diff --git a/.github/fetch_version.py b/.github/fetch_version.py
index 7f394b76..05793d11 100644
--- a/.github/fetch_version.py
+++ b/.github/fetch_version.py
@@ -1,8 +1,8 @@
 def fetch_version():
     try:
-        import importlib
+        from importlib.metadata import version
 
-        return importlib.import_module("policyengine").__version__
+        return version("policyengine")
     except Exception as e:
         print(f"Error fetching version: {e}")
         return None
diff --git a/.github/workflows/code_changes.yaml b/.github/workflows/code_changes.yaml
index c18b527c..cd64a7ef 100644
--- a/.github/workflows/code_changes.yaml
+++ b/.github/workflows/code_changes.yaml
@@ -26,6 +26,9 @@ jobs:
 
         - name: Run ruff check
           run: ruff check .
+
+        - name: Run ruff format check
+          run: ruff format --check .
   Test:
       runs-on: macos-latest
       permissions:
diff --git a/.github/workflows/pr_code_changes.yaml b/.github/workflows/pr_code_changes.yaml
index 8ca3092b..a2cc1192 100644
--- a/.github/workflows/pr_code_changes.yaml
+++ b/.github/workflows/pr_code_changes.yaml
@@ -23,6 +23,20 @@ jobs:
 
         - name: Run ruff check
           run: ruff check .
+  Mypy:
+    runs-on: ubuntu-latest
+    steps:
+        - uses: actions/checkout@v4
+        - name: Install uv
+          uses: astral-sh/setup-uv@v5
+        - name: Set up Python
+          uses: actions/setup-python@v5
+          with:
+              python-version: '3.13'
+        - name: Install package
+          run: uv pip install -e .[dev] --system
+        - name: Run mypy (informational)
+          run: mypy src/policyengine || echo "::warning::mypy found errors (non-blocking until codebase is clean)"
   Test:
     runs-on: macos-latest
     strategy:
diff --git a/.github/workflows/versioning.yaml b/.github/workflows/versioning.yaml
index a30a0e47..dcb70429 100644
--- a/.github/workflows/versioning.yaml
+++ b/.github/workflows/versioning.yaml
@@ -7,7 +7,7 @@ on:
       - main
 
     paths:
-      - changelog_entry.yaml
+      - changelog.d/**
       - .github/**
   workflow_dispatch:
 
@@ -27,7 +27,7 @@ jobs:
         with:
           python-version: 3.13
       - name: Build changelog
-        run: pip install yaml-changelog && make changelog
+        run: pip install yaml-changelog towncrier && make changelog
       - name: Preview changelog update
         run: ".github/get-changelog-diff.sh"
       - name: Update changelog
@@ -66,3 +66,10 @@ jobs:
           user: __token__
           password: ${{ secrets.PYPI }}
           skip_existing: true
+      - name: Create GitHub Release
+        run: |
+          VERSION=$(python .github/fetch_version.py)
+          gh release create "$VERSION" \
+            --title "v$VERSION" \
+            --notes "See [CHANGELOG.md](https://github.com/PolicyEngine/policyengine.py/blob/main/CHANGELOG.md) for details." \
+            --latest
diff --git a/Makefile b/Makefile
index b54164f4..f5028d39 100644
--- a/Makefile
+++ b/Makefile
@@ -27,4 +27,4 @@ build-package:
 	python -m build
 
 test:
-	pytest tests
\ No newline at end of file
+	pytest tests --cov=policyengine --cov-report=term-missing
\ No newline at end of file
diff --git a/README.md b/README.md
index 8c89c37f..8d1cf2c2 100644
--- a/README.md
+++ b/README.md
@@ -48,10 +48,94 @@ print(f"Total UC spending: £{agg.result / 1e9:.1f}bn")
 
 ## Installation
 
+### As a library
+
 ```bash
 pip install policyengine
 ```
 
+This installs both UK and US country models. To install only one:
+
+```bash
+pip install policyengine[uk]    # UK model only
+pip install policyengine[us]    # US model only
+```
+
+### For development
+
+```bash
+git clone https://github.com/PolicyEngine/policyengine.py.git
+cd policyengine.py
+uv pip install -e .[dev]        # install with dev dependencies (pytest, ruff, mypy, etc.)
+```
+
+## Development
+
+### Running configurations
+
+| Configuration | Install | Use case |
+|---------------|---------|----------|
+| **Library user** | `pip install policyengine` | Using the package in your own code |
+| **UK only** | `pip install policyengine[uk]` | Only need UK simulations |
+| **US only** | `pip install policyengine[us]` | Only need US simulations |
+| **Developer** | `uv pip install -e .[dev]` | Contributing to the package |
+
+### Common commands
+
+```bash
+make format           # ruff format
+make test             # pytest with coverage
+make docs             # build Jupyter Book documentation
+make clean            # remove caches, build artifacts, .h5 files
+```
+
+### Testing
+
+Tests require a `HUGGING_FACE_TOKEN` environment variable for downloading datasets:
+
+```bash
+export HUGGING_FACE_TOKEN=hf_...
+make test
+```
+
+To run a specific test:
+
+```bash
+pytest tests/test_models.py -v
+pytest tests/test_parametric_reforms.py -k "test_uk" -v
+```
+
+### Linting and type checking
+
+```bash
+ruff format .                    # format code
+ruff check .                     # lint
+mypy src/policyengine            # type check (informational — not yet enforced in CI)
+```
+
+### CI pipeline
+
+PRs trigger the following checks:
+
+| Check | Status | Command |
+|-------|--------|---------|
+| Lint + format | Required | `ruff check .` + `ruff format --check .` |
+| Tests (Python 3.13) | Required | `make test` |
+| Tests (Python 3.14) | Required | `make test` |
+| Mypy | Informational | `mypy src/policyengine` |
+| Docs build | Required | Jupyter Book build |
+
+### Versioning and releases
+
+This project uses [towncrier](https://towncrier.readthedocs.io/) for changelog management. When making a PR, add a changelog fragment:
+
+```bash
+# Fragment types: breaking, added, changed, fixed, removed
+echo "Description of change" > changelog.d/my-change.added
+```
+
+On merge, the versioning workflow bumps the version, builds the changelog, and creates a GitHub Release.
+
 ## Features
 
 - **Multi-country support**: UK and US tax-benefit systems
diff --git a/pyproject.toml b/pyproject.toml
index fadcc314..fc3dffe6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -46,8 +46,10 @@ dev = [
     "ruff>=0.9.0",
     "policyengine_core>=3.23.6",
     "policyengine-uk>=2.51.0",
-    "policyengine-us>=1.213.1",    "towncrier>=24.8.0",
-
+    "policyengine-us>=1.213.1",
+    "towncrier>=24.8.0",
+    "mypy>=1.11.0",
+    "pytest-cov>=5.0.0",
 ]
 
 [tool.setuptools]
@@ -90,6 +92,12 @@ indent-style = "space"
 skip-magic-trailing-comma = false
 line-ending = "auto"
 
+[tool.mypy]
+python_version = "3.13"
+warn_return_any = true
+warn_unused_configs = true
+ignore_missing_imports = true
+
 [tool.towncrier]
 package = "policyengine"
 directory = "changelog.d"
diff --git a/src/policyengine/tax_benefit_models/us/model.py b/src/policyengine/tax_benefit_models/us/model.py
index f13cdb9b..d8c05704 100644
--- a/src/policyengine/tax_benefit_models/us/model.py
+++ b/src/policyengine/tax_benefit_models/us/model.py
@@ -27,7 +27,13 @@
 if TYPE_CHECKING:
     from policyengine.core.simulation import Simulation
 
-US_GROUP_ENTITIES = ["household", "tax_unit", "spm_unit", "family", "marital_unit"]
+US_GROUP_ENTITIES = [
+    "household",
+    "tax_unit",
+    "spm_unit",
+    "family",
+    "marital_unit",
+]
 
 
 class PolicyEngineUS(TaxBenefitModel):
diff --git a/src/policyengine/utils/parametric_reforms.py b/src/policyengine/utils/parametric_reforms.py
index d0acc33d..71476afa 100644
--- a/src/policyengine/utils/parametric_reforms.py
+++ b/src/policyengine/utils/parametric_reforms.py
@@ -82,7 +82,9 @@ def modifier(simulation):
     return modifier
 
 
-def build_reform_dict(policy_or_dynamic: Policy | Dynamic | None) -> dict | None:
+def build_reform_dict(
+    policy_or_dynamic: Policy | Dynamic | None,
+) -> dict | None:
     """Extract a reform dict from a Policy or Dynamic object.
 
     If the object has parameter_values, converts them to reform dict format.