diff --git a/server/services/local-compiler.ts b/server/services/local-compiler.ts
index c6116102..3822baf7 100644
--- a/server/services/local-compiler.ts
+++ b/server/services/local-compiler.ts
@@ -338,6 +338,7 @@ export class LocalCompiler {
         const { randomUUID: _cacheUUID } = await import("node:crypto");
         const tmpCachePath = cachePath + "." + _cacheUUID() + ".tmp";
         try {
+          await mkdir(dirname(cachePath), { recursive: true });
           const fs = await import("node:fs");
           await fs.promises.copyFile(suspect, tmpCachePath);
           await fs.promises.rename(tmpCachePath, cachePath);
@@ -345,7 +346,6 @@ export class LocalCompiler {
           const sizeKB = (newCacheStat.size / 1024).toFixed(1);
           this.logger.info(`[LocalCompiler] CLI cache saved (${sizeKB} KB)`);
         } catch (error_) {
-          const tmpCachePath = cachePath + "." + _cacheUUID() + ".tmp";
           try { await rm(tmpCachePath, { force: true }); } catch {}
           this.logger.warn(`[LocalCompiler] CLI cache write failed: ${
             error_ instanceof Error ? error_.message : error_}`);
diff --git a/tests/server/services/local-compiler.test.ts b/tests/server/services/local-compiler.test.ts
index ba1e6f33..fa5a05ba 100644
--- a/tests/server/services/local-compiler.test.ts
+++ b/tests/server/services/local-compiler.test.ts
@@ -1,17 +1,24 @@
-import { mkdir, mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
+import { mkdir, mkdtemp, readFile, readdir, rm, stat, utimes, writeFile } from "node:fs/promises";
 import { tmpdir } from "node:os";
-import { join } from "node:path";
+import { dirname, join } from "node:path";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import { ProcessExecutor } from "../../../server/services/process-executor";
 import { LocalCompiler } from "../../../server/services/local-compiler";
 import { SketchFileBuilder } from "../../../server/services/sketch-file-builder";
 import { spawn } from "node:child_process";
+import { Logger } from "../../../shared/logger";
+
+interface LocalCompilerCacheInternals {
+  updateCliCache(buildDir: string): Promise<void>;
+}
 
 describe("LocalCompiler public compile behavior", () => {
   const temporaryDirectories: string[] = [];
+  const originalCliCachePath = Reflect.get(LocalCompiler, "CLI_CACHE_PATH");
 
   afterEach(async () => {
     vi.restoreAllMocks();
+    Reflect.set(LocalCompiler, "CLI_CACHE_PATH", originalCliCachePath);
     await Promise.all(temporaryDirectories.map((directory) => rm(directory, { recursive: true, force: true })));
     temporaryDirectories.length = 0;
   });
@@ -213,4 +220,41 @@ describe("LocalCompiler public compile behavior", () => {
     expect(execute).toHaveBeenCalledTimes(1);
     expect(execute.mock.calls[0][0]).toBe("arduino-cli");
   });
+
+  it("initializes the CLI cache when its parent directory does not yet exist", async () => {
+    const root = await mkdtemp(join(tmpdir(), "unosim-cli-cache-"));
+    temporaryDirectories.push(root);
+    const buildDir = join(root, "build");
+    const sourceArchive = join(buildDir, "core", "core.a");
+    const cachePath = join(root, "cache", "cores", "uno-cli-feedback.a");
+    await mkdir(dirname(sourceArchive), { recursive: true });
+    await writeFile(sourceArchive, "core archive", "utf8");
+    Reflect.set(LocalCompiler, "CLI_CACHE_PATH", cachePath);
+    const warn = vi.spyOn(Logger.prototype, "warn");
+
+    await (new LocalCompiler() as unknown as LocalCompilerCacheInternals).updateCliCache(buildDir);
+
+    expect((await stat(dirname(cachePath))).isDirectory()).toBe(true);
+    const cacheContents = await readFile(cachePath);
+    expect(cacheContents.byteLength).toBeGreaterThan(0);
+    expect(warn).not.toHaveBeenCalled();
+  });
+
+  it("cleans the exact temporary cache file when the final rename fails", async () => {
+    const root = await mkdtemp(join(tmpdir(), "unosim-cli-cache-cleanup-"));
+    temporaryDirectories.push(root);
+    const buildDir = join(root, "build");
+    const sourceArchive = join(buildDir, "core", "core.a");
+    const cachePath = join(root, "cache", "uno-cli-feedback.a");
+    await mkdir(dirname(sourceArchive), { recursive: true });
+    await writeFile(sourceArchive, "core archive", "utf8");
+    await mkdir(cachePath, { recursive: true });
+    await utimes(cachePath, new Date(0), new Date(0));
+    Reflect.set(LocalCompiler, "CLI_CACHE_PATH", cachePath);
+
+    await (new LocalCompiler() as unknown as LocalCompilerCacheInternals).updateCliCache(buildDir);
+
+    const cacheEntries = await readdir(dirname(cachePath));
+    expect(cacheEntries.filter((entry) => entry.endsWith(".tmp"))).toEqual([]);
+  });
 });