diff --git a/config.json b/config.json
index 270a7f1..0898338 100644
--- a/config.json
+++ b/config.json
@@ -25,6 +25,11 @@
         ],
         "specs": ["specs", "rspec", "rstest", "coverage", "qlty coverage", "qlty coverage diff"],
         "e2e": ["Preview E2E *"]
+      },
+      "ignoreChecks": ["Preview E2E ${{ matrix.folder }}"],
+      "preview": {
+        "label": "preview",
+        "urlTemplate": "https://pr-{number}.argocd.testmd.co.uk/"
       }
     },
     {
diff --git a/server/categorize.ts b/server/categorize.ts
index c1d97be..81f8efa 100644
--- a/server/categorize.ts
+++ b/server/categorize.ts
@@ -68,6 +68,7 @@ export function categorize(rules: RepoRules | undefined, contexts: CheckContext[
   const buckets = new Map<CheckCategory, CheckInfo[]>(CATEGORIES.map((c) => [c, []]));
   for (const ctx of dedupeByName(contexts)) {
     const name = ctx.__typename === 'StatusContext' ? ctx.context : ctx.name;
+    if (rules?.ignore.has(name)) continue;
     buckets.get(categoryFor(rules, name))!.push({
       name,
       state: checkState(ctx),
diff --git a/server/config.ts b/server/config.ts
index a251177..63a2f71 100644
--- a/server/config.ts
+++ b/server/config.ts
@@ -15,6 +15,14 @@ const repoSchema = z.object({
       e2e: categorySchema.optional(),
     })
     .default({}),
+  ignoreChecks: z.array(z.string()).default([]),
+  preview: z
+    .object({
+      label: z.string(),
+      /** `{number}` is replaced with the PR number. */
+      urlTemplate: z.string(),
+    })
+    .optional(),
 });
 
 const muteRuleSchema = z.object({
@@ -47,6 +55,8 @@ interface GlobMatcher {
 export interface RepoRules {
   exact: Map<string, CheckCategory>;
   globs: GlobMatcher[];
+  ignore: Set<string>;
+  preview?: { label: string; urlTemplate: string };
 }
 
 export interface AppConfig extends RawConfig {
@@ -98,7 +108,12 @@ export function loadConfig(path = join(rootDir, 'config.json')): AppConfig {
         }
       }
     }
-    rulesByRepo.set(repo.name, { exact, globs });
+    rulesByRepo.set(repo.name, {
+      exact,
+      globs,
+      ignore: new Set(repo.ignoreChecks),
+      preview: repo.preview,
+    });
   }
 
   const parts = ['is:pr', 'is:open', ...raw.repos.map((r) => `repo:${r.name}`)];
diff --git a/server/db.ts b/server/db.ts
index 9b5444f..6bb4c5a 100644
--- a/server/db.ts
+++ b/server/db.ts
@@ -55,6 +55,7 @@ export interface EventInsert {
   reviewState: string | null;
   threadId: string | null;
   path: string | null;
+  diffHunk: string | null;
   read: boolean;
 }
 
@@ -76,6 +77,11 @@ export class Db {
     this.db.exec('PRAGMA foreign_keys = ON');
     this.db.exec(SCHEMA);
 
+    const eventCols = this.db.prepare('PRAGMA table_info(events)').all() as { name: string }[];
+    if (!eventCols.some((c) => c.name === 'diff_hunk')) {
+      this.db.exec('ALTER TABLE events ADD COLUMN diff_hunk TEXT');
+    }
+
     const clauses: string[] = [];
     for (const rule of opts.muteRules ?? []) {
       let clause = 'e.actor = ?';
@@ -155,10 +161,11 @@ export class Db {
     this.db
       .prepare(
         `INSERT INTO events (id, pr_id, kind, actor, created_at, updated_at, body_excerpt, url,
-                             review_state, thread_id, path, read, read_at)
-         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, NULL)
+                             review_state, thread_id, path, diff_hunk, read, read_at)
+         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, NULL)
          ON CONFLICT(id) DO UPDATE SET
-           body_excerpt = excluded.body_excerpt, updated_at = excluded.updated_at`,
+           body_excerpt = excluded.body_excerpt, updated_at = excluded.updated_at,
+           diff_hunk = excluded.diff_hunk`,
       )
       .run(
         e.id,
@@ -172,6 +179,7 @@ export class Db {
         e.reviewState,
         e.threadId,
         e.path,
+        e.diffHunk,
         e.read ? 1 : 0,
       );
   }
@@ -229,6 +237,7 @@ export class Db {
       reviewState: r.review_state as string | null,
       path: r.path as string | null,
       read: (r.read as number) === 1,
+      diffHunk: (r.diff_hunk as string | null) ?? null,
       inReplyTo:
         r.root_id && r.root_id !== r.id
           ? { actor: r.root_actor as string, bodyExcerpt: (r.root_body as string) ?? '' }
diff --git a/server/github/queries.ts b/server/github/queries.ts
index e4fe5aa..e4b7fa7 100644
--- a/server/github/queries.ts
+++ b/server/github/queries.ts
@@ -16,6 +16,7 @@ export const LIST_QUERY = /* GraphQL */ `
           headRefName
           headRefOid
           repository { nameWithOwner }
+          labels(first: 20) { nodes { name } }
           commits(last: 1) { nodes { commit { statusCheckRollup { state } } } }
           reviewThreads(first: 50) { totalCount nodes { isResolved } }
           comments(first: 1) { totalCount }
@@ -38,6 +39,7 @@ export interface ListPr {
   headRefName: string;
   headRefOid: string;
   repository: { nameWithOwner: string };
+  labels: { nodes: { name: string }[] };
   commits: { nodes: { commit: { statusCheckRollup: { state: string } | null } }[] };
   reviewThreads: { totalCount: number; nodes: { isResolved: boolean }[] };
   comments: { totalCount: number };
@@ -90,7 +92,7 @@ export const DETAIL_QUERY = /* GraphQL */ `
             isResolved
             path
             comments(first: 30) {
-              nodes { id author { login } bodyText createdAt updatedAt url }
+              nodes { id author { login } bodyText createdAt updatedAt url diffHunk }
             }
           }
         }
@@ -110,6 +112,8 @@ export interface DetailComment {
   createdAt: string;
   updatedAt: string;
   url: string;
+  /** Present only on review-thread comments. */
+  diffHunk?: string;
 }
 
 export interface DetailPr {
diff --git a/server/poller.ts b/server/poller.ts
index daadbe6..c2d62ee 100644
--- a/server/poller.ts
+++ b/server/poller.ts
@@ -36,6 +36,7 @@ function signature(pr: ListPr): string {
         pr.comments.totalCount,
         pr.reviews.totalCount,
         pr.latestReviews.nodes.map((r) => `${r.author?.login}:${r.state}`),
+        pr.labels.nodes.map((l) => l.name).sort(),
       ]),
     )
     .digest('hex');
@@ -59,14 +60,20 @@ async function fetchList(config: AppConfig): Promise<ListPr[]> {
 
 function buildSnapshot(config: AppConfig, pr: ListPr, detail: DetailPr | undefined, db: Db): PrSnapshot {
   const repo = pr.repository.nameWithOwner;
+  const rules = config.rulesByRepo.get(repo);
   let categories;
   if (detail) {
     const contexts = detail.commits.nodes[0]?.commit.statusCheckRollup?.contexts.nodes ?? [];
-    categories = categorize(config.rulesByRepo.get(repo), contexts);
+    categories = categorize(rules, contexts);
   } else {
     // Detail node inaccessible this round — keep the previous check breakdown.
-    categories = db.getSnapshot(pr.id)?.categories ?? categorize(config.rulesByRepo.get(repo), []);
+    categories = db.getSnapshot(pr.id)?.categories ?? categorize(rules, []);
   }
+  const labels = pr.labels.nodes.map((l) => l.name);
+  const previewUrl =
+    rules?.preview && labels.includes(rules.preview.label)
+      ? rules.preview.urlTemplate.replaceAll('{number}', String(pr.number))
+      : null;
   return {
     id: pr.id,
     repo,
@@ -77,6 +84,8 @@ function buildSnapshot(config: AppConfig, pr: ListPr, detail: DetailPr | undefin
     isDraft: pr.isDraft,
     branch: pr.headRefName,
     updatedAt: pr.updatedAt,
+    labels,
+    previewUrl,
     ...deriveReviewState(pr),
     verdicts: deriveVerdicts(pr),
     categories,
diff --git a/server/timeline.ts b/server/timeline.ts
index eacc086..1c079cd 100644
--- a/server/timeline.ts
+++ b/server/timeline.ts
@@ -8,6 +8,17 @@ function excerpt(text: string): string {
   return clean.length > EXCERPT_LEN ? `${clean.slice(0, EXCERPT_LEN - 1)}…` : clean;
 }
 
+const HUNK_LINES = 8;
+const HUNK_CHARS = 1200;
+
+/** GitHub's diffHunk ends at the commented line — keep the trailing context. */
+function trimHunk(hunk: string | undefined): string | null {
+  if (!hunk) return null;
+  const lines = hunk.split('\n');
+  const out = lines.slice(-HUNK_LINES).join('\n');
+  return out.length > HUNK_CHARS ? out.slice(-HUNK_CHARS) : out;
+}
+
 export interface TimelineOpts {
   user: string;
   /** First-ever sync: mark the historical backfill as already read. */
@@ -32,6 +43,7 @@ export function ingestTimeline(db: Db, pr: DetailPr, opts: TimelineOpts): number
       reviewState: null,
       threadId: null,
       path: null,
+      diffHunk: null,
       read: false,
     });
   }
@@ -50,6 +62,7 @@ export function ingestTimeline(db: Db, pr: DetailPr, opts: TimelineOpts): number
         reviewState: null,
         threadId: thread.id,
         path: thread.path,
+        diffHunk: trimHunk(c.diffHunk),
         read: false,
       });
     }
@@ -72,6 +85,7 @@ export function ingestTimeline(db: Db, pr: DetailPr, opts: TimelineOpts): number
       reviewState: r.state,
       threadId: null,
       path: null,
+      diffHunk: null,
       read: false,
     });
   }
diff --git a/shared/types.ts b/shared/types.ts
index 9260b43..490e8ed 100644
--- a/shared/types.ts
+++ b/shared/types.ts
@@ -36,6 +36,9 @@ export interface PrSnapshot {
   isDraft: boolean;
   branch: string;
   updatedAt: string;
+  labels: string[];
+  /** Per-PR review environment, when the repo configures one and the label matches. */
+  previewUrl: string | null;
   reviewState: ReviewState;
   unresolvedThreads: number;
   totalThreads: number;
@@ -59,6 +62,8 @@ export interface TimelineEvent {
   reviewState: string | null;
   path: string | null;
   read: boolean;
+  /** Trailing lines of the diff hunk a review comment is anchored to. */
+  diffHunk: string | null;
   /** Set when this is a reply within a review thread: the thread's root comment. */
   inReplyTo: { actor: string; bodyExcerpt: string } | null;
 }
diff --git a/web/src/components/PrCard.tsx b/web/src/components/PrCard.tsx
index 29147f8..45767e5 100644
--- a/web/src/components/PrCard.tsx
+++ b/web/src/components/PrCard.tsx
@@ -20,6 +20,11 @@ export default function PrCard({ pr, unread }: { pr: PrSnapshot; unread: number
           {pr.branch}
         </span>
         <span>{relativeTime(pr.updatedAt)}</span>
+        {pr.previewUrl && (
+          <a className="preview-link" href={pr.previewUrl} target="_blank" rel="noreferrer">
+            preview ↗
+          </a>
+        )}
       </div>
       <div className="chips-row">
         <ReviewBadge pr={pr} />
diff --git a/web/src/components/Timeline.tsx b/web/src/components/Timeline.tsx
index c6bd270..bf19e96 100644
--- a/web/src/components/Timeline.tsx
+++ b/web/src/components/Timeline.tsx
@@ -62,14 +62,43 @@ function KindLabel({ event }: { event: TimelineEvent }) {
   if (event.kind === 'review_comment') {
     return (
       <span>
-        commented{event.path ? ' on ' : ''}
-        {event.path && <span className="path">{event.path.split('/').pop()}</span>}
+        {event.inReplyTo ? 'replied' : 'commented'}
+        {event.path ? ' on ' : ''}
+        {event.path && (
+          <span className="path" title={event.path}>
+            {event.path.split('/').pop()}
+          </span>
+        )}
       </span>
     );
   }
   return <span>commented</span>;
 }
 
+function DiffHunk({ hunk }: { hunk: string }) {
+  return (
+    <pre className="tl-diff">
+      {hunk.split('\n').map((line, i) => (
+        <span
+          key={i}
+          className={
+            line.startsWith('+')
+              ? 'diff-add'
+              : line.startsWith('-')
+                ? 'diff-del'
+                : line.startsWith('@@')
+                  ? 'diff-meta'
+                  : ''
+          }
+        >
+          {line || ' '}
+          {'\n'}
+        </span>
+      ))}
+    </pre>
+  );
+}
+
 export default function Timeline() {
   const [unreadOnly, setUnreadOnly] = useState(false);
   const queryClient = useQueryClient();
@@ -144,14 +173,18 @@ export default function Timeline() {
                     readMutation.mutate({ id: e.id, read: !e.read });
                   }}
                 />
-                <div>
+                <div className="tl-content">
                   <div className="tl-kind">
                     <KindLabel event={e} />
                   </div>
+                  {e.diffHunk && !e.inReplyTo && <DiffHunk hunk={e.diffHunk} />}
                   {e.inReplyTo && (
-                    <div className="tl-reply-ctx">
-                      ↳ <span className="actor">{e.inReplyTo.actor}</span>:{' '}
-                      {e.inReplyTo.bodyExcerpt}
+                    <div className="tl-thread">
+                      {e.diffHunk && <DiffHunk hunk={e.diffHunk} />}
+                      <div className="tl-reply-ctx">
+                        <span className="actor">{e.inReplyTo.actor}</span>{' '}
+                        {e.inReplyTo.bodyExcerpt}
+                      </div>
                     </div>
                   )}
                   {e.bodyExcerpt && <div className="body">{e.bodyExcerpt}</div>}
diff --git a/web/src/styles/app.css b/web/src/styles/app.css
index aebfa45..a46fbfd 100644
--- a/web/src/styles/app.css
+++ b/web/src/styles/app.css
@@ -288,6 +288,19 @@ button {
   white-space: nowrap;
 }
 
+.preview-link {
+  color: var(--accent);
+  text-decoration: none;
+  font-weight: 600;
+  border: 1px solid var(--border);
+  border-radius: 4px;
+  padding: 0 5px;
+}
+
+.preview-link:hover {
+  border-color: var(--accent);
+}
+
 .unread-pill {
   background: var(--unread);
   color: #fff;
@@ -580,11 +593,20 @@ a.check-row:hover {
   background: var(--unread);
 }
 
+.tl-content {
+  min-width: 0;
+  flex: 1;
+}
+
+.tl-thread {
+  border-left: 2px solid var(--hairline);
+  padding-left: 8px;
+  margin: 3px 0;
+}
+
 .tl-reply-ctx {
   font-size: 12px;
   color: var(--ink-muted);
-  border-left: 2px solid var(--hairline);
-  padding-left: 7px;
   margin: 2px 0;
   display: -webkit-box;
   -webkit-line-clamp: 2;
@@ -597,6 +619,39 @@ a.check-row:hover {
   font-weight: 600;
 }
 
+.tl-diff {
+  margin: 3px 0;
+  padding: 6px 8px;
+  border: 1px solid var(--hairline);
+  border-radius: 6px;
+  background: var(--page);
+  font-family: ui-monospace, monospace;
+  font-size: 11px;
+  line-height: 1.5;
+  overflow-x: auto;
+  white-space: pre;
+  max-height: 160px;
+  overflow-y: auto;
+}
+
+.tl-diff .diff-add {
+  color: var(--status-pass-text);
+  background: var(--chip-pass-bg);
+  display: inline-block;
+  min-width: 100%;
+}
+
+.tl-diff .diff-del {
+  color: var(--status-fail-text);
+  background: var(--chip-fail-bg);
+  display: inline-block;
+  min-width: 100%;
+}
+
+.tl-diff .diff-meta {
+  color: var(--ink-muted);
+}
+
 .tl-item .body {
   color: var(--ink-secondary);
   font-size: 13px;