diff --git a/plugins/admin/src/index.ts b/plugins/admin/src/index.ts
index d0415cd81..fb0386175 100644
--- a/plugins/admin/src/index.ts
+++ b/plugins/admin/src/index.ts
@@ -7,6 +7,7 @@ import { signedRequestHeaders, withSourceAuthNonce } from "../../chassis/src/cor
 import { json, readBody, cookie } from "../../chassis/src/http.ts";
 import { createBrandingCache, injectBranding, type OrgBranding } from "../../chassis/src/branding.ts";
 import { verifyPortalIdentity, PORTAL_IDENTITY_HEADER } from "../../chassis/src/portal-identity.ts";
+import { errMessage } from "../../chassis/src/errors.ts";
 import {
   CORE_API_URL as CORE,
   CORE_ORG_ID as ORG,
@@ -20,6 +21,9 @@ import { dirname, join } from "node:path";
 
 const PORT = portFromEnv(8090);
 const ADMIN_BASE_PATH = (process.env.ADMIN_BASE_PATH ?? "").replace(/\/$/, "");
+const CORE_WHOAMI_ATTEMPTS = 2;
+const CORE_WHOAMI_TIMEOUT_MS = 2_500;
+const CORE_WHOAMI_RETRY_DELAY_MS = 250;
 function signedHeaders(method: string, corePath: string, rawBody: string): Record<string, string> {
   return signedRequestHeaders(CORE_SIGNING_SECRET, method, corePath, rawBody, { "content-type": "application/json" });
 }
@@ -243,19 +247,37 @@ async function uploadFileFromRequest(
 
 async function coreWhoami(principal: string): Promise<{ isAdmin: boolean; role?: string; scopeId?: string } | null> {
   const corePath = "/v1/admin/whoami";
-  try {
-    const r = await fetch(`${CORE}${corePath}`, {
-      headers: {
-        ...signedHeaders("GET", corePath, ""),
-        ...portalIdentityHeader(),
-        "x-admin-actor": `${principal}@${ORG}`,
-      },
-    });
-    if (!r.ok) return null;
-    return (await r.json()) as { isAdmin: boolean; role?: string; scopeId?: string };
-  } catch {
-    return null;
+  const started = Date.now();
+  let failure = "unknown failure";
+  let attempts = 0;
+  for (; attempts < CORE_WHOAMI_ATTEMPTS; attempts++) {
+    try {
+      const r = await fetch(`${CORE}${corePath}`, {
+        headers: {
+          ...signedHeaders("GET", corePath, ""),
+          ...portalIdentityHeader(),
+          "x-admin-actor": `${principal}@${ORG}`,
+        },
+        signal: AbortSignal.timeout(CORE_WHOAMI_TIMEOUT_MS),
+      });
+      if (r.ok) {
+        const body = (await r.json()) as { isAdmin?: unknown; role?: string; scopeId?: string };
+        if (typeof body.isAdmin !== "boolean") throw new Error("core returned an invalid admin status");
+        return { ...body, isAdmin: body.isAdmin };
+      }
+      failure = `HTTP ${r.status}`;
+      if (r.status < 500 && r.status !== 429) break;
+    } catch (error) {
+      failure = errMessage(error);
+    }
+    if (attempts + 1 < CORE_WHOAMI_ATTEMPTS) {
+      await new Promise((resolve) => setTimeout(resolve, CORE_WHOAMI_RETRY_DELAY_MS));
+    }
   }
+  console.warn(
+    `[admin] core whoami failed after ${Math.min(attempts + 1, CORE_WHOAMI_ATTEMPTS)} attempt(s) in ${Date.now() - started}ms: ${failure}`,
+  );
+  return null;
 }
 
 const WRITES = new Map<string, string[]>([
diff --git a/plugins/admin/test/whoami.test.ts b/plugins/admin/test/whoami.test.ts
index 27233e453..db7762a25 100644
--- a/plugins/admin/test/whoami.test.ts
+++ b/plugins/admin/test/whoami.test.ts
@@ -7,8 +7,16 @@ import { mintPortalIdentity } from "../../chassis/src/portal-identity.ts";
 let lastActor: string | null = null;
 let lastSigned = false;
 let lastPortalIdentity: string | null = null;
+let transientWhoamiFailures = 0;
+let whoamiRequests = 0;
 const core = createServer((req: IncomingMessage, res) => {
   if (req.method === "GET" && (req.url ?? "").startsWith("/v1/admin/whoami")) {
+    whoamiRequests++;
+    if (transientWhoamiFailures > 0) {
+      transientWhoamiFailures--;
+      res.writeHead(502, { "content-type": "application/json" });
+      return void res.end(JSON.stringify({ error: "temporarily_unavailable" }));
+    }
     lastActor = (req.headers["x-admin-actor"] as string) ?? null;
     lastSigned = Boolean(req.headers["x-timestamp"] && req.headers["x-signature"]);
     lastPortalIdentity = (req.headers["x-portal-identity"] as string) ?? null;
@@ -134,6 +142,15 @@ test("an unsigned or wrongly-signed portal identity is not accepted as an admin
   }
 });
 
+test("a transient core failure is retried before admin bootstrap fails", async () => {
+  transientWhoamiFailures = 1;
+  whoamiRequests = 0;
+  const r = await api("/api/me", "admin=U-admin");
+  assert.equal(r.status, 200);
+  assert.equal(whoamiRequests, 2);
+  assert.equal(((await r.json()) as { isAdmin?: boolean }).isAdmin, true);
+});
+
 test("core unreachable → /api/whoami returns 502 core_unreachable (outage, not a not-admin verdict)", async () => {
   await new Promise<void>((r) => core.close(() => r()));
   const r = await api("/api/whoami", "admin=U-admin");
diff --git a/plugins/portal/src/index.ts b/plugins/portal/src/index.ts
index a0abdee9d..fcb7ff941 100644
--- a/plugins/portal/src/index.ts
+++ b/plugins/portal/src/index.ts
@@ -201,8 +201,9 @@ export function consumeState(state: string): boolean {
 }
 
 const ADMIN_TTL_MS = 60_000;
-const ADMIN_PROBE_TIMEOUT_MS = 1500;
+const ADMIN_PROBE_TIMEOUT_MS = 6_500;
 const ADMIN_PROBE_ATTEMPTS = 2;
+const ADMIN_PROBE_RETRY_DELAY_MS = 250;
 const adminCache = new LRUCache<string, boolean>({ max: 10_000, ttl: ADMIN_TTL_MS });
 
 async function adminProbeAttempt(sub: string): Promise<boolean | null> {
@@ -217,10 +218,18 @@ async function adminProbeAttempt(sub: string): Promise<boolean | null> {
       );
     }
     const r = await fetch(`${UPSTREAMS.admin}/api/whoami`, { headers, signal: ctrl.signal });
-    if (!r.ok) return null;
-    const j = (await r.json()) as { isAdmin?: boolean };
-    return j.isAdmin === true;
-  } catch {
+    if (!r.ok) {
+      console.warn(`[portal] admin probe returned HTTP ${r.status}`);
+      return null;
+    }
+    const j = (await r.json()) as { isAdmin?: unknown };
+    if (typeof j.isAdmin !== "boolean") {
+      console.warn("[portal] admin probe returned an invalid admin status");
+      return null;
+    }
+    return j.isAdmin;
+  } catch (error) {
+    console.warn(`[portal] admin probe failed: ${errMessage(error)}`);
     return null;
   } finally {
     clearTimeout(timer);
@@ -232,7 +241,11 @@ async function adminProbe(sub: string): Promise<{ isAdmin: boolean; failed: bool
   if (hit !== undefined) return { isAdmin: hit, failed: false };
   for (let attempt = 0; attempt < ADMIN_PROBE_ATTEMPTS; attempt++) {
     const isAdmin = await adminProbeAttempt(sub);
-    if (isAdmin === null) continue;
+    if (isAdmin === null) {
+      if (attempt + 1 < ADMIN_PROBE_ATTEMPTS)
+        await new Promise((resolve) => setTimeout(resolve, ADMIN_PROBE_RETRY_DELAY_MS));
+      continue;
+    }
     adminCache.set(sub, isAdmin);
     return { isAdmin, failed: false };
   }
diff --git a/plugins/portal/test/proxy-errors.test.ts b/plugins/portal/test/proxy-errors.test.ts
index 255b8d744..413e71390 100644
--- a/plugins/portal/test/proxy-errors.test.ts
+++ b/plugins/portal/test/proxy-errors.test.ts
@@ -5,7 +5,7 @@ import { connect } from "node:net";
 import type { AddressInfo } from "node:net";
 import { verifyPortalIdentity } from "../../chassis/src/portal-identity.ts";
 
-let whoamiMode: "ok" | "down" | "fail-once" = "ok";
+let whoamiMode: "ok" | "down" | "fail-once" | "malformed" = "ok";
 let whoamiRequests = 0;
 
 const upstream = createServer((req: IncomingMessage, res) => {
@@ -15,6 +15,10 @@ const upstream = createServer((req: IncomingMessage, res) => {
       res.writeHead(502, { "content-type": "application/json" });
       return void res.end(JSON.stringify({ error: "core_unreachable" }));
     }
+    if (whoamiMode === "malformed") {
+      res.writeHead(200, { "content-type": "application/json" });
+      return void res.end("{}");
+    }
     const m = (req.headers.cookie ?? "").match(/admin=([^;]+)/);
     const sub = m ? decodeURIComponent(m[1] ?? "") : "";
     res.writeHead(200, { "content-type": "application/json" });
@@ -152,6 +156,16 @@ test("an admin-probe outage is reported as unavailable and is NOT negative-cache
   assert.equal(ok.status, 200);
 });
 
+test("a malformed admin verdict fails readiness instead of being cached as non-admin", async () => {
+  whoamiMode = "malformed";
+  const denied = await fetch(`${base}/admin/`, {
+    headers: { cookie: sessionCookie("U-admin-malformed"), accept: "text/html" },
+  });
+  assert.equal(denied.status, 403);
+  assert.match(await denied.text(), /temporarily unavailable/i);
+  whoamiMode = "ok";
+});
+
 test("consumeState: single-use, TTL-bounded, never wholesale-wiped", () => {
   assert.equal(consumeState("state-a"), true);
   assert.equal(consumeState("state-a"), false, "a consumed state cannot be replayed");