diff --git a/CLAUDE.md b/CLAUDE.md
index f96c8fa..1e07619 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -129,3 +129,26 @@ When editing CLAUDE.md or other markdown files, follow these rules to avoid lint
 - `LicenseClient` designed for obfuscation: all sensitive logic contained in single class
 - Symfony HttpClient works well with PSR interfaces via `symfony/http-client-contracts`
 - Keep a Changelog format allows duplicate headings per version (MD024 warning can be ignored)
+
+### 2026-01-22 - Version 0.0.2 (Security Layer)
+
+**Completed:**
+
+- Added PHPUnit ^11.0 test framework with 66 tests total
+- Implemented `SecureLicenseClient` with response signature verification
+- Created `ResponseSignature` class for HMAC-SHA256 signing/verification
+- Created `StringEncoder` for XOR-based string obfuscation
+- Created `IntegrityChecker` for source file hash verification
+- Added `SignatureException` and `IntegrityException` for security errors
+- Documented server-side implementation in `docs/server-implementation.md`
+- Merged all changes to main branch
+
+**Learnings:**
+
+- Response signature verification (HMAC) is more secure than code obfuscation alone
+- Per-license key derivation prevents cross-license signature reuse
+- Timestamp validation (5-minute tolerance) prevents replay attacks
+- Server must sign responses with matching algorithm for client verification
+- IntegrityChecker normalizes line endings for cross-platform hash consistency
+- StringEncoder uses XOR with expanded key for simple obfuscation (not encryption)
+- PHPUnit 11 uses PHP 8 attributes (`#[Test]`, `#[CoversClass]`) instead of annotations