diff --git a/packages/shared/src/relayClient.test.ts b/packages/shared/src/relayClient.test.ts
index 291cd347039b287f8f40e8ffff122a575fa93672..23ae8eb2d33d47425520fbf5ac7d82df66fd5a9e 100644
--- a/packages/shared/src/relayClient.test.ts
+++ b/packages/shared/src/relayClient.test.ts
@@ -4,6 +4,7 @@ import { describe, expect, it } from "@effect/vitest";
 import * as ConfigProvider from "effect/ConfigProvider";
 import * as Deferred from "effect/Deferred";
 import * as Effect from "effect/Effect";
+import * as Fiber from "effect/Fiber";
 import * as Hex from "effect/encoding/Hex";
 import * as Fiber from "effect/Fiber";
 import * as FileSystem from "effect/FileSystem";
@@ -154,6 +155,133 @@ const managedDirectory = (baseDir: string, platform: NodeJS.Platform) =>
   `${baseDir}/tools/cloudflared/${RelayClient.CLOUDFLARED_VERSION}/${platform}-x64`;
 
 describe("RelayClient", () => {
+  it.effect("cancels a contended install without removing the other installer's lock", () =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const baseDir = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-cloudflared-test-" });
+      const directory = `${baseDir}/tools/cloudflared/${RelayClient.CLOUDFLARED_VERSION}/linux-x64`;
+      const lockPath = `${directory}/cloudflared.lock`;
+      yield* fileSystem.makeDirectory(directory, { recursive: true });
+      yield* fileSystem.writeFileString(lockPath, "other-installer");
+      const contended = yield* Deferred.make<void>();
+      const manager = yield* RelayClient.makeCloudflaredRelayClient({ baseDir }).pipe(
+        Effect.provideService(FileSystem.FileSystem, {
+          ...fileSystem,
+          writeFileString: (path, contents, options) =>
+            fileSystem
+              .writeFileString(path, contents, options)
+              .pipe(
+                Effect.tapError(() =>
+                  path === lockPath ? Deferred.succeed(contended, undefined) : Effect.void,
+                ),
+              ),
+        }),
+      );
+      const installing = yield* manager.install.pipe(Effect.forkChild);
+      yield* Deferred.await(contended);
+      yield* Fiber.interrupt(installing);
+      expect(yield* fileSystem.readFileString(lockPath)).toBe("other-installer");
+    }).pipe(
+      Effect.scoped,
+      Effect.provide(
+        Layer.mergeAll(
+          NodeServices.layer,
+          layerHttpClient(new Uint8Array()),
+          layerSpawner([]),
+          layerHostRuntime({ PATH: "" }),
+        ),
+      ),
+    ),
+  );
+
+  it.effect("releases the install lock when a download is cancelled", () =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const baseDir = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-cloudflared-test-" });
+      const lockPath = `${baseDir}/tools/cloudflared/${RelayClient.CLOUDFLARED_VERSION}/linux-x64/cloudflared.lock`;
+      const downloading = yield* Deferred.make<void>();
+      const manager = yield* RelayClient.makeCloudflaredRelayClient({ baseDir });
+      const installing = yield* manager
+        .installWithProgress((event) =>
+          event.type === "progress" && event.stage === "downloading"
+            ? Deferred.succeed(downloading, undefined).pipe(Effect.andThen(Effect.never))
+            : Effect.void,
+        )
+        .pipe(Effect.forkChild);
+      yield* Deferred.await(downloading);
+      expect(yield* fileSystem.exists(lockPath)).toBe(true);
+      yield* Fiber.interrupt(installing);
+      expect(yield* fileSystem.exists(lockPath)).toBe(false);
+    }).pipe(
+      Effect.scoped,
+      Effect.provide(
+        Layer.mergeAll(
+          NodeServices.layer,
+          layerHttpClient(new Uint8Array()),
+          layerSpawner([]),
+          layerHostRuntime({ PATH: "" }),
+        ),
+      ),
+    ),
+  );
+
+  it.effect.skipIf(windowsHost)("releases a lock acquired while installation is cancelled", () =>
+    Effect.gen(function* () {
+      const fileSystem = yield* FileSystem.FileSystem;
+      const baseDir = yield* fileSystem.makeTempDirectoryScoped({ prefix: "t3-cloudflared-test-" });
+      const lockPath = `${baseDir}/tools/cloudflared/${RelayClient.CLOUDFLARED_VERSION}/linux-x64/cloudflared.lock`;
+      const acquired = yield* Deferred.make<void>();
+      const completeWrite = yield* Deferred.make<void>();
+      let pauseWrite = true;
+      const manager = yield* RelayClient.makeCloudflaredRelayClient({
+        baseDir,
+        releaseAsset: {
+          url: "https://example.test/cloudflared",
+          sha256: Hex.encode(sha256(new TextEncoder().encode("test-binary"))),
+          archive: "binary",
+        },
+      }).pipe(
+        Effect.provideService(FileSystem.FileSystem, {
+          ...fileSystem,
+          writeFileString: (path, contents, options) =>
+            fileSystem
+              .writeFileString(path, contents, options)
+              .pipe(
+                Effect.tap(() =>
+                  path === lockPath && pauseWrite
+                    ? Deferred.succeed(acquired, undefined).pipe(
+                        Effect.andThen(Deferred.await(completeWrite)),
+                      )
+                    : Effect.void,
+                ),
+              ),
+        }),
+      );
+
+      const installing = yield* manager.install.pipe(Effect.forkChild);
+      yield* Deferred.await(acquired);
+      const cancelling = yield* Fiber.interrupt(installing).pipe(
+        Effect.forkChild({ startImmediately: true }),
+      );
+      yield* Deferred.succeed(completeWrite, undefined);
+      yield* Fiber.join(cancelling);
+      expect(yield* fileSystem.exists(lockPath)).toBe(false);
+
+      pauseWrite = false;
+      expect(yield* manager.install).toMatchObject({ status: "available" });
+      expect(yield* fileSystem.exists(lockPath)).toBe(false);
+    }).pipe(
+      Effect.scoped,
+      Effect.provide(
+        Layer.mergeAll(
+          NodeServices.layer,
+          layerHttpClient(new TextEncoder().encode("test-binary")),
+          layerSpawner([]),
+          layerHostRuntime({ PATH: "" }),
+        ),
+      ),
+    ),
+  );
   it.effect.skipIf(windowsHost)(
     "resolves explicit overrides before managed and PATH executables",
     () =>
@@ -274,6 +402,11 @@ describe("RelayClient", () => {
       const error = yield* manager.install.pipe(Effect.flip);
       expect(error).toBeInstanceOf(RelayClient.RelayClientInstallError);
       expect(error.reason).toBe("invalid_checksum");
+      expect(
+        yield* fileSystem.exists(
+          `${baseDir}/tools/cloudflared/${RelayClient.CLOUDFLARED_VERSION}/linux-x64/cloudflared.lock`,
+        ),
+      ).toBe(false);
     }).pipe(
       Effect.scoped,
       Effect.provide(
diff --git a/packages/shared/src/relayClient.ts b/packages/shared/src/relayClient.ts
index e75133256ef569a4600069bf5f534728b07159fa..9e2f4bea8229417bbfad4917cc3a1b7accbf09e4 100644
--- a/packages/shared/src/relayClient.ts
+++ b/packages/shared/src/relayClient.ts
@@ -487,7 +487,10 @@ export const makeCloudflaredRelayClient = Effect.fn("cloudflared.make")(function
     lockPath: string,
   ) {
     for (let attempt = 0; attempt < INSTALL_LOCK_RETRY_COUNT; attempt += 1) {
-      const acquired = yield* fileSystem.writeFileString(lockPath, "", { flag: "wx" }).pipe(
+      const acquired = yield* Effect.acquireRelease(
+        fileSystem.writeFileString(lockPath, "", { flag: "wx" }),
+        () => fileSystem.remove(lockPath, { force: true }).pipe(Effect.ignore),
+      ).pipe(
         Effect.as(true),
         Effect.catchIf(isAlreadyExists, () => Effect.succeed(false)),
       );
@@ -610,7 +613,6 @@ export const makeCloudflaredRelayClient = Effect.fn("cloudflared.make")(function
       } satisfies AvailableRelayClient;
     }).pipe(
       Effect.scoped,
-      Effect.ensuring(fileSystem.remove(lockPath, { force: true }).pipe(Effect.ignore)),
       Effect.catchIf(
         (cause) => !(cause instanceof RelayClientInstallError),
         (cause) =>
@@ -631,7 +633,7 @@ export const makeCloudflaredRelayClient = Effect.fn("cloudflared.make")(function
           type: "progress",
           stage,
         }),
-      ),
+      ).pipe(Effect.scoped),
     );
   const install = installWithProgress(() => Effect.void);