diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91ec2e7..899fff8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,23 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.9.0] - 2026-08-14
+
+First release of the XChain Platform release train. Every component in the train
+now shares one platform version, so "XChain 0.9.0" names an exact, reproducible
+set of software rather than a rough era.
+
+### Changed
+- Adopted the platform version stream. This component moves from `1.6.12` to
+  `0.9.0`. **The number is lower but the release is newer**: the platform stream
+  starts at 0.9.0 for the testnet series, and 1.0.0 is reserved for mainnet.
+
+<!-- ------------------------------------------------------------------------
+     Versions BELOW this line are this component's own legacy stream, from
+     before the release train. They are kept for history and are NOT comparable
+     to the platform versions above: a higher legacy number is an older release.
+     ------------------------------------------------------------------------ -->
+
 ## [1.6.12] - 2026-08-13
 
 ### Fixed
diff --git a/package-lock.json b/package-lock.json
index 4d4e04e..4e6b1bd 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "xchain-encoder",
-  "version": "1.6.11",
+  "version": "0.9.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "xchain-encoder",
-      "version": "1.6.11",
+      "version": "0.9.0",
       "license": "AGPL-3.0-or-later",
       "dependencies": {
         "axios": "^1.18.1",
diff --git a/package.json b/package.json
index 15653db..acaf374 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "xchain-encoder",
   "description": "xchain-encoder encodes XChain Platform ACTION commands into blockchain transactions.",
-  "version": "1.6.12",
+  "version": "0.9.0",
   "license": "AGPL-3.0-or-later",
   "repository": {
     "type": "git",