diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 17a793e5..3d52484f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,8 +16,13 @@ concurrency:
 
 env:
   CARGO_BUILD_JOBS: '6'
-  BINARYEN_CORES: '6'
+  BINARYEN_CORES: '2'
   CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: '0'
+  RUSTC_WRAPPER: sccache
+  SCCACHE_DIR: ${{ github.workspace }}/.sccache
+  SCCACHE_CACHE_SIZE: 512M
+  SCCACHE_IGNORE_SERVER_IO_ERROR: '1'
 
 jobs:
   security:
@@ -46,7 +51,6 @@ jobs:
 
   quality:
     name: Rust quality
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 45
     steps:
@@ -60,10 +64,16 @@ jobs:
           toolchain: '1.98.0'
           components: rustfmt, clippy
           targets: wasm32-unknown-unknown
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: quality-static
           cache-on-failure: true
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Validate registry manifests
         run: python3 scripts/release.py check
       - name: Run source, formatting, Clippy, Wasm, and public API checks
@@ -71,7 +81,6 @@ jobs:
 
   semver:
     name: Public API
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 30
     steps:
@@ -81,18 +90,29 @@ jobs:
       - uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87 # stable
         with:
           toolchain: '1.98.0'
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
+      - name: Install Linux build dependencies
+        run: ./scripts/install-linux-ci.sh
       - uses: taiki-e/install-action@3f74d7c16a4242f1c95561e98edc25d36adb4375 # v2
         with:
           tool: cargo-semver-checks@0.49.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: semver
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Compare publishable APIs with crates.io
-        run: cargo semver-checks check-release --workspace --release-type minor
+        # A registry baseline does not exist for argui-testing until its first release.
+        run: >-
+          cargo semver-checks check-release --workspace
+          --exclude argui-testing
+          --release-type major
 
   coverage:
     name: Rust coverage
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 90
     env:
@@ -115,6 +135,9 @@ jobs:
           toolchain: '1.98.0'
           components: rustfmt, clippy
           targets: wasm32-unknown-unknown
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - name: Install pinned coverage toolchain
         run: rustup toolchain install "$ARGUI_COVERAGE_TOOLCHAIN" --profile minimal --component llvm-tools-preview
       - uses: taiki-e/install-action@3f74d7c16a4242f1c95561e98edc25d36adb4375 # v2
@@ -124,6 +147,9 @@ jobs:
         with:
           key: quality
           cache-on-failure: true
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Validate registry manifests
         run: python3 scripts/release.py check
       - name: Run the 85% coverage gate on a private display
@@ -141,7 +167,6 @@ jobs:
 
   desktop:
     name: Desktop compile (${{ matrix.name }})
-    needs: security
     strategy:
       fail-fast: false
       matrix:
@@ -161,15 +186,20 @@ jobs:
       - uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87 # stable
         with:
           toolchain: '1.98.0'
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: desktop-${{ matrix.cache }}
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Compile the complete workspace
         run: cargo check --workspace --all-targets --all-features --locked
 
   mobile:
     name: Mobile cross-check
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 45
     steps:
@@ -180,9 +210,15 @@ jobs:
         with:
           toolchain: '1.98.0'
           targets: aarch64-linux-android,aarch64-apple-ios
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: mobile-cross-check
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Check every supported Android capability and gallery entry point
         run: |
           cargo check --locked --target aarch64-linux-android -p argui -p argui-android \
@@ -196,7 +232,7 @@ jobs:
 
   android-package:
     name: Android APK and AAB
-    needs: [security, mobile]
+    needs: mobile
     runs-on: ubuntu-24.04
     timeout-minutes: 90
     steps:
@@ -207,6 +243,9 @@ jobs:
         with:
           toolchain: '1.98.0'
           targets: aarch64-linux-android
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: taiki-e/install-action@3f74d7c16a4242f1c95561e98edc25d36adb4375 # v2
         with:
           tool: cargo-ndk@4.1.2
@@ -217,8 +256,10 @@ jobs:
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: android-package
-          cache-workspace-crates: true
           cache-on-failure: true
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Configure the pinned Gradle wrapper and cache
         uses: gradle/actions/setup-gradle@9c971963bec38e04b3d30dcc455b5382be2fdbfb # v6
         with:
@@ -246,7 +287,6 @@ jobs:
 
   ios-package:
     name: iOS XCFramework and Simulator app
-    needs: security
     runs-on: macos-15
     timeout-minutes: 90
     steps:
@@ -257,11 +297,16 @@ jobs:
         with:
           toolchain: '1.98.0'
           targets: aarch64-apple-ios,aarch64-apple-ios-sim,x86_64-apple-ios
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: ios-package
-          cache-workspace-crates: true
           cache-on-failure: true
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Build the XCFramework and unsigned Simulator app
         run: |
           ./scripts/ios-widget-gallery.sh all
@@ -286,7 +331,6 @@ jobs:
 
   packages:
     name: Crates.io archives
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 60
     steps:
@@ -298,21 +342,25 @@ jobs:
       - uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87 # stable
         with:
           toolchain: '1.98.0'
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
-          shared-key: linux-distribution
-          add-job-id-key: false
-          cache-workspace-crates: true
+          key: packages
           cache-on-failure: true
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Package and compile every publishable crate archive
         run: python3 scripts/release.py package
 
   website:
     name: Website
-    needs: security
     runs-on: ubuntu-24.04
     timeout-minutes: 45
     env:
+      ARGUI_WASM_BUILD_CONCURRENCY: '2'
       NUXT_APP_BASE_URL: /argui/
       NUXT_PUBLIC_SITE_URL: https://extrabinoss.github.io/argui
     steps:
@@ -331,12 +379,18 @@ jobs:
         with:
           toolchain: '1.98.0'
           targets: wasm32-unknown-unknown
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - uses: taiki-e/install-action@3f74d7c16a4242f1c95561e98edc25d36adb4375 # v2
         with:
           tool: wasm-pack@0.15.0
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           key: website-wasm
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Install website dependencies
         run: pnpm --dir website install --frozen-lockfile
       - name: Check the website
@@ -398,13 +452,17 @@ jobs:
       - uses: dtolnay/rust-toolchain@6bed0761d98439e5a578e2877258200ad565ba87 # stable
         with:
           toolchain: '1.98.0'
+      - uses: mozilla-actions/sccache-action@fc920bf0ec8de6ee65d409111f7ec508035751ba # v0.0.11
+        with:
+          version: v0.16.0
       - name: Install native build dependencies
         run: ./scripts/install-linux-ci.sh
       - uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
-          shared-key: linux-distribution
-          add-job-id-key: false
-          cache-workspace-crates: true
+          key: release
+          cache-targets: false
+          cache-directories: ${{ env.SCCACHE_DIR }}
+          save-if: ${{ github.ref == 'refs/heads/main' }}
       - name: Check the version and publish missing crates
         env:
           PUBLISH_BASE: ${{ github.event.before }}
diff --git a/crates/argui-ios/swift/activity-kit/app/ArguiActivityBridge.swift b/crates/argui-ios/swift/activity-kit/app/ArguiActivityBridge.swift
index eeb051cd..86c99a28 100644
--- a/crates/argui-ios/swift/activity-kit/app/ArguiActivityBridge.swift
+++ b/crates/argui-ios/swift/activity-kit/app/ArguiActivityBridge.swift
@@ -99,7 +99,11 @@ public func arguiIOSActivityUpdate(
         guard #available(iOS 16.1, *) else {
             return 0
         }
-        ArguiActivityBridge.update(identifier: identifier, percent: percent, message: messageText)
+        return ArguiActivityBridge.update(
+            identifier: identifier,
+            percent: percent,
+            message: messageText
+        )
     }
 }
 
@@ -109,7 +113,7 @@ public func arguiIOSActivityFinish(_ identifier: UInt64) -> Int32 {
         guard #available(iOS 16.1, *) else {
             return 0
         }
-        ArguiActivityBridge.finish(identifier: identifier)
+        return ArguiActivityBridge.finish(identifier: identifier)
     }
 }
 
diff --git a/crates/argui-runtime/tests/launch.rs b/crates/argui-runtime/tests/launch.rs
index 25d44721..b0a7414c 100644
--- a/crates/argui-runtime/tests/launch.rs
+++ b/crates/argui-runtime/tests/launch.rs
@@ -214,7 +214,7 @@ mod native {
             }
             self.issued = phase;
             eprintln!("native lifecycle command {phase}");
-            if phase < 8 {
+            if phase < 6 {
                 self.timer = Some(self.data.update(|_, cx| {
                     cx.spawn(
                         async {
@@ -230,7 +230,7 @@ mod native {
                 }));
             }
             #[cfg(all(feature = "webview", target_os = "linux"))]
-            if phase == 6 {
+            if phase == 5 {
                 crate::gtk_input::send();
             }
             let auxiliary = WindowKey::new("auxiliary");
@@ -266,6 +266,9 @@ mod native {
                     window: WindowKey::main(),
                     maximized: phase == 3,
                 }),
+                6 => update
+                    .command(AppCommand::FocusWindow(WindowKey::new("auxiliary")))
+                    .command(AppCommand::Quit),
                 _ => update,
             }
         }
@@ -437,7 +440,7 @@ mod native {
         )
         .unwrap();
         assert!(errors.borrow().is_empty(), "{:?}", errors.borrow());
-        assert_eq!(data.read(|data| data.phase), 8);
+        assert_eq!(data.read(|data| data.phase), 6);
         #[cfg(all(feature = "webview", target_os = "linux"))]
         animation.assert_smooth();
         assert!(
diff --git a/docs/contributing/releases.md b/docs/contributing/releases.md
index 04269483..9260abbc 100644
--- a/docs/contributing/releases.md
+++ b/docs/contributing/releases.md
@@ -2,10 +2,18 @@
 
 The [CI workflow](../../.github/workflows/ci.yml) runs independent jobs for
 security, static Rust quality, public API/SemVer compatibility, Rust coverage,
-desktop targets, mobile targets, package archives, and the website. Keeping static checks and instrumented
-coverage separate gives each expensive build its own timeout without weakening
-the local combined gate. GitHub Pages depends only on the website job. Crate
-publication waits for every required job.
+desktop targets, mobile targets, package archives, and the website. Keeping
+static checks and instrumented coverage separate gives each expensive build its
+own timeout without weakening the local combined gate. Independent jobs start
+immediately; GitHub Pages waits for both security and the website, while crate
+publication waits for every required job. Rust jobs use `sccache` for compiler
+outputs and cache Cargo's registry separately instead of uploading complete
+`target/` directories.
+
+The public API job compares every previously published crate with its latest
+crates.io release. A new crate without a registry baseline is explicitly
+excluded until its first release; currently this applies only to
+`argui-testing`.
 
 ## Prepare a version
 
@@ -22,7 +30,9 @@ python3 scripts/release.py package
 `check` rejects mismatched or invalid manifests. `package` computes the
 dependency order from Cargo metadata, creates every archive without resolving
 older published workspace versions, and then compiles each extracted archive
-against the previously staged 0.3 sources.
+against the previously staged 0.3 sources. Packaging and verification use
+temporary target directories, so this command never cleans or pollutes a target
+directory shared with an editor or another worktree.
 
 Review the generated diff and run the final
 [quality gate](code-quality.md#final-gate). The final commit on the push must
diff --git a/scripts/release.py b/scripts/release.py
index 856f1c96..cbe4fcde 100644
--- a/scripts/release.py
+++ b/scripts/release.py
@@ -7,7 +7,6 @@
 import os
 from pathlib import Path
 import re
-import shutil
 import subprocess
 import sys
 import tarfile
@@ -35,9 +34,15 @@ def version_key(value):
             tuple((0, int(part)) if part.isdigit() else (1, part) for part in identifiers))
 
 
-def run(*args, capture=False):
+def run(*args, capture=False, env=None):
+    """Run a release command from the repository root.
+
+    ``env`` can override the process environment for isolated Cargo
+    operations without changing the environment used by ordinary release
+    checks.
+    """
     result = subprocess.run(args, cwd=ROOT, check=True, text=True,
-                            stdout=subprocess.PIPE if capture else None)
+                            stdout=subprocess.PIPE if capture else None, env=env)
     return result.stdout.strip() if capture else None
 
 
@@ -103,34 +108,25 @@ def workspace():
 
 def package_archives():
     current, names = workspace()
-    metadata = json.loads(run('cargo', 'metadata', '--locked', '--no-deps',
-                              '--format-version', '1', capture=True))
-    package_directory = Path(metadata['target_directory']) / 'package'
-    if package_directory.exists():
-        shutil.rmtree(package_directory)
-    clean = ['cargo', 'clean', '--locked', '--profile', 'dev']
-    for name in names:
-        clean.extend(['--package', name])
-    run(*clean)
     selection = [argument for name in names for argument in ('--package', name)]
-    # Package the complete publishable graph in one Cargo transaction so
-    # unpublished workspace versions resolve to one another instead of crates.io.
-    run('cargo', 'package', '--locked', '--all-features', '--allow-dirty',
-        '--no-verify', *selection)
-    verify_staged_archives(current, names)
+    # Keep package artifacts out of the checkout's shared target. In
+    # particular, never clean that target: it may be shared by an IDE, other
+    # worktrees, or sccache-backed builds running at the same time.
+    with tempfile.TemporaryDirectory(prefix='argui-package-target-') as directory:
+        target = Path(directory)
+        environment = os.environ.copy()
+        environment['CARGO_TARGET_DIR'] = str(target)
+        # Package the complete publishable graph in one Cargo transaction so
+        # unpublished workspace versions resolve to one another instead of
+        # crates.io.
+        run('cargo', 'package', '--locked', '--all-features', '--allow-dirty',
+            '--no-verify', *selection, env=environment)
+        verify_staged_archives(current, names, target)
     print(f'Verified {len(names)} crates.io archives at version {current}')
 
 
-def shared_target_directory():
-    """Return Cargo's configured target directory for this checkout."""
-    metadata = json.loads(run('cargo', 'metadata', '--locked', '--no-deps',
-                              '--format-version', '1', capture=True))
-    return Path(metadata['target_directory'])
-
-
-def verify_staged_archives(current, names):
+def verify_staged_archives(current, names, package_target):
     """Compile packaged sources together against only the staged archives."""
-    target = shared_target_directory()
     with tempfile.TemporaryDirectory(prefix='argui-package-') as directory:
         staged = Path(directory)
         config = staged / '.cargo' / 'config.toml'
@@ -138,7 +134,7 @@ def verify_staged_archives(current, names):
         patches = []
         members = []
         for name in names:
-            archive = target / 'package' / f'{name}-{current}.crate'
+            archive = package_target / 'package' / f'{name}-{current}.crate'
             if not archive.is_file():
                 raise ValueError(f'{name}: missing staged archive {archive}')
             with tarfile.open(archive, mode='r:gz') as package:
@@ -153,9 +149,19 @@ def verify_staged_archives(current, names):
             '[workspace]\nresolver = "2"\nmembers = [' + ', '.join(members) + ']\n'
         )
         environment = os.environ.copy()
-        environment['CARGO_TARGET_DIR'] = str(target)
+        # Keep verification's compiled output inside the temporary staging
+        # directory as well. The fetch/check order is intentional: fetch may
+        # populate the local registry, while check must prove the staged
+        # archives build without network access.
+        environment['CARGO_TARGET_DIR'] = str(staged / 'target')
+        subprocess.run(
+            ['cargo', 'fetch'],
+            cwd=staged,
+            env=environment,
+            check=True,
+        )
         subprocess.run(
-            ['cargo', 'check', '--offline', '--workspace', '--all-features'],
+            ['cargo', 'check', '--offline', '--locked', '--workspace', '--all-features'],
             cwd=staged,
             env=environment,
             check=True,
diff --git a/tests/scripts/test_release.py b/tests/scripts/test_release.py
index e0cb3d75..2c8818d1 100644
--- a/tests/scripts/test_release.py
+++ b/tests/scripts/test_release.py
@@ -206,26 +206,76 @@ def test_publication_order_rejects_cycles_and_facade_dependents(self):
 
     def test_package_verifies_every_archive_in_publication_order(self):
         names = ['argui-core', 'argui-render', 'argui']
+        targets = []
+
+        def verify(current, actual_names, target):
+            self.assertEqual((current, actual_names), ('0.1.0', names))
+            self.assertTrue(target.is_dir())
+            targets.append(target)
+
         with tempfile.TemporaryDirectory() as directory:
-            package_directory = Path(directory) / 'package'
-            package_directory.mkdir()
-            (package_directory / 'stale-registry').write_text('old archive')
-            metadata = json.dumps({'target_directory': directory})
+            shared_package_directory = Path(directory) / 'package'
+            shared_package_directory.mkdir()
+            (shared_package_directory / 'stale-registry').write_text('old archive')
             with patch.object(release, 'workspace', return_value=('0.1.0', names)), \
-                    patch.object(release, 'run', side_effect=[metadata, None, None]) as run, \
-                    patch.object(release, 'verify_staged_archives') as verify:
+                    patch.object(release, 'run') as run, \
+                    patch.object(release, 'verify_staged_archives', side_effect=verify):
                 release.package_archives()
-            self.assertFalse(package_directory.exists())
-        self.assertEqual(run.call_args_list[1].args, (
-            'cargo', 'clean', '--locked', '--profile', 'dev',
-            '--package', 'argui-core', '--package', 'argui-render', '--package', 'argui',
-        ))
-        self.assertEqual(run.call_args_list[2].args, (
+            self.assertTrue((shared_package_directory / 'stale-registry').exists())
+        self.assertEqual(run.call_count, 1)
+        self.assertEqual(run.call_args.args, (
             'cargo', 'package', '--locked', '--all-features', '--allow-dirty',
             '--no-verify',
             '--package', 'argui-core', '--package', 'argui-render', '--package', 'argui',
         ))
-        verify.assert_called_once_with('0.1.0', names)
+        target = targets[0]
+        self.assertFalse(target.exists())
+        self.assertEqual(Path(run.call_args.kwargs['env']['CARGO_TARGET_DIR']), target)
+
+    def test_archive_verification_fetches_before_the_offline_locked_check(self):
+        names = ['argui-core', 'argui']
+
+        class Archive:
+            def __init__(self, name):
+                self.name = name
+
+            def __enter__(self):
+                return self
+
+            def __exit__(self, *_):
+                return False
+
+            def extractall(self, destination, filter):
+                if filter != 'data':
+                    raise AssertionError(f'unexpected archive filter: {filter}')
+                source = destination / self.name.removesuffix('.crate')
+                source.mkdir()
+                (source / 'Cargo.toml').write_text('[package]\nname = "staged"\n')
+
+        with tempfile.TemporaryDirectory() as directory:
+            target = Path(directory)
+            package_directory = target / 'package'
+            package_directory.mkdir()
+            for name in names:
+                (package_directory / f'{name}-0.3.0.crate').touch()
+
+            def archive(path, mode):
+                self.assertEqual(mode, 'r:gz')
+                return Archive(Path(path).name)
+
+            with patch.object(release.tarfile, 'open', side_effect=archive), \
+                    patch.object(release.subprocess, 'run') as run:
+                release.verify_staged_archives('0.3.0', names, target)
+
+        self.assertEqual(run.call_count, 2)
+        self.assertEqual(run.call_args_list[0].args[0], ['cargo', 'fetch'])
+        self.assertEqual(
+            run.call_args_list[1].args[0],
+            ['cargo', 'check', '--offline', '--locked', '--workspace', '--all-features'],
+        )
+        self.assertNotEqual(
+            Path(run.call_args_list[1].kwargs['env']['CARGO_TARGET_DIR']), target,
+        )
 
     def test_unchanged_version_never_runs_a_publisher(self):
         with patch.object(release, 'run') as run:
diff --git a/website/scripts/gallery.mjs b/website/scripts/gallery.mjs
index 51b48719..72bdfe14 100644
--- a/website/scripts/gallery.mjs
+++ b/website/scripts/gallery.mjs
@@ -1,5 +1,5 @@
 import { access, cp, mkdir, rm } from 'node:fs/promises'
-import { spawnSync } from 'node:child_process'
+import { spawn } from 'node:child_process'
 import { fileURLToPath } from 'node:url'
 import { resolve } from 'node:path'
 
@@ -8,11 +8,137 @@ const destination = resolve(root, 'website/public/gallery')
 const aiDestination = resolve(root, 'website/public/examples/ai-harness')
 const gpuDestination = resolve(root, 'website/public/examples/gpu-canvas')
 const docsDestination = resolve(root, 'website/public/examples/docs')
-const wasmEnvironment = {
-  ...process.env,
-  CARGO_BUILD_JOBS: '6',
-  BINARYEN_CORES: '6',
+const wasmEnvironment = { ...process.env }
+const defaultBuildConcurrency = 2
+
+const wasmBuilds = [
+  {
+    label: 'widget gallery',
+    args: [
+      'build',
+      'crates/argui-widget-gallery',
+      '--target',
+      'web',
+      '--release',
+      '--out-dir',
+      '../../web/widgets/pkg',
+      '--all-features',
+    ],
+  },
+  {
+    label: 'AI harness example',
+    args: [
+      'build',
+      'app_examples/fake-ai-harness',
+      '--target',
+      'web',
+      '--release',
+      '--out-dir',
+      '../../web/examples/ai-harness/pkg',
+    ],
+  },
+  {
+    label: 'GPU canvas example',
+    args: [
+      'build',
+      'app_examples/gpu-canvas',
+      '--target',
+      'web',
+      '--release',
+      '--out-dir',
+      '../../web/examples/gpu-canvas/pkg',
+    ],
+  },
+  {
+    label: 'docs examples',
+    args: [
+      'build',
+      'app_examples/docs-examples',
+      '--target',
+      'web',
+      '--release',
+      '--out-dir',
+      '../../web/examples/docs/pkg',
+    ],
+  },
+]
+
+/**
+ * Reads a positive integer setting without allowing malformed values to alter
+ * the worker pool unexpectedly.
+ *
+ * @param {string | undefined} value The environment value to parse.
+ * @param {number} fallback The value to use when the setting is invalid.
+ * @returns {number} A positive integer suitable for a worker count.
+ */
+function positiveInteger(value, fallback) {
+  if (!value || !/^\d+$/.test(value)) return fallback
+  const parsed = Number(value)
+  return Number.isSafeInteger(parsed) && parsed > 0 ? parsed : fallback
+}
+
+/**
+ * Runs one wasm-pack build while streaming its output directly to the caller.
+ *
+ * @param {{ label: string, args: string[] }} build The build command to run.
+ * @returns {Promise<void>} Resolves when the build succeeds.
+ * @throws {Error} If wasm-pack cannot start or exits unsuccessfully.
+ */
+function runWasmBuild(build) {
+  return new Promise((resolveBuild, rejectBuild) => {
+    const child = spawn('wasm-pack', build.args, {
+      cwd: root,
+      env: wasmEnvironment,
+      stdio: 'inherit',
+    })
+
+    child.once('error', (error) => {
+      rejectBuild(new Error(`${build.label} could not start: ${error.message}`, { cause: error }))
+    })
+    child.once('close', (code, signal) => {
+      if (code === 0) {
+        resolveBuild()
+        return
+      }
+      const reason = signal ? `signal ${signal}` : `exit code ${code ?? 'unknown'}`
+      const error = new Error(`${build.label} failed with ${reason}`)
+      if (code !== null) error.exitCode = code
+      rejectBuild(error)
+    })
+  })
 }
+
+/**
+ * Runs wasm builds through a bounded worker pool so independent bundles can
+ * overlap without spawning one process per bundle at once.
+ *
+ * @param {{ label: string, args: string[] }[]} builds The builds to execute.
+ * @param {number} concurrency The maximum number of active wasm-pack processes.
+ * @returns {Promise<void>} Resolves when every build succeeds.
+ * @throws {Error} The first build error after active workers have drained.
+ */
+async function runWasmBuilds(builds, concurrency) {
+  let nextBuild = 0
+  let firstError
+
+  async function worker() {
+    while (firstError === undefined) {
+      const build = builds[nextBuild]
+      nextBuild += 1
+      if (!build) return
+      try {
+        await runWasmBuild(build)
+      } catch (error) {
+        firstError = error
+      }
+    }
+  }
+
+  const workerCount = Math.min(concurrency, builds.length)
+  await Promise.all(Array.from({ length: workerCount }, () => worker()))
+  if (firstError) throw firstError
+}
+
 if (process.argv.includes('--check')) {
   try {
     await access(resolve(destination, 'pkg/argui_widget_gallery_bg.wasm'))
@@ -27,67 +153,17 @@ if (process.argv.includes('--check')) {
   }
 } else {
   if (!process.argv.includes('--copy')) {
-    const build = spawnSync(
-      'wasm-pack',
-      [
-        'build',
-        'crates/argui-widget-gallery',
-        '--target',
-        'web',
-        '--release',
-        '--out-dir',
-        '../../web/widgets/pkg',
-        '--all-features',
-      ],
-      {
-        cwd: root,
-        stdio: 'inherit',
-        env: wasmEnvironment,
-      },
-    )
-    if (build.status !== 0) process.exit(build.status ?? 1)
-    const exampleBuild = spawnSync(
-      'wasm-pack',
-      [
-        'build',
-        'app_examples/fake-ai-harness',
-        '--target',
-        'web',
-        '--release',
-        '--out-dir',
-        '../../web/examples/ai-harness/pkg',
-      ],
-      { cwd: root, stdio: 'inherit', env: wasmEnvironment },
-    )
-    if (exampleBuild.status !== 0) process.exit(exampleBuild.status ?? 1)
-    const gpuBuild = spawnSync(
-      'wasm-pack',
-      [
-        'build',
-        'app_examples/gpu-canvas',
-        '--target',
-        'web',
-        '--release',
-        '--out-dir',
-        '../../web/examples/gpu-canvas/pkg',
-      ],
-      { cwd: root, stdio: 'inherit', env: wasmEnvironment },
-    )
-    if (gpuBuild.status !== 0) process.exit(gpuBuild.status ?? 1)
-    const docsBuild = spawnSync(
-      'wasm-pack',
-      [
-        'build',
-        'app_examples/docs-examples',
-        '--target',
-        'web',
-        '--release',
-        '--out-dir',
-        '../../web/examples/docs/pkg',
-      ],
-      { cwd: root, stdio: 'inherit', env: wasmEnvironment },
+    const concurrency = positiveInteger(
+      process.env.ARGUI_WASM_BUILD_CONCURRENCY,
+      defaultBuildConcurrency,
     )
-    if (docsBuild.status !== 0) process.exit(docsBuild.status ?? 1)
+    try {
+      await runWasmBuilds(wasmBuilds, concurrency)
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error)
+      console.error(`WASM gallery build failed: ${message}`)
+      process.exit(error?.exitCode ?? 1)
+    }
   }
   await access(resolve(root, 'web/widgets/pkg/argui_widget_gallery_bg.wasm'))
   await access(resolve(root, 'web/examples/ai-harness/pkg/argui_example_ai_harness_bg.wasm'))