diff --git a/decision_mapper.py b/decision_mapper.py
index 105d12f..9190e2f 100644
--- a/decision_mapper.py
+++ b/decision_mapper.py
@@ -21,6 +21,17 @@
 _INCOME_SYMBOLS = frozenset({"QQQI", "SPYI"})
 _DEFAULT_MIN_TRADE_FLOOR = 100.0
 _DEFAULT_REBALANCE_THRESHOLD_RATIO = 0.01
+_SNAPSHOT_DIAGNOSTIC_FIELDS = (
+    "snapshot_manifest_price_as_of",
+    "snapshot_manifest_universe_as_of",
+    "snapshot_manifest_source_input_status",
+    "snapshot_manifest_source_input_fallback_used",
+    "snapshot_manifest_source_input_fallback_reason",
+    "snapshot_manifest_source_input_fallback_streak",
+    "snapshot_manifest_source_input_manifest_path",
+    "snapshot_manifest_source_refresh_run_id",
+    "snapshot_manifest_source_refresh_generated_at",
+)
 
 
 def _build_portfolio_inputs(
@@ -106,6 +117,22 @@ def _resolve_platform_reserved_cash(
     return max(reserved_cash_floor_usd, max(0.0, float(total_equity)) * reserved_cash_ratio)
 
 
+def _attach_snapshot_diagnostics(
+    plan: dict[str, Any],
+    *,
+    decision: StrategyDecision,
+    runtime_metadata: Mapping[str, Any] | None,
+) -> None:
+    execution = plan.get("execution")
+    if not isinstance(execution, dict):
+        return
+    diagnostics = {**dict(runtime_metadata or {}), **dict(decision.diagnostics)}
+    for field in _SNAPSHOT_DIAGNOSTIC_FIELDS:
+        value = diagnostics.get(field)
+        if value is not None and value != "":
+            execution[field] = value
+
+
 def _apply_reserved_cash_policy(
     annotations: ValueTargetExecutionAnnotations,
     *,
@@ -498,4 +525,9 @@ def map_strategy_decision_to_plan(
         cash_by_currency = _cash_by_currency_from_snapshot(snapshot)
     if cash_by_currency:
         plan["portfolio"]["cash_by_currency"] = cash_by_currency
+    _attach_snapshot_diagnostics(
+        plan,
+        decision=normalized_decision,
+        runtime_metadata=runtime_metadata,
+    )
     return plan
diff --git a/tests/test_decision_mapper.py b/tests/test_decision_mapper.py
index 2214285..39ae5fc 100644
--- a/tests/test_decision_mapper.py
+++ b/tests/test_decision_mapper.py
@@ -212,6 +212,41 @@ def test_applies_platform_reserved_cash_policy_to_weight_decision(self):
         self.assertEqual(plan["execution"]["reserved_cash"], 1500.0)
         self.assertEqual(plan["execution"]["investable_cash"], 2500.0)
 
+    def test_carries_snapshot_manifest_diagnostics_to_execution(self):
+        decision = StrategyDecision(
+            positions=(),
+            risk_flags=("no_execute",),
+            diagnostics={"signal_description": "monthly cadence"},
+        )
+        snapshot = PortfolioSnapshot(
+            as_of=datetime.now(timezone.utc),
+            total_equity=10000.0,
+            buying_power=10000.0,
+            positions=(),
+            metadata={"account_hash": "longbridge-snapshot"},
+        )
+
+        plan = map_strategy_decision_to_plan(
+            decision,
+            snapshot=snapshot,
+            strategy_profile="mega_cap_leader_rotation_top50_balanced",
+            runtime_metadata={
+                "snapshot_manifest_price_as_of": "2026-06-01",
+                "snapshot_manifest_universe_as_of": "2026-04-29",
+                "snapshot_manifest_source_input_status": "universe_fallback",
+                "snapshot_manifest_source_input_fallback_used": True,
+                "snapshot_manifest_source_input_fallback_streak": 1,
+                "snapshot_manifest_source_refresh_run_id": "26785047433",
+            },
+        )
+
+        self.assertEqual(plan["execution"]["snapshot_manifest_price_as_of"], "2026-06-01")
+        self.assertEqual(plan["execution"]["snapshot_manifest_universe_as_of"], "2026-04-29")
+        self.assertEqual(plan["execution"]["snapshot_manifest_source_input_status"], "universe_fallback")
+        self.assertIs(plan["execution"]["snapshot_manifest_source_input_fallback_used"], True)
+        self.assertEqual(plan["execution"]["snapshot_manifest_source_input_fallback_streak"], 1)
+        self.assertEqual(plan["execution"]["snapshot_manifest_source_refresh_run_id"], "26785047433")
+
     def test_platform_reserved_cash_policy_does_not_lower_strategy_reserve(self):
         decision = StrategyDecision(
             positions=(PositionTarget(symbol="TQQQ", target_value=5000.0),),