diff --git a/docs/plans/state.json b/docs/plans/state.json
index 250c344..956fdee 100644
--- a/docs/plans/state.json
+++ b/docs/plans/state.json
@@ -5710,6 +5710,17 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/gateway/handlers/handlers.test.ts + pnpm typecheck passing"
+    },
+    "dashboard-model-defaults-draft-preservation": {
+      "status": "completed",
+      "date": "2026-02-19",
+      "updated": "2026-02-19",
+      "summary": "Fixed Model Tier Defaults dropdown reset during periodic dashboard refresh by preserving unsaved form draft state (tiers, delegation, and background override settings) across Assistant Health rerenders until saved.",
+      "files_modified": [
+        "src/gateway/ui/pages/dashboard.js",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm typecheck passing"
     }
   },
   "overall_progress": {
diff --git a/src/gateway/ui/pages/dashboard.js b/src/gateway/ui/pages/dashboard.js
index 10d5822..0949fdd 100644
--- a/src/gateway/ui/pages/dashboard.js
+++ b/src/gateway/ui/pages/dashboard.js
@@ -13,6 +13,10 @@ let _lastBriefingTestAt = null;
 let _assistantSaveState = null;
 let _lastAssistantConfig = null;
 let _assistantManualOverrides = new Set();
+let _assistantModelDefaultsDraft = null;
+
+const MODEL_DEFAULT_TASK_KEYS = ['compaction', 'memory_extraction', 'classification', 'tool_summarisation', 'complex_reasoning'];
+const MODEL_DEFAULT_TIER_KEYS = ['default', 'fast', 'complex', 'local'];
 
 function formatUptime(seconds) {
   const d = Math.floor(seconds / 86400);
@@ -666,6 +670,7 @@ async function triggerDailyBriefingTest(jobName, statusEl) {
 function updateAssistantHealth(configData) {
   const el = document.getElementById('ops-assistant-health');
   if (!el) {return;}
+  _assistantModelDefaultsDraft = readAssistantModelDefaultsDraft(el) ?? _assistantModelDefaultsDraft;
 
   const snapshot = getAssistantStateSnapshot(configData);
 
@@ -692,7 +697,7 @@ function updateAssistantHealth(configData) {
     : 'not configured';
   const briefingReady = dailyBriefing && Boolean(briefingOutput?.channel && briefingOutput?.peer);
   const playbookLikeReady = announce || (memoryDaily && memoryProactive);
-  const modelTier = configData?.agents?.primary_tier ?? 'default';
+  const modelTier = _assistantModelDefaultsDraft?.primaryTier ?? configData?.agents?.primary_tier ?? 'default';
   const delegation = configData?.agents?.delegation ?? {};
   const backgroundModels = configData?.agents?.background_models ?? {};
   const tiers = configData?.models ?? {};
@@ -787,10 +792,10 @@ function updateAssistantHealth(configData) {
       <div class="text-sm font-semibold text-zinc-50 mb-3">Model Tier Defaults</div>
       <div class="text-sm text-zinc-500 mb-3">Tier provider/model definitions</div>
       <div class="space-y-3 mb-4">
-        ${['default', 'fast', 'complex', 'local'].map((tier) => {
+        ${MODEL_DEFAULT_TIER_KEYS.map((tier) => {
     const cfg = tiers?.[tier] ?? {};
-    const provider = cfg.provider ?? tiers?.default?.provider ?? 'openai';
-    const model = cfg.model ?? '';
+    const provider = _assistantModelDefaultsDraft?.tiers?.[tier]?.provider ?? cfg.provider ?? tiers?.default?.provider ?? 'openai';
+    const model = _assistantModelDefaultsDraft?.tiers?.[tier]?.model ?? cfg.model ?? '';
     return `
             <div class="p-3 border border-zinc-800 rounded-md bg-zinc-950/60">
               <div class="text-sm text-zinc-50 mb-2">${escapeHtml(tier)} tier</div>
@@ -822,8 +827,9 @@ function updateAssistantHealth(configData) {
       <div class="space-y-3">
         ${taskRows.map((task) => {
     const background = backgroundModels?.[task.key] ?? {};
-    const delegationTier = delegation?.[task.key] ?? 'fast';
-    const backgroundEnabled = Boolean(backgroundModels?.[task.key] && background?.enabled !== false);
+    const draftTask = _assistantModelDefaultsDraft?.tasks?.[task.key] ?? {};
+    const delegationTier = draftTask.delegationTier ?? delegation?.[task.key] ?? 'fast';
+    const backgroundEnabled = draftTask.backgroundEnabled ?? Boolean(backgroundModels?.[task.key] && background?.enabled !== false);
     return `
             <div class="p-3 border border-zinc-800 rounded-md bg-zinc-950/60">
               <div class="text-sm text-zinc-50 mb-2">${escapeHtml(task.label)}</div>
@@ -841,17 +847,21 @@ function updateAssistantHealth(configData) {
                 <label class="flex flex-col gap-1">
                   <span class="text-xs text-zinc-500">Provider</span>
                   <select id="assist-bg-${task.key}-provider" class="bg-zinc-950 text-zinc-50 border border-zinc-800 rounded-md px-2 py-1.5 text-sm focus:border-blue-500 outline-none">
-                    ${providerOption(background?.provider ?? tiers?.default?.provider ?? 'openai')}
+                    ${providerOption(draftTask.provider ?? background?.provider ?? tiers?.default?.provider ?? 'openai')}
                   </select>
                 </label>
                 <label class="flex flex-col gap-1">
                   <span class="text-xs text-zinc-500">Model</span>
-                  ${modelDataList(`assist-bg-${task.key}-model`, background?.provider ?? tiers?.default?.provider ?? 'openai', background?.model ?? '')}
+                  ${modelDataList(
+    `assist-bg-${task.key}-model`,
+    draftTask.provider ?? background?.provider ?? tiers?.default?.provider ?? 'openai',
+    draftTask.model ?? background?.model ?? '',
+  )}
                 </label>
                 <label class="flex flex-col gap-1">
                   <span class="text-xs text-zinc-500">Fallback tier</span>
                   <select id="assist-bg-${task.key}-fallback" class="bg-zinc-950 text-zinc-50 border border-zinc-800 rounded-md px-2 py-1.5 text-sm focus:border-blue-500 outline-none">
-                    ${tierOption(background?.fallback_tier ?? 'fast')}
+                    ${tierOption(draftTask.fallbackTier ?? background?.fallback_tier ?? 'fast')}
                   </select>
                 </label>
               </div>
@@ -928,7 +938,7 @@ function updateAssistantHealth(configData) {
     });
   }
 
-  const taskRowsForModels = ['compaction', 'memory_extraction', 'classification', 'tool_summarisation', 'complex_reasoning'];
+  const taskRowsForModels = MODEL_DEFAULT_TASK_KEYS;
   for (const task of taskRowsForModels) {
     const providerSelect = el.querySelector(`#assist-bg-${task}-provider`);
     if (!providerSelect) {continue;}
@@ -996,11 +1006,11 @@ function updateAssistantHealth(configData) {
         };
         _assistantManualOverrides.add('automation.daily_briefing.enabled');
       } else if (action === 'save-model-defaults') {
-        const tasks = ['compaction', 'memory_extraction', 'classification', 'tool_summarisation', 'complex_reasoning'];
+        const tasks = MODEL_DEFAULT_TASK_KEYS;
         patches = {
           'agents.primary_tier': (el.querySelector('#assist-primary-tier')?.value ?? 'default'),
         };
-        const tiers = ['default', 'fast', 'complex', 'local'];
+        const tiers = MODEL_DEFAULT_TIER_KEYS;
         for (const tier of tiers) {
           const provider = (el.querySelector(`#assist-tier-${tier}-provider`)?.value ?? '').trim();
           const model = (el.querySelector(`#assist-tier-${tier}-model`)?.value ?? '').trim();
@@ -1033,7 +1043,12 @@ function updateAssistantHealth(configData) {
         }
       }
       if (!patches) {return;}
-      await applyAssistantPatch(patches, statusEl);
+      const patchResult = await applyAssistantPatch(patches, statusEl);
+      if (action === 'save-model-defaults' && patchResult.applied.length > 0 && patchResult.rejected.length === 0) {
+        _assistantModelDefaultsDraft = null;
+      } else if (action === 'save-model-defaults') {
+        _assistantModelDefaultsDraft = readAssistantModelDefaultsDraft(el) ?? _assistantModelDefaultsDraft;
+      }
       // Force immediate refresh of slow sections after applying.
       const refreshed = await fetchSlow(_dashboardClient);
       if (refreshed) {
@@ -1052,6 +1067,38 @@ function updateAssistantHealth(configData) {
   });
 }
 
+function readAssistantModelDefaultsDraft(rootEl) {
+  const primaryTier = rootEl.querySelector('#assist-primary-tier')?.value;
+  if (!primaryTier) {
+    return null;
+  }
+
+  const tiers = {};
+  for (const tier of MODEL_DEFAULT_TIER_KEYS) {
+    const provider = (rootEl.querySelector(`#assist-tier-${tier}-provider`)?.value ?? '').trim();
+    const model = (rootEl.querySelector(`#assist-tier-${tier}-model`)?.value ?? '').trim();
+    if (!provider && !model) {continue;}
+    tiers[tier] = { provider, model };
+  }
+
+  const tasks = {};
+  for (const task of MODEL_DEFAULT_TASK_KEYS) {
+    tasks[task] = {
+      delegationTier: rootEl.querySelector(`#assist-delegation-${task}`)?.value ?? 'fast',
+      backgroundEnabled: Boolean(rootEl.querySelector(`#assist-bg-${task}-enabled`)?.checked),
+      provider: (rootEl.querySelector(`#assist-bg-${task}-provider`)?.value ?? '').trim(),
+      model: (rootEl.querySelector(`#assist-bg-${task}-model`)?.value ?? '').trim(),
+      fallbackTier: rootEl.querySelector(`#assist-bg-${task}-fallback`)?.value ?? 'fast',
+    };
+  }
+
+  return {
+    primaryTier,
+    tiers,
+    tasks,
+  };
+}
+
 function _updateChannels(channelsData) {
   const el = document.getElementById('ops-channels');
   if (!el) {return;}
@@ -1248,5 +1295,6 @@ export const DashboardPage = {
     _assistantSaveState = null;
     _lastAssistantConfig = null;
     _assistantManualOverrides = new Set();
+    _assistantModelDefaultsDraft = null;
   },
 };