diff --git a/.github/workflows/tier0.yml b/.github/workflows/tier0.yml
new file mode 100644
index 0000000..75dead2
--- /dev/null
+++ b/.github/workflows/tier0.yml
@@ -0,0 +1,33 @@
+name: Tier 0 — Unit (Linux)
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+# Minimal-deps run: Tier 0 must work without ComfyUI, coremltools, or
+# python_coreml_stable_diffusion (Linux CI image won't have them). The
+# in-tree purity gate (tests/unit/test_tier0_purity.py) double-checks
+# that the suite hasn't started leaking framework imports.
+jobs:
+  unit:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install Tier 0 deps
+        run: |
+          python -m pip install --upgrade pip
+          # Pins mirror pyproject (Phase 1 baseline). Tier 0 only needs
+          # torch + numpy + pytest; everything else is Mac-only.
+          python -m pip install \
+            "torch==2.0.1" "numpy<1.25" \
+            "pytest>=8" "pytest-xdist"
+
+      - name: Run Tier 0
+        run: pytest -m unit tests/ -v
diff --git a/.github/workflows/tier1.yml b/.github/workflows/tier1.yml
new file mode 100644
index 0000000..bb063ea
--- /dev/null
+++ b/.github/workflows/tier1.yml
@@ -0,0 +1,31 @@
+name: Tier 1 — Smoke (macOS-ARM)
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    # Gate behind the run-tier1 label too, so external PRs that touch
+    # only docs don't burn a minute of macOS-ARM time. Maintainers can
+    # always re-run via the run-tier1 label.
+    types: [opened, synchronize, reopened, labeled]
+
+jobs:
+  smoke:
+    if: |
+      github.event_name == 'push' ||
+      github.event.action != 'labeled' ||
+      contains(github.event.pull_request.labels.*.name, 'run-tier1')
+    runs-on: macos-14  # M1, Apple Silicon hosted runner
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+
+      - name: uv sync
+        run: uv sync --no-install-project
+
+      - name: Run Tier 1 (synthetic micro-UNet smoke)
+        run: uv run pytest -m smoke tests/ -v
diff --git a/.github/workflows/tier2.yml b/.github/workflows/tier2.yml
new file mode 100644
index 0000000..a7ec67e
--- /dev/null
+++ b/.github/workflows/tier2.yml
@@ -0,0 +1,63 @@
+name: Tier 2 — M2 / ANE (self-hosted)
+
+on:
+  pull_request:
+    types: [labeled]
+  schedule:
+    # Nightly at 04:00 UTC (~05/06 in PL). Keeps the M2 path honest
+    # without burning the runner on every PR.
+    - cron: "0 4 * * *"
+  workflow_dispatch:
+
+jobs:
+  m2:
+    if: |
+      github.event_name == 'schedule' ||
+      github.event_name == 'workflow_dispatch' ||
+      (github.event_name == 'pull_request' &&
+       contains(github.event.pull_request.labels.*.name, 'run-m2'))
+    # Self-hosted Mac registered by the maintainer. See docs/ci-m2.md
+    # for runner setup and required model paths.
+    runs-on: [self-hosted, macOS, ARM64, coreml]
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: uv sync
+        run: uv sync
+
+      - name: Start ComfyUI server (background)
+        env:
+          COMFY_DIR: ${{ env.COMFY_DIR }}
+        run: |
+          cd "$COMFY_DIR"
+          nohup "$GITHUB_WORKSPACE/.venv/bin/python" main.py --port 8188 --cpu-vae > /tmp/comfyui-ci.log 2>&1 &
+          # Wait for readiness, fail fast if it never comes up.
+          for _ in $(seq 1 60); do
+            if grep -q "To see the GUI" /tmp/comfyui-ci.log 2>/dev/null; then
+              echo "comfy ready"; exit 0
+            fi
+            sleep 2
+          done
+          echo "comfy failed to start"; tail -100 /tmp/comfyui-ci.log; exit 1
+
+      - name: Run Tier 2 (m2 marker)
+        run: uv run pytest -m m2 tests/ -v
+
+      - name: Run bench harness
+        run: |
+          uv run python bench/run.py \
+            --model "$COMFY_DIR/models/unet/v1-5-pruned-emaonly_1x512x512_se_unet.mlmodelc" \
+            --compute-units CPU_AND_NE CPU_AND_GPU \
+            --repeats 30 --assumed-steps 20
+
+      - name: Upload bench results
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: bench-results
+          path: bench/results/*.json
+
+      - name: Stop ComfyUI server
+        if: always()
+        run: pkill -f "main.py.*8188" || true
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8a2c480
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,76 @@
+# ComfyUI-CoreMLSuite — tiered test/bench dispatcher (Phase 4).
+#
+# Tiers (see MODERNIZATION_SPEC.md):
+#   Tier 0 (unit):  framework-free pure-logic tests, run anywhere in seconds.
+#   Tier 1 (smoke): macOS-ARM, no ANE, no full model — converts a synthetic
+#                   micro-UNet to catch coremltools / ml-stable-diffusion
+#                   API breakage in minutes.
+#   Tier 2 (m2):    real ANE on Apple Silicon; integration + bench.
+#
+# COMFY_DIR defaults to the canonical custom-node layout (two dirs up from here).
+# PY defaults to the project's uv-managed venv interpreter.
+
+COMFY_DIR ?= $(realpath $(CURDIR)/../..)
+PY ?= $(CURDIR)/.venv/bin/python
+PYTEST ?= $(PY) -m pytest
+
+UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
+IS_MACOS_ARM := $(filter Darwin,$(UNAME_S))$(filter arm64,$(UNAME_M))
+
+.PHONY: help test-unit test-smoke test-m2 bench bench-rerun ci-tier0 ci-tier1 clean check-macos-arm
+
+help:
+	@echo "ComfyUI-CoreMLSuite — make targets"
+	@echo ""
+	@echo "  test-unit       Tier 0: pure-logic pytest, runs anywhere, seconds"
+	@echo "  test-smoke      Tier 1: synthetic micro-UNet ct.convert + load (macOS-ARM, minutes)"
+	@echo "  test-m2         Tier 2: pytest -m m2 against a real Core ML UNet (Apple Silicon + ANE)"
+	@echo "  bench           Run bench/run.py against a converted .mlmodelc"
+	@echo ""
+	@echo "Vars: COMFY_DIR (default: $(COMFY_DIR)), PY (default: $(PY))"
+
+check-macos-arm:
+	@if [ -z "$(IS_MACOS_ARM)" ]; then \
+		echo "this target requires macOS on Apple Silicon (got $(UNAME_S)/$(UNAME_M))"; \
+		exit 2; \
+	fi
+
+# Tier 0 — Linux-safe pure logic. Should not import comfy/coremltools.
+test-unit:
+	$(PYTEST) -m unit tests/
+
+# Tier 1 — macOS-ARM smoke. Converts a synthetic UNet through coremltools to
+# catch API breakage without needing a real SD checkpoint or the ANE.
+test-smoke: check-macos-arm
+	$(PYTEST) -m smoke tests/
+
+# Tier 2 — full Apple Silicon path: integration + m2 golden + bench.
+# Requires a converted .mlmodelc (see bench/scripts/convert_sd15.py).
+test-m2: check-macos-arm
+	$(PYTEST) -m m2 tests/
+
+# Bench harness. Override MODEL=/path/to/.mlmodelc for an explicit model.
+MODEL ?= $(COMFY_DIR)/models/unet/v1-5-pruned-emaonly_1x512x512_se_unet.mlmodelc
+COMPUTE_UNITS ?= CPU_AND_NE CPU_AND_GPU
+REPEATS ?= 30
+ASSUMED_STEPS ?= 20
+bench: check-macos-arm
+	$(PY) bench/run.py \
+		--model "$(MODEL)" \
+		--compute-units $(COMPUTE_UNITS) \
+		--repeats $(REPEATS) \
+		--assumed-steps $(ASSUMED_STEPS)
+
+# What CI actually invokes — same as test-unit but echoes the env capture
+# alongside so failed runs land with diagnostics.
+ci-tier0:
+	@echo "## env (Tier 0)" && $(PY) --version && uv pip freeze --python "$(PY)" 2>/dev/null | head -50 || true
+	$(MAKE) test-unit
+
+ci-tier1: check-macos-arm
+	@echo "## env (Tier 1)" && $(PY) --version && uv pip freeze --python "$(PY)" 2>/dev/null | head -50 || true
+	$(MAKE) test-smoke
+
+clean:
+	rm -rf .pytest_cache tests/m2/_latest_generated.png pytestdebug.log
diff --git a/docs/ci-m2.md b/docs/ci-m2.md
new file mode 100644
index 0000000..4cf7912
--- /dev/null
+++ b/docs/ci-m2.md
@@ -0,0 +1,90 @@
+# Self-hosted M2 runner — setup
+
+Tier 2 (ANE + integration + bench) runs on a self-hosted GitHub Actions
+runner registered against the maintainer's M-series Mac. Hosted macOS
+runners on GitHub do not expose the Apple Neural Engine, so the ANE
+half of the matrix has to live on real hardware.
+
+## One-time runner setup
+
+1. **Install dependencies on the Mac.** Python 3.11.x (matching the
+   `requires-python` pin), `uv`, `git`, plus the ComfyUI checkout at the
+   path the workflow expects (default: `$HOME/dev/ComfyUI`). The
+   workflow reads `COMFY_DIR` from the runner's env.
+
+   ```bash
+   brew install python@3.11 uv git
+   ```
+
+2. **Register the runner.** From the repo Settings → Actions → Runners
+   → New self-hosted runner, follow the macOS-ARM instructions. Add the
+   labels exactly: `self-hosted`, `macOS`, `ARM64`, `coreml` (the
+   workflow `runs-on` clause requires all four).
+
+   ```bash
+   mkdir ~/actions-runner && cd ~/actions-runner
+   curl -O -L https://github.com/actions/runner/releases/download/v2.317.0/actions-runner-osx-arm64-2.317.0.tar.gz
+   tar xzf actions-runner-osx-arm64-2.317.0.tar.gz
+   ./config.sh --url https://github.com/<owner>/<repo> \
+               --token <REGISTRATION_TOKEN> \
+               --labels self-hosted,macOS,ARM64,coreml \
+               --name "$(hostname)-m2"
+   ./svc.sh install && ./svc.sh start   # run as a launchd service
+   ```
+
+3. **Persist `COMFY_DIR` for the runner.** The workflow needs to know
+   where the ComfyUI checkout lives. Add it to the runner's `.env`:
+
+   ```bash
+   echo 'COMFY_DIR=/Users/<you>/dev/ComfyUI' >> ~/actions-runner/.env
+   ```
+
+4. **Pre-convert the baseline SD1.5 model.** The bench step expects
+   `$COMFY_DIR/models/unet/v1-5-pruned-emaonly_1x512x512_se_unet.mlmodelc`.
+   Run the conversion once manually:
+
+   ```bash
+   cd $GITHUB_WORKSPACE
+   uv run python bench/scripts/convert_sd15.py
+   ```
+
+   Re-runs of the same combination are a no-op; the converter skips when
+   the .mlmodelc already exists.
+
+## Triggers
+
+The Tier 2 workflow (`.github/workflows/tier2.yml`) runs:
+
+- **On PR label `run-m2`** — maintainers add the label to opt a PR
+  into the ANE lane (the runner is not free; default off).
+- **Nightly at 04:00 UTC** via `schedule:`.
+- **Manually** via the workflow_dispatch button.
+
+## Artifacts
+
+- Bench JSON/MD are uploaded as `bench-results`.
+- M2 golden image regressions surface as test failures in
+  `tests/m2/test_golden_image.py`; diff PNG is written next to the
+  golden under `tests/m2/_latest_generated.png` (gitignored).
+
+## When the runner is down
+
+If the maintainer's Mac is offline, the workflow queues until the
+runner comes back. Cancel a stuck run from the Actions UI; the gate is
+not blocking by default (Tier 0 + Tier 1 carry PR status). Tier 2 is
+"good to merge once it goes green," not "blocked until then."
+
+## Replacing the integration e2e
+
+The legacy `tests/integration/test_basic_conversion_1_5.py` checked
+CoreML output against an MPS reference image at PSNR > 25 dB. That
+reference path is broken on macOS 26.x with torch 2.0.1 (see Phase 1
+Gate report). Phase 4 moves the same coverage to
+`tests/m2/test_golden_image.py`, which:
+
+- runs the Core ML pipeline only (no MPS reference),
+- asserts SHA256 against `tests/m2/goldens/sd15_seed42.sha256`,
+- falls back to PSNR ≥ 40 dB if the hash drifts.
+
+This removes the human-eyeball dependency: a regression is now a
+numerical fail, not a "looks different to me."
diff --git a/tests/integration/test_basic_conversion_1_5.py b/tests/integration/test_basic_conversion_1_5.py
deleted file mode 100644
index 1107885..0000000
--- a/tests/integration/test_basic_conversion_1_5.py
+++ /dev/null
@@ -1,85 +0,0 @@
-import json
-import os
-
-import pytest
-import requests
-import torch
-from PIL import Image
-import numpy as np
-
-from folder_paths import get_save_image_path, get_output_directory
-
-IMAGE_PREFIX = "E2E-1.5"
-IMAGE_PREFIX_CML = f"{IMAGE_PREFIX}-CoreML"
-IMAGE_PREFIX_MPS = f"{IMAGE_PREFIX}-MPS"
-
-
-class OutputImageRepository:
-    def __init__(self, name_prefix):
-        self.name_prefix = name_prefix
-
-    def list_images(self):
-        full_output_folder, _, _, _, _ = get_save_image_path(
-            self.name_prefix, get_output_directory(), 512, 512
-        )
-        return full_output_folder, os.listdir(full_output_folder)
-
-    def delete_images(self):
-        full_output_folder, images = self.list_images()
-        for image in images:
-            os.remove(os.path.join(full_output_folder, image))
-
-    def get_latest_image(self, prefix):
-        full_output_folder, images = self.list_images()
-        for image in sorted(images, reverse=True):
-            if image.startswith(prefix):
-                return os.path.join(full_output_folder, image)
-        return None
-
-
-@pytest.fixture(scope="function")
-def output_image_repository():
-    repo = OutputImageRepository(IMAGE_PREFIX)
-    yield repo
-    repo.delete_images()
-
-
-def test_basic_conversion_1_5(output_image_repository):
-    with open("tests/integration/workflows/e2e-1.5-basic-conversion.json") as f:
-        prompt = json.load(f)
-    prompt = randomize_seed_in_prompt(prompt)
-    queue_prompt(prompt)
-
-    coreml_img_path = output_image_repository.get_latest_image(IMAGE_PREFIX_CML)
-    mps_img_path = output_image_repository.get_latest_image(IMAGE_PREFIX_MPS)
-
-    coreml_image = Image.open(coreml_img_path)
-    mps_image = Image.open(mps_img_path)
-
-    assert psnr(np.array(coreml_image), np.array(mps_image)) > 25
-
-
-def psnr(img1, img2):
-    mse = np.mean((img1 - img2) ** 2)
-    if mse == 0:
-        return 100
-    PIXEL_MAX = 255.0
-    return 20 * np.log10(PIXEL_MAX / np.sqrt(mse))
-
-
-def queue_prompt(prompt: dict):
-    p = {"prompt": prompt}
-    data = json.dumps(p).encode("utf-8")
-    req = requests.post("http://localhost:8188/prompt", data=data)
-    assert req.status_code == 200
-    while True:
-        req = requests.get("http://localhost:8188/prompt")
-        if req.json()["exec_info"]["queue_remaining"] == 0:
-            break
-
-
-def randomize_seed_in_prompt(prompt):
-    seed = torch.random.seed()
-    prompt["3"]["inputs"]["seed"] = seed
-    prompt["11"]["inputs"]["seed"] = seed
-    return prompt
diff --git a/tests/smoke/__init__.py b/tests/smoke/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/smoke/test_synthetic_unet.py b/tests/smoke/test_synthetic_unet.py
new file mode 100644
index 0000000..b5f074c
--- /dev/null
+++ b/tests/smoke/test_synthetic_unet.py
@@ -0,0 +1,122 @@
+"""Tier 1 smoke: convert a synthetic micro-UNet through coremltools and load
+it back with python_coreml_stable_diffusion's CoreMLModel.
+
+Purpose: catch API breakage in coremltools / ml-stable-diffusion *without*
+needing a real SD checkpoint, the ANE, or a converted .mlmodelc on disk.
+Runs in minutes on a hosted macOS-ARM runner (no Apple internal stuff).
+
+What it asserts:
+  - coremltools.convert still accepts the call shape we use today
+  - the resulting .mlpackage round-trips through CoreMLModel
+  - expected_inputs exposes the input names/shapes we declared
+  - calling the model returns the named output (`noise_pred`)
+
+Auto-skips on non-Apple-Silicon hosts so Tier 0 CI on Linux ignores it.
+"""
+import platform
+import shutil
+
+import numpy as np
+import pytest
+import torch
+import torch.nn as nn
+
+
+pytestmark = pytest.mark.skipif(
+    platform.system() != "Darwin" or platform.machine() != "arm64",
+    reason="Tier 1 requires macOS on Apple Silicon",
+)
+
+
+# Tiny shapes — large enough to exercise conv2d + linear + addition kernels in
+# coremltools, small enough that conversion finishes in seconds on CPU.
+SAMPLE_SHAPE = (1, 4, 8, 8)
+TIMESTEP_SHAPE = (1,)
+ENCODER_SHAPE = (1, 64, 1, 4)  # matches SD's transposed encoder_hidden_states layout
+OUT_NAME = "noise_pred"
+
+
+class TinyUNet(nn.Module):
+    """Minimal UNet-shaped graph: conv -> add(time+context) -> conv.
+
+    Not a real diffusion model. Just enough op variety to exercise the
+    PyTorch -> MIL frontend in coremltools and confirm we can still wire
+    the inputs/outputs the way ml-stable-diffusion expects.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.conv_in = nn.Conv2d(4, 8, kernel_size=3, padding=1)
+        self.conv_out = nn.Conv2d(8, 4, kernel_size=3, padding=1)
+        self.time_proj = nn.Linear(1, 8)
+        self.text_proj = nn.Linear(64, 8)
+
+    def forward(self, sample, timestep, encoder_hidden_states):
+        h = self.conv_in(sample)
+        t_emb = self.time_proj(timestep.unsqueeze(-1)).view(1, 8, 1, 1)
+        c_emb = self.text_proj(encoder_hidden_states.squeeze(2).mean(-1)).view(1, 8, 1, 1)
+        h = h + t_emb + c_emb
+        return self.conv_out(h)
+
+
+@pytest.fixture(scope="module")
+def tiny_mlpackage(tmp_path_factory):
+    """Convert TinyUNet once per test session and reuse the .mlpackage."""
+    import coremltools as ct
+
+    torch.manual_seed(0)
+    model = TinyUNet().eval()
+    example = (
+        torch.randn(*SAMPLE_SHAPE),
+        torch.randn(*TIMESTEP_SHAPE),
+        torch.randn(*ENCODER_SHAPE),
+    )
+    traced = torch.jit.trace(model, example)
+
+    mlmodel = ct.convert(
+        traced,
+        inputs=[
+            ct.TensorType(name="sample", shape=SAMPLE_SHAPE, dtype=np.float16),
+            ct.TensorType(name="timestep", shape=TIMESTEP_SHAPE, dtype=np.float16),
+            ct.TensorType(name="encoder_hidden_states", shape=ENCODER_SHAPE, dtype=np.float16),
+        ],
+        outputs=[ct.TensorType(name=OUT_NAME, dtype=np.float16)],
+        compute_units=ct.ComputeUnit.CPU_ONLY,
+        compute_precision=ct.precision.FLOAT16,
+        convert_to="mlprogram",
+        minimum_deployment_target=ct.target.macOS13,
+    )
+
+    out_dir = tmp_path_factory.mktemp("tiny_unet")
+    pkg_path = out_dir / "tiny.mlpackage"
+    mlmodel.save(str(pkg_path))
+    yield pkg_path
+    shutil.rmtree(out_dir, ignore_errors=True)
+
+
+def test_coremltools_convert_round_trips_via_coreml_model(tiny_mlpackage):
+    from python_coreml_stable_diffusion.coreml_model import CoreMLModel
+
+    model = CoreMLModel(str(tiny_mlpackage), "CPU_ONLY", "packages")
+
+    # expected_inputs is the contract our wrappers depend on. Lock the shape
+    # of the dict + a sample entry.
+    expected = dict(model.expected_inputs)
+    assert set(expected.keys()) == {"sample", "timestep", "encoder_hidden_states"}
+    assert tuple(expected["sample"]["shape"]) == SAMPLE_SHAPE
+    assert tuple(expected["timestep"]["shape"]) == TIMESTEP_SHAPE
+    assert tuple(expected["encoder_hidden_states"]["shape"]) == ENCODER_SHAPE
+
+    # Forward pass: drive the model the way CoreMLModelWrapper does.
+    rng = np.random.default_rng(0)
+    inputs = {
+        "sample": rng.standard_normal(SAMPLE_SHAPE).astype(np.float16),
+        "timestep": rng.standard_normal(TIMESTEP_SHAPE).astype(np.float16),
+        "encoder_hidden_states": rng.standard_normal(ENCODER_SHAPE).astype(np.float16),
+    }
+    out = model(**inputs)
+    assert isinstance(out, dict), f"unexpected output type: {type(out)}"
+    assert OUT_NAME in out, f"missing output {OUT_NAME!r}; got {sorted(out)}"
+    assert out[OUT_NAME].shape == SAMPLE_SHAPE, (
+        f"output shape drift: got {out[OUT_NAME].shape}, expected {SAMPLE_SHAPE}"
+    )