diff --git a/adapters/__init__.py b/adapters/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/adapters/atlassian/__init__.py b/adapters/atlassian/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/adapters/m365/__init__.py b/adapters/m365/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/adapters/selfhosted/__init__.py b/adapters/selfhosted/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/core/__init__.py b/src/core/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/core/config.py b/src/core/config.py
new file mode 100644
index 0000000..18317f3
--- /dev/null
+++ b/src/core/config.py
@@ -0,0 +1,115 @@
+"""Config loader — merges core.yaml with a target overlay and validates with Pydantic."""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+import yaml
+from pydantic import BaseModel, field_validator
+
+# ---------------------------------------------------------------------------
+# Schema
+# ---------------------------------------------------------------------------
+
+
+class Organisation(BaseModel):
+    name: str
+    short: str
+    quality_officer: str
+    management: str
+
+
+class Role(BaseModel):
+    id: str
+    label: str
+    responsibilities: list[str]
+
+
+class Clause(BaseModel):
+    id: str
+    title: str
+    documents: list[str]
+
+
+class Document(BaseModel):
+    id: str
+    title: str
+    template: str | None
+    clause: str
+
+
+class RecordType(BaseModel):
+    id: str
+    label: str
+    clause: str
+    fields: list[str]
+
+
+class KPI(BaseModel):
+    id: str
+    label: str
+    unit: str
+    target: str
+    frequency: str
+    clause: str
+
+
+class CapaState(BaseModel):
+    id: str
+    label: str
+    transitions: list[str]
+
+
+class Meta(BaseModel):
+    version: str
+    standard: str
+
+
+class CoreConfig(BaseModel):
+    meta: Meta
+    organisation: Organisation
+    roles: list[Role]
+    clauses: list[Clause]
+    documents: list[Document]
+    record_types: list[RecordType]
+    kpis: list[KPI]
+    capa_states: list[CapaState]
+
+    @field_validator("documents")
+    @classmethod
+    def document_ids_unique(cls, docs: list[Document]) -> list[Document]:
+        ids = [d.id for d in docs]
+        duplicates = {i for i in ids if ids.count(i) > 1}
+        if duplicates:
+            raise ValueError(f"Duplicate document IDs: {duplicates}")
+        return docs
+
+
+# ---------------------------------------------------------------------------
+# Loader
+# ---------------------------------------------------------------------------
+
+
+def _load_yaml(path: Path) -> dict[str, Any]:
+    with path.open(encoding="utf-8") as fh:
+        return yaml.safe_load(fh) or {}
+
+
+def _deep_merge(base: dict[str, Any], overlay: dict[str, Any]) -> dict[str, Any]:
+    """Recursively merge overlay into base (overlay wins on conflicts)."""
+    merged = base.copy()
+    for key, value in overlay.items():
+        if key in merged and isinstance(merged[key], dict) and isinstance(value, dict):
+            merged[key] = _deep_merge(merged[key], value)
+        else:
+            merged[key] = value
+    return merged
+
+
+def load_config(core_path: Path, overlay_path: Path) -> CoreConfig:
+    """Load and merge core + overlay YAML, return validated CoreConfig."""
+    core_data = _load_yaml(core_path)
+    overlay_data = _load_yaml(overlay_path)
+    merged = _deep_merge(core_data, overlay_data)
+    return CoreConfig.model_validate(merged)
diff --git a/src/core/renderer.py b/src/core/renderer.py
new file mode 100644
index 0000000..fb4a4cc
--- /dev/null
+++ b/src/core/renderer.py
@@ -0,0 +1,44 @@
+"""Jinja2 template renderer — renders .md.j2 templates with config context."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from jinja2 import Environment, FileSystemLoader, StrictUndefined, select_autoescape
+
+from src.core.config import CoreConfig
+
+
+def build_context(config: CoreConfig, extra: dict | None = None) -> dict:
+    """Build the base Jinja2 context from a validated config."""
+    ctx: dict = {
+        "org_name": config.organisation.name,
+        "org_short": config.organisation.short,
+        "quality_officer": config.organisation.quality_officer,
+        "management": config.organisation.management,
+        "version": config.meta.version,
+    }
+    if extra:
+        ctx.update(extra)
+    return ctx
+
+
+def render_template(
+    template_name: str,
+    config: CoreConfig,
+    templates_dir: Path,
+    extra: dict | None = None,
+) -> str:
+    """Render a single .md.j2 template and return the result as a string.
+
+    Raises jinja2.UndefinedError if a placeholder has no value in context.
+    """
+    env = Environment(
+        loader=FileSystemLoader(str(templates_dir)),
+        undefined=StrictUndefined,
+        autoescape=select_autoescape(enabled_extensions=("html",)),
+        keep_trailing_newline=True,
+    )
+    template = env.get_template(template_name)
+    context = build_context(config, extra)
+    return template.render(**context)
diff --git a/tests/test_config.py b/tests/test_config.py
new file mode 100644
index 0000000..e6db3c7
--- /dev/null
+++ b/tests/test_config.py
@@ -0,0 +1,65 @@
+"""Unit tests for the config loader."""
+
+from pathlib import Path
+
+from src.core.config import _deep_merge
+
+CORE_YAML = Path(__file__).parent.parent / "config" / "core.yaml"
+SELFHOSTED_YAML = Path(__file__).parent.parent / "config" / "selfhosted.yaml"
+
+
+class TestDeepMerge:
+    def test_overlay_wins_on_conflict(self) -> None:
+        base = {"a": 1, "b": {"x": 10, "y": 20}}
+        overlay = {"b": {"x": 99}, "c": 3}
+        result = _deep_merge(base, overlay)
+        assert result == {"a": 1, "b": {"x": 99, "y": 20}, "c": 3}
+
+    def test_base_unchanged(self) -> None:
+        base = {"a": 1}
+        _deep_merge(base, {"a": 2})
+        assert base == {"a": 1}
+
+
+class TestCoreConfig:
+    def test_core_yaml_loads_without_overlay(self) -> None:
+        """core.yaml must be parseable on its own (Jinja placeholders are strings)."""
+        import yaml
+
+        with CORE_YAML.open(encoding="utf-8") as fh:
+            data = yaml.safe_load(fh)
+        assert "clauses" in data
+        assert "documents" in data
+        assert len(data["clauses"]) == 7  # clauses 4-10
+
+    def test_all_clause_document_refs_exist(self) -> None:
+        import yaml
+
+        with CORE_YAML.open(encoding="utf-8") as fh:
+            data = yaml.safe_load(fh)
+        doc_ids = {d["id"] for d in data["documents"]}
+        for clause in data["clauses"]:
+            for ref in clause["documents"]:
+                assert ref in doc_ids, f"Clause {clause['id']} references unknown doc '{ref}'"
+
+    def test_kpis_have_required_fields(self) -> None:
+        import yaml
+
+        with CORE_YAML.open(encoding="utf-8") as fh:
+            data = yaml.safe_load(fh)
+        for kpi in data["kpis"]:
+            assert "id" in kpi
+            assert "label" in kpi
+            assert "target" in kpi
+
+    def test_capa_state_transitions_reference_valid_states(self) -> None:
+        import yaml
+
+        with CORE_YAML.open(encoding="utf-8") as fh:
+            data = yaml.safe_load(fh)
+        state_ids = {s["id"] for s in data["capa_states"]}
+        for state in data["capa_states"]:
+            for transition in state["transitions"]:
+                assert transition in state_ids, (
+                    f"State '{state['id']}' transitions to unknown state '{transition}'"
+                )
diff --git a/tests/test_renderer.py b/tests/test_renderer.py
new file mode 100644
index 0000000..26598f2
--- /dev/null
+++ b/tests/test_renderer.py
@@ -0,0 +1,80 @@
+"""Unit tests for the Jinja2 template renderer."""
+
+from pathlib import Path
+from unittest.mock import MagicMock
+
+from src.core.renderer import build_context, render_template
+
+TEMPLATES_DIR = Path(__file__).parent.parent / "templates"
+
+
+def _make_config(org_name: str = "Acme Ltd") -> MagicMock:
+    cfg = MagicMock()
+    cfg.organisation.name = org_name
+    cfg.organisation.short = "ACME"
+    cfg.organisation.quality_officer = "Jane Smith"
+    cfg.organisation.management = "John Doe"
+    cfg.meta.version = "1.0"
+    return cfg
+
+
+class TestBuildContext:
+    def test_contains_org_fields(self) -> None:
+        ctx = build_context(_make_config())
+        assert ctx["org_name"] == "Acme Ltd"
+        assert ctx["quality_officer"] == "Jane Smith"
+        assert ctx["management"] == "John Doe"
+        assert ctx["version"] == "1.0"
+
+    def test_extra_values_merged(self) -> None:
+        ctx = build_context(_make_config(), extra={"date": "2024-01-01"})
+        assert ctx["date"] == "2024-01-01"
+
+    def test_extra_overrides_base(self) -> None:
+        ctx = build_context(_make_config(), extra={"org_name": "Override Corp"})
+        assert ctx["org_name"] == "Override Corp"
+
+
+class TestRenderTemplate:
+    def test_policy_renders_org_name(self) -> None:
+        result = render_template(
+            "policy.md.j2",
+            _make_config(),
+            TEMPLATES_DIR,
+            extra={"date": "2024-01-01"},
+        )
+        assert "Acme Ltd" in result
+        assert "ISO 9001:2015" in result
+
+    def test_procedure_renders_title(self) -> None:
+        result = render_template(
+            "procedure.md.j2",
+            _make_config(),
+            TEMPLATES_DIR,
+            extra={
+                "procedure_title": "Document Control",
+                "doc_id": "QMS-7.5-001",
+                "clause": "7.5",
+                "owner_role": "QMO",
+                "approver": "John Doe",
+                "author": "Jane Smith",
+                "date": "2024-01-01",
+            },
+        )
+        assert "Document Control" in result
+        assert "7.5" in result
+
+    def test_capa_form_renders(self) -> None:
+        result = render_template(
+            "capa_form.md.j2",
+            _make_config(),
+            TEMPLATES_DIR,
+            extra={
+                "capa_id": "CAPA-2024-001",
+                "opened_date": "2024-01-01",
+                "opened_by": "Jane Smith",
+                "source_ref": "NC-2024-003",
+            },
+        )
+        assert "CAPA-2024-001" in result
+        assert "10.2" in result