diff --git a/backend-java/src/test/java/com/nanri/aiimage/metrics/TempDiskMetricsTest.java b/backend-java/src/test/java/com/nanri/aiimage/metrics/TempDiskMetricsTest.java
new file mode 100644
index 00000000..cf76454e
--- /dev/null
+++ b/backend-java/src/test/java/com/nanri/aiimage/metrics/TempDiskMetricsTest.java
@@ -0,0 +1,79 @@
+package com.nanri.aiimage.metrics;
+
+import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-187：临时磁盘容量/占用指标契约（spec 11 §1，09 临时磁盘巡检/告警接线面）。
+ * aiimage.tmpdisk.capacity/used gauge，标签 path；与 09 告警阈值联动时可直接读值比判。
+ */
+class TempDiskMetricsTest {
+
+    private final SimpleMeterRegistry registry = new SimpleMeterRegistry();
+    private final TaskObservabilityMetrics metrics = new TaskObservabilityMetrics("server-110", registry);
+
+    private static final String TMP = "/data/tmp-files";
+
+    @Test
+    void diskCapacityMeasured() {
+        metrics.disk(TMP, 100_000_000L, 30_000_000L);
+        assertEquals(100_000_000.0,
+                registry.get("aiimage.tmpdisk.capacity").tag("path", TMP).gauge().value(), 0.001);
+    }
+
+    @Test
+    void diskUsedMeasured() {
+        metrics.disk(TMP, 100_000_000L, 30_000_000L);
+        assertEquals(30_000_000.0,
+                registry.get("aiimage.tmpdisk.used").tag("path", TMP).gauge().value(), 0.001);
+    }
+
+    @Test
+    void usagePercentDerivableForThreshold() {
+        metrics.disk(TMP, 100_000_000L, 90_000_000L);
+        double capacity = registry.get("aiimage.tmpdisk.capacity").tag("path", TMP).gauge().value();
+        double used = registry.get("aiimage.tmpdisk.used").tag("path", TMP).gauge().value();
+        double percent = used / capacity * 100;
+        assertEquals(90.0, percent, 0.001, "09 告警可按占用百分比比判阈值");
+    }
+
+    @Test
+    void emptyDirectoryRecordsZero() {
+        metrics.disk(TMP, 100_000_000L, 0L);
+        assertEquals(0.0, registry.get("aiimage.tmpdisk.used").tag("path", TMP).gauge().value(), 0.001);
+    }
+
+    @Test
+    void pathTagAttached() {
+        metrics.disk(TMP, 1L, 1L);
+        assertEquals(TMP, registry.get("aiimage.tmpdisk.capacity").gauge().getId().getTag("path"));
+    }
+
+    @Test
+    void gaugeUpdatesOnLaterWrite() {
+        metrics.disk(TMP, 100L, 10L);
+        metrics.disk(TMP, 100L, 55L);
+        assertEquals(55.0, registry.get("aiimage.tmpdisk.used").tag("path", TMP).gauge().value(), 0.001);
+    }
+
+    @Test
+    void diskNamesFrozen() {
+        metrics.disk(TMP, 1L, 1L);
+        assertTrue(registry.getMeters().stream()
+                .anyMatch(m -> m.getId().getName().equals("aiimage.tmpdisk.capacity")));
+        assertTrue(registry.getMeters().stream()
+                .anyMatch(m -> m.getId().getName().equals("aiimage.tmpdisk.used")));
+    }
+
+    @Test
+    void measureCallDoesNotBlockOrThrow() {
+        // 多次写 gauge 不抛错（巡检每轮都调用），registry 为空也不影响
+        TaskObservabilityMetrics without = new TaskObservabilityMetrics("server-121", null);
+        without.disk(TMP, 1L, 1L);
+        metrics.disk(TMP, 1L, 1L);
+        metrics.disk(TMP + "/sub", 1L, 0L);
+    }
+}