+        method: "GET",
+        headers: {
+          "User-Agent": STANDARD_USER_AGENT,
+        },
+      },
+      10_000
+    );
+
+    if (res.status === 401 || res.status === 403) {
+      return {
+        valid: false,
+        error: "SESSION_EXPIRED",
+        errorCode: "AUTH_007",
+        unsupported: false,
+      };
+    }
+
+    // Any other response (200, 404, 405, 429, ...) means the cookie was accepted —
+    // a 401/403 from the /models probe is the only definitive "session expired" signal
+    // for web-cookie auth, so a non-auth status is treated as a valid session.
+    return { valid: true, error: null, unsupported: false };
+  } catch (error: any) {
+    return toValidationErrorResult(error);
+  }
+}
 
 export async function validateProviderApiKey({ provider, apiKey, providerSpecificData = {} }: any) {
   const requiresApiKey = !providerAllowsOptionalApiKey(provider);
@@ -3941,6 +4000,15 @@ export async function validateProviderApiKey({ provider, apiKey, providerSpecifi
     return { valid: false, error: "Provider and API key required", unsupported: false };
   }
 
+  // Web-cookie providers (session-based authentication)
+  if (WEB_COOKIE_PROVIDERS[provider]) {
+    try {
+      return await validateWebCookieProvider({ provider, apiKey, providerSpecificData });
+    } catch (error: any) {
+      return toValidationErrorResult(error);
+    }
+  }
+
   if (isOpenAICompatibleProvider(provider)) {
     try {
       return await validateOpenAICompatibleProvider({ apiKey, providerSpecificData });
diff --git a/src/shared/constants/errorCodes.ts b/src/shared/constants/errorCodes.ts
index 661e913d8de..99a40ca6f06 100644
--- a/src/shared/constants/errorCodes.ts
+++ b/src/shared/constants/errorCodes.ts
@@ -47,6 +47,12 @@ export const ERROR_CODES: Record<string, ErrorCodeDef> = {
     httpStatus: 400,
     category: "AUTH",
   },
+  AUTH_007: {
+    code: "AUTH_007",
+    message: "Session expired (re-login required)",
+    httpStatus: 401,
+    category: "AUTH",
+  },
 
   // ── Proxy ──
   PROXY_001: {
diff --git a/tests/unit/provider-validation-web-cookie-auth007.test.ts b/tests/unit/provider-validation-web-cookie-auth007.test.ts
new file mode 100644
index 00000000000..c53705af040
--- /dev/null
+++ b/tests/unit/provider-validation-web-cookie-auth007.test.ts
@@ -0,0 +1,102 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+// The validator probes the provider's /models endpoint via safeOutboundFetch →
+// fetchWithTimeout, which binds globalThis.fetch at MODULE LOAD time. The mock MUST be
+// installed BEFORE importing validation.ts — a late reassignment (inside a test) is
+// ignored and the validator hits the real network instead. (That made the 401/403
+// assertions pass only by coincidence — live chatgpt.com returns 401/403 — while the
+// 200 case failed.) A mutable `nextResponse` lets each test vary the probe result, and
+// `fetchCalls` proves the mocked probe ran rather than the live network.
+let nextResponse: { status: number; body: string } = { status: 200, body: "{}" };
+let fetchCalls = 0;
+globalThis.fetch = (async () => {
+  fetchCalls++;
+  return new Response(nextResponse.body, {
+    status: nextResponse.status,
+    headers: { "content-type": "application/json" },
+  });
+}) as typeof fetch;
+
+const { validateWebCookieProvider } = await import("../../src/lib/providers/validation.ts");
+
+function mockFetch(status: number, body: string) {
+  nextResponse = { status, body };
+  fetchCalls = 0;
+}
+
+test("should_return_AUTH_007_when_models_endpoint_returns_401", async () => {
+  mockFetch(401, JSON.stringify({ error: "unauthorized" }));
+
+  const result = await validateWebCookieProvider({
+    provider: "chatgpt-web",
+    apiKey: "expired_cookie=session=abc123",
+    providerSpecificData: {},
+  });
+
+  assert.equal(fetchCalls, 1, "the /models probe must be the mocked fetch, not the live network");
+  assert.equal(result.valid, false);
+  assert.equal(result.errorCode, "AUTH_007");
+  assert.equal(result.error, "SESSION_EXPIRED");
+});
+
+test("should_return_AUTH_007_when_models_endpoint_returns_403", async () => {
+  mockFetch(403, JSON.stringify({ error: "forbidden" }));
+
+  const result = await validateWebCookieProvider({
+    provider: "chatgpt-web",
+    apiKey: "expired_cookie=session=abc123",
+    providerSpecificData: {},
+  });
+
+  assert.equal(fetchCalls, 1, "the /models probe must be the mocked fetch, not the live network");
+  assert.equal(result.valid, false);
+  assert.equal(result.errorCode, "AUTH_007");
+  assert.equal(result.error, "SESSION_EXPIRED");
+});
+
+test("should_return_valid_when_models_endpoint_returns_200", async () => {
+  // A non-401/403 status from the /models probe means the cookie was accepted,
+  // so the session is treated as valid.
+  mockFetch(200, JSON.stringify({ ok: true, data: [] }));
+
+  const result = await validateWebCookieProvider({
+    provider: "chatgpt-web",
+    apiKey: "valid_cookie=session=abc123",
+    providerSpecificData: {},
+  });
+
+  assert.equal(fetchCalls, 1, "the /models probe must be the mocked fetch, not the live network");
+  assert.equal(result.valid, true);
+});
+
+test("should_return_unsupported_when_provider_not_in_registry", async () => {
+  mockFetch(200, "{}");
+
+  const result = await validateWebCookieProvider({
+    provider: "nonexistent-provider",
+    apiKey: "some_cookie",
+    providerSpecificData: {},
+  });
+
+  // Unknown provider short-circuits before any network probe.
+  assert.equal(fetchCalls, 0);
+  assert.equal(result.valid, false);
+  assert.equal(result.unsupported, true);
+});
+
+test("should_return_error_when_cookie_is_empty", async () => {
+  mockFetch(200, "{}");
+
+  const result = await validateWebCookieProvider({
+    provider: "chatgpt-web",
+    apiKey: "",
+    providerSpecificData: {},
+  });
+
+  // Empty cookie short-circuits before any network probe.
+  assert.equal(fetchCalls, 0);
+  assert.equal(result.valid, false);
+  assert.equal(result.unsupported, false);
+  assert.match(result.error, /cookie/i);
+});