diff --git a/CLAUDE.md b/AGENTS.md
similarity index 60%
rename from CLAUDE.md
rename to AGENTS.md
index 56d4366..8c823cc 100644
--- a/CLAUDE.md
+++ b/AGENTS.md
@@ -36,6 +36,18 @@ When your changes create orphans:
 
 The test: Every changed line should trace directly to the user's request.
 
+## Test-Driven Development
+
+**Red, green, refactor — never write implementation code first.**
+
+1. **Red** — write a failing test that captures the desired behaviour. Run it and confirm it fails for the right reason.
+2. **Green** — write the minimum code needed to make that test pass. Run the test and confirm it passes.
+3. **Refactor** — clean up while keeping all tests green. Re-run the full test suite after every step.
+
+- No production code without a failing test that demands it.
+- If a test passes on the first run, verify it actually exercises the new behaviour — it may be a false green.
+- Run the full suite (`dotnet test`) before declaring any task done.
+
 ## Goal-Driven Execution
 
 **Define success criteria. Loop until verified.**
@@ -57,3 +69,16 @@ For multi-step tasks, state a brief plan:
 ```
 
 Strong success criteria let you loop independently. Weak criteria ("make it work") require constant clarification.
+
+## Keep the Regression Test Cases Up to Date
+
+**Every code change must be reflected in `RegressionTests.md`.**
+
+After making any change — new feature, behaviour change, bug fix, or removed functionality — update `RegressionTests.md` before considering the task done:
+
+- Add a new case (following the existing `<AREA>-NN` ID and table format) for any new or changed user-visible behaviour.
+- Amend the relevant existing case when behaviour changes.
+- Remove or mark obsolete any case that no longer applies.
+- Keep the Contents list in sync when a whole section is added or removed.
+
+If a change genuinely affects no manual test case, say so explicitly instead of silently skipping this step.