fix: expose cursor thinking as reasoning_content in plugin proxy

Author: Your Name

src/plugin.ts

@@ -8,7 +8,7 @@ import { startCursorOAuth } from "./auth";
 import { LineBuffer } from "./streaming/line-buffer.js";
 import { StreamToSseConverter, formatSseDone } from "./streaming/openai-sse.js";
 import { parseStreamJsonLine } from "./streaming/parser.js";
-import { extractText, isAssistantText } from "./streaming/types.js";
+import { extractText, extractThinking, isAssistantText, isThinking } from "./streaming/types.js";
 import { createLogger } from "./utils/logger";
 import { parseAgentError, formatErrorForUser, stripAnsi } from "./utils/errors";
 import { OpenCodeToolDiscovery } from "./tools/discovery.js";
@@ -38,7 +38,16 @@ function getGlobalKey(): string {
   return "__opencode_cursor_proxy_server__";
 }
 
-function createChatCompletionResponse(model: string, content: string) {
+function createChatCompletionResponse(model: string, content: string, reasoningContent?: string) {
+  const message: { role: "assistant"; content: string; reasoning_content?: string } = {
+    role: "assistant",
+    content,
+  };
+
+  if (reasoningContent && reasoningContent.length > 0) {
+    message.reasoning_content = reasoningContent;
+  }
+
   return {
     id: `cursor-acp-${Date.now()}`,
     object: "chat.completion",
@@ -47,7 +56,7 @@ function createChatCompletionResponse(model: string, content: string) {
     choices: [
       {
         index: 0,
-        message: { role: "assistant", content },
+        message,
         finish_reason: "stop",
       },
     ],
@@ -70,16 +79,30 @@ function createChatCompletionChunk(id: string, created: number, model: string, d
   };
 }
 
-function extractAssistantTextFromStream(output: string): string {
+function extractCompletionFromStream(output: string): { assistantText: string; reasoningText: string } {
   const lines = output.split("\n");
-  let content = "";
+  let assistantText = "";
+  let reasoningText = "";
+
   for (const line of lines) {
     const event = parseStreamJsonLine(line);
-    if (event && isAssistantText(event)) {
-      content = extractText(event);
+    if (!event) {
+      continue;
+    }
+
+    if (isAssistantText(event)) {
+      assistantText = extractText(event);
+    }
+
+    if (isThinking(event)) {
+      const thinking = extractThinking(event);
+      if (thinking) {
+        reasoningText += thinking;
+      }
     }
   }
-  return content;
+
+  return { assistantText, reasoningText };
 }
 
 function formatToolUpdateEvent(update: ToolUpdate): string {
@@ -198,6 +221,7 @@ async function ensureCursorProxyServer(workspaceDirectory: string, toolRouter?:
         "--print",
         "--output-format",
         "stream-json",
+        "--stream-partial-output",
         "--workspace",
         workspaceDirectory,
         "--model",
@@ -239,8 +263,12 @@ async function ensureCursorProxyServer(workspaceDirectory: string, toolRouter?:
           });
         }
 
-        const assistantText = extractAssistantTextFromStream(stdout);
-        const payload = createChatCompletionResponse(model, assistantText || stdout || stderr);
+        const completion = extractCompletionFromStream(stdout);
+        const payload = createChatCompletionResponse(
+          model,
+          completion.assistantText || stdout || stderr,
+          completion.reasoningText || undefined,
+        );
         return new Response(JSON.stringify(payload), {
           status: 200,
           headers: { "Content-Type": "application/json" },
@@ -452,6 +480,7 @@ async function ensureCursorProxyServer(workspaceDirectory: string, toolRouter?:
         "--print",
         "--output-format",
         "stream-json",
+        "--stream-partial-output",
         "--workspace",
         workspaceDirectory,
         "--model",
@@ -474,7 +503,7 @@ async function ensureCursorProxyServer(workspaceDirectory: string, toolRouter?:
         child.on("close", async (code) => {
           const stdout = Buffer.concat(stdoutChunks).toString().trim();
           const stderr = Buffer.concat(stderrChunks).toString().trim();
-          const assistantText = extractAssistantTextFromStream(stdout);
+          const completion = extractCompletionFromStream(stdout);
 
           if (code !== 0 && stderr.length > 0) {
             const parsed = parseAgentError(stderr);
@@ -507,7 +536,15 @@ async function ensureCursorProxyServer(workspaceDirectory: string, toolRouter?:
               choices: [
                 {
                   index: 0,
-                  message: { role: "assistant", content: assistantText || stdout || stderr },
+                  message: {
+                    role: "assistant",
+                    content: completion.assistantText || stdout || stderr,
+                    ...(completion.reasoningText
+                      ? {
+                          reasoning_content: completion.reasoningText,
+                        }
+                      : {}),
+                  },
                   finish_reason: "stop",
                 },
               ],

src/streaming/openai-sse.ts

@@ -22,6 +22,7 @@ type OpenAiToolCall = {
 
 type OpenAiDelta = {
   content?: string;
+  reasoning_content?: string;
   tool_calls?: OpenAiToolCall[];
 };
 
@@ -75,7 +76,7 @@ export class StreamToSseConverter {
 
     if (isThinking(event)) {
       const delta = this.tracker.nextThinking(extractThinking(event));
-      return delta ? [this.chunkWith({ content: delta })] : [];
+      return delta ? [this.chunkWith({ reasoning_content: delta })] : [];
     }
 
     if (isToolCall(event)) {