diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6c1bc887..0a0f5ae5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,7 +24,7 @@ defaults:
 
 jobs:
   detect-changes:
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-linux-x64-default
     permissions:
       contents: read
       pull-requests: read
@@ -43,7 +43,7 @@ jobs:
     needs: detect-changes
     if: needs.detect-changes.outputs.code-changed == 'true'
     name: Clippy
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-linux-x64-default
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
@@ -57,7 +57,10 @@ jobs:
           components: clippy
 
       - run: rustup target add x86_64-unknown-linux-musl
-      - run: pip install cargo-zigbuild
+      - run: pipx install cargo-zigbuild
+      # pipx isolates cargo-zigbuild in its own venv, so its ziglang dependency
+      # (which bundles zig) isn't on PATH. Install zig separately.
+      - uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2
 
       # --locked: verify Cargo.lock is up to date (replaces the removed `cargo check --locked`)
       - run: cargo clippy --locked --all-targets --all-features -- -D warnings
@@ -70,14 +73,22 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-latest
+          - os: namespace-profile-linux-x64-default
             target: x86_64-unknown-linux-gnu
+            cargo_cmd: cargo-zigbuild
+            build_target: x86_64-unknown-linux-gnu.2.17
           - os: windows-latest
             target: x86_64-pc-windows-msvc
-          - os: macos-latest
+            cargo_cmd: cargo
+            build_target: x86_64-pc-windows-msvc
+          - os: namespace-profile-mac-default
             target: aarch64-apple-darwin
-          - os: macos-latest
+            cargo_cmd: cargo
+            build_target: aarch64-apple-darwin
+          - os: namespace-profile-mac-default
             target: x86_64-apple-darwin
+            cargo_cmd: cargo
+            build_target: x86_64-apple-darwin
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
@@ -102,10 +113,15 @@ jobs:
       - run: rustup target add ${{ matrix.target }}
 
       - run: rustup target add x86_64-unknown-linux-musl
-        if: ${{ matrix.os == 'ubuntu-latest' }}
+        if: ${{ matrix.target == 'x86_64-unknown-linux-gnu' }}
 
-      - run: pip install cargo-zigbuild
-        if: ${{ matrix.os == 'ubuntu-latest' }}
+      - run: pipx install cargo-zigbuild
+        if: ${{ matrix.target == 'x86_64-unknown-linux-gnu' }}
+
+      # pipx isolates cargo-zigbuild in its own venv, so its ziglang dependency
+      # (which bundles zig) isn't on PATH. Install zig separately.
+      - uses: mlugg/setup-zig@d1434d08867e3ee9daa34448df10607b98908d29 # v2
+        if: ${{ matrix.target == 'x86_64-unknown-linux-gnu' }}
 
       # For x86_64-apple-darwin on arm64 runner, install x64 node so fspy preload dylib
       # (compiled for x86_64) can be injected into node processes running under Rosetta.
@@ -128,26 +144,16 @@ jobs:
       - run: pnpm install
 
       - name: Build tests
-        run: cargo test --no-run --target ${{ matrix.target }}
-        if: ${{ matrix.os != 'ubuntu-latest' }}
-
-      - name: Build tests
-        run: cargo-zigbuild test --no-run --target x86_64-unknown-linux-gnu.2.17
-        if: ${{ matrix.os == 'ubuntu-latest' }}
-
-      - name: Run tests
-        run: cargo test --target ${{ matrix.target }}
-        if: ${{ matrix.os != 'ubuntu-latest' }}
+        run: ${{ matrix.cargo_cmd }} test --no-run --target ${{ matrix.build_target }}
 
       - name: Run tests
-        run: cargo-zigbuild test --target x86_64-unknown-linux-gnu.2.17
-        if: ${{ matrix.os == 'ubuntu-latest' }}
+        run: ${{ matrix.cargo_cmd }} test --target ${{ matrix.build_target }}
 
   test-musl:
     needs: detect-changes
     if: needs.detect-changes.outputs.code-changed == 'true'
     name: Test (musl)
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-linux-x64-default
     container:
       image: node:22-alpine3.21
       options: --shm-size=256m # shm_io tests need bigger shared memory
@@ -193,7 +199,7 @@ jobs:
 
   fmt:
     name: Format and Check Deps
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-linux-x64-default
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
@@ -221,7 +227,7 @@ jobs:
         run: pnpm dedupe --check
 
   done:
-    runs-on: ubuntu-latest
+    runs-on: namespace-profile-linux-x64-default
     if: always()
     needs:
       - clippy
diff --git a/README.md b/README.md
index a3cee071..26206b79 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,10 @@ vp run -t @my/app#build   # run in a package and its transitive dependencies
 vp run --cache build      # run with caching enabled
 ```
 
+## Sponsors
+
+Thanks to [namespace.so](https://namespace.so) for powering our CI/CD pipelines with fast, free macOS and Linux runners.
+
 ## License
 
 [MIT](LICENSE)