diff --git a/packages/host-service/src/daemon/DaemonSupervisor.ts b/packages/host-service/src/daemon/DaemonSupervisor.ts
index d139fc25f6e..780fac08fda 100644
--- a/packages/host-service/src/daemon/DaemonSupervisor.ts
+++ b/packages/host-service/src/daemon/DaemonSupervisor.ts
@@ -942,16 +942,28 @@ export class DaemonSupervisor {
 			// Prod: detached so PTYs survive host-service restarts via socket
 			// adoption. Dev: attached as defense-in-depth in case serve.ts's
 			// dev shutdown doesn't fire (e.g. host-service crash).
-			child = childProcess.spawn(
-				process.execPath,
-				[this.opts.scriptPath, `--socket=${socketPath}`],
-				{
-					detached: !isDev,
-					stdio,
-					env: childEnv,
-					windowsHide: true,
-				},
-			);
+			// Raise RLIMIT_NOFILE before exec: macOS's 256 soft default starves a
+			// daemon hosting many worktrees' PTYs and surfaces as node-pty
+			// "posix_spawnp failed" (EMFILE). The raised limit is inherited by
+			// handoff successors the daemon spawns from itself.
+			const isWindows = process.platform === "win32";
+			const command = isWindows ? process.execPath : "/bin/sh";
+			const commandArgs = isWindows
+				? [this.opts.scriptPath, `--socket=${socketPath}`]
+				: [
+						"-c",
+						'ulimit -n 1048576 2>/dev/null || ulimit -n "$(ulimit -Hn)" 2>/dev/null || true; exec "$@"',
+						"sh",
+						process.execPath,
+						this.opts.scriptPath,
+						`--socket=${socketPath}`,
+					];
+			child = childProcess.spawn(command, commandArgs, {
+				detached: !isDev,
+				stdio,
+				env: childEnv,
+				windowsHide: true,
+			});
 		} finally {
 			if (logFd >= 0) {
 				try {
diff --git a/packages/pty-daemon/src/Pty/Pty.ts b/packages/pty-daemon/src/Pty/Pty.ts
index 054b09c6172..6bf8a83d4a7 100644
--- a/packages/pty-daemon/src/Pty/Pty.ts
+++ b/packages/pty-daemon/src/Pty/Pty.ts
@@ -142,6 +142,21 @@ function validateDims(cols: number, rows: number): void {
 	}
 }
 
+function reprobeErrno(meta: SessionMeta): string {
+	try {
+		const probe = childProcess.spawnSync(meta.shell, ["-c", ":"], {
+			cwd: meta.cwd,
+			timeout: 1000,
+			stdio: "ignore",
+		});
+		if (!probe.error) return "ok";
+		const e = probe.error as NodeJS.ErrnoException;
+		return e.code ?? e.message;
+	} catch (e) {
+		return `reprobe-failed:${(e as Error).message}`;
+	}
+}
+
 export function spawn({ meta }: SpawnOptions): Pty {
 	validateDims(meta.cols, meta.rows);
 	// Pre-flight: node-pty's "posix_spawnp failed" message swallows errno
@@ -178,9 +193,11 @@ export function spawn({ meta }: SpawnOptions): Pty {
 			encoding: null,
 		});
 	} catch (err) {
-		// Annotate with shell + cwd so the wire-error reply is actionable.
+		// node-pty's native "posix_spawnp failed." drops the errno, so re-probe
+		// the same shell+cwd with spawnSync to surface the real code (e.g.
+		// EMFILE/EAGAIN/ENOENT).
 		throw new Error(
-			`spawn failed (shell=${meta.shell} cwd=${meta.cwd ?? "(none)"}): ${(err as Error).message}`,
+			`spawn failed (shell=${meta.shell} cwd=${meta.cwd ?? "(none)"} errno=${reprobeErrno(meta)}): ${(err as Error).message}`,
 		);
 	}
 	const adapter = new NodePtyAdapter(term, meta);