diff --git a/desktop/src/workspace/local-workspace-agent-catalog.cjs b/desktop/src/workspace/local-workspace-agent-catalog.cjs
index 16ede48..9ac5525 100644
--- a/desktop/src/workspace/local-workspace-agent-catalog.cjs
+++ b/desktop/src/workspace/local-workspace-agent-catalog.cjs
@@ -334,7 +334,7 @@ class LocalWorkspaceAgentCatalog {
     }
     const since = this.indeterminateSince.get(agent.kind)
     if (previous?.available !== true || runtimeMissing || !Number.isFinite(nowMs)
-        || !Number.isFinite(since) || nowMs - since >= INDETERMINATE_PROBE_GRACE_MS
+        || !Number.isFinite(since) || nowMs < since || nowMs - since >= INDETERMINATE_PROBE_GRACE_MS
         || this.detectedIdentities.get(agent.kind) !== agentVerificationIdentity(agent, this.state().agentPreferences)
         || !agentVersionIdentified(agent) || !agentCompatible(agent)) return null
     return {
diff --git a/desktop/test/workspace/local-workspace-agent-catalog.test.cjs b/desktop/test/workspace/local-workspace-agent-catalog.test.cjs
index df82b6f..14b3495 100644
--- a/desktop/test/workspace/local-workspace-agent-catalog.test.cjs
+++ b/desktop/test/workspace/local-workspace-agent-catalog.test.cjs
@@ -1265,6 +1265,25 @@ test('an Agent that was never usable is not made available by an inconclusive pr
   assert.equal(agents()[0].available, false)
 })
 
+test('a clock rollback expires the inconclusive probe grace period', async () => {
+  const time = clock()
+  let probe = { state: 'ready', source: 'native-auth-status' }
+  const { agents, catalog } = fixture({
+    now: time.now,
+    detectAgents: async () => [OPENCLAW],
+    credentialState: async () => probe,
+  })
+  await catalog.refresh()
+  probe = { state: 'unknown', source: 'native-probe-failed' }
+  await catalog.refresh()
+  assert.equal(agents()[0].available, true)
+
+  time.advance(-1000)
+  await catalog.refresh()
+  assert.equal(agents()[0].available, false)
+  assert.equal(agents()[0].availabilitySource, 'native-probe-failed')
+})
+
 test('OpenClaw immediately becomes unavailable when its guarded runtime is unavailable', async () => {
   let probe = { state: 'ready', source: 'native-auth-status' }
   const { agents, catalog } = fixture({