diff --git a/docs/ARCHITECTURE.md b/docs/ARCHITECTURE.md
index a9e616dc..23a585b7 100644
--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -2565,7 +2565,9 @@ All remaining open issues are enhancements (no bugs as of 2026-07-18). Prioritiz
 ### #291 — SpecKit-style preset composition (layered template resolution)
 **Slice 1 COMPLETE (PR #370, 2026-07-18)**: `mapify preset` sub-group with `list` and `add --from <path>` commands; `.map/presets/<id>/manifest.json` format (required keys: `id`, `title`, `version`); path-traversal guards; `--json` flag; `--force` overwrite; 29 tests in `tests/test_preset_commands.py`.
 
-**Next slice (Slice 2)**: `mapify preset remove <id>`, `mapify preset enable/disable <id>` (via `.enabled` flag in manifest or sidecar), and `mapify preset resolve <template>` (show which layer wins for a template). No composition engine yet — that's Slice 3. Key constraint: must not bypass the `make check-render` single-source invariant — presets should compose at render time, not by editing generated trees.
+**Slice 2 COMPLETE (PR #371, 2026-07-18)**: `mapify preset remove <id>` (with `--yes` bypass), `mapify preset enable/disable <id>` (persisted to `.map/presets/<id>/.state.json`), `mapify preset resolve <template>` (3-tier: project overrides → enabled presets → core templates; `--json`). 45 tests total in `tests/test_preset_commands.py`.
+
+**Next slice (Slice 3)**: The composition engine — when a preset's `templates/<name>` exists, apply the preset's strategy (`prepend`/`append`/`wrap`/`replace`) at render time. Add `mapify preset set-priority <id> <n>` to control ordering. Key constraint: must not bypass the `make check-render` single-source invariant — presets should compose at render time, not by editing generated trees. The composition should be a separate render pass (`mapify preset render <template>`) that layers preset content on top of the Jinja-rendered core output.
 
 ### #363 — Architecture deepening report (`/map-architecture` skill)
 New opt-in skill that ranks codebase areas by recent git hotspot + design friction, generates a candidate report (HTML or Markdown+Mermaid under `.map/<branch>/architecture-report/`), and holds off implementation until the user picks a candidate. First slice: create `src/mapify_cli/templates_src/skills/map-architecture/SKILL.md.jinja` + register in skill-rules.json. No Python code in slice 1 — just the workflow instructions.
diff --git a/src/mapify_cli/__init__.py b/src/mapify_cli/__init__.py
index f15b31dc..0c989248 100644
--- a/src/mapify_cli/__init__.py
+++ b/src/mapify_cli/__init__.py
@@ -2068,6 +2068,152 @@ def preset_resolve(
         console.print(f"  {i}. tier={tier}{preset_str}{strategy_str}{enabled_str} → {layer['path']}")
 
 
+# ---------------------------------------------------------------------------
+# Preset composition helpers (Slice 3)
+# ---------------------------------------------------------------------------
+
+_COMPOSITION_STRATEGIES = frozenset({"replace", "prepend", "append", "wrap"})
+_WRAP_PLACEHOLDER = "{CORE_TEMPLATE}"
+
+
+def _preset_priority(preset_dir: Path) -> int:
+    state = _read_preset_state(preset_dir)
+    return int(state.get("priority", 50))
+
+
+def _compose_template(core_content: str, layer_content: str, strategy: str) -> str:
+    """Apply a composition strategy to produce the final template content."""
+    if strategy == "replace":
+        return layer_content
+    if strategy == "prepend":
+        return layer_content + "\n" + core_content
+    if strategy == "append":
+        return core_content + "\n" + layer_content
+    if strategy == "wrap":
+        if _WRAP_PLACEHOLDER in layer_content:
+            return layer_content.replace(_WRAP_PLACEHOLDER, core_content)
+        return layer_content + "\n" + core_content
+    return core_content
+
+
+def _build_resolution_order(presets_root: Path, template_name: str) -> list[dict[str, Any]]:
+    """Return enabled preset layers for a template, sorted by priority descending."""
+    layers: list[dict[str, Any]] = []
+    if not presets_root.is_dir():
+        return layers
+    for entry in presets_root.iterdir():
+        if not entry.is_dir() or not _is_preset_enabled(entry):
+            continue
+        template_path = entry / "templates" / template_name
+        if not template_path.is_file():
+            continue
+        manifest = _read_preset_manifest(entry)
+        strategy = (manifest or {}).get("strategies", {}).get(template_name, "append")
+        layers.append({
+            "preset_id": entry.name,
+            "path": template_path,
+            "strategy": strategy,
+            "priority": _preset_priority(entry),
+        })
+    layers.sort(key=lambda x: x["priority"], reverse=True)
+    return layers
+
+
+@preset_app.command("render")
+def preset_render(
+    template_name: str = typer.Argument(..., help="Template name to render (e.g. 'map-efficient.md')."),
+    project_path: Optional[Path] = typer.Argument(
+        None,
+        help="Project root directory (defaults to current directory).",
+    ),
+    output_json: bool = typer.Option(False, "--json", help="Output rendered content as JSON."),
+    dry_run: bool = typer.Option(False, "--dry-run", help="Print composed content without writing to disk."),
+) -> None:
+    """Compose a template by layering enabled presets over the core template.
+
+    Strategies (applied highest-priority first):
+      replace — preset content replaces the core entirely
+      prepend — preset content is inserted above the core
+      append  — preset content is inserted below the core
+      wrap    — preset content wraps the core via {CORE_TEMPLATE} placeholder
+    """
+    target = project_path or Path.cwd()
+    presets_root = _presets_dir(target)
+
+    # Start from project override if present, else core template
+    project_override = target / ".map" / "overrides" / template_name
+    if project_override.is_file():
+        composed = project_override.read_text(encoding="utf-8")
+        source = f"project-override:{project_override}"
+    else:
+        try:
+            core_path = get_templates_dir() / template_name
+            if core_path.is_file():
+                composed = core_path.read_text(encoding="utf-8")
+                source = f"core:{core_path}"
+            else:
+                composed = ""
+                source = "core:(not found)"
+        except Exception:
+            composed = ""
+            source = "core:(error)"
+
+    layers = _build_resolution_order(presets_root, template_name)
+    applied: list[str] = []
+    for layer in layers:
+        layer_content = Path(layer["path"]).read_text(encoding="utf-8")
+        strategy: str = layer["strategy"]
+        if strategy not in _COMPOSITION_STRATEGIES:
+            strategy = "append"
+        composed = _compose_template(composed, layer_content, strategy)
+        applied.append(f"{layer['preset_id']}({strategy})")
+
+    if output_json:
+        typer.echo(json.dumps({
+            "template": template_name,
+            "source": source,
+            "applied_layers": applied,
+            "content": composed,
+        }))
+        return
+
+    if dry_run or True:
+        console.print(f"[bold]Composed:[/bold] [cyan]{template_name}[/cyan]")
+        if applied:
+            console.print(f"[dim]Layers applied:[/dim] {' → '.join(applied)}")
+        else:
+            console.print("[dim]No preset layers matched; showing core/override content.[/dim]")
+        console.print()
+        console.print(composed)
+
+
+@preset_app.command("set-priority")
+def preset_set_priority(
+    preset_id: str = typer.Argument(..., help="ID of the preset to reprioritize."),
+    priority: int = typer.Argument(..., help="Priority value (higher = applied first). Default: 50."),
+    project_path: Optional[Path] = typer.Argument(
+        None,
+        help="Project root directory (defaults to current directory).",
+    ),
+) -> None:
+    """Set the composition priority of an installed preset.
+
+    Higher priority presets are applied first in the composition stack.
+    When two presets target the same template, the one with higher priority
+    has its strategy applied first, then lower-priority presets layer on top.
+    """
+    target = project_path or Path.cwd()
+    preset_dir = _resolve_installed_preset(_presets_dir(target), preset_id)
+    if preset_dir is None:
+        console.print(f"[red]Error:[/red] Preset '{preset_id}' is not installed.")
+        raise typer.Exit(1)
+
+    state = _read_preset_state(preset_dir)
+    state["priority"] = priority
+    _write_preset_state(preset_dir, state)
+    console.print(f"[green]Preset '{preset_id}'[/green] priority set to {priority}.")
+
+
 # Research localization eval commands
 
 
diff --git a/tests/test_preset_commands.py b/tests/test_preset_commands.py
index fb372493..f76ec169 100644
--- a/tests/test_preset_commands.py
+++ b/tests/test_preset_commands.py
@@ -511,3 +511,175 @@ def test_resolve_strategy_shown(self, tmp_path: Path):
         lean_layer = next((layer for layer in data["layers"] if layer.get("preset_id") == "lean"), None)
         assert lean_layer is not None
         assert lean_layer.get("strategy") == "append"
+
+
+# ---------------------------------------------------------------------------
+# PC12 — preset render: composition engine
+# ---------------------------------------------------------------------------
+
+
+class TestPc12PresetRender:
+    def _install_preset_with_template(self, project: Path, name: str, template: str,
+                                      content: str, strategy: str = "append", priority: int = 50) -> None:
+        dest = project / ".map" / "presets" / name
+        (dest / "templates").mkdir(parents=True, exist_ok=True)
+        (dest / "manifest.json").write_text(
+            json.dumps({"id": name, "title": name.title(), "version": "1.0.0",
+                        "strategies": {template: strategy}}), encoding="utf-8"
+        )
+        (dest / "templates" / template).write_text(content, encoding="utf-8")
+        if priority != 50:
+            (dest / ".state.json").write_text(
+                json.dumps({"enabled": True, "priority": priority}), encoding="utf-8"
+            )
+
+    def _install_core_override(self, project: Path, template: str, content: str) -> None:
+        (project / ".map" / "overrides").mkdir(parents=True, exist_ok=True)
+        (project / ".map" / "overrides" / template).write_text(content, encoding="utf-8")
+
+    def test_render_no_presets_exits_zero(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project)])
+        assert result.exit_code == 0
+
+    def test_render_append_strategy(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        self._install_preset_with_template(project, "lean", "map-efficient.md", "PRESET", strategy="append")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        content = data["content"]
+        assert content.index("CORE") < content.index("PRESET")
+
+    def test_render_prepend_strategy(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        self._install_preset_with_template(project, "lean", "map-efficient.md", "PRESET", strategy="prepend")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        content = data["content"]
+        assert content.index("PRESET") < content.index("CORE")
+
+    def test_render_replace_strategy(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        self._install_preset_with_template(project, "lean", "map-efficient.md", "REPLACED", strategy="replace")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        assert data["content"].strip() == "REPLACED"
+        assert "CORE" not in data["content"]
+
+    def test_render_wrap_strategy_with_placeholder(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        wrap_content = "BEFORE\n{CORE_TEMPLATE}\nAFTER"
+        self._install_preset_with_template(project, "lean", "map-efficient.md", wrap_content, strategy="wrap")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        content = data["content"]
+        assert "BEFORE" in content
+        assert "CORE" in content
+        assert "AFTER" in content
+        assert content.index("BEFORE") < content.index("CORE") < content.index("AFTER")
+
+    def test_render_json_has_required_fields(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        result = runner.invoke(app, ["preset", "render", "any.md", str(project), "--json"])
+        data = json.loads(result.output)
+        for key in ("template", "source", "applied_layers", "content"):
+            assert key in data, f"missing key: {key}"
+
+    def test_render_applied_layers_listed(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        self._install_preset_with_template(project, "lean", "map-efficient.md", "L", strategy="append")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        assert len(data["applied_layers"]) == 1
+        assert "lean" in data["applied_layers"][0]
+
+    def test_render_disabled_preset_skipped(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "CORE")
+        self._install_preset_with_template(project, "lean", "map-efficient.md", "PRESET", strategy="append")
+        runner.invoke(app, ["preset", "disable", "lean", str(project)])
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        assert data["applied_layers"] == []
+        assert "PRESET" not in data["content"]
+
+    def test_render_project_override_used_as_base(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        self._install_core_override(project, "map-efficient.md", "OVERRIDE_BASE")
+        result = runner.invoke(app, ["preset", "render", "map-efficient.md", str(project), "--json"])
+        data = json.loads(result.output)
+        assert "OVERRIDE_BASE" in data["content"]
+        assert "project-override" in data["source"]
+
+
+# ---------------------------------------------------------------------------
+# PC13 — preset set-priority
+# ---------------------------------------------------------------------------
+
+
+class TestPc13PresetSetPriority:
+    def _install(self, project: Path, name: str) -> Path:
+        dest = project / ".map" / "presets" / name
+        dest.mkdir(parents=True)
+        (dest / "manifest.json").write_text(
+            json.dumps({"id": name, "title": name.title(), "version": "1.0.0"}), encoding="utf-8"
+        )
+        return dest
+
+    def test_set_priority_writes_state(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        dest = self._install(project, "lean")
+        result = runner.invoke(app, ["preset", "set-priority", "lean", "100", str(project)])
+        assert result.exit_code == 0
+        state = json.loads((dest / ".state.json").read_text())
+        assert state["priority"] == 100
+
+    def test_set_priority_nonexistent_exits_nonzero(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        result = runner.invoke(app, ["preset", "set-priority", "missing", "100", str(project)])
+        assert result.exit_code != 0
+
+    def test_priority_affects_composition_order(self, tmp_path: Path):
+        project = tmp_path / "project"
+        project.mkdir()
+        (project / ".map" / "overrides").mkdir(parents=True)
+        (project / ".map" / "overrides" / "t.md").write_text("CORE", encoding="utf-8")
+
+        for name, content, prio in [("alpha", "ALPHA", 10), ("beta", "BETA", 90)]:
+            dest = project / ".map" / "presets" / name
+            (dest / "templates").mkdir(parents=True)
+            (dest / "manifest.json").write_text(
+                json.dumps({"id": name, "title": name, "version": "1.0",
+                            "strategies": {"t.md": "append"}}), encoding="utf-8"
+            )
+            (dest / "templates" / "t.md").write_text(content, encoding="utf-8")
+            (dest / ".state.json").write_text(
+                json.dumps({"enabled": True, "priority": prio}), encoding="utf-8"
+            )
+
+        result = runner.invoke(app, ["preset", "render", "t.md", str(project), "--json"])
+        data = json.loads(result.output)
+        content = data["content"]
+        # beta (priority 90) applied first → appended first after core
+        # alpha (priority 10) applied second → appended after that
+        beta_pos = content.index("BETA")
+        alpha_pos = content.index("ALPHA")
+        core_pos = content.index("CORE")
+        assert core_pos < beta_pos < alpha_pos