fix cursor stream-json multiplexed output handling

packages/adapters/cursor-local/src/cli/format-event.ts

@@ -1,4 +1,5 @@
 import pc from "picocolors";
+import { normalizeCursorStreamLine } from "../shared/stream.js";
 
 function asRecord(value: unknown): Record<string, unknown> | null {
   if (typeof value !== "object" || value === null || Array.isArray(value)) return null;
@@ -121,7 +122,7 @@ function printLegacyToolEvent(part: Record<string, unknown>): void {
 }
 
 export function printCursorStreamEvent(raw: string, _debug: boolean): void {
-  const line = raw.trim();
+  const line = normalizeCursorStreamLine(raw).line;
   if (!line) return;
 
   let parsed: Record<string, unknown> | null = null;

packages/adapters/cursor-local/src/server/execute.ts

@@ -16,6 +16,7 @@ import {
 } from "@paperclipai/adapter-utils/server-utils";
 import { DEFAULT_CURSOR_LOCAL_MODEL } from "../index.js";
 import { parseCursorJsonl, isCursorUnknownSessionError } from "./parse.js";
+import { normalizeCursorStreamLine } from "../shared/stream.js";
 
 function firstNonEmptyLine(text: string): string {
   return (
@@ -251,13 +252,44 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
       });
     }
 
+    let stdoutLineBuffer = "";
+    const emitNormalizedStdoutLine = async (rawLine: string) => {
+      const normalized = normalizeCursorStreamLine(rawLine);
+      if (!normalized.line) return;
+      await onLog(normalized.stream ?? "stdout", `${normalized.line}\n`);
+    };
+    const flushStdoutChunk = async (chunk: string, finalize = false) => {
+      const combined = `${stdoutLineBuffer}${chunk}`;
+      const lines = combined.split(/\r?\n/);
+      stdoutLineBuffer = lines.pop() ?? "";
+
+      for (const line of lines) {
+        await emitNormalizedStdoutLine(line);
+      }
+
+      if (finalize) {
+        const trailing = stdoutLineBuffer.trim();
+        stdoutLineBuffer = "";
+        if (trailing) {
+          await emitNormalizedStdoutLine(trailing);
+        }
+      }
+    };
+
     const proc = await runChildProcess(runId, command, args, {
       cwd,
       env,
       timeoutSec,
       graceSec,
-      onLog,
+      onLog: async (stream, chunk) => {
+        if (stream !== "stdout") {
+          await onLog(stream, chunk);
+          return;
+        }
+        await flushStdoutChunk(chunk);
+      },
     });
+    await flushStdoutChunk("", true);
 
     return {
       proc,

packages/adapters/cursor-local/src/server/parse.ts

@@ -1,4 +1,5 @@
 import { asString, asNumber, parseObject, parseJson } from "@paperclipai/adapter-utils/server-utils";
+import { normalizeCursorStreamLine } from "../shared/stream.js";
 
 function asErrorText(value: unknown): string {
   if (typeof value === "string") return value;
@@ -60,7 +61,7 @@ export function parseCursorJsonl(stdout: string) {
   };
 
   for (const rawLine of stdout.split(/\r?\n/)) {
-    const line = rawLine.trim();
+    const line = normalizeCursorStreamLine(rawLine).line;
     if (!line) continue;
 
     const event = parseJson(line);

packages/adapters/cursor-local/src/shared/stream.ts

@@ -0,0 +1,16 @@
+export function normalizeCursorStreamLine(rawLine: string): {
+  stream: "stdout" | "stderr" | null;
+  line: string;
+} {
+  const trimmed = rawLine.trim();
+  if (!trimmed) return { stream: null, line: "" };
+
+  const prefixed = trimmed.match(/^(stdout|stderr)\s*[:=]?\s*([\[{].*)$/i);
+  if (!prefixed) {
+    return { stream: null, line: trimmed };
+  }
+
+  const stream = prefixed[1]?.toLowerCase() === "stderr" ? "stderr" : "stdout";
+  const line = (prefixed[2] ?? "").trim();
+  return { stream, line };
+}

packages/adapters/cursor-local/src/ui/parse-stdout.ts

@@ -1,4 +1,5 @@
 import type { TranscriptEntry } from "@paperclipai/adapter-utils";
+import { normalizeCursorStreamLine } from "../shared/stream.js";
 
 function safeJsonParse(text: string): unknown {
   try {
@@ -101,9 +102,12 @@ function parseAssistantMessage(messageRaw: unknown, ts: string): TranscriptEntry
 }
 
 export function parseCursorStdoutLine(line: string, ts: string): TranscriptEntry[] {
-  const parsed = asRecord(safeJsonParse(line));
+  const normalized = normalizeCursorStreamLine(line);
+  if (!normalized.line) return [];
+
+  const parsed = asRecord(safeJsonParse(normalized.line));
   if (!parsed) {
-    return [{ kind: "stdout", ts, text: line }];
+    return [{ kind: "stdout", ts, text: normalized.line }];
   }
 
   const type = asString(parsed.type);
@@ -156,7 +160,7 @@ export function parseCursorStdoutLine(line: string, ts: string): TranscriptEntry
   }
 
   if (type === "error") {
-    const message = asString(parsed.message) || stringifyUnknown(parsed.error ?? parsed.detail) || line;
+    const message = asString(parsed.message) || stringifyUnknown(parsed.error ?? parsed.detail) || normalized.line;
     return [{ kind: "stderr", ts, text: message }];
   }
 
@@ -236,5 +240,5 @@ export function parseCursorStdoutLine(line: string, ts: string): TranscriptEntry
     }];
   }
 
-  return [{ kind: "stdout", ts, text: line }];
+  return [{ kind: "stdout", ts, text: normalized.line }];
 }

server/src/__tests__/cursor-local-adapter.test.ts

@@ -39,6 +39,24 @@ describe("cursor parser", () => {
     expect(parsed.costUsd).toBeCloseTo(0.001, 6);
     expect(parsed.errorMessage).toBe("model access denied");
   });
+
+  it("parses multiplexed stdout-prefixed json lines", () => {
+    const stdout = [
+      'stdout{"type":"system","subtype":"init","session_id":"chat_prefixed","model":"gpt-5"}',
+      'stdout{"type":"assistant","message":{"content":[{"type":"output_text","text":"prefixed hello"}]}}',
+      'stdout{"type":"result","subtype":"success","usage":{"input_tokens":3,"output_tokens":2,"cached_input_tokens":1},"total_cost_usd":0.0001}',
+    ].join("\n");
+
+    const parsed = parseCursorJsonl(stdout);
+    expect(parsed.sessionId).toBe("chat_prefixed");
+    expect(parsed.summary).toBe("prefixed hello");
+    expect(parsed.usage).toEqual({
+      inputTokens: 3,
+      cachedInputTokens: 1,
+      outputTokens: 2,
+    });
+    expect(parsed.costUsd).toBeCloseTo(0.0001, 6);
+  });
 });
 
 describe("cursor stale session detection", () => {
@@ -108,6 +126,16 @@ describe("cursor ui stdout parser", () => {
       },
     ]);
   });
+
+  it("parses stdout-prefixed json lines", () => {
+    const ts = "2026-03-05T00:00:00.000Z";
+    expect(
+      parseCursorStdoutLine(
+        'stdout{"type":"assistant","message":{"content":[{"type":"thinking","text":"streamed"}]}}',
+        ts,
+      ),
+    ).toEqual([{ kind: "thinking", ts, text: "streamed" }]);
+  });
 });
 
 function stripAnsi(value: string): string {