diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..7b0c259
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,28 @@
+# Changelog
+
+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).
+
+## [Unreleased]
+
+## [1.0.0] - 2026-03-22
+
+### Added
+- Production-ready Slack incident management bot
+- Orphaned incident recovery and incident templates
+- Lean dev workflow and cleanup commands
+
+### Fixed
+- All deferred code review issues
+- Incident bot hardened for release readiness
+- Docker build: updated Rust image and installed openssl build deps
+- Repaired main CI checks
+
+### Changed
+- Bootstrapped codex OS guardrails
+- Removed obsolete phase tracking files
+- Updated passing test counts and status documentation
+- Enabled QEMU for multi-arch Docker builds
+- Targeted current x64 image lane in CI