diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index a2fe3a2bb..4f8396ea9 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -24,3 +24,23 @@ jobs:
       - name: Set up Gradle
         uses: gradle/actions/setup-gradle@d9c87d481d55275bb5441eef3fe0e46805f9ef70 # v3
       - run: ./gradlew checkWithCodenarc checkstyleMain checkstyleTest runUnitTests runLiveObjectsUnitTests :uts:runUtsUnitTests
+
+  # Continuously proves the release pre-flight and that every published module
+  # builds a publishable artifact set, so version/coordinate regressions surface
+  # on PRs rather than on release day.
+  release-dry-run:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3
+        with:
+          persist-credentials: false
+      - name: Set up the JDK
+        uses: actions/setup-java@17f84c3641ba7b8f6deff6309fc4c864478f5d62 # v3
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+      - name: Set up Gradle
+        uses: gradle/actions/setup-gradle@d9c87d481d55275bb5441eef3fe0e46805f9ef70 # v3
+      - run: ./gradlew verifyReleaseArtifacts publishToMavenLocal
diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index c55cc27a9..0266268de 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -46,6 +46,12 @@ jobs:
       - name: Set up Gradle
         uses: gradle/actions/setup-gradle@d9c87d481d55275bb5441eef3fe0e46805f9ef70 # v3
 
+      # Fails before anything is uploaded if the artifact set, group or lockstep
+      # version drifts (PDR-091b: core, core-android, device and server release
+      # together on the same version; partial release must be impossible).
+      - name: Release pre-flight
+        run: ./gradlew verifyReleaseArtifacts
+
       - name: Publish and release to Maven Central
         run: ./gradlew publishAndReleaseToMavenCentral
         env:
diff --git a/README.md b/README.md
index a16465305..2a0449358 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,23 @@ Find out more:
 
 ---
 
+> [!NOTE]
+> **This branch carries the in-development 2.0 device/server package split.** The SDK is being
+> restructured into new artifacts that declare which side of the network they run on, so that
+> traffic classifies correctly on MAU-priced accounts:
+>
+> | Artifact | For | Entry point |
+> |----------|-----|-------------|
+> | `io.ably.pubsub:device` (aar) | Devices: Android apps and other end-user runtimes | `PubSubDevice.clientBuilder(...)` |
+> | `io.ably.pubsub:server` (jar) | Servers and other trusted backend environments | `PubSubServer.httpClientBuilder(...)` / `PubSubServer.realtimeClientBuilder(...)` |
+> | `io.ably.pubsub:core`, `io.ably.pubsub:core-android` | Internal implementation artifacts — do not depend on these directly | — |
+>
+> Nothing from this branch is published yet. The `io.ably:ably-java` and `io.ably:ably-android`
+> 1.x artifacts continue to work and will receive security and critical fixes from a maintenance
+> branch for one year after the 2.0 release. The installation instructions below still describe 1.x.
+
+---
+
 ## Getting started
 
 Everything you need to get started with Ably:
diff --git a/build.gradle.kts b/build.gradle.kts
index a98b165b6..6921a8130 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -30,6 +30,56 @@ subprojects {
     }
 }
 
+/*
+ * Release pre-flight: the split ships core, core-android, device and server in lockstep
+ * (one version, one run — PDR-091b), so the set of published artifacts and their
+ * coordinates are asserted here and the release workflow fails before anything is
+ * uploaded if they drift. If you add or remove a published module, update this list
+ * deliberately.
+ */
+val expectedReleaseArtifacts = sortedSetOf(
+    "io.ably.pubsub:core:jar",
+    "io.ably.pubsub:core-android:aar",
+    "io.ably.pubsub:device:aar",
+    "io.ably.pubsub:server:jar",
+    "io.ably.pubsub:liveobjects:jar",
+    "io.ably.pubsub:pubsub-adapter:jar",
+    "io.ably.pubsub:network-client-core:jar",
+    "io.ably.pubsub:network-client-default:jar",
+    "io.ably.pubsub:network-client-okhttp:jar",
+)
+
+tasks.register("verifyReleaseArtifacts") {
+    description = "Asserts the published artifact set, group and lockstep version before a release."
+    doLast {
+        val rootVersion = project.property("VERSION_NAME") as String
+        val actual = sortedSetOf<String>()
+        subprojects.filter { it.pluginManager.hasPlugin("com.vanniktech.maven.publish") }.forEach { p ->
+            val artifactId = p.findProperty("POM_ARTIFACT_ID")
+                ?: error("${p.path} applies maven-publish but has no POM_ARTIFACT_ID")
+            val packaging = p.findProperty("POM_PACKAGING") ?: "jar"
+            // The version each module publishes at comes from its effective VERSION_NAME
+            // (a module-local gradle.properties can override the root's — exactly the
+            // lockstep drift this guards against).
+            val moduleVersion = p.findProperty("VERSION_NAME")
+            if (moduleVersion != rootVersion) {
+                error("Lockstep violation: ${p.path} has VERSION_NAME $moduleVersion, expected $rootVersion")
+            }
+            val group = p.findProperty("GROUP")
+            actual.add("$group:$artifactId:$packaging")
+        }
+        if (actual != expectedReleaseArtifacts) {
+            error(
+                "Published artifact set does not match the expected release set.\n" +
+                    "  expected: $expectedReleaseArtifacts\n" +
+                    "  actual:   $actual\n" +
+                    "If this change is deliberate, update expectedReleaseArtifacts in build.gradle.kts."
+            )
+        }
+        logger.lifecycle("Release pre-flight OK: ${actual.size} artifacts at $rootVersion: $actual")
+    }
+}
+
 configure(subprojects) {
     pluginManager.withPlugin("com.vanniktech.maven.publish") {
         extensions.configure<MavenPublishBaseExtension> {