diff --git a/.github/workflows/desktop-release.yml b/.github/workflows/desktop-release.yml
index 26be12291b..bdbeb9f139 100644
--- a/.github/workflows/desktop-release.yml
+++ b/.github/workflows/desktop-release.yml
@@ -135,6 +135,32 @@ jobs:
         env:
           NODE_AUTH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
+      # Backport electron-builder#10172 to the pinned build tool only.
+      # Remove this step when app-builder-lib is upgraded to a release containing it.
+      - name: Repair temporary keychain password in signing tool
+        shell: bash
+        run: |
+          node <<'KEYCHAIN_FIX'
+          const fs = require('node:fs');
+          const path = require('node:path');
+          const manifestPath = require.resolve('app-builder-lib/package.json');
+          if (JSON.parse(fs.readFileSync(manifestPath, 'utf8')).version !== '26.8.1') {
+            throw new Error('Reassess/remove the signing backport for the new app-builder-lib version');
+          }
+          const sourcePath = path.join(path.dirname(manifestPath), 'out/codeSign/macCodeSign.js');
+          let source = fs.readFileSync(sourcePath, 'utf8');
+          const replacements = [
+            ['importCerts(keychainFile, certPaths, cscPasswords)', 'importCerts(keychainFile, certPaths, cscPasswords, keychainPassword)'],
+            ['importCerts(keychainFile, paths, keyPasswords)', 'importCerts(keychainFile, paths, keyPasswords, keychainPassword)'],
+            ['["set-key-partition-list", "-S", "apple-tool:,apple:", "-s", "-k", password, keychainFile]', '["set-key-partition-list", "-S", "apple-tool:,apple:", "-s", "-k", keychainPassword, keychainFile]'],
+          ];
+          for (const [before, after] of replacements) {
+            if (source.split(before).length !== 2) throw new Error('Unexpected signing tool source; refusing to patch');
+            source = source.replace(before, after);
+          }
+          fs.writeFileSync(sourcePath, source);
+          KEYCHAIN_FIX
+
       - name: Set desktop package version from tag
         shell: bash
         run: |
diff --git a/scripts/ci-workflow.test.mjs b/scripts/ci-workflow.test.mjs
index 73a9003312..381f826540 100644
--- a/scripts/ci-workflow.test.mjs
+++ b/scripts/ci-workflow.test.mjs
@@ -1,5 +1,5 @@
 import assert from "node:assert/strict";
-import { readFileSync, readdirSync, mkdtempSync, writeFileSync, rmSync } from "node:fs";
+import { readFileSync, readdirSync, mkdtempSync, mkdirSync, writeFileSync, rmSync } from "node:fs";
 import { spawnSync } from "node:child_process";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
@@ -679,3 +679,53 @@ test("macOS jobs use latest runners while preserving release architectures", ()
   // GitHub has no standard macos-latest-intel alias; use the newest Intel image.
   assert.match(release, /runner: macos-26-intel\n\s+electron_arch: x64/);
 });
+
+test("macOS signing repair keeps certificate and keychain passwords separate", () => {
+  const workflow = readFileSync(new URL(".github/workflows/desktop-release.yml", repoRoot), "utf8");
+  const match = workflow.match(/<<'KEYCHAIN_FIX'\n([\s\S]*?)\n          KEYCHAIN_FIX/);
+  assert.ok(match, "the release workflow repairs the pinned signing tool");
+  const script = match[1].replace(/^          /gm, "");
+  const original = [
+    "return await importCerts(keychainFile, certPaths, cscPasswords);",
+    "async function importCerts(keychainFile, paths, keyPasswords) {",
+    '["import", paths[i], "-P", password]',
+    '["set-key-partition-list", "-S", "apple-tool:,apple:", "-s", "-k", password, keychainFile]',
+    "}",
+  ].join("\n");
+  const directory = mkdtempSync(join(tmpdir(), "signing-repair-"));
+  try {
+    const packageDirectory = join(directory, "node_modules/app-builder-lib");
+    mkdirSync(join(packageDirectory, "out/codeSign"), { recursive: true });
+    const manifest = join(packageDirectory, "package.json");
+    const sourcePath = join(packageDirectory, "out/codeSign/macCodeSign.js");
+    for (const [version, source, succeeds] of [
+      ["26.8.1", original, true],
+      ["26.8.1", original.replace("cscPasswords);", "differentArguments);"), false],
+      ["26.18.0", original, false],
+    ]) {
+      writeFileSync(manifest, JSON.stringify({ name: "app-builder-lib", version }));
+      writeFileSync(sourcePath, source);
+      const result = spawnSync(process.execPath, ["-e", script], {
+        cwd: directory,
+        encoding: "utf8",
+      });
+      const actual = readFileSync(sourcePath, "utf8");
+      if (succeeds) {
+        assert.equal(result.status, 0, result.stderr);
+        assert.ok(
+          actual.includes("importCerts(keychainFile, certPaths, cscPasswords, keychainPassword)"),
+        );
+        assert.ok(
+          actual.includes("importCerts(keychainFile, paths, keyPasswords, keychainPassword)"),
+        );
+        assert.ok(actual.includes('["import", paths[i], "-P", password]'));
+        assert.ok(actual.includes('"-k", keychainPassword, keychainFile]'));
+      } else {
+        assert.notEqual(result.status, 0);
+        assert.equal(actual, source, "unexpected tool inputs must fail without a partial write");
+      }
+    }
+  } finally {
+    rmSync(directory, { recursive: true, force: true });
+  }
+});