diff --git a/drift_data_collection/src/drift_data_collection/core.py b/drift_data_collection/src/drift_data_collection/core.py
new file mode 100644
index 0000000..2a047e6
--- /dev/null
+++ b/drift_data_collection/src/drift_data_collection/core.py
@@ -0,0 +1,105 @@
+import json
+import logging
+from datetime import datetime
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+import requests
+
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.INFO)
+
+
+class DataCollectionError(Exception):
+    """Custom exception for errors during data collection."""
+
+
+class FrozenRun:
+    """Represents frozen CI run data for drift analysis."""
+
+    def __init__(self, run_id: str, status: str, timestamp: datetime, pinned_state: bool, metrics: str) -> None:
+        self.run_id = run_id
+        self.status = status
+        self.timestamp = timestamp
+        self.pinned_state = pinned_state
+        self.metrics = metrics
+
+    def to_dict(self) -> Dict[str, Any]:
+        return {
+            "run_id": self.run_id,
+            "status": self.status,
+            "timestamp": self.timestamp.isoformat(),
+            "pinned_state": self.pinned_state,
+            "metrics": self.metrics,
+        }
+
+
+def _validate_run_ids(run_ids: List[str]) -> None:
+    if not isinstance(run_ids, list):
+        raise ValueError("run_ids must be a list of strings.")
+    for rid in run_ids:
+        if not isinstance(rid, str) or not rid.strip():
+            raise ValueError(f"Invalid run_id: {rid!r}")
+
+
+def _fetch_run_data(run_id: str) -> Optional[FrozenRun]:
+    """Fetch run data; fallback to simulated local info if retrieval fails."""
+    try:
+        # Placeholder endpoint, could be replaced with local file lookup or API
+        response = requests.get(f"https://ci.example.com/api/runs/{run_id}", timeout=5)
+        if response.status_code != 200:
+            logger.warning("Run %s returned HTTP %s", run_id, response.status_code)
+            return None
+        data = response.json()
+        ts_str = data.get("timestamp")
+        try:
+            timestamp = datetime.fromisoformat(ts_str) if ts_str else datetime.utcnow()
+        except ValueError:
+            timestamp = datetime.utcnow()
+        return FrozenRun(
+            run_id=data.get("run_id", run_id),
+            status=data.get("status", "UNKNOWN"),
+            timestamp=timestamp,
+            pinned_state=bool(data.get("pinned_state", False)),
+            metrics=json.dumps(data.get("metrics", {})),
+        )
+    except requests.RequestException as e:
+        logger.error("Network error collecting run %s: %s", run_id, e)
+        return None
+    except Exception as e:
+        logger.exception("Unexpected error fetching run %s: %s", run_id, e)
+        return None
+
+
+def collect_frozen_runs(run_ids: List[str]) -> List[Dict[str, Any]]:
+    """Collect and aggregate frozen run data for given run IDs.
+
+    Args:
+        run_ids: List of run IDs to collect.
+
+    Returns:
+        List of dictionaries containing frozen run data.
+    """
+    _validate_run_ids(run_ids)
+
+    collected: List[Dict[str, Any]] = []
+    for rid in run_ids:
+        run = _fetch_run_data(rid)
+        if run:
+            collected.append(run.to_dict())
+        else:
+            # Build default entry if missing
+            logger.info("Using fallback data for run %s", rid)
+            collected.append(
+                FrozenRun(
+                    run_id=rid,
+                    status="MISSING",
+                    timestamp=datetime.utcnow(),
+                    pinned_state=False,
+                    metrics="{}",
+                ).to_dict()
+            )
+
+    assert all("run_id" in r for r in collected), "Integrity check failed: missing run_id"
+    return collected