phase: 181_svg_document_preview

**Phase 181 — final verification pass (all tasks already complete; verified + docs pass)**

- Verified: `app/rag/svg_text.py` (100 % cov), vector branch in `_index_image_file`, `_row_kind_mismatch` text→image migration, `IMAGE_MIMES[".svg"]`, sandboxed CSP on `GET /api/documents/{id}/image`, `.doc-image-img--vector` in `document.js`/`styles.css`, figure/thumbnail deliberate non-changes.
- Tests/lint (exact commands): `uv run pytest --cov=app --cov-report=term-missing` → **4265 passed, TOTAL 99 %** (exit 0) · `uv run pytest tests/e2e/test_svg_document_preview.py -v --no-cov` → **5 passed in isolation** · `uv run ruff check .` → clean · `uv run pyright` → **0 errors**.
- Regression (each run in isolation, `--no-cov`, all rc=0): `test_image_documents`, `test_chat_image_questions`, `test_answer_images`, `test_chat_answer_clusters`, `test_image_anchor_context`, `test_image_upload_feedback`, `test_markdown_inline_links_images`, `test_prose_word_wrap`, `test_pdf_support`, `test_pictorial_pdf`, `test_garbage_pdf`, `test_pdf_image_extraction`, `test_pdf_image_context`, `test_pdf_pages_in_sources`, `test_pdf_strip_additive_selfheal`, `test_sync_image_progress`.
- Completion criteria: ①SVG→`is_image`+`image_path`, no vision call, own `<title>/<desc>/<text>` — **met**; ②`image/svg+xml` + `default-src 'none'; sandbox` + `private, max-age=3600`, raster headers byte-unchanged — **met**; ③chat figure → modal `<img>`, no XML — **met**; ④`/document.html` full-width vector in `.doc-image` + text below — **met**; ⑤`![alt](/api/documents/<id>/image)` paints — **met**; ⑥raster/PDF unchanged — **met**; ⑦all gates green — **met**; ⑧commit + phase-dir move — harness-owned.
- Documentation: found and fixed README inconsistencies — stale forward reference "left to phase 181 / is phase 181's job" → completed-tense sizing note; "Updating the documents" standalone-image list missing `svg`; new **Raster only** bullet for question uploads (`.svg` → 422) documenting the `chat_images` guard; missing `svg_indexed=N` / `import: svg indexed` log contract; env-table heading `122/123/124` → `122/123/124/181`; new troubleshooting entry for an `.svg` showing raw XML. Full audit: every `Settings` field and every `.env.example` var is documented; pages/commands/scripts all exist. AGENTS.md verified accurate (phase-181 §5 clause present) — no changes needed beyond what the phase wrote.
- Notable deviation (kept from task 02): `app/api/chat_images.py` subtracts `_VECTOR_IMAGE_EXTENSIONS` from the question-image accept set — a required consequence of LOCKED A7 (`svg` in the default image set) since `_CHAT_IMAGE_FILENAME_RE` refuses to *serve* `.svg`; the regex itself is untouched, as the phase specified.
- Note for the commit: changes include `README.md`, `AGENTS.md` and `.env.example` — the phase file's `git add app/ frontend/ tests/ .env.example .agents/phases/` line omits the two markdown files; stage them too.
- Next pending phase: `182_verbatim_show_text`.

app/rag/importer.py

@@ -111,6 +111,20 @@ summary (stored verbatim, no ``lite`` call, no pointer line), so the
 ``is_summary`` position −1 chunk mirrors ``Document.summary``, which
 equals ``Document.content``.
 
+The image branch is RASTER (vision-described, the paragraph above) OR
+VECTOR (phase 181, LOCKED A1: an ``.svg``). A vector file takes the
+SAME branch — bytes digest, ``image_dir`` copy, ``is_image``/``image_path``,
+the ``summary = content`` convention, the phase-125 ``image_context``
+enrichment — but NEVER the model call: its searchable text is extracted
+from the file itself (:func:`app.rag.svg_text.extract_svg_text` — the
+``<title>``/``<desc>``/``<text>`` words, or LOCKED A2's structural line
+built from the stem, the shape census and the ``viewBox`` when the
+drawing carries no words at all). A file the extractor refuses (over the
+size cap, DOCTYPE/entity-bearing, malformed XML) fails soft exactly like
+an undescribed raster: ``images_failed`` + a warning, no row, no copy.
+Successful vector indexes count ``svg_indexed`` (log-only) and log one
+``import: svg indexed`` line.
+
 PDF files (phase 126, LOCKED A1/A2/A3/A4): a ``.pdf`` file (the
 ``pdf`` token of ``BOR_IMPORT_EXTENSIONS``) takes the PDF index path
 (:func:`_index_pdf_file` — the branch sits in :func:`_index_file`
@@ -359,6 +373,7 @@ from app.rag.summarizer import (
     describe_pdf_page,
     generate_summary,
 )
+from app.rag.svg_text import SvgText, extract_svg_text
 
 logger = logging.getLogger("app.importer")
 
@@ -433,6 +448,14 @@ class ImportSummary:
     #: Fail-soft: the sync continues, this counter + the warning line
     #: are the signal.
     images_failed: int = 0
+    #: Vector image docs (phase 181, task 02 — LOCKED A1) indexed from
+    #: their OWN extracted text (:func:`app.rag.svg_text.extract_svg_text`)
+    #: with NO vision call. A subset of the image branch: it does NOT
+    #: move ``added``/``updated`` (those count as for any other image).
+    #: Log-only (the sync ``detail`` API shape is untouched — the stats
+    #: log-only convention, phase 133): the owner reads it in the sync
+    #: log beside the per-file ``import: svg indexed`` line.
+    svg_indexed: int = 0
     #: PDFs (phase 133, task 03) whose text layer failed the garbage
     #: gate (:func:`app.rag.pdf.is_usable_pdf_text` — empty layer or
     #: XML/binary soup) and took the page-screenshot vision fallback
@@ -498,7 +521,7 @@ class ImportSummary:
         logger.info(
             "import: summary files=%d added=%d updated=%d unchanged=%d pruned=%d "
             "errors=%d chunks=%d embed_batches=%d summaries=%d summary_errors=%d "
-            "summary_backfilled=%d dates_updated=%d images_failed=%d "
+            "summary_backfilled=%d dates_updated=%d images_failed=%d svg_indexed=%d "
             "image_context_backfilled=%d pdfs_screenshotted=%d "
             "pdfs_pictorial=%d pdf_pictorial_pages=%d pdf_images_deduped=%d "
             "pdf_images_blank_skipped=%d formats=%s",
@@ -515,6 +538,7 @@ class ImportSummary:
             self.summary_backfilled,
             self.dates_updated,
             self.images_failed,
+            self.svg_indexed,
             self.image_context_backfilled,
             self.pdfs_screenshotted,
             self.pdfs_pictorial,
@@ -1325,6 +1349,38 @@ def _regate_pdf_strip(
         )
 
 
+def _row_kind_mismatch(path: Path, doc: Document, settings: Settings) -> bool:
+    """Phase 181 (task 02, design D4): does this row's KIND disagree with
+    how *path* would be indexed NOW — the ONE case that must fall
+    THROUGH the phase-147 unchanged fast path?
+
+    ``True`` only while the ``images`` toggle is ON and the file matches
+    the image extension set while the row is still a TEXT row
+    (``is_image`` False). That is exactly the migration this phase needs:
+    an ``.svg`` imported before ``svg`` joined
+    :py:attr:`Settings.image_extension_set` is a text document whose
+    ``content`` is the raw XML — and because the text digest of an ASCII
+    file equals the digest of its bytes, its ``file_hash`` (and even its
+    ``content_hash``) matches perfectly, so a hash-only fast path would
+    freeze it as XML forever: no bytes route, no preview, no
+    ``image_url`` citation figure — the exact complaint this phase
+    answers. Falling through runs the image branch, which rewrites the
+    row (``is_image``/``image_path``/extracted ``content`` + the
+    ``image_dir`` copy) through the normal index write: no alembic
+    migration, no backfill script, and the next sync is fast again.
+
+    The REVERSE direction is deliberately NOT forced: with the toggle
+    OFF the walk never admits an image file (so an ``is_image`` row never
+    reaches :func:`_index_file` at all) and the phase-122 prune guard
+    keeps the row; requiring ``settings.images`` here keeps that
+    contract byte-identical (``svg`` in ``BOR_IMPORT_EXTENSIONS`` with
+    the toggle off still means "text document", LOCKED A7).
+    """
+    if not settings.images or doc.is_image:
+        return False
+    return match_extension(path, settings.image_extension_set) is not None
+
+
 async def _index_file(
     session: Session,
     *,
@@ -1400,10 +1456,17 @@ async def _index_file(
         # fast path (and the branches' unchanged path) refresh the
         # stored date from the same source.
         raw_date = file_mtime_datetime(full_path)
-    if doc is not None and doc.file_hash == file_digest:
+    if (
+        doc is not None
+        and doc.file_hash == file_digest
+        and not _row_kind_mismatch(full_path, doc, settings)
+    ):
         # The fast path: the raw bytes are what was indexed last time
         # — the bookkeeping (backfill / D1 / D4) runs in the shared
-        # helper, nothing else does.
+        # helper, nothing else does. Phase 181 (task 02, D4): "the same
+        # bytes" is only "the same document" when the row's KIND also
+        # matches how the file would be indexed NOW — see
+        # :func:`_row_kind_mismatch` (the SVG text→image migration).
         await _unchanged_doc(
             session, doc, source=source, rel=rel, llm=llm, summary=summary,
             raw_date=raw_date, file_digest=file_digest, full_path=full_path,
@@ -3542,7 +3605,17 @@ async def _index_image_file(
     on_chunk: Callable[[int, int], None] | None = None,
 ) -> None:
     """The phase-122 image branch of :func:`_index_file` — a standalone
-    image is indexed from its BYTES, never its text:
+    image is indexed from its BYTES, never its text.
+
+    Phase 181 (task 02, LOCKED A1) makes the branch RASTER **or**
+    VECTOR: an ``.svg`` takes this same path (digest, copy, ``is_image``,
+    ``image_path``, chunking, ``summary = content``, the phase-125
+    ``image_context`` enrichment) but its ``content`` comes from
+    :func:`app.rag.svg_text.extract_svg_text` instead of the vision
+    seam, and a success counts the log-only ``svg_indexed``. The bullets
+    and the fail-soft below are shared by both kinds — the only
+    difference is where the text comes from.
+
 
     * the sha256 digest is over the raw bytes (the digest rule is
       content identity — the same bytes are the same document);
@@ -3600,13 +3673,20 @@ async def _index_image_file(
     digest = hashlib.sha256(data).hexdigest()
     doc = session.scalar(select(Document).where(Document.source == source, Document.path == rel))
 
-    if doc is not None and doc.content_hash == digest:
+    if doc is not None and doc.is_image and doc.content_hash == digest:
         # Phase 147: the shared unchanged path — a pre-phase NULL-hash
         # row, or a bytes-changed/content-same image (the byte digest
         # still matches). The helper stamps the new file hash (the
         # next sync takes the fast path); for an image the summary is
         # the stored description (``doc.content``), so the image-aware
         # ``_store_summary`` backfill re-stores it verbatim.
+        # Phase 181 (task 02, D4): ``doc.is_image`` joins the guard — a
+        # NON-image row routed here by :func:`_row_kind_mismatch` is the
+        # migration case, not an unchanged one. An ASCII SVG indexed as
+        # TEXT digests to the SAME value here (the text path hashes
+        # ``content.encode()``, which for a byte-clean file equals the
+        # raw-bytes digest), so without it the text→image conversion
+        # would report ``unchanged`` forever and never produce the copy.
         await _unchanged_doc(
             session, doc, source=source, rel=rel, llm=llm, summary=summary,
             raw_date=raw_date, file_digest=file_digest, full_path=full_path,
@@ -3629,16 +3709,50 @@ async def _index_image_file(
     # it is generated BEFORE anything is written, so a failure skips the
     # doc with no row and no copy (the copy is only made after a
     # successful description — a failure never leaves an orphan).
-    content = await _describe_or_skip(
-        llm, data=data, source=source, rel=rel, full_path=full_path,
-        context=image_context,
-    )
+    #
+    # Phase 181 (task 02, LOCKED A1): the VECTOR branch. An ``.svg`` is
+    # described by NOBODY — OpenAI-compatible vision endpoints reject
+    # ``image/svg+xml`` and no rasteriser dependency is in scope — so
+    # its text comes out of the file itself (its ``<title>``/``<desc>``/
+    # ``<text>`` words, or LOCKED A2's structural line). Everything else
+    # in this function is shared: the byte digest, the ``image_dir``
+    # copy, ``is_image``/``image_path``, the title, the counters, the
+    # phase-125 ``image_context`` prepend below, the chunk pipeline and
+    # ``summary = content``. The seam below is not reached, so no vision
+    # call happens for a vector file (pinned by the unit tests).
+    is_vector = full_path.suffix.lower() == ".svg"
+    svg: SvgText | None = None
+    if is_vector:
+        svg = extract_svg_text(data, stem=full_path.stem)
+        content = None if svg is None else svg.text
+    else:
+        content = await _describe_or_skip(
+            llm, data=data, source=source, rel=rel, full_path=full_path,
+            context=image_context,
+        )
     if content is None:
         # LOCKED A3 fail-soft: an undescribed image is unsearchable
-        # noise — skip the doc entirely (no row, no copy).
+        # noise — skip the doc entirely (no row, no copy). Phase 181
+        # (LOCKED A2): the vector case skips ONLY when the extractor
+        # refused the file (over the size cap, DOCTYPE/entity-bearing,
+        # malformed XML) — a textless SVG is NOT a failure, it gets the
+        # structural line.
         summary.images_failed += 1
-        logger.warning("import: image description failed source=%s path=%s", source, rel)
+        logger.warning(
+            "import: %s source=%s path=%s",
+            "svg text extraction failed" if is_vector else "image description failed",
+            source, rel,
+        )
         return
+    if svg is not None:
+        # Phase 181 (task 02): the log-only vector counter + the
+        # auditability line (AGENTS rule 10) — ``structural=True`` marks
+        # the docs whose text is the LOCKED A2 fallback line.
+        summary.svg_indexed += 1
+        logger.info(
+            "import: svg indexed source=%s path=%s structural=%s chars=%d",
+            source, rel, svg.structural, len(svg.text),
+        )
     if image_context is not None:
         # Phase 125 (task 03): the enriched content — the reference
         # context FIRST (for retrieval), then the description. The

app/rag/summarizer.py

@@ -149,6 +149,17 @@ PICTORIAL_PROMPT = f"{PICTORIAL_PAGE_MODE}: {PICTORIAL_INSTRUCTION}"
 #: takes the :data:`IMAGE_FALLBACK_MIME` data-URL mime in the describe
 #: call — the vision endpoint may reject it, and the fail-soft skip
 #: (``images_failed``) is the honest outcome.
+#:
+#: Phase 181 adds ``.svg`` — the ONE **vector** entry in the map. It
+#: exists for the BYTES route only: the vector import branch
+#: (``app/rag/importer.py::_index_image_file``) takes
+#: :func:`app.rag.svg_text.extract_svg_text` INSTEAD of the vision
+#: describe call (LOCKED A1), so an ``.svg`` never reaches
+#: :func:`image_data_url` and this value is never put in a multimodal
+#: message. ``app/api/docs.py::get_document_image`` reads the same map
+#: for the ``Content-Type`` (one map, one truth), and that route is
+#: where the vector value earns its place — plus the sandboxed CSP the
+#: vector bytes need and the rasters do not (LOCKED A3, phase 181).
 IMAGE_MIMES: dict[str, str] = {
     ".png": "image/png",
     ".jpg": "image/jpeg",
@@ -156,6 +167,7 @@ IMAGE_MIMES: dict[str, str] = {
     ".webp": "image/webp",
     ".gif": "image/gif",
     ".bmp": "image/bmp",
+    ".svg": "image/svg+xml",
 }
 
 #: The data-URL mime for an image extension :data:`IMAGE_MIMES` does not

app/rag/svg_text.py

@@ -0,0 +1,293 @@
+"""SVG text extraction — the words a vector drawing carries (phase 181).
+
+Pure functions, no I/O — fully unit-testable. Stdlib only (the
+:mod:`app.rag.md_images` precedent, phase 125).
+
+An ``.svg`` joins the image family (LOCKED A1, phase 181): its BYTES are
+served to the browser so every citation surface paints the graphic
+instead of XML. But OpenAI-compatible vision endpoints reject
+``image/svg+xml``, and adding a rasteriser dependency is out of scope —
+so the vector branch never calls the describer. The text that makes the
+document **retrievable** comes from the file itself:
+
+* ``<title>``, ``<desc>`` and ``<text>`` (LOCKED D2) — collected in
+  DOCUMENT order by LOCAL name (namespace-agnostic: ``<title>`` and
+  ``{http://www.w3.org/2000/svg}title`` both count, declared ``svg:``
+  prefixes included), whitespace-normalised, de-duplicated
+  case-insensitively keeping the FIRST occurrence, joined with ``\\n``.
+  ``<tspan>`` children are joined WITH a space so ``a<tspan>b</tspan>``
+  reads "a b", not "ab". XML entity references inside the text
+  (``&amp;``) are decoded by the parser — the correct direction, the
+  renderer re-escapes on display.
+* a textless diagram (pure ``<path>``s — extremely common) still gets
+  honest, searchable text (LOCKED A2): one structural line built ONLY
+  from facts the file states, never invented prose.
+
+Guards, applied BEFORE any parse (untrusted markup, the sibling of
+LOCKED A3):
+
+* empty / whitespace-only input → ``None``;
+* more than :data:`MAX_SVG_BYTES` → ``None`` (memory guard);
+* a ``<!DOCTYPE`` or ``<!ENTITY`` declaration anywhere in the bytes →
+  ``None``. Refusing the doctype outright is what makes stdlib
+  :mod:`xml.etree.ElementTree` safe here: no external entities, no
+  entity expansion (the billion-laughs class);
+* malformed XML (:class:`xml.etree.ElementTree.ParseError`) → ``None``
+  — never re-raised, the caller's fail-soft is a skip, not a crash.
+
+What is deliberately NOT followed: ``<image>`` elements embedding a
+raster inside the SVG (their ``href`` is not text), and
+``aria-label``/``role`` attributes — ``<title>``/``<desc>`` are the
+SVG-spec carriers of words and the fallback line covers the rest.
+"""
+from __future__ import annotations
+
+import math
+import re
+from dataclasses import dataclass
+from xml.etree import ElementTree
+
+#: Hard input cap for one SVG (phase 181, LOCKED A3's sibling) — bytes
+#: over this are refused without a parse attempt, so a hostile or
+#: accidentally gigantic file can never be the memory event of a sync.
+MAX_SVG_BYTES: int = 2 * 1024 * 1024
+
+#: Cap on the EXTRACTED text (phase 181). It binds on the result, never
+#: silently mid-word: an over-cap extraction is cut at the last newline
+#: or period before the cap (a hard cut only when the window holds no
+#: boundary at all).
+MAX_SVG_TEXT_CHARS: int = 4000
+
+#: A document type declaration in the raw bytes (lower-cased marker).
+#: Its presence — anywhere — refuses the input (billion-laughs /
+#: external-entity class).
+_DOCTYPE_MARKER = b"<!doctype"
+
+#: An entity declaration in the raw bytes (lower-cased marker) — same
+#: refusal as :data:`_DOCTYPE_MARKER`, checked separately so a stray
+#: ``<!ENTITY`` inside a stray doctype-less prolog is still caught.
+_ENTITY_MARKER = b"<!entity"
+
+#: Elements whose whole text block is one item, nested markup
+#: concatenated (:meth:`ElementTree.Element.itertext`).
+_BLOCK_TEXT_NAMES = frozenset({"title", "desc"})
+
+#: Elements whose text is joined with a space so inline children
+#: (``<tspan>``) do not weld their neighbours together.
+_SPACED_TEXT_NAMES = frozenset({"text"})
+
+#: Local names that are structure, not drawing: never counted as shapes
+#: in the fallback line (:func:`_shape_clause`).
+_NON_SHAPE_NAMES = frozenset({"svg", "title", "desc"})
+
+#: How many element kinds the fallback line names (LOCKED D3: "the
+#: three most common element local names with counts").
+_TOP_SHAPE_NAMES = 3
+
+#: ``viewBox`` components: four numbers separated by whitespace and/or
+#: commas (the SVG-spec grammar, which allows either).
+_VIEWBOX_SPLIT_RE = re.compile(r"[\s,]+")
+
+#: The multiplication sign used between a shape name and its count, and
+#: between the viewBox width and height — the app's own typography.
+_TIMES = "×"
+
+
+@dataclass(frozen=True)
+class SvgText:
+    """The searchable text of one SVG document (phase 181, LOCKED A1/A2).
+
+    * ``text`` — what gets stored as the document's ``content`` (and
+      ``summary``, per the phase-122 image convention);
+    * ``structural`` — ``True`` when the document carried no words and
+      ``text`` is the structural fallback line, so the importer can log
+      and count it separately from a genuinely worded diagram.
+    """
+
+    text: str
+    structural: bool
+
+
+def local_name(tag: object) -> str:
+    """The namespace-agnostic name of an element tag.
+
+    ``{http://www.w3.org/2000/svg}title`` and ``title`` both give
+    ``"title"`` — ElementTree expands every declared prefix (including
+    ``<svg:title>``) into Clark notation, so stripping the ``{uri}`` is
+    all "namespace-agnostic" needs. A non-string tag (comment /
+    processing-instruction marker) has no name → ``""``.
+    """
+    if not isinstance(tag, str):
+        return ""
+    return tag.rsplit("}", 1)[-1]
+
+
+def extract_svg_text(data: bytes, *, stem: str = "") -> SvgText | None:
+    """Turn raw SVG bytes into the document's searchable text.
+
+    Returns ``None`` when the input is unusable or unsafe: empty /
+    whitespace-only, larger than :data:`MAX_SVG_BYTES`, carrying a
+    ``<!DOCTYPE``/``<!ENTITY`` declaration, or not well-formed XML. The
+    caller's fail-soft (skip the document, count it) is the honest
+    outcome — this function never raises for bad input.
+
+    *stem* is the file name without extension: it names the document in
+    the structural fallback line and is never invented.
+
+    Otherwise a :class:`SvgText` whose ``text`` is the document-order
+    ``<title>``/``<desc>``/``<text>`` words (``structural=False``), or —
+    when the file carries no words at all — the structural line built
+    from the stem, the shape census and the ``viewBox``
+    (``structural=True``, LOCKED A2).
+    """
+    if not data or not data.strip():
+        return None
+    if len(data) > MAX_SVG_BYTES:
+        return None
+    lowered = data.lower()
+    if _DOCTYPE_MARKER in lowered or _ENTITY_MARKER in lowered:
+        return None
+    try:
+        root = ElementTree.fromstring(data)
+    except ElementTree.ParseError:
+        return None
+    items = _dedupe(_walk_text(root))
+    if items:
+        return SvgText(text=_cap_text("\n".join(items)), structural=False)
+    return SvgText(text=_structural_line(root, stem), structural=True)
+
+
+def _walk_text(root: ElementTree.Element) -> list[str]:
+    """Every worded ``title``/``desc``/``text`` block, in document order.
+
+    Items are whitespace-normalised; a block that normalises to nothing
+    (an empty ``<title></title>``) is dropped so the fallback can still
+    describe the file.
+    """
+    items: list[str] = []
+    for el in root.iter():
+        name = local_name(el.tag)
+        if name in _BLOCK_TEXT_NAMES:
+            raw = "".join(el.itertext())
+        elif name in _SPACED_TEXT_NAMES:
+            raw = " ".join(el.itertext())
+        else:
+            continue
+        normalised = " ".join(raw.split())
+        if normalised:
+            items.append(normalised)
+    return items
+
+
+def _dedupe(items: list[str]) -> list[str]:
+    """Drop repeats case-insensitively, keeping the FIRST occurrence.
+
+    A ``<title>`` mirrored in a ``<desc>`` (exporters do this) is one
+    sentence in the index, not two; the first position in document
+    order is the one kept.
+    """
+    seen: set[str] = set()
+    unique: list[str] = []
+    for item in items:
+        key = item.casefold()
+        if key in seen:
+            continue
+        seen.add(key)
+        unique.append(item)
+    return unique
+
+
+def _cap_text(text: str) -> str:
+    """Cap *text* at :data:`MAX_SVG_TEXT_CHARS` without cutting a word.
+
+    An over-cap text is cut at the LAST newline or period before the cap
+    (whichever comes later) so the stored text ends on a boundary; only
+    a window with no boundary at all (one colossal run of characters)
+    is hard-cut.
+    """
+    if len(text) <= MAX_SVG_TEXT_CHARS:
+        return text
+    window = text[:MAX_SVG_TEXT_CHARS]
+    cut = max(window.rfind("\n"), window.rfind("."))
+    if cut < 0:
+        return window
+    return text[: cut + 1].rstrip()
+
+
+def _structural_line(root: ElementTree.Element, stem: str) -> str:
+    """The LOCKED A2 fallback: one line of facts, nothing invented.
+
+    ``Vector diagram "<stem>" — <N> shapes (<top-3 kinds>), viewBox
+    <w>×<h>`` — each fact clause is omitted when the file does not
+    state it, and the stem clause disappears entirely when empty (no
+    empty quotes). With no facts and no stem the line is just
+    ``Vector diagram``.
+    """
+    head = f'Vector diagram "{stem}"' if stem else "Vector diagram"
+    facts = [c for c in (_shape_clause(root), _viewbox_clause(root)) if c]
+    if not facts:
+        return head
+    return f"{head} — {', '.join(facts)}"
+
+
+def _shape_clause(root: ElementTree.Element) -> str:
+    """``<N> shapes (<kinds>)`` — the drawing's element census.
+
+    *N* counts every descendant element except ``svg``, ``title`` and
+    ``desc`` (structure, not drawing). The kinds are the
+    :data:`_TOP_SHAPE_NAMES` most common local names, ordered by count
+    (document order breaks ties) and annotated with their count — the
+    count is left off a kind that appears exactly once, which is what
+    the total already says. ``""`` when there are no shapes at all, so
+    the clause is omitted rather than claiming "0 shapes".
+    """
+    counts: dict[str, int] = {}
+    first_seen: dict[str, int] = {}
+    total = 0
+    for index, el in enumerate(root.iter()):
+        if el is root:
+            continue
+        name = local_name(el.tag)
+        if not name or name in _NON_SHAPE_NAMES:
+            continue
+        counts[name] = counts.get(name, 0) + 1
+        first_seen.setdefault(name, index)
+        total += 1
+    if not total:
+        return ""
+    top = sorted(counts, key=lambda name: (-counts[name], first_seen[name]))
+    listing = ", ".join(
+        f"{name}{_TIMES}{counts[name]}" if counts[name] > 1 else name
+        for name in top[:_TOP_SHAPE_NAMES]
+    )
+    noun = "shape" if total == 1 else "shapes"
+    return f"{total} {noun} ({listing})"
+
+
+def _viewbox_clause(root: ElementTree.Element) -> str:
+    """``viewBox <w>×<h>`` from the root's ``viewBox``, or ``""``.
+
+    The spec grammar is four whitespace-and/or-comma separated numbers;
+    the last two are the width and height. Unparseable (wrong count,
+    non-numeric, non-finite) → ``""`` — the clause is omitted rather
+    than reporting a size the file does not state. Integral values
+    print without a trailing ``.0``.
+    """
+    raw = (root.get("viewBox") or "").strip()
+    if not raw:
+        return ""
+    parts = [part for part in _VIEWBOX_SPLIT_RE.split(raw) if part]
+    if len(parts) != 4:
+        return ""
+    try:
+        _min_x, _min_y, width, height = (float(part) for part in parts)
+    except ValueError:
+        return ""
+    if not (math.isfinite(width) and math.isfinite(height)):
+        return ""
+    return f"viewBox {_format_number(width)}{_TIMES}{_format_number(height)}"
+
+
+def _format_number(value: float) -> str:
+    """``8`` for 8.0, ``8.5`` for 8.5 — no trailing ``.0`` in a size."""
+    return str(int(value)) if value.is_integer() else str(value)