diff --git a/backend/app/api/routes/observability.py b/backend/app/api/routes/observability.py
index a45c974..2134035 100644
--- a/backend/app/api/routes/observability.py
+++ b/backend/app/api/routes/observability.py
@@ -157,8 +157,18 @@ async def read_summary(
         problems=problems,
         flows={
             "total": len(names),
+            # What the engine will actually act on. Enabled is not enough:
+            # validation stops a flow as surely as quarantine does, and a
+            # paused one is holding its messages rather than running them.
             "running": len(
-                [n for n in names if controller.is_enabled(n) and n not in quarantined]
+                [
+                    n
+                    for n in names
+                    if controller.is_enabled(n)
+                    and n not in quarantined
+                    and n not in paused
+                    and n not in invalid
+                ]
             ),
             "paused": len(paused),
             "quarantined": len(quarantined),
diff --git a/backend/tests/api/routes/test_observability.py b/backend/tests/api/routes/test_observability.py
index 494541a..24ba915 100644
--- a/backend/tests/api/routes/test_observability.py
+++ b/backend/tests/api/routes/test_observability.py
@@ -91,6 +91,10 @@ def test_a_flow_that_cannot_run_makes_the_summary_degraded(
 
     controller = client.app.state.flow_controller
     before = controller.issues
+    before_flows = controller.store.list_flows
+    # The looping flow has to be one the store lists, otherwise "running"
+    # counts nothing either way and the assertion below proves nothing.
+    controller.store.list_flows = lambda: ["looping"]
     controller.issues = [
         ValidationIssue(
             code="cycle",
@@ -110,9 +114,11 @@ def test_a_flow_that_cannot_run_makes_the_summary_degraded(
         body = client.get(f"{PREFIX}/summary", headers=superuser_token_headers).json()
     finally:
         controller.issues = before
+        controller.store.list_flows = before_flows
 
     assert body["status"] == "degraded"
     assert body["flows"]["invalid"] == 1
+    assert body["flows"]["running"] == 0
     assert any("looping" in problem for problem in body["problems"])
     assert not any("broken" in problem for problem in body["problems"])
     assert not any("hooky" in problem for problem in body["problems"])
diff --git a/frontend/src/components/Health/HealthActivity.tsx b/frontend/src/components/Health/HealthActivity.tsx
index a409485..2695192 100644
--- a/frontend/src/components/Health/HealthActivity.tsx
+++ b/frontend/src/components/Health/HealthActivity.tsx
@@ -8,7 +8,7 @@ import { UplotChart } from "@/components/Common/UplotChart"
 import { useEngineEvents } from "@/components/Flow/liveStore"
 import { PANEL_SECTION } from "@/components/Flow/SidePanel"
 import { Button } from "@/components/ui/button"
-import { cn, si } from "@/lib/utils"
+import { cn, dur } from "@/lib/utils"
 import {
   ago,
   auditQueryOptions,
@@ -319,8 +319,8 @@ export function HealthActivity({ range }: { range: Range }) {
                   >
                     {run.status}
                   </span>
-                  <span className="w-16 shrink-0 text-right text-muted-foreground">
-                    {si(run.duration_ms)} ms
+                  <span className="w-20 shrink-0 whitespace-nowrap text-right text-muted-foreground">
+                    {dur(run.duration_ms)}
                   </span>
                   <span className="w-16 shrink-0 text-right text-xs text-muted-foreground">
                     {ago(run.started_at)}
diff --git a/frontend/src/components/Health/HealthOverview.tsx b/frontend/src/components/Health/HealthOverview.tsx
index 6870898..3dd8705 100644
--- a/frontend/src/components/Health/HealthOverview.tsx
+++ b/frontend/src/components/Health/HealthOverview.tsx
@@ -6,7 +6,7 @@ import { type Range, RangePicker } from "@/components/Common/RangePicker"
 import { Sparkline } from "@/components/Common/Sparkline"
 import { PANEL_SECTION } from "@/components/Flow/SidePanel"
 import { Badge } from "@/components/ui/badge"
-import { si } from "@/lib/utils"
+import { dur, si } from "@/lib/utils"
 import {
   ago,
   CARD,
@@ -117,16 +117,18 @@ export function HealthOverview({
           <Tile
             label="Flows running"
             value={`${summary?.flows.running ?? 0}/${summary?.flows.total ?? 0}`}
-            // Worst first: the engine gave up on a quarantined flow, a flow
-            // validation blocks never started, and a paused one is deliberate.
+            // Worst first, but all of them: a quarantine used to hide the
+            // flows validation blocks, so the tile disagreed with the count
+            // beside it. Zero and undefined both drop out of the filter.
             note={
-              summary?.flows.quarantined
-                ? `${summary.flows.quarantined} quarantined`
-                : summary?.flows.invalid
-                  ? `${summary.flows.invalid} cannot run`
-                  : summary?.flows.paused
-                    ? `${summary.flows.paused} paused`
-                    : "none paused"
+              [
+                summary?.flows.quarantined &&
+                  `${summary.flows.quarantined} quarantined`,
+                summary?.flows.invalid && `${summary.flows.invalid} cannot run`,
+                summary?.flows.paused && `${summary.flows.paused} paused`,
+              ]
+                .filter(Boolean)
+                .join(" · ") || "none paused"
             }
           />
           <Tile
@@ -149,8 +151,8 @@ export function HealthOverview({
           />
           <Tile
             label="Loop lag"
-            value={`${si(summary?.loop_lag.ewma ?? 0)} ms`}
-            note={`peak ${si(summary?.loop_lag.max_60s ?? 0)} ms in the last minute`}
+            value={dur(summary?.loop_lag.ewma ?? 0)}
+            note={`peak ${dur(summary?.loop_lag.max_60s ?? 0)} in the last minute`}
           />
         </div>
       </section>
@@ -208,10 +210,10 @@ export function HealthOverview({
                     )}
                   </td>
                   <td className="whitespace-nowrap px-3 py-2 text-center">
-                    {si(row.avg_ms)} ms
+                    {dur(row.avg_ms)}
                   </td>
                   <td className="whitespace-nowrap px-3 py-2 text-center">
-                    {si(row.avg_lag_ms)} ms
+                    {dur(row.avg_lag_ms)}
                   </td>
                   {/* The dot straddles the curve's right edge, so the cell
                       keeps a little room for the half that hangs out. */}
diff --git a/frontend/src/lib/utils.check.ts b/frontend/src/lib/utils.check.ts
index 08e27c9..a0c7d84 100644
--- a/frontend/src/lib/utils.check.ts
+++ b/frontend/src/lib/utils.check.ts
@@ -1,12 +1,13 @@
 /**
- * The cases `si` gets wrong when its rounding is written the obvious way.
+ * The cases `si` and `dur` get wrong when their rounding is written the
+ * obvious way.
  *
  * Run: `bun src/lib/utils.check.ts` (there is no unit runner; the suite in
  * `tests/` drives a running stack).
  */
 import assert from "node:assert/strict"
 
-import { si } from "./utils"
+import { dur, si } from "./utils"
 
 // Nothing is prefixed in the plain window: these are written with a unit after
 // them, and "400m ms" is not an improvement on "0.4 ms".
@@ -30,3 +31,22 @@ assert.notEqual(si(1234, 4), si(1235, 4))
 assert.equal(si(Number.NaN), "--")
 
 console.log("si: ok")
+
+// The unit follows the size, so no reading is left as a shortened number in
+// front of a unit the call site guessed.
+assert.equal(dur(0), "0 ms")
+assert.equal(dur(203.63), "204 ms")
+assert.equal(dur(1240), "1.24 s")
+assert.equal(dur(90_000), "1.5 min")
+
+// The plain window down to 0.01 ms, so a fast run keeps one unit across polls.
+assert.equal(dur(0.4), "0.4 ms")
+assert.equal(dur(0.0031, 4), "3.1 µs")
+
+// Rounding must not leave a value in the step it just rounded out of.
+assert.equal(dur(999.7), "1 s")
+assert.equal(dur(59_999), "1 min")
+
+assert.equal(dur(Number.NaN), "--")
+
+console.log("dur: ok")
diff --git a/frontend/src/lib/utils.ts b/frontend/src/lib/utils.ts
index a9d9260..acaca2a 100644
--- a/frontend/src/lib/utils.ts
+++ b/frontend/src/lib/utils.ts
@@ -41,3 +41,38 @@ export function si(value: number, digits = 3): string {
   const [factor, suffix] = SI_STEPS.find(([step]) => size >= step) ?? [1, ""]
   return `${Number((rounded / factor).toPrecision(digits))}${suffix}`
 }
+
+/** Floor, divisor and unit per step, largest first. */
+const DUR_STEPS: [number, number, string][] = [
+  [60_000, 60_000, "min"],
+  [1_000, 1_000, "s"],
+  [0.01, 1, "ms"],
+  [0, 1e-3, "µs"],
+]
+
+/**
+ * A duration in milliseconds at `digits` significant digits, carrying the unit
+ * it picked: 1240 → "1.24 s", 90000 → "1.5 min", 203.63 → "204 ms".
+ *
+ * Unlike `si` the unit is not the caller's to write. Shortening the number in
+ * front of a fixed " ms" gives "1.2k ms", which is a duration nobody reads —
+ * so the step moves the unit instead, and the value is rounded before that
+ * step is picked, so 999.7 reads "1 s" rather than "1000 ms".
+ *
+ * Below a millisecond it holds down to 0.01, which is `si`'s own plain-number
+ * window transposed onto units. That floor is deliberate: without it a tile
+ * polled every ten seconds flips between "400 µs" and "1.2 ms", and a reading
+ * that changes unit on every poll reads as broken rather than as fast.
+ */
+export function dur(ms: number, digits = 3): string {
+  if (!Number.isFinite(ms)) return "--"
+  const rounded = Number(ms.toPrecision(digits))
+  const size = Math.abs(rounded)
+  if (size === 0) return "0 ms"
+  const [, factor, unit] = DUR_STEPS.find(([floor]) => size >= floor) ?? [
+    0,
+    1,
+    "ms",
+  ]
+  return `${Number((rounded / factor).toPrecision(digits))} ${unit}`
+}