acp: handle case where big-pickle is unavailable as a fallback

packages/opencode/src/acp/agent.ts

@@ -34,13 +34,9 @@ import type { OpencodeClient, SessionMessageResponse } from "@opencode-ai/sdk/v2
 export namespace ACP {
   const log = Log.create({ service: "acp-agent" })
 
-  export async function init({ sdk }: { sdk: OpencodeClient }) {
-    const model = await defaultModel({ sdk })
+  export async function init({ sdk: _sdk }: { sdk: OpencodeClient }) {
     return {
       create: (connection: AgentSideConnection, fullConfig: ACPConfig) => {
-        if (!fullConfig.defaultModel) {
-          fullConfig.defaultModel = model
-        }
         return new Agent(connection, fullConfig)
       },
     }
@@ -988,8 +984,10 @@ export namespace ACP {
     const configured = config.defaultModel
     if (configured) return configured
 
-    const model = await sdk.config
-      .get({ directory: cwd }, { throwOnError: true })
+    const directory = cwd ?? process.cwd()
+
+    const specified = await sdk.config
+      .get({ directory }, { throwOnError: true })
       .then((resp) => {
         const cfg = resp.data
         if (!cfg || !cfg.model) return undefined
@@ -1004,7 +1002,47 @@ export namespace ACP {
         return undefined
       })
 
-    return model ?? { providerID: "opencode", modelID: "big-pickle" }
+    const providers = await sdk.config
+      .providers({ directory }, { throwOnError: true })
+      .then((x) => x.data?.providers ?? [])
+      .catch((error) => {
+        log.error("failed to list providers for default model", { error })
+        return []
+      })
+
+    if (specified && providers.length) {
+      const provider = providers.find((p) => p.id === specified.providerID)
+      if (provider && provider.models[specified.modelID]) return specified
+    }
+
+    if (specified && !providers.length) return specified
+
+    const opencodeProvider = providers.find((p) => p.id === "opencode")
+    if (opencodeProvider) {
+      if (opencodeProvider.models["big-pickle"]) {
+        return { providerID: "opencode", modelID: "big-pickle" }
+      }
+      const [best] = Provider.sort(Object.values(opencodeProvider.models))
+      if (best) {
+        return {
+          providerID: best.providerID,
+          modelID: best.id,
+        }
+      }
+    }
+
+    const models = providers.flatMap((p) => Object.values(p.models))
+    const [best] = Provider.sort(models)
+    if (best) {
+      return {
+        providerID: best.providerID,
+        modelID: best.id,
+      }
+    }
+
+    if (specified) return specified
+
+    return { providerID: "opencode", modelID: "big-pickle" }
   }
 
   function parseUri(