fix(tooling): emit NDJSON MCP responses for agentctl and jev

Cursor IDE loads pi-subagents (NDJSON) but not agentctl/jev which replied
with Content-Length framing. Align send() and mark type=stdio in mcp.json.

scripts/mcp/README.md

@@ -42,9 +42,13 @@ The executor resolves `agentctl` helpers from the git main worktree scripts dire
 
 Scoped reads: `scripts/pi-subagent-readonly.ts` — builtin `path` only; `@`/`~` denied; directory walks must contain only allowlisted regular files. Approved tests use a separate snapshot; model evidence stays pristine.
 
-### Cursor CLI compatibility (pi-subagents)
+### Cursor CLI / IDE compatibility
 
-Real Cursor CLI `2026.09.18` (and `2026.09.23` verified here) does **not** expand `${workspaceFolder}` in MCP `args`. The `pi-subagents` entry therefore uses workspace-relative `args: ["scripts/mcp/pi-subagents-mcp.mjs"]` with `type: "stdio"` / `command: "node"`. Absolute `${workspaceFolder}/…` paths fail with `Cannot find module '…/${workspaceFolder}/scripts/mcp/pi-subagents-mcp.mjs'`. After `agent mcp enable pi-subagents`, `agent mcp list-tools pi-subagents` must report exactly three tools: `pi_subagent_roles`, `pi_subagent_run`, `pi_subagent_result`. Older `agentctl` / `jev` entries may still use `${workspaceFolder}` until separately corrected.
+Real Cursor CLI `2026.09.18+` does **not** expand `${workspaceFolder}` in MCP `args`. All Node MCP entries use workspace-relative `args: ["scripts/mcp/….mjs"]` with `"type": "stdio"`.
+
+**Response framing:** Cursor stdio MCP expects **newline-delimited JSON-RPC** responses (same as `pi-subagents-mcp.mjs`). `agentctl-mcp.mjs` / `jev-mcp.mjs` historically replied with `Content-Length` framing, which prevented IDE loading even after path fixes; they now emit NDJSON while still accepting Content-Length *requests* on stdin.
+
+After reload + enable: `agent mcp list-tools agentctl` / `jev` / `pi-subagents` should list tools. Older Connection-failed notes that only cited `${workspaceFolder}` are incomplete without the framing check.
 
 ### Limitations (v1)
 

scripts/mcp/agentctl-mcp.mjs

@@ -4,7 +4,6 @@
  * lease_run passes command as argv after `--` — no extra shell.
  */
 import { spawnSync } from 'node:child_process';
-import { createInterface } from 'node:readline';
 import { fileURLToPath } from 'node:url';
 import path from 'node:path';
 import fs from 'node:fs';
@@ -339,8 +338,10 @@ function callTool(name, args = {}) {
 }
 
 function send(msg) {
+  // Cursor IDE/CLI stdio MCP expects newline-delimited JSON-RPC (same as pi-subagents).
+  // Still accept Content-Length framed *requests* on stdin for compatibility.
   const body = JSON.stringify(msg);
-  process.stdout.write(`Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n${body}`);
+  process.stdout.write(body + '\n');
 }
 
 function handle(msg) {

scripts/mcp/jev-mcp.mjs

@@ -165,8 +165,10 @@ async function callTool(name, args = {}) {
 }
 
 function send(msg) {
+  // Cursor IDE/CLI stdio MCP expects newline-delimited JSON-RPC (same as pi-subagents).
+  // Still accept Content-Length framed *requests* on stdin for compatibility.
   const body = JSON.stringify(msg);
-  process.stdout.write(`Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n${body}`);
+  process.stdout.write(body + '\n');
 }
 
 function handle(msg) {

scripts/tests/test_mcp_ndjson_framing.py

@@ -0,0 +1,70 @@
+"""Stdio MCP framing: Cursor expects NDJSON responses (pi-subagents style)."""
+from __future__ import annotations
+
+import json
+import subprocess
+import unittest
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parents[2]
+MCP = REPO / "scripts" / "mcp"
+
+
+class McpNdjsonFramingTest(unittest.TestCase):
+    def _handshake(self, script: Path) -> dict:
+        """Send NDJSON initialize; expect a single NDJSON JSON-RPC response line."""
+        req = {
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "initialize",
+            "params": {
+                "protocolVersion": "2024-11-05",
+                "capabilities": {},
+                "clientInfo": {"name": "unittest", "version": "0"},
+            },
+        }
+        r = subprocess.run(
+            ["node", str(script)],
+            input=json.dumps(req) + "\n",
+            capture_output=True,
+            text=True,
+            cwd=str(REPO),
+            timeout=10,
+            check=False,
+        )
+        out = (r.stdout or "").strip()
+        # Must not use Content-Length response framing for Cursor IDE.
+        self.assertFalse(
+            out.lower().startswith("content-length:"),
+            f"{script.name} still uses Content-Length response: {out[:120]!r}",
+        )
+        lines = [ln for ln in out.splitlines() if ln.strip()]
+        self.assertTrue(lines, f"{script.name} produced no stdout: stderr={r.stderr!r}")
+        msg = json.loads(lines[0])
+        self.assertEqual(msg.get("jsonrpc"), "2.0")
+        self.assertEqual(msg.get("id"), 1)
+        self.assertIn("result", msg)
+        return msg
+
+    def test_agentctl_initialize_ndjson(self):
+        msg = self._handshake(MCP / "agentctl-mcp.mjs")
+        self.assertEqual(msg["result"]["serverInfo"]["name"], "agentctl")
+
+    def test_jev_initialize_ndjson(self):
+        msg = self._handshake(MCP / "jev-mcp.mjs")
+        self.assertEqual(msg["result"]["serverInfo"]["name"], "jev")
+
+    def test_pi_subagents_initialize_ndjson(self):
+        msg = self._handshake(MCP / "pi-subagents-mcp.mjs")
+        self.assertEqual(msg["result"]["serverInfo"]["name"], "pi-subagents")
+
+    def test_mcp_json_stdio_type_for_all_node_servers(self):
+        cfg = json.loads((REPO / ".cursor" / "mcp.json").read_text(encoding="utf-8"))
+        for name in ("agentctl", "jev", "pi-subagents"):
+            entry = cfg["mcpServers"][name]
+            self.assertEqual(entry.get("type"), "stdio", name)
+            self.assertTrue(any(a.startswith("scripts/") for a in entry["args"]), name)
+
+
+if __name__ == "__main__":
+    unittest.main()