diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..7d5daf3
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,29 @@
+# deploydiff
+
+## Purpose
+Compare deployment configurations across environments. Detect drift between staging and production configs. Preview infrastructure changes with human-readable diffs, cost impact estimation, and rollback commands.
+
+## Build & Test Commands
+- Install: `pip install -e .` or `pip install deploydiff`
+- Test: `pytest tests/` (or `python -m pytest tests/ -v --tb=short`)
+- Lint: `ruff check .`
+- Build: `pip install build twine && python -m build && twine check dist/*`
+- CLI check: `deploydiff --help`
+
+## Architecture
+Key directories:
+- `src/deploydiff/` — Main package (CLI, diff engine, cost estimator, rollback generator)
+- `tests/` — Test suite
+- `.github/workflows/` — CI/CD (auto-code-review.yml, ci.yml, pages.yml, publish.yml)
+- `dist/` — Built distributions
+
+## Conventions
+- Language: Python 3.10+
+- Test framework: pytest
+- CI: GitHub Actions (auto-code-review.yml, ci.yml, pages.yml, publish.yml)
+- Linting: ruff
+- Build system: setuptools
+- Package layout: src/ layout
+- Dependencies: click, rich, pyyaml, tomli, jinja2
+- CLI entry point: deploydiff.cli:cli
+- Default branch: main
\ No newline at end of file
diff --git a/pyproject.toml b/pyproject.toml
index 17077c0..b9e59fa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -15,6 +15,8 @@ dependencies = [
     "click>=8.1",
     "rich>=13.0",
     "pyyaml>=6.0",
+    "tomli>=2.0",
+    "jinja2>=3.1",
 ]
 keywords = ["infrastructure", "terraform", "cloudformation", "pulumi", "cost", "diff", "cli"]
 classifiers = [
diff --git a/tests/conftest.py b/tests/conftest.py
index baf8023..38b2915 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,9 +1,10 @@
 """Test configuration - mock license checks so tests run without a license."""
 
-import pytest
 import sys
 from unittest.mock import MagicMock
 
+import pytest
+
 # Replace revenueholdings_license with a mock BEFORE any src imports resolve it
 _mock_rl = MagicMock()
 _mock_rl.require_license = MagicMock(return_value=None)