perstack-ai · FL4TLiN3 · Mar 4, 2026 · Mar 4, 2026 · Mar 4, 2026 · Mar 4, 2026
diff --git a/.changeset/fix-default-model-tier.md b/.changeset/fix-default-model-tier.md
@@ -0,0 +1,11 @@
+---
+"@perstack/runtime": patch
+"@perstack/installer": patch
+"perstack": patch
+---
+
+Fix: Preserve `defaultModelTier` when resolving experts from API
+
+The `toRuntimeExpert` function in both runtime and installer packages was dropping the `defaultModelTier` field when converting API response experts to runtime Expert objects. This caused all API-fetched experts to ignore their configured model tier and fall back to the provider's highest-tier model (e.g., claude-opus-4-6 instead of claude-haiku-4-5 for `defaultModelTier: "low"`).
+
+Also fixed `configExpertToExpert` in the installer package which had the same omission when converting TOML config experts.
diff --git a/bun.lock b/bun.lock
diff --git a/packages/installer/package.json b/packages/installer/package.json
@@ -27,7 +27,7 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
-    "@perstack/api-client": "^0.0.57",
+    "@perstack/api-client": "^0.0.58",
     "@perstack/core": "workspace:*",
     "@perstack/perstack-toml": "workspace:*",
     "@perstack/skill-manager": "workspace:*"

diff --git a/packages/installer/src/expert-resolver.ts b/packages/installer/src/expert-resolver.ts
@@ -3,6 +3,7 @@ import {
   defaultPerstackApiBaseUrl,
   type Expert,
   expertSchema,
+  type ModelTier,
   type PerstackConfig,
   PerstackError,
   type RuntimeVersion,
@@ -47,6 +48,7 @@ export type PublishedExpertData = {
   >
   delegates?: string[]
   tags?: string[]
+  defaultModelTier?: ModelTier
 }
 
 export function toRuntimeExpert(key: string, expert: PublishedExpertData): Expert {
@@ -117,6 +119,7 @@ export function toRuntimeExpert(key: string, expert: PublishedExpertData): Exper
     skills,
     delegates: expert.delegates ?? [],
     tags: expert.tags ?? [],
+    defaultModelTier: expert.defaultModelTier,
   }
 }
 
@@ -136,6 +139,7 @@ export function configExpertToExpert(
     providerTools: configExpert.providerTools,
     providerSkills: configExpert.providerSkills,
     providerToolOptions: configExpert.providerToolOptions,
+    defaultModelTier: configExpert.defaultModelTier,
   })
 }
 

diff --git a/packages/runtime/package.json b/packages/runtime/package.json
@@ -37,7 +37,7 @@
     "@ai-sdk/openai": "^3.0.29",
     "@modelcontextprotocol/sdk": "^1.26.0",
     "@paralleldrive/cuid2": "^3.3.0",
-    "@perstack/api-client": "^0.0.57",
+    "@perstack/api-client": "^0.0.58",
     "@perstack/base": "0.0.78",
     "@perstack/core": "0.0.64",
     "ai": "^6.0.86",

diff --git a/packages/runtime/src/helpers/resolve-expert.test.ts b/packages/runtime/src/helpers/resolve-expert.test.ts
@@ -46,6 +46,7 @@ mock.module("@perstack/api-client", () => ({
                   skills: {},
                   delegates: [],
                   tags: [],
+                  defaultModelTier: "low",
                 },
               },
             },
@@ -136,6 +137,14 @@ describe("@perstack/runtime: resolveExpertToRun", () => {
     expect(result.key).toBe("published-expert")
   })
 
+  it("preserves defaultModelTier from API response", async () => {
+    const experts: Record<string, Expert> = {}
+    await resolveExpertToRun("remote-expert", experts, {
+      perstackApiBaseUrl: "https://api.test.com",
+    })
+    expect(experts["@remote-expert/delegate"].defaultModelTier).toBe("low")
+  })
+
   it("resolves delegate from already-populated experts without API call", async () => {
     const experts: Record<string, Expert> = {}
     await resolveExpertToRun("remote-expert", experts, {

diff --git a/packages/runtime/src/helpers/resolve-expert.ts b/packages/runtime/src/helpers/resolve-expert.ts
@@ -1,5 +1,11 @@
 import { createApiClient } from "@perstack/api-client"
-import { type Expert, PerstackError, type RuntimeVersion, type Skill } from "@perstack/core"
+import {
+  type Expert,
+  type ModelTier,
+  PerstackError,
+  type RuntimeVersion,
+  type Skill,
+} from "@perstack/core"
 
 export async function resolveExpertToRun(
   expertKey: string,
@@ -73,6 +79,7 @@ function toRuntimeExpert(
     >
     delegates?: string[]
     tags?: string[]
+    defaultModelTier?: ModelTier
   },
 ): Expert {
   const skills: Record<string, Skill> = Object.fromEntries(
@@ -142,5 +149,6 @@ function toRuntimeExpert(
     skills,
     delegates: expert.delegates ?? [],
     tags: expert.tags ?? [],
+    defaultModelTier: expert.defaultModelTier,
   }
 }
diff --git a/packages/studio/package.json b/packages/studio/package.json
@@ -27,7 +27,7 @@
     "typecheck": "tsc --noEmit"
   },
   "dependencies": {
-    "@perstack/api-client": "^0.0.57",
+    "@perstack/api-client": "^0.0.58",
     "@perstack/core": "workspace:*",
     "@perstack/installer": "workspace:*",
     "@perstack/perstack-toml": "workspace:*"