diff --git a/src/pages/MilestoneDetailPage.tsx b/src/pages/MilestoneDetailPage.tsx
index 96eebea..f5e27c5 100644
--- a/src/pages/MilestoneDetailPage.tsx
+++ b/src/pages/MilestoneDetailPage.tsx
@@ -45,6 +45,7 @@ export default function MilestoneDetailPage() {
   const [actionError, setActionError] = useState<string | null>(null)
   const [showCloseConfirm, setShowCloseConfirm] = useState(false)
   const [closeReason, setCloseReason] = useState('')
+  const [preflight, setPreflight] = useState<{ freeze?: { allowed: boolean; reason: string | null }; start?: { allowed: boolean; reason: string | null } } | null>(null)
 
   const fetchMilestone = () => {
     api.get<Milestone>(`/milestones/${id}`).then(({ data }) => {
@@ -55,11 +56,18 @@ export default function MilestoneDetailPage() {
           setProjectCode(proj.project_code || '')
         })
         api.get<ProjectMember[]>(`/projects/${data.project_id}/members`).then(({ data }) => setMembers(data)).catch(() => {})
+        fetchPreflight(data.project_id)
       }
     })
     api.get<MilestoneProgress>(`/milestones/${id}/progress`).then(({ data }) => setProgress(data)).catch(() => {})
   }
 
+  const fetchPreflight = (projectId: number) => {
+    api.get(`/projects/${projectId}/milestones/${id}/actions/preflight`)
+      .then(({ data }) => setPreflight(data))
+      .catch(() => setPreflight(null))
+  }
+
   useEffect(() => {
     fetchMilestone()
   }, [id])
@@ -113,6 +121,7 @@ export default function MilestoneDetailPage() {
       await api.post(`/projects/${project.id}/milestones/${milestone.id}/actions/${action}`, body ?? {})
       fetchMilestone()
       refreshMilestoneItems()
+      fetchPreflight(project.id)
     } catch (err: any) {
       const detail = err?.response?.data?.detail
       setActionError(typeof detail === 'string' ? detail : `${action} failed`)
@@ -164,22 +173,38 @@ export default function MilestoneDetailPage() {
         {!isTerminal && (
           <div style={{ display: 'flex', gap: 8, marginTop: 8, flexWrap: 'wrap', alignItems: 'center' }}>
             {msStatus === 'open' && (
-              <button
-                className="btn-primary"
-                disabled={actionLoading === 'freeze'}
-                onClick={handleFreeze}
-              >
-                {actionLoading === 'freeze' ? '⏳ Freezing...' : '🧊 Freeze'}
-              </button>
+              <span title={preflight?.freeze?.allowed === false ? preflight.freeze.reason ?? '' : ''}>
+                <button
+                  className="btn-primary"
+                  disabled={actionLoading === 'freeze' || preflight?.freeze?.allowed === false}
+                  onClick={handleFreeze}
+                  style={preflight?.freeze?.allowed === false ? { opacity: 0.5, cursor: 'not-allowed' } : {}}
+                >
+                  {actionLoading === 'freeze' ? '⏳ Freezing...' : '🧊 Freeze'}
+                </button>
+                {preflight?.freeze?.allowed === false && (
+                  <span className="text-dim" style={{ marginLeft: 8, fontSize: '0.85em' }}>
+                    ⚠ {preflight.freeze.reason}
+                  </span>
+                )}
+              </span>
             )}
             {msStatus === 'freeze' && (
-              <button
-                className="btn-primary"
-                disabled={actionLoading === 'start'}
-                onClick={handleStart}
-              >
-                {actionLoading === 'start' ? '⏳ Starting...' : '▶️ Start'}
-              </button>
+              <span title={preflight?.start?.allowed === false ? preflight.start.reason ?? '' : ''}>
+                <button
+                  className="btn-primary"
+                  disabled={actionLoading === 'start' || preflight?.start?.allowed === false}
+                  onClick={handleStart}
+                  style={preflight?.start?.allowed === false ? { opacity: 0.5, cursor: 'not-allowed' } : {}}
+                >
+                  {actionLoading === 'start' ? '⏳ Starting...' : '▶️ Start'}
+                </button>
+                {preflight?.start?.allowed === false && (
+                  <span className="text-dim" style={{ marginLeft: 8, fontSize: '0.85em' }}>
+                    ⚠ {preflight.start.reason}
+                  </span>
+                )}
+              </span>
             )}
             {(msStatus === 'open' || msStatus === 'freeze' || msStatus === 'undergoing') && (
               <>