fix: blank assistant text with MCP enabled after AI SDK v6 migration

The v6 upgrade changed the default unmapped finish reason from 'unknown'
to 'other', but the prompt loop continue sets were not updated to match.
This caused premature loop exit after MCP tool calls, before the model
produced final assistant text.

Additionally, the LLM middleware still targeted legacy 'prompt' param key
while v6 Responses requests use 'messages' or 'input', causing
ProviderTransform.message() to be silently skipped.

Fixes #20050
Fixes #20465

Author: kostiantyn-kugot

packages/opencode/src/session/llm.ts

@@ -376,8 +376,16 @@ export namespace LLM {
             specificationVersion: "v3" as const,
             async transformParams(args) {
               if (args.type === "stream") {
-                // @ts-expect-error
-                args.params.prompt = ProviderTransform.message(args.params.prompt, input.model, options)
+                if ("messages" in args.params && Array.isArray(args.params.messages)) {
+                  args.params.messages = ProviderTransform.message(args.params.messages, input.model, options)
+                }
+                if ("input" in args.params && Array.isArray(args.params.input)) {
+                  args.params.input = ProviderTransform.message(args.params.input, input.model, options)
+                }
+                if ("prompt" in args.params && Array.isArray(args.params.prompt)) {
+                  // @ts-expect-error legacy prompt shape differs from v3 prompt typing
+                  args.params.prompt = ProviderTransform.message(args.params.prompt, input.model, options)
+                }
               }
               return args.params
             },

packages/opencode/src/session/prompt.ts

@@ -1340,7 +1340,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
 
             if (
               lastAssistant?.finish &&
-              !["tool-calls"].includes(lastAssistant.finish) &&
+              !["tool-calls", "other"].includes(lastAssistant.finish) &&
               !hasToolCalls &&
               lastUser.id < lastAssistant.id
             ) {
@@ -1494,7 +1494,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
                 return "break" as const
               }
 
-              const finished = handle.message.finish && !["tool-calls", "unknown"].includes(handle.message.finish)
+              const finished = handle.message.finish && !["tool-calls", "other"].includes(handle.message.finish)
               if (finished && !handle.message.error) {
                 if (format.type === "json_schema") {
                   handle.message.error = new MessageV2.StructuredOutputError({