core+app: agent headline for board rows + resizable preview rail

app/src-tauri/src/lib.rs

@@ -674,6 +674,9 @@ fn ingest_review_findings(state: &AppState, object_id: &str) -> &'static str {
             if let Some(intent) = review.intent {
                 r.distilled_intent = Some(intent);
             }
+            if let Some(headline) = review.headline {
+                r.distilled_headline = Some(headline);
+            }
         }
         if recap_present {
             r.recap_sha = Some(r.head_sha.clone());
@@ -788,6 +791,7 @@ async fn refresh_review_diff(state: &AppState, pr_ref: &PrRef) {
 fn clear_head_anchored_annotations(review: &mut Review) {
     review.review_findings.clear();
     review.distilled_intent = None;
+    review.distilled_headline = None;
 }
 
 /// Extract the PR number from a PR URL or reference string.
@@ -1420,6 +1424,7 @@ mod tests {
             conversation: vec![],
             last_reviewed_sha: None,
             distilled_intent: None,
+            distilled_headline: None,
             recap_sha: None,
         }
     }

app/src/App.tsx

@@ -52,6 +52,15 @@ import {
   saveDensity,
   WIDE_BREAKPOINT,
 } from "./lib/board-density";
+import {
+  clampRailWidth,
+  loadRailWidth,
+  saveRailWidth,
+  RAIL_DEFAULT_WIDTH,
+  RAIL_KEY_STEP,
+  RAIL_MIN_WIDTH,
+  RAIL_MAX_WIDTH,
+} from "./lib/rail-width";
 import type { GateState } from "./bindings/GateState";
 import type { DiffSide } from "./bindings/DiffSide";
 import type { Review } from "./bindings/Review";
@@ -301,6 +310,62 @@ function App() {
 
   // Triage-table selection (drives the preview rail), by PR ref.
   const [selectedPr, setSelectedPr] = useState<string | null>(null);
+
+  // User-resizable preview-rail width, persisted. Dragging tracks the pointer
+  // from a captured start position; the write happens once on release.
+  const [railWidth, setRailWidth] = useState<number>(loadRailWidth);
+  const railDrag = useRef<{ startX: number; startWidth: number } | null>(null);
+
+  const handleRailDragStart = useCallback(
+    (e: React.PointerEvent<HTMLDivElement>) => {
+      e.preventDefault();
+      e.currentTarget.setPointerCapture(e.pointerId);
+      railDrag.current = { startX: e.clientX, startWidth: railWidth };
+    },
+    [railWidth],
+  );
+  const handleRailDragMove = useCallback(
+    (e: React.PointerEvent<HTMLDivElement>) => {
+      const drag = railDrag.current;
+      if (drag === null) return;
+      // Dragging left widens the rail (the divider sits on its left edge).
+      setRailWidth(clampRailWidth(drag.startWidth + (drag.startX - e.clientX)));
+    },
+    [],
+  );
+  const handleRailDragEnd = useCallback(
+    (e: React.PointerEvent<HTMLDivElement>) => {
+      const drag = railDrag.current;
+      if (drag === null) return;
+      railDrag.current = null;
+      e.currentTarget.releasePointerCapture(e.pointerId);
+      saveRailWidth(clampRailWidth(drag.startWidth + (drag.startX - e.clientX)));
+    },
+    [],
+  );
+  const resetRailWidth = useCallback(() => {
+    setRailWidth(RAIL_DEFAULT_WIDTH);
+    saveRailWidth(RAIL_DEFAULT_WIDTH);
+  }, []);
+  const handleRailKeyDown = useCallback(
+    (e: React.KeyboardEvent<HTMLDivElement>) => {
+      // Left widens / right narrows, mirroring the drag direction.
+      const delta =
+        e.key === "ArrowLeft"
+          ? RAIL_KEY_STEP
+          : e.key === "ArrowRight"
+            ? -RAIL_KEY_STEP
+            : null;
+      if (delta === null) return;
+      e.preventDefault();
+      setRailWidth((w) => {
+        const next = clampRailWidth(w + delta);
+        saveRailWidth(next);
+        return next;
+      });
+    },
+    [],
+  );
   const requestDiffJump = useAppStore((s) => s.requestDiffJump);
   // Only render the preview rail when the window is wide enough for it.
   const railFits = useMediaQuery(RAIL_MIN_WIDTH_QUERY);
@@ -892,13 +957,33 @@ function App() {
             )}
           </div>
           {railFits && selectedReview !== null && (
-            <aside className="w-[380px] shrink-0 overflow-y-auto border-l border-border bg-card">
-              <BoardPreviewRail
-                review={selectedReview}
-                onOpen={handleOpenReview}
-                onJumpTo={handleRailJump}
+            <>
+              <div
+                role="separator"
+                aria-orientation="vertical"
+                aria-label="Resize preview rail"
+                aria-valuenow={railWidth}
+                aria-valuemin={RAIL_MIN_WIDTH}
+                aria-valuemax={RAIL_MAX_WIDTH}
+                tabIndex={0}
+                onPointerDown={handleRailDragStart}
+                onPointerMove={handleRailDragMove}
+                onPointerUp={handleRailDragEnd}
+                onDoubleClick={resetRailWidth}
+                onKeyDown={handleRailKeyDown}
+                className="w-1.5 shrink-0 cursor-col-resize outline-none transition-colors hover:bg-primary/30 focus-visible:bg-primary/40"
               />
-            </aside>
+              <aside
+                style={{ width: railWidth }}
+                className="shrink-0 overflow-y-auto border-l border-border bg-card"
+              >
+                <BoardPreviewRail
+                  review={selectedReview}
+                  onOpen={handleOpenReview}
+                  onJumpTo={handleRailJump}
+                />
+              </aside>
+            </>
           )}
         </>
       );

app/src/bindings/Review.ts

@@ -146,6 +146,15 @@ last_reviewed_sha: string | null,
  * legacy data.
  */
 distilled_intent: string | null, 
+/**
+ * The pre-review agent's one-line (≤120 chars) summary of what the PR
+ * does, for card and table-row display where a paragraph doesn't scan.
+ *
+ * Same lifecycle as [`Self::distilled_intent`]: advisory display only,
+ * cleared when the head moves, `None` before the first pre-pass and for
+ * legacy data (display falls back to the intent's first sentence).
+ */
+distilled_headline: string | null, 
 /**
  * The head SHA the rendered pre-review recap was generated at, for
  * staleness. `None` before any recap and for legacy data.

app/src/components/BoardTable.tsx

@@ -23,7 +23,7 @@ import { StatusLed } from "./StatusLed";
 import { cardSignal, toneTextClass } from "../lib/card-signal";
 import { actionConfigForState } from "../lib/review-action";
 import { parsePrDisplay } from "../lib/pr-ref";
-import { stripMarkdown } from "../lib/markdown-text";
+import { reviewHeadline } from "../lib/review-headline";
 import { findingCounts, severityMeta } from "../lib/finding-severity";
 import { ciState } from "../lib/ci";
 import { diffTotals, sizeClass, sizeClassLabel } from "../lib/diff-signals";
@@ -163,13 +163,10 @@ function BoardRow({
   const signal = cardSignal(review);
   const action = actionConfigForState(review.gate_state);
   const { number: prNumber } = parsePrDisplay(review.pr);
-  const intent = useMemo(
-    () =>
-      review.distilled_intent !== null
-        ? stripMarkdown(review.distilled_intent)
-        : null,
-    [review.distilled_intent],
-  );
+  // One scannable line, not a mid-cut paragraph: the agent's dedicated
+  // headline, or the intent's first sentence for pre-headline data. The full
+  // read lives in the preview rail and the Briefing.
+  const headline = useMemo(() => reviewHeadline(review), [review]);
 
   return (
     <div
@@ -212,12 +209,12 @@ function BoardRow({
       </div>
 
       {/* Agent's read */}
-      {intent !== null ? (
+      {headline !== null ? (
         <p
-          className="line-clamp-2 text-xs leading-snug text-muted-foreground"
-          title={intent}
+          className="truncate text-xs leading-snug text-muted-foreground"
+          title={headline}
         >
-          {intent}
+          {headline}
         </p>
       ) : (
         <span className="text-xs text-muted-foreground/50" aria-hidden="true">

app/src/lib/rail-width.test.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect } from "vitest";
+import {
+  clampRailWidth,
+  initialRailWidth,
+  RAIL_DEFAULT_WIDTH,
+  RAIL_MAX_WIDTH,
+  RAIL_MIN_WIDTH,
+} from "./rail-width";
+
+describe("clampRailWidth", () => {
+  it("clamps into the usable band and rounds", () => {
+    expect(clampRailWidth(100)).toBe(RAIL_MIN_WIDTH);
+    expect(clampRailWidth(10_000)).toBe(RAIL_MAX_WIDTH);
+    expect(clampRailWidth(400.6)).toBe(401);
+    expect(clampRailWidth(Number.NaN)).toBe(RAIL_DEFAULT_WIDTH);
+  });
+});
+
+describe("initialRailWidth", () => {
+  it("defaults when nothing or garbage is stored, clamps stored values", () => {
+    expect(initialRailWidth(null)).toBe(RAIL_DEFAULT_WIDTH);
+    expect(initialRailWidth("bogus")).toBe(RAIL_DEFAULT_WIDTH);
+    expect(initialRailWidth("500")).toBe(500);
+    expect(initialRailWidth("50")).toBe(RAIL_MIN_WIDTH);
+    expect(initialRailWidth("9999")).toBe(RAIL_MAX_WIDTH);
+  });
+});

app/src/lib/rail-width.ts

@@ -0,0 +1,46 @@
+/**
+ * Width model + persistence for the board's briefing preview rail.
+ *
+ * The rail is user-resizable by dragging its left edge (or arrow keys on the
+ * focused divider). The chosen width persists; malformed or out-of-range
+ * stored values clamp back into the usable band so a bad write can never
+ * produce an invisible or page-eating rail.
+ */
+
+/** localStorage key the persisted rail width (px) is stored under. */
+export const RAIL_WIDTH_KEY = "cockpit.board.railWidth";
+
+/** Narrowest useful rail: below this the findings rows wrap unreadably. */
+export const RAIL_MIN_WIDTH = 300;
+
+/** Widest allowed rail: keeps the triage table usable beside it. */
+export const RAIL_MAX_WIDTH = 720;
+
+/** Width before the user ever resizes (the D1 mockup's proportion). */
+export const RAIL_DEFAULT_WIDTH = 380;
+
+/** Step (px) for one arrow-key press on the focused resize divider. */
+export const RAIL_KEY_STEP = 16;
+
+/** Clamp any candidate width into the usable band. */
+export function clampRailWidth(width: number): number {
+  if (Number.isNaN(width)) return RAIL_DEFAULT_WIDTH;
+  return Math.min(RAIL_MAX_WIDTH, Math.max(RAIL_MIN_WIDTH, Math.round(width)));
+}
+
+/** Parse a stored raw value into a usable width, defaulting when malformed. */
+export function initialRailWidth(stored: string | null): number {
+  if (stored === null) return RAIL_DEFAULT_WIDTH;
+  const parsed = Number.parseInt(stored, 10);
+  return Number.isNaN(parsed) ? RAIL_DEFAULT_WIDTH : clampRailWidth(parsed);
+}
+
+/** Read the persisted rail width from `localStorage`. */
+export function loadRailWidth(): number {
+  return initialRailWidth(localStorage.getItem(RAIL_WIDTH_KEY));
+}
+
+/** Persist the user's rail width. */
+export function saveRailWidth(width: number): void {
+  localStorage.setItem(RAIL_WIDTH_KEY, String(clampRailWidth(width)));
+}

app/src/lib/review-headline.test.ts

@@ -0,0 +1,47 @@
+import { describe, it, expect } from "vitest";
+import { reviewHeadline } from "./review-headline";
+import { makeReview } from "../test/fixtures";
+
+describe("reviewHeadline", () => {
+  it("prefers the agent-authored headline verbatim", () => {
+    const review = {
+      ...makeReview(),
+      distilled_headline: "Adds share-by-email behind a flag",
+      distilled_intent: "A long paragraph. With more sentences.",
+    };
+    expect(reviewHeadline(review)).toBe("Adds share-by-email behind a flag");
+  });
+
+  it("falls back to the intent's first sentence for pre-headline data", () => {
+    const review = {
+      ...makeReview(),
+      distilled_headline: null,
+      distilled_intent:
+        "Implements the Share flow for NEX-1605: a new QuoteEmailService renders and sends. A new table links emails to quotes.",
+    };
+    expect(reviewHeadline(review)).toBe(
+      "Implements the Share flow for NEX-1605: a new QuoteEmailService renders and sends.",
+    );
+  });
+
+  it("caps a boundary-free fallback with an ellipsis", () => {
+    const review = {
+      ...makeReview(),
+      distilled_headline: null,
+      distilled_intent: "x".repeat(400),
+    };
+    const headline = reviewHeadline(review);
+    expect(headline).not.toBeNull();
+    expect(headline?.length).toBe(160);
+    expect(headline?.endsWith("…")).toBe(true);
+  });
+
+  it("returns null when the review has no agent read", () => {
+    const review = {
+      ...makeReview(),
+      distilled_headline: null,
+      distilled_intent: null,
+    };
+    expect(reviewHeadline(review)).toBeNull();
+  });
+});

app/src/lib/review-headline.ts

@@ -0,0 +1,41 @@
+import type { Review } from "../bindings/Review";
+import { stripMarkdown } from "./markdown-text";
+
+/**
+ * Longest fallback headline derived from the intent paragraph. The agent's own
+ * headline is capped harder (≤120) by the backend; this only bounds the
+ * first-sentence fallback for pre-headline data.
+ */
+const MAX_FALLBACK_CHARS = 160;
+
+/**
+ * The one-line summary of a review for cards and table rows.
+ *
+ * Prefers the agent-authored `distilled_headline` (a deliberate ≤80-char
+ * sentence from the pre-review contract). For reviews analyzed before the
+ * headline existed, falls back to the first sentence of the distilled intent —
+ * a mid-paragraph ellipsis cut is exactly what made the table column hard to
+ * scan. Returns null when the review has no agent read at all.
+ */
+export function reviewHeadline(review: Review): string | null {
+  if (review.distilled_headline !== null) return review.distilled_headline;
+  if (review.distilled_intent === null) return null;
+  const plain = stripMarkdown(review.distilled_intent).trim();
+  if (plain === "") return null;
+  return truncate(firstSentence(plain), MAX_FALLBACK_CHARS);
+}
+
+/**
+ * The first sentence of a paragraph: up to the first `.`, `!`, or `?` that is
+ * followed by whitespace or the end. Falls back to the whole text when no
+ * sentence boundary exists.
+ */
+function firstSentence(text: string): string {
+  const match = /^[\s\S]*?[.!?](?=\s|$)/.exec(text);
+  return (match?.[0] ?? text).trim();
+}
+
+/** Hard char cap with a single-character ellipsis. */
+function truncate(text: string, max: number): string {
+  return text.length <= max ? text : `${text.slice(0, max - 1).trimEnd()}…`;
+}

app/src/test/fixtures.ts

@@ -60,6 +60,7 @@ export function makeReview(overrides: Partial<Review> = {}): Review {
     ci_summary: null,
     last_reviewed_sha: null,
     distilled_intent: null,
+    distilled_headline: null,
     recap_sha: null,
   };
   return { ...base, ...overrides };

crates/cockpit-core/src/adapters/github.rs

@@ -944,6 +944,7 @@ pub fn build_review_from_pr(
         conversation: vec![],
         last_reviewed_sha: None,
         distilled_intent: None,
+        distilled_headline: None,
         recap_sha: None,
     }
 }
@@ -2665,6 +2666,7 @@ index 1111111..2222222 100644
             conversation: vec![],
             last_reviewed_sha: None,
             distilled_intent: None,
+            distilled_headline: None,
             recap_sha: None,
         }
     }