fix(core): resolve hidden title models internally

Move copilot utility-model preference out of core selection into the
github-copilot plugin by exposing catalog.model.small set/get/remove on
the transform draft.

packages/core/src/catalog.ts

@@ -1,7 +1,7 @@
 export * as Catalog from "./catalog"
 
 import { makeLocationNode } from "./effect/app-node"
-import { Array, Context, Effect, Layer, Option, Order, pipe } from "effect"
+import { Array, Context, Effect, Layer, Order, pipe } from "effect"
 import { Catalog } from "@opencode-ai/schema/catalog"
 import { ModelV2 } from "./model"
 import { ProviderV2 } from "./provider"
@@ -21,6 +21,7 @@ export const Event = Catalog.Event
 type Data = {
   providers: Map<ProviderV2.ID, ProviderRecord>
   defaultModel?: DefaultModel
+  smallModels: Map<ProviderV2.ID, ModelV2.ID>
 }
 
 export type Draft = {
@@ -38,6 +39,11 @@ export type Draft = {
       get: () => DefaultModel | undefined
       set: (providerID: ProviderV2.ID, modelID: ModelV2.ID) => void
     }
+    small: {
+      get: (providerID: ProviderV2.ID) => ModelV2.ID | undefined
+      set: (providerID: ProviderV2.ID, modelID: ModelV2.ID) => void
+      remove: (providerID: ProviderV2.ID) => void
+    }
   }
 }
 
@@ -83,7 +89,7 @@ const layer = Layer.effect(
 
     const state = State.create<Data, Draft>({
       name: "catalog",
-      initial: () => ({ providers: new Map() }),
+      initial: () => ({ providers: new Map(), smallModels: new Map() }),
       draft: (draft) => {
         const result: Draft = {
           provider: {
@@ -131,6 +137,15 @@ const layer = Layer.effect(
                 draft.defaultModel = { providerID, modelID }
               },
             },
+            small: {
+              get: (providerID) => draft.smallModels.get(providerID),
+              set: (providerID, modelID) => {
+                draft.smallModels.set(providerID, modelID)
+              },
+              remove: (providerID) => {
+                draft.smallModels.delete(providerID)
+              },
+            },
           },
         }
         return result
@@ -217,48 +232,50 @@ const layer = Layer.effect(
             return
           }
 
-          if (providerID === ProviderV2.ID.opencode) {
-            const gpt5Nano = record.models.get(ModelV2.ID.make("gpt-5-nano"))
-            if (gpt5Nano?.enabled && gpt5Nano.status === "active") return projectModel(gpt5Nano, provider)
+          // Plugin transforms may pin a small model (for example picker-disabled utility models).
+          const configured = state.get().smallModels.get(providerID)
+          if (configured) {
+            const model = record.models.get(configured)
+            if (model?.status === "active") return projectModel(model, provider)
           }
 
-          const candidates = pipe(
+          const priority = providerID.startsWith("opencode")
+            ? ["gpt-nano"]
+            : providerID.startsWith("github-copilot")
+              ? ["gpt-mini", ...SMALL_MODEL_FAMILY_PRIORITY]
+              : SMALL_MODEL_FAMILY_PRIORITY
+
+          const models = pipe(
             Array.fromIterable(record.models.values()),
-            Array.filter(
-              (model) =>
-                model.providerID === providerID &&
-                model.enabled &&
-                model.status === "active" &&
-                model.capabilities.input.some((item) => item.startsWith("text")) &&
-                model.capabilities.output.some((item) => item.startsWith("text")),
-            ),
-            Array.map((model) => ({
-              model,
-              cost: model.cost[0] ? model.cost[0].input + model.cost[0].output : 999,
-              age: (Date.now() - model.time.released) / (1000 * 60 * 60 * 24 * 30),
-              small: SMALL_MODEL_RE.test(`${model.id} ${model.family ?? ""} ${model.name}`.toLowerCase()),
-            })),
-            Array.filter((item) => item.cost > 0 && item.age <= 18),
+            Array.filter((model) => model.enabled && model.status === "active"),
+            Array.sortWith((model) => model.id, Order.flip(Order.String)),
+            Array.sortWith((model) => model.time.released, Order.flip(Order.Number)),
           )
 
-          const pick = (items: typeof candidates) => {
-            const maxCost = Math.max(...items.map((item) => item.cost), 0.01)
-            const maxAge = Math.max(...items.map((item) => item.age), 0.01)
-            return pipe(
-              items,
-              Array.sortWith((item) => (item.cost / maxCost) * 0.8 + (item.age / maxAge) * 0.2, Order.Number),
-              Array.map((item) => projectModel(item.model, provider)),
-              Array.head,
-            )
+          for (const family of priority) {
+            const candidates = models.filter((model) => model.family === family)
+            if (providerID === ProviderV2.ID.amazonBedrock) {
+              const crossRegionPrefixes = ["global.", "us.", "eu."]
+              const globalMatch = candidates.find((model) => model.id.startsWith("global."))
+              if (globalMatch) return projectModel(globalMatch, provider)
+
+              const region = typeof provider.settings?.region === "string" ? provider.settings.region : undefined
+              if (region) {
+                const regionPrefix = region.split("-")[0]
+                if (regionPrefix === "us" || regionPrefix === "eu") {
+                  const regionalMatch = candidates.find((model) => model.id.startsWith(`${regionPrefix}.`))
+                  if (regionalMatch) return projectModel(regionalMatch, provider)
+                }
+              }
+
+              const unprefixed = candidates.find(
+                (model) => !crossRegionPrefixes.some((prefix) => model.id.startsWith(prefix)),
+              )
+              if (unprefixed) return projectModel(unprefixed, provider)
+              continue
+            }
+            if (candidates[0]) return projectModel(candidates[0], provider)
           }
-
-          return Option.getOrUndefined(
-            pipe(
-              candidates,
-              Array.filter((item) => item.small),
-              (items) => (items.length > 0 ? pick(items) : pick(candidates)),
-            ),
-          )
         }),
       },
     }
@@ -267,6 +284,6 @@ const layer = Layer.effect(
   }),
 )
 
-const SMALL_MODEL_RE = /\b(nano|flash|lite|mini|haiku|small|fast)\b/
+const SMALL_MODEL_FAMILY_PRIORITY = ["gemini-flash", "gpt-nano", "claude-haiku"]
 
 export const node = makeLocationNode({ service: Service, layer, deps: [EventV2.node, Integration.node] })

packages/core/src/plugin/host.ts

@@ -148,6 +148,12 @@ export const make = Effect.fn("PluginHost.make")(function* (plugin: PluginV2.Int
                 set: (providerID, modelID) =>
                   draft.model.default.set(ProviderV2.ID.make(providerID), ModelV2.ID.make(modelID)),
               },
+              small: {
+                get: (providerID) => draft.model.small.get(ProviderV2.ID.make(providerID)),
+                set: (providerID, modelID) =>
+                  draft.model.small.set(ProviderV2.ID.make(providerID), ModelV2.ID.make(modelID)),
+                remove: (providerID) => draft.model.small.remove(ProviderV2.ID.make(providerID)),
+              },
             },
           })
         }),

packages/core/src/plugin/provider/github-copilot.ts

@@ -119,6 +119,8 @@ function shouldUseResponses(modelID: string) {
   return Number(match[1]) >= 5 && !modelID.startsWith("gpt-5-mini")
 }
 
+const UTILITY_MODELS = ["gpt-5.4-nano", "gpt-4.1", "gpt-4o", "gpt-4o-mini"]
+
 export const GithubCopilotPlugin = define({
   id: "opencode.provider.github-copilot",
   effect: Effect.fn(function* (ctx) {
@@ -192,6 +194,13 @@ export const GithubCopilotPlugin = define({
           model.enabled = false
         })
       }
+      // GitHub exposes utility models for title generation without including them in the picker.
+      const utility = UTILITY_MODELS.map((id) => ModelV2.ID.make(id)).find((id) => {
+        const model = evt.model.get(item.provider.id, id)
+        return model?.status === "active"
+      })
+      if (utility) evt.model.small.set(item.provider.id, utility)
+      else evt.model.small.remove(item.provider.id)
     })
     const refresh = () => loading.withPermit(load().pipe(Effect.andThen(ctx.catalog.reload())))
     yield* events.subscribe(Integration.Event.ConnectionUpdated).pipe(

packages/core/src/session/runner/model.ts

@@ -88,12 +88,23 @@ export interface Resolved {
 
 export interface Interface {
   readonly resolve: (session: SessionSchema.Info) => Effect.Effect<Resolved, Error>
+  readonly resolveCatalogModel: (
+    session: SessionSchema.Info,
+    model: ModelV2.Info,
+  ) => Effect.Effect<Resolved, Error>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/v2/SessionRunnerModel") {}
 
 /** Test or embedding seam for supplying a model resolver directly. */
-export const layerWith = (resolve: Interface["resolve"]) => Layer.succeed(Service, Service.of({ resolve }))
+export const layerWith = (
+  resolve: Interface["resolve"],
+  resolveCatalogModel: Interface["resolveCatalogModel"] = (session, model) =>
+    resolve({
+      ...session,
+      model: ModelV2.Ref.make({ id: model.id, providerID: model.providerID }),
+    }),
+) => Layer.succeed(Service, Service.of({ resolve, resolveCatalogModel }))
 
 /** Builds a Resolved whose catalog identity mirrors the route model. Test or embedding seam. */
 export const resolved = (model: Model, variant?: ModelV2.VariantID, cost: ModelV2.Info["cost"] = []): Resolved => ({
@@ -307,7 +318,43 @@ const layer = Layer.effect(
     const integrations = yield* Integration.Service
     const npm = yield* Npm.Service
     const aisdk = yield* AISDK.Service
+    const resolveCatalogModel = Effect.fn("SessionRunnerModel.resolveCatalogModel")(function* (
+      session: SessionSchema.Info,
+      selected: ModelV2.Info,
+      variant?: ModelV2.VariantID,
+    ) {
+      const provider = yield* catalog.provider.get(selected.providerID)
+      const connection = yield* integrations.connection.active(
+        provider?.integrationID ?? Integration.ID.make(selected.providerID),
+      )
+      const model = yield* resolve(
+        {
+          ...session,
+          model: ModelV2.Ref.make({
+            id: selected.id,
+            providerID: selected.providerID,
+            ...(variant === undefined ? {} : { variant }),
+          }),
+        },
+        selected,
+        connection ? yield* integrations.connection.resolve(connection) : undefined,
+        {
+          loadPackage: (specifier) => ProviderV2.loadPackage(specifier, npm),
+          loadAISDK: (model) => aisdk.model(model),
+        },
+      )
+      return {
+        model,
+        ref: ModelV2.Ref.make({
+          id: selected.id,
+          providerID: selected.providerID,
+          ...(variant === undefined ? {} : { variant }),
+        }),
+        cost: selected.cost,
+      }
+    })
     return Service.of({
+      resolveCatalogModel,
       resolve: Effect.fn("SessionRunnerModel.resolve")(function* (session) {
         // Location plugins populate and filter the catalog asynchronously during layer startup.
         const defaultModel = session.model ? undefined : yield* catalog.model.default()
@@ -324,28 +371,7 @@ const layer = Layer.effect(
             modelID: session.model.id,
           })
         if (!selected) return yield* new ModelNotSelectedError({ sessionID: session.id })
-        const provider = yield* catalog.provider.get(selected.providerID)
-        const connection = yield* integrations.connection.active(
-          provider?.integrationID ?? Integration.ID.make(selected.providerID),
-        )
-        const model = yield* resolve(
-          session,
-          selected,
-          connection ? yield* integrations.connection.resolve(connection) : undefined,
-          {
-            loadPackage: (specifier) => ProviderV2.loadPackage(specifier, npm),
-            loadAISDK: (model) => aisdk.model(model),
-          },
-        )
-        return {
-          model,
-          ref: ModelV2.Ref.make({
-            id: selected.id,
-            providerID: selected.providerID,
-            ...(session.model?.variant === undefined ? {} : { variant: session.model.variant }),
-          }),
-          cost: selected.cost,
-        }
+        return yield* resolveCatalogModel(session, selected, session.model?.variant)
       }),
     })
   }),

packages/core/src/session/title.ts

@@ -3,6 +3,7 @@ export * as SessionTitle from "./title"
 import { LLM, LLMClient, LLMError, LLMEvent, Message, type LLMRequest } from "@opencode-ai/llm"
 import { Context, DateTime, Effect, Layer, Stream } from "effect"
 import { AgentV2 } from "../agent"
+import { Catalog } from "../catalog"
 import { Database } from "../database/database"
 import { EventV2 } from "../event"
 import { makeLocationNode } from "../effect/app-node"
@@ -21,6 +22,7 @@ type Dependencies = {
   }
   readonly agents: AgentV2.Interface
   readonly models: SessionRunnerModel.Interface
+  readonly catalog: Catalog.Interface
 }
 
 export interface Interface {
@@ -45,7 +47,14 @@ const make = (dependencies: Dependencies) => {
     const resolved = yield* (
       agent.model
         ? dependencies.models.resolve({ ...session, model: agent.model })
-        : dependencies.models.resolve(session)
+        : Effect.gen(function* () {
+            const providerID = session.model?.providerID ?? (yield* dependencies.catalog.model.default())?.providerID
+            const small = providerID ? yield* dependencies.catalog.model.small(providerID) : undefined
+            if (!small) return yield* dependencies.models.resolve(session)
+            return yield* dependencies.models
+              .resolveCatalogModel(session, small)
+              .pipe(Effect.catch(() => dependencies.models.resolve(session)))
+          })
     ).pipe(Effect.catch(() => Effect.succeed(undefined)))
     if (!resolved) return
     const chunks: string[] = []
@@ -90,8 +99,9 @@ export const layer = Layer.effect(
     const llm = yield* LLMClient.Service
     const agents = yield* AgentV2.Service
     const models = yield* SessionRunnerModel.Service
+    const catalog = yield* Catalog.Service
     const database = yield* Database.Service
-    const title = make({ events, llm, agents, models })
+    const title = make({ events, llm, agents, models, catalog })
     return Service.of({
       generateForFirstPrompt: (session) => title.generateForFirstPrompt(database.db, session),
     })
@@ -101,5 +111,5 @@ export const layer = Layer.effect(
 export const node = makeLocationNode({
   service: Service,
   layer,
-  deps: [EventV2.node, llmClient, AgentV2.node, SessionRunnerModel.node, Database.node],
+  deps: [EventV2.node, llmClient, AgentV2.node, SessionRunnerModel.node, Catalog.node, Database.node],
 })

packages/core/test/catalog.test.ts

@@ -290,45 +290,216 @@ describe("CatalogV2", () => {
     }),
   )
 
-  it.effect("small model prefers small keyword candidates before cost scoring", () =>
+  it.effect("small model selects the latest model in the preferred family", () =>
     Effect.gen(function* () {
       const catalog = yield* Catalog.Service
       const providerID = ProviderV2.ID.make("test")
       yield* catalog.transform((catalog) => {
         catalog.provider.update(providerID, () => {})
-        catalog.model.update(providerID, ModelV2.ID.make("cheap-large"), (model) => {
-          model.capabilities.input = ["text"]
-          model.capabilities.output = ["text"]
-          model.cost = [
-            {
-              input: Money.USDPerMillionTokens.make(1),
-              output: Money.USDPerMillionTokens.make(1),
-              cache: {
-                read: Money.USDPerMillionTokens.zero,
-                write: Money.USDPerMillionTokens.zero,
-              },
-            },
-          ]
+        catalog.model.update(providerID, ModelV2.ID.make("old-flash"), (model) => {
+          model.family = ModelV2.Family.make("gemini-flash")
+          model.time.released = Date.now() - 1000
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("new-flash"), (model) => {
+          model.family = ModelV2.Family.make("gemini-flash")
           model.time.released = Date.now()
         })
-        catalog.model.update(providerID, ModelV2.ID.make("expensive-mini"), (model) => {
-          model.capabilities.input = ["text"]
-          model.capabilities.output = ["text"]
-          model.cost = [
-            {
-              input: Money.USDPerMillionTokens.make(10),
-              output: Money.USDPerMillionTokens.make(10),
-              cache: {
-                read: Money.USDPerMillionTokens.zero,
-                write: Money.USDPerMillionTokens.zero,
-              },
-            },
-          ]
+        catalog.model.update(providerID, ModelV2.ID.make("newer-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now() + 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("new-flash"))
+    }),
+  )
+
+  it.effect("small model matches exact model families", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.make("test")
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("glm-flash"), (model) => {
+          model.family = ModelV2.Family.make("glm-flash")
+          model.time.released = Date.now() + 1000
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
           model.time.released = Date.now()
         })
       })
 
-      expect((yield* catalog.model.small(providerID))?.id).toMatch("expensive-mini")
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("claude-haiku"))
+    }),
+  )
+
+  it.effect("small model ignores model IDs without family metadata", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.make("test")
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-5-nano"), (model) => {
+          model.time.released = Date.now()
+        })
+      })
+
+      expect(yield* catalog.model.small(providerID)).toBeUndefined()
+    }),
+  )
+
+  it.effect("small model prefers gpt-nano family for opencode providers", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.opencode
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("old-nano"), (model) => {
+          model.family = ModelV2.Family.make("gpt-nano")
+          model.time.released = Date.now() - 1000
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("new-nano"), (model) => {
+          model.family = ModelV2.Family.make("gpt-nano")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("flash"), (model) => {
+          model.family = ModelV2.Family.make("gemini-flash")
+          model.time.released = Date.now() + 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("new-nano"))
+    }),
+  )
+
+  it.effect("small model prefers gpt-mini family for github-copilot providers", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.githubCopilot
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("flash"), (model) => {
+          model.family = ModelV2.Family.make("gemini-flash")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("mini"), (model) => {
+          model.family = ModelV2.Family.make("gpt-mini")
+          model.time.released = Date.now() - 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("mini"))
+    }),
+  )
+
+  it.effect("small model prefers a plugin-configured small model override", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.githubCopilot
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("mini"), (model) => {
+          model.family = ModelV2.Family.make("gpt-mini")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-5.4-nano"), (model) => {
+          model.enabled = false
+          model.time.released = Date.now() - 2000
+        })
+        catalog.model.small.set(providerID, ModelV2.ID.make("gpt-5.4-nano"))
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("gpt-5.4-nano"))
+      expect((yield* catalog.model.available()).some((model) => model.id === ModelV2.ID.make("gpt-5.4-nano"))).toBe(
+        false,
+      )
+    }),
+  )
+
+  it.effect("small model prefers global bedrock deployments before regional ones", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.amazonBedrock
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, (provider) => {
+          provider.settings = { region: "us-west-2" }
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("us.claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("global.claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now() - 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("global.claude-haiku"))
+    }),
+  )
+
+  it.effect("small model prefers regional bedrock deployments when global is missing", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.amazonBedrock
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, (provider) => {
+          provider.settings = { region: "us-west-2" }
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("us.claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now() - 1000
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("eu.claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now() + 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("us.claude-haiku"))
+    }),
+  )
+
+  it.effect("small model prefers unprefixed bedrock deployments when region prefixes are missing", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.amazonBedrock
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, (provider) => {
+          provider.settings = { region: "ap-northeast-1" }
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("eu.claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now()
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("claude-haiku"), (model) => {
+          model.family = ModelV2.Family.make("claude-haiku")
+          model.time.released = Date.now() - 1000
+        })
+      })
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("claude-haiku"))
+    }),
+  )
+
+  it.effect("small model skips inferred models for Azure providers", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      for (const providerID of [ProviderV2.ID.azure, ProviderV2.ID.make("azure-cognitive-services")]) {
+        yield* catalog.transform((catalog) => {
+          catalog.provider.update(providerID, () => {})
+          catalog.model.update(providerID, ModelV2.ID.make("small"), (model) => {
+            model.family = ModelV2.Family.make("gemini-flash")
+            model.time.released = Date.now()
+          })
+        })
+        expect(yield* catalog.model.small(providerID)).toBeUndefined()
+      }
     }),
   )
 })

packages/core/test/plugin/host.ts

@@ -178,6 +178,12 @@ export function catalogHost(catalog: Catalog.Interface): PluginContext["catalog"
               set: (providerID, modelID) =>
                 draft.model.default.set(ProviderV2.ID.make(providerID), ModelV2.ID.make(modelID)),
             },
+            small: {
+              get: (providerID) => draft.model.small.get(ProviderV2.ID.make(providerID)),
+              set: (providerID, modelID) =>
+                draft.model.small.set(ProviderV2.ID.make(providerID), ModelV2.ID.make(modelID)),
+              remove: (providerID) => draft.model.small.remove(ProviderV2.ID.make(providerID)),
+            },
           },
         }),
       ),

packages/core/test/plugin/provider-github-copilot.test.ts

@@ -289,6 +289,28 @@ describe("GithubCopilotPlugin", () => {
     }),
   )
 
+  it.effect("pins picker-hidden utility models for internal small-model work", () =>
+    Effect.gen(function* () {
+      const catalog = yield* Catalog.Service
+      const providerID = ProviderV2.ID.githubCopilot
+      yield* catalog.transform((catalog) => {
+        catalog.provider.update(providerID, () => {})
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-4.1"), (model) => {
+          model.enabled = false
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-5.4-nano"), (model) => {
+          model.enabled = false
+        })
+      })
+      yield* addPlugin()
+
+      expect((yield* catalog.model.small(providerID))?.id).toBe(ModelV2.ID.make("gpt-5.4-nano"))
+      expect((yield* catalog.model.available()).some((model) => model.id === ModelV2.ID.make("gpt-5.4-nano"))).toBe(
+        false,
+      )
+    }),
+  )
+
   it.effect("does not disable gpt-5-chat-latest for non-Copilot providers", () =>
     Effect.gen(function* () {
       const catalog = yield* Catalog.Service

packages/core/test/plugin/provider-opencode.test.ts

@@ -481,30 +481,38 @@ describe("OpencodePlugin", () => {
     ),
   )
 
-  it.effect("prefers gpt-5-nano as the opencode small model", () =>
+  it.effect("prefers the newest gpt-nano family model for opencode", () =>
     Effect.gen(function* () {
       const catalog = yield* Catalog.Service
       const providerID = ProviderV2.ID.opencode
 
       yield* catalog.transform((catalog) => {
         catalog.provider.update(providerID, () => {})
-        catalog.model.update(providerID, ModelV2.ID.make("cheap-mini"), (model) => {
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-5-nano"), (model) => {
+          model.family = ModelV2.Family.make("gpt-nano")
+          model.capabilities.input = ["text"]
+          model.capabilities.output = ["text"]
+          model.cost = [...cost(10, 10)]
+          model.time.released = Date.now() - 1000
+        })
+        catalog.model.update(providerID, ModelV2.ID.make("gpt-5.4-nano"), (model) => {
+          model.family = ModelV2.Family.make("gpt-nano")
           model.capabilities.input = ["text"]
           model.capabilities.output = ["text"]
           model.cost = [...cost(1, 1)]
           model.time.released = Date.now()
         })
-        catalog.model.update(providerID, ModelV2.ID.make("gpt-5-nano"), (model) => {
+        catalog.model.update(providerID, ModelV2.ID.make("cheap-mini"), (model) => {
           model.capabilities.input = ["text"]
           model.capabilities.output = ["text"]
-          model.cost = [...cost(10, 10)]
-          model.time.released = Date.now()
+          model.cost = [...cost(1, 1)]
+          model.time.released = Date.now() + 1000
         })
       })
 
       const selected = yield* catalog.model.small(providerID)
 
-      expect(selected?.id).toBe(ModelV2.ID.make("gpt-5-nano"))
+      expect(selected?.id).toBe(ModelV2.ID.make("gpt-5.4-nano"))
     }),
   )
 })

packages/core/test/session-title.test.ts

@@ -2,11 +2,14 @@ import { expect } from "bun:test"
 import { LLMClient, LLMEvent, Model, type LLMRequest } from "@opencode-ai/llm"
 import { OpenAIChat } from "@opencode-ai/llm/protocols"
 import { AgentV2 } from "@opencode-ai/core/agent"
+import { Catalog } from "@opencode-ai/core/catalog"
 import { Database } from "@opencode-ai/core/database/database"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { llmClient } from "@opencode-ai/core/effect/app-node-platform"
 import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { EventV2 } from "@opencode-ai/core/event"
+import { ModelV2 } from "@opencode-ai/core/model"
+import { ProviderV2 } from "@opencode-ai/core/provider"
 import { SessionEvent } from "@opencode-ai/core/session/event"
 import { SessionMessage } from "@opencode-ai/core/session/message"
 import { SessionProjector } from "@opencode-ai/core/session/projector"
@@ -18,10 +21,12 @@ import { SessionV2 } from "@opencode-ai/core/session"
 import { Project } from "@opencode-ai/core/project"
 import { ProjectTable } from "@opencode-ai/core/project/sql"
 import { AbsolutePath } from "@opencode-ai/core/schema"
-import { DateTime, Effect, Layer, Stream } from "effect"
+import { Effect, Layer, Stream } from "effect"
 import { testEffect } from "./lib/effect"
 
 let requests: LLMRequest[] = []
+let resolvedModels: Array<{ id: string; provider: string } | undefined> = []
+let failSmallResolve = false
 const model = Model.make({
   id: "title-model",
   provider: "test",
@@ -36,7 +41,35 @@ const client = Layer.mock(LLMClient.Service)({
   generate: () => Effect.die("unused"),
 })
 const models = Layer.mock(SessionRunnerModel.Service)({
-  resolve: () => Effect.succeed(SessionRunnerModel.resolved(model)),
+  resolve: (session) => {
+    resolvedModels.push(session.model ? { id: session.model.id, provider: session.model.providerID } : undefined)
+    if (failSmallResolve && session.model?.id === "mini") {
+      return Effect.fail(new Error("small unavailable") as never)
+    }
+    const selected = session.model
+      ? Model.make({
+          id: session.model.id,
+          provider: session.model.providerID,
+          route: OpenAIChat.route.with({ limits: { context: 10_000, output: 1_000 } }),
+        })
+      : model
+    return Effect.succeed(SessionRunnerModel.resolved(selected))
+  },
+  resolveCatalogModel: (session, selected) => {
+    resolvedModels.push({ id: selected.id, provider: selected.providerID })
+    if (failSmallResolve && selected.id === ModelV2.ID.make("mini")) {
+      return Effect.fail(new Error("small unavailable") as never)
+    }
+    return Effect.succeed(
+      SessionRunnerModel.resolved(
+        Model.make({
+          id: selected.id,
+          provider: selected.providerID,
+          route: OpenAIChat.route.with({ limits: { context: 10_000, output: 1_000 } }),
+        }),
+      ),
+    )
+  },
 })
 const it = testEffect(
   AppNodeBuilder.build(
@@ -46,6 +79,7 @@ const it = testEffect(
       SessionProjector.node,
       SessionStore.node,
       AgentV2.node,
+      Catalog.node,
       SessionTitle.node,
     ]),
     [
@@ -55,7 +89,10 @@ const it = testEffect(
   ),
 )
 
-const insertSession = (id: SessionV2.ID) =>
+const insertSession = (
+  id: SessionV2.ID,
+  model?: { id: string; providerID: string },
+) =>
   Effect.gen(function* () {
     const { db } = yield* Database.Service
     yield* db
@@ -73,6 +110,14 @@ const insertSession = (id: SessionV2.ID) =>
         directory: "/project",
         title: "New session - fake",
         version: "test",
+        ...(model
+          ? {
+              model: {
+                id: ModelV2.ID.make(model.id),
+                providerID: ProviderV2.ID.make(model.providerID),
+              },
+            }
+          : {}),
       })
       .onConflictDoNothing()
       .run()
@@ -94,17 +139,47 @@ const prompt = (sessionID: SessionV2.ID, text: string) =>
     })
   })
 
-it.effect("generates a title from the sole user message and renames the session", () =>
+const enableTitleAgent = (model?: { id: string; providerID: string }) =>
   Effect.gen(function* () {
-    requests = []
     const agentService = yield* AgentV2.Service
     yield* agentService.transform((editor) => {
       editor.update(AgentV2.ID.make("title"), (agent) => {
         agent.mode = "primary"
         agent.hidden = true
         agent.system = "You are a title generator."
+        if (model) {
+          agent.model = {
+            id: ModelV2.ID.make(model.id),
+            providerID: ProviderV2.ID.make(model.providerID),
+          }
+        }
       })
     })
+  })
+
+const seedSmallModel = () =>
+  Effect.gen(function* () {
+    const catalog = yield* Catalog.Service
+    const providerID = ProviderV2.ID.make("test")
+    yield* catalog.transform((catalog) => {
+      catalog.provider.update(providerID, () => {})
+      catalog.model.update(providerID, ModelV2.ID.make("main"), (model) => {
+        model.time.released = Date.now()
+      })
+      catalog.model.update(providerID, ModelV2.ID.make("mini"), (model) => {
+        model.enabled = false
+        model.family = ModelV2.Family.make("gpt-nano")
+        model.time.released = Date.now()
+      })
+      catalog.model.small.set(providerID, ModelV2.ID.make("mini"))
+    })
+  })
+
+it.effect("generates a title from the sole user message and renames the session", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    yield* enableTitleAgent()
     const sessionID = SessionV2.ID.make("ses_title_generate")
     yield* insertSession(sessionID)
     yield* prompt(sessionID, "Help me debug the failing build")
@@ -123,17 +198,130 @@ it.effect("generates a title from the sole user message and renames the session"
   }),
 )
 
+it.effect("prefers the catalog small model over the session model", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    yield* enableTitleAgent()
+    yield* seedSmallModel()
+    const sessionID = SessionV2.ID.make("ses_title_small_model")
+    yield* insertSession(sessionID, { id: "main", providerID: "test" })
+    yield* prompt(sessionID, "Help me debug the failing build")
+
+    const store = yield* SessionStore.Service
+    const session = yield* store
+      .get(sessionID)
+      .pipe(Effect.flatMap((session) => (session ? Effect.succeed(session) : Effect.die("session missing"))))
+    const title = yield* SessionTitle.Service
+    yield* title.generateForFirstPrompt(session)
+
+    expect(resolvedModels).toEqual([{ id: "mini", provider: "test" }])
+    expect(String(requests[0]?.model.id)).toBe("mini")
+  }),
+)
+
+it.effect("prefers the title agent model over the catalog small model", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    yield* enableTitleAgent({ id: "agent-title", providerID: "test" })
+    yield* seedSmallModel()
+    const sessionID = SessionV2.ID.make("ses_title_agent_model")
+    yield* insertSession(sessionID, { id: "main", providerID: "test" })
+    yield* prompt(sessionID, "Help me debug the failing build")
+
+    const store = yield* SessionStore.Service
+    const session = yield* store
+      .get(sessionID)
+      .pipe(Effect.flatMap((session) => (session ? Effect.succeed(session) : Effect.die("session missing"))))
+    const title = yield* SessionTitle.Service
+    yield* title.generateForFirstPrompt(session)
+
+    expect(resolvedModels).toEqual([{ id: "agent-title", provider: "test" }])
+    expect(String(requests[0]?.model.id)).toBe("agent-title")
+  }),
+)
+
+it.effect("falls back to the session model when no small model exists", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    failSmallResolve = false
+    yield* enableTitleAgent()
+    const sessionID = SessionV2.ID.make("ses_title_session_fallback")
+    yield* insertSession(sessionID, { id: "main", providerID: "test" })
+    yield* prompt(sessionID, "Help me debug the failing build")
+
+    const store = yield* SessionStore.Service
+    const session = yield* store
+      .get(sessionID)
+      .pipe(Effect.flatMap((session) => (session ? Effect.succeed(session) : Effect.die("session missing"))))
+    const title = yield* SessionTitle.Service
+    yield* title.generateForFirstPrompt(session)
+
+    expect(resolvedModels).toEqual([{ id: "main", provider: "test" }])
+    expect(String(requests[0]?.model.id)).toBe("main")
+  }),
+)
+
+it.effect("falls back to the session model when small model resolution fails", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    failSmallResolve = true
+    yield* enableTitleAgent()
+    yield* seedSmallModel()
+    const sessionID = SessionV2.ID.make("ses_title_small_resolve_fail")
+    yield* insertSession(sessionID, { id: "main", providerID: "test" })
+    yield* prompt(sessionID, "Help me debug the failing build")
+
+    const store = yield* SessionStore.Service
+    const session = yield* store
+      .get(sessionID)
+      .pipe(Effect.flatMap((session) => (session ? Effect.succeed(session) : Effect.die("session missing"))))
+    const title = yield* SessionTitle.Service
+    yield* title.generateForFirstPrompt(session)
+
+    expect(resolvedModels).toEqual([
+      { id: "mini", provider: "test" },
+      { id: "main", provider: "test" },
+    ])
+    expect(String(requests[0]?.model.id)).toBe("main")
+  }),
+)
+
+it.effect("uses the catalog default provider when the session has no model", () =>
+  Effect.gen(function* () {
+    requests = []
+    resolvedModels = []
+    failSmallResolve = false
+    yield* enableTitleAgent()
+    yield* seedSmallModel()
+    const catalog = yield* Catalog.Service
+    yield* catalog.transform((catalog) => {
+      catalog.model.default.set(ProviderV2.ID.make("test"), ModelV2.ID.make("main"))
+    })
+    const sessionID = SessionV2.ID.make("ses_title_default_provider")
+    yield* insertSession(sessionID)
+    yield* prompt(sessionID, "Help me debug the failing build")
+
+    const store = yield* SessionStore.Service
+    const session = yield* store
+      .get(sessionID)
+      .pipe(Effect.flatMap((session) => (session ? Effect.succeed(session) : Effect.die("session missing"))))
+    const title = yield* SessionTitle.Service
+    yield* title.generateForFirstPrompt(session)
+
+    expect(resolvedModels).toEqual([{ id: "mini", provider: "test" }])
+    expect(String(requests[0]?.model.id)).toBe("mini")
+  }),
+)
+
 it.effect("does not generate once a second user message exists", () =>
   Effect.gen(function* () {
     requests = []
-    const agentService = yield* AgentV2.Service
-    yield* agentService.transform((editor) => {
-      editor.update(AgentV2.ID.make("title"), (agent) => {
-        agent.mode = "primary"
-        agent.hidden = true
-        agent.system = "You are a title generator."
-      })
-    })
+    resolvedModels = []
+    yield* enableTitleAgent()
     const sessionID = SessionV2.ID.make("ses_title_second_message")
     yield* insertSession(sessionID)
     yield* prompt(sessionID, "First message")
@@ -155,14 +343,8 @@ it.effect("does not generate once a second user message exists", () =>
 it.effect("does not generate for a child session", () =>
   Effect.gen(function* () {
     requests = []
-    const agentService = yield* AgentV2.Service
-    yield* agentService.transform((editor) => {
-      editor.update(AgentV2.ID.make("title"), (agent) => {
-        agent.mode = "primary"
-        agent.hidden = true
-        agent.system = "You are a title generator."
-      })
-    })
+    resolvedModels = []
+    yield* enableTitleAgent()
     const sessionID = SessionV2.ID.make("ses_title_child")
     const { db } = yield* Database.Service
     yield* db
@@ -201,6 +383,7 @@ it.effect("does not generate for a child session", () =>
 it.effect("does not generate when the title agent is removed", () =>
   Effect.gen(function* () {
     requests = []
+    resolvedModels = []
     const sessionID = SessionV2.ID.make("ses_title_no_agent")
     yield* insertSession(sessionID)
     yield* prompt(sessionID, "Help me debug the failing build")

packages/plugin/src/v2/effect/catalog.ts

@@ -23,6 +23,11 @@ export interface CatalogDraft {
       get(): { providerID: string; modelID: string } | undefined
       set(providerID: string, modelID: string): void
     }
+    readonly small: {
+      get(providerID: string): string | undefined
+      set(providerID: string, modelID: string): void
+      remove(providerID: string): void
+    }
   }
 }