diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f5393b0ef..ded718a77 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,6 +23,11 @@ jobs:
         python: ["3.10", "3.14"]
         os: [ubuntu-latest, ubuntu-arm, macos-arm, windows-latest]
         include:
+          - os: ubuntu-latest
+            runsOn: ubuntu-latest-16-cores
+            # Keep xdist parallelism at the standard runner level so the local
+            # test service is not overwhelmed by more concurrent workers.
+            pytestWorkerArg: "-n 4"
           - os: ubuntu-latest
             python: "3.14"
             docsTarget: true
@@ -62,14 +67,14 @@ jobs:
       - run: poe build-develop
       - run: poe lint
       - run: mkdir junit-xml
-      - run: poe test ${{matrix.pytestExtraArgs}} -s --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}.xml
+      - run: poe test ${{matrix.pytestExtraArgs}} ${{matrix.pytestWorkerArg}} -s --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}.xml
         timeout-minutes: 15
       # Time skipping doesn't yet support ARM
       - if: ${{ !endsWith(matrix.os, '-arm') }}
-        run: poe test ${{matrix.pytestExtraArgs}} -s --workflow-environment time-skipping --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--time-skipping.xml
+        run: poe test ${{matrix.pytestExtraArgs}} ${{matrix.pytestWorkerArg}} -s --workflow-environment time-skipping --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--time-skipping.xml
         timeout-minutes: 10
       - if: ${{ matrix.openaiTestTarget && (github.event.pull_request.head.repo.full_name == '' || github.event.pull_request.head.repo.full_name == 'temporalio/sdk-python') }}
-        run: poe test tests/contrib/openai_agents/test_openai.py ${{matrix.pytestExtraArgs}} -s  --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--openai.xml
+        run: poe test tests/contrib/openai_agents/test_openai.py ${{matrix.pytestExtraArgs}} ${{matrix.pytestWorkerArg}} -s  --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--openai.xml
         timeout-minutes: 10
         env:
           OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
@@ -106,7 +111,7 @@ jobs:
   # FIPS binary and build the release wheel.
   fips-build:
     timeout-minutes: 45
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-16-cores
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
@@ -190,7 +195,7 @@ jobs:
       matrix:
         include:
           - cibw-build: cp310-musllinux_x86_64
-            runsOn: ubuntu-latest
+            runsOn: ubuntu-latest-16-cores
           - cibw-build: cp310-musllinux_aarch64
             runsOn: ubuntu-24.04-arm64-2-core
     runs-on: ${{ matrix.runsOn }}
@@ -214,7 +219,7 @@ jobs:
 
   check-protos:
     timeout-minutes: 30
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-16-cores
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
@@ -251,7 +256,7 @@ jobs:
 
   test-latest-deps:
     timeout-minutes: 30
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-16-cores
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
@@ -292,7 +297,7 @@ jobs:
   cloud-test:
     if: ${{ github.actor != 'dependabot[bot]' && (github.event.pull_request.head.repo.full_name == '' || github.event.pull_request.head.repo.full_name == 'temporalio/sdk-python') }}
     timeout-minutes: 30
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-16-cores
     steps:
       - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with: