phase: 122_image_documents

**Phase 122 (image documents) — final verification pass: all green. No code changes were needed; defects found: none.**

**Verified (implementation already complete in working tree, reviewed end-to-end):**
- Toggle (`BOR_IMAGES`/`BOR_IMAGE_EXTENSIONS`/`BOR_IMAGE_DIR`, off by default) + `GET /api/config` `images` flag
- Ingest: bytes digest, `image_dir` persistent copy, `content = summary = vision description` (chat-model call; only text embedded), fail-soft skip + `images_failed` counter
- Serve/display: `/api/documents/{id}/image` route (404 matrix), viewer `<img>` + description, Sources 48px lazy thumbnails, chat inline source figure (alt = summary), agent `read` marker
- Prune guard: images-off syncs never prune `is_image` docs

**Test / lint / coverage (exact commands & outcomes):**
- `uv run pytest` → exit 0 (green; note: pytest 9.1.1 `-q` omits the final count line in output — exit code authoritative)
- `uv run pytest --cov=app --cov-report=term-missing` → **2715 passed, exit 0, TOTAL 99%** (>90% gate)
- `uv run ruff check . && uv run pyright` → "All checks passed!" / "0 errors, 0 warnings, 0 informations"
- `uv run pytest tests/e2e/test_image_documents.py -v --no-cov` → **4 passed, exit 0** (isolation)

**Completion criteria:** (1) images=true → described/embedded/displayed docs: ✅ (E2E + integration) · (2) images=false byte-identical + image docs survive sync: ✅ (E2E negative app + unit/integration) · (3) viewer + chat rendering with alt text; failed description skips + logs, sync completes: ✅ · (4) test/lint/coverage gates: ✅ · (5) commit + phase move: deferred to harness per this pass's rules (working tree left uncommitted).

**Notable deviation (pre-existing, documented in code):** image route uses `require_user` (phase-79 posture, same gate as the document content endpoint) rather than the phase text's "public" parenthetical — matches the endpoint it mirrors.

**Next pending phase:** `123_chat_image_questions`.

frontend/assets/sources.js

@@ -285,6 +285,21 @@
  *   • the stat cards are UNTOUCHED — they keep their indexed_at
  *     "last indexed" semantics (the owner asked for the column, not
  *     the cards).
+ *
+ * Phase 122 (task 04) — the image-doc thumbnail: a file node of the
+ * tree carries the image affordance (is_image / image_url / summary —
+ * OMITTED on text nodes, the wire-additive rule) when it is an image
+ * document. makeRow's Path cell then renders a FIXED 48px thumbnail
+ * box (object-fit: cover, loading="lazy", alt = the summary — the
+ * vision description; a NULL summary falls back to the title) BEFORE
+ * the path link (the .kb-doc-path flex wrapper — the link keeps its
+ * ellipsis). Progressive enhancement: a failed fetch (or the lazy
+ * first paint) swaps in the document glyph INSIDE the same fixed box
+ * (no layout shift beyond the box, no broken-image placeholder). Text
+ * rows never get a box (the pre-phase bare-link cell, byte-identical).
+ * The glyph is static SVG (aria-hidden — the alt text is the
+ * accessible content); the box + img are properties only, never
+ * innerHTML with document-derived data (the house rule).
  */
 
 import { fetchIsAdmin } from "./header.js";
@@ -1391,12 +1406,78 @@ export async function mount(root) {
           chunks: f.chunks,
           created_at: f.created_at, // phase 106 (task 08, D8): the tree's file date
           indexed_at: f.indexed_at,
+          // Phase 122 (task 04): the image affordance — the tree's
+          // file node carries is_image / image_url / summary on an
+          // image doc (the omission rule: a TEXT node's wire shape
+          // carries none, so these stay undefined there and makeRow
+          // keeps the bare-link cell, byte-identical to pre-phase).
+          is_image: f.is_image,
+          image_url: f.image_url,
+          summary: f.summary,
         })
       );
     }
     if (tableWrap) tableWrap.hidden = files.length === 0;
   }
 
+  /* Phase 122 (task 04): the document glyph — the fallback INSIDE the
+   * fixed thumbnail box (a failed fetch, or a node with no servable
+   * image_url). Static SVG, aria-hidden (the img's alt is the
+   * accessible content; this is decoration for the box). Built with
+   * createElementNS — the module keeps its ONE innerHTML (the static
+   * sync-modal skeleton, the test_kb_tree_ui pin). */
+  function docThumbGlyph() {
+    const span = document.createElement("span");
+    span.className = "kb-doc-thumb-glyph";
+    span.setAttribute("aria-hidden", "true");
+    const NS = "http://www.w3.org/2000/svg";
+    const svg = document.createElementNS(NS, "svg");
+    svg.setAttribute("viewBox", "0 0 48 48");
+    svg.setAttribute("fill", "none");
+    svg.setAttribute("stroke", "currentColor");
+    svg.setAttribute("stroke-width", "2.4");
+    svg.setAttribute("stroke-linecap", "round");
+    svg.setAttribute("stroke-linejoin", "round");
+    const sheet = document.createElementNS(NS, "path");
+    sheet.setAttribute(
+      "d",
+      "M12 4h16l8 8v28a4 4 0 0 1-4 4H12a4 4 0 0 1-4-4V8a4 4 0 0 1 4-4Z"
+    );
+    const fold = document.createElementNS(NS, "path");
+    fold.setAttribute("d", "M28 4v8h8");
+    svg.append(sheet, fold);
+    span.appendChild(svg);
+    return span;
+  }
+
+  /* Phase 122 (task 04): the image-doc thumbnail — the FIXED 48px box
+   * (object-fit: cover via CSS, loading="lazy", alt = the summary —
+   * the vision description; a NULL/blank summary falls back to the
+   * title, then the path). A failed fetch swaps in the document
+   * glyph in the SAME box (progressive enhancement — no layout shift
+   * beyond the fixed box, no broken-image placeholder). Called only
+   * for image rows (makeRow gates on d.is_image). */
+  function docThumb(d) {
+    const box = document.createElement("span");
+    box.className = "kb-doc-thumb";
+    const alt =
+      typeof d.summary === "string" && d.summary.trim() !== ""
+        ? d.summary
+        : d.title || d.path;
+    if (d.image_url) {
+      const img = document.createElement("img");
+      img.className = "kb-doc-thumb-img";
+      img.loading = "lazy";
+      img.src = d.image_url;
+      img.alt = alt;
+      img.addEventListener("error", () => box.replaceChildren(docThumbGlyph()));
+      box.appendChild(img);
+    } else {
+      box.appendChild(docThumbGlyph());
+    }
+    return box;
+  }
+
   /* The no-data state (phase 97): zero sources (nothing registered,
    * nothing indexed) OR a failed tree fetch (the former showEmpty
    * failure behavior, unchanged in kind) — every catalog surface
@@ -1440,7 +1521,18 @@ export async function mount(root) {
     });
     link.title = d.path; // full path as the link's hover/accessible name
     link.textContent = d.path;
-    pathTd.appendChild(link);
+    // Phase 122 (task 04): an image row gets the FIXED 48px thumbnail
+    // box before the path link (the .kb-doc-path flex wrapper — the
+    // link keeps its ellipsis). Text rows keep the bare-link cell,
+    // byte-identical to pre-phase (no box at all).
+    if (d.is_image) {
+      const pathWrap = document.createElement("div");
+      pathWrap.className = "kb-doc-path";
+      pathWrap.append(docThumb(d), link);
+      pathTd.appendChild(pathWrap);
+    } else {
+      pathTd.appendChild(link);
+    }
     tr.appendChild(pathTd);
 
     // Phase 106 (task 08, D8): the cell order is [title, chunks,