diff --git a/.github/workflows/go-test.yml b/.github/workflows/go-test.yml
index f0364023f7..9b8add2ed5 100644
--- a/.github/workflows/go-test.yml
+++ b/.github/workflows/go-test.yml
@@ -18,11 +18,32 @@ env:
   # state_db tests run in their own workflow (sei-db-tests.yml); exclude
   # that subtree everywhere in this workflow to avoid double-running them.
   STATE_DB_PKG_PREFIX: github.com/sei-protocol/sei-chain/sei-db/state_db
+  # Number of race-detection shards. Matches `NUM_SPLIT` passed to
+  # `make test-group-N` so shards are locally reproducible.
+  NUM_SPLIT: 3
 
 jobs:
+  shard-indexes:
+    name: Generate race shard indexes
+    runs-on: ubuntu-latest
+    outputs:
+      json: ${{ steps.generate-index-list.outputs.json }}
+    steps:
+      - id: generate-index-list
+        run: |
+          MAX_INDEX=$((${{ env.NUM_SPLIT }}-1))
+          INDEX_LIST=$(seq 0 ${MAX_INDEX})
+          INDEX_JSON=$(jq --null-input --compact-output '. |= [inputs]' <<< ${INDEX_LIST})
+          echo "json=${INDEX_JSON}" >> "$GITHUB_OUTPUT"
+
   test:
-    name: Race Detection
+    name: "Race Detection (shard ${{ matrix.shard }})"
     runs-on: uci-default
+    needs: shard-indexes
+    strategy:
+      fail-fast: false
+      matrix:
+        shard: ${{ fromJson(needs.shard-indexes.outputs.json) }}
     env:
       GOFLAGS: -race -tags=ledger,test_ledger_mock
     steps:
@@ -52,9 +73,27 @@ jobs:
       - name: Go test
         run: |
           set -euo pipefail
-          PKGS=$(go list ./... | grep -v "^${STATE_DB_PKG_PREFIX}")
-          echo "$PKGS" | xargs go test \
-            -timeout=${{ env.GO_TEST_TIMEOUT }}
+          make split-test-packages NUM_SPLIT=${{ env.NUM_SPLIT }}
+          SHARD_FILE=build/packages.txt.${{ matrix.shard }}
+          PARALLEL=()
+          if grep -qx "github.com/sei-protocol/sei-chain/occ_tests" "$SHARD_FILE"; then
+            echo "occ_tests present in this shard; forcing -parallel=1"
+            PARALLEL=(-parallel=1)
+          fi
+          xargs go test "${PARALLEL[@]}" -timeout=${{ env.GO_TEST_TIMEOUT }} < "$SHARD_FILE"
+
+  test-check:
+    name: Race Detection
+    runs-on: ubuntu-latest
+    needs: test
+    if: always()
+    steps:
+      - name: Check shard results
+        run: |
+          if [[ "${{ needs.test.result }}" != "success" ]]; then
+            echo "One or more Race Detection shards failed"
+            exit 1
+          fi
 
   coverage:
     name: Coverage
diff --git a/AGENTS.md b/AGENTS.md
index fa3426f844..01434ebba1 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -99,12 +99,15 @@ make build    # build the seid binary into ./build/seid
 make install  # install seid into $GOBIN
 ```
 
-Tests run with the race detector and coverage. CI shards them into groups; while
-iterating, run a single package directly:
+Tests run with the race detector and coverage. `go-test.yml`'s Race Detection job
+shards into `NUM_SPLIT` (currently 3) parallel matrix jobs, round-robin split
+(package `i` goes to shard `i % NUM_SPLIT`, not a contiguous chunk — see the
+`split-test-packages` Makefile target). `make test-group-N` reproduces a given
+shard locally with the same package split:
 
 ```bash
-make test-group-0       # one CI test shard (race + coverage)
-go test ./<pkg>/...     # run a single package
+NUM_SPLIT=3 make test-group-0   # reproduce CI race shard 0 locally
+go test ./<pkg>/...              # run a single package
 ```
 
 CI mirrors these checks: `.github/workflows/golangci.yml` runs golangci-lint
diff --git a/Makefile b/Makefile
index 82448449f0..255e4508a3 100644
--- a/Makefile
+++ b/Makefile
@@ -569,19 +569,60 @@ GO_TEST_FILES != find $(CURDIR) -name "*_test.go"
 # default to four splits by default
 NUM_SPLIT ?= 4
 
+# state_db tests run in their own workflow (sei-db-tests.yml); exclude that
+# subtree here too so local shards match the CI shards exactly.
+STATE_DB_PKG_PREFIX := github.com/sei-protocol/sei-chain/sei-db/state_db
+
 $(BUILDDIR):
 	mkdir -p $@
 
-# The format statement filters out all packages that don't have tests.
-# Note we need to check for both in-package tests (.TestGoFiles) and
-# out-of-package tests (.XTestGoFiles).
+# Includes every package, not just ones with test files: `go test` on a
+# package with no tests still compiles it (reported as "no test files"),
+# which is how go-test.yml's Race Detection job also acts as a compile
+# check under -race -tags=ledger,test_ledger_mock for the whole tree.
+# Filtering to test-only packages here would silently drop that coverage.
 $(BUILDDIR)/packages.txt:$(GO_TEST_FILES) $(BUILDDIR)
-	go list -f "{{ if (or .TestGoFiles .XTestGoFiles) }}{{ .ImportPath }}{{ end }}" ./... | sort > $@
+	go list ./... > $@.tmp
+	grep -v "^$(STATE_DB_PKG_PREFIX)" $@.tmp | sort > $@
+	@rm -f $@.tmp
 
 TARGET_PACKAGE := github.com/sei-protocol/sei-chain/occ_tests
 
+# Packages whose test suite alone regularly runs 1-4+ minutes under -race.
+# Plain i%N round-robin assigns these by their position in the full,
+# alphabetically-sorted package list, so several of them can land on the
+# same shard by coincidence. Splitting them into their own round-robin
+# pass, ahead of the rest of the list, guarantees consecutive heavy
+# packages rotate across shards instead of clustering. Re-derive this list
+# occasionally from a race job's `ok  <pkg>  <secs>s` log lines.
+HEAVY_TEST_PACKAGES := \
+	github.com/sei-protocol/sei-chain/sei-db/db_engine/litt/disktable \
+	github.com/sei-protocol/sei-chain/sei-cosmos/storev2/rootmulti \
+	github.com/sei-protocol/sei-chain/sei-db/db_engine/litt/test \
+	github.com/sei-protocol/sei-chain/sei-ibc-go/modules/core/04-channel/keeper \
+	github.com/sei-protocol/sei-chain/giga/tests \
+	github.com/sei-protocol/sei-chain/sei-cosmos/x/staking/keeper \
+	github.com/sei-protocol/sei-chain/evmrpc/tests \
+	github.com/sei-protocol/sei-chain/sei-ibc-go/modules/core/03-connection/keeper \
+	github.com/sei-protocol/sei-chain/sei-ibc-go/modules/apps/transfer/keeper \
+	github.com/sei-protocol/sei-chain/sei-cosmos/x/bank/keeper
+
+# Round-robin split: package i goes to shard i%N.
+# Interleaving avoids dumping a whole cluster of alphabetically-adjacent
+# (and often runtime-correlated, e.g. a module's many keeper packages)
+# packages into one shard, unlike a straight `split -d -n l/N` chunk split.
+# Pre-touch all N files first so a shard with zero packages (NUM_SPLIT >
+# package count) still gets an (empty) file instead of breaking test-group-%.
+# HEAVY_TEST_PACKAGES is round-robined separately, and first, so its own
+# i%N indexing can't collide with the coincidental clustering above.
 split-test-packages:$(BUILDDIR)/packages.txt
-	split -d -n l/$(NUM_SPLIT) $< $<.
+	@for i in $$(seq 0 $$(($(NUM_SPLIT)-1))); do : > $(BUILDDIR)/packages.txt.$$i; done
+	@printf '%s\n' $(HEAVY_TEST_PACKAGES) > $(BUILDDIR)/heavy-packages.txt
+	@grep -Fxf $(BUILDDIR)/heavy-packages.txt $< > $(BUILDDIR)/packages.txt.heavy || true
+	@grep -Fxvf $(BUILDDIR)/heavy-packages.txt $< > $(BUILDDIR)/packages.txt.rest || true
+	@awk -v n=$(NUM_SPLIT) -v dir=$(BUILDDIR) '{print >> (dir "/packages.txt." (NR-1)%n)}' $(BUILDDIR)/packages.txt.heavy
+	@awk -v n=$(NUM_SPLIT) -v dir=$(BUILDDIR) '{print >> (dir "/packages.txt." (NR-1)%n)}' $(BUILDDIR)/packages.txt.rest
+	@rm -f $(BUILDDIR)/heavy-packages.txt $(BUILDDIR)/packages.txt.heavy $(BUILDDIR)/packages.txt.rest
 test-group-%:split-test-packages
 	@echo "🔍 Checking for special package: $(TARGET_PACKAGE)"
 	@if grep -q "$(TARGET_PACKAGE)" $(BUILDDIR)/packages.txt.$*; then \