diff --git a/src/wasm/stream.ts b/src/wasm/stream.ts
index 694820c..3b35d13 100644
--- a/src/wasm/stream.ts
+++ b/src/wasm/stream.ts
@@ -5,6 +5,7 @@
  * Use `.pipeThrough()` instead of `.pipe()`.
  */
 
+import type { Transformer } from 'node:stream/web';
 import { createLZMAError } from '../errors.js';
 import type { LZMAOptions } from '../types.js';
 import { code, decoderInit, encoderInit, end, getModule } from './bindings.js';
@@ -65,9 +66,13 @@ export function createXz(opts?: LZMAOptions): TransformStream<Uint8Array, Uint8A
       }
     },
     /* cancel() frees WASM resources when the readable side is cancelled.
-       Part of the Streams spec but not yet in TypeScript's DOM lib. */
-    // @ts-expect-error cancel is a valid Transformer method per Streams spec
+       Part of the Streams spec; @types/node added `cancel?:` to the Transformer
+       interface in 25.7.0. The intersection cast accepts the property on both
+       older typings (where it's absent) and newer typings (where it's present),
+       keeping the typecheck stable across `@types/node` minor bumps. */
     cancel: doCleanup,
+  } as Transformer<Uint8Array, Uint8Array> & {
+    cancel?: (reason: unknown) => void | PromiseLike<void>;
   });
 }
 
@@ -125,9 +130,10 @@ export function createUnxz(): TransformStream<Uint8Array, Uint8Array> {
       }
     },
     /* cancel() frees WASM resources when the readable side is cancelled.
-       Part of the Streams spec but not yet in TypeScript's DOM lib. */
-    // @ts-expect-error cancel is a valid Transformer method per Streams spec
+       See createXz() for the rationale on the intersection cast. */
     cancel: doCleanup,
+  } as Transformer<Uint8Array, Uint8Array> & {
+    cancel?: (reason: unknown) => void | PromiseLike<void>;
   });
 }
 
diff --git a/test/wasm/stream-directive-hygiene.test.ts b/test/wasm/stream-directive-hygiene.test.ts
new file mode 100644
index 0000000..6ae761b
--- /dev/null
+++ b/test/wasm/stream-directive-hygiene.test.ts
@@ -0,0 +1,29 @@
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+import { describe, expect, it } from 'vitest';
+
+/**
+ * Forward-compat guard for `src/wasm/stream.ts`.
+ *
+ * `@types/node` adds and (more rarely) removes typed members of the Streams
+ * interfaces across minor bumps. The file deliberately uses an intersection
+ * cast on `TransformStream` constructor calls so it needs ZERO TypeScript
+ * suppression directives. Any directive — in either the expect-error or
+ * ignore form — would either mask a real upstream regression, or fire
+ * TS2578 ("unused directive") the moment the typing it suppresses lands
+ * upstream, breaking the daily Refresh Lockfile workflow.
+ *
+ * This test is the deterministic regression detector for that invariant.
+ */
+describe('src/wasm/stream.ts — TS directive hygiene', () => {
+  it('contains no @ts-ignore or @ts-expect-error directive', () => {
+    const path = fileURLToPath(new URL('../../src/wasm/stream.ts', import.meta.url));
+    const source = readFileSync(path, 'utf8');
+
+    // Match the directive form specifically (with leading `//` and a word boundary
+    // after the directive name), so the rule name appearing inside a doc-comment
+    // or string literal does not produce a false positive.
+    const directivePattern = /\/\/\s*@ts-(expect-error|ignore)\b/;
+    expect(source).not.toMatch(directivePattern);
+  });
+});