diff --git a/evaluate/__init__.py b/evaluate/__init__.py
new file mode 100644
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--- /dev/null
+++ b/evaluate/__init__.py
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+from .wnn_gpu import wnn_gpu
\ No newline at end of file
diff --git a/evaluate/wnn_gpu.py b/evaluate/wnn_gpu.py
new file mode 100644
index 0000000..ad1b053
--- /dev/null
+++ b/evaluate/wnn_gpu.py
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+"""
+wnn_gpu.py — Person-1 (API & Alignment)
+
+Handles:
+  - Input validation for MuData with two modalities (RNA, ATAC)
+  - Cell alignment across modalities (same cells, same order)
+  - Reproducibility metadata (params + alignment report)
+  - Seeds + optional RMM memory pool init (safe no-ops without RAPIDS)
+  - Host↔device helpers for later GPU stages (cuML/cuGraph)
+
+Note: This file is CPU-safe. If CuPy/RMM aren’t installed, GPU bits are skipped.
+"""
+
+from __future__ import annotations
+from dataclasses import dataclass, asdict
+from typing import Tuple, Dict, Any, Iterable
+import contextlib
+import random
+import hashlib  # <-- added
+import numpy as np
+from mudata import MuData
+
+
+# --------------------------- GPU plumbing (safe no-ops) ---------------------------
+def init_seeds_and_pool(seed: int) -> None:
+    """Set CPU/CuPy RNG seeds and (optionally) initialize an RMM pool for CuPy."""
+    # CPU determinism
+    random.seed(seed)
+    np.random.seed(seed)
+
+    # Optional: CuPy RNG + RMM pool (only if available)
+    with contextlib.suppress(ImportError):
+        import cupy as cp  # type: ignore
+        cp.random.seed(seed)
+        with contextlib.suppress(ImportError):
+            import rmm  # type: ignore
+            # Initialize a simple pool allocator if not already initialized
+            if not rmm.is_initialized():
+                rmm.reinitialize(pool_allocator=True)
+            # Tell CuPy to use RMM for allocations
+            cp.cuda.set_allocator(rmm.rmm_cupy_allocator)
+
+
+def to_device(x):
+    """Move a NumPy array (or array-like) to GPU (CuPy) if available; otherwise return unchanged."""
+    try:
+        import cupy as cp  # type: ignore
+        # (Extend later for sparse types if needed)
+        return cp.asarray(x)
+    except ImportError:
+        return x
+
+
+def to_host(x):
+    """Bring a CuPy array back to host NumPy if needed; otherwise return unchanged."""
+    try:
+        import cupy as cp  # type: ignore
+        if isinstance(x, cp.ndarray):
+            return cp.asnumpy(x)
+    except ImportError:
+        pass
+    return x
+
+
+# ----------------------------- Validation -----------------------------
+def validate_mudata(mdata: MuData, modalities: Tuple[str, str] = ("rna", "atac")) -> MuData:
+    """
+    Ensure the input is a MuData with the expected modalities and that
+    each modality has non-empty obs/var.
+    """
+    if not isinstance(mdata, MuData):
+        raise TypeError("Expected a mudata.MuData object")
+
+    for key in modalities:
+        if key not in mdata.mod:
+            raise KeyError(f"MuData is missing modality '{key}'")
+        ad = mdata.mod[key]
+        if ad.n_obs == 0 or ad.n_vars == 0:
+            raise ValueError(f"Modality '{key}' is empty (no cells or no features).")
+    return mdata
+
+
+# ----------------------------- Alignment ------------------------------
+@dataclass
+class AlignmentReport:
+    """Summary of alignment results; stored in mdata.uns['wnn_alignment']."""
+    rna_n_before: int
+    atac_n_before: int
+    n_intersection: int
+    n_only_rna: int
+    n_only_atac: int
+    kept_fraction: float
+    order_hash: str
+    notes: str = "Cells present in both modalities were kept; others dropped."
+
+    def to_meta(self) -> Dict[str, Any]:
+        return asdict(self)
+
+
+def _stable_order_hash(names) -> str:
+    """Stable, cross-process/content-based hash of the final cell order."""
+    h = hashlib.sha1()
+    for n in names:
+        h.update(str(n).encode("utf-8"))
+        h.update(b"\x00")
+    return h.hexdigest()
+
+
+def _intersection_in_reference_order(ref_names: Iterable[str], other_names: Iterable[str]):
+    """Intersection of two name lists, preserving the order of the first (reference)."""
+    other_set = set(other_names)
+    return [c for c in ref_names if c in other_set]
+
+
+def align_modalities(mdata: MuData, rna_key: str = "rna", atac_key: str = "atac") -> AlignmentReport:
+    """
+    Make RNA and ATAC refer to the same cells in the same order.
+    Steps:
+      1) Compute intersection (RNA order).
+      2) Subset both modalities to that intersection.
+      3) Verify identical final orders.
+      4) Write aligned AnnData back into mdata.mod[...].
+      5) Return a report with counts + a quick hash of final order.
+    """
+    ad_rna = mdata.mod[rna_key]
+    ad_atac = mdata.mod[atac_key]
+
+    rna_n_before = ad_rna.n_obs
+    atac_n_before = ad_atac.n_obs
+
+    inter = _intersection_in_reference_order(ad_rna.obs_names.tolist(),
+                                             ad_atac.obs_names.tolist())
+
+    # ---- added: empty intersection guard ----
+    if len(inter) == 0:
+        raise ValueError(
+            "RNA and ATAC share 0 cells after matching obs_names. "
+            "Check barcode prefixes/suffixes (e.g., '-1' vs no suffix) or preprocessing steps."
+        )
+
+    n_intersection = len(inter)
+    n_only_rna = rna_n_before - n_intersection
+    n_only_atac = atac_n_before - n_intersection
+    kept_fraction = (n_intersection / max(rna_n_before, atac_n_before)) if max(rna_n_before, atac_n_before) else 0.0
+
+    ad_rna_aligned = ad_rna[inter].copy()
+    ad_atac_aligned = ad_atac[inter].copy()
+
+    if list(ad_rna_aligned.obs_names) != list(ad_atac_aligned.obs_names):
+        raise RuntimeError("Post-alignment orders differ between RNA and ATAC — this should not happen.")
+
+    mdata.mod[rna_key] = ad_rna_aligned
+    mdata.mod[atac_key] = ad_atac_aligned
+
+    # ---- changed: use stable content hash instead of Python's randomizing hash() ----
+    order_hash = _stable_order_hash(ad_rna_aligned.obs_names.tolist())
+
+    return AlignmentReport(
+        rna_n_before=rna_n_before,
+        atac_n_before=atac_n_before,
+        n_intersection=n_intersection,
+        n_only_rna=n_only_rna,
+        n_only_atac=n_only_atac,
+        kept_fraction=kept_fraction,
+        order_hash=order_hash,
+    )
+
+
+# ------------------------------- API ----------------------------------
+def wnn_gpu(
+    mdata: MuData,
+    modalities: Tuple[str, str] = ("rna", "atac"),
+    k: int = 15,
+    metric: str = "euclidean",
+    weight_mode: str = "local",
+    resolution: float = 1.0,
+    seed: int = 0,
+    deterministic: bool = True,
+    fp_dtype: str = "float32",
+) -> MuData:
+    """
+    Public entrypoint for the WNN pipeline (Person-1 portion only).
+    Validates input, aligns modalities, and records params + alignment report.
+    Also seeds RNG and (optionally) initializes an RMM pool for GPU runs.
+    """
+    # 0) Seeds + (optional) RMM pool — safe to do even on CPU-only setups
+    init_seeds_and_pool(seed)
+
+    # 1) Validate input
+    md = validate_mudata(mdata, modalities)
+
+    # 2) Align modalities (your core deliverable)
+    ref_key, other_key = modalities
+    report = align_modalities(md, rna_key=ref_key, atac_key=other_key)
+
+    # 3) Record parameters and alignment summary in md.uns
+    params = md.uns.setdefault("wnn_params", {})
+    params.update(
+        dict(
+            modalities=list(modalities),
+            k=k,
+            metric=metric,
+            weight_mode=weight_mode,
+            resolution=resolution,
+            seed=seed,
+            deterministic=deterministic,
+            fp_dtype=fp_dtype,
+        )
+    )
+    md.uns["wnn_alignment"] = report.to_meta()
+    md.uns.setdefault("wnn_runtime", {})  # teammates will fill timings later
+
+    # 4) Return aligned MuData
+    return md