feat(systems): a System names its files — path patterns stored, validated and matched (milestone 444 step 3, #4756)

A System gains path_patterns: globs relative to the repo root (* within one
directory, ** across any depth, a plain directory covering everything under
it). One service validates them for every door, so the web UI and MCP refuse
the same bad pattern with the same message. systems_for_paths resolves paths
to every active System that covers them, which step 4 (#4757) uses to deliver
an area's rulings when its files are touched.

- schema: systems.path_patterns JSONB NOT NULL default [] (migration 0113)
- service: normalize_path_patterns, path_matches, systems_for_paths
- routes + MCP create_system/update_system accept it; [] clears
- web UI: a Files field in the create and edit forms, patterns on the card
- backup carries it through export and restore
- using-scribe reflex 7: tagging work keeps a System's files current

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

alembic/versions/0113_system_path_patterns.py

@@ -0,0 +1,34 @@
+"""system_path_patterns — a System names the files that are its area
+(milestone 444 step 3, #4756)
+
+Revision ID: 0113
+Revises: 0112
+Create Date: 2026-10-02
+
+A JSONB list of globs relative to the repo root. NOT NULL with a `[]`
+default, so an existing System reads as "no paths yet" rather than as NULL. No
+backfill: which files are which area is a judgment, and the charters that name
+directories in prose are not a mapping anyone confirmed.
+"""
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+revision = "0113"
+down_revision = "0112"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "systems",
+        sa.Column(
+            "path_patterns", postgresql.JSONB(), nullable=False,
+            server_default=sa.text("'[]'::jsonb"),
+        ),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("systems", "path_patterns")

frontend/src/api/systems.ts

@@ -14,6 +14,12 @@ export interface System {
   color: string | null;
   status: "active" | "archived";
   order_index: number;
+  /**
+   * The files that are this area, as globs relative to the repo root: `*`
+   * within one directory, `**` across any depth, a plain directory covering
+   * everything under it. Empty means the area has not named its files.
+   */
+  path_patterns: string[];
   open_issue_count: number;
   created_at: string | null;
   updated_at: string | null;
@@ -39,7 +45,13 @@ export interface CreatedSystem extends System {
 
 export async function createSystem(
   projectId: number,
-  data: { name: string; description?: string; color?: string; canonical_id?: number },
+  data: {
+    name: string;
+    description?: string;
+    color?: string;
+    canonical_id?: number;
+    path_patterns?: string[];
+  },
 ): Promise<CreatedSystem> {
   return apiPost(`/api/projects/${projectId}/systems`, data);
 }
@@ -53,6 +65,7 @@ export async function updateSystem(
     color: string | null;
     status: "active" | "archived";
     order_index: number;
+    path_patterns: string[];
   }>,
 ): Promise<System> {
   return apiPatch(`/api/projects/${projectId}/systems/${systemId}`, data);

frontend/src/components/SystemsSection.vue

@@ -28,6 +28,7 @@ const newDescription = ref("");
 // feature two matchers to keep in step, which is the exact drift the catalog
 // exists to end. The server still applies an exact hit on submit.
 const newCanonicalId = ref<number | null>(null);
+const newPaths = ref("");
 const creating = ref(false);
 // An `overlap` the server offered after a create — an offer, never applied.
 const suggestion = ref<{ systemId: number; match: CanonicalMatch } | null>(null);
@@ -37,6 +38,7 @@ const editingId = ref<number | null>(null);
 const editName = ref("");
 const editDescription = ref("");
 const editCanonicalId = ref<number | null>(null);
+const editPaths = ref("");
 const savingEdit = ref(false);
 
 // Mapping review
@@ -55,6 +57,16 @@ const visibleSystems = computed(() =>
 
 const proposals = computed(() => canon.proposalsByProject[props.projectId] ?? []);
 
+// The files field is one pattern per line. The server is the one that
+// validates and tidies them, so this only splits — a second validator here
+// would be a second answer to "is this pattern acceptable".
+function parsePaths(text: string): string[] {
+  return text
+    .split("\n")
+    .map((line) => line.trim())
+    .filter(Boolean);
+}
+
 function areaName(system: System): string | null {
   return canon.byId(system.canonical_id)?.name ?? null;
 }
@@ -89,6 +101,7 @@ function openCreate() {
   newName.value = "";
   newDescription.value = "";
   newCanonicalId.value = null;
+  newPaths.value = "";
 }
 
 function cancelCreate() {
@@ -96,6 +109,7 @@ function cancelCreate() {
   newName.value = "";
   newDescription.value = "";
   newCanonicalId.value = null;
+  newPaths.value = "";
 }
 
 async function submitCreate() {
@@ -107,6 +121,7 @@ async function submitCreate() {
       name,
       description: newDescription.value.trim() || undefined,
       canonical_id: newCanonicalId.value ?? undefined,
+      path_patterns: parsePaths(newPaths.value),
     });
     cancelCreate();
     if (created.canonical_suggestion) {
@@ -157,6 +172,7 @@ function startEdit(system: System) {
   editName.value = system.name;
   editDescription.value = system.description;
   editCanonicalId.value = system.canonical_id;
+  editPaths.value = system.path_patterns.join("\n");
 }
 
 function cancelEdit() {
@@ -171,6 +187,7 @@ async function submitEdit(system: System) {
     await store.updateSystem(props.projectId, system.id, {
       name,
       description: editDescription.value.trim(),
+      path_patterns: parsePaths(editPaths.value),
     });
     // The mapping is a separate write with its own validation — one column,
     // one writer (services/canonical_systems.set_system_canonical).
@@ -180,8 +197,9 @@ async function submitEdit(system: System) {
     }
     editingId.value = null;
     toast.show("System updated");
-  } catch {
+  } catch (e) {
-    toast.show("Failed to update system", "error");
+    // A refused pattern comes back as a 400 naming it — say which.
+    toast.show(apiErrorMessage(e, "Failed to update system"), "error");
   } finally {
     savingEdit.value = false;
   }
@@ -337,6 +355,20 @@ async function confirmDelete() {
           Files this system under an area shared by every project. Your name stays as you typed it.
         </span>
       </label>
+      <label class="area-field">
+        <span class="area-label">Files</span>
+        <textarea
+          v-model="newPaths"
+          class="fs-input system-textarea system-paths-input"
+          rows="2"
+          placeholder="e.g. src/billing — one pattern per line"
+          aria-label="System files"
+          spellcheck="false"
+        ></textarea>
+        <span class="field-hint">
+          One pattern per line, from the repo root. <code>*</code> stays in one folder, <code>**</code> reaches any depth, and a folder covers everything in it.
+        </span>
+      </label>
       <div class="system-form-actions">
         <button type="submit" class="btn-primary btn-compact" :disabled="!newName.trim() || creating">
           {{ creating ? "Creating…" : "Create" }}
@@ -397,6 +429,17 @@ async function confirmDelete() {
                 </option>
               </select>
             </label>
+            <label class="area-field">
+              <span class="area-label">Files</span>
+              <textarea
+                v-model="editPaths"
+                class="fs-input system-textarea system-paths-input"
+                rows="2"
+                placeholder="One pattern per line, from the repo root"
+                aria-label="System files"
+                spellcheck="false"
+              ></textarea>
+            </label>
             <div class="system-form-actions">
               <button type="submit" class="btn-primary btn-compact" :disabled="!editName.trim() || savingEdit">
                 {{ savingEdit ? "Saving…" : "Save" }}
@@ -430,6 +473,9 @@ async function confirmDelete() {
               >{{ areaName(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">
+              <li v-for="pattern in system.path_patterns" :key="pattern" class="system-path">{{ pattern }}</li>
+            </ul>
           </div>
           <div class="system-actions">
             <button class="action-btn" title="Edit" aria-label="Edit system" @click="startEdit(system)">
@@ -627,6 +673,28 @@ async function confirmDelete() {
 .system-textarea { resize: vertical; }
 
 .system-form-actions { display: flex; gap: 0.4rem; }
+.system-paths-input { font-family: var(--fs-font-mono); font-size: 0.8rem; }
+
+/* The area's files (milestone 444). Mono because they are paths to be read
+   character for character; small because they qualify the card, not lead it. */
+.system-paths {
+  list-style: none;
+  margin: var(--fs-space-2) 0 0;
+  padding: 0;
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--fs-space-1);
+}
+.system-path {
+  font-family: var(--fs-font-mono);
+  font-size: 0.7rem;
+  color: var(--fs-text-secondary);
+  background: var(--fs-surface-page);
+  border: 1px solid var(--fs-border-color);
+  border-radius: var(--fs-radius-sm);
+  padding: 0.05rem 0.4rem;
+  word-break: break-all;
+}
 
 /* RESTORED (#2444). Both lost their base rule to a CSS sweep; only the
    `--archived` modifier and the `:hover .system-actions` reveal survived.

frontend/src/stores/systems.ts

@@ -22,7 +22,7 @@ export const useSystemsStore = defineStore("systems", () => {
 
   async function createSystem(
     projectId: number,
-    data: { name: string; description?: string; color?: string; canonical_id?: number },
+    data: Parameters<typeof api.createSystem>[1],
   ) {
     const system = await api.createSystem(projectId, data);
     if (!systemsByProject.value[projectId]) systemsByProject.value[projectId] = [];
@@ -33,7 +33,7 @@ export const useSystemsStore = defineStore("systems", () => {
   async function updateSystem(
     projectId: number,
     systemId: number,
-    data: Partial<Pick<System, "name" | "description" | "color" | "status" | "order_index">>,
+    data: Parameters<typeof api.updateSystem>[2],
   ) {
     const system = await api.updateSystem(projectId, systemId, data);
     const list = systemsByProject.value[projectId];

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe for Claude Code: connects the scribe MCP server, adds the hooks that deliver live project state and relevant records at the right moment, ships the shared client-neutral Scribe skills (using-scribe, writing-plans, reporting-back, systematic-debugging, verification, brainstorming, reusing-code, shape-accounting), and syncs your saved Scribe Processes as skills (/scribe:sync).",
-  "version": "2026.10.02.2259",
+  "version": "2026.10.03.0255",
   "author": {
     "name": "Bryan Van Deusen"
   },

plugin/skills/using-scribe/SKILL.md

@@ -198,6 +198,11 @@ Two constraints on *how* that's achieved:
    work-logs alike. Treat it as the tagging question asked at the moment of
    work: tag the record, create the missing System, or deliberately leave it.
 
+   A System also names its files: `path_patterns`, globs from the repo root.
+   When the work you are tagging touched files its System's patterns don't
+   cover, and they plainly belong to that area, add them with `update_system`
+   — which files are which area is your call, as naming the area was.
+
 8. **Name the record, never just its number.** Whenever you refer to a Scribe
    record — in a message to the operator, a commit message, a task body, a
    work-log — write the id *and* its title: `#3244 "the staleness signal"`,

src/scribe/mcp/tools/systems.py

@@ -9,6 +9,7 @@ tools are thin wrappers.
 Sentinels (match the milestone/task tool conventions):
   - name="" / description="" / color="" / status="" → "leave unchanged" on update
   - order_index=-1 → "leave unchanged" on update (0 is a valid order_index)
+  - path_patterns=None → "leave unchanged" on update ([] clears them)
 """
 from __future__ import annotations
 
@@ -167,6 +168,7 @@ async def create_system(
     name: str,
     description: str = "",
     color: str = "",
+    path_patterns: list[str] | None = None,
 ) -> dict:
     """Create a System (a reusable, self-describing subsystem/area) in a project.
 
@@ -195,11 +197,20 @@ async def create_system(
     under the System, so a ruling there reaches each session working in the
     area; a quote in a work log reaches one only if a search matches it.
 
+    `path_patterns` name the files that ARE the area: globs relative to the
+    repo root, `*` within one directory, `**` across any depth, and a plain
+    directory covering everything under it (`src/billing`,
+    `frontend/src/components/Billing*.vue`). The description says what the
+    area is for; the patterns say where it lives, so work touching those files
+    can be traced to the System without a search. Give them when the area's
+    files are known; a System without them still works for tagging.
+
     Args:
         project_id: The project this system belongs to (required).
         name: Short label (required).
         description: What the system is and how it's used — a name is rarely enough.
         color: Optional UI accent (hex), or empty.
+        path_patterns: The area's files as repo-relative globs, or omit.
 
     Duplicate-gated like the other creates: if a System with the same
     normalized name already exists in this project (archived included), the
@@ -237,7 +248,7 @@ async def create_system(
     system = await systems_svc.create_system(
         uid, project_id=project_id, name=name,
         description=description or None, color=color or None,
-        canonical_id=applied,
+        canonical_id=applied, path_patterns=path_patterns,
     )
     if system is None:
         raise ValueError(f"cannot create system in project {project_id} (no write access)")
@@ -307,6 +318,7 @@ async def update_system(
     color: str = "",
     status: str = "",
     order_index: int = -1,
+    path_patterns: list[str] | None = None,
 ) -> dict:
     """Update a System. Only explicitly provided fields change.
 
@@ -319,10 +331,14 @@ async def update_system(
     history. If the charter above it contradicts a ruling, fix that sentence
     in the same edit.
 
+    `path_patterns` also REPLACES the whole list, and `[]` clears it.
+
     Args:
         status: 'active' or 'archived'. Archive a system to retire it without
             losing history; archived systems hide from default lists.
         order_index: display position (0-based); -1 = leave unchanged.
+        path_patterns: The area's files as repo-relative globs (see
+            create_system). Omit to leave unchanged; [] clears them.
     """
     uid = current_user_id()
     fields: dict = {}
@@ -336,6 +352,8 @@ async def update_system(
         fields["status"] = status
     if order_index >= 0:
         fields["order_index"] = order_index
+    if path_patterns is not None:
+        fields["path_patterns"] = path_patterns
     system = await systems_svc.update_system(uid, system_id, **fields)
     if system is None:
         raise ValueError(f"system {system_id} not found or no write access")

src/scribe/models/system.py

@@ -1,4 +1,5 @@
-from sqlalchemy import ForeignKey, Index, Integer, Text, UniqueConstraint
+from sqlalchemy import ForeignKey, Index, Integer, Text, UniqueConstraint, text
+from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column
 
 from scribe.models import Base
@@ -38,6 +39,15 @@ class System(Base, TimestampMixin, SoftDeleteMixin):
     # active | archived — systems accumulate; archive rather than delete.
     status: Mapped[str] = mapped_column(Text, default="active", server_default="active")
     order_index: Mapped[int] = mapped_column(Integer, default=0, server_default="0")
+    # The files that ARE this area, as globs relative to the repo root
+    # (milestone 444). The description says what the area is FOR; these say
+    # where it lives, so a command or edit touching those files can be
+    # resolved to the System — and its rulings — without a similarity search.
+    # NOT NULL with a `[]` default for the reason DesignToken.supersedes gives:
+    # a nullable list has two empties, and every reader must handle both.
+    path_patterns: Mapped[list] = mapped_column(
+        JSONB, nullable=False, default=list, server_default=text("'[]'::jsonb")
+    )
 
     __table_args__ = (
         Index("ix_systems_project_id", "project_id"),
@@ -54,6 +64,7 @@ class System(Base, TimestampMixin, SoftDeleteMixin):
             "color": self.color,
             "status": self.status,
             "order_index": self.order_index,
+            "path_patterns": list(self.path_patterns or []),
             "created_at": iso(self.created_at),
             "updated_at": iso(self.updated_at),
         }

src/scribe/routes/systems.py

@@ -82,12 +82,16 @@ async def create_system_route(project_id: int):
     # Exact is mechanical and applied; overlap is a judgment call and is only
     # offered back for the form to present.
     applied = canonical["id"] if canonical and canonical["basis"] == "exact" else None
-    system = await systems_svc.create_system(
+    try:
-        uid, project_id=project_id, name=data["name"],
+        system = await systems_svc.create_system(
-        description=data.get("description"), color=data.get("color"),
+            uid, project_id=project_id, name=data["name"],
-        order_index=data.get("order_index", 0),
+            description=data.get("description"), color=data.get("color"),
-        canonical_id=data.get("canonical_id") or applied,
+            order_index=data.get("order_index", 0),
-    )
+            canonical_id=data.get("canonical_id") or applied,
+            path_patterns=data.get("path_patterns"),
+        )
+    except ValueError as e:
+        return jsonify({"error": str(e)}), 400
     if system is None:
         return jsonify({"error": "Permission denied"}), 403
     out = system.to_dict()
@@ -125,11 +129,14 @@ async def update_system_route(project_id: int, system_id: int):
     if system is None or system.project_id != project_id:
         return not_found("System")
     data = await request.get_json() or {}
-    allowed = {"name", "description", "color", "status", "order_index"}
+    allowed = {"name", "description", "color", "status", "order_index", "path_patterns"}
     fields = {k: v for k, v in data.items() if k in allowed}
     if "status" in fields and fields["status"] not in ("active", "archived"):
         return jsonify({"error": "status must be 'active' or 'archived'"}), 400
-    updated = await systems_svc.update_system(uid, system_id, **fields)
+    try:
+        updated = await systems_svc.update_system(uid, system_id, **fields)
+    except ValueError as e:
+        return jsonify({"error": str(e)}), 400
     if updated is None:
         return not_found("System")
     return jsonify(updated.to_dict())

src/scribe/services/backup.py

@@ -387,6 +387,7 @@ def _system_rows(rows, canonical_slugs: dict[int, str]) -> list[dict]:
             "id": r.id, "user_id": r.user_id, "project_id": r.project_id,
             "name": r.name, "description": r.description, "color": r.color,
             "status": r.status, "order_index": r.order_index,
+            "path_patterns": list(r.path_patterns or []),
             "canonical_slug": canonical_slugs.get(r.canonical_id or 0),
         }
         for r in rows
@@ -1460,6 +1461,8 @@ def _build_system(row: dict, maps: _Maps) -> System | None:
         color=row.get("color"),
         status=row.get("status", "active"),
         order_index=row.get("order_index", 0),
+        # Absent in a backup taken before milestone 444: no paths, not an error.
+        path_patterns=list(row.get("path_patterns") or []),
         # An unknown slug restores UNMAPPED rather than failing: the System and
         # its records are the payload, the mapping is an aid.
         canonical_id=maps.canonical_by_slug.get(row.get("canonical_slug") or ""),

src/scribe/services/systems.py

@@ -7,6 +7,7 @@ many-to-many through record_systems, mutable over time.
 """
 import logging
 from datetime import datetime, timezone
+from pathlib import PurePosixPath
 
 from sqlalchemy import delete, func, select
 
@@ -31,6 +32,87 @@ def local_name_key(name: str) -> str:
     return " ".join(name.split()).lower()
 
 
+# Bounds on what one System may claim. Generous for a real area — a handful of
+# directories and the odd stray file — and small enough that a pasted file
+# listing is refused rather than stored as the area's definition.
+MAX_PATH_PATTERNS = 50
+MAX_PATH_PATTERN_LENGTH = 300
+
+
+def normalize_repo_path(path: str) -> str:
+    """A path as the patterns see it: relative to the repo root, `/`-separated.
+
+    Shared by the patterns and the paths matched against them, so the two can
+    never disagree about whether `./src/x.py` and `src/x.py` are one file.
+    """
+    out = (path or "").strip().replace("\\", "/")
+    while out.startswith("./"):
+        out = out[2:]
+    out = out.lstrip("/")
+    while len(out) > 1 and out.endswith("/"):
+        out = out[:-1]
+    return out
+
+
+def normalize_path_patterns(patterns) -> list[str]:
+    """Validate and tidy a System's path patterns; ValueError says what is wrong.
+
+    Blank entries are dropped and repeats collapse, keeping the first-written
+    order. A pattern that climbs out of the repo (`..`) is refused rather than
+    dropped: it can never match, and storing it would read as coverage.
+    """
+    if patterns is None:
+        return []
+    if isinstance(patterns, str) or not isinstance(patterns, (list, tuple)):
+        raise ValueError("path_patterns must be a list of glob strings")
+    out: list[str] = []
+    for raw in patterns:
+        if not isinstance(raw, str):
+            raise ValueError("path_patterns must be a list of glob strings")
+        pattern = normalize_repo_path(raw)
+        if not pattern:
+            continue
+        if len(pattern) > MAX_PATH_PATTERN_LENGTH:
+            raise ValueError(
+                f"path pattern longer than {MAX_PATH_PATTERN_LENGTH} characters: "
+                f"{pattern[:60]}…"
+            )
+        if ".." in pattern.split("/"):
+            raise ValueError(
+                f"path pattern {pattern!r} leaves the repo — patterns are "
+                "relative to the repo root"
+            )
+        if pattern not in out:
+            out.append(pattern)
+    if len(out) > MAX_PATH_PATTERNS:
+        raise ValueError(
+            f"{len(out)} path patterns; a System takes at most "
+            f"{MAX_PATH_PATTERNS} — name directories with `**` rather than "
+            "listing their files"
+        )
+    return out
+
+
+def path_matches(pattern: str, path: str) -> bool:
+    """Whether a repo-relative path falls under one pattern.
+
+    Glob semantics are `PurePosixPath.full_match`: `*` stays inside one path
+    segment, `**` spans any number of them, and case counts. A pattern with
+    no wildcard that names a directory covers everything under it, so
+    `src/billing` means the directory the way a person writing it means it.
+    """
+    path = normalize_repo_path(path)
+    if not path or not pattern:
+        return False
+    candidate = PurePosixPath(path)
+    return candidate.full_match(pattern) or candidate.full_match(f"{pattern}/**")
+
+
+def matching_patterns(patterns, path: str) -> list[str]:
+    """The patterns among `patterns` that `path` falls under, in their order."""
+    return [p for p in (patterns or []) if path_matches(p, path)]
+
+
 async def assess_system_name(user_id: int, project_id: int, name: str) -> dict:
     """What BOTH doors must know before minting a System name (milestone 307).
 
@@ -154,13 +236,18 @@ async def create_system(
     color: str | None = None,
     order_index: int = 0,
     canonical_id: int | None = None,
+    path_patterns: list[str] | None = None,
 ) -> System | None:
     """Create a System. None if the user can't write the project.
 
     `canonical_id` maps the new System onto the global catalog; leaving it None
     is fine — an unmapped System is fully usable, and the mapping can be
     proposed later (services/canonical_systems.propose_mappings).
+
+    `path_patterns` are validated here, so every door refuses the same bad
+    pattern with the same message (ValueError).
     """
+    patterns = normalize_path_patterns(path_patterns)
     if not await access.can_write_project(user_id, project_id):
         return None
     async with async_session() as session:
@@ -172,6 +259,7 @@ async def create_system(
             color=color,
             order_index=order_index,
             canonical_id=canonical_id,
+            path_patterns=patterns,
         )
         session.add(system)
         await session.commit()
@@ -209,13 +297,40 @@ async def list_systems(
         return list(result.scalars().all())
 
 
+async def systems_for_paths(
+    user_id: int, project_id: int, paths: list[str],
+) -> list[tuple[System, list[str]]]:
+    """The project's active Systems whose patterns cover any of `paths`.
+
+    Each comes with the paths it matched, in the order given. A path can match
+    several Systems — areas overlap, and every one it belongs to answers for
+    it — so nothing here picks a winner. Systems with no patterns never match:
+    an area that has not named its files is not claiming all of them.
+    """
+    wanted = [p for p in (normalize_repo_path(x) for x in paths or []) if p]
+    if not wanted:
+        return []
+    out: list[tuple[System, list[str]]] = []
+    for system in await list_systems(user_id, project_id):
+        patterns = system.path_patterns or []
+        if not patterns:
+            continue
+        hit = [p for p in wanted if matching_patterns(patterns, p)]
+        if hit:
+            out.append((system, hit))
+    return out
+
 async def update_system(user_id: int, system_id: int, **fields: object) -> System | None:
     """Update a System if the user can write its project."""
     # canonical_id is deliberately NOT settable here: canonical_systems.
     # set_system_canonical is its single writer, because it also validates the
     # catalog entry is live. Two entry points onto one column is the drift this
     # table exists to end.
-    allowed = {"name", "description", "color", "status", "order_index"}
+    allowed = {"name", "description", "color", "status", "order_index", "path_patterns"}
+    # Validated before anything is read, so a refused pattern changes nothing.
+    # `[]` is a value here, not "leave unchanged": it clears the paths.
+    if fields.get("path_patterns") is not None:
+        fields["path_patterns"] = normalize_path_patterns(fields["path_patterns"])
     async with async_session() as session:
         system = await session.get(System, system_id)
         if system is None or system.deleted_at is not None:

tests/test_guidance_ownership.py

@@ -205,6 +205,9 @@ TOPICS: tuple[Topic, ...] = (
     Topic("code says what a thing does, not what was wanted", U,
           ("rulings", "unconfirmed"),
           "code tells you what a thing does, not what was wanted"),
+    Topic("a System names its files, and tagging work keeps them current", U,
+          ("path_patterns", "update_system"),
+          "which files are which area is your call"),
     # ── process arcs — owned by their skills ──
     Topic("plan in a milestone, steps created together", "skill:writing-plans", ("start_planning", "{{ref:"),
           "a milestone earns its place when the work has an arc", index=("start_planning",)),

tests/test_mcp_tool_systems.py

@@ -101,6 +101,23 @@ async def test_get_system_splits_records_by_kind():
     assert [r["id"] for r in result["notes"]] == [12]
 
 
+@pytest.mark.asyncio
+async def test_path_patterns_reach_the_service_from_both_tools():
+    """Omitted means unchanged; an empty list is a value — it clears them."""
+    with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \
+         patch("scribe.mcp.tools.systems.systems_svc") as svc:
+        svc.assess_system_name = AsyncMock(return_value=_NO_MATCH)
+        svc.create_system = AsyncMock(return_value=fake_system(name="Billing"))
+        svc.update_system = AsyncMock(return_value=fake_system(name="Billing"))
+        from scribe.mcp.tools.systems import create_system, update_system
+        await create_system(project_id=5, name="Billing", path_patterns=["src/billing"])
+        assert svc.create_system.await_args.kwargs["path_patterns"] == ["src/billing"]
+        await update_system(system_id=1, name="Billing")
+        assert "path_patterns" not in svc.update_system.await_args.kwargs
+        await update_system(system_id=1, path_patterns=[])
+        assert svc.update_system.await_args.kwargs["path_patterns"] == []
+
+
 @pytest.mark.asyncio
 async def test_update_system_not_found_raises():
     with patch("scribe.mcp.tools.systems.current_user_id", return_value=1), \

tests/test_services_systems.py

@@ -126,3 +126,127 @@ async def test_assess_fails_open_so_a_naming_aid_cannot_block_a_create():
 async def test_assess_says_nothing_about_a_nameless_system():
     from scribe.services.systems import assess_system_name
     assert await assess_system_name(1, 5, "   ") == {"duplicate": None, "canonical": None}
+
+
+# ── path patterns — the files that ARE the area (milestone 444, #4756) ──
+
+def test_patterns_are_tidied_to_repo_relative_and_deduplicated():
+    from scribe.services.systems import normalize_path_patterns
+    out = normalize_path_patterns([
+        "  ./src/billing/ ", "/src/billing", "", "src\\api\\*.py", "  ",
+        "frontend/src/**/Billing*.vue",
+    ])
+    assert out == ["src/billing", "src/api/*.py", "frontend/src/**/Billing*.vue"]
+    assert normalize_path_patterns(None) == []
+    assert normalize_path_patterns([]) == []
+
+
+@pytest.mark.parametrize("bad", [
+    "src/billing",                 # a bare string, not a list
+    ["../other-repo/src"],          # leaves the repo
+    ["src/../../etc"],
+    [42],
+    ["x" * 301],
+    [f"src/f{i}.py" for i in range(51)],
+])
+def test_patterns_that_cannot_mean_an_area_are_refused(bad):
+    from scribe.services.systems import normalize_path_patterns
+    with pytest.raises(ValueError):
+        normalize_path_patterns(bad)
+
+
+@pytest.mark.parametrize("pattern,path,expected", [
+    # A plain directory covers everything under it, at any depth.
+    ("src/billing", "src/billing/invoice.py", True),
+    ("src/billing", "src/billing/deep/er/x.py", True),
+    ("src/billing", "src/billing", True),
+    ("src/billing", "src/billingual/x.py", False),
+    # `*` stays inside one segment; `**` spans any number, including none.
+    ("src/*.py", "src/app.py", True),
+    ("src/*.py", "src/pkg/app.py", False),
+    ("src/**/*.py", "src/pkg/sub/app.py", True),
+    ("src/**/*.py", "src/app.py", True),
+    ("**/Billing*.vue", "frontend/src/components/BillingCard.vue", True),
+    # Case counts, and the path is read the way the pattern was written.
+    ("src/billing", "Src/billing/x.py", False),
+    ("src/billing", "./src/billing/x.py", True),
+    ("src/billing", "", False),
+])
+def test_path_matches(pattern, path, expected):
+    from scribe.services.systems import path_matches
+    assert path_matches(pattern, path) is expected
+
+
+@pytest.mark.asyncio
+async def test_systems_for_paths_returns_every_area_a_path_belongs_to():
+    """Areas overlap, and each one a path belongs to answers for it — the
+    lookup never picks a winner. A System that named no files claims none."""
+    api = MagicMock(id=1, path_patterns=["src/scribe/routes", "src/scribe/mcp/tools"])
+    data = MagicMock(id=2, path_patterns=["src/scribe/models", "src/scribe/**/systems.py"])
+    unnamed = MagicMock(id=3, path_patterns=[])
+    with patch("scribe.services.systems.list_systems",
+               AsyncMock(return_value=[api, data, unnamed])):
+        from scribe.services.systems import systems_for_paths
+        out = await systems_for_paths(1, 5, [
+            "src/scribe/routes/systems.py", "./README.md", "",
+        ])
+    assert [(s.id, paths) for s, paths in out] == [
+        (1, ["src/scribe/routes/systems.py"]),
+        (2, ["src/scribe/routes/systems.py"]),
+    ]
+
+
+@pytest.mark.asyncio
+async def test_systems_for_paths_with_no_paths_reads_nothing():
+    lister = AsyncMock(return_value=[])
+    with patch("scribe.services.systems.list_systems", lister):
+        from scribe.services.systems import systems_for_paths
+        assert await systems_for_paths(1, 5, ["", "  "]) == []
+    lister.assert_not_awaited()
+
+
+@pytest.mark.asyncio
+async def test_update_refuses_a_bad_pattern_before_touching_the_row():
+    with patch("scribe.services.systems.async_session") as mock_cls:
+        from scribe.services.systems import update_system
+        with pytest.raises(ValueError):
+            await update_system(1, 9, path_patterns=["../elsewhere"])
+    mock_cls.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_update_with_an_empty_list_clears_the_patterns():
+    """`[]` is a value, not "leave unchanged" — the service skips only None."""
+    system = MagicMock(deleted_at=None, project_id=5, path_patterns=["src/old"])
+    session = make_mock_session()
+    session.get = AsyncMock(return_value=system)
+    with patch("scribe.services.systems.async_session", return_value=session), \
+         patch("scribe.services.systems.access") as acc, \
+         patch("scribe.services.systems.embed_system"):
+        acc.can_write_project = AsyncMock(return_value=True)
+        from scribe.services.systems import update_system
+        await update_system(1, 9, path_patterns=[])
+    assert system.path_patterns == []
+
+
+@pytest.mark.asyncio
+async def test_create_stores_tidied_patterns():
+    mock_session = make_mock_session()
+    captured = {}
+    mock_session.add = MagicMock(side_effect=lambda obj: captured.update(
+        patterns=getattr(obj, "path_patterns", "MISSING")))
+    with patch("scribe.services.systems.async_session", return_value=mock_session), \
+         patch("scribe.services.systems.access") as acc, \
+         patch("scribe.services.systems.embed_system"):
+        acc.can_write_project = AsyncMock(return_value=True)
+        from scribe.services.systems import create_system
+        await create_system(1, 5, "Billing", path_patterns=["./src/billing/"])
+    assert captured["patterns"] == ["src/billing"]
+
+
+def test_system_to_dict_carries_its_patterns():
+    from scribe.models.system import System
+    system = System(id=1, user_id=1, project_id=5, name="Billing",
+                    path_patterns=["src/billing"])
+    assert system.to_dict()["path_patterns"] == ["src/billing"]
+    assert System(id=2, user_id=1, project_id=5, name="X").to_dict()["path_patterns"] == []