feat(snippets): reverse lookup — find snippets by repo/path/symbol

"What canonical helpers already live in this file?" was unanswerable:
location lived only in the body markdown. It is now a jsonpath containment
query over the `notes.data` mirror added by migration 0070.

- One predicate in two dialects in services/knowledge.py: SQL (`data @?`,
  applied in the browse arm and the keyword arm before count/pagination, so
  totals stay honest) and Python (`location_matches`, for the semantic arm
  which post-filters candidates it already holds). Both must change together.
- Parts are ANDed within a SINGLE locations entry — repo A in one entry and
  path B in another is not "recorded at A/B". `path` also matches as a
  directory prefix, via jsonpath `starts with` rather than `@>`, which the
  same GIN index serves.
- `repo`/`path`/`symbol` reach the service, the REST list and the MCP tool
  under one name with one default (rule #33); the MCP docstring teaches the
  place form, and so does the reusing-code skill (plugin.json bumped).
- UI: a Location disclosure beside the snippet search, with its own empty
  state — "nothing kept there, so what you're about to write is new."

Settles #2083's open question (pre-0070 NULL `data`) by backfilling after
all: `backfill_snippet_data` runs at startup, deriving the mirror from the
body with the same parser the read path trusts. 0070's caution was about
mangling a hand-edited body; this never touches the body. The alternative
was a permanent second body-regex arm, or a query that silently answers
"nothing here" for an old snippet and gets the helper written twice.

Refs #2083, milestone #232.

frontend/src/api/snippets.ts

@@ -80,13 +80,26 @@ export interface SnippetInput {
   force?: boolean;
 }
 
+/** `repo`/`path`/`symbol` are the reverse lookup — "what already lives here?"
+ *  They must all match the same recorded location; `path` also matches anything
+ *  beneath it. Combinable with `q`. */
 export async function listSnippets(
-  params: { q?: string; tag?: string; projectId?: number | null } = {},
+  params: {
+    q?: string;
+    tag?: string;
+    projectId?: number | null;
+    repo?: string;
+    path?: string;
+    symbol?: string;
+  } = {},
 ): Promise<{ snippets: SnippetListItem[]; total: number }> {
   const qs = new URLSearchParams();
   if (params.q) qs.set("q", params.q);
   if (params.tag) qs.set("tag", params.tag);
   if (params.projectId) qs.set("project_id", String(params.projectId));
+  if (params.repo) qs.set("repo", params.repo);
+  if (params.path) qs.set("path", params.path);
+  if (params.symbol) qs.set("symbol", params.symbol);
   const query = qs.toString();
   return apiGet(`/api/snippets${query ? `?${query}` : ""}`);
 }

frontend/src/views/SnippetListView.vue

@@ -13,6 +13,27 @@ const error = ref<string | null>(null);
 const search = ref("");
 let searchTimer: ReturnType<typeof setTimeout> | undefined;
 
+// Reverse lookup — "what already lives here?" All three must match the same
+// recorded location; path also matches anything beneath it.
+const showLocationFilter = ref(false);
+const locRepo = ref("");
+const locPath = ref("");
+const locSymbol = ref("");
+const locationActive = computed(
+  () => !!(locRepo.value.trim() || locPath.value.trim() || locSymbol.value.trim()),
+);
+function clearLocation() {
+  locRepo.value = "";
+  locPath.value = "";
+  locSymbol.value = "";
+  loadSnippets();
+}
+function toggleLocationFilter() {
+  showLocationFilter.value = !showLocationFilter.value;
+  // Collapsing while filtered would hide why the list is short.
+  if (!showLocationFilter.value && locationActive.value) clearLocation();
+}
+
 // Multi-select → merge
 const selectMode = ref(false);
 const selectedIds = ref<Set<number>>(new Set());
@@ -70,7 +91,12 @@ async function loadSnippets() {
   loading.value = true;
   error.value = null;
   try {
-    const data = await listSnippets({ q: search.value.trim() || undefined });
+    const data = await listSnippets({
+      q: search.value.trim() || undefined,
+      repo: locRepo.value.trim() || undefined,
+      path: locPath.value.trim() || undefined,
+      symbol: locSymbol.value.trim() || undefined,
+    });
     snippets.value = data.snippets;
   } catch {
     error.value = "Couldn't load your snippets.";
@@ -84,6 +110,9 @@ function onSearchInput() {
   clearTimeout(searchTimer);
   searchTimer = setTimeout(loadSnippets, 300);
 }
+// Same debounce for the location fields — typing a path shouldn't fire a query
+// per keystroke.
+const onLocationInput = onSearchInput;
 
 onMounted(loadSnippets);
 
@@ -127,6 +156,48 @@ function languageOf(tags: string[]): string {
         @input="onSearchInput"
         @keydown.enter="loadSnippets"
       />
+      <button
+        class="btn-ghost"
+        :class="{ 'filter-on': locationActive }"
+        :aria-expanded="showLocationFilter"
+        aria-controls="location-filter"
+        @click="toggleLocationFilter"
+      >
+        <!-- Say it in the label, not only in the accent — the state has to reach
+             a screen reader too. -->
+        {{ locationActive ? "Location · filtering" : "Location" }}
+      </button>
+    </div>
+
+    <!-- Reverse lookup: what's already kept in this repo / file / symbol. -->
+    <div v-if="showLocationFilter" id="location-filter" class="location-row">
+      <input
+        v-model="locRepo"
+        class="loc-input"
+        placeholder="repo"
+        aria-label="Filter by repo"
+        @input="onLocationInput"
+        @keydown.enter="loadSnippets"
+      />
+      <input
+        v-model="locPath"
+        class="loc-input loc-input-wide"
+        placeholder="path — matches the file or anything under it"
+        aria-label="Filter by path"
+        @input="onLocationInput"
+        @keydown.enter="loadSnippets"
+      />
+      <input
+        v-model="locSymbol"
+        class="loc-input"
+        placeholder="symbol"
+        aria-label="Filter by symbol"
+        @input="onLocationInput"
+        @keydown.enter="loadSnippets"
+      />
+      <button v-if="locationActive" class="loc-clear" @click="clearLocation">
+        Clear
+      </button>
     </div>
 
     <div v-if="loading" class="skeleton-grid">
@@ -138,15 +209,24 @@ function languageOf(tags: string[]): string {
     <div v-else-if="snippets.length === 0" class="empty-state-rich">
       <div class="empty-icon">❭_</div>
       <p class="empty-title">
-        {{ search.trim() ? "No snippets match your search" : "No snippets kept yet" }}
+        {{ locationActive
+          ? "Nothing kept at that location yet"
+          : search.trim()
+            ? "No snippets match your search"
+            : "No snippets kept yet" }}
       </p>
       <p class="empty-sub">
-        {{ search.trim()
+        {{ locationActive
+          ? "No recorded snippet lives there — so whatever you're about to write is new. Widen the path, or clear the filter."
+          : search.trim()
             ? "Try a different term, or clear the search."
             : "Record a reusable function or component and it will be offered back to you later." }}
       </p>
+      <button v-if="locationActive" class="empty-action" @click="clearLocation">
+        Clear location filter
+      </button>
       <button
-        v-if="!search.trim()"
+        v-else-if="!search.trim()"
         class="empty-action"
         @click="router.push('/snippets/new')"
       >
@@ -278,6 +358,62 @@ function languageOf(tags: string[]): string {
 
 .search-row {
   margin-bottom: 1.25rem;
+  display: flex;
+  gap: 0.5rem;
+  align-items: center;
+  flex-wrap: wrap;
+}
+/* Filter is engaged — the accent marks "you are here", per the design system. */
+.filter-on {
+  border-color: var(--color-primary);
+  color: var(--color-primary);
+}
+
+.location-row {
+  display: flex;
+  gap: 0.5rem;
+  align-items: center;
+  flex-wrap: wrap;
+  margin: -0.5rem 0 1.25rem;
+}
+.loc-input {
+  flex: 1 1 8rem;
+  min-width: 0;
+  max-width: 12rem;
+  padding: 0.4rem 0.65rem;
+  border: 1px solid var(--color-border);
+  border-radius: var(--radius-sm);
+  background: var(--color-bg);
+  color: var(--color-text);
+  font-size: 0.85rem;
+  font-family: var(--font-mono, ui-monospace, "JetBrains Mono", monospace);
+  box-sizing: border-box;
+}
+.loc-input-wide {
+  flex: 2 1 16rem;
+  max-width: 26rem;
+}
+.loc-input::placeholder {
+  font-family: inherit;
+  color: var(--color-text-muted);
+}
+.loc-input:focus {
+  outline: none;
+  border-color: var(--color-primary);
+  box-shadow: var(--focus-ring);
+}
+.loc-clear {
+  padding: 0.4rem 0.65rem;
+  border: none;
+  background: transparent;
+  color: var(--color-text-secondary);
+  font-size: 0.85rem;
+  font-family: inherit;
+  cursor: pointer;
+  text-decoration: underline;
+}
+.loc-clear:hover {
+  color: var(--color-text);
 }
 .search-input {
   width: 100%;

plugin/.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "scribe",
   "description": "Scribe system-of-record for Claude Code: MCP tools over your notes/tasks/projects/rules, a session-start push channel that surfaces your always-on rules + active-project context, process-skills (writing-plans, systematic-debugging, verification, brainstorming, reusing-code), and your saved Scribe Processes auto-surfaced as skills (/scribe:sync). Replaces superpowers + file-memory with one app-backed plugin.",
-  "version": "0.1.16",
+  "version": "0.1.17",
   "author": { "name": "Bryan Van Deusen" },
   "mcpServers": {
     "scribe": {

plugin/skills/reusing-code/SKILL.md

@@ -20,6 +20,14 @@ through recall/auto-inject; this skill is the active reflex around that.
   `list_snippets` searches every project by default; that's deliberate, since a
   helper you need here was quite possibly written somewhere else. Narrow with
   `project_id` only when you specifically want this project's own.
+- **About to edit an existing file? Ask by place, not just by meaning.**
+  `list_snippets(repo="…", path="…")` answers "what canonical helpers are already
+  recorded here?" — `path` matches the exact file or anything beneath it, so
+  `path="frontend/src"` covers the whole tree. Cheaper and sharper than a
+  wording search when you already know where the code is going, and it catches
+  the helper you'd otherwise duplicate a few lines down. `symbol="…"` narrows
+  further, and all three must match the same recorded location. Combine with `q`
+  to ask both at once.
 - If a snippet fits, pull it in full with `get_snippet(id)` and reuse it — its
   `location` points at the reference implementation. Adapt, don't re-derive.
 - If auto-inject already surfaced a snippet title that looks relevant, that's

src/scribe/app.py

@@ -170,6 +170,15 @@ def create_app() -> Quart:
                 await backfill_note_embeddings()
             except Exception:
                 logger.warning("Embedding backfill failed", exc_info=True)
+            # Snippets written before migration 0070 have no `notes.data` mirror,
+            # and the location reverse lookup queries that column — an unfilled
+            # row would read as "no snippet here" rather than as a gap. Separate
+            # try block so neither backfill can skip the other.
+            try:
+                from scribe.services.snippets import backfill_snippet_data
+                await backfill_snippet_data()
+            except Exception:
+                logger.warning("Snippet data backfill failed", exc_info=True)
 
         asyncio.create_task(_delayed_backfill())
 

src/scribe/mcp/tools/snippets.py

@@ -19,9 +19,16 @@ from scribe.services import systems as systems_svc
 
 async def list_snippets(
     q: str = "", tag: str = "", limit: int = 50, project_id: int = 0,
+    repo: str = "", path: str = "", symbol: str = "",
 ) -> dict:
     """List recorded snippets (reusable functions/components).
 
+    Two ways to ask, usable together: by MEANING (`q` — "what do I need this code
+    to do?") and by PLACE (`repo`/`path`/`symbol` — "what canonical helpers
+    already live in the file I'm about to edit?"). Reach for the place form
+    before you write or change code in a file: it is the cheap way to find prior
+    art you'd otherwise duplicate a few lines down.
+
     Args:
         q: Free-text search across name + body (optional). Matches on meaning as
             well as wording, so describe what you need the code to DO.
@@ -30,6 +37,16 @@ async def list_snippets(
         project_id: Narrow to one project. 0 (default) searches every project —
             usually what you want, since a helper you need here may well have
             been written somewhere else.
+        repo: Narrow to snippets recorded in this repo, matched exactly — the
+            same repo string used when recording, e.g. "Scribe".
+        path: Narrow to snippets recorded at this path. Matches the exact file
+            OR anything beneath it, so "frontend/src" finds
+            "frontend/src/lib/x.ts" as well as itself.
+        symbol: Narrow to snippets recorded under this symbol name, exactly.
+
+    `repo`/`path`/`symbol` must all match the SAME recorded location, so a
+    snippet that lives in repo A and, separately, at path B in another repo is
+    not returned for repo=A + path=B.
 
     Returns {"snippets": [{id, title, tags, preview}], "total": int}. The title
     reads "name — when to reach for it"; open one in full with get_snippet(id).
@@ -44,6 +61,7 @@ async def list_snippets(
     items, total = await snippets_svc.list_snippets(
         uid, q=q or None, tag=tag, limit=max(1, min(limit, 100)),
         project_id=project_id or None,
+        repo=repo, path=path, symbol=symbol,
     )
     return {
         "snippets": await access_svc.label_shared_items(uid, items),

src/scribe/routes/snippets.py

@@ -56,9 +56,15 @@ async def list_snippets_route():
         project_id = int(request.args.get("project_id", 0) or 0) or None
     except (TypeError, ValueError):
         project_id = None
+    # Reverse lookup — "what already lives here?" Empty args are ignored, so the
+    # plain list is unchanged.
+    repo = request.args.get("repo", "")
+    path = request.args.get("path", "")
+    symbol = request.args.get("symbol", "")
     limit, offset = parse_pagination()
     items, total = await snippets_svc.list_snippets(
         uid, q=q, tag=tag, limit=limit, offset=offset, project_id=project_id,
+        repo=repo, path=path, symbol=symbol,
     )
     # Mark rows owned by someone else so the UI can show whose they are — an
     # unmarked row in your own list reads as one you recorded and vetted.

src/scribe/services/knowledge.py

@@ -15,6 +15,7 @@ The asymmetry is the point. A record that appears unasked reads as one you
 endorsed, so a one-off direct share has to be searched for rather than arriving
 in your ambient lists.
 """
+import json
 import logging
 
 from sqlalchemy import func, select
@@ -28,6 +29,85 @@ logger = logging.getLogger(__name__)
 _SNIPPET_LEN = 200
 
 
+# --- the location filter (reverse lookup, #2083) ------------------------------
+#
+# ONE predicate in two dialects: "this record carries a location matching every
+# part asked for." The SQL form runs in the browse arm and the keyword arm,
+# before the count and the page slice, so totals stay honest; the Python form
+# runs in the semantic arm, which post-filters candidates it already holds in
+# memory. THE TWO MUST CHANGE TOGETHER — a filter only one arm applies makes a
+# snippet findable by wording and invisible by location, which is exactly the
+# split tests/test_retrieval_scopes.py exists to prevent.
+#
+# Semantics, both dialects:
+#   - parts are ANDed WITHIN a single location entry, never across the list. A
+#     snippet whose first location is in repo A and whose second is at path B
+#     does not answer repo=A + path=B — it was never in that place.
+#   - `path` matches exactly OR as a directory prefix: "frontend/src" finds
+#     "frontend/src/lib/x.ts". Prefix is the one part a GIN containment lookup
+#     can't serve (migration 0070), which is why this is a jsonpath `@?` rather
+#     than `@>` — jsonpath `starts with` is index-served by the same GIN index.
+#
+# The filter reads `notes.data`, so it only sees rows carrying that mirror.
+# Rows written before migration 0070 are populated once at startup by
+# snippets.backfill_snippet_data — without that, this query would answer "no
+# snippets here" for an old snippet and the caller would write the helper again.
+
+LOCATION_KEYS = ("repo", "path", "symbol")
+
+
+def location_parts(repo: str = "", path: str = "", symbol: str = "") -> dict[str, str]:
+    """The non-empty, stripped location parts asked for; {} when none were."""
+    given = {"repo": repo, "path": path, "symbol": symbol}
+    return {k: (v or "").strip() for k, v in given.items() if (v or "").strip()}
+
+
+def _path_matches(have: str, want: str) -> bool:
+    """Exact, or `have` sits somewhere under the `want` directory."""
+    return have == want or have.startswith(want.rstrip("/") + "/")
+
+
+def location_matches(data: dict | None, parts: dict[str, str]) -> bool:
+    """Python dialect of the location predicate. Keep in step with _location_clause."""
+    if not parts:
+        return True
+    for loc in (data or {}).get("locations") or []:
+        if all(
+            _path_matches((loc.get(key) or "").strip(), want)
+            if key == "path"
+            else (loc.get(key) or "").strip() == want
+            for key, want in parts.items()
+        ):
+            return True
+    return False
+
+
+def location_jsonpath(parts: dict[str, str]) -> str:
+    """The jsonpath behind the SQL dialect — one `locations` entry matching all parts.
+
+    Values are embedded as JSON string literals (jsonpath uses JSON quoting), so
+    a repo or path carrying a quote can't break out of the expression. The keys
+    are our own fixed set, never caller input.
+    """
+    filters = []
+    for key in LOCATION_KEYS:
+        if key not in parts:
+            continue
+        want = parts[key]
+        literal = json.dumps(want)
+        if key == "path":
+            prefix = json.dumps(want.rstrip("/") + "/")
+            filters.append(f"(@.path == {literal} || @.path starts with {prefix})")
+        else:
+            filters.append(f"@.{key} == {literal}")
+    return f"$.locations[*] ? ({' && '.join(filters)})"
+
+
+def _location_clause(parts: dict[str, str]):
+    """SQL dialect of the location predicate. Keep in step with location_matches."""
+    return Note.data.path_exists(location_jsonpath(parts))
+
+
 def _note_to_item(note: Note) -> dict:
     item: dict = {
         "id": note.id,
@@ -80,18 +160,24 @@ async def query_knowledge(
     limit: int,
     offset: int,
     project_id: int | None = None,
+    locations: dict[str, str] | None = None,
 ) -> tuple[list[dict], int]:
     """Query knowledge objects (non-task notes) with filters.
 
     `project_id` narrows to one project (None = every project).
 
+    `locations` narrows to records whose `data.locations` holds an entry matching
+    every part given — build it with `location_parts(repo=…, path=…, symbol=…)`.
+    Today only snippets carry locations, but the column is general, so the filter
+    lives here with the query rather than in one type's service.
+
     Returns (items, total_count).
     """
     # Semantic search path — scores take priority over sort
     if q:
         return await _semantic_knowledge_search(
             user_id, q, note_type=note_type, tags=tags, limit=limit,
-            offset=offset, project_id=project_id,
+            offset=offset, project_id=project_id, locations=locations,
         )
 
     # No query = browsing. Narrower scope: a record shared directly with the
@@ -107,6 +193,9 @@ async def query_knowledge(
         for tag in tags:
             base = base.where(Note.tags.contains([tag]))
 
+        if locations:
+            base = base.where(_location_clause(locations))
+
         # Count before pagination
         count_stmt = select(func.count()).select_from(base.subquery())
         total: int = (await session.execute(count_stmt)).scalar_one()
@@ -134,6 +223,7 @@ async def _semantic_knowledge_search(
     limit: int,
     offset: int,
     project_id: int | None = None,
+    locations: dict[str, str] | None = None,
 ) -> tuple[list[dict], int]:
     """Hybrid search: keyword matches first (title/body ILIKE), then semantic results.
 
@@ -167,6 +257,8 @@ async def _semantic_knowledge_search(
                 base = base.where(Note.project_id == project_id)
             for tag in tags:
                 base = base.where(Note.tags.contains([tag]))
+            if locations:
+                base = base.where(_location_clause(locations))
             # Title matches first, then body-only matches, newest first within each
             base = base.order_by(
                 Note.title.ilike(pattern).desc(),
@@ -204,6 +296,11 @@ async def _semantic_knowledge_search(
                 continue
             if tags and not all(t in (note.tags or []) for t in tags):
                 continue
+            # The Python dialect of the same predicate the SQL arms apply above —
+            # these candidates arrive already fetched, so there's no query to
+            # narrow. See the comment on location_matches.
+            if locations and not location_matches(note.data, locations):
+                continue
             semantic_notes.append(note)
     except Exception:
         logger.warning("Semantic search unavailable, using keyword results only", exc_info=True)

src/scribe/services/snippets.py

@@ -5,10 +5,10 @@ component recorded once so a later session can recall it before writing a
 one-off. It carries a name, language, signature, canonical location
 (repo · path · symbol), a one-line "when to reach for it", and the code itself.
 
-Structured fields are stored as a **body-convention** — no dedicated column, so
+Structured fields are stored as a **body-convention** — the body is the readable
-a snippet inherits everything a note has (embeddings, ACL, project/System
+form and the thing that gets embedded, so a snippet inherits everything a note
-association, dedup) and, crucially, becomes eligible for semantic recall the
+has (embeddings, ACL, project/System association, dedup) and, crucially, becomes
-moment it's embedded:
+eligible for semantic recall the moment it's embedded:
 
   - ``title`` = ``"{name} — {when_to_use}"``. The title is exactly what the
     title-first auto-inject surfaces, so this one line self-describes the snippet
@@ -17,18 +17,30 @@ moment it's embedded:
   - ``body``  = templated markdown (When to use / Signature / Location, then a
     fenced code block).
 
+Since migration 0070 the same fields are ALSO written to ``notes.data`` (see
+``compose_data``) — a queryable mirror, not a second source of truth: it carries
+no code, and it exists so location/language can be indexed rather than regexed
+out of every body. Reads prefer it and fall back to the body parse.
+
 The public field API (name/language/signature/location/when_to_use/code) lives
-here, so the underlying storage could later move to a structured column without
+here, so callers (MCP tool, REST route, UI) never see which of the two a field
-changing any caller (MCP tool, REST route, UI).
+came from.
 """
 from __future__ import annotations
 
 import asyncio
+import logging
 import re
 
+from sqlalchemy import select
+
+from scribe.models import async_session
+from scribe.models.note import Note
 from scribe.services import knowledge as knowledge_svc
 from scribe.services import notes as notes_svc
 
+logger = logging.getLogger(__name__)
+
 SNIPPET_NOTE_TYPE = "snippet"
 SNIPPET_TAG = "snippet"
 
@@ -354,6 +366,63 @@ def snippet_fields(note) -> dict:
     return merged
 
 
+async def backfill_snippet_data(*, batch: int = 500) -> int:
+    """Populate `notes.data` for snippet rows that predate migration 0070.
+
+    Runs once at startup (see app.py). Returns how many rows were filled.
+
+    Migration 0070 deliberately left `data` NULL on existing rows, because
+    *reading* a snippet never needed it — `snippet_fields` falls back to parsing
+    the body. Querying does: the location reverse lookup (#2083) is a jsonpath
+    over this column, so a NULL-`data` snippet would be reported as "nothing
+    recorded here" and the caller would write the helper again — silently worse
+    than having no reverse lookup at all. Every consumer of the column
+    (reverse lookup, and the write-path trigger built on it) can then assume the
+    mirror is present instead of carrying a second body-regex arm.
+
+    This does not reverse 0070's actual caution, which was about mangling a
+    hand-edited *body*: the body is never touched here, only the mirror derived
+    from it, by the same parser the read path already trusts. Idempotent — a
+    filled row is skipped forever after, and a snippet with no structured fields
+    at all settles at `{}` rather than staying NULL and being re-scanned. Trashed
+    rows are included so a later restore comes back queryable.
+    """
+    filled = 0
+    async with async_session() as session:
+        while True:
+            rows = list(
+                (
+                    await session.execute(
+                        select(Note)
+                        .where(Note.note_type == SNIPPET_NOTE_TYPE)
+                        .where(Note.data.is_(None))
+                        .limit(batch)
+                    )
+                )
+                .scalars()
+                .all()
+            )
+            if not rows:
+                break
+            for note in rows:
+                fields = parse_snippet_fields(note.title, note.body, note.tags)
+                note.data = compose_data(
+                    name=fields["name"],
+                    when_to_use=fields["when_to_use"],
+                    signature=fields["signature"],
+                    language=fields["language"],
+                    locations=fields["locations"],
+                    merged_from=fields["merged_from"],
+                )
+            await session.commit()
+            filled += len(rows)
+            if len(rows) < batch:
+                break
+    if filled:
+        logger.info("Snippet data backfill: populated `data` for %d snippet(s)", filled)
+    return filled
+
+
 def snippet_to_dict(note) -> dict:
     """Note serialization plus a parsed ``snippet`` sub-object of structured
     fields, so callers get both the raw record and the typed view.
@@ -433,12 +502,20 @@ async def list_snippets(
     limit: int = 50,
     offset: int = 0,
     project_id: int | None = None,
+    repo: str = "",
+    path: str = "",
+    symbol: str = "",
 ) -> tuple[list[dict], int]:
     """List snippets (id/title/tags/preview dicts), most-recently-updated first.
 
     ``project_id`` narrows to one project; omit it to reach across every project
     — which is the point when the thing you're about to write was already solved
-    somewhere else."""
+    somewhere else.
+
+    ``repo`` / ``path`` / ``symbol`` are the reverse lookup: "what canonical
+    helpers already live here?" They narrow to snippets recorded at a matching
+    location, ANDed within one location entry, with ``path`` also matching as a
+    directory prefix. Combinable with ``q`` — search *and* place."""
     return await knowledge_svc.query_knowledge(
         user_id=user_id,
         note_type=SNIPPET_NOTE_TYPE,
@@ -448,6 +525,8 @@ async def list_snippets(
         limit=max(1, min(limit, 100)),
         offset=max(0, offset),
         project_id=project_id,
+        locations=knowledge_svc.location_parts(repo=repo, path=path, symbol=symbol)
+        or None,
     )
 
 

tests/test_integration_snippet_locations.py

@@ -0,0 +1,299 @@
+"""Real-Postgres integration test for the snippet location reverse lookup (#2083).
+
+Runs only in the CI integration lane (real Postgres, schema built by
+`alembic upgrade head`, which includes migration 0070's `notes.data` + GIN index).
+This exercises what the unit mocks cannot:
+
+  - the jsonpath `@?` containment behind `_location_clause` — including
+    `starts with` for a path prefix, and the fact that parts must match within a
+    SINGLE `locations` entry;
+  - that the SQL dialect and the Python dialect (`location_matches`, used by the
+    semantic arm) return the SAME rows. Those two must never drift, or a snippet
+    is findable by wording and invisible by location;
+  - `backfill_snippet_data`, which is what stops a pre-0070 snippet from being
+    silently reported as "nothing recorded here."
+"""
+from unittest.mock import AsyncMock, patch
+
+import pytest
+import pytest_asyncio
+from sqlalchemy import delete, select
+
+from scribe.models import async_session, engine
+from scribe.models.note import Note
+from scribe.models.user import User
+from scribe.services.knowledge import location_matches, location_parts
+from scribe.services.snippets import (
+    SNIPPET_NOTE_TYPE,
+    backfill_snippet_data,
+    compose_body,
+    compose_data,
+    list_snippets,
+    snippet_fields,
+)
+
+pytestmark = pytest.mark.integration
+
+
+@pytest_asyncio.fixture(autouse=True)
+async def _dispose_engine():
+    # Per-loop pool: dispose after each test (see test_integration_db_maintenance).
+    yield
+    await engine.dispose()
+
+
+def _loc(repo="", path="", symbol=""):
+    return {"repo": repo, "path": path, "symbol": symbol}
+
+
+@pytest_asyncio.fixture
+async def seeded():
+    """A user with four snippets covering the cases the filter has to separate.
+
+    Returns (user_id, {label: note_id}).
+    """
+    async with async_session() as s:
+        user = User(username="snippet_loc_itest")
+        s.add(user)
+        await s.flush()
+
+        def _snippet(name, locations, code="return 1"):
+            return Note(
+                user_id=user.id,
+                note_type=SNIPPET_NOTE_TYPE,
+                title=f"{name} — does a thing",
+                body=compose_body(code=code, language="python", locations=locations),
+                tags=["python", "snippet"],
+                data=compose_data(name=name, language="python", locations=locations),
+            )
+
+        nested = _snippet("nested", [_loc("Scribe", "frontend/src/lib/x.ts", "helper")])
+        sibling = _snippet("sibling", [_loc("Scribe", "frontend/srcmap.ts", "other")])
+        # Two locations, deliberately crossed: repo Scribe at src/a.py and repo
+        # Portal at src/b.py. repo=Scribe + path=src/b.py must NOT match it.
+        multi = _snippet(
+            "multi",
+            [_loc("Scribe", "src/a.py", "alpha"), _loc("Portal", "src/b.py", "beta")],
+        )
+        # No structured location at all — must never satisfy a location filter,
+        # and must not error the query either.
+        placeless = _snippet("placeless", [])
+        # A plain note (not a snippet) with no `data` — proves the jsonpath
+        # operator tolerates NULL rather than raising.
+        plain = Note(user_id=user.id, title="plain", body="no data here")
+
+        s.add_all([nested, sibling, multi, placeless, plain])
+        await s.commit()
+        ids = (
+            user.id,
+            {
+                "nested": nested.id,
+                "sibling": sibling.id,
+                "multi": multi.id,
+                "placeless": placeless.id,
+                "plain": plain.id,
+            },
+        )
+    yield ids
+    user_id = ids[0]
+    async with async_session() as s:
+        await s.execute(delete(Note).where(Note.user_id == user_id))
+        await s.execute(delete(User).where(User.id == user_id))
+        await s.commit()
+
+
+async def _ids_for(user_id: int, **parts) -> set[int]:
+    items, total = await list_snippets(user_id, **parts)
+    assert total == len(items), "total must match the filtered page, not the whole list"
+    return {i["id"] for i in items}
+
+
+@pytest.mark.asyncio
+async def test_repo_filter_finds_every_snippet_recorded_in_it(seeded):
+    user_id, ids = seeded
+    found = await _ids_for(user_id, repo="Scribe")
+    assert found == {ids["nested"], ids["sibling"], ids["multi"]}
+    assert ids["placeless"] not in found
+
+
+@pytest.mark.asyncio
+async def test_exact_path_finds_only_that_file(seeded):
+    user_id, ids = seeded
+    assert await _ids_for(user_id, path="frontend/src/lib/x.ts") == {ids["nested"]}
+
+
+@pytest.mark.asyncio
+async def test_path_prefix_reaches_into_subdirectories(seeded):
+    user_id, ids = seeded
+    # ...and stops at the directory boundary: srcmap.ts is a sibling, not a child.
+    assert await _ids_for(user_id, path="frontend/src") == {ids["nested"]}
+    assert await _ids_for(user_id, path="frontend/src/") == {ids["nested"]}
+    assert await _ids_for(user_id, path="frontend") == {ids["nested"], ids["sibling"]}
+
+
+@pytest.mark.asyncio
+async def test_parts_must_match_within_one_location(seeded):
+    user_id, ids = seeded
+    assert await _ids_for(user_id, repo="Scribe", path="src/a.py") == {ids["multi"]}
+    # Same snippet, but repo and path belong to two different entries.
+    assert await _ids_for(user_id, repo="Scribe", path="src/b.py") == set()
+    assert await _ids_for(user_id, repo="Portal", path="src/b.py") == {ids["multi"]}
+
+
+@pytest.mark.asyncio
+async def test_symbol_filter_and_an_unrecorded_location(seeded):
+    user_id, ids = seeded
+    assert await _ids_for(user_id, symbol="helper") == {ids["nested"]}
+    assert await _ids_for(user_id, repo="NoSuchRepo") == set()
+
+
+@pytest.mark.asyncio
+async def test_no_location_filter_still_lists_everything(seeded):
+    """The filter is opt-in — a plain browse must not lose the placeless snippet."""
+    found = await _ids_for(user_id=seeded[0])
+    ids = seeded[1]
+    assert {ids["nested"], ids["sibling"], ids["multi"], ids["placeless"]} <= found
+    assert ids["plain"] not in found  # not a snippet
+
+
+@pytest.mark.asyncio
+async def test_keyword_arm_applies_the_location_filter(seeded):
+    """Search AND place compose. The embedder is stubbed out so this isolates the
+    keyword (ILIKE) arm, which is the second place the SQL clause has to appear."""
+    user_id, ids = seeded
+    with patch(
+        "scribe.services.embeddings.semantic_search_notes",
+        AsyncMock(return_value=[]),
+    ):
+        assert await _ids_for(user_id, q="nested", repo="Scribe") == {ids["nested"]}
+        # Matches the query but not the place.
+        assert await _ids_for(user_id, q="nested", repo="Portal") == set()
+
+
+@pytest.mark.asyncio
+async def test_semantic_arm_applies_the_location_filter(seeded):
+    """The semantic arm holds its candidates in memory, so it filters in Python.
+    A query that matches no title or body leaves only that arm in play."""
+    user_id, ids = seeded
+    async with async_session() as s:
+        rows = list(
+            (
+                await s.execute(
+                    select(Note)
+                    .where(Note.user_id == user_id)
+                    .where(Note.note_type == SNIPPET_NOTE_TYPE)
+                )
+            )
+            .scalars()
+            .all()
+        )
+    candidates = [(0.9, n) for n in rows]
+
+    with patch(
+        "scribe.services.embeddings.semantic_search_notes",
+        AsyncMock(return_value=candidates),
+    ):
+        # No keyword can match this, so every hit below came from the stub.
+        assert await _ids_for(user_id, q="zzzznomatch") == {
+            ids["nested"], ids["sibling"], ids["multi"], ids["placeless"],
+        }
+        assert await _ids_for(user_id, q="zzzznomatch", path="frontend/src") == {
+            ids["nested"],
+        }
+        assert await _ids_for(user_id, q="zzzznomatch", repo="Scribe", path="src/b.py") == set()
+
+
+@pytest.mark.asyncio
+async def test_sql_and_python_dialects_agree_on_the_same_rows(seeded):
+    """The drift guard: whatever the SQL arm returns, the Python arm must too."""
+    user_id, _ids = seeded
+    async with async_session() as s:
+        rows = list(
+            (
+                await s.execute(
+                    select(Note)
+                    .where(Note.user_id == user_id)
+                    .where(Note.note_type == SNIPPET_NOTE_TYPE)
+                )
+            )
+            .scalars()
+            .all()
+        )
+        by_id = {n.id: n.data for n in rows}
+
+    cases = [
+        {"repo": "Scribe"},
+        {"path": "frontend/src"},
+        {"path": "frontend/src/lib/x.ts"},
+        {"repo": "Scribe", "path": "src/a.py"},
+        {"repo": "Scribe", "path": "src/b.py"},
+        {"symbol": "beta"},
+        {"repo": "Scribe", "path": "frontend", "symbol": "helper"},
+    ]
+    for case in cases:
+        sql_ids = await _ids_for(user_id, **case)
+        parts = location_parts(**case)
+        python_ids = {nid for nid, data in by_id.items() if location_matches(data, parts)}
+        assert sql_ids == python_ids, f"dialects disagree on {case}"
+
+
+@pytest.mark.asyncio
+async def test_backfill_makes_a_pre_0070_snippet_findable_by_location(seeded):
+    """A snippet stored before migration 0070 has no `data`, so the location query
+    can't see it. Unfilled, it reads as "nothing recorded here" — the failure the
+    backfill exists to prevent."""
+    user_id, _ids = seeded
+    locations = [_loc("Legacy", "old/path/y.py", "legacy_helper")]
+    async with async_session() as s:
+        old = Note(
+            user_id=user_id,
+            note_type=SNIPPET_NOTE_TYPE,
+            title="legacy — recorded before the data column existed",
+            body=compose_body(code="return 2", language="python", locations=locations),
+            tags=["python", "snippet"],
+            data=None,
+        )
+        s.add(old)
+        await s.commit()
+        old_id = old.id
+
+    assert await _ids_for(user_id, repo="Legacy") == set()
+
+    filled = await backfill_snippet_data()
+    assert filled >= 1
+
+    assert await _ids_for(user_id, repo="Legacy") == {old_id}
+    assert await _ids_for(user_id, path="old/path") == {old_id}
+
+    # The mirror agrees with the body it was derived from, and the body is untouched.
+    async with async_session() as s:
+        row = (await s.execute(select(Note).where(Note.id == old_id))).scalar_one()
+        assert row.data["locations"] == locations
+        assert snippet_fields(row)["symbol"] == "legacy_helper"
+        assert "old/path/y.py" in row.body
+
+
+@pytest.mark.asyncio
+async def test_backfill_is_idempotent_and_settles_a_fieldless_snippet(seeded):
+    """Second run fills nothing, and a snippet with no structured fields lands at
+    `{}` rather than staying NULL and being rescanned on every boot."""
+    user_id, _ids = seeded
+    async with async_session() as s:
+        bare = Note(
+            user_id=user_id,
+            note_type=SNIPPET_NOTE_TYPE,
+            title="",
+            body="",
+            tags=[],
+            data=None,
+        )
+        s.add(bare)
+        await s.commit()
+        bare_id = bare.id
+
+    await backfill_snippet_data()
+    assert await backfill_snippet_data() == 0
+
+    async with async_session() as s:
+        row = (await s.execute(select(Note).where(Note.id == bare_id))).scalar_one()
+        assert row.data == {}

tests/test_routes_snippets.py

@@ -72,6 +72,19 @@ def test_project_scoping_reaches_every_caller():
     assert "project_id" in inspect.getsource(routes.list_snippets_route)
 
 
+def test_location_lookup_reaches_every_caller():
+    """The reverse lookup — "what already lives here?" — has to be askable from
+    both surfaces, or an agent and a human get different answers about the same
+    file (rule #33)."""
+    from scribe.mcp.tools import snippets as tools
+    from scribe.routes import snippets as routes
+    from scribe.services import snippets as svc
+    for key in ("repo", "path", "symbol"):
+        assert key in inspect.signature(svc.list_snippets).parameters
+        assert key in inspect.signature(tools.list_snippets).parameters
+        assert f'request.args.get("{key}"' in inspect.getsource(routes)
+
+
 def test_update_field_map_matches_service_kwargs():
     """Every field the PATCH route forwards must be a real update_snippet kwarg
     (rule #33 interface-contract parity)."""

tests/test_snippet_location_filter.py

@@ -0,0 +1,205 @@
+"""Tests for the snippet location reverse lookup (#2083).
+
+Covers the pure half of the predicate — `location_parts`, `location_matches`,
+`location_jsonpath` — plus the parameter plumbing across the three surfaces
+(service / REST route / MCP tool), which rule #33 requires to agree on names and
+defaults.
+
+The SQL half can only be proved against real Postgres — see
+tests/test_integration_snippet_locations.py, which also pins the two dialects to
+the same answers on the same rows.
+"""
+import inspect
+import json
+from unittest.mock import AsyncMock, patch
+
+import pytest
+
+from scribe.services.knowledge import (
+    LOCATION_KEYS,
+    location_jsonpath,
+    location_matches,
+    location_parts,
+)
+
+
+def _data(*locations: dict) -> dict:
+    return {"locations": list(locations)}
+
+
+# --- location_parts -----------------------------------------------------------
+
+def test_location_parts_keeps_only_what_was_asked_for():
+    assert location_parts() == {}
+    assert location_parts(repo="Scribe") == {"repo": "Scribe"}
+    assert location_parts(repo="  Scribe  ", path=" src/x.py ") == {
+        "repo": "Scribe", "path": "src/x.py",
+    }
+
+
+def test_location_parts_treats_whitespace_as_absent():
+    """An empty query-string arg must not filter the list down to nothing."""
+    assert location_parts(repo="   ", path="", symbol=None or "") == {}
+
+
+def test_location_parts_covers_every_location_key():
+    assert set(location_parts(repo="a", path="b", symbol="c")) == set(LOCATION_KEYS)
+
+
+# --- location_matches ---------------------------------------------------------
+
+def test_no_parts_matches_everything():
+    assert location_matches(None, {}) is True
+    assert location_matches(_data({"repo": "x", "path": "y", "symbol": "z"}), {}) is True
+
+
+def test_matches_exact_repo_path_and_symbol():
+    data = _data({"repo": "Scribe", "path": "src/scribe/x.py", "symbol": "helper"})
+    assert location_matches(data, {"repo": "Scribe"})
+    assert location_matches(data, {"path": "src/scribe/x.py"})
+    assert location_matches(data, {"symbol": "helper"})
+    assert location_matches(data, {"repo": "Scribe", "symbol": "helper"})
+
+
+def test_path_matches_as_a_directory_prefix():
+    data = _data({"repo": "Scribe", "path": "frontend/src/lib/x.ts", "symbol": ""})
+    assert location_matches(data, {"path": "frontend/src"})
+    assert location_matches(data, {"path": "frontend/src/"})
+    assert location_matches(data, {"path": "frontend/src/lib/x.ts"})
+
+
+def test_path_prefix_stops_at_a_directory_boundary():
+    """`frontend/src` must not match `frontend/srcmap.ts` — a sibling, not a child."""
+    data = _data({"repo": "Scribe", "path": "frontend/srcmap.ts", "symbol": ""})
+    assert not location_matches(data, {"path": "frontend/src"})
+
+
+def test_parts_must_all_match_the_same_location():
+    """Repo A in one entry and path B in another is not "recorded at A/B"."""
+    data = _data(
+        {"repo": "Scribe", "path": "src/a.py", "symbol": ""},
+        {"repo": "Portal", "path": "src/b.py", "symbol": ""},
+    )
+    assert location_matches(data, {"repo": "Scribe", "path": "src/a.py"})
+    assert not location_matches(data, {"repo": "Scribe", "path": "src/b.py"})
+
+
+def test_missing_or_empty_data_never_matches():
+    assert not location_matches(None, {"repo": "Scribe"})
+    assert not location_matches({}, {"repo": "Scribe"})
+    assert not location_matches({"locations": []}, {"repo": "Scribe"})
+    assert not location_matches({"name": "x"}, {"repo": "Scribe"})
+
+
+def test_blank_recorded_part_does_not_match_a_requested_one():
+    data = _data({"repo": "Scribe", "path": "", "symbol": ""})
+    assert not location_matches(data, {"repo": "Scribe", "symbol": "helper"})
+
+
+# --- location_jsonpath --------------------------------------------------------
+
+def test_jsonpath_filters_within_one_locations_entry():
+    expr = location_jsonpath({"repo": "Scribe", "symbol": "helper"})
+    assert expr.startswith("$.locations[*] ? (")
+    assert '@.repo == "Scribe"' in expr
+    assert '@.symbol == "helper"' in expr
+    assert " && " in expr
+
+
+def test_jsonpath_path_asks_for_exact_or_prefix():
+    expr = location_jsonpath({"path": "frontend/src"})
+    assert '@.path == "frontend/src"' in expr
+    assert '@.path starts with "frontend/src/"' in expr
+    assert " || " in expr
+
+
+def test_jsonpath_does_not_double_the_prefix_slash():
+    assert 'starts with "frontend/src/"' in location_jsonpath({"path": "frontend/src/"})
+
+
+def test_jsonpath_quotes_values_as_json_literals():
+    """A quote in a repo name must stay inside the literal, not end it."""
+    nasty = 'we"ird'
+    expr = location_jsonpath({"repo": nasty})
+    assert json.dumps(nasty) in expr
+    assert '\\"' in expr
+
+
+def test_jsonpath_emits_parts_in_a_fixed_key_order():
+    """Stable text keeps the query plan cacheable and the tests readable."""
+    a = location_jsonpath({"symbol": "s", "repo": "r", "path": "p"})
+    b = location_jsonpath({"repo": "r", "path": "p", "symbol": "s"})
+    assert a == b
+
+
+# --- the SQL dialect renders (shape only; behaviour is the integration test) ---
+
+def test_location_clause_renders_a_jsonpath_containment():
+    """Catches an API slip in the fast lane rather than waiting for Postgres —
+    the clause has to compile to `data @? :jsonpath` against the pg dialect."""
+    from sqlalchemy.dialects import postgresql
+
+    from scribe.services.knowledge import _location_clause
+
+    sql = str(_location_clause({"repo": "Scribe"}).compile(dialect=postgresql.dialect()))
+    assert "@?" in sql
+    assert "data" in sql
+
+
+# --- surface plumbing (rule #33) ---------------------------------------------
+
+def test_agent_and_service_surfaces_take_the_same_location_params():
+    from scribe.mcp.tools.snippets import list_snippets as mcp_list
+    from scribe.services.snippets import list_snippets as svc_list
+
+    for fn in (mcp_list, svc_list):
+        params = inspect.signature(fn).parameters
+        for key in LOCATION_KEYS:
+            assert key in params, f"{fn.__qualname__} is missing {key}"
+            assert params[key].default == "", f"{fn.__qualname__}.{key} default drifted"
+
+
+def test_route_forwards_the_location_args_by_name():
+    """The REST surface is the third caller; it must use the same arg names."""
+    from scribe.routes import snippets as routes
+    src = inspect.getsource(routes)
+    for key in LOCATION_KEYS:
+        assert f'request.args.get("{key}"' in src
+        assert f"{key}={key}" in src
+
+
+@pytest.mark.asyncio
+async def test_mcp_tool_passes_locations_through_to_the_service():
+    with patch("scribe.services.snippets.list_snippets",
+               new=AsyncMock(return_value=([], 0))) as m, \
+         patch("scribe.services.access.label_shared_items",
+               new=AsyncMock(return_value=[])):
+        from scribe.mcp.tools.snippets import list_snippets
+        await list_snippets(repo="Scribe", path="src/scribe", symbol="helper")
+    kwargs = m.await_args.kwargs
+    assert kwargs["repo"] == "Scribe"
+    assert kwargs["path"] == "src/scribe"
+    assert kwargs["symbol"] == "helper"
+
+
+@pytest.mark.asyncio
+async def test_service_sends_no_location_filter_when_none_was_asked_for():
+    """A plain list must not carry an empty filter — that would exclude every
+    row whose `data` has no locations at all."""
+    with patch("scribe.services.knowledge.query_knowledge",
+               new=AsyncMock(return_value=([], 0))) as m:
+        from scribe.services.snippets import list_snippets
+        await list_snippets(1)
+    assert m.await_args.kwargs["locations"] is None
+
+
+@pytest.mark.asyncio
+async def test_service_builds_the_filter_from_the_parts_given():
+    with patch("scribe.services.knowledge.query_knowledge",
+               new=AsyncMock(return_value=([], 0))) as m:
+        from scribe.services.snippets import list_snippets
+        await list_snippets(1, q="debounce", repo="Scribe", path=" src/ ")
+    kwargs = m.await_args.kwargs
+    assert kwargs["locations"] == {"repo": "Scribe", "path": "src/"}
+    # Search and place compose — the location filter must not drop the query.
+    assert kwargs["q"] == "debounce"