phase: 138_markdown_blockquotes

**Phase 138 final verification pass — all green, no defects found.**

- Verified: blockquote pass in `frontend/assets/markdown.js` (step 2b, between escape+inline and paragraphs), guard extended to `|blockquote`, docstring updated; `.md-quote` CSS (left border + padding + `--ink-soft`, no fill, palette vars only, contrast comments, user-bubble override); unit pins + node behavior; dedicated E2E (chat / viewer / restore); mock `QUOTE_TRIGGER`/`QUOTE_ANSWER`; fixture `tests/fixtures/quote_docs/`. Thinking block confirmed on the same shared renderer (app.js L2025/L3095).
- `uv run pytest tests/e2e/test_markdown_blockquotes.py -v --no-cov` → 3 passed (isolation)
- `uv run pytest --cov=app --cov-report=term-missing` → 3268 passed, 9 skipped; TOTAL **99%** (>90%)
- `uv run ruff check . && uv run pyright` → All checks passed; 0 errors
- Criteria: quotes render in chat/viewer/restore ✅ (E2E) + thinking ✅ (shared renderer + unscoped AA CSS); `>>` collapses, fence/table `>` untouched ✅ (unit+e2e); non-quote byte-identical ✅ (exact fixture; phase-44/renderer suites pass **unedited**, confirmed by empty `git diff --stat`)
- No deviations; commit + phase-dir move left to the harness per pipeline rules (working tree clean of stray changes — only phase-138 diffs present)
- Next pending phase: **139_read_range_tool_lines**

frontend/assets/markdown.js

@@ -16,6 +16,22 @@
  * and restores it alongside the code blocks in the final step. Fences
  * win over tables (they are protected first), and everything that is
  * not a pipe table renders byte-identically to the original app.js copy.
+ *
+ * Phase 138 (2026-09-30, TODO.md L3) added the blockquote pass between
+ * step 2 (escape+inline) and step 3 (paragraphs): the maximal run of
+ * consecutive >-prefixed lines becomes ONE
+ * <blockquote class="md-quote"> with the members joined with <br>.
+ * The pass order is now fences → tables → escape+inline → blockquotes
+ * → paragraphs → restore. Group rule: a BLANK line terminates the
+ * group (a re-quoted line starts a new <blockquote>), and nested
+ * >> / >>> collapses to a single level (locked A1). Documented limit:
+ * a markdown STRUCTURE line inside a quote (a "- list" / "# heading")
+ * renders as plain text — the inline chain ran first, so its
+ * line-start transforms never see the post-strip text; inline
+ * code/strong/em still work. Fences and tables keep their precedence:
+ * a > inside a code fence never reaches the pass (step 1 placeholder),
+ * and a > in a table cell is restored in step 4. Everything without a
+ * quote line renders byte-identically to the pre-phase renderer.
  */
 
 function escapeHtml(s) {
@@ -123,13 +139,46 @@ function renderMarkdown(md) {
   // 2. Escape everything else, then apply the inline + block transforms.
   text = inline(escapeHtml(text));
 
+  // 2b. Blockquotes (phase 138, 2026-09-30, TODO.md L3). Runs AFTER
+  // the escape+inline step — a quote line now starts with the escaped
+  // marker &gt;, and inline code/strong/em already work inside quotes
+  // for free (this pass never re-transforms) — and BEFORE the
+  // paragraph pass, which the extended step-3 guard leaves alone. The
+  // maximal run of consecutive lines matching ^\s*(?:&gt;)+ ? is ONE
+  // <blockquote class="md-quote">: the leading (?:&gt;)+ run plus ONE
+  // optional space is stripped from each member (nested >> / >>>
+  // collapses to a single level — locked A1), members are joined with
+  // <br> (the paragraph convention), and a BLANK line terminates the
+  // group (a re-quoted line starts a new <blockquote>). Documented
+  // limit: a "- list" / "# heading" line INSIDE a quote renders as
+  // plain text — the inline chain ran first. Fences (step 1) and
+  // tables (step 1b) keep their precedence: a > inside a fence never
+  // reaches this pass, and a > in a table cell is restored in step 4.
+  const quoteLines = text.split("\n");
+  const quoted = [];
+  let qpos = 0;
+  while (qpos < quoteLines.length) {
+    if (!/^\s*(?:&gt;)+ ?/.test(quoteLines[qpos])) {
+      quoted.push(quoteLines[qpos]);
+      qpos += 1;
+      continue;
+    }
+    const members = [];
+    while (qpos < quoteLines.length && /^\s*(?:&gt;)+ ?/.test(quoteLines[qpos])) {
+      members.push(quoteLines[qpos].replace(/^\s*(?:&gt;)+ ?/, ""));
+      qpos += 1;
+    }
+    quoted.push(`<blockquote class="md-quote">${members.join("<br>")}</blockquote>`);
+  }
+  text = quoted.join("\n");
+
   // 3. Paragraphs (double newline separated).
   text = text
     .split(/\n{2,}/)
     .map((block) => {
       const b = block.trim();
       if (!b) return "";
-      if (/^<(h\d|ul|ol|pre|li)/.test(b)) return b;
+      if (/^<(h\d|ul|ol|pre|li|blockquote)/.test(b)) return b;
       return `<p>${b.replace(/\n/g, "<br>")}</p>`;
     })
     .join("");

frontend/assets/styles.css

@@ -541,6 +541,37 @@ body::before {
 .md-table th, .md-table td { border: 1px solid var(--line); padding: 0.4rem 0.6rem; text-align: left; vertical-align: top; }
 .md-table thead th { background: var(--surface); color: var(--ink); }
 
+/* Markdown blockquotes (phase 138, 2026-09-30, TODO L3): the shared
+   renderer (markdown.js step 2b) turns a run of "> "-prefixed lines
+   into <blockquote class="md-quote"> — ONE rule set serves all three
+   rendering contexts (the chat .bubble, the details.thinking
+   scratchpad, the document viewer's .doc-md): every one sits on the
+   --surface canvas (the deflected bubble's --accent-bg holds too —
+   ink-soft there is 6.9:1), so a single AA pairing covers them all.
+   A visible-but-restrained left border + padding + a muted ink — NO
+   background fill (locked A2). Palette vars only (the :root-drift
+   test parses the built-ins from this file — no hex literal here):
+   border-left  --brand-ink — 9.9:1 on --surface, the rose accent bar
+                (--line would be invisible: 1.14:1 on the surface;
+                plain --brand vanishes on the user bubble, 1:1);
+   color        --ink-soft  — 8.2:1 on --surface, the same AA pairing
+                              the --ink-soft :root comment documents.
+   Static content — no animation (nothing for prefers-reduced-motion
+   to still). */
+.md-quote {
+  border-left: 3px solid var(--brand-ink);
+  padding: 0.25rem 0.75rem;
+  margin: 0.5rem 0;
+  color: var(--ink-soft);
+}
+/* The USER bubble also runs the question through the shared renderer
+   (app.js addMessage), on the --brand fill with --bg text: --ink-soft
+   there is 1.6:1 — an AA failure — so the quote keeps the bubble's
+   own dark ink, 5.2:1 on --brand (the :root --bg pairing). The
+   --brand-ink bar holds 1.9:1 against the fill — still visible, the
+   quote stays distinct. */
+.msg.user .bubble .md-quote { color: var(--bg); }
+
 .msg.user { justify-content: flex-end; }
 .msg.user .msg-body { align-items: flex-end; }
 .msg.user .bubble {