diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a10186f..80631e9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -39,15 +39,6 @@ jobs:
             echo "$module $version"
             [[ $version =~ ^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)$ ]]
           done
-      - name: The previous pins are the versions right before the current ones
-        run: |
-          current=$(go list -m -f '{{.Version}}' github.com/batchstream/weir-go)
-          previous=$(go list -m -versions github.com/batchstream/weir-go | tr ' ' '\n' | grep -B1 -x "$current" | head -n 1)
-          echo "weir-go $previous then $current"
-          [[ $previous =~ ^v && $previous != "$current" && $(jq -er .weir_go_previous versions.json) == "$previous" ]]
-          server=$(jq -er .weir_previous_source versions.json)
-          echo "server $server then $(jq -er .weir_source versions.json)"
-          [[ $server =~ ^[0-9a-f]{40}$ && $server != "$(jq -er .weir_source versions.json)" ]]
       - name: Tests, vet and formatting
         run: |
           go mod tidy -diff
@@ -59,40 +50,6 @@ jobs:
           python3 -O -m unittest discover -s scripts -p '*_test.py'
           test -z "$(gofmt -l cmd internal tests)"
           git diff --exit-code
-  version-skew:
-    runs-on: ubuntu-24.04
-    timeout-minutes: 20
-    strategy:
-      fail-fast: false
-      matrix:
-        target: [integration-previous-server, integration-previous-sdk]
-    steps:
-      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
-        with:
-          ref: ${{ github.event.pull_request.head.sha || github.sha }}
-          persist-credentials: false
-      - uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16
-        with:
-          go-version-file: go.mod
-      - name: Install the pinned Weir and mongod
-        run: |
-          make prepare prepare-previous
-          mongod=$(scripts/mongod.sh)
-          printf 'WEIR_TEST_MONGODB_BINARY=%s\n' "$mongod" >> "$GITHUB_ENV"
-      - name: Real multi-node integration, one side a version behind
-        run: make ${{ matrix.target }}
-      - name: Upload fixture logs
-        if: always()
-        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02
-        with:
-          name: ${{ matrix.target }}-${{ github.sha }}
-          path: |
-            /tmp/weir-tests-*/manifest.json
-            /tmp/weir-tests-*/cleanup.json
-            /tmp/weir-tests-*/*config.json
-            /tmp/weir-tests-*/*process.log
-            /tmp/weir-tests-*/docker-engine.json
-          retention-days: 14
   blackbox:
     runs-on: ubuntu-24.04
     timeout-minutes: 20
diff --git a/Makefile b/Makefile
index 600ae49..35e223c 100644
--- a/Makefile
+++ b/Makefile
@@ -1,13 +1,9 @@
-.PHONY: prepare prepare-previous test integration integration-previous-server integration-previous-sdk benchmark diagnostic
+.PHONY: prepare test integration benchmark diagnostic
 
 prepare:
 	revision=$$(jq -er .weir_source versions.json) && \
 		GOBIN="$(CURDIR)/.tools" go install -ldflags "-X main.revision=$$revision" github.com/batchstream/weir/cmd/weir@$$revision
 
-prepare-previous:
-	revision=$$(jq -er .weir_previous_source versions.json) && \
-		GOBIN="$(CURDIR)/.tools/previous" go install -ldflags "-X main.revision=$$revision" github.com/batchstream/weir/cmd/weir@$$revision
-
 test:
 	go test -race -count=1 ./...
 	python3 -m unittest discover -s scripts -p '*_test.py'
@@ -15,20 +11,6 @@ test:
 integration:
 	WEIR_TEST_BINARY="$(CURDIR)/.tools/weir" go test -race -tags=integration -count=1 -timeout=10m -v ./tests/integration
 
-integration-previous-server:
-	WEIR_TEST_BINARY="$(CURDIR)/.tools/previous/weir" go test -race -tags=integration,previous -count=1 -timeout=10m -v ./tests/integration
-
-# GOFLAGS, not a flag of go test, so that any binary a test builds uses the same SDK.
-# The SDK brings the protocol version it was released with, as it does for a caller.
-integration-previous-sdk:
-	mkdir -p .tools
-	cp go.mod .tools/previous-sdk.mod
-	cp go.sum .tools/previous-sdk.sum
-	version=$$(jq -er .weir_go_previous versions.json) && \
-		protocol=$$(go mod download -json github.com/batchstream/weir-go@$$version | jq -er .GoMod | xargs awk '$$1 == "github.com/batchstream/weir-protocol" {print $$2}') && \
-		go get -modfile=.tools/previous-sdk.mod github.com/batchstream/weir-go@$$version github.com/batchstream/weir-protocol@$$protocol
-	GOFLAGS=-modfile="$(CURDIR)/.tools/previous-sdk.mod" WEIR_TEST_BINARY="$(CURDIR)/.tools/weir" go test -race -tags=integration,previous -count=1 -timeout=10m -v ./tests/integration
-
 benchmark:
 	go run ./cmd/weir-lab -mode saturation -weir "$(CURDIR)/.tools/weir" -backend all -database-cpus 1 -client-processes 4 -concurrency-levels 4,8,32,128,256 -batch-sizes 1 -records 8192 -write-percent 0 -rounds 3 -warmup-duration 10s -duration 20s -output results/local/benchmark
 
diff --git a/README.md b/README.md
index 933ae5b..3c2410b 100644
--- a/README.md
+++ b/README.md
@@ -109,7 +109,7 @@ python3 -m unittest discover -s scripts -p '*_test.py'
 ```
 
 [versions.json](versions.json) pins the Weir server and database images. `go.mod`
-pins the SDK and protocol. See [CI and output](docs/ci.md) before changing a pin.
+pins the SDK and protocol. See [CI and output](docs/ci.md) for what CI runs.
 
 - Contributing: [CONTRIBUTING.md](CONTRIBUTING.md)
 - Security reports: [SECURITY.md](SECURITY.md)
diff --git a/docs/ci.md b/docs/ci.md
index 4b6fd3d..f5d993a 100644
--- a/docs/ci.md
+++ b/docs/ci.md
@@ -6,26 +6,14 @@ What CI runs, which versions it pins and where output goes.
 
 The Weir server commit and the database images are pinned in
 [versions.json](../versions.json) by full commit; `go.mod` pins released SDK and
-protocol versions without replacements. `versions.json` also names the previous
-server and SDK, which CI tests against the current other side. The tests depend
-on no server module or package.
+protocol versions without replacements. The tests depend on no server module or
+package.
 
 ## CI
 
 CI runs unit, race, vet and module-boundary checks, real multi-node integration,
 and verified ordinary and Lua comparison smoke tests on both databases, and
-uploads results and fixture logs as a workflow artifact. It also runs the
-integration tests with each side one version behind, since a server and its
-clients are not upgraded together. After `make prepare prepare-previous`, `make
-integration-previous-server` uses the current SDK with the `weir_previous_source`
-server and `make integration-previous-sdk` uses the current server with the
-`weir_go_previous` SDK and the protocol version it was released with. When pinning
-a new server or SDK, move that side's previous pin to the version it replaces; CI
-checks that each differs from the current one and that the SDK's is the release
-right before it. Both runs set the `previous` build tag: a test or helper that
-only the current versions can pass goes in a file with a `!previous` build
-constraint so that the rest keeps running, until the previous pin has that
-behaviour too.
+uploads results and fixture logs as a workflow artifact.
 
 ## Output
 
diff --git a/versions.json b/versions.json
index 1a4aee7..f2671ff 100644
--- a/versions.json
+++ b/versions.json
@@ -1,7 +1,5 @@
 {
   "weir_source": "5107986b882da60751403c7e05bbbebdb12b3cdb",
-  "weir_previous_source": "3717479d2820c8e99927d4e91f7c32298e0c32b1",
-  "weir_go_previous": "v0.24.0",
   "mongodb_version": "8.0.32",
   "mongodb_image": "mongo@sha256:d0d926f94df099bff534b7ee5b5986458131a22489dfff8664509af0c1e2ca9c",
   "elasticsearch_version": "8.19.22",