diff --git a/.env.example b/.env.example
index 9536558737..c9b3042c9f 100644
--- a/.env.example
+++ b/.env.example
@@ -68,28 +68,28 @@ GITTENSORY_REVIEW_ENRICHMENT=false
 # commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
-# conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,i18n
-# commitLint
+# conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
+# i18n,commitLint
 #
 # Profile defaults:
 # fast: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,secretLog,typosquat,iacMisconfig,nativeBuild
 # testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber,conflictMarker
-# debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,i18n
+# debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y,i18n
 # balanced (default): dependency,dependencyDiff,lockfileDrift,secret,license,installScript
 # heavyDependency,hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight
 # typosquat,commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication
 # churnHotspot,blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch
 # commitHygiene,pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology
 # todoMarker,magicNumber,conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting
-# errorSwallow,unsafeAny,i18n,commitLint
+# errorSwallow,unsafeAny,a11y,i18n,commitLint
 # deep: dependency,dependencyDiff,lockfileDrift,secret,license,installScript,heavyDependency
 # hardcodedUrl,actionPin,eol,redos,provenance,codeowners,secretLog,assetWeight,typosquat
 # commitSignature,iacMisconfig,nativeBuild,history,docCommentDrift,duplication,churnHotspot
 # blameLink,approvalIntegrity,ciCheckSignals,undocumentedExport,staleBranch,commitHygiene
 # pendingReviewRequests,testRatio,migrationSafety,looseRange,terminology,todoMarker,magicNumber
-# conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,i18n
-# commitLint
+# conflictMarker,debugLeftover,sizeSmell,floatingPromise,deepNesting,errorSwallow,unsafeAny,a11y
+# i18n,commitLint
 # END GENERATED REES ANALYZERS
 
 # Submitter-reputation spend control (internal-only): downgrades new/burst/low-rep
diff --git a/apps/gittensory-ui/src/lib/rees-analyzers.ts b/apps/gittensory-ui/src/lib/rees-analyzers.ts
index 9620f8fdf9..960b4ab37f 100644
--- a/apps/gittensory-ui/src/lib/rees-analyzers.ts
+++ b/apps/gittensory-ui/src/lib/rees-analyzers.ts
@@ -1071,6 +1071,29 @@ export const REES_ANALYZERS = [
         "Structural regex only (no type-checker). String literals and comment lines are skipped; findings are capped.",
     },
   },
+  {
+    name: "a11y",
+    title: "Accessibility regressions",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    profiles: ["fast", "balanced", "deep"],
+    requires: ["files"],
+    limits: {
+      maxFindings: 25,
+      maxLineChars: 2000,
+    },
+    docs: {
+      summary: "Flags common accessibility regressions in newly added JSX/HTML markup lines.",
+      looksAt:
+        "Added lines in changed non-test .jsx/.tsx/.html/.vue files for missing img alt text, click-only handlers, unlabeled controls, and positive tabindex.",
+      reports:
+        "File, line, and rule: img-alt, click-events-have-key-events, label-control, or positive-tabindex.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Structural markup heuristics only — buttons/links and controls with aria-label/id associations are not flagged.",
+    },
+  },
   {
     name: "i18n",
     title: "i18n regressions",
diff --git a/review-enrichment/analyzer-metadata.json b/review-enrichment/analyzer-metadata.json
index e06196056c..eb783794b9 100644
--- a/review-enrichment/analyzer-metadata.json
+++ b/review-enrichment/analyzer-metadata.json
@@ -1213,6 +1213,32 @@
         "notes": "Structural regex only (no type-checker). String literals and comment lines are skipped; findings are capped."
       }
     },
+    {
+      "name": "a11y",
+      "title": "Accessibility regressions",
+      "category": "quality",
+      "cost": "local",
+      "defaultEnabled": true,
+      "profiles": [
+        "fast",
+        "balanced",
+        "deep"
+      ],
+      "requires": [
+        "files"
+      ],
+      "limits": {
+        "maxFindings": 25,
+        "maxLineChars": 2000
+      },
+      "docs": {
+        "summary": "Flags common accessibility regressions in newly added JSX/HTML markup lines.",
+        "looksAt": "Added lines in changed non-test .jsx/.tsx/.html/.vue files for missing img alt text, click-only handlers, unlabeled controls, and positive tabindex.",
+        "reports": "File, line, and rule: img-alt, click-events-have-key-events, label-control, or positive-tabindex.",
+        "network": "Pure local analyzer. No external network call.",
+        "notes": "Structural markup heuristics only — buttons/links and controls with aria-label/id associations are not flagged."
+      }
+    },
     {
       "name": "i18n",
       "title": "i18n regressions",
diff --git a/review-enrichment/src/analyzers/a11y-regression.ts b/review-enrichment/src/analyzers/a11y-regression.ts
new file mode 100644
index 0000000000..156a5fdf2e
--- /dev/null
+++ b/review-enrichment/src/analyzers/a11y-regression.ts
@@ -0,0 +1,124 @@
+// Accessibility regression analyzer (#2026). Flags common a11y regressions in newly added JSX/HTML markup:
+// images without alt text, click-only handlers on non-interactive elements, unlabeled form controls, and
+// positive tabindex values. Pure compute over added lines in .jsx/.tsx/.html/.vue files, no network.
+import type { A11yFinding, EnrichRequest } from "../types.js";
+import { isTestPath } from "./test-ratio.js";
+
+const MAX_FINDINGS = 25;
+const MAX_LINE_CHARS = 2000;
+
+const MARKUP_PATH_RE = /\.(?:tsx|jsx|html|vue)$/i;
+
+const POSITIVE_TABINDEX_RE =
+  /\btabIndex\s*=\s*\{\s*([1-9]\d*)\s*\}|\btabindex\s*=\s*["']([1-9]\d*)["']/i;
+const IMG_TAG_RE = /<img\b/i;
+const ALT_ATTR_RE = /\balt\s*=/i;
+const ON_CLICK_RE = /\bonClick\s*=/;
+const KEYBOARD_HANDLER_RE = /\bonKey(?:Down|Up|Press)\s*=/;
+const INTERACTIVE_TAG_RE = /<(?:button|a)\b/i;
+const INTERACTIVE_ROLE_RE =
+  /\brole\s*=\s*["'](?:button|link|menuitem|tab|switch|checkbox|radio)["']/i;
+const NON_INTERACTIVE_CLICK_TARGET_RE =
+  /<(?:div|span|p|li|td|tr|section|article|header|footer|main|nav)\b/i;
+const FORM_CONTROL_RE = /<(?:input|select|textarea)\b/i;
+const LABEL_ASSOC_RE = /\b(?:aria-label|aria-labelledby|id)\s*=|<label\b/i;
+
+function isCommentLine(line: string): boolean {
+  const trimmed = line.trimStart();
+  return /^(?:\/\/|\/\*|\*|<!--|import\b|from\b)/.test(trimmed);
+}
+
+function isMarkupPath(path: string): boolean {
+  return MARKUP_PATH_RE.test(path) && !isTestPath(path);
+}
+
+/** Classify one added markup line for an a11y regression, or null. Pure. */
+export function detectA11yRegression(line: string): A11yFinding["rule"] | null {
+  if (isCommentLine(line) || line.length > MAX_LINE_CHARS) return null;
+
+  if (POSITIVE_TABINDEX_RE.test(line)) return "positive-tabindex";
+
+  if (IMG_TAG_RE.test(line) && !ALT_ATTR_RE.test(line)) return "img-alt";
+
+  if (ON_CLICK_RE.test(line)) {
+    const hasKeyboard = KEYBOARD_HANDLER_RE.test(line);
+    const isInteractive =
+      INTERACTIVE_TAG_RE.test(line) || INTERACTIVE_ROLE_RE.test(line);
+    if (
+      !hasKeyboard &&
+      !isInteractive &&
+      NON_INTERACTIVE_CLICK_TARGET_RE.test(line)
+    ) {
+      return "click-events-have-key-events";
+    }
+  }
+
+  if (FORM_CONTROL_RE.test(line) && !LABEL_ASSOC_RE.test(line)) {
+    return "label-control";
+  }
+
+  return null;
+}
+
+type ScanLimits = {
+  maxFindings?: number;
+  signal?: AbortSignal;
+};
+
+/** Scan one file patch's added lines for a11y regressions, line-cited via hunk headers. Pure. */
+export function scanPatchForA11yRegression(
+  path: string,
+  patch: string,
+  limits: ScanLimits = {},
+): A11yFinding[] {
+  const maxFindings = limits.maxFindings ?? MAX_FINDINGS;
+  if (maxFindings <= 0 || !isMarkupPath(path)) return [];
+
+  const findings: A11yFinding[] = [];
+  let newLine = 0;
+  let inHunk = false;
+
+  for (const line of patch.split("\n")) {
+    if (limits.signal?.aborted) throw new Error("analyzer_aborted");
+    const hunk = /^@@ -\d+(?:,\d+)? \+(\d+)(?:,\d+)? @@/.exec(line);
+    if (hunk) {
+      newLine = Number(hunk[1]);
+      inHunk = true;
+      continue;
+    }
+    if (!inHunk) continue;
+    if (line.startsWith("+")) {
+      const body = line.slice(1);
+      const rule = detectA11yRegression(body);
+      if (rule) {
+        findings.push({ file: path, line: newLine, rule });
+        if (findings.length >= maxFindings) return findings;
+      }
+      newLine++;
+    } else if (!line.startsWith("-") && !line.startsWith("\\")) {
+      newLine++;
+    }
+  }
+
+  return findings;
+}
+
+/** Analyzer entrypoint: scan markup files for accessibility regressions. */
+export async function scanA11yRegression(
+  req: EnrichRequest,
+  signal?: AbortSignal,
+): Promise<A11yFinding[]> {
+  const findings: A11yFinding[] = [];
+  for (const file of req.files ?? []) {
+    if (signal?.aborted) throw new Error("analyzer_aborted");
+    if (!file.patch) continue;
+    for (const finding of scanPatchForA11yRegression(file.path, file.patch, {
+      maxFindings: MAX_FINDINGS - findings.length,
+      signal,
+    })) {
+      findings.push(finding);
+      if (findings.length >= MAX_FINDINGS) return findings;
+    }
+  }
+  return findings;
+}
diff --git a/review-enrichment/src/analyzers/registry.ts b/review-enrichment/src/analyzers/registry.ts
index 2f64a03cb5..24bb153e14 100644
--- a/review-enrichment/src/analyzers/registry.ts
+++ b/review-enrichment/src/analyzers/registry.ts
@@ -37,6 +37,7 @@ import { scanI18nRegression } from "./i18n-regression.js";
 import { scanErrorSwallow } from "./error-swallow.js";
 import { scanFloatingPromise } from "./floating-promise.js";
 import { scanSizeSmell } from "./size-smell.js";
+import { scanA11yRegression } from "./a11y-regression.js";
 import { scanCommitLint } from "./commit-lint.js";
 import { scanUnsafeAny } from "./unsafe-any.js";
 import { scanTerminology } from "./terminology.js";
@@ -1167,6 +1168,37 @@ export const ANALYZER_DESCRIPTORS = [
     },
     run: (req, { signal }) => scanUnsafeAny(req, signal),
   }),
+  descriptor({
+    name: "a11y",
+    title: "Accessibility regressions",
+    category: "quality",
+    cost: "local",
+    defaultEnabled: true,
+    requires: ["files"],
+    limits: { maxFindings: 25, maxLineChars: 2000 },
+    docs: {
+      summary:
+        "Flags common accessibility regressions in newly added JSX/HTML markup lines.",
+      looksAt:
+        "Added lines in changed non-test .jsx/.tsx/.html/.vue files for missing img alt text, click-only handlers, unlabeled controls, and positive tabindex.",
+      reports:
+        "File, line, and rule: img-alt, click-events-have-key-events, label-control, or positive-tabindex.",
+      network: "Pure local analyzer. No external network call.",
+      notes:
+        "Structural markup heuristics only — buttons/links and controls with aria-label/id associations are not flagged.",
+    },
+    render: (findings, helpers) => {
+      if (!findings.length) return [];
+      const lines = ["### Accessibility regressions (added markup)"];
+      for (const item of findings) {
+        lines.push(
+          `- ${helpers.safeCodeSpan(`${item.file}:${item.line}`)} — ${helpers.safeCodeSpan(item.rule)}`,
+        );
+      }
+      return lines;
+    },
+    run: (req, { signal }) => scanA11yRegression(req, signal),
+  }),
   descriptor({
     name: "i18n",
     title: "i18n regressions",
diff --git a/review-enrichment/src/render.ts b/review-enrichment/src/render.ts
index 5039c10652..63b97b26b5 100644
--- a/review-enrichment/src/render.ts
+++ b/review-enrichment/src/render.ts
@@ -491,6 +491,7 @@ export function renderBrief(
   lines.push(...renderDescriptorSection("deepNesting", findings.deepNesting));
   lines.push(...renderDescriptorSection("errorSwallow", findings.errorSwallow));
   lines.push(...renderDescriptorSection("unsafeAny", findings.unsafeAny));
+  lines.push(...renderDescriptorSection("a11y", findings.a11y));
   lines.push(...renderDescriptorSection("i18n", findings.i18n));
   lines.push(...renderDescriptorSection("hardcodedUrl", findings.hardcodedUrl));
   lines.push(...renderDescriptorSection("commitLint", findings.commitLint));
diff --git a/review-enrichment/src/types.ts b/review-enrichment/src/types.ts
index c2183577be..1fb604edf1 100644
--- a/review-enrichment/src/types.ts
+++ b/review-enrichment/src/types.ts
@@ -536,6 +536,18 @@ export interface UnsafeAnyFinding {
   kind: "annotation" | "cast" | "assertion";
 }
 
+/** A common accessibility regression in newly added markup (#2026, part of #1499).
+ *  Reports file, line, and rule only — never string content. */
+export interface A11yFinding {
+  file: string;
+  line: number;
+  rule:
+    | "img-alt"
+    | "click-events-have-key-events"
+    | "label-control"
+    | "positive-tabindex";
+}
+
 /** An absolute HTTP(S) URL or raw IP:port endpoint hardcoded in non-test, non-config source (#2027, part of #1499).
  *  Reports location, kind, and a redacted/truncated host — never full paths or query strings. */
 export interface HardcodedUrlFinding {
@@ -597,6 +609,7 @@ export interface BriefFindings {
   deepNesting?: DeepNestingFinding[];
   errorSwallow?: ErrorSwallowFinding[];
   unsafeAny?: UnsafeAnyFinding[];
+  a11y?: A11yFinding[];
   i18n?: I18nFinding[];
   hardcodedUrl?: HardcodedUrlFinding[];
   commitLint?: CommitLintFinding[];
diff --git a/review-enrichment/test/a11y-regression.test.ts b/review-enrichment/test/a11y-regression.test.ts
new file mode 100644
index 0000000000..95dc52ea3f
--- /dev/null
+++ b/review-enrichment/test/a11y-regression.test.ts
@@ -0,0 +1,89 @@
+// Units for the a11y regression analyzer (#2026). Own file so concurrent analyzer PRs don't collide.
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import {
+  detectA11yRegression,
+  scanA11yRegression,
+  scanPatchForA11yRegression,
+} from "../dist/analyzers/a11y-regression.js";
+import { renderBrief } from "../dist/render.js";
+
+const patchOf = (lines: string[]) =>
+  `@@ -1,0 +1,${lines.length} @@\n${lines.map((l) => `+${l}`).join("\n")}`;
+
+test("detectA11yRegression: flags each rule on representative markup", () => {
+  assert.equal(detectA11yRegression('<img src="/logo.png" />'), "img-alt");
+  assert.equal(
+    detectA11yRegression('<div onClick={() => open()}>Open</div>'),
+    "click-events-have-key-events",
+  );
+  assert.equal(detectA11yRegression('<input type="email" />'), "label-control");
+  assert.equal(detectA11yRegression('<div tabIndex={3}>Skip</div>'), "positive-tabindex");
+});
+
+test("detectA11yRegression: does not flag compliant markup", () => {
+  assert.equal(detectA11yRegression('<img alt="Logo" src="/logo.png" />'), null);
+  assert.equal(detectA11yRegression('<button onClick={() => open()}>Open</button>'), null);
+  assert.equal(
+    detectA11yRegression('<div role="button" onClick={() => open()}>Open</div>'),
+    null,
+  );
+  assert.equal(
+    detectA11yRegression('<div onClick={() => open()} onKeyDown={handleKey}>Open</div>'),
+    null,
+  );
+  assert.equal(detectA11yRegression('<input aria-label="Email" type="email" />'), null);
+  assert.equal(detectA11yRegression("<label><input type=\"email\" /></label>"), null);
+  assert.equal(detectA11yRegression('<div tabIndex={0}>Focusable</div>'), null);
+});
+
+test("scanPatchForA11yRegression: flags added lines with correct locations", () => {
+  const findings = scanPatchForA11yRegression(
+    "src/Widget.tsx",
+    patchOf([
+      "export function Widget() {",
+      '  return <img src="/logo.png" />;',
+      "}",
+    ]),
+  );
+  assert.deepEqual(findings, [
+    { file: "src/Widget.tsx", line: 2, rule: "img-alt" },
+  ]);
+});
+
+test("scanPatchForA11yRegression: skips test files and non-markup paths", () => {
+  assert.deepEqual(
+    scanPatchForA11yRegression("src/Widget.test.tsx", patchOf(['<img src="/x" />'])),
+    [],
+  );
+  assert.deepEqual(
+    scanPatchForA11yRegression("src/worker.ts", patchOf(['<img src="/x" />'])),
+    [],
+  );
+});
+
+test("scanPatchForA11yRegression: respects the findings cap", () => {
+  const lines = Array.from({ length: 10 }, () => '<img src="/x" />');
+  assert.equal(
+    scanPatchForA11yRegression("src/a.tsx", patchOf(lines), { maxFindings: 2 }).length,
+    2,
+  );
+});
+
+test("scanA11yRegression: aggregates across files and renders a public-safe brief", async () => {
+  const findings = await scanA11yRegression({
+    repoFullName: "owner/repo",
+    prNumber: 1,
+    files: [
+      { path: "src/a.tsx", patch: patchOf(['<div tabIndex={5}>Skip</div>']) },
+      { path: "src/b.html", patch: patchOf(['<input type="text" />']) },
+    ],
+  });
+  assert.equal(findings.length, 2);
+  assert.equal(findings[0]?.rule, "positive-tabindex");
+  assert.equal(findings[1]?.rule, "label-control");
+  const { promptSection } = renderBrief({ a11y: findings });
+  assert.match(promptSection, /Accessibility regressions/);
+  assert.match(promptSection, /positive-tabindex/);
+  assert.doesNotMatch(promptSection, /Skip/);
+});
diff --git a/review-enrichment/test/analyzer-registry.test.ts b/review-enrichment/test/analyzer-registry.test.ts
index 9db05f6470..133ab89d9a 100644
--- a/review-enrichment/test/analyzer-registry.test.ts
+++ b/review-enrichment/test/analyzer-registry.test.ts
@@ -53,6 +53,7 @@ const EXPECTED_ANALYZERS = [
   "deepNesting",
   "errorSwallow",
   "unsafeAny",
+  "a11y",
   "i18n",
   "commitLint",
 ];
diff --git a/src/review/enrichment-analyzer-names.ts b/src/review/enrichment-analyzer-names.ts
index 7b22b22aff..8c7113c29e 100644
--- a/src/review/enrichment-analyzer-names.ts
+++ b/src/review/enrichment-analyzer-names.ts
@@ -47,6 +47,7 @@ export const REES_ANALYZER_NAMES = [
   "deepNesting",
   "errorSwallow",
   "unsafeAny",
+  "a11y",
   "i18n",
   "commitLint",
 ] as const;