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/api/docs.py

@@ -52,10 +52,15 @@ BYTES route: the persistent copy behind an ``is_image`` document's
 ``image_path``, served with the extension's ``Content-Type`` (the
 ``app.rag.summarizer.IMAGE_MIMES`` map — one map, one truth) and a
 ``Cache-Control: private, max-age=3600`` header (the bytes are
-content-hashed — long enough, bustable by re-upload). PUBLIC (phase
-124 — the phase-123 chat-image precedent: the image is part of a
-shared chat's rendered content, and the shared chat — the app's ONLY
-anonymous surface — must render the answer figure faithfully for
+content-hashed — long enough, bustable by re-upload), plus — for the
+vector ``image/svg+xml`` entry only, phase 181 LOCKED A3 — a
+``Content-Security-Policy: default-src 'none'; sandbox`` so a DIRECT
+navigation to the URL cannot run script from stored SVG markup (the
+``SecurityHeadersMiddleware`` preserves that inner CSP; raster
+responses gain nothing). PUBLIC (phase 124 — the phase-123 chat-image
+precedent: the image is part of a shared chat's rendered content, and
+the shared chat — the app's ONLY anonymous surface — must render the
+answer figure faithfully for
 guests; the unguessable ``uuid4`` document id IS the credential, no
 enumeration value): a missing doc, a non-image doc, a doc whose
 ``image_path`` is NULL, or a row whose copy was lost all map to 404
@@ -132,6 +137,23 @@ from app.schemas import (
 
 router = APIRouter(tags=["kb"])
 
+#: The vector media type (phase 181, task 03) — read out of
+#: :data:`app.rag.summarizer.IMAGE_MIMES` rather than restated, so the
+#: guard below can never drift from the ``Content-Type`` the route
+#: sends for an ``.svg`` (one map, one truth).
+SVG_MEDIA_TYPE = IMAGE_MIMES[".svg"]
+
+#: The CSP an SVG bytes response carries (phase 181, task 03, LOCKED
+#: A3). ``sandbox`` — no scripting, and the document gets an OPAQUE
+#: origin (no same-origin fetch/cookie/form capability);
+#: ``default-src 'none'`` — no subresource of any kind. Scoped to the
+#: vector type ON PURPOSE: an ``<img>`` never runs SVG script, but this
+#: URL is directly navigable, and the bytes come from an untrusted
+#: source tree, so a direct visit must not become a script-capable
+#: same-origin document. Raster types are untouched (their header set
+#: stays byte-identical). See :func:`get_document_image`.
+SVG_SANDBOX_CSP = "default-src 'none'; sandbox"
+
 
 def doc_format(path: str, extensions: frozenset[str] = frozenset()) -> str:
     """Lowercased path suffix without its dot (``kubernetes.md`` → ``md``,
@@ -353,6 +375,33 @@ def get_document_image(
     ``application/octet-stream``) and ``Cache-Control: private,
     max-age=3600`` (the bytes are content-hashed — long enough to be
     useful, bustable by re-upload).
+
+    Phase 181 (task 03, LOCKED A3): an ``image/svg+xml`` response — the
+    vector entry of that same map, derived from the ROW's extension and
+    NEVER from a client value — carries ONE extra header,
+    :data:`SVG_SANDBOX_CSP` (``default-src 'none'; sandbox``). An
+    ``<img>`` can never execute an SVG's script, which is why the
+    figure surfaces are safe as they stand; but this URL is also
+    DIRECTLY NAVIGABLE (a guest who pastes it into the address bar),
+    and without the policy a stored SVG would render as a
+    script-capable SAME-ORIGIN document — the ingestion path takes
+    untrusted files from a source tree, so that is a stored-XSS seam
+    scoped to the app's origin. ``sandbox`` blocks scripting AND makes
+    the response an opaque origin (no same-origin fetches, cookies or
+    form submission from the document); ``default-src 'none'`` blocks
+    every subresource load, so the SVG cannot pull a tracker or a
+    remote image either. Deliberately NOT applied to the raster types:
+    their header set stays byte-identical (a PNG needs no policy
+    change, and adding one would risk the phase-123/124 image
+    surfaces), and no ``Content-Disposition: attachment`` is set — the
+    graphic must render inline, and ``sandbox`` is the stronger, less
+    intrusive control. The route sets the value on the response
+    itself; :class:`app.core.security_headers.SecurityHeadersMiddleware`
+    PRESERVES a CSP an inner layer already set, so this is the policy
+    the browser sees (the app-wide ``CSP`` string would be wrong here —
+    ``default-src 'self'`` would grant the SVG document the app's own
+    origins), while the middleware's global
+    ``X-Content-Type-Options: nosniff`` still applies.
     """
     try:
         uid = uuid.UUID(doc_id)
@@ -368,10 +417,15 @@ def get_document_image(
         # onerror fallback renders the "image unavailable" note.
         raise HTTPException(status_code=404, detail="document not found")
     media_type = IMAGE_MIMES.get(image_file.suffix.lower(), IMAGE_FALLBACK_MIME)
+    headers = {"Cache-Control": "private, max-age=3600"}
+    if media_type == SVG_MEDIA_TYPE:
+        # Phase 181 (LOCKED A3): vector bytes only — see the route
+        # docstring. Raster responses keep the header set they had.
+        headers["Content-Security-Policy"] = SVG_SANDBOX_CSP
     return FileResponse(
         image_file,
         media_type=media_type,
-        headers={"Cache-Control": "private, max-age=3600"},
+        headers=headers,
     )