diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2c26ee..2258647 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.5.0] - 2026-02-16
+
 ### Changed
 
 #### Spec Serialization Compliance
@@ -17,7 +19,24 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **Breaking:** `Block::block_type()` returns `Cow<'_, str>` instead of `&'static str`; extension blocks return `"namespace:blockType"` instead of `"extension"`
 - `FigCaption` block type serializes as `"figcaption"` (lowercase) instead of `"figCaption"`
 - All old formats are accepted on deserialization for backward compatibility
-- Added conformance test suite (`tests/conformance.rs`) to prevent future spec drift
+
+#### CLI Restructuring
+- Split `cdx-cli/src/main.rs` into `cli.rs` (argument definitions), `dispatcher.rs` (command dispatch), and `main.rs` (entry point)
+
+### Added
+
+#### Spec Conformance Testing
+- Conformance test suite (`tests/conformance.rs`) covering all 78 testable spec requirements
+- Conformance matrix (`docs/conformance-matrix.md`) mapping spec sections to tests — 78/79 PASS, 0 TODO
+- Hash boundary tests verifying document ID includes/excludes correct fields
+- Asset embedding tests: hash verification, missing file detection, hash mismatch errors
+- State machine enforcement tests for review/frozen/published requirements
+- Provenance/lineage validation tests
+- Property-based tests using proptest for hash determinism, metadata inclusion, block round-trips
+- Fuzz targets for Block, Mark, and Content deserialization (`fuzz/fuzz_targets/`)
+
+#### Security Policy
+- Added `SECURITY.md` with supported versions and vulnerability reporting process
 
 ## [0.4.0] - 2026-02-16
 
@@ -257,7 +276,8 @@ Initial release implementing Codex Document Format Specification v0.1.
 - `sign_document` - Sign a document with ES256
 - `extract_content` - Extract text content from blocks
 
-[Unreleased]: https://github.com/Entrolution/cdx-core/compare/v0.4.0...HEAD
+[Unreleased]: https://github.com/Entrolution/cdx-core/compare/v0.5.0...HEAD
+[0.5.0]: https://github.com/Entrolution/cdx-core/compare/v0.4.0...v0.5.0
 [0.4.0]: https://github.com/Entrolution/cdx-core/compare/v0.3.0...v0.4.0
 [0.3.0]: https://github.com/Entrolution/cdx-core/compare/v0.2.0...v0.3.0
 [0.2.0]: https://github.com/Entrolution/cdx-core/compare/v0.1.0...v0.2.0
diff --git a/Cargo.toml b/Cargo.toml
index f5864e4..9e0dfc8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,4 +17,4 @@ thiserror = "2.0"
 chrono = { version = "0.4", features = ["serde", "now"], default-features = false }
 
 # Internal crates
-cdx-core = { path = "cdx-core", version = "0.4.0" }
+cdx-core = { path = "cdx-core", version = "0.5.0" }
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..47cb64b
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,28 @@
+# Security Policy
+
+## Supported Versions
+
+| Version | Supported |
+|---------|-----------|
+| 0.5.x   | Yes       |
+| < 0.5   | No        |
+
+Only the latest minor release receives security updates. Earlier versions are not supported.
+
+## Reporting a Vulnerability
+
+If you discover a security vulnerability, please report it responsibly:
+
+1. **Do not** open a public GitHub issue.
+2. Email **security@entrolution.com** with details of the vulnerability.
+3. Include steps to reproduce, if possible.
+
+We aim to acknowledge reports within 48 hours and provide a fix or mitigation within 7 days for critical issues.
+
+## Security Practices
+
+- All cryptographic operations use well-audited Rust crates (`sha2`, `p256`, `aes-gcm`, `ed25519-dalek`).
+- Archive extraction is bounded to prevent decompression bombs (256 MiB limit).
+- Path traversal attacks are rejected at the archive reader/writer level.
+- Document integrity is verified via SHA-256 content hashes and JCS-canonicalized document IDs.
+- Spec conformance is validated by 1,000+ tests covering all 78 testable requirements.
diff --git a/cdx-cli/Cargo.toml b/cdx-cli/Cargo.toml
index 041a821..c030887 100644
--- a/cdx-cli/Cargo.toml
+++ b/cdx-cli/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cdx-cli"
-version = "0.4.0"
+version = "0.5.0"
 edition.workspace = true
 rust-version.workspace = true
 license.workspace = true
diff --git a/cdx-core/Cargo.toml b/cdx-core/Cargo.toml
index 563c4c7..0d7cff8 100644
--- a/cdx-core/Cargo.toml
+++ b/cdx-core/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cdx-core"
-version = "0.4.0"
+version = "0.5.0"
 edition.workspace = true
 rust-version.workspace = true
 license.workspace = true