diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 000000000..7558149ec
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,48 @@
+# Every pull request: build the tree and test the packages this fork changes. The rest is upstream Prysm and is tested
+# there.
+name: CI
+
+on:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-go@v7
+        with:
+          go-version-file: go.mod
+
+      - run: go build ./...
+
+      # The fork's changes: the inactivity ejection in epoch processing, the slot schedule and what is timed by it, and
+      # the genesis tooling in prysmctl.
+      #
+      # Skipped: two epoch tests that expect the upstream balances and fail on main as it stands, the tests that read
+      # their data from a Bazel runfiles directory, which go test does not provide, and two upstream tests that pass on
+      # one run and fail on the next (TestAggregateAndSaveForkChoiceAtts_Multiple, TestProcessLogs_DepositRequestsStarted).
+      - run: >
+          go test -tags develop -timeout 30m
+          -skip '^(TestProcessEpoch_CanProcess|TestProcessEpoch_CanProcessBellatrix|TestEIP3076SpecTests|TestLoadConfigFile|Test(Mainnet|Holesky|Hoodi|Sepolia)ConfigMatchesUpstreamYaml|TestAggregateAndSaveForkChoiceAtts_Multiple|TestProcessLogs_DepositRequestsStarted)$'
+          ./beacon-chain/core/altair
+          ./beacon-chain/core/epoch
+          ./beacon-chain/execution
+          ./beacon-chain/operations/attestations
+          ./cmd/prysmctl/testnet
+          ./config/params
+          ./time/slots
+          ./validator/client
+
+      # In beacon-chain/blockchain the fork changes only the attestation routine, so only that file's tests run.
+      # Elsewhere in the package a failing test panics inside the assertion helper and takes the whole run down.
+      - run: >
+          go test -tags develop ./beacon-chain/blockchain
+          -run '^(TestAttestationCheckPtState_FarFutureSlot|TestVerifyLMDFFGConsistent|TestProcessAttestations_Ok|TestService_ProcessAttestationsAndUpdateHead|TestService_UpdateHead_NoAtts)$'