diff --git a/lib/analytics/__tests__/right-to-left-layout-support.test.ts b/lib/analytics/__tests__/right-to-left-layout-support.test.ts
new file mode 100644
index 0000000..29c26f0
--- /dev/null
+++ b/lib/analytics/__tests__/right-to-left-layout-support.test.ts
@@ -0,0 +1,14 @@
+import { describe, expect, it } from "vitest";
+import { evaluateRightToLeftLayoutSupport } from "../right-to-left-layout-support";
+
+describe("evaluateRightToLeftLayoutSupport", () => {
+  it("evaluates nominal, elevated, and critical thresholds deterministically", () => {
+    expect(evaluateRightToLeftLayoutSupport({ contextId: "ctx-1", primaryMetric: 15, secondaryMetric: 10, limitThreshold: 100 }).status).toBe("nominal");
+    expect(evaluateRightToLeftLayoutSupport({ contextId: "ctx-2", primaryMetric: 40, secondaryMetric: 20 }).status).toBe("elevated");
+    expect(evaluateRightToLeftLayoutSupport({ contextId: "ctx-3", primaryMetric: 70, secondaryMetric: 25, limitThreshold: 100 }).status).toBe("critical");
+  });
+
+  it("rejects blank contextId", () => {
+    expect(() => evaluateRightToLeftLayoutSupport({ contextId: "   ", primaryMetric: 1, secondaryMetric: 1 })).toThrow(/contextId is required/);
+  });
+});
diff --git a/lib/analytics/right-to-left-layout-support.ts b/lib/analytics/right-to-left-layout-support.ts
new file mode 100644
index 0000000..dd70d7f
--- /dev/null
+++ b/lib/analytics/right-to-left-layout-support.ts
@@ -0,0 +1,40 @@
+export interface RightToLeftLayoutSupportSummaryInput {
+  contextId: string;
+  primaryMetric: number;
+  secondaryMetric: number;
+  limitThreshold?: number;
+}
+
+export interface RightToLeftLayoutSupportSummary {
+  contextId: string;
+  primaryMetric: number;
+  secondaryMetric: number;
+  scoreBps: number;
+  status: "nominal" | "elevated" | "critical";
+}
+
+export function evaluateRightToLeftLayoutSupport(input: RightToLeftLayoutSupportSummaryInput): RightToLeftLayoutSupportSummary {
+  const contextId = input.contextId.trim();
+  if (!contextId) {
+    throw new Error("evaluateRightToLeftLayoutSupport: contextId is required");
+  }
+  const primaryMetric = Math.max(0, Math.trunc(input.primaryMetric));
+  const secondaryMetric = Math.max(0, Math.trunc(input.secondaryMetric));
+  const limit = Math.max(1, Math.trunc(input.limitThreshold ?? 100));
+
+  const scoreBps = Math.min(10000, Math.round(((primaryMetric + secondaryMetric) * 10000) / limit));
+  let status: "nominal" | "elevated" | "critical" = "nominal";
+  if (scoreBps >= 8500) {
+    status = "critical";
+  } else if (scoreBps >= 5000) {
+    status = "elevated";
+  }
+
+  return {
+    contextId,
+    primaryMetric,
+    secondaryMetric,
+    scoreBps,
+    status,
+  };
+}