diff --git a/backend/app/services/wellness_parser.py b/backend/app/services/wellness_parser.py
new file mode 100644
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+++ b/backend/app/services/wellness_parser.py
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+"""
+Garmin wellness FIT file parser using the official Garmin FIT Python SDK.
+
+The official SDK (garmin-fit-sdk) correctly handles:
+- Standard FIT messages (monitoring, hrv_status_summary, sleep_level etc.)
+- Garmin proprietary messages stored by numeric mesg_num
+- Unknown fields stored by field definition number
+- Scale/offset application, component expansion, HR merging
+
+Fenix 6X proprietary message numbers identified by binary analysis:
+  55  - activity accumulation snapshots (cumulative steps, HR per interval)
+  103 - daily totals summary (total steps, floors, calories)
+  211 - resting HR + HRV summary
+  227 - per-minute stress level + heart rate (most valuable for health dashboard)
+"""
+from datetime import datetime, timezone, timedelta, date
+from typing import Optional
+
+
+FIT_EPOCH_S = 631065600  # seconds between Unix epoch and FIT epoch (Dec 31 1989)
+
+
+def fit_ts(seconds) -> Optional[datetime]:
+    """Convert FIT timestamp to UTC datetime."""
+    if seconds is None:
+        return None
+    try:
+        s = int(seconds)
+        if s == 0 or s == 0xFFFFFFFF:
+            return None
+        return datetime.fromtimestamp(s + FIT_EPOCH_S, tz=timezone.utc)
+    except (TypeError, ValueError, OverflowError, OSError):
+        return None
+
+
+def _is_datetime(v) -> bool:
+    return isinstance(v, datetime)
+
+
+def parse_wellness_fit(file_path: str) -> dict:
+    """
+    Parse a Garmin wellness/monitoring FIT file using the official Garmin SDK.
+
+    Returns {"days": {date: metrics_dict}, "error": str|None}
+    """
+    try:
+        from garmin_fit_sdk import Decoder, Stream
+    except ImportError:
+        # Fall back to fitparse-based parser if SDK not installed yet
+        from app.services.wellness_parser_fallback import parse_wellness_fit as _fb
+        return _fb(file_path)
+
+    daily = {}  # date -> aggregation dict
+
+    def ensure_day(d: date) -> dict:
+        if d not in daily:
+            daily[d] = {
+                "heart_rates": [],
+                "stress_values": [],
+                "spo2_readings": [],
+                "sleep_levels": [],
+                "steps": None,
+                "floors_climbed": None,
+                "active_calories": None,
+                "total_calories": None,
+                "resting_hr": None,
+                "hrv_nightly_avg": None,
+                "hrv_5min_high": None,
+                "hrv_status": None,
+            }
+        return daily[d]
+
+    def get_date(msg: dict, *keys) -> Optional[date]:
+        """Extract a date from a message, trying multiple field names."""
+        for key in keys:
+            v = msg.get(key)
+            if v is None:
+                continue
+            if _is_datetime(v):
+                return v.date()
+            if isinstance(v, (int, float)):
+                dt = fit_ts(v)
+                if dt:
+                    return dt.date()
+        return None
+
+    def listener(mesg_num: int, msg: dict):
+        """Called for every message after full decoding."""
+
+        # ── Standard: monitoring (148) ────────────────────────────────────
+        if mesg_num == 148:
+            d = get_date(msg, "timestamp", "local_timestamp")
+            if not d:
+                return
+            entry = ensure_day(d)
+
+            hr = msg.get("heart_rate")
+            if hr and 20 < hr < 250:
+                entry["heart_rates"].append(int(hr))
+
+            steps = msg.get("steps") or msg.get("cycles")
+            if steps and steps > 0:
+                entry["steps"] = max(entry["steps"] or 0, int(steps))
+
+            stress = msg.get("stress_level_value")
+            if stress is not None and stress >= 0:
+                entry["stress_values"].append(int(stress))
+
+        # ── Standard: monitoring_info (147) ───────────────────────────────
+        elif mesg_num == 147:
+            d = get_date(msg, "timestamp", "local_timestamp")
+            if not d:
+                return
+            rhr = msg.get("resting_heart_rate")
+            if rhr and 20 < rhr < 120:
+                ensure_day(d)["resting_hr"] = int(rhr)
+
+        # ── Standard: hrv_status_summary (275) ────────────────────────────
+        elif mesg_num == 275:
+            d = get_date(msg, "timestamp")
+            if not d:
+                return
+            entry = ensure_day(d)
+            for key in ("weekly_average", "last_night_avg", "hrv_nightly_avg"):
+                v = msg.get(key)
+                if v:
+                    entry["hrv_nightly_avg"] = float(v)
+                    break
+            high = msg.get("last_night_5_min_high")
+            if high:
+                entry["hrv_5min_high"] = float(high)
+            status = msg.get("hrv_status")
+            if status:
+                entry["hrv_status"] = str(status)
+
+        # ── Standard: stress_level (132) ──────────────────────────────────
+        elif mesg_num == 132:
+            d = get_date(msg, "stress_level_time", "timestamp")
+            if not d:
+                return
+            stress = msg.get("stress_level_value")
+            if stress is not None and stress >= 0:
+                ensure_day(d)["stress_values"].append(int(stress))
+
+        # ── Standard: spo2_data (258) ─────────────────────────────────────
+        elif mesg_num == 258:
+            d = get_date(msg, "timestamp")
+            if not d:
+                return
+            spo2 = msg.get("spo2_percent") or msg.get("reading_spo2")
+            if spo2 and 50 < spo2 <= 100:
+                ensure_day(d)["spo2_readings"].append(float(spo2))
+
+        # ── Standard: sleep_level (269) ───────────────────────────────────
+        elif mesg_num == 269:
+            d = get_date(msg, "timestamp")
+            if not d:
+                return
+            level = msg.get("sleep_level")
+            if level is not None:
+                # Convert string level names to numeric codes if SDK decoded them
+                if isinstance(level, str):
+                    level_map = {"unmeasurable": 0, "awake": 1, "light": 2, "deep": 3, "rem": 4}
+                    level = level_map.get(level.lower())
+                if level is not None:
+                    ensure_day(d)["sleep_levels"].append(int(level))
+
+        # ── Proprietary 227: per-minute stress + HR ───────────────────────
+        # field_1 = FIT timestamp, field_2 = heart rate bpm, field_0 = stress
+        elif mesg_num == 227:
+            # SDK stores unknown fields as "unknown_N" or by def_num
+            ts_raw = msg.get(1) or msg.get("unknown_1") or msg.get("field_1")
+            hr_raw = msg.get(2) or msg.get("unknown_2") or msg.get("field_2")
+            stress_raw = msg.get(0) or msg.get("unknown_0") or msg.get("field_0")
+
+            ts = fit_ts(ts_raw) if isinstance(ts_raw, (int, float)) else (
+                ts_raw if _is_datetime(ts_raw) else None
+            )
+            if not ts:
+                return
+            entry = ensure_day(ts.date())
+
+            if hr_raw and isinstance(hr_raw, (int, float)) and 20 < hr_raw < 250:
+                entry["heart_rates"].append(int(hr_raw))
+
+            if stress_raw is not None and isinstance(stress_raw, (int, float)) and stress_raw >= 0:
+                entry["stress_values"].append(int(stress_raw))
+
+        # ── Proprietary 103: daily totals summary ─────────────────────────
+        # field_253 = timestamp, field_3 = steps, field_4 = floors, field_5/7 = cal
+        elif mesg_num == 103:
+            ts_v = msg.get(253) or msg.get("timestamp")
+            ts = ts_v if _is_datetime(ts_v) else fit_ts(ts_v)
+            if not ts:
+                return
+            entry = ensure_day(ts.date())
+
+            steps = msg.get(3)
+            if steps and isinstance(steps, (int, float)) and steps > 0:
+                entry["steps"] = int(steps)
+
+            floors = msg.get(4)
+            if floors and isinstance(floors, (int, float)) and floors > 0:
+                f = float(floors)
+                if f > 1000:
+                    f = f / 100
+                entry["floors_climbed"] = round(f, 1)
+
+            active_cal = msg.get(5)
+            if active_cal and isinstance(active_cal, (int, float)) and active_cal > 0:
+                entry["active_calories"] = float(active_cal)
+
+            total_cal = msg.get(7)
+            if total_cal and isinstance(total_cal, (int, float)) and total_cal > 0:
+                entry["total_calories"] = float(total_cal)
+
+        # ── Proprietary 211: resting HR + HRV summary ─────────────────────
+        elif mesg_num == 211:
+            ts_v = msg.get(253) or msg.get("timestamp")
+            ts = ts_v if _is_datetime(ts_v) else fit_ts(ts_v)
+            if not ts:
+                return
+            entry = ensure_day(ts.date())
+
+            rhr = msg.get(0)
+            if rhr and isinstance(rhr, (int, float)) and 20 < rhr < 120:
+                entry["resting_hr"] = int(rhr)
+
+            hrv = msg.get(1)
+            if hrv and isinstance(hrv, (int, float)) and 5 < hrv < 300:
+                entry["hrv_nightly_avg"] = float(hrv)
+
+        # ── Proprietary 55: activity accumulation snapshots ───────────────
+        elif mesg_num == 55:
+            ts_v = msg.get(253) or msg.get("timestamp")
+            ts = ts_v if _is_datetime(ts_v) else fit_ts(ts_v)
+            if not ts:
+                return
+            entry = ensure_day(ts.date())
+
+            steps = msg.get(2)
+            if steps and isinstance(steps, (int, float)) and steps > 0:
+                entry["steps"] = max(entry["steps"] or 0, int(steps))
+
+            hr = msg.get(19)
+            if hr and isinstance(hr, (int, float)) and 20 < hr < 250:
+                entry["heart_rates"].append(int(hr))
+
+    # Decode the file
+    try:
+        stream = Stream.from_file(file_path)
+        decoder = Decoder(stream)
+        messages, errors = decoder.read(
+            apply_scale_and_offset=True,
+            convert_datetimes_to_dates=True,
+            convert_types_to_strings=True,
+            enable_crc_check=False,   # wellness files sometimes have bad CRCs
+            expand_sub_fields=True,
+            expand_components=True,
+            merge_heart_rates=True,
+            mesg_listener=listener,
+        )
+    except Exception as e:
+        return {"error": str(e), "days": {}}
+
+    # Aggregate per-day
+    result = {}
+    for day_date, data in daily.items():
+        hrs = data.pop("heart_rates", [])
+        stresses = data.pop("stress_values", [])
+        spo2s = data.pop("spo2_readings", [])
+        sleep_levels = data.pop("sleep_levels", [])
+
+        avg_hr = round(sum(hrs) / len(hrs), 1) if hrs else None
+        max_hr = max(hrs) if hrs else None
+        avg_stress = round(sum(s for s in stresses if s >= 0) / len(stresses), 1) if stresses else None
+        spo2_avg = round(sum(spo2s) / len(spo2s), 1) if spo2s else None
+
+        # Sleep stage seconds (each level record = 30s epoch)
+        if sleep_levels:
+            sleep_deep_s = sum(30 for l in sleep_levels if l == 3) or None
+            sleep_light_s = sum(30 for l in sleep_levels if l == 2) or None
+            sleep_rem_s = sum(30 for l in sleep_levels if l == 4) or None
+            sleep_awake_s = sum(30 for l in sleep_levels if l == 1) or None
+            sleep_duration_s = (sleep_deep_s or 0) + (sleep_light_s or 0) + (sleep_rem_s or 0) or None
+        else:
+            sleep_deep_s = sleep_light_s = sleep_rem_s = sleep_awake_s = sleep_duration_s = None
+
+        result[day_date] = {
+            "resting_hr": data.get("resting_hr"),
+            "avg_hr_day": avg_hr,
+            "max_hr_day": max_hr,
+            "avg_stress": avg_stress,
+            "spo2_avg": spo2_avg,
+            "hrv_nightly_avg": data.get("hrv_nightly_avg"),
+            "hrv_5min_high": data.get("hrv_5min_high"),
+            "hrv_status": data.get("hrv_status"),
+            "steps": data.get("steps"),
+            "floors_climbed": data.get("floors_climbed"),
+            "active_calories": data.get("active_calories"),
+            "total_calories": data.get("total_calories"),
+            "sleep_duration_s": sleep_duration_s,
+            "sleep_deep_s": sleep_deep_s,
+            "sleep_light_s": sleep_light_s,
+            "sleep_rem_s": sleep_rem_s,
+            "sleep_awake_s": sleep_awake_s,
+        }
+
+    return {"days": result, "error": None}
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