diff --git a/packages/quantus-crypto/README.md b/packages/quantus-crypto/README.md
index d92c2976..4ef8d18a 100644
--- a/packages/quantus-crypto/README.md
+++ b/packages/quantus-crypto/README.md
@@ -28,6 +28,14 @@ wasm-bindgen 0.2.79's JS-heap ABI, while this crate builds with 0.2.128, which
 uses externref tables. wasm-bindgen's own generated glue plus `initSync` is both
 smaller and correct.
 
+The only runtime dependency is `fflate`, for zlib inflate. Base64 decoding is
+fifteen lines here rather than a dependency. Both were originally taken from
+`@polkadot/wasm-util`, which turned out to cost more than it saved: its index
+re-exports `packageDetect`, dragging in a `@polkadot/util` peer dependency for a
+side effect we do not want, and being a workspace package it resolved through its
+*own* repo's node_modules when this package was consumed by symlink from another
+checkout — which is exactly how `quantus/common` consumes it during development.
+
 ## Scheme selector
 
 `Scheme.MlDsa87 = 0`, `Scheme.MlDsa65 = 1` — these are the chain's own
diff --git a/packages/quantus-crypto/package.json b/packages/quantus-crypto/package.json
index 4e7ed98c..6b147191 100644
--- a/packages/quantus-crypto/package.json
+++ b/packages/quantus-crypto/package.json
@@ -18,7 +18,7 @@
   "version": "0.1.0",
   "main": "index.js",
   "dependencies": {
-    "@polkadot/wasm-util": "7.5.4",
+    "fflate": "^0.8.2",
     "tslib": "^2.7.0"
   }
 }
diff --git a/packages/quantus-crypto/src/base64.ts b/packages/quantus-crypto/src/base64.ts
new file mode 100644
index 00000000..986f48a5
--- /dev/null
+++ b/packages/quantus-crypto/src/base64.ts
@@ -0,0 +1,51 @@
+// Copyright 2026 @quantus/crypto authors & contributors
+// SPDX-License-Identifier: Apache-2.0
+
+const CHARS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
+
+// An array indexer rather than a Map: the input is ASCII by construction, so it
+// cannot overflow, and array access is measurably faster on the hot loop.
+const MAP = new Array<number>(256);
+
+for (let i = 0; i < CHARS.length; i++) {
+  MAP[CHARS.charCodeAt(i)] = i;
+}
+
+/**
+ * Decode base64 into a caller-supplied buffer.
+ *
+ * Deliberately not `atob` or `Buffer.from`: the first is browser-only, the second
+ * node-only, and this runs in an MV3 service worker, a Worker, node tests and a
+ * bundled extension page. The output length is known at build time, so the
+ * caller provides the buffer and there is no growth or reallocation.
+ *
+ * This is a reimplementation of `@polkadot/wasm-util`'s base64Decode, which was
+ * the dependency it replaced. That package's index re-exports `packageDetect`,
+ * dragging in a `@polkadot/util` peer dependency for a side effect we do not
+ * want, and being a workspace package it resolved through its own repo's
+ * node_modules when consumed by symlink from another checkout. Fifteen lines is
+ * cheaper than either problem.
+ */
+export function base64Decode (data: string, out: Uint8Array): Uint8Array {
+  let byte = 0;
+  let bits = 0;
+  let pos = 0;
+
+  for (let i = 0; i < data.length && pos < out.length; i++) {
+    const value = MAP[data.charCodeAt(i)];
+
+    if (value === undefined) {
+      continue;
+    }
+
+    byte = (byte << 6) | value;
+    bits += 6;
+
+    if (bits >= 8) {
+      bits -= 8;
+      out[pos++] = (byte >>> bits) & 0xff;
+    }
+  }
+
+  return out;
+}
diff --git a/packages/quantus-crypto/src/init.ts b/packages/quantus-crypto/src/init.ts
index eba41cc4..cadb1a18 100644
--- a/packages/quantus-crypto/src/init.ts
+++ b/packages/quantus-crypto/src/init.ts
@@ -1,12 +1,9 @@
 // Copyright 2026 @quantus/crypto authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
-// Deep imports, not the package index. `@polkadot/wasm-util`'s index re-exports
-// `packageDetect`, whose only job is a side effect registering the package with
-// `@polkadot/util` — a peer dependency we would otherwise inherit for nothing.
-// These two subpaths are pure functions with no dependencies at all.
-import { base64Decode } from '@polkadot/wasm-util/base64';
-import { unzlibSync } from '@polkadot/wasm-util/fflate';
+import { unzlibSync } from 'fflate';
+
+import { base64Decode } from './base64.js';
 
 import { bytes, lenOut } from './bytes.js';
 import { initSync } from './generated/quantus_crypto.js';
diff --git a/packages/quantus-crypto/tsconfig.build.json b/packages/quantus-crypto/tsconfig.build.json
index 23481326..44c4904c 100644
--- a/packages/quantus-crypto/tsconfig.build.json
+++ b/packages/quantus-crypto/tsconfig.build.json
@@ -6,14 +6,6 @@
     "declaration": true,
     "outDir": "./build",
     "rootDir": "./src",
-    "paths": {
-      "@polkadot/wasm-util/base64": [
-        "wasm-util/build/base64.d.ts"
-      ],
-      "@polkadot/wasm-util/fflate": [
-        "wasm-util/build/fflate.d.ts"
-      ]
-    },
     "emitDeclarationOnly": false
   },
   "exclude": [
diff --git a/scripts/test-quantus-js.sh b/scripts/test-quantus-js.sh
index d2036026..7b4ce90d 100755
--- a/scripts/test-quantus-js.sh
+++ b/scripts/test-quantus-js.sh
@@ -4,13 +4,12 @@
 
 # Runs the consumer test against a staged node_modules rather than in-place.
 #
-# In this repo `node_modules/@polkadot/wasm-util` symlinks to the package *source*
-# directory, whose package.json carries no `exports` map — only the build output
-# does. So a deep import like `@polkadot/wasm-util/base64` resolves for a real
-# consumer and fails here, which would make the in-place test wrong in a way that
-# has nothing to do with our package. Staging the built artifacts the way an
-# install lays them out tests module resolution too, which is half of what can
-# break in a published package.
+# Staging the built artifact the way an install lays it out tests module
+# resolution too, which is half of what can break in a published package — it is
+# what caught binaryen 105 producing a wasm that fails to instantiate.
+#
+# `fflate`, the one runtime dependency, resolves by node walking up to the repo's
+# own node_modules, which is exactly what it would do inside a real install.
 
 set -e
 
@@ -18,10 +17,9 @@ PKG=packages/quantus-crypto
 STAGE=$PKG/build-test
 
 rm -rf $STAGE
-mkdir -p $STAGE/node_modules/@quantus $STAGE/node_modules/@polkadot
+mkdir -p $STAGE/node_modules/@quantus
 
 cp -r $PKG/build $STAGE/node_modules/@quantus/crypto
-cp -r packages/wasm-util/build $STAGE/node_modules/@polkadot/wasm-util
 echo '{ "name": "quantus-crypto-consumer-test", "type": "module", "version": "0.0.0" }' > $STAGE/package.json
 cp $PKG/test/consumer.mjs $STAGE/consumer.mjs
 
diff --git a/yarn.lock b/yarn.lock
index b8539e99..38a0473b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -614,7 +614,7 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@quantus/crypto@workspace:packages/quantus-crypto"
   dependencies:
-    "@polkadot/wasm-util": "npm:7.5.4"
+    fflate: "npm:^0.8.2"
     tslib: "npm:^2.7.0"
   languageName: unknown
   linkType: soft