cursor adapter: pipe prompts over stdin

packages/adapters/cursor-local/src/index.ts

@@ -76,7 +76,7 @@ Operational fields:
 
 Notes:
 - Runs are executed with: agent -p --output-format stream-json ...
-- Prompts are passed as a final positional argument.
+- Prompts are piped to Cursor via stdin.
 - Sessions are resumed with --resume when stored session cwd matches current cwd.
 - Paperclip auto-injects local skills into "~/.cursor/skills" when missing, so Cursor can discover "$paperclip" and related skills on local runs.
 - Paperclip auto-adds --trust unless one of --trust/--yolo/-f is already present in extraArgs.

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

@@ -301,6 +301,7 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     if (autoTrustEnabled) {
       notes.push("Auto-added --trust to bypass interactive workspace trust prompt.");
     }
+    notes.push("Prompt is piped to Cursor via stdin.");
     if (!instructionsFilePath) return notes;
     if (instructionsPrefix.length > 0) {
       notes.push(
@@ -334,7 +335,6 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
     if (mode) args.push("--mode", mode);
     if (autoTrustEnabled) args.push("--trust");
     if (extraArgs.length > 0) args.push(...extraArgs);
-    args.push(prompt);
     return args;
   };
 
@@ -346,10 +346,7 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
         command,
         cwd,
         commandNotes,
-        commandArgs: args.map((value, idx) => {
-          if (idx === args.length - 1) return `<prompt ${prompt.length} chars>`;
-          return value;
-        }),
+        commandArgs: args,
         env: redactEnvForLogs(env),
         prompt,
         context,
@@ -385,6 +382,7 @@ export async function execute(ctx: AdapterExecutionContext): Promise<AdapterExec
       env,
       timeoutSec,
       graceSec,
+      stdin: prompt,
       onLog: async (stream, chunk) => {
         if (stream !== "stdout") {
           await onLog(stream, chunk);

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

@@ -11,7 +11,7 @@ const fs = require("node:fs");
 const capturePath = process.env.PAPERCLIP_TEST_CAPTURE_PATH;
 const payload = {
   argv: process.argv.slice(2),
-  prompt: process.argv.at(-1) ?? "",
+  prompt: fs.readFileSync(0, "utf8"),
   paperclipEnvKeys: Object.keys(process.env)
     .filter((key) => key.startsWith("PAPERCLIP_"))
     .sort(),
@@ -96,6 +96,7 @@ describe("cursor execute", () => {
       expect(result.errorMessage).toBeNull();
 
       const capture = JSON.parse(await fs.readFile(capturePath, "utf8")) as CapturePayload;
+      expect(capture.argv).not.toContain("Follow the paperclip heartbeat.");
       expect(capture.argv).not.toContain("--mode");
       expect(capture.argv).not.toContain("ask");
       expect(capture.paperclipEnvKeys).toEqual(