fix(task): limit small models to explore agents

packages/opencode/src/provider/provider.ts

@@ -28,6 +28,7 @@ import { withStatics } from "@/util/schema"
 
 import * as ProviderTransform from "./transform"
 import { ModelID, ProviderID } from "./schema"
+import { ProviderSmallModel } from "./small-model"
 
 const log = Log.create({ service: "provider" })
 
@@ -1611,22 +1612,10 @@ const layer: Layer.Layer<
       const provider = s.providers[providerID]
       if (!provider) return undefined
 
-      let priority = [
-        "claude-haiku-4-5",
-        "claude-haiku-4.5",
-        "3-5-haiku",
-        "3.5-haiku",
-        "gemini-3-flash",
-        "gemini-2.5-flash",
-        "gpt-5-nano",
-      ]
-      if (providerID.startsWith("opencode")) {
-        priority = ["gpt-5-nano"]
-      }
-      if (providerID.startsWith("github-copilot")) {
-        priority = ["gpt-5-mini", "claude-haiku-4.5", ...priority]
-      }
+      const priority = ProviderSmallModel.priority[providerID] ?? []
       for (const item of priority) {
+        if (provider.models[item]) return yield* getModel(providerID, ModelID.make(item))
+
         if (providerID === ProviderID.amazonBedrock) {
           const crossRegionPrefixes = ["global.", "us.", "eu."]
           const candidates = Object.keys(provider.models).filter((m) => m.includes(item))

packages/opencode/src/provider/small-model.ts

@@ -0,0 +1,73 @@
+export * as ProviderSmallModel from "./small-model"
+
+export const priority: Record<string, string[]> = {
+  opencode: [
+    "gpt-5.4-mini",
+    "gemini-3-flash",
+    "claude-haiku-4-5",
+  ],
+  "opencode-go": ["minimax-m2.7", "minimax-m2.5"],
+  openai: [
+    "gpt-5.4-mini",
+    "gpt-5.4-nano",
+    "gpt-5.1-codex-mini",
+    "gpt-5-mini",
+    "gpt-5-nano",
+    "gpt-4.1-nano",
+    "gpt-4o-mini",
+  ],
+  anthropic: ["claude-haiku-4-5", "claude-3-5-haiku", "claude-3-haiku"],
+  google: [
+    "gemini-3.1-flash-lite-preview",
+    "gemini-flash-lite-latest",
+    "gemini-3-flash-preview",
+    "gemini-2.5-flash",
+    "gemini-2.5-flash-lite",
+    "gemini-2.0-flash-lite",
+  ],
+  "google-vertex": [
+    "gemini-3.1-flash-lite-preview",
+    "gemini-flash-lite-latest",
+    "gemini-3-flash-preview",
+    "gemini-2.5-flash",
+    "gemini-2.5-flash-lite",
+    "gemini-2.0-flash-lite",
+  ],
+  "github-copilot": [
+    "gpt-5.4-mini",
+    "gemini-3-flash-preview",
+    "claude-haiku-4.5",
+  ],
+  xai: [
+    "grok-4.20-0309-non-reasoning",
+    "grok-4-1-fast-non-reasoning",
+    "grok-4-fast-non-reasoning",
+    "grok-code-fast-1",
+    "grok-3-mini-fast-latest",
+    "grok-3-mini-fast",
+    "grok-3-mini-latest",
+    "grok-3-mini",
+  ],
+  "amazon-bedrock": [
+    "anthropic.claude-haiku-4-5",
+    "openai.gpt-oss-20b",
+    "mistral.ministral-3-8b",
+    "mistral.ministral-3-3b",
+    "amazon.nova-2-lite",
+    "amazon.nova-lite",
+    "mistral.voxtral-mini-3b",
+    "meta.llama3-1-8b",
+  ],
+  openrouter: [
+    "openai/gpt-5.4-mini",
+    "openai/gpt-5.4-nano",
+    "google/gemini-3.1-flash-lite-preview",
+    "anthropic/claude-haiku-4.5",
+    "x-ai/grok-4.20-beta",
+    "x-ai/grok-4-fast",
+    "mistralai/mistral-small-2603",
+    "openai/gpt-5.1-codex-mini",
+    "openai/gpt-5-mini",
+    "openai/gpt-5-nano",
+  ],
+}

packages/opencode/src/tool/task.ts

@@ -6,6 +6,7 @@ import { MessageV2 } from "../session/message-v2"
 import { Agent } from "../agent/agent"
 import type { SessionPrompt } from "../session/prompt"
 import { Config } from "@/config/config"
+import { Provider } from "@/provider/provider"
 import { Effect, Schema } from "effect"
 
 export interface TaskPromptOps {
@@ -32,6 +33,7 @@ export const TaskTool = Tool.define(
   Effect.gen(function* () {
     const agent = yield* Agent.Service
     const config = yield* Config.Service
+    const provider = yield* Provider.Service
     const sessions = yield* Session.Service
 
     const run = Effect.fn("TaskTool.execute")(function* (
@@ -99,9 +101,10 @@ export const TaskTool = Tool.define(
       const msg = yield* Effect.sync(() => MessageV2.get({ sessionID: ctx.sessionID, messageID: ctx.messageID }))
       if (msg.info.role !== "assistant") return yield* Effect.fail(new Error("Not an assistant message"))
 
+      const smallModel = !next.model && next.name === "explore" ? yield* provider.getSmallModel(msg.info.providerID) : undefined
       const model = next.model ?? {
-        modelID: msg.info.modelID,
-        providerID: msg.info.providerID,
+        modelID: smallModel?.id ?? msg.info.modelID,
+        providerID: smallModel?.providerID ?? msg.info.providerID,
       }
 
       yield* ctx.metadata({

packages/opencode/test/tool/task.test.ts

@@ -2,6 +2,7 @@ import { afterEach, describe, expect } from "bun:test"
 import { Effect, Layer } from "effect"
 import { Agent } from "../../src/agent/agent"
 import { Config } from "@/config/config"
+import { Provider } from "@/provider/provider"
 import { CrossSpawnSpawner } from "@opencode-ai/core/cross-spawn-spawner"
 import { Instance } from "../../src/project/instance"
 import { Session } from "@/session/session"
@@ -28,6 +29,7 @@ const it = testEffect(
   Layer.mergeAll(
     Agent.defaultLayer,
     Config.defaultLayer,
+    Provider.defaultLayer,
     CrossSpawnSpawner.defaultLayer,
     Session.defaultLayer,
     Truncate.defaultLayer,
@@ -35,7 +37,7 @@ const it = testEffect(
   ),
 )
 
-const seed = Effect.fn("TaskToolTest.seed")(function* (title = "Pinned") {
+const seed = Effect.fn("TaskToolTest.seed")(function* (title = "Pinned", model = ref) {
   const session = yield* Session.Service
   const chat = yield* session.create({ title })
   const user = yield* session.updateMessage({
@@ -43,7 +45,7 @@ const seed = Effect.fn("TaskToolTest.seed")(function* (title = "Pinned") {
     role: "user",
     sessionID: chat.id,
     agent: "build",
-    model: ref,
+    model,
     time: { created: Date.now() },
   })
   const assistant: MessageV2.Assistant = {
@@ -56,8 +58,8 @@ const seed = Effect.fn("TaskToolTest.seed")(function* (title = "Pinned") {
     cost: 0,
     path: { cwd: "/tmp", root: "/tmp" },
     tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
-    modelID: ref.modelID,
-    providerID: ref.providerID,
+    modelID: model.modelID,
+    providerID: model.providerID,
     time: { created: Date.now() },
   }
   yield* session.updateMessage(assistant)
@@ -274,6 +276,56 @@ describe("tool.task", () => {
     ),
   )
 
+  it.live("execute defaults explore agents to the provider small model", () =>
+    provideTmpdirInstance(
+      () =>
+        Effect.gen(function* () {
+          const current = {
+            providerID: ProviderID.openai,
+            modelID: ModelID.make("gpt-5"),
+          }
+          const { chat, assistant } = yield* seed("Pinned", current)
+          const tool = yield* TaskTool
+          const def = yield* tool.init()
+          let seen: SessionPrompt.PromptInput | undefined
+          const promptOps = stubOps({ onPrompt: (input) => (seen = input) })
+
+          const result = yield* def.execute(
+            {
+              description: "inspect bug",
+              prompt: "look into the cache key path",
+              subagent_type: "explore",
+            },
+            {
+              sessionID: chat.id,
+              messageID: assistant.id,
+              agent: "build",
+              abort: new AbortController().signal,
+              extra: { promptOps },
+              messages: [],
+              metadata: () => Effect.void,
+              ask: () => Effect.void,
+            },
+          )
+
+          expect(result.metadata.model).toEqual({
+            providerID: ProviderID.openai,
+            modelID: ModelID.make("gpt-5.4-mini"),
+          })
+          expect(seen?.model).toEqual(result.metadata.model)
+        }),
+      {
+        config: {
+          provider: {
+            openai: {
+              options: { apiKey: "test" },
+            },
+          },
+        },
+      },
+    ),
+  )
+
   it.live("execute creates a child when task_id does not exist", () =>
     provideTmpdirInstance(() =>
       Effect.gen(function* () {