diff --git a/gravityweave/dtn.py b/gravityweave/dtn.py
new file mode 100644
index 0000000..55621c7
--- /dev/null
+++ b/gravityweave/dtn.py
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+"""DTN custody header and simple custody policy helpers.
+
+This module provides a minimal CustodyHeader dataclass used by DTN custody
+holders to make decisions about storing/transferring PlanDelta payloads.
+It also exposes a small helper that decides whether to accept custody based
+on priority, remaining lifetime, and a node reputation score.
+
+The implementation is intentionally small and deterministic for unit testing.
+"""
+from dataclasses import dataclass, field
+from typing import List
+import time
+
+
+@dataclass
+class CustodyHeader:
+    delta_id: str
+    created_at: float = field(default_factory=time.time)
+    lifetime_secs: int = 3600  # how long the custody is expected to be valid
+    custody_chain: List[str] = field(default_factory=list)
+    priority_key: int = 0  # combined urgency/impact key (0..127)
+
+    def is_expired(self, now: float = None) -> bool:
+        if now is None:
+            now = time.time()
+        return now > (self.created_at + self.lifetime_secs)
+
+    def add_holder(self, node_id: str):
+        # append to custody chain (no dedupe to keep deterministic append-only)
+        self.custody_chain.append(node_id)
+
+
+def should_accept_custody(header: CustodyHeader, node_reputation: float, min_reputation: float = 0.2) -> bool:
+    """Decide whether a node should accept custody for a delta.
+
+    Decision factors (simple heuristic):
+    - If the header is already expired, refuse custody.
+    - Prefer accepting higher priority_key values.
+    - Gate acceptance by a minimum reputation threshold.
+
+    Returns True if the node should accept custody.
+    """
+    if header.is_expired():
+        return False
+
+    # Enforce a minimum reputation gate: nodes below min_reputation refuse custody
+    if node_reputation < min_reputation:
+        return False
+
+    # decode urgency and impact from priority_key (urgency<<4)|impact
+    urgency = (header.priority_key >> 4) & 0x07
+    impact = header.priority_key & 0x0F
+
+    # compute a simple desirability score
+    score = urgency * 2 + impact + (node_reputation * 4)
+
+    # threshold depends on min_reputation; higher min_reputation raises bar
+    threshold = 5.0 + (1.0 - min_reputation) * 3.0
+    return score >= threshold
diff --git a/tests/test_dtn.py b/tests/test_dtn.py
new file mode 100644
index 0000000..e797ef6
--- /dev/null
+++ b/tests/test_dtn.py
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+from gravityweave.dtn import CustodyHeader, should_accept_custody
+import time
+
+
+def test_custody_header_and_expiry():
+    h = CustodyHeader(delta_id="d1", lifetime_secs=1)
+    assert not h.is_expired()
+    # wait for expiry
+    time.sleep(1.1)
+    assert h.is_expired()
+
+
+def test_should_accept_custody():
+    # fresh header with medium priority
+    h = CustodyHeader(delta_id="d2", lifetime_secs=60, priority_key=(2 << 4) | 8)
+    # low reputation should often reject
+    assert not should_accept_custody(h, node_reputation=0.0, min_reputation=0.2)
+    # decent reputation should accept
+    assert should_accept_custody(h, node_reputation=0.8, min_reputation=0.2)