diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 92cbd82..978dddd 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -18,7 +18,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.11"
+          python-version: "3.12"
 
       - name: Install dependencies
         run: |
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f0fde9e..59ab146 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -2,16 +2,16 @@ name: Tests
 
 on:
   push:
-    branches: [main]
+    branches: [main, claude/spec-driven-engine]
   pull_request:
-    branches: [main]
+    branches: [main, claude/spec-driven-engine]
 
 jobs:
   test:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.12", "3.13", "3.14"]
 
     steps:
       - uses: actions/checkout@v4
@@ -21,10 +21,15 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
+      - name: Set up uv
+        uses: astral-sh/setup-uv@v6
+
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
-          pip install -e ".[dev]"
+          # uv (not pip) so [tool.uv.sources] is honored — microimpute is
+          # pinned to a git rev there; plain pip resolves PyPI instead and
+          # gets an Imputer API the spec engine cannot run against.
+          uv pip install --system -e ".[dev]"
 
       - name: Run tests
         run: |
diff --git a/pyproject.toml b/pyproject.toml
index 10ae935..4d9bb10 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,14 +24,13 @@ classifiers = [
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
     "Topic :: Scientific/Engineering :: Artificial Intelligence",
     "Topic :: Scientific/Engineering :: Information Analysis",
 ]
-requires-python = ">=3.11"
+requires-python = ">=3.12"
 dependencies = [
     "torch>=2.0",
     "numpy>=1.24",
@@ -70,7 +69,7 @@ l0 = [
 calibrate = [
     # Identity-preserving gradient-descent chi-squared adapter.
     # microcalibrate pins Python >=3.13; the marker avoids breaking
-    # microplex installs on 3.11/3.12 that don't need the extra.
+    # microplex installs on 3.12 that don't need the extra.
     "microcalibrate>=0.22; python_version >= '3.13'",
 ]
 benchmark = [
@@ -122,7 +121,7 @@ select = ["E", "F", "I", "N", "W", "UP"]
 ignore = ["E501"]  # Line length handled by formatter
 
 [tool.mypy]
-python_version = "3.11"
+python_version = "3.12"
 warn_return_any = true
 warn_unused_configs = true
 ignore_missing_imports = true
diff --git a/tests/core/__init__.py b/tests/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/spec/__init__.py b/tests/spec/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/targets/__init__.py b/tests/targets/__init__.py
new file mode 100644
index 0000000..e69de29