diff --git a/src/plugins/loader-cache-state.ts b/src/plugins/loader-cache-state.ts
index 9cd85f94e6d..4714f8ea114 100644
--- a/src/plugins/loader-cache-state.ts
+++ b/src/plugins/loader-cache-state.ts
@@ -1,3 +1,5 @@
+import { PluginLruCache } from "./plugin-lru-cache.js";
+
 export class PluginLoadReentryError extends Error {
   readonly cacheKey: string;
 
@@ -9,27 +11,20 @@ export class PluginLoadReentryError extends Error {
 }
 
 export class PluginLoaderCacheState<T> {
-  readonly #defaultMaxEntries: number;
-  #maxEntries: number;
-  readonly #registryCache = new Map<string, T>();
+  readonly #registryCache: PluginLruCache<T>;
   readonly #inFlightLoads = new Set<string>();
   readonly #openAllowlistWarningCache = new Set<string>();
 
   constructor(defaultMaxEntries: number) {
-    this.#defaultMaxEntries = Math.max(1, Math.floor(defaultMaxEntries));
-    this.#maxEntries = this.#defaultMaxEntries;
+    this.#registryCache = new PluginLruCache<T>(defaultMaxEntries);
   }
 
   get maxEntries(): number {
-    return this.#maxEntries;
+    return this.#registryCache.maxEntries;
   }
 
   setMaxEntriesForTest(value?: number): void {
-    this.#maxEntries =
-      typeof value === "number" && Number.isFinite(value) && value > 0
-        ? Math.max(1, Math.floor(value))
-        : this.#defaultMaxEntries;
-    this.#evictOldestEntries();
+    this.#registryCache.setMaxEntriesForTest(value);
   }
 
   clear(): void {
@@ -39,21 +34,11 @@ export class PluginLoaderCacheState<T> {
   }
 
   get(cacheKey: string): T | undefined {
-    const cached = this.#registryCache.get(cacheKey);
-    if (!cached) {
-      return undefined;
-    }
-    this.#registryCache.delete(cacheKey);
-    this.#registryCache.set(cacheKey, cached);
-    return cached;
+    return this.#registryCache.get(cacheKey);
   }
 
   set(cacheKey: string, state: T): void {
-    if (this.#registryCache.has(cacheKey)) {
-      this.#registryCache.delete(cacheKey);
-    }
     this.#registryCache.set(cacheKey, state);
-    this.#evictOldestEntries();
   }
 
   isLoadInFlight(cacheKey: string): boolean {
@@ -78,14 +63,4 @@ export class PluginLoaderCacheState<T> {
   recordOpenAllowlistWarning(cacheKey: string): void {
     this.#openAllowlistWarningCache.add(cacheKey);
   }
-
-  #evictOldestEntries(): void {
-    while (this.#registryCache.size > this.#maxEntries) {
-      const oldestEntry = this.#registryCache.keys().next();
-      if (oldestEntry.done) {
-        break;
-      }
-      this.#registryCache.delete(oldestEntry.value);
-    }
-  }
 }
diff --git a/src/plugins/plugin-lru-cache.test.ts b/src/plugins/plugin-lru-cache.test.ts
new file mode 100644
index 00000000000..e514dcb3dd7
--- /dev/null
+++ b/src/plugins/plugin-lru-cache.test.ts
@@ -0,0 +1,42 @@
+import { describe, expect, it } from "vitest";
+import { PluginLruCache } from "./plugin-lru-cache.js";
+
+describe("PluginLruCache", () => {
+  it("evicts the least recently used entry", () => {
+    const cache = new PluginLruCache<string>(2);
+
+    cache.set("", "empty");
+    cache.set("a", "alpha");
+    cache.set("b", "bravo");
+    expect(cache.get("a")).toBe("alpha");
+
+    cache.set("c", "charlie");
+
+    expect(cache.get("b")).toBeUndefined();
+    expect(cache.get("a")).toBe("alpha");
+    expect(cache.get("c")).toBe("charlie");
+  });
+
+  it("returns hit state for cached null values", () => {
+    const cache = new PluginLruCache<string | null>(2);
+
+    cache.set("missing", null);
+
+    expect(cache.getResult("missing")).toEqual({ hit: true, value: null });
+    expect(cache.getResult("unknown")).toEqual({ hit: false });
+  });
+
+  it("resizes and falls back to the default max entry count", () => {
+    const cache = new PluginLruCache<string>(2);
+
+    cache.setMaxEntriesForTest(1.9);
+    cache.set("a", "alpha");
+    cache.set("b", "bravo");
+    expect(cache.maxEntries).toBe(1);
+    expect(cache.size).toBe(1);
+    expect(cache.get("a")).toBeUndefined();
+
+    cache.setMaxEntriesForTest();
+    expect(cache.maxEntries).toBe(2);
+  });
+});
diff --git a/src/plugins/plugin-lru-cache.ts b/src/plugins/plugin-lru-cache.ts
new file mode 100644
index 00000000000..9037735cb34
--- /dev/null
+++ b/src/plugins/plugin-lru-cache.ts
@@ -0,0 +1,72 @@
+export type PluginLruCacheResult<T> = { hit: true; value: T } | { hit: false };
+
+export class PluginLruCache<T> {
+  readonly #defaultMaxEntries: number;
+  #maxEntries: number;
+  readonly #entries = new Map<string, T>();
+
+  constructor(defaultMaxEntries: number) {
+    this.#defaultMaxEntries = normalizeMaxEntries(defaultMaxEntries, 1);
+    this.#maxEntries = this.#defaultMaxEntries;
+  }
+
+  get maxEntries(): number {
+    return this.#maxEntries;
+  }
+
+  get size(): number {
+    return this.#entries.size;
+  }
+
+  setMaxEntriesForTest(value?: number): void {
+    this.#maxEntries =
+      typeof value === "number"
+        ? normalizeMaxEntries(value, this.#defaultMaxEntries)
+        : this.#defaultMaxEntries;
+    this.#evictOldestEntries();
+  }
+
+  clear(): void {
+    this.#entries.clear();
+  }
+
+  get(cacheKey: string): T | undefined {
+    const cached = this.getResult(cacheKey);
+    return cached.hit ? cached.value : undefined;
+  }
+
+  getResult(cacheKey: string): PluginLruCacheResult<T> {
+    if (!this.#entries.has(cacheKey)) {
+      return { hit: false };
+    }
+    const cached = this.#entries.get(cacheKey) as T;
+    this.#entries.delete(cacheKey);
+    this.#entries.set(cacheKey, cached);
+    return { hit: true, value: cached };
+  }
+
+  set(cacheKey: string, value: T): void {
+    if (this.#entries.has(cacheKey)) {
+      this.#entries.delete(cacheKey);
+    }
+    this.#entries.set(cacheKey, value);
+    this.#evictOldestEntries();
+  }
+
+  #evictOldestEntries(): void {
+    while (this.#entries.size > this.#maxEntries) {
+      const oldestEntry = this.#entries.keys().next();
+      if (oldestEntry.done) {
+        break;
+      }
+      this.#entries.delete(oldestEntry.value);
+    }
+  }
+}
+
+function normalizeMaxEntries(value: number, fallback: number): number {
+  if (!Number.isFinite(value) || value <= 0) {
+    return fallback;
+  }
+  return Math.max(1, Math.floor(value));
+}
diff --git a/src/plugins/setup-registry.ts b/src/plugins/setup-registry.ts
index ac9ed08ff32..9e4626a60c2 100644
--- a/src/plugins/setup-registry.ts
+++ b/src/plugins/setup-registry.ts
@@ -7,6 +7,7 @@ import { buildPluginApi } from "./api-builder.js";
 import { collectPluginConfigContractMatches } from "./config-contracts.js";
 import { getCachedPluginJitiLoader, type PluginJitiLoaderCache } from "./jiti-loader-cache.js";
 import type { PluginManifestRecord } from "./manifest-registry.js";
+import { PluginLruCache, type PluginLruCacheResult } from "./plugin-lru-cache.js";
 import { loadPluginManifestRegistryForPluginRegistry } from "./plugin-registry.js";
 import { resolvePluginCacheInputs } from "./roots.js";
 import type { PluginRuntime } from "./runtime/types.js";
@@ -86,20 +87,22 @@ const NOOP_LOGGER: PluginLogger = {
 const MAX_SETUP_LOOKUP_CACHE_ENTRIES = 128;
 
 const jitiLoaders: PluginJitiLoaderCache = new Map();
-const setupRegistryCache = new Map<string, PluginSetupRegistry>();
-const setupProviderCache = new Map<string, ProviderPlugin | null>();
-const setupCliBackendCache = new Map<string, SetupCliBackendEntry | null>();
-let setupLookupCacheEntryCap = MAX_SETUP_LOOKUP_CACHE_ENTRIES;
+const setupRegistryCache = new PluginLruCache<PluginSetupRegistry>(MAX_SETUP_LOOKUP_CACHE_ENTRIES);
+const setupProviderCache = new PluginLruCache<ProviderPlugin | null>(
+  MAX_SETUP_LOOKUP_CACHE_ENTRIES,
+);
+const setupCliBackendCache = new PluginLruCache<SetupCliBackendEntry | null>(
+  MAX_SETUP_LOOKUP_CACHE_ENTRIES,
+);
 
 export const __testing = {
   get maxSetupLookupCacheEntries() {
-    return setupLookupCacheEntryCap;
+    return setupRegistryCache.maxEntries;
   },
   setMaxSetupLookupCacheEntriesForTest(value?: number) {
-    setupLookupCacheEntryCap =
-      typeof value === "number" && Number.isFinite(value) && value > 0
-        ? Math.max(1, Math.floor(value))
-        : MAX_SETUP_LOOKUP_CACHE_ENTRIES;
+    setupRegistryCache.setMaxEntriesForTest(value);
+    setupProviderCache.setMaxEntriesForTest(value);
+    setupCliBackendCache.setMaxEntriesForTest(value);
   },
   getCacheSizes() {
     return {
@@ -125,31 +128,12 @@ function getJiti(modulePath: string) {
   });
 }
 
-function getCachedSetupValue<T>(
-  cache: Map<string, T>,
-  key: string,
-): { hit: true; value: T } | { hit: false } {
-  if (!cache.has(key)) {
-    return { hit: false };
-  }
-  const cached = cache.get(key) as T;
-  cache.delete(key);
-  cache.set(key, cached);
-  return { hit: true, value: cached };
+function getCachedSetupValue<T>(cache: PluginLruCache<T>, key: string): PluginLruCacheResult<T> {
+  return cache.getResult(key);
 }
 
-function setCachedSetupValue<T>(cache: Map<string, T>, key: string, value: T): void {
-  if (cache.has(key)) {
-    cache.delete(key);
-  }
+function setCachedSetupValue<T>(cache: PluginLruCache<T>, key: string, value: T): void {
   cache.set(key, value);
-  while (cache.size > setupLookupCacheEntryCap) {
-    const oldestKey = cache.keys().next().value;
-    if (typeof oldestKey !== "string") {
-      break;
-    }
-    cache.delete(oldestKey);
-  }
 }
 
 function buildSetupRegistryCacheKey(params: {