diff --git a/.github/workflows/runtime-interface-client_pr.yml b/.github/workflows/runtime-interface-client_pr.yml
index 98618396..885b952c 100644
--- a/.github/workflows/runtime-interface-client_pr.yml
+++ b/.github/workflows/runtime-interface-client_pr.yml
@@ -111,6 +111,9 @@ jobs:
     strategy:
       # Run every OS/arch combination to completion so one failure doesn't mask the others.
       fail-fast: false
+      # Every shard pulls its images anonymously from public.ecr.aws, and shards
+      # started together trip its rate limit (429), so cap how many run at once.
+      max-parallel: 4
       matrix:
         buildspec:
           - buildspec.os.alpine.yml
@@ -136,15 +139,6 @@ jobs:
               platform: linux/arm64/v8
     name: "integration-test (${{ matrix.buildspec }} / ${{ matrix.arch.label }})"
     steps:
-    - name: Jitter start (stagger matrix shards to spare public.ecr.aws rate limit)
-      # Every shard is scheduled within milliseconds of the others and hits
-      # public.ecr.aws / docker hub inside the same rate-limit window, so they
-      # collectively trip the throttle.
-      run: |
-        jitter=$((RANDOM % 61))
-        echo "Sleeping ${jitter}s to stagger this shard"
-        sleep "${jitter}"
-
     - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
 
     - name: Set up Docker Buildx
diff --git a/aws-lambda-java-runtime-interface-client/Makefile b/aws-lambda-java-runtime-interface-client/Makefile
index 770671c0..6d1a7762 100644
--- a/aws-lambda-java-runtime-interface-client/Makefile
+++ b/aws-lambda-java-runtime-interface-client/Makefile
@@ -37,6 +37,9 @@ setup-codebuild-agent:
 .PHONY: test-smoke
 test-smoke: test-smoke-x86_64 test-smoke-aarch64
 
+# amazoncorretto 11 is left out of the CI integration matrix
+# (buildspec.os.amazoncorretto.yml) because smoke already covers it. Changing it
+# here changes integration coverage too.
 .PHONY: test-smoke-x86_64
 test-smoke-x86_64: setup-codebuild-agent
 	CODEBUILD_IMAGE_TAG=codebuild-agent test/integration/codebuild-local/test_one.sh test/integration/codebuild/buildspec.os.alpine.yml alpine 3.15 corretto11 linux/amd64
@@ -64,11 +67,13 @@ dev: test
 pr: test test-smoke
 
 # Per-architecture PR checks so CI can run each on a native runner (no QEMU).
+# No `test` here: the required `build` check already runs the unit tests
+# (build-<arch>), so CI would only run them twice.
 .PHONY: pr-x86_64
-pr-x86_64: test test-smoke-x86_64
+pr-x86_64: test-smoke-x86_64
 
 .PHONY: pr-aarch64
-pr-aarch64: test test-smoke-aarch64
+pr-aarch64: test-smoke-aarch64
 
 .PHONY: build
 build: build-x86_64 build-aarch64
diff --git a/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.alpine.yml b/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.alpine.yml
index 65a9da50..595de79f 100644
--- a/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.alpine.yml
+++ b/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.alpine.yml
@@ -16,8 +16,6 @@ batch:
       env:
         variables:
           DISTRO_VERSION:
-            - "3.13"
-            - "3.14"
             - "3.15"
           RUNTIME_VERSION:
             - "corretto11"
diff --git a/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.amazoncorretto.yml b/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.amazoncorretto.yml
index c578235f..efa99cec 100644
--- a/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.amazoncorretto.yml
+++ b/aws-lambda-java-runtime-interface-client/test/integration/codebuild/buildspec.os.amazoncorretto.yml
@@ -18,8 +18,8 @@ batch:
           DISTRO_VERSION:
             - "amazoncorretto"
           RUNTIME_VERSION:
+            # 11 is covered by the smoke tests (Makefile, test-smoke-<arch>).
             - "8"
-            - "11"
           PLATFORM:
             - "linux/amd64"
             - "linux/arm64/v8"