fix: preserve exec exit code after stream cancellation

cmd/bridge/server.go

@@ -361,7 +361,10 @@ func execPipe(stream pb.ContainerService_ExecServer, firstMsg *pb.ExecInput) err
 		timeout = defaultTimeout
 	}
 
-	ctx, cancel := context.WithTimeout(stream.Context(), time.Duration(timeout)*time.Second)
+	// Keep non-PTY execs alive across transport cancellation so a dropped
+	// stream does not rewrite a successful command into exit -1. The timeout
+	// still bounds command lifetime, and stream shutdown still closes stdin.
+	ctx, cancel := context.WithTimeout(context.WithoutCancel(stream.Context()), time.Duration(timeout)*time.Second)
 	defer cancel()
 
 	cmd := exec.CommandContext(ctx, "/bin/sh", "-c", command) //nolint:gosec // G204: MCP exec tool intentionally executes agent-issued shell commands inside the container

cmd/bridge/server_test.go

@@ -0,0 +1,79 @@
+package main
+
+import (
+	"context"
+	"testing"
+
+	"google.golang.org/grpc/metadata"
+
+	pb "github.com/memohai/memoh/internal/workspace/bridgepb"
+)
+
+type cancelOnStdoutExecStream struct {
+	ctx    context.Context
+	cancel context.CancelFunc
+
+	outputs  []*pb.ExecOutput
+	canceled bool
+}
+
+func newCancelOnStdoutExecStream() *cancelOnStdoutExecStream {
+	ctx, cancel := context.WithCancel(context.Background())
+	return &cancelOnStdoutExecStream{ctx: ctx, cancel: cancel}
+}
+
+func (s *cancelOnStdoutExecStream) Send(msg *pb.ExecOutput) error {
+	clone := *msg
+	if len(msg.GetData()) > 0 {
+		clone.Data = append([]byte(nil), msg.GetData()...)
+	}
+	s.outputs = append(s.outputs, &clone)
+	if !s.canceled && msg.GetStream() == pb.ExecOutput_STDOUT && len(msg.GetData()) > 0 {
+		s.canceled = true
+		s.cancel()
+	}
+	return nil
+}
+
+func (s *cancelOnStdoutExecStream) Recv() (*pb.ExecInput, error) {
+	<-s.ctx.Done()
+	return nil, s.ctx.Err()
+}
+
+func (s *cancelOnStdoutExecStream) Context() context.Context   { return s.ctx }
+func (*cancelOnStdoutExecStream) SetHeader(metadata.MD) error  { return nil }
+func (*cancelOnStdoutExecStream) SendHeader(metadata.MD) error { return nil }
+func (*cancelOnStdoutExecStream) SetTrailer(metadata.MD)       {}
+func (*cancelOnStdoutExecStream) SendMsg(any) error            { return nil }
+func (*cancelOnStdoutExecStream) RecvMsg(any) error            { return nil }
+
+func TestExecPipePreservesExitCodeAcrossStreamCancellation(t *testing.T) {
+	stream := newCancelOnStdoutExecStream()
+
+	err := execPipe(stream, &pb.ExecInput{
+		Command:        "printf ok; sleep 0.2",
+		WorkDir:        "/tmp",
+		TimeoutSeconds: 5,
+	})
+	if err != nil {
+		t.Fatalf("execPipe returned error: %v", err)
+	}
+
+	var stdout string
+	var exitCode int32 = -999
+	for _, output := range stream.outputs {
+		switch output.GetStream() {
+		case pb.ExecOutput_STDOUT:
+			stdout += string(output.GetData())
+		case pb.ExecOutput_EXIT:
+			exitCode = output.GetExitCode()
+		}
+	}
+
+	if stdout != "ok" {
+		t.Fatalf("stdout = %q, want %q", stdout, "ok")
+	}
+	if exitCode != 0 {
+		t.Fatalf("exit code = %d, want 0", exitCode)
+	}
+}