src/scribe/mcp/tools/snippets.py

@@ -127,12 +127,19 @@ async def create_snippet(
         force: Bypass the near-duplicate gate (see below).
 
     Returns the created snippet (including a parsed `snippet` field), OR — when a
-    near-duplicate snippet already exists and force is false — {"duplicate": true,
+    duplicate already exists and force is false — {"duplicate": true,
     "existing_id": ..., "message": ...} and nothing is created. When that happens
     and it really is the same reusable thing found in another place, prefer
     merge_snippets(existing_id, [new...]) — or record then merge — to unify them
     into ONE canonical record (which then carries every call site as a location),
     rather than forcing a second copy with force=true.
+
+    WHAT THE GATE MATCHES ON. Exact identity first — an existing snippet at the
+    same repo · path · symbol, or holding byte-identical code. Those are certain,
+    and force is almost never the right answer to them. Only then a semantic
+    check, held to a high bar so that VARIANTS of one component are not refused:
+    `.btn-primary` and `.btn-secondary` read alike and are two different things,
+    so record both (#2518).
     """
     if not (name or "").strip() or not (code or "").strip():
         raise ValueError("create_snippet requires a non-empty name and code")
@@ -148,6 +155,10 @@ async def create_snippet(
         dup = await dedup_svc.find_duplicate_note(
             uid, title, body, project_id=project_id or None,
             is_task=False, note_type=snippets_svc.SNIPPET_NOTE_TYPE,
+            # The artefact itself, not just its description — the gate compares
+            # location and code before it compares prose (#2518).
+            code=code,
+            locations=snippets_svc.resolve_locations(repo, path, symbol, locations),
         )
         if dup is not None:
             return dedup_svc.duplicate_response(dup, "snippet")

src/scribe/routes/snippets.py

@@ -112,6 +112,15 @@ async def create_snippet_route():
             project_id=project_id,
             is_task=False,
             note_type=snippets_svc.SNIPPET_NOTE_TYPE,
+            # Matched on the artefact — location and code — before prose, the
+            # same way the MCP create path does (#2518). Both surfaces must
+            # apply the identical gate or the web UI becomes the way to record
+            # a duplicate the agent would have been stopped from writing.
+            code=data.get("code", ""),
+            locations=snippets_svc.resolve_locations(
+                data.get("repo", ""), data.get("path", ""), data.get("symbol", ""),
+                data.get("locations"),
+            ),
         )
         if dup is not None:
             return jsonify(dedup_svc.duplicate_response(dup, "snippet")), 409

src/scribe/services/dedup.py

@@ -48,6 +48,27 @@ _MIN_BODY_FOR_SEMANTIC = 200
 # noise). Matches the 0.90 the pre-pivot dedup settled on.
 _SEMANTIC_THRESHOLD = 0.90
 
+# SNIPPETS ARE MEASURED DIFFERENTLY, and #2518 is why. A snippet's embedded
+# document is mostly PROSE ABOUT the code — name, when-to-reach-for-it,
+# signature, the comments explaining the choice — with the artefact itself a
+# minority of the text. Two measurements on the same corpus:
+#
+#   .btn-danger vs .btn-danger-outline   0.92   siblings, blocked (false positive)
+#   .btn-primary re-recorded verbatim
+#   under a different name              <0.90   a literal copy, ALLOWED THROUGH
+#
+# The second is the one that settles it. Identical code at an identical
+# repo·path·symbol sailed past the gate because the description differed, while
+# two deliberately-parallel variants were refused because theirs did not. The
+# arm is not mis-tuned; it is reading the wrong field, and no threshold fixes
+# that — lowering it blocks more siblings, raising it allows more copies.
+#
+# So: STRUCTURE decides, and the semantic arm becomes a backstop set above the
+# band where legitimate variants live (0.92 observed). It still catches a
+# genuine reword that shares neither location nor code, which is the case the
+# structural signals cannot see.
+_SNIPPET_SEMANTIC_THRESHOLD = 0.96
+
 
 @dataclass
 class DuplicateMatch:
@@ -58,25 +79,124 @@ class DuplicateMatch:
     reason: str        # "title" | "semantic"
 
 
+# How each signal describes itself when it blocks a write. The structural ones
+# are CERTAIN, so they say what was matched instead of hedging with "similar" —
+# and they point at merge, not update, because two records of one artefact is
+# what merge exists to fold back together.
+_REASON_PHRASING = {
+    "location": (
+        "is already recorded at that exact repo · path · symbol",
+        "Update it (update_{kind}), or if you meant to record a second call "
+        "site, use merge_snippets so one record carries both locations.",
+    ),
+    "code": (
+        "already holds identical code",
+        "Update it (update_{kind}) rather than keeping two copies that must "
+        "then be kept in step by hand.",
+    ),
+}
+
+
 def duplicate_response(dup: "DuplicateMatch", kind: str) -> dict:
     """Standard 'blocked — update instead' payload returned by a create tool
-    when the gate finds a near-duplicate. `kind` is 'note' or 'task' (drives the
+    when the gate finds a near-duplicate. `kind` is 'note', 'task' or 'snippet'
-    update_<kind> hint)."""
+    (drives the update_<kind> hint)."""
+    phrasing = _REASON_PHRASING.get(dup.reason)
+    if phrasing:
+        claim, advice = phrasing
+        message = (
+            f'An existing {kind} (id {dup.id}: "{dup.title}") {claim}. '
+            f"{advice.format(kind=kind)} If this really is a distinct {kind}, "
+            f"retry with force=true."
+        )
+    else:
+        message = (
+            f'A {dup.reason}-similar {kind} already exists (id {dup.id}: '
+            f'"{dup.title}"). Prefer UPDATING it (update_{kind}) over creating a '
+            f"near-duplicate. If this really is a distinct {kind}, retry with "
+            f"force=true."
+        )
     return {
         "duplicate": True,
         "existing_id": dup.id,
         "existing_title": dup.title,
         "similarity": dup.similarity,
         "match": dup.reason,
-        "message": (
+        "message": message,
-            f'A {dup.reason}-similar {kind} already exists (id {dup.id}: '
-            f'"{dup.title}"). Prefer UPDATING it (update_{kind}) over creating a '
-            f"near-duplicate. If this really is a distinct {kind}, retry with "
-            f"force=true."
-        ),
     }
 
 
+async def _find_snippet_by_structure(
+    user_id: int,
+    code: str,
+    locations: list[dict] | None,
+    project_id: int | None,
+) -> DuplicateMatch | None:
+    """Exact-identity duplicate of an incoming snippet, or None.
+
+    Two signals, both index-served off `notes.data` and both CERTAIN rather than
+    probabilistic — which is what the semantic arm could not be (#2518):
+
+      location  the same named thing in the same file. Requires BOTH path and
+                symbol: a path alone is a directory of many artefacts, and
+                matching on it would refuse every second snippet from one file.
+      code      byte-identical code, wherever it lives. Uses the same
+                fingerprint the drift check uses, so "identical" means the same
+                thing in both places.
+
+    Fail-open like the rest of this module: a failed lookup lets the write
+    through rather than blocking on an infrastructure problem.
+    """
+    from scribe.services.knowledge import location_jsonpath
+    from scribe.services.snippets import code_sha
+
+    identifying = [
+        loc for loc in (locations or [])
+        if (loc.get("path") or "").strip() and (loc.get("symbol") or "").strip()
+    ]
+    if not identifying and not (code or "").strip():
+        return None          # nothing to match on — don't open a session for it
+
+    def _scoped(stmt):
+        stmt = stmt.where(
+            Note.user_id == user_id,
+            Note.deleted_at.is_(None),
+            Note.note_type == SNIPPET_NOTE_TYPE,
+        )
+        # Same scoping rule as the title and semantic arms: a project's records
+        # compare only within that project, orphans only to orphans.
+        return (stmt.where(Note.project_id == project_id) if project_id is not None
+                else stmt.where(Note.project_id.is_(None)))
+
+    try:
+        async with async_session() as session:
+            for loc in identifying:
+                parts = {
+                    "path": (loc["path"]).strip(),
+                    "symbol": (loc["symbol"]).strip(),
+                }
+                repo = (loc.get("repo") or "").strip()
+                if repo:
+                    parts["repo"] = repo
+                stmt = _scoped(select(Note)).where(
+                    Note.data.path_exists(location_jsonpath(parts))
+                )
+                hit = (await session.execute(stmt.limit(1))).scalars().first()
+                if hit is not None:
+                    return DuplicateMatch(hit.id, hit.title, 1.0, "location")
+
+            if (code or "").strip():
+                stmt = _scoped(select(Note)).where(
+                    Note.data["code_sha"].astext == code_sha(code)
+                )
+                hit = (await session.execute(stmt.limit(1))).scalars().first()
+                if hit is not None:
+                    return DuplicateMatch(hit.id, hit.title, 1.0, "code")
+    except Exception:
+        logger.debug("snippet structural dedup skipped — query failed", exc_info=True)
+    return None
+
+
 async def find_duplicate_note(
     user_id: int,
     title: str,
@@ -84,11 +204,19 @@ async def find_duplicate_note(
     project_id: int | None = None,
     is_task: bool | None = None,
     note_type: str = "note",
+    code: str = "",
+    locations: list[dict] | None = None,
 ) -> DuplicateMatch | None:
     """Best near-duplicate of (title, body) within the same owner + project +
-    kind, or None. Title match first (cheap, exact), then semantic when the body
+    kind, or None. Title match first (cheap, exact), then — for snippets — the
-    is long enough to be meaningful. Never raises — embedder failure degrades to
+    structural signals, then semantic when the body is long enough to be
-    title-only (callers should still be able to create)."""
+    meaningful. Never raises — embedder failure degrades to title-only (callers
+    should still be able to create).
+
+    `code` and `locations` are the snippet's structured fields. They are ignored
+    for every other kind, and passing them is what lets the gate compare
+    ARTEFACTS rather than descriptions of artefacts (#2518).
+    """
     norm = " ".join((title or "").split()).lower()
 
     # --- Signal 1: normalized-title exact match (same scope) ---
@@ -118,7 +246,17 @@ async def find_duplicate_note(
             logger.debug("dedup title check skipped — query failed", exc_info=True)
             return None
 
-    # --- Signal 2: semantic similarity (only with a substantial body) ---
+    # --- Signal 2: structural identity (snippets only) ---
+    # Ahead of the semantic arm because it is exact: when it fires there is
+    # nothing to weigh, and its verdict is the one worth showing.
+    if note_type == SNIPPET_NOTE_TYPE:
+        structural = await _find_snippet_by_structure(
+            user_id, code, locations, project_id
+        )
+        if structural is not None:
+            return structural
+
+    # --- Signal 3: semantic similarity (only with a substantial body) ---
     if body and len(body.strip()) >= _MIN_BODY_FOR_SEMANTIC:
         query = f"{title}\n{body}".strip()
         # Scope the semantic check the same way as the title check: a record in
@@ -129,7 +267,9 @@ async def find_duplicate_note(
         hits = await embeddings_svc.semantic_search_notes(
             user_id, query, project_id=project_id, is_task=is_task,
             orphan_only=(project_id is None),
-            limit=3, threshold=_SEMANTIC_THRESHOLD,
+            limit=3,
+            threshold=(_SNIPPET_SEMANTIC_THRESHOLD
+                       if note_type == SNIPPET_NOTE_TYPE else _SEMANTIC_THRESHOLD),
             # Owner-only, deliberately: this gate BLOCKS a create and tells the
             # caller to update the match instead. Matching someone else's record
             # would refuse their write and point them at something they may not
@@ -222,6 +362,52 @@ def group_pairs(pairs: list[tuple[int, int, float]]) -> list[list[int]]:
                   key=lambda g: (-len(g), g[0]))
 
 
+def _symbols(data: dict | None) -> set[str]:
+    """Every symbol a snippet claims, from its indexed location mirror."""
+    return {
+        (loc.get("symbol") or "").strip()
+        for loc in (data or {}).get("locations") or []
+        if (loc.get("symbol") or "").strip()
+    }
+
+
+def _drop_sibling_pairs(
+    pairs: list[tuple[int, int, float]], records: dict[int, dict]
+) -> list[tuple[int, int, float]]:
+    """Remove pairs that are VARIANTS of one thing rather than copies of it.
+
+    Two snippets that both name a symbol, name DIFFERENT symbols, and hold
+    different code are two artefacts. The author asserted that by naming them
+    apart, and merging them would destroy a distinction someone made on purpose.
+
+    Without this, a design system's button family reports as a single merge set:
+    eight recipes, every direct pair over the floor, top score 0.92 (#2518).
+    They resemble each other because variants of one component are SUPPOSED to —
+    same selector prefix, same token families, deliberately parallel prose. The
+    similarity is read correctly; it just does not mean "duplicate".
+
+    THE COST, stated plainly: a helper genuinely recorded twice under two names
+    — `debounce` and `useDebouncedRef` — is no longer reported. That is real
+    recall lost. It is the better trade because the report is a merge PROPOSAL:
+    a missed pair costs a duplicate nobody was going to notice anyway, while a
+    wrong set invites an operator to collapse a component family in one click.
+    Same-symbol and no-symbol duplicates, which is how re-recording usually
+    looks, still report.
+    """
+    kept = []
+    for left, right, score in pairs:
+        left_data, right_data = records.get(left) or {}, records.get(right) or {}
+        left_syms, right_syms = _symbols(left_data), _symbols(right_data)
+        shas = (left_data.get("code_sha"), right_data.get("code_sha"))
+        identical_code = shas[0] is not None and shas[0] == shas[1]
+        # Both named, no name in common, and the code differs → siblings.
+        if (left_syms and right_syms and not (left_syms & right_syms)
+                and not identical_code):
+            continue
+        kept.append((left, right, score))
+    return kept
+
+
 async def find_duplicate_snippets(
     user_id: int, *, threshold: float | None = None, limit: int = _MAX_DUPLICATE_PAIRS
 ) -> dict:
@@ -280,21 +466,32 @@ async def find_duplicate_snippets(
     if not pairs:
         return {"groups": [], "pairs": [], "threshold": floor}
 
-    best: dict[tuple[int, int], float] = {(a, b): s for a, b, s in pairs}
+    # Titles + the structural fields, for presentation AND for the sibling
-    grouped = group_pairs(pairs)
+    # filter below. One fetch covers every id the scan proposed.
-
+    scanned = sorted({n for pair in pairs for n in pair[:2]})
-    # Titles for presentation. One fetch for every id in the report.
-    ids = sorted({n for g in grouped for n in g})
     titles: dict[int, str] = {}
+    records: dict[int, dict] = {}
     try:
         async with async_session() as session:
             rows = (await session.execute(
-                select(Note.id, Note.title).where(Note.id.in_(ids))
+                select(Note.id, Note.title, Note.data).where(Note.id.in_(scanned))
             )).all()
-            titles = {int(i): t for i, t in rows}
+            titles = {int(i): t for i, t, _ in rows}
+            records = {int(i): (d or {}) for i, _, d in rows}
     except Exception:
         logger.debug("duplicate report titles unavailable", exc_info=True)
 
+    # Fails OPEN, and the direction matters: with `records` empty the filter
+    # below keeps every pair, so a lookup failure degrades to the unfiltered
+    # report rather than to an empty one. A report that silently returns
+    # nothing reads as "your corpus is clean", which is the wrong lie.
+    pairs = _drop_sibling_pairs(pairs, records)
+    if not pairs:
+        return {"groups": [], "pairs": [], "threshold": floor}
+
+    best: dict[tuple[int, int], float] = {(a, b): s for a, b, s in pairs}
+    grouped = group_pairs(pairs)
+
     groups = []
     for members in grouped:
         scores = [

src/scribe/services/snippets.py

@@ -96,6 +96,27 @@ def _normalize_locations(locations: list[dict] | None) -> list[dict]:
     return out
 
 
+def resolve_locations(
+    repo: str = "", path: str = "", symbol: str = "",
+    locations: list[dict] | None = None,
+) -> list[dict]:
+    """The location list a caller meant, from either calling convention.
+
+    `locations` is the general form (one entry per call site); repo/path/symbol
+    are the single-location shorthand and apply only when `locations` was not
+    given — passing both is not a merge, it is the caller having decided.
+
+    Extracted because compose_body, create_snippet and the dedup gate must all
+    read the shorthand the SAME way. They each had their own copy of the
+    `if locations is None` fallback, which is fine until one of them gains a
+    rule the others don't — and the gate (#2518) is the one where a disagreement
+    would mean comparing a location the record won't actually be stored with.
+    """
+    if locations is None:
+        locations = [{"repo": repo, "path": path, "symbol": symbol}]
+    return _normalize_locations(locations)
+
+
 def _location_str(loc: dict) -> str:
     """`repo` · `path` · `symbol` — only the non-empty parts."""
     parts = [(loc.get(k) or "").strip() for k in ("repo", "path", "symbol")]
@@ -186,9 +207,7 @@ def compose_body(
     a back-compat shorthand for one location and are used only when ``locations``
     is not given.
     """
-    if locations is None:
+    locs = resolve_locations(repo, path, symbol, locations)
-        locations = [{"repo": repo, "path": path, "symbol": symbol}]
-    locs = _normalize_locations(locations)
 
     header: list[str] = []
     if (when_to_use or "").strip():
@@ -601,8 +620,7 @@ async def create_snippet(
     """Create a snippet note (embedded on create for immediate recall). Returns
     the created Note. Pass ``locations`` for the multi-location case; the single
     ``repo``/``path``/``symbol`` are the one-location shorthand."""
-    if locations is None:
+    locations = resolve_locations(repo, path, symbol, locations)
-        locations = [{"repo": repo, "path": path, "symbol": symbol}]
     note = await notes_svc.create_note(
         user_id,
         title=compose_title(name, when_to_use),

tests/test_services_dedup.py

@@ -110,3 +110,175 @@ def test_duplicate_response_shape():
     assert r["match"] == "title"
     assert "force=true" in r["message"]
     assert "update_task" in r["message"]
+
+
+# --- snippet structural identity (#2518) -------------------------------------
+#
+# The gate used to compare a snippet's rendered DOCUMENT, which is mostly prose
+# about the code. Measured on the button corpus, that failed in both directions
+# at once: two deliberately-parallel variants were refused at 0.92, while a
+# verbatim re-record of one snippet under a different name scored below 0.90 and
+# was created. These tests pin the structural signals that replaced it.
+
+
+def _session_sequence(results):
+    """A mocked async_session() whose successive execute() calls yield `results`.
+
+    The single-result helper above can't express this: the structural check runs
+    a location query and then a code query, and the whole point is that they
+    answer differently.
+    """
+    s = AsyncMock()
+    s.__aenter__ = AsyncMock(return_value=s)
+    s.__aexit__ = AsyncMock(return_value=False)
+    wrapped = []
+    for note in results:
+        r = MagicMock()
+        r.scalars.return_value.first.return_value = note
+        wrapped.append(r)
+    s.execute = AsyncMock(side_effect=wrapped)
+    return s
+
+
+@pytest.mark.asyncio
+async def test_same_location_is_a_duplicate_however_it_is_described():
+    """The measured false NEGATIVE: identical code at an identical
+    repo·path·symbol was created because the prose around it differed."""
+    existing = _fake_note(id=30, title=".btn-primary — a page's main action",
+                          note_type="snippet")
+    sem = AsyncMock()
+    with patch("scribe.services.dedup.async_session",
+               return_value=_session_sequence([None, existing])), \
+         patch("scribe.services.dedup.embeddings_svc.semantic_search_notes", sem):
+        dup = await find_duplicate_note(
+            7, "primaryButton — something else entirely", body="x" * 400,
+            project_id=2, is_task=False, note_type="snippet",
+            code=".btn-primary { color: red; }",
+            locations=[{"repo": "Scribe", "path": "a/b.css", "symbol": ".btn-primary"}],
+        )
+    assert dup is not None
+    assert dup.reason == "location"
+    assert dup.similarity == 1.0
+    # Structural identity is certain, so it must not be diluted by asking the
+    # embedder for a second opinion.
+    sem.assert_not_called()
+
+
+@pytest.mark.asyncio
+async def test_identical_code_is_a_duplicate_at_a_different_location():
+    existing = _fake_note(id=31, title="group_pairs", note_type="snippet")
+    with patch("scribe.services.dedup.async_session",
+               return_value=_session_sequence([None, None, existing])), \
+         patch("scribe.services.dedup.embeddings_svc.semantic_search_notes",
+               AsyncMock(return_value=[])):
+        dup = await find_duplicate_note(
+            7, "unionFind", body="x" * 400, project_id=2, is_task=False,
+            note_type="snippet", code="def f():\n    return 1",
+            locations=[{"repo": "Scribe", "path": "z.py", "symbol": "f"}],
+        )
+    assert dup is not None
+    assert dup.reason == "code"
+
+
+@pytest.mark.asyncio
+async def test_a_location_without_a_symbol_is_not_an_identity():
+    """A path alone is a DIRECTORY of artefacts. Matching on it would refuse
+    every second snippet recorded from one file — which is exactly the corpus
+    the button recipes form."""
+    session = _session_sequence([None])
+    sem = AsyncMock(return_value=[])
+    with patch("scribe.services.dedup.async_session", return_value=session), \
+         patch("scribe.services.dedup.embeddings_svc.semantic_search_notes", sem):
+        dup = await find_duplicate_note(
+            7, "Some recipe", body="x" * 400, project_id=2, is_task=False,
+            note_type="snippet", code="",
+            locations=[{"repo": "Scribe", "path": "a/b.css", "symbol": ""}],
+        )
+    assert dup is None
+    # Exactly one query — the title check. With no symbol and no code there is
+    # nothing to match structurally, and the sequence above would raise
+    # StopIteration if a second query were issued.
+    assert session.execute.await_count == 1
+
+
+@pytest.mark.asyncio
+async def test_snippets_use_the_raised_semantic_threshold():
+    """Variants of one component legitimately reach 0.92. The semantic arm has
+    to sit above that band or it refuses the corpus it exists to protect."""
+    from scribe.services.dedup import (
+        _SEMANTIC_THRESHOLD,
+        _SNIPPET_SEMANTIC_THRESHOLD,
+    )
+    sem = AsyncMock(return_value=[])
+    with patch("scribe.services.dedup.async_session",
+               return_value=_session_sequence([None, None, None])), \
+         patch("scribe.services.dedup.embeddings_svc.semantic_search_notes", sem):
+        await find_duplicate_note(
+            7, "A recipe", body="x" * 400, project_id=2, is_task=False,
+            note_type="snippet", code="x",
+            locations=[{"repo": "R", "path": "p", "symbol": "s"}],
+        )
+    assert sem.await_args.kwargs["threshold"] == _SNIPPET_SEMANTIC_THRESHOLD
+    assert _SNIPPET_SEMANTIC_THRESHOLD > 0.92, (
+        "the observed sibling band tops out at 0.92 (.btn-danger vs "
+        ".btn-danger-outline); a threshold at or below it blocks legitimate "
+        "variants again"
+    )
+    assert _SNIPPET_SEMANTIC_THRESHOLD > _SEMANTIC_THRESHOLD
+
+
+def test_sibling_variants_are_not_reported_as_merge_candidates():
+    """The measured false POSITIVE: eight button recipes, every direct pair over
+    the floor, proposed as ONE merge set."""
+    from scribe.services.dedup import _drop_sibling_pairs
+
+    records = {
+        1: {"locations": [{"repo": "S", "path": "c.css", "symbol": ".btn-primary"}],
+            "code_sha": "aaa"},
+        2: {"locations": [{"repo": "S", "path": "c.css", "symbol": ".btn-secondary"}],
+            "code_sha": "bbb"},
+    }
+    assert _drop_sibling_pairs([(1, 2, 0.87)], records) == []
+
+
+def test_identical_code_still_reports_even_with_different_symbols():
+    """The filter keys on "the author named these apart", but a shared code
+    fingerprint overrides that — the same code under two names IS the
+    copy-paste the report exists to surface."""
+    from scribe.services.dedup import _drop_sibling_pairs
+
+    records = {
+        1: {"locations": [{"repo": "S", "path": "a.py", "symbol": "debounce"}],
+            "code_sha": "same"},
+        2: {"locations": [{"repo": "S", "path": "b.py", "symbol": "useDebounced"}],
+            "code_sha": "same"},
+    }
+    assert _drop_sibling_pairs([(1, 2, 0.9)], records) == [(1, 2, 0.9)]
+
+
+def test_unnamed_snippets_still_report():
+    """A snippet with no recorded symbol made no identity claim, so the filter
+    must not protect it — re-recording without a location is a common way to
+    duplicate."""
+    from scribe.services.dedup import _drop_sibling_pairs
+
+    records = {1: {"code_sha": "aaa"}, 2: {"code_sha": "bbb"}}
+    assert _drop_sibling_pairs([(1, 2, 0.9)], records) == [(1, 2, 0.9)]
+
+
+def test_duplicate_response_names_what_matched_for_structural_hits():
+    """A structural hit is certain, so the message must not hedge with
+    "similar" — and it points at merge, which is what two records of one
+    artefact actually need."""
+    r = duplicate_response(
+        DuplicateMatch(id=9, title=".btn-primary", similarity=1.0, reason="location"),
+        "snippet",
+    )
+    assert "repo · path · symbol" in r["message"]
+    assert "merge_snippets" in r["message"]
+    assert "similar" not in r["message"]
+
+    r = duplicate_response(
+        DuplicateMatch(id=9, title="x", similarity=1.0, reason="code"), "snippet",
+    )
+    assert "identical code" in r["message"]