fix: drain piped stderr in runServerCapture/waitForCloudInit to prevent deadlock (#1915)

PR #1903 fixed a pipe buffer deadlock in awsCli() by draining both
stdout and stderr before awaiting proc.exited. The same pattern existed
in runServerCapture() across 4 cloud providers and waitForCloudInit()
across 3 providers. If SSH produces >64KB of stderr, the child blocks
writing to the full pipe while the parent blocks waiting for exit.

Fixes: hetzner, aws, digitalocean, gcp — 7 locations total.

Co-authored-by: B <6723574+louisgv@users.noreply.github.com>

packages/cli/src/aws/aws.ts

@@ -1062,7 +1062,11 @@ export async function runServerCapture(cmd: string, timeoutSecs?: number): Promi
       /* ignore */
     }
   }, timeout);
-  const stdout = await new Response(proc.stdout).text();
+  // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+  const [stdout] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+  ]);
   const exitCode = await proc.exited;
   clearTimeout(timer);
   if (exitCode !== 0) {

packages/cli/src/digitalocean/digitalocean.ts

@@ -928,7 +928,11 @@ export async function waitForCloudInit(ip?: string, _maxAttempts = 60): Promise<
           ],
         },
       );
-      const stdout = await new Response(proc.stdout).text();
+      // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+      const [stdout] = await Promise.all([
+        new Response(proc.stdout).text(),
+        new Response(proc.stderr).text(),
+      ]);
       if ((await proc.exited) === 0 && stdout.includes("done")) {
         logInfo("Cloud-init complete");
         return;
@@ -1011,7 +1015,11 @@ export async function runServerCapture(cmd: string, timeoutSecs?: number, ip?: s
       proc.kill();
     } catch {}
   }, timeout);
-  const stdout = await new Response(proc.stdout).text();
+  // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+  const [stdout] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+  ]);
   const exitCode = await proc.exited;
   try {
     proc.stdin!.end();

packages/cli/src/gcp/gcp.ts

@@ -792,6 +792,11 @@ export async function waitForCloudInit(maxAttempts = 60): Promise<void> {
           ],
         },
       );
+      // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+      await Promise.all([
+        new Response(proc.stdout).text(),
+        new Response(proc.stderr).text(),
+      ]);
       if ((await proc.exited) === 0) {
         logInfo("Startup script completed");
         return;
@@ -868,7 +873,11 @@ export async function runServerCapture(cmd: string, timeoutSecs?: number): Promi
       proc.kill();
     } catch {}
   }, timeout);
-  const stdout = await new Response(proc.stdout).text();
+  // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+  const [stdout] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+  ]);
   const exitCode = await proc.exited;
   clearTimeout(timer);
   if (exitCode !== 0) {

packages/cli/src/hetzner/hetzner.ts

@@ -489,7 +489,11 @@ export async function waitForCloudInit(ip?: string, _maxAttempts = 60): Promise<
           ],
         },
       );
-      const stdout = await new Response(proc.stdout).text();
+      // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+      const [stdout] = await Promise.all([
+        new Response(proc.stdout).text(),
+        new Response(proc.stderr).text(),
+      ]);
       const exitCode = await proc.exited;
       if (exitCode === 0 && stdout.includes("done")) {
         logInfo("Cloud-init complete");
@@ -576,7 +580,11 @@ export async function runServerCapture(cmd: string, timeoutSecs?: number, ip?: s
       proc.kill();
     } catch {}
   }, timeout);
-  const stdout = await new Response(proc.stdout).text();
+  // Drain both pipes before awaiting exit to prevent pipe buffer deadlock
+  const [stdout] = await Promise.all([
+    new Response(proc.stdout).text(),
+    new Response(proc.stderr).text(),
+  ]);
   const exitCode = await proc.exited;
   try {
     proc.stdin!.end();