diff --git a/src/resources/extensions/sf/tests/uok-metrics-exposition.test.mjs b/src/resources/extensions/sf/tests/uok-metrics-exposition.test.mjs
new file mode 100644
index 000000000..77a5ed2b4
--- /dev/null
+++ b/src/resources/extensions/sf/tests/uok-metrics-exposition.test.mjs
@@ -0,0 +1,82 @@
+/**
+ * uok-metrics-exposition.test.mjs — Prometheus metrics cache behaviour.
+ *
+ * Purpose: prove cached UOK metric snapshots are explicitly refreshable so
+ * health surfaces can trade scrape cost for freshness without serving stale
+ * data after known DB writes.
+ */
+import assert from "node:assert/strict";
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, test } from "vitest";
+import { closeDatabase, insertGateRun, openDatabase } from "../sf-db.js";
+import {
+	invalidateMetricsCache,
+	readUokMetrics,
+	writeUokMetrics,
+} from "../uok/metrics-exposition.js";
+
+const tmpDirs = [];
+
+afterEach(() => {
+	closeDatabase();
+	invalidateMetricsCache();
+	while (tmpDirs.length > 0) {
+		const dir = tmpDirs.pop();
+		if (dir) rmSync(dir, { recursive: true, force: true });
+	}
+});
+
+function makeProject() {
+	const dir = mkdtempSync(join(tmpdir(), "sf-uok-metrics-"));
+	tmpDirs.push(dir);
+	openDatabase(":memory:");
+	return dir;
+}
+
+function recordGateRun(outcome, evaluatedAt = new Date().toISOString()) {
+	insertGateRun({
+		traceId: `trace-${outcome}`,
+		turnId: `turn-${outcome}`,
+		gateId: "cache-gate",
+		gateType: "verification",
+		unitType: "execute-task",
+		unitId: "M001/S01/T01",
+		milestoneId: "M001",
+		sliceId: "S01",
+		taskId: "T01",
+		outcome,
+		failureClass: outcome === "pass" ? "" : "assertion",
+		rationale: outcome,
+		findings: "",
+		attempt: 1,
+		maxAttempts: 1,
+		retryable: false,
+		evaluatedAt,
+		durationMs: outcome === "pass" ? 10 : 20,
+	});
+}
+
+test("writeUokMetrics_when_cache_invalidated_refreshes_db_snapshot", () => {
+	const project = makeProject();
+	recordGateRun("pass");
+
+	writeUokMetrics(project, ["cache-gate"]);
+	const first = readUokMetrics(project);
+	assert.match(first, /uok_gate_runs_total\{gate_id="cache-gate"\} 1/);
+
+	recordGateRun("fail");
+	writeUokMetrics(project, ["cache-gate"]);
+	const cached = readUokMetrics(project);
+	assert.match(cached, /uok_gate_runs_total\{gate_id="cache-gate"\} 1/);
+
+	invalidateMetricsCache();
+	writeUokMetrics(project, ["cache-gate"]);
+	const refreshed = readUokMetrics(project);
+	assert.match(refreshed, /uok_gate_runs_total\{gate_id="cache-gate"\} 2/);
+	assert.match(
+		refreshed,
+		/uok_gate_runs_failed_total\{gate_id="cache-gate"\} 1/,
+	);
+});
diff --git a/src/resources/extensions/sf/uok/metrics-exposition.js b/src/resources/extensions/sf/uok/metrics-exposition.js
index a9f32b2b9..aeb7ecf96 100644
--- a/src/resources/extensions/sf/uok/metrics-exposition.js
+++ b/src/resources/extensions/sf/uok/metrics-exposition.js
@@ -99,7 +99,7 @@ function collectGateMetrics(gateIds) {
 	return lines;
 }
 
-function buildMetricsText(gateIds) {
+export function buildMetricsText(gateIds) {
 	const cacheKey = gateIds ? gateIds.join(",") : "";
 	const now = Date.now();
 	if (