diff --git a/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts b/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
index 01c61ba6130..38280a0cdbd 100644
--- a/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
+++ b/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
@@ -544,5 +544,51 @@ describe("autorouter_presets", () => {
       const prefill = buildPresetPrefill(config, groupsOnly(["claude-sonnet-4.5"]));
       expect(prefill.complexityRouterConfig.tiers.SIMPLE).toEqual(["claude-sonnet-4.5"]);
     });
+
+    it("prefills the per-model litellm_params a preset carries in tier_model_configs", () => {
+      const config = {
+        tiers: { SIMPLE: ["gpt-5-nano"], MEDIUM: [], COMPLEX: [], REASONING: ["o3"] },
+        tier_model_configs: {
+          REASONING: [{ model_name: "o3", litellm_params: { reasoning_effort: "high" } }],
+        },
+        classifier_type: "heuristic" as const,
+        session_affinity: false,
+        deployment_affinity: true,
+      };
+      const prefill = buildPresetPrefill(config, groupsOnly(["gpt-5-nano", "o3"]));
+      expect(prefill.complexityRouterConfig.tier_model_params).toEqual({
+        REASONING: { o3: { reasoning_effort: "high" } },
+      });
+    });
+
+    // The params key on the preset's own spelling while the tier entry gets rewritten to the
+    // caller's. Leaving the key alone names a model the tier no longer holds, and
+    // serializeTierModelConfigs then drops the params on submit without saying so.
+    it("rewrites a param key to the same registered spelling its tier entry was rewritten to", () => {
+      const config = {
+        tiers: { SIMPLE: [], MEDIUM: [], COMPLEX: [], REASONING: ["claude-sonnet-4-5"] },
+        tier_model_configs: {
+          REASONING: [{ model_name: "claude-sonnet-4-5", litellm_params: { reasoning_effort: "high" } }],
+        },
+        classifier_type: "heuristic" as const,
+        session_affinity: false,
+        deployment_affinity: true,
+      };
+      const prefill = buildPresetPrefill(config, groupsOnly(["claude-sonnet-4.5"]));
+      expect(prefill.complexityRouterConfig.tier_model_params).toEqual({
+        REASONING: { "claude-sonnet-4.5": { reasoning_effort: "high" } },
+      });
+    });
+
+    it("leaves tier_model_params undefined for a preset that carries no per-model params", () => {
+      const config = {
+        tiers: { SIMPLE: ["gpt-5-nano"], MEDIUM: [], COMPLEX: [], REASONING: [] },
+        classifier_type: "heuristic" as const,
+        session_affinity: false,
+        deployment_affinity: true,
+      };
+      const prefill = buildPresetPrefill(config, groupsOnly(["gpt-5-nano"]));
+      expect(prefill.complexityRouterConfig.tier_model_params).toBeUndefined();
+    });
   });
 });
diff --git a/ui/litellm-dashboard/src/lib/autorouter_presets.ts b/ui/litellm-dashboard/src/lib/autorouter_presets.ts
index fd1ca7a13c2..68c4e8df79a 100644
--- a/ui/litellm-dashboard/src/lib/autorouter_presets.ts
+++ b/ui/litellm-dashboard/src/lib/autorouter_presets.ts
@@ -12,6 +12,7 @@ import {
 } from "@/components/add_model/ComplexityRouterConfig";
 import { KeywordTierRule } from "@/components/add_model/KeywordTierRules";
 import { hydrateKeywordTierRules } from "@/components/add_model/complexity_router_keywords";
+import { TierModelParamsByTier, hydrateTierModelParams } from "@/components/add_model/complexity_router_tiers";
 import { DEFAULT_ESCALATION_KEYWORDS } from "@/components/add_model/EscalationKeywords";
 import { DEFAULT_MATCH_THRESHOLD } from "@/components/add_model/SemanticKeywordMatching";
 import presetsRaw from "@/autorouter_presets.json";
@@ -244,6 +245,17 @@ export const buildPresetPrefill = (
 ): PresetPrefill => {
   const resolve = (model: string): string => resolveAvailableModel(model, availability) ?? model;
   const resolveTier = (models: string[]): string[] => models.map(resolve);
+  // Params key on the model name the preset spells while every tier entry is rewritten to the
+  // caller's registered spelling, so the keys have to be rewritten the same way. Otherwise
+  // serializeTierModelConfigs drops them for naming a model the tier no longer holds.
+  const resolveParamKeys = (params: TierModelParamsByTier | undefined): TierModelParamsByTier | undefined =>
+    params &&
+    Object.fromEntries(
+      Object.entries(params).map(([tier, byModel]) => [
+        tier,
+        Object.fromEntries(Object.entries(byModel).map(([model, litellmParams]) => [resolve(model), litellmParams])),
+      ]),
+    );
 
   return {
     complexityRouterConfig: {
@@ -253,6 +265,7 @@ export const buildPresetPrefill = (
         COMPLEX: resolveTier(config.tiers.COMPLEX),
         REASONING: resolveTier(config.tiers.REASONING),
       },
+      tier_model_params: resolveParamKeys(hydrateTierModelParams(config.tiers, config.tier_model_configs)),
       tier_labels: hydrateTierLabels(config.tier_labels),
       classifier_type: config.classifier_type,
       classifier_llm_config: config.classifier_llm_config && {