From 0a1bb68808ceab4231a5508496bc20c1601d7e73 Mon Sep 17 00:00:00 2001
From: Bryan Van Deusen <bryan.vandeusen@fabledsword.com>
Date: Sat, 3 Oct 2026 08:49:20 -0400
Subject: [PATCH] =?UTF-8?q?feat(rulings):=20system=5Fusage=5Fevents=20is?=
 =?UTF-8?q?=20read=20back=20=E2=80=94=20per-System=20counts=20and=20a=20te?=
 =?UTF-8?q?lemetry=20block=20(#4769)?=
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Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

#4769 "Rulings are counted where someone will read them": milestone 444
step 4 wrote system_usage_events and nothing read it.

- retrieval_telemetry gains a `system_usage` block: surfacings and opens by
  source, distinct counts, and `by_system` naming the areas most shown.
  There is deliberately no pull-through ratio, because rulings travel in full
  in the line and opens are the exception.
- usage_for_systems (one GROUP BY) adds `usage` to the REST Systems list and
  detail, and to MCP get_system. MCP list_systems is unchanged.
- The Systems UI shows a "rulings shown N×" chip.
- rulings_pre_tool, rulings_write_path and mcp_get_system are now declared
  registry points; the registry guard covers their recorders.
- The Systems store merges a PATCH reply instead of replacing the row.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 frontend/src/api/systems.ts                |   8 +
 frontend/src/components/SystemsSection.vue |  25 ++++
 frontend/src/stores/systems.ts             |   5 +-
 src/scribe/mcp/tools/search.py             |  12 +-
 src/scribe/mcp/tools/systems.py            |   9 +-
 src/scribe/routes/systems.py               |   6 +
 src/scribe/services/retrieval_registry.py  |  24 +++
 src/scribe/services/retrieval_telemetry.py | 121 +++++++++++++++-
 src/scribe/services/system_usage.py        |  67 +++++++++
 tests/conftest.py                          |  20 +++
 tests/test_retrieval_registry.py           |   3 +
 tests/test_system_usage_readout.py         | 161 +++++++++++++++++++++
 12 files changed, 457 insertions(+), 4 deletions(-)
 create mode 100644 tests/test_system_usage_readout.py

diff --git a/frontend/src/api/systems.ts b/frontend/src/api/systems.ts
index 7d19ed1..3b75050 100644
--- a/frontend/src/api/systems.ts
+++ b/frontend/src/api/systems.ts
@@ -1,5 +1,6 @@
 import { apiGet, apiPost, apiPatch, apiDelete } from "@/api/client";
 import type { CanonicalMatch } from "@/api/canonicalSystems";
+import type { RecordUsage } from "@/types/usage";
 
 export interface System {
   id: number;
@@ -21,6 +22,13 @@ export interface System {
    */
   path_patterns: string[];
   open_issue_count: number;
+  /**
+   * How often this area's rulings were shown to a session because its files
+   * were touched (`surfaced_count`), and how often it was opened (#4769).
+   * Present on the list and detail reads; optional because a System returned
+   * by a create or update carries none.
+   */
+  usage?: RecordUsage;
   created_at: string | null;
   updated_at: string | null;
 }
diff --git a/frontend/src/components/SystemsSection.vue b/frontend/src/components/SystemsSection.vue
index f69fffd..7171436 100644
--- a/frontend/src/components/SystemsSection.vue
+++ b/frontend/src/components/SystemsSection.vue
@@ -7,6 +7,7 @@ import { getProjectIssues } from "@/api/systems";
 import type { System, TaskLike } from "@/api/systems";
 import type { CanonicalMatch } from "@/api/canonicalSystems";
 import { apiErrorMessage } from "@/api/client";
+import { fmtDate } from "@/utils/dateFormat";
 import { Pencil, Trash2, Archive, ArchiveRestore } from "lucide-vue-next";
 
 const props = defineProps<{ projectId: number }>();
@@ -71,6 +72,25 @@ function areaName(system: System): string | null {
   return canon.byId(system.canonical_id)?.name ?? null;
 }
 
+/** How many times this area's rulings reached a session (#4769). Not the
+ *  UsageBadge: its "N/M used" reads opens over showings, and rulings are
+ *  delivered in full in the line, so an unopened System is the arm working,
+ *  not dead weight. */
+function rulingsShown(system: System): number {
+  return system.usage?.surfaced_count ?? 0;
+}
+
+function rulingsTitle(system: System): string {
+  const u = system.usage;
+  if (!u) return "";
+  const last = u.last_surfaced_at ? ` Last shown ${fmtDate(u.last_surfaced_at)}.` : "";
+  return (
+    `This area's rulings were shown in full to a session ${u.surfaced_count}×, ` +
+    `when a command or edit touched its files.${last} ` +
+    `Opened with get_system ${u.pull_count}×.`
+  );
+}
+
 async function load() {
   error.value = null;
   try {
@@ -471,6 +491,11 @@ async function confirmDelete() {
                 class="area-chip"
                 :title="`Filed under the shared area “${areaName(system)}” — records and rules about this area line up across projects.`"
               >{{ areaName(system) }}</span>
+              <span
+                v-if="rulingsShown(system)"
+                class="usage-tag"
+                :title="rulingsTitle(system)"
+              >rulings shown {{ rulingsShown(system) }}×</span>
             </div>
             <p v-if="system.description" class="system-description">{{ system.description }}</p>
             <ul v-if="system.path_patterns.length" class="system-paths" aria-label="Files">
diff --git a/frontend/src/stores/systems.ts b/frontend/src/stores/systems.ts
index 6e2c318..b8aee46 100644
--- a/frontend/src/stores/systems.ts
+++ b/frontend/src/stores/systems.ts
@@ -39,7 +39,10 @@ export const useSystemsStore = defineStore("systems", () => {
     const list = systemsByProject.value[projectId];
     if (list) {
       const idx = list.findIndex((s) => s.id === systemId);
-      if (idx >= 0) list[idx] = system;
+      // Merged, not replaced: the PATCH reply is the bare System, and the
+      // list's read-side decorations (issue count, rulings usage) would
+      // otherwise vanish from the row until the next reload.
+      if (idx >= 0) list[idx] = { ...list[idx], ...system };
     }
     return system;
   }
diff --git a/src/scribe/mcp/tools/search.py b/src/scribe/mcp/tools/search.py
index 2ffc329..129e397 100644
--- a/src/scribe/mcp/tools/search.py
+++ b/src/scribe/mcp/tools/search.py
@@ -380,7 +380,7 @@ async def retrieval_telemetry(
     — so `near_miss_samples=5` and opening the ids it returns is the step that
     separates a real miss from a bar doing its job.
 
-    Three readouts, from the three tables built for them:
+    Four readouts, from the four tables built for them:
 
     `sources` — per retrieval surface (`auto_inject`, `write_path`,
     `mcp_search`, …), from `retrieval_logs`: `calls`, `zero_result_calls`,
@@ -529,6 +529,16 @@ It is an UPPER BOUND per surface: a pull records the door it came
     the zeros were missing rather than absent (#3497). Measured since, it
     declines the large majority of its calls like any other surface.
 
+    `system_usage` — the RULINGS arm (#4769), from `system_usage_events`: how
+    often an area's rulings were shown because a command (`rulings_pre_tool`)
+    or an edit (`rulings_write_path`) touched its files, how often a System
+    was then opened (`mcp_get_system`), and `by_system` naming the areas, most
+    shown first. A lookup, not a ranker, so it has no row in `sources` and no
+    floor to tune. And NO `pull_through`, on purpose: the rulings travel in
+    full in the line, so a session reads them without opening anything, and
+    a ratio of opens would read near zero on an arm that is working.
+    `system_usage_failed: true` means its read broke and the zeros mean nothing.
+
     EVERY COUNTER BLOCK CARRIES ITS OWN COVERAGE — `complete_from` and
     `covers_window`. `complete_from` is when the number became trustworthy:
     for one source, its first recorded row; for a section that sums several,
diff --git a/src/scribe/mcp/tools/systems.py b/src/scribe/mcp/tools/systems.py
index 8b2dab7..dc09010 100644
--- a/src/scribe/mcp/tools/systems.py
+++ b/src/scribe/mcp/tools/systems.py
@@ -18,6 +18,7 @@ from scribe.services import canonical_systems as canonical_systems_svc
 from scribe.services import milestones as milestones_svc
 from scribe.services import notes as notes_svc
 from scribe.services import systems as systems_svc
+from scribe.services import system_usage as system_usage_svc
 from scribe.services.system_usage import record_system_pulled
 
 # Below this, a project is young enough that the mild "which area is this
@@ -288,7 +289,9 @@ async def get_system(system_id: int) -> dict:
 
     Returns the system, plus its associated records split into `issues`,
     `tasks` (work/plan), and `notes` — each saying what the record is and where
-    it sits, not what it says (open one with get_note / get_task).
+    it sits, not what it says (open one with get_note / get_task) — and
+    `usage`: how many times its rulings were shown to a session because its
+    files were touched (`surfaced_count`), and how many times it was opened.
     """
     uid = current_user_id()
     system = await systems_svc.get_system(uid, system_id)
@@ -312,6 +315,10 @@ async def get_system(system_id: int) -> dict:
     data["issues"] = issues
     data["tasks"] = tasks
     data["notes"] = notes
+    # How often this area's rulings were shown to a session and the System
+    # opened (#4769). Here and not on list_systems: one lookup on a read that
+    # asked for the System, rather than a column on every project handshake.
+    data["usage"] = (await system_usage_svc.usage_for_systems([system.id]))[system.id]
     return data
 
 
diff --git a/src/scribe/routes/systems.py b/src/scribe/routes/systems.py
index 7021d09..75cb1b3 100644
--- a/src/scribe/routes/systems.py
+++ b/src/scribe/routes/systems.py
@@ -10,6 +10,7 @@ from scribe.routes.utils import not_found
 from scribe.services import systems as systems_svc
 from scribe.services.access import can_write_project
 from scribe.services.projects import get_project_for_user
+from scribe.services import system_usage as system_usage_svc
 
 logger = logging.getLogger(__name__)
 
@@ -43,10 +44,14 @@ async def list_systems_route(project_id: int):
         uid, project_id, include_archived=_truthy(request.args.get("include_archived")),
     )
     counts = await systems_svc.open_issue_counts_by_system(uid, project_id)
+    # How often each area's rulings reached a session (#4769) — one GROUP BY
+    # for the page, and a zero shape for an area nothing has touched.
+    usage = await system_usage_svc.usage_for_systems([s.id for s in systems])
     out = []
     for s in systems:
         d = s.to_dict()
         d["open_issue_count"] = counts.get(s.id, 0)
+        d["usage"] = usage.get(s.id, system_usage_svc.empty_system_usage())
         out.append(d)
     return jsonify({"systems": out})
 
@@ -114,6 +119,7 @@ async def get_system_route(project_id: int, system_id: int):
     )
     data = system.to_dict()
     data["issues"], data["tasks"], data["notes"] = issues, tasks, notes
+    data["usage"] = (await system_usage_svc.usage_for_systems([system.id]))[system.id]
     return jsonify(data)
 
 
diff --git a/src/scribe/services/retrieval_registry.py b/src/scribe/services/retrieval_registry.py
index 31c30a7..5b2c02c 100644
--- a/src/scribe/services/retrieval_registry.py
+++ b/src/scribe/services/retrieval_registry.py
@@ -151,6 +151,23 @@ POINTS: dict[str, Point] = dict([
        "the fixed question asked when a task finishes: how should this report read",
        fixed_query=True),
 
+    # The rulings arm (milestone 444). A LOOKUP, not a ranker: a path falls
+    # under a System's patterns or it does not, so nothing here writes to
+    # retrieval_logs and no score-shaped warning can apply. Its rows are in
+    # `system_usage_events`, read back as `retrieval_telemetry`'s
+    # `system_usage` block (#4769).
+    _p("rulings_pre_tool", UNBIDDEN,
+       "an area's rulings, shown because a command touched its files",
+       expects_traffic=False,
+       quiet_because="speaks only once a System has both path_patterns and a "
+                     "Rulings section; an install where none does is "
+                     "correctly silent here"),
+    _p("rulings_write_path", UNBIDDEN,
+       "an area's rulings, shown because an edit touched its files",
+       expects_traffic=False,
+       quiet_because="same as rulings_pre_tool — no System with patterns "
+                     "and rulings, nothing to show"),
+
     # ── Asked: a caller wanted a ranked list ─────────────────────────────
     _p("mcp_search", ASKED, "an agent called search"),
     _p("wide_net", ASKED, "an agent asked what might apply, with no bar"),
@@ -186,6 +203,10 @@ POINTS: dict[str, Point] = dict([
     _p("mcp_get_process", PULL, "an agent opened a process"),
     _p("mcp_get_lesson", PULL, "an agent opened a lesson"),
     _p("mcp_get_rule", PULL, "an agent opened a rule"),
+    _p("mcp_get_system", PULL, "an agent opened a System", expects_traffic=False,
+       quiet_because="a System's rulings arrive in full in the rulings line, "
+                     "so opening one is the exception rather than the "
+                     "measure; a window without it is not a gap"),
     _p("rest_note", PULL, "a person opened a note", expects_traffic=False,
        quiet_because="web UI only"),
     _p("rest_task", PULL, "a person opened a task", expects_traffic=False,
@@ -220,6 +241,9 @@ FAN_OUT_SITES: dict[str, tuple[str, ...]] = {
     "scribe/services/plugin_context.py::record_surfaced(source=arm)": (
         "write_path_place", "write_path_semantic", "write_path_sync",
     ),
+    "scribe/services/system_rulings.py::record_system_surfaced(source=source)": (
+        "rulings_pre_tool", "rulings_write_path",
+    ),
     "scribe/services/rulebooks.py::record_rule_surfaced(source=source)": (
         "enter_project", "start_planning", "get_task", "get_project",
         "get_milestone",
diff --git a/src/scribe/services/retrieval_telemetry.py b/src/scribe/services/retrieval_telemetry.py
index 7667f11..2e1f8be 100644
--- a/src/scribe/services/retrieval_telemetry.py
+++ b/src/scribe/services/retrieval_telemetry.py
@@ -34,6 +34,10 @@ from scribe.models.rule_usage import DEPARTED as RULE_DEPARTED
 from scribe.models.rule_usage import PULLED as RULE_PULLED
 from scribe.models.rule_usage import SURFACED as RULE_SURFACED
 from scribe.models.rule_usage import RuleUsageEvent
+from scribe.models.system import System
+from scribe.models.system_usage import PULLED as SYSTEM_PULLED
+from scribe.models.system_usage import SURFACED as SYSTEM_SURFACED
+from scribe.models.system_usage import SystemUsageEvent
 from scribe.services.rule_usage import is_ambient
 from scribe.models.retrieval_log import RetrievalLog
 from scribe.services.retrieval_registry import (
@@ -817,7 +821,7 @@ def _compute_warnings(sources: dict, usage: dict, rule_usage: dict,
 
 
 def _silent_surfaces(sources: dict, usage: dict, rule_usage: dict,
-                     active: bool) -> list[dict]:
+                     active: bool, system_usage: dict | None = None) -> list[dict]:
     """Registered points that emitted nothing at all in the window.
 
     THE HALF THE ROWS CANNOT SEE. Every check above reads rows, so an arm that
@@ -834,12 +838,124 @@ def _silent_surfaces(sources: dict, usage: dict, rule_usage: dict,
         return []
     seen = set(sources) | set((usage.get("by_source") or {}))
     seen |= set((rule_usage.get("by_source") or {}))
+    seen |= set(((system_usage or {}).get("by_source") or {}))
     return [
         {"source": s, "kind": POINTS[s].kind, "what": POINTS[s].what}
         for s in sources_expected_to_emit() if s not in seen
     ]
 
 
+# How many Systems `by_system` lists. A readout of which AREAS' rulings are
+# reaching sessions, not an export: an install with more ruled areas than this
+# reads the rest from the per-System counts on the Systems list.
+SYSTEM_USAGE_TOP = 20
+
+
+async def _system_usage(user_id: int | None, since) -> dict:
+    """The rulings arm's own block (#4769): were an area's rulings shown, and
+    was the area then opened.
+
+    FROM `system_usage_events`, IN ITS OWN SESSION AND ITS OWN GUARD, for the
+    reason the rule block is guarded apart: a failure here must not take down
+    the readouts beside it, and must say so rather than print zeros (#2663) —
+    the keys are kept and `system_usage_failed` is added.
+
+    NO PULL-THROUGH, and the omission is the design. The note and rule ratios
+    ask "was the hint any use" of a line that carries a TITLE, where opening
+    the record is how it gets read. A rulings line carries the rulings
+    themselves; the agent reads them without opening anything, and
+    `get_system` is reached for only when a long list was cut ("+N more").
+    A ratio here would read near zero on an arm that is working, and invite
+    the dead-weight verdict the per-record badges give — the wrong conclusion,
+    built from a true number. The counts are printed side by side instead.
+
+    `by_system` names the areas, because "rulings were shown 40 times" says
+    nothing a reader can act on, and "Billing, 38 of them" does.
+    Ordered by surfacings, then by name, so a stable window reads stably.
+    """
+    block: dict = {
+        "surfaced": 0,
+        "pulled": 0,
+        "distinct_systems_surfaced": 0,
+        "distinct_systems_pulled": 0,
+        "by_source": {},
+        "by_system": [],
+    }
+    try:
+        async with async_session() as session:
+            where = (
+                SystemUsageEvent.created_at >= since,
+                SystemUsageEvent.user_id == user_id,
+            )
+            per_source = (
+                await session.execute(
+                    select(
+                        SystemUsageEvent.event,
+                        SystemUsageEvent.source,
+                        func.count().label("n"),
+                    )
+                    .where(*where)
+                    .group_by(SystemUsageEvent.event, SystemUsageEvent.source)
+                )
+            ).all()
+            per_system = (
+                await session.execute(
+                    select(
+                        SystemUsageEvent.system_id,
+                        System.name,
+                        SystemUsageEvent.event,
+                        func.count().label("n"),
+                        func.max(SystemUsageEvent.created_at).label("last_at"),
+                    )
+                    # Outer: telemetry outlives the row it describes, and a
+                    # deleted System's surfacings still happened.
+                    .outerjoin(System, System.id == SystemUsageEvent.system_id)
+                    .where(*where)
+                    .group_by(
+                        SystemUsageEvent.system_id, System.name,
+                        SystemUsageEvent.event,
+                    )
+                )
+            ).all()
+            complete = await _complete_from(session, SystemUsageEvent, user_id)
+    except Exception:
+        logger.warning("system usage read failed", exc_info=True)
+        block["system_usage_failed"] = True
+        return block
+
+    for event, source, n in per_source:
+        n = int(n)
+        key = "surfaced" if event == SYSTEM_SURFACED else (
+            "pulled" if event == SYSTEM_PULLED else None)
+        if key is None:
+            continue
+        block[key] += n
+        block["by_source"][source] = block["by_source"].get(source, 0) + n
+
+    systems: dict[int, dict] = {}
+    for system_id, name, event, n, last_at in per_system:
+        row = systems.setdefault(int(system_id), {
+            "system_id": int(system_id),
+            "name": name,
+            "surfaced": 0,
+            "pulled": 0,
+            "last_surfaced_at": None,
+        })
+        if event == SYSTEM_SURFACED:
+            row["surfaced"] += int(n)
+            row["last_surfaced_at"] = iso(last_at)
+        elif event == SYSTEM_PULLED:
+            row["pulled"] += int(n)
+    block["distinct_systems_surfaced"] = sum(1 for r in systems.values() if r["surfaced"])
+    block["distinct_systems_pulled"] = sum(1 for r in systems.values() if r["pulled"])
+    block["by_system"] = sorted(
+        (r for r in systems.values() if r["surfaced"]),
+        key=lambda r: (-r["surfaced"], r["name"] or ""),
+    )[:SYSTEM_USAGE_TOP]
+    block.update(_coverage(complete.get("*"), since))
+    return block
+
+
 async def retrieval_summary(
     user_id: int | None, *, days: int = 30, near_miss_samples: int = 0,
 ) -> dict:
@@ -878,6 +994,7 @@ async def retrieval_summary(
         "sources": {},
         "usage": {},
         "rule_usage": {},
+        "system_usage": {},
         "read_failed": False,
     }
 
@@ -1435,6 +1552,7 @@ async def retrieval_summary(
     )
     rule_usage.update(_coverage((rule_complete or {}).get("*"), since))
     out["rule_usage"] = rule_usage
+    out["system_usage"] = await _system_usage(user_id, since)
 
     # ── What is wrong (#3431) ────────────────────────────────────────────
     #
@@ -1514,6 +1632,7 @@ async def retrieval_summary(
     )
     out["silent_surfaces"] = _silent_surfaces(
         out["sources"], usage, rule_usage, active,
+        system_usage=out["system_usage"],
     )
 
     return out
diff --git a/src/scribe/services/system_usage.py b/src/scribe/services/system_usage.py
index 61c5967..001d788 100644
--- a/src/scribe/services/system_usage.py
+++ b/src/scribe/services/system_usage.py
@@ -13,7 +13,10 @@ from __future__ import annotations
 
 import logging
 
+from sqlalchemy import func, select
+
 from scribe.models import async_session
+from scribe.models.base import iso
 from scribe.models.system_usage import PULLED, SURFACED, SystemUsageEvent
 from scribe.services.background import report_telemetry_failure, spawn
 
@@ -65,3 +68,67 @@ def record_system_pulled(
         logger.debug("system usage payload build failed", exc_info=True)
         return
     spawn(_insert_events(rows), site="system_usage_write")
+
+
+def empty_system_usage() -> dict:
+    """The zero readout — a System no event has touched.
+
+    Rendered unconditionally, like `empty_rule_usage`, so a System predating
+    the table reads as "never shown, never opened" rather than as a missing
+    key. Every System in an install predates it, so for a while this is the
+    normal state and must not look like a broken readout.
+
+    The same four keys as the client's `RecordUsage`, but read differently: a
+    System's rulings are delivered IN FULL in the injected line, so a
+    surfacing with no pull is the arm working, not dead weight. See
+    `retrieval_telemetry`'s `system_usage` block for why no ratio is offered.
+    """
+    return {
+        "surfaced_count": 0,
+        "pull_count": 0,
+        "last_surfaced_at": None,
+        "last_pulled_at": None,
+    }
+
+
+async def usage_for_systems(system_ids: list[int]) -> dict[int, dict]:
+    """Aggregate usage for a set of Systems: {system_id: {counts + timestamps}}.
+
+    One GROUP BY for the whole list, never a query per row — this decorates a
+    list view. Systems with no events come back as `empty_system_usage()`.
+    Fails open: a readout that could break the Systems list is worse than a
+    zero, but the failure is reported so the zero is not mistaken for silence
+    (#2663).
+    """
+    ids = [int(s) for s in system_ids]
+    out: dict[int, dict] = {sid: empty_system_usage() for sid in ids}
+    if not ids:
+        return out
+    try:
+        async with async_session() as session:
+            rows = (
+                await session.execute(
+                    select(
+                        SystemUsageEvent.system_id,
+                        SystemUsageEvent.event,
+                        func.count().label("n"),
+                        func.max(SystemUsageEvent.created_at).label("last_at"),
+                    )
+                    .where(SystemUsageEvent.system_id.in_(ids))
+                    .group_by(SystemUsageEvent.system_id, SystemUsageEvent.event)
+                )
+            ).all()
+    except Exception:
+        await report_telemetry_failure("system_usage", "readout")
+        return out
+    for system_id, event, n, last_at in rows:
+        slot = out.get(int(system_id))
+        if slot is None:
+            continue
+        if event == SURFACED:
+            slot["surfaced_count"] = int(n)
+            slot["last_surfaced_at"] = iso(last_at)
+        elif event == PULLED:
+            slot["pull_count"] = int(n)
+            slot["last_pulled_at"] = iso(last_at)
+    return out
diff --git a/tests/conftest.py b/tests/conftest.py
index 234db00..79447da 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -131,6 +131,26 @@ def _no_rulings_arm():
         yield
 
 
+@pytest.fixture(autouse=True)
+def _no_system_usage_readout():
+    """Stub the per-System usage lookup the Systems list and get_system carry
+    (#4769).
+
+    Autouse for _no_rulings_arm's reason: every route and tool test that
+    reads a System now reaches a GROUP BY on system_usage_events. Stubbed to
+    the zero shape for whatever ids were asked. tests/test_system_usage_readout.py
+    binds the real function at import time, before this patch runs.
+    """
+    from scribe.services.system_usage import empty_system_usage
+
+    async def _zeros(system_ids):
+        return {int(s): empty_system_usage() for s in system_ids}
+
+    with patch("scribe.services.system_usage.usage_for_systems",
+               AsyncMock(side_effect=_zeros)):
+        yield
+
+
 @pytest.fixture(autouse=True)
 def _no_task_log_arm():
     """Stub the task-log read arm that get_task / list_tasks / get_milestone
diff --git a/tests/test_retrieval_registry.py b/tests/test_retrieval_registry.py
index 9da0a80..56d4097 100644
--- a/tests/test_retrieval_registry.py
+++ b/tests/test_retrieval_registry.py
@@ -41,6 +41,9 @@ SRC = Path(__file__).resolve().parents[1] / "src"
 RECORDERS = {
     "record_retrieval", "record_surfaced", "record_pulled",
     "record_rule_surfaced", "record_rule_pulled", "rules_payload",
+    # The rulings arm (#4769): its two recorders, and `rulings_for_paths`,
+    # which forwards its caller's `source` the way `rules_payload` does.
+    "record_system_surfaced", "record_system_pulled", "rulings_for_paths",
 }
 
 
diff --git a/tests/test_system_usage_readout.py b/tests/test_system_usage_readout.py
new file mode 100644
index 0000000..c156063
--- /dev/null
+++ b/tests/test_system_usage_readout.py
@@ -0,0 +1,161 @@
+"""Rulings are counted where someone will read them (#4769).
+
+`system_usage_events` was written from milestone 444 step 4 and read by
+nothing. These pin the two readouts:
+
+- PER SYSTEM: `usage_for_systems` — one GROUP BY, a zero shape for a System
+  nothing touched — carried by the Systems list, the REST detail and MCP
+  `get_system`.
+- IN AGGREGATE: `retrieval_summary`'s `system_usage` block — counts by source,
+  the areas named, and deliberately NO pull-through ratio.
+
+Integration for both aggregates, not mocked: a GROUP BY the database rejects
+is swallowed by the fail-open guard and reads as zero, which is #2663 exactly.
+"""
+from unittest.mock import AsyncMock, patch
+
+import pytest
+import pytest_asyncio
+
+from scribe.models import async_session
+from scribe.services.system_usage import empty_system_usage
+# Bound at import, before conftest's autouse stub replaces the module attribute.
+from scribe.services.system_usage import usage_for_systems as real_usage_for_systems
+from tests.helpers import ensure_user
+
+
+# ── the payloads carry it ────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_system_carries_its_usage():
+    from tests.helpers import fake_system
+
+    shown = {**empty_system_usage(), "surfaced_count": 4, "pull_count": 1}
+    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.systems.systems_svc") as svc, \
+         patch("scribe.services.system_usage.usage_for_systems",
+               AsyncMock(return_value={3: shown})):
+        svc.get_system = AsyncMock(return_value=fake_system(id=3))
+        svc.list_records_for_system = AsyncMock(return_value=[])
+        from scribe.mcp.tools.systems import get_system
+        result = await get_system(system_id=3)
+    assert result["usage"] == shown
+
+
+def test_the_zero_shape_matches_the_client_type():
+    """The four keys `RecordUsage` in frontend/src/types/usage.ts declares —
+    a fifth here would be a field the chip never reads, a missing one a
+    crash on every System nothing has touched."""
+    assert set(empty_system_usage()) == {
+        "surfaced_count", "pull_count", "last_surfaced_at", "last_pulled_at",
+    }
+
+
+@pytest.mark.asyncio
+async def test_an_empty_id_list_reads_nothing():
+    with patch("scribe.services.system_usage.async_session") as session:
+        assert await real_usage_for_systems([]) == {}
+    session.assert_not_called()
+
+
+# ── the aggregates, against Postgres ─────────────────────────────────────
+
+
+@pytest_asyncio.fixture
+async def ruled_areas():
+    """An owner, a project and two Systems, with usage rows on both."""
+    from scribe.models.project import Project
+    from scribe.models.system import System
+    from scribe.models.system_usage import SystemUsageEvent
+
+    async with async_session() as s:
+        owner = await ensure_user(s, "system_usage_owner")
+        other = await ensure_user(s, "system_usage_other")
+        project = Project(user_id=owner.id, title="Ruled areas")
+        s.add(project)
+        await s.flush()
+        billing = System(user_id=owner.id, project_id=project.id, name="Billing")
+        storage = System(user_id=owner.id, project_id=project.id, name="Storage")
+        s.add_all([billing, storage])
+        await s.flush()
+
+        def ev(uid, sid, event, source):
+            return SystemUsageEvent(
+                user_id=uid, system_id=sid, event=event, source=source,
+                project_id=project.id,
+            )
+
+        s.add_all([
+            ev(owner.id, billing.id, "surfaced", "rulings_pre_tool"),
+            ev(owner.id, billing.id, "surfaced", "rulings_pre_tool"),
+            ev(owner.id, billing.id, "surfaced", "rulings_write_path"),
+            ev(owner.id, billing.id, "pulled", "mcp_get_system"),
+            ev(owner.id, storage.id, "surfaced", "rulings_write_path"),
+            # Another user's session: in the per-System count, which is about
+            # the System, and NOT in the owner's telemetry, which is theirs.
+            ev(other.id, storage.id, "surfaced", "rulings_pre_tool"),
+        ])
+        ids = {
+            "owner": owner.id, "other": other.id, "pid": project.id,
+            "billing": billing.id, "storage": storage.id,
+        }
+        await s.commit()
+    yield ids
+
+    from sqlalchemy import delete
+    async with async_session() as s:
+        await s.execute(delete(SystemUsageEvent).where(
+            SystemUsageEvent.system_id.in_([ids["billing"], ids["storage"]])))
+        await s.execute(delete(System).where(System.project_id == ids["pid"]))
+        await s.execute(delete(Project).where(Project.id == ids["pid"]))
+        await s.commit()
+
+
+@pytest.mark.integration
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("_dispose_engine")
+async def test_usage_for_systems_counts_each_system(ruled_areas):
+    ids = ruled_areas
+    out = await real_usage_for_systems([ids["billing"], ids["storage"], 987654321])
+    billing, storage = out[ids["billing"]], out[ids["storage"]]
+    assert billing["surfaced_count"] == 3 and billing["pull_count"] == 1
+    assert billing["last_surfaced_at"] and billing["last_pulled_at"]
+    assert storage["surfaced_count"] == 2 and storage["pull_count"] == 0
+    assert storage["last_pulled_at"] is None
+    assert out[987654321] == empty_system_usage()
+
+
+@pytest.mark.integration
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("_dispose_engine")
+async def test_the_telemetry_block_names_the_areas_and_offers_no_ratio(ruled_areas):
+    from scribe.services.retrieval_telemetry import retrieval_summary
+
+    ids = ruled_areas
+    block = (await retrieval_summary(ids["owner"], days=30))["system_usage"]
+    assert "system_usage_failed" not in block, "the aggregate did not execute"
+    assert block["surfaced"] == 4 and block["pulled"] == 1
+    assert block["by_source"] == {
+        "rulings_pre_tool": 2, "rulings_write_path": 2, "mcp_get_system": 1,
+    }
+    assert block["distinct_systems_surfaced"] == 2
+    assert block["distinct_systems_pulled"] == 1
+    assert [(r["name"], r["surfaced"], r["pulled"]) for r in block["by_system"]] == [
+        ("Billing", 3, 1), ("Storage", 1, 0),
+    ]
+    # Rulings are delivered in full in the line; a ratio of opens would read
+    # near zero on an arm that is working.
+    assert "pull_through" not in block
+
+
+@pytest.mark.integration
+@pytest.mark.asyncio
+@pytest.mark.usefixtures("_dispose_engine")
+async def test_a_fresh_install_reads_zero_not_failed():
+    from scribe.services.retrieval_telemetry import retrieval_summary
+
+    block = (await retrieval_summary(990031, days=30))["system_usage"]
+    assert "system_usage_failed" not in block
+    assert block["surfaced"] == 0 and block["by_system"] == []
+    assert block["covers_window"] is None