diff --git a/scripts/sync_schema.py b/scripts/sync_schema.py
index 5aaf8e6..c922edb 100644
--- a/scripts/sync_schema.py
+++ b/scripts/sync_schema.py
@@ -100,6 +100,39 @@ def parse_fields(fields_dict: dict) -> dict[str, str]:
     return result
 
 
+def collect_lifecycle(section: dict, grouped: bool) -> tuple[set[str], set[str]]:
+    """Collect keys carrying the registry lifecycle flags.
+
+    The YAML marks two orthogonal facts (see the slicer_fields.yaml header):
+    ``deprecated`` is a consumption-side intent (stop reading this key) and
+    ``sunsetted`` is a production-side fact (no shipping SDK emits it).
+
+    *grouped* is True for property sections, which nest their entries one
+    level deeper under a type section (textual/numerical/boolean).
+    Returns ``(deprecated_keys, sunsetted_keys)``.
+    """
+    deprecated: set[str] = set()
+    sunsetted: set[str] = set()
+
+    def scan(entries: dict) -> None:
+        for key, meta in entries.items():
+            if not isinstance(meta, dict):
+                continue
+            if meta.get("deprecated"):
+                deprecated.add(key)
+            if meta.get("sunsetted"):
+                sunsetted.add(key)
+
+    if grouped:
+        for section_entries in section.values():
+            if isinstance(section_entries, dict):
+                scan(section_entries)
+    else:
+        scan(section)
+
+    return deprecated, sunsetted
+
+
 def parse_properties(properties_dict: dict) -> dict[str, str]:
     """Parse a session_properties or event_properties section.
 
@@ -143,6 +176,17 @@ def format_dict(
     return "\n".join(lines)
 
 
+def format_set(name: str, entries: set[str], indent: str = "    ") -> str:
+    """Format a set of keys as a frozenset constant declaration."""
+    if not entries:
+        return f"{name}: frozenset[str] = frozenset()"
+
+    lines = [f"{name}: frozenset[str] = frozenset({{"]
+    lines.extend(f'{indent}"{key}",' for key in sorted(entries))
+    lines.append("})")
+    return "\n".join(lines)
+
+
 def generate(yaml_path: Path) -> str:
     """Read the YAML and produce the generated module source."""
     with open(yaml_path) as f:
@@ -153,6 +197,20 @@ def generate(yaml_path: Path) -> str:
     event_fields = parse_fields(data.get("event_fields", {}))
     event_properties = parse_properties(data.get("event_properties", {}))
 
+    # Lifecycle flags across every section — session and event, fields and
+    # properties — collapsed into two flat sets of raw registry keys.
+    deprecated_keys: set[str] = set()
+    sunsetted_keys: set[str] = set()
+    for section_name, grouped in (
+        ("session_fields", False),
+        ("event_fields", False),
+        ("session_properties", True),
+        ("event_properties", True),
+    ):
+        dep, sun = collect_lifecycle(data.get(section_name, {}), grouped)
+        deprecated_keys |= dep
+        sunsetted_keys |= sun
+
     yaml_name = yaml_path.name
     yaml_hash = hashlib.sha256(yaml_path.read_bytes()).hexdigest()[:12]
 
@@ -203,6 +261,19 @@ def generate(yaml_path: Path) -> str:
         "",
         format_dict("EVENT_PROPERTY_TYPES", event_properties),
         "",
+        "",
+        "# " + "=" * 77,
+        "# LIFECYCLE FLAGS",
+        "# Raw registry keys (session + event, fields + properties) carrying",
+        '# "deprecated: true" (consumers should stop reading the key) or',
+        '# "sunsetted: true" (no shipping SDK emits it). The two compose freely.',
+        "# " + "=" * 77,
+        "",
+        format_set("DEPRECATED_KEYS", deprecated_keys),
+        "",
+        "",
+        format_set("SUNSETTED_KEYS", sunsetted_keys),
+        "",
     ]
 
     return "\n".join(sections)
diff --git a/src/cognitive3dpy/_schema.py b/src/cognitive3dpy/_schema.py
index e04c344..9e58a40 100644
--- a/src/cognitive3dpy/_schema.py
+++ b/src/cognitive3dpy/_schema.py
@@ -18,8 +18,10 @@
 import polars as pl
 
 from cognitive3dpy._schema_generated import (
+    DEPRECATED_KEYS,
     SESSION_FIELD_TYPES,
     SESSION_PROPERTY_TYPES,
+    SUNSETTED_KEYS,
 )
 from cognitive3dpy._transform import _clean_name
 
@@ -76,6 +78,12 @@
     "c3d.metrics.controller_events_score": None,
     "c3d.metrics.controller_engagement_score": None,
     "c3d.metrics.dynamic_engagement_score": None,
+    "c3d.metrics.standing_percentage":
+        "c3d.metric_components.posture_standing_percentage",
+    # Superseded by a drain *rate*, which has no single successor key —
+    # compute it from c3d.metric_components.battery_drain_sum and
+    # c3d.metric_components.battery_drain_time_millis (compact=False).
+    "c3d.metrics.battery_efficiency": None,
 }
 
 # Renamed properties: old_name → new_name (same data, new path)
@@ -106,6 +114,17 @@
 # Top-level fields that are already normalized (not c3d.* properties)
 DEPRECATED_COLUMNS["hmd"] = "c3d_device_hmd_type"
 
+# Registry lifecycle flags, normalized to column names. Unlike the curated
+# maps above these are generated from slicer_fields.yaml, so they track the
+# registry on every schema sync. Used to guard SESSIONS_COMPACT_COLUMNS
+# against drift (see tests/test_compact_columns.py).
+DEPRECATED_REGISTRY_COLUMNS: frozenset[str] = frozenset(
+    _clean_name(k) for k in DEPRECATED_KEYS
+)
+SUNSETTED_REGISTRY_COLUMNS: frozenset[str] = frozenset(
+    _clean_name(k) for k in SUNSETTED_KEYS
+)
+
 RENAMED_COLUMNS: dict[str, str] = {
     _clean_name(k): _clean_name(v)
     for k, v in RENAMED_PROPERTIES.items()
diff --git a/src/cognitive3dpy/_schema_generated.py b/src/cognitive3dpy/_schema_generated.py
index 567836d..0f14eb1 100644
--- a/src/cognitive3dpy/_schema_generated.py
+++ b/src/cognitive3dpy/_schema_generated.py
@@ -300,3 +300,64 @@
     "questionSetId": pl.Utf8,
     "hook": pl.Utf8,
 }
+
+
+# =============================================================================
+# LIFECYCLE FLAGS
+# Raw registry keys (session + event, fields + properties) carrying
+# "deprecated: true" (consumers should stop reading the key) or
+# "sunsetted: true" (no shipping SDK emits it). The two compose freely.
+# =============================================================================
+
+DEPRECATED_KEYS: frozenset[str] = frozenset({
+    "c3d.device.eyetracking.type",
+    "c3d.height",
+    "c3d.metric_components.forward_reach_score",
+    "c3d.metric_components.fps_data_point_count",
+    "c3d.metric_components.fps_data_point_sum",
+    "c3d.metric_components.horizontal_reach_score",
+    "c3d.metric_components.pitch_score",
+    "c3d.metric_components.roll_score",
+    "c3d.metric_components.vertical_reach_score",
+    "c3d.metrics.app_performance",
+    "c3d.metrics.battery_efficiency",
+    "c3d.metrics.boundary_score",
+    "c3d.metrics.controller_engagement_score",
+    "c3d.metrics.controller_ergonomic_score",
+    "c3d.metrics.controller_events_score",
+    "c3d.metrics.dynamic_engagement_score",
+    "c3d.metrics.ergonomics_score",
+    "c3d.metrics.head_orientation_score",
+    "c3d.metrics.immersion_score",
+    "c3d.metrics.orientation_score",
+    "c3d.metrics.standing_percentage",
+    "c3d.participant.hmdHeight",
+    "c3d.roomsize",
+})
+
+
+SUNSETTED_KEYS: frozenset[str] = frozenset({
+    "c3d.app.androidPlugin.hostName",
+    "c3d.app.androidPlugin.networkHostName",
+    "c3d.app.multiplayer.lobbyId",
+    "c3d.app.plugin.version",
+    "c3d.device.manufacturer",
+    "c3d.device.screenresolution",
+    "c3d.device.serial_number",
+    "c3d.device.serialnumber",
+    "c3d.headphonespresent",
+    "c3d.height",
+    "c3d.oculusId",
+    "c3d.participant.Age",
+    "c3d.participant.Color",
+    "c3d.participant.Job",
+    "c3d.participant.Sex",
+    "c3d.participant.hmdHeight",
+    "c3d.roomscale",
+    "cvr.device.graphics.memory",
+    "cvr.device.graphics.version",
+    "cvr.device.platform",
+    "cvr.vr.display.family",
+    "cvr.vr.display.model",
+    "cvr.vr.enabled",
+})
diff --git a/src/cognitive3dpy/_transform.py b/src/cognitive3dpy/_transform.py
index a324516..be25c43 100644
--- a/src/cognitive3dpy/_transform.py
+++ b/src/cognitive3dpy/_transform.py
@@ -94,11 +94,12 @@ def _clean_name(name: str) -> str:
     "c3d_roomsize_meters",
     # Key metrics (top-level scores)
     "c3d_metrics_fps_score",
+    # Registry status is deliberately "active" despite melder's deletion
+    # intent — see cvr-cortex investigations/average-fps-intended-deletion-
+    # vs-live-consumer.md. Do not drop this without revisiting that note.
     "c3d_metrics_average_fps",
     "c3d_metrics_presence_score",
     "c3d_metrics_comfort_score",
-    "c3d_metrics_battery_efficiency",
-    "c3d_metrics_standing_percentage",
     "c3d_metrics_cyberwellness_score",
     # Metric components (sub-scores)
     "c3d_metric_components_fps_score_degree_app_performance",
@@ -121,6 +122,8 @@ def _clean_name(name: str) -> str:
     "c3d_metric_components_cyberwellness_translational_movement",
     "c3d_metric_components_cyberwellness_translational_speed",
     "c3d_metric_components_cyberwellness_continuous_movement",
+    # Replaces the retired c3d.metrics.standing_percentage compute.
+    "c3d_metric_components_posture_standing_percentage",
     # Controller ergo counts
     "c3d_metric_components_controller_ergo_counts_forwards_near",
     "c3d_metric_components_controller_ergo_counts_forwards_medium",
diff --git a/tests/test_compact_columns.py b/tests/test_compact_columns.py
new file mode 100644
index 0000000..0a1ebdf
--- /dev/null
+++ b/tests/test_compact_columns.py
@@ -0,0 +1,112 @@
+"""Guard SESSIONS_COMPACT_COLUMNS against drift from the cortex registry.
+
+``SESSIONS_COMPACT_COLUMNS`` is a hand-curated list — the registry does not
+carry per-consumer presentation intent, so it cannot be generated. What the
+registry *does* carry is lifecycle state (``deprecated`` / ``sunsetted``),
+which ``sync_schema.py`` emits into ``_schema_generated.py``. These tests use
+it to fail CI when the curated list falls out of step with the registry:
+
+- a column resolves to no known field/property at all, or
+- a column resolves to a key the registry has retired.
+
+When a schema sync turns one of these red, either drop the column (following
+the deprecation convention in CLAUDE.md) or add it to
+``_LIFECYCLE_EXCEPTIONS`` with a reason.
+"""
+
+from __future__ import annotations
+
+from cognitive3dpy._schema import (
+    DEPRECATED_REGISTRY_COLUMNS,
+    SESSION_SCHEMA,
+    SUNSETTED_REGISTRY_COLUMNS,
+)
+from cognitive3dpy._transform import SESSIONS_COMPACT_COLUMNS
+
+# Compact columns with no registry key behind them. Each is produced by the
+# package or returned by the API under a name the registry does not model,
+# so the resolution check can never cover them.
+_DERIVED_COMPACT_COLUMNS: dict[str, str] = {
+    # API response fields absent from slicer_fields.yaml
+    "device_id": "API session field, not modelled in the registry",
+    "user_key": "API session field, not modelled in the registry",
+    # Data-availability flags. The registry models the ES-side plural names
+    # (hasGazes, hasEvents, ...); the list API returns these singular ones,
+    # and has_boundary has no registry counterpart at all.
+    "has_gaze": "API list-response flag; registry models hasGazes",
+    "has_fixation": "API list-response flag; registry models hasFixations",
+    "has_event": "API list-response flag; registry models hasEvents",
+    "has_dynamic": "API list-response flag; registry models hasDynamics",
+    "has_sensor": "API list-response flag; registry models hasSensors",
+    "has_boundary": "API list-response flag; no registry counterpart",
+}
+
+# Registry-retired columns deliberately kept in the compact output.
+# Key: column name. Value: why it stays.
+_LIFECYCLE_EXCEPTIONS: dict[str, str] = {}
+
+
+def test_no_duplicate_compact_columns():
+    duplicates = sorted(
+        {c for c in SESSIONS_COMPACT_COLUMNS if SESSIONS_COMPACT_COLUMNS.count(c) > 1}
+    )
+    assert not duplicates, f"Duplicate compact columns: {duplicates}"
+
+
+def test_every_compact_column_resolves():
+    """Each column maps to a schema entry or a documented derived column."""
+    unresolved = [
+        c
+        for c in SESSIONS_COMPACT_COLUMNS
+        if c not in SESSION_SCHEMA and c not in _DERIVED_COMPACT_COLUMNS
+    ]
+    assert not unresolved, (
+        f"Compact columns resolve to no known field or property: {unresolved}. "
+        "Either the name is stale, or add it to _DERIVED_COMPACT_COLUMNS "
+        "with a reason."
+    )
+
+
+def test_no_deprecated_columns_in_compact():
+    """Registry-deprecated keys must not sit in the default output."""
+    offenders = sorted(
+        (set(SESSIONS_COMPACT_COLUMNS) & DEPRECATED_REGISTRY_COLUMNS)
+        - set(_LIFECYCLE_EXCEPTIONS)
+    )
+    assert not offenders, (
+        f"Compact columns are deprecated in the registry: {offenders}. "
+        "Drop them per the deprecation convention in CLAUDE.md, or add them "
+        "to _LIFECYCLE_EXCEPTIONS with a reason."
+    )
+
+
+def test_no_sunsetted_columns_in_compact():
+    """Nothing in the default output should be a key no SDK still emits."""
+    offenders = sorted(
+        (set(SESSIONS_COMPACT_COLUMNS) & SUNSETTED_REGISTRY_COLUMNS)
+        - set(_LIFECYCLE_EXCEPTIONS)
+    )
+    assert not offenders, (
+        f"Compact columns are sunsetted in the registry: {offenders}. "
+        "Drop them, or add them to _LIFECYCLE_EXCEPTIONS with a reason."
+    )
+
+
+def test_exceptions_are_still_needed():
+    """An exception whose column is gone or no longer flagged is stale."""
+    flagged = DEPRECATED_REGISTRY_COLUMNS | SUNSETTED_REGISTRY_COLUMNS
+    stale = sorted(
+        c
+        for c in _LIFECYCLE_EXCEPTIONS
+        if c not in SESSIONS_COMPACT_COLUMNS or c not in flagged
+    )
+    assert not stale, f"Stale entries in _LIFECYCLE_EXCEPTIONS: {stale}"
+
+
+def test_deprecated_columns_have_migration_entries():
+    """Columns dropped from compact still warn via handle_deprecated_columns."""
+    from cognitive3dpy._schema import DEPRECATED_COLUMNS
+
+    for column in ("c3d_metrics_standing_percentage", "c3d_metrics_battery_efficiency"):
+        assert column not in SESSIONS_COMPACT_COLUMNS
+        assert column in DEPRECATED_COLUMNS