diff --git a/.github/workflows/apple-ipad-post-deployment-smoke.yml b/.github/workflows/apple-ipad-post-deployment-smoke.yml
index 2ab788d..daf8b1a 100644
--- a/.github/workflows/apple-ipad-post-deployment-smoke.yml
+++ b/.github/workflows/apple-ipad-post-deployment-smoke.yml
@@ -43,7 +43,7 @@ jobs:
           test "$(jq -r '.deployment_result' "$evidence")" = DEPLOYED_PENDING_SMOKE
           manifest="$(mktemp)"
           trap 'rm -f "$manifest" ipad-apps.json' EXIT
-          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json --output "$manifest"
+          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
             APPROVED_DEPLOYMENT_DISPATCH_PENDING|APPROVED_PARTIAL_DEPLOYMENT_OPERATIONAL) ;;
diff --git a/.github/workflows/apple-ipad-secure-distribution-relay.yml b/.github/workflows/apple-ipad-secure-distribution-relay.yml
index dae40bf..92088f2 100644
--- a/.github/workflows/apple-ipad-secure-distribution-relay.yml
+++ b/.github/workflows/apple-ipad-secure-distribution-relay.yml
@@ -40,7 +40,7 @@ jobs:
           printf '%s' "$PLATFORM_VERSION" | grep -Eq '^[0-9]+\.[0-9]+$'
           manifest="$(mktemp)"
           trap 'rm -f "$manifest"' EXIT
-          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json --output "$manifest"
+          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
             APPROVED_DEPLOYMENT_DISPATCH_PENDING|APPROVED_PARTIAL_DEPLOYMENT_OPERATIONAL) ;;
@@ -49,7 +49,7 @@ jobs:
           test "$(jq -r '.approval.state' "$manifest")" = APPROVED
           test "$(jq -r '.manifest_id' "$manifest")" = "$MANIFEST_ID"
           test "$(jq -r '.release_profile' "$manifest")" = "$RELEASE_PROFILE"
-          release_version="$(jq -r --arg sha "$CANDIDATE_SHA" '.repositories[] | select(.repository == "pcvantol/djconnect-app" and .source_sha == $sha and .version == "3.3.0") | .version' "$manifest")"
+          release_version="$(jq -r --arg sha "$CANDIDATE_SHA" '.repositories[] | select(.repository == "pcvantol/djconnect-app" and .source_sha == $sha and .version == "4.0.0") | .version' "$manifest")"
           printf '%s' "$release_version" | grep -Eq '^[0-9]+\.[0-9]+\.[0-9]+$'
           test "$ARTIFACT_ID" = "release-asset:pcvantol/djconnect-app-releases:ios/v${release_version}:DJConnect-iOS-${release_version}-unsigned.zip"
           binding="$(jq -cer --arg artifact "$ARTIFACT_ID" --arg checksum "$ARTIFACT_SHA256" '.artifact_bindings[] | select(.target == "apple_private_device" and .target_device == "ipad" and .artifact_id == $artifact and .artifact_sha256 == $checksum and .signing == "local_developer_provisioning_required" and (has("paired_watch_validation") | not))' "$manifest")"
diff --git a/.github/workflows/apple-iphone-post-deployment-smoke.yml b/.github/workflows/apple-iphone-post-deployment-smoke.yml
index fe619c3..da9cb52 100644
--- a/.github/workflows/apple-iphone-post-deployment-smoke.yml
+++ b/.github/workflows/apple-iphone-post-deployment-smoke.yml
@@ -43,7 +43,7 @@ jobs:
           test "$(jq -r '.deployment_result' "$evidence")" = DEPLOYED_PENDING_SMOKE
           manifest="$(mktemp)"
           trap 'rm -f "$manifest" iphone-apps.json watch-apps.json' EXIT
-          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json --output "$manifest"
+          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
             APPROVED_DEPLOYMENT_DISPATCH_PENDING|APPROVED_PARTIAL_DEPLOYMENT_OPERATIONAL) ;;
diff --git a/.github/workflows/apple-iphone-secure-distribution-relay.yml b/.github/workflows/apple-iphone-secure-distribution-relay.yml
index dbfaa7e..25b6940 100644
--- a/.github/workflows/apple-iphone-secure-distribution-relay.yml
+++ b/.github/workflows/apple-iphone-secure-distribution-relay.yml
@@ -41,7 +41,7 @@ jobs:
           printf '%s' "$PLATFORM_VERSION" | grep -Eq '^[0-9]+\.[0-9]+$'
           manifest="$(mktemp)"
           trap 'rm -f "$manifest"' EXIT
-          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json --output "$manifest"
+          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
             APPROVED_DEPLOYMENT_DISPATCH_PENDING|APPROVED_PARTIAL_DEPLOYMENT_OPERATIONAL) ;;
@@ -50,7 +50,7 @@ jobs:
           test "$(jq -r '.approval.state' "$manifest")" = APPROVED
           test "$(jq -r '.manifest_id' "$manifest")" = "$MANIFEST_ID"
           test "$(jq -r '.release_profile' "$manifest")" = "$RELEASE_PROFILE"
-          jq -e --arg sha "$CANDIDATE_SHA" '.repositories[] | select(.repository == "pcvantol/djconnect-app" and .source_sha == $sha and .version == "3.3.0")' "$manifest" >/dev/null
+          jq -e --arg sha "$CANDIDATE_SHA" '.repositories[] | select(.repository == "pcvantol/djconnect-app" and .source_sha == $sha and .version == "4.0.0")' "$manifest" >/dev/null
           binding="$(jq -cer --arg artifact "$ARTIFACT_ID" --arg checksum "$ARTIFACT_SHA256" '.artifact_bindings[] | select(.target == "apple_private_device" and .target_device == "iphone" and .paired_watch_validation == "required" and .artifact_id == $artifact and .artifact_sha256 == $checksum and .signing == "local_developer_provisioning_required")' "$manifest")"
           printf 'artifact_url=%s\n' "$(jq -r '.artifact_url' <<<"$binding")" >> "$GITHUB_OUTPUT"
       - name: Verify exact physical iPhone, paired Watch and local signing scope
diff --git a/.github/workflows/apple-post-deployment-smoke.yml b/.github/workflows/apple-post-deployment-smoke.yml
index 4d89fa4..b715d11 100644
--- a/.github/workflows/apple-post-deployment-smoke.yml
+++ b/.github/workflows/apple-post-deployment-smoke.yml
@@ -61,7 +61,7 @@ jobs:
           set -euo pipefail
           manifest="$(mktemp)"
           trap 'rm -f "$manifest"' EXIT
-          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json --output "$manifest"
+          curl --fail --silent --show-error --location https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
             APPROVED_DEPLOYMENT_DISPATCH_PENDING|APPROVED_PARTIAL_DEPLOYMENT_OPERATIONAL) ;;
diff --git a/.github/workflows/apple-secure-distribution-relay.yml b/.github/workflows/apple-secure-distribution-relay.yml
index 82f520a..c110e8e 100644
--- a/.github/workflows/apple-secure-distribution-relay.yml
+++ b/.github/workflows/apple-secure-distribution-relay.yml
@@ -65,7 +65,7 @@ jobs:
           manifest="$(mktemp)"
           trap 'rm -f "$manifest"' EXIT
           curl --fail --silent --show-error --location \
-            https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_3_3_CURRENT_MAIN_MANIFEST_PROPOSAL.json \
+            https://raw.githubusercontent.com/pcvantol/djconnect/main/docs/release/PLATFORM_4_0_RC1_APPLE_OPERATIONAL_MANIFEST.json \
             --output "$manifest"
           manifest_status="$(jq -r '.status' "$manifest")"
           case "$manifest_status" in
diff --git a/Apps/DJConnectWatch/DJConnectWatchModel.swift b/Apps/DJConnectWatch/DJConnectWatchModel.swift
index fcadddc..ea5f19e 100644
--- a/Apps/DJConnectWatch/DJConnectWatchModel.swift
+++ b/Apps/DJConnectWatch/DJConnectWatchModel.swift
@@ -517,7 +517,7 @@ final class DJConnectWatchModel: NSObject, ObservableObject {
                 sendCompanionPairingRegistration()
             }
         }
-        appendDiagnosticLog("Version metadata: release_version=\(DJConnectApplicationVersion.releaseVersion); build_version=\(DJConnectApplicationVersion.buildVersion); protocol_version=\(DJConnectProtocolVersion.current)")
+        appendDiagnosticLog("Version metadata: release_version=\(DJConnectApplicationVersion.releaseVersion); public_release=\(DJConnectApplicationVersion.publicReleaseIdentity); build_version=\(DJConnectApplicationVersion.buildVersion); protocol_version=\(DJConnectProtocolVersion.current)")
         if !isDemoMode {
             startNetworkMonitor()
         }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c699ae6..d2d2c81 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,15 @@ All notable changes to DJConnect App are documented here.
 
 ## Unreleased
 
+## 4.0.0-rc.1 - 2026-08-06
+
+### Changed
+
+- Prepare the native Apple `4.0.0` / build `40001` package for the Platform
+  `4.0.0-rc.1` candidate and report the RC identity in diagnostics.
+- Move the Apple runtime protocol contract to `4.0.0-rc.1`, which enforces the
+  shared `4.0` compatibility line with Home Assistant.
+
 ## 3.2.35 - 2026-07-09
 
 ### Fixed
diff --git a/DJConnectApp.xcodeproj/project.pbxproj b/DJConnectApp.xcodeproj/project.pbxproj
index 2bd5d41..32ab778 100644
--- a/DJConnectApp.xcodeproj/project.pbxproj
+++ b/DJConnectApp.xcodeproj/project.pbxproj
@@ -1749,7 +1749,7 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				CODE_SIGN_STYLE = Automatic;
 				COPY_PHASE_STRIP = NO;
-				CURRENT_PROJECT_VERSION = 1;
+				CURRENT_PROJECT_VERSION = 40001;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEVELOPMENT_TEAM = "";
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
@@ -1770,7 +1770,7 @@
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				MACOSX_DEPLOYMENT_TARGET = 26.0;
-				MARKETING_VERSION = 3.3.0;
+				MARKETING_VERSION = 4.0.0;
 				MTL_ENABLE_DEBUG_INFO = INCLUDE_SOURCE;
 				MTL_FAST_MATH = YES;
 				ONLY_ACTIVE_ARCH = YES;
@@ -1898,7 +1898,7 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				CODE_SIGN_STYLE = Automatic;
 				COPY_PHASE_STRIP = NO;
-				CURRENT_PROJECT_VERSION = 1;
+				CURRENT_PROJECT_VERSION = 40001;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEVELOPMENT_TEAM = "";
 				ENABLE_NS_ASSERTIONS = NO;
@@ -1913,7 +1913,7 @@
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				MACOSX_DEPLOYMENT_TARGET = 26.0;
-				MARKETING_VERSION = 3.3.0;
+				MARKETING_VERSION = 4.0.0;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				MTL_FAST_MATH = YES;
 				PRODUCT_NAME = "$(TARGET_NAME)";
diff --git a/README.md b/README.md
index 8025c8f..9a3d61f 100644
--- a/README.md
+++ b/README.md
@@ -607,7 +607,7 @@ must keep pairing and token state, show an update-required state, and pause
 command/voice retries until the app or integration is updated.
 
 Successful status and command responses may also include `ha_version` or
-`ha_major_minor`. App `3.2.x` requires HA integration `3.2.x` and disables
+`ha_major_minor`. App `4.0.x` requires HA integration `4.0.x` and disables
 playback, queue, playlist, output, liked, and voice controls when the runtime
 contract is outside that range. Settings and pairing reset remain available.
 
diff --git a/Sources/DJConnectCore/DJConnectModels.swift b/Sources/DJConnectCore/DJConnectModels.swift
index 656b284..147bb54 100644
--- a/Sources/DJConnectCore/DJConnectModels.swift
+++ b/Sources/DJConnectCore/DJConnectModels.swift
@@ -1,6 +1,9 @@
 import Foundation
 
 public enum DJConnectApplicationVersion {
+    /// Public cross-platform identity for the native numeric 4.0.0 / 40001 package.
+    public static let publicReleaseIdentity = "4.0.0-rc.1"
+
     public static var releaseVersion: String {
         bundleValue(for: "CFBundleShortVersionString")
     }
@@ -20,7 +23,7 @@ public enum DJConnectApplicationVersion {
 }
 
 public enum DJConnectProtocolVersion {
-    public static let current = "3.2.33"
+    public static let current = "4.0.0-rc.1"
 }
 
 public enum DJConnectClientType: String, Codable, Sendable {
diff --git a/Tests/DJConnectCoreTests/DJConnectCoreTests.swift b/Tests/DJConnectCoreTests/DJConnectCoreTests.swift
index e105edb..a2eff20 100644
--- a/Tests/DJConnectCoreTests/DJConnectCoreTests.swift
+++ b/Tests/DJConnectCoreTests/DJConnectCoreTests.swift
@@ -1151,6 +1151,11 @@ private func makePairedMusicDNAModel(
     #expect(watchAboutSource.contains("DJConnectApplicationVersion.releaseVersion"))
 }
 
+@Test func platformFourReleaseCandidateUsesNativePackageAndPublicProtocolMapping() {
+    #expect(DJConnectApplicationVersion.publicReleaseIdentity == "4.0.0-rc.1")
+    #expect(DJConnectProtocolVersion.current == "4.0.0-rc.1")
+}
+
 @Test func homeAssistantClientRoutesUseCanonicalV1Prefix() throws {
     let checkedRoots = ["Sources", "Apps"]
     let legacyRoutes = [
@@ -10303,9 +10308,9 @@ private func makePairedMusicDNAModel(
     ))
 
     let updateMessage = try #require(model.updateRequiredMessage)
-    #expect(updateMessage.contains("3.2.x"))
-    #expect(updateMessage.contains(">=3.2.0"))
-    #expect(updateMessage.contains("<3.3.0"))
+    #expect(updateMessage.contains("4.0.x"))
+    #expect(updateMessage.contains(">=4.0.0"))
+    #expect(updateMessage.contains("<4.1.0"))
     #expect(model.canUsePlaybackFeatures == false)
     #expect(model.backendAvailable == false)
     #expect(model.playback == nil)
@@ -10327,7 +10332,7 @@ private func makePairedMusicDNAModel(
     model.apply(commandResponse: DJConnectCommandResponse(
         success: true,
         backendAvailable: true,
-        haVersion: "3.2.99",
+        haVersion: "4.0.99",
         playback: DJConnectPlayback(trackName: "Compatible Track")
     ))
     model.apply(musicBackendSummary: DJConnectMusicBackendSummary(remoteSupported: true))
diff --git a/docs/HANDOFF.md b/docs/HANDOFF.md
index 3dfa6ab..a30d512 100644
--- a/docs/HANDOFF.md
+++ b/docs/HANDOFF.md
@@ -279,7 +279,7 @@ protocol version:
 
 - HA `3.0.z` accepts clients `3.0.z`.
 - HA `3.1.z` accepts clients `3.1.z`.
-- HA `3.2.z` accepts clients `3.2.z`.
+- HA `4.0.z` accepts clients `4.0.z`.
 - Patch versions may differ.
 - `0.0.0` is reserved as a dev-client escape hatch.
 
@@ -288,8 +288,8 @@ reset pairing or discard the token. Show an update-required state and pause
 command/voice retries until the user updates the app or integration.
 
 The Apple app also validates `ha_version` / `ha_major_minor` fields on normal
-status and command responses. App `3.2.x` requires HA integration `3.2.x`
-(`>=3.2.0`, `<3.3.0`). If HA is outside that range, the app must show a clear
+status and command responses. App `4.0.x` requires HA integration `4.0.x`
+(`>=4.0.0`, `<4.1.0`). If HA is outside that range, the app must show a clear
 message to update the Home Assistant integration, disable playback/output/
 queue/playlist/liked/voice controls, and keep Settings plus pairing reset
 available.
diff --git a/docs/RELEASE.md b/docs/RELEASE.md
index 737cdde..a13e3df 100644
--- a/docs/RELEASE.md
+++ b/docs/RELEASE.md
@@ -68,8 +68,10 @@ After renewing the Apple Developer Program membership:
   Local Network, Microphone, Speech Recognition.
 - Confirm app icons, launch screen, welcome screen, About screen, and website
   link match the current DJConnect branding.
-- Confirm the HA integration compatibility line is documented:
-  app `3.2.x` requires HA integration `3.2.x`.
+- Confirm the HA integration compatibility line is documented. For this
+  candidate, Apple clients and HA integration use the shared `4.0` line; the
+  native Apple package remains numeric `4.0.0` while the platform identity is
+  `4.0.0-rc.1`.
 - Confirm the public macOS release helper works in dry/local mode before the
   first public binary release.
 
diff --git a/docs/release-notes/de/v4.0.0.md b/docs/release-notes/de/v4.0.0.md
new file mode 100644
index 0000000..4b4071c
--- /dev/null
+++ b/docs/release-notes/de/v4.0.0.md
@@ -0,0 +1,9 @@
+# DJConnect App 4.0.0 RC 1
+
+## Geändert
+
+- Dieser interne Release Candidate bringt die Clients für iPhone, iPad und
+  Apple Watch auf die gemeinsame DJConnect-4.0-Kompatibilitätslinie.
+- Der Bereitstellungsweg für private Geräte prüft jetzt das spezielle
+  Betriebsmanifest für Platform 4.0, bevor ein freigegebener Build installiert wird.
+
diff --git a/docs/release-notes/en/v4.0.0.md b/docs/release-notes/en/v4.0.0.md
new file mode 100644
index 0000000..f228610
--- /dev/null
+++ b/docs/release-notes/en/v4.0.0.md
@@ -0,0 +1,9 @@
+# DJConnect App 4.0.0 RC 1
+
+## Changed
+
+- This internal release candidate moves the iPhone, iPad, and Apple Watch
+  clients to the shared DJConnect 4.0 compatibility line.
+- The private-device deployment route now validates the dedicated Platform 4.0
+  operational manifest before it installs an approved build.
+
diff --git a/docs/release-notes/es/v4.0.0.md b/docs/release-notes/es/v4.0.0.md
new file mode 100644
index 0000000..e983982
--- /dev/null
+++ b/docs/release-notes/es/v4.0.0.md
@@ -0,0 +1,9 @@
+# DJConnect App 4.0.0 RC 1
+
+## Cambiado
+
+- Esta versión candidata interna lleva los clientes de iPhone, iPad y Apple
+  Watch a la línea de compatibilidad compartida de DJConnect 4.0.
+- La ruta de despliegue para dispositivos privados ahora valida el manifiesto
+  operativo específico de Platform 4.0 antes de instalar una compilación aprobada.
+
diff --git a/docs/release-notes/fr/v4.0.0.md b/docs/release-notes/fr/v4.0.0.md
new file mode 100644
index 0000000..5013380
--- /dev/null
+++ b/docs/release-notes/fr/v4.0.0.md
@@ -0,0 +1,9 @@
+# DJConnect App 4.0.0 RC 1
+
+## Modifié
+
+- Cette version candidate interne aligne les clients iPhone, iPad et Apple
+  Watch sur la ligne de compatibilité partagée DJConnect 4.0.
+- Le parcours de déploiement sur appareil privé vérifie désormais le manifeste
+  opérationnel dédié à Platform 4.0 avant d’installer une build approuvée.
+
diff --git a/docs/release-notes/nl/v4.0.0.md b/docs/release-notes/nl/v4.0.0.md
new file mode 100644
index 0000000..ba13307
--- /dev/null
+++ b/docs/release-notes/nl/v4.0.0.md
@@ -0,0 +1,9 @@
+# DJConnect App 4.0.0 RC 1
+
+## Gewijzigd
+
+- Deze interne release candidate brengt de iPhone-, iPad- en Apple
+  Watch-clients naar de gedeelde DJConnect 4.0-compatibiliteitslijn.
+- De private-device-uitrol controleert nu het specifieke Platform
+  4.0-operationele manifest vóór een goedgekeurde build wordt geïnstalleerd.
+
diff --git a/project.yml b/project.yml
index 490953b..535ddac 100644
--- a/project.yml
+++ b/project.yml
@@ -10,8 +10,8 @@ options:
 settings:
   base:
     SWIFT_VERSION: "6.0"
-    CURRENT_PROJECT_VERSION: "1"
-    MARKETING_VERSION: "3.3.0"
+    CURRENT_PROJECT_VERSION: "40001"
+    MARKETING_VERSION: "4.0.0"
     DEVELOPMENT_TEAM: ""
     CODE_SIGN_STYLE: Automatic
 packages: {}