From 0cb3a8ba6d4b8a07d35b0beba3633f05095896cf Mon Sep 17 00:00:00 2001
From: Sanskar Singh <116519896+itzrnvr@users.noreply.github.com>
Date: Sat, 16 May 2026 11:08:31 +0530
Subject: [PATCH] fix: respond to ConPTY DSR cursor query on spawn
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ConPTY sends ESC[6n (Device Status Report — report cursor position)
immediately on session start and blocks the child process until it
receives a reply. Since portable-pty never responds, the child hangs
forever and the PTY times out.

Fix: write ESC[1;1R (cursor at row 1, col 1) to the PTY input pipe
right after spawning, before reading any output. This unblocks ConPTY
and allows the child process to start normally.
---
 .gitignore                         |  1 +
 crates/pi-natives/src/pty.rs       | 18 +++++++++++++--
 packages/natives/native/index.d.ts |  5 ++++
 repro_pty.rs                       | 20 ++++++++++++++++
 test-pty.ts                        | 37 ++++++++++++++++++++++++++++++
 5 files changed, 79 insertions(+), 2 deletions(-)
 create mode 100644 repro_pty.rs
 create mode 100644 test-pty.ts

diff --git a/.gitignore b/.gitignore
index b17590ad7..bf283ba5f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -61,3 +61,4 @@ python/omp-rpc/src/omp_rpc.egg-info/
 # parallel-agent worktrees
 .wt/
 CPU*.md
+packages/coding-agent/binaries/
diff --git a/crates/pi-natives/src/pty.rs b/crates/pi-natives/src/pty.rs
index 6fcb2137a..1b4a33c84 100644
--- a/crates/pi-natives/src/pty.rs
+++ b/crates/pi-natives/src/pty.rs
@@ -252,8 +252,18 @@ fn run_pty_sync(
 			.map_err(|err| Error::from_reason(format!("Failed to open PTY: {err}")))?
 	};
 
-	let mut cmd = CommandBuilder::new(config.shell.as_deref().unwrap_or("sh"));
-	cmd.arg("-lc");
+	let shell = config.shell.as_deref().unwrap_or("sh");
+	let mut cmd = CommandBuilder::new(shell);
+	// Use shell-appropriate command execution flags
+	let lower = shell.to_lowercase();
+	if lower.ends_with("cmd.exe") || lower.ends_with("cmd") {
+		cmd.arg("/c");
+	} else if lower.contains("powershell") || lower.contains("pwsh") {
+		cmd.arg("-Command");
+	} else {
+		// sh/bash/zsh/fish etc.
+		cmd.arg("-lc");
+	}
 	cmd.arg(&config.command);
 	if let Some(cwd) = config.cwd.as_ref() {
 		cmd.cwd(cwd);
@@ -276,6 +286,10 @@ fn run_pty_sync(
 	let mut writer = master
 		.take_writer()
 		.map_err(|err| Error::from_reason(format!("Failed to create PTY writer: {err}")))?;
+	// ConPTY sends ESC[6n (cursor position query) and blocks until we reply.
+	// Reply with cursor at 1,1 so it unblocks the child spawn.
+	let _ = writer.write_all(b"\x1b[1;1R");
+	let _ = writer.flush();
 	let mut reader = master
 		.try_clone_reader()
 		.map_err(|err| Error::from_reason(format!("Failed to create PTY reader: {err}")))?;
diff --git a/packages/natives/native/index.d.ts b/packages/natives/native/index.d.ts
index d3a32e970..7153c09d6 100644
--- a/packages/natives/native/index.d.ts
+++ b/packages/natives/native/index.d.ts
@@ -1137,6 +1137,11 @@ export interface PtyStartOptions {
   cols?: number
   /** PTY row count. */
   rows?: number
+  /**
+   * Shell binary to use (e.g. "sh", "bash", or an absolute path).
+   * Defaults to "sh" if not provided.
+   */
+  shell?: string
 }
 
 /**
diff --git a/repro_pty.rs b/repro_pty.rs
new file mode 100644
index 000000000..c9f2c4f51
--- /dev/null
+++ b/repro_pty.rs
@@ -0,0 +1,20 @@
+use portable_pty::{native_pty_system, PtySize, CommandBuilder};
+
+fn main() {
+    println!("Starting PTY reproduction...");
+    let pty_system = native_pty_system();
+    println!("Got pty system");
+
+    let pair = pty_system.openpty(PtySize {
+        rows: 40,
+        cols: 120,
+        pixel_width: 0,
+        pixel_height: 0,
+    });
+    match pair {
+        Ok(p) => println!("openpty succeeded!"),
+        Err(e) => println!("openpty failed: {}", e),
+    }
+
+    println!("Done.");
+}
diff --git a/test-pty.ts b/test-pty.ts
new file mode 100644
index 000000000..f8de4fb69
--- /dev/null
+++ b/test-pty.ts
@@ -0,0 +1,37 @@
+import { PtySession } from "@oh-my-pi/pi-natives";
+
+async function testPty(shell: string, command: string, label: string) {
+  const session = new PtySession();
+  const t0 = Date.now();
+  let output = "";
+
+  await new Promise<void>((resolve) => {
+    session.start(
+      {
+        command,
+        shell,
+        timeoutMs: 5000,
+        cols: 80,
+        rows: 24,
+      },
+      (_err, chunk) => {
+        if (chunk) output += chunk;
+      },
+    ).then((result) => {
+      const ms = Date.now() - t0;
+      // Strip VT sequences for readable output
+      const clean = output.replace(/\x1b\[[^a-zA-Z]*[a-zA-Z]/g, "").replace(/\x1b\][^\x07]*\x07/g, "").trim();
+      console.log(`[${label}] ${ms}ms timedOut=${result.timedOut} exitCode=${result.exitCode} output="${clean}"`);
+      resolve();
+    }).catch((err) => {
+      console.log(`[${label}] ${Date.now() - t0}ms ERROR: ${err.message}`);
+      resolve();
+    });
+    setTimeout(() => { console.log(`[${label}] HUNG`); resolve(); }, 10000);
+  });
+}
+
+await testPty("cmd.exe", "echo hello from cmd", "cmd");
+await testPty("powershell.exe", "Write-Host 'hello from pwsh'", "pwsh");
+await testPty("sh", "echo hello from bash", "sh-git-bash");
+process.exit(0);