Add mcp logs command for streaming container logs

New server-streaming Logs RPC streams container output to the CLI.
Supports --tail/-n, --follow/-f, --timestamps/-t, --since.

Detects journald log driver and falls back to journalctl (podman logs
can't read journald outside the originating user session). New containers
default to k8s-file via mcp user's containers.conf.

Also adds stream auth interceptor for the agent gRPC server (required
for streaming RPCs).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/agent/agent.go

@@ -100,6 +100,9 @@ func Run(cfg *config.AgentConfig) error {
 		grpc.ChainUnaryInterceptor(
 			auth.AuthInterceptor(validator),
 		),
+		grpc.ChainStreamInterceptor(
+			auth.StreamAuthInterceptor(validator),
+		),
 	)
 	mcpv1.RegisterMcpAgentServiceServer(server, a)
 

internal/agent/logs.go

@@ -0,0 +1,75 @@
+package agent
+
+import (
+	"bufio"
+	"io"
+
+	mcpv1 "git.wntrmute.dev/mc/mcp/gen/mcp/v1"
+	"git.wntrmute.dev/mc/mcp/internal/registry"
+	"git.wntrmute.dev/mc/mcp/internal/runtime"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// Logs streams container logs for a service component.
+func (a *Agent) Logs(req *mcpv1.LogsRequest, stream mcpv1.McpAgentService_LogsServer) error {
+	if req.GetService() == "" {
+		return status.Error(codes.InvalidArgument, "service name is required")
+	}
+
+	// Resolve component name.
+	component := req.GetComponent()
+	if component == "" {
+		components, err := registry.ListComponents(a.DB, req.GetService())
+		if err != nil {
+			return status.Errorf(codes.Internal, "list components: %v", err)
+		}
+		if len(components) == 0 {
+			return status.Error(codes.NotFound, "no components found for service")
+		}
+		component = components[0].Name
+	}
+
+	containerName := ContainerNameFor(req.GetService(), component)
+
+	podman, ok := a.Runtime.(*runtime.Podman)
+	if !ok {
+		return status.Error(codes.Internal, "logs requires podman runtime")
+	}
+
+	cmd := podman.Logs(stream.Context(), containerName, int(req.GetTail()), req.GetFollow(), req.GetTimestamps(), req.GetSince())
+
+	a.Logger.Info("running podman logs", "container", containerName, "args", cmd.Args)
+
+	// Podman writes container stdout to its stdout and container stderr
+	// to its stderr. Merge both into a single pipe.
+	pr, pw := io.Pipe()
+	cmd.Stdout = pw
+	cmd.Stderr = pw
+
+	if err := cmd.Start(); err != nil {
+		pw.Close()
+		return status.Errorf(codes.Internal, "start podman logs: %v", err)
+	}
+
+	// Close the write end when the command exits so the scanner finishes.
+	go func() {
+		err := cmd.Wait()
+		if err != nil {
+			a.Logger.Warn("podman logs exited", "container", containerName, "error", err)
+		}
+		pw.Close()
+	}()
+
+	scanner := bufio.NewScanner(pr)
+	for scanner.Scan() {
+		if err := stream.Send(&mcpv1.LogsResponse{
+			Data: append(scanner.Bytes(), '\n'),
+		}); err != nil {
+			_ = cmd.Process.Kill()
+			return err
+		}
+	}
+
+	return nil
+}

internal/auth/auth.go

@@ -255,6 +255,52 @@ func AuthInterceptor(validator TokenValidator) grpc.UnaryServerInterceptor {
 	}
 }
 
+// StreamAuthInterceptor returns a gRPC stream server interceptor with
+// the same authentication rules as AuthInterceptor.
+func StreamAuthInterceptor(validator TokenValidator) grpc.StreamServerInterceptor {
+	return func(
+		srv any,
+		ss grpc.ServerStream,
+		info *grpc.StreamServerInfo,
+		handler grpc.StreamHandler,
+	) error {
+		md, ok := metadata.FromIncomingContext(ss.Context())
+		if !ok {
+			return status.Error(codes.Unauthenticated, "missing metadata")
+		}
+
+		authValues := md.Get("authorization")
+		if len(authValues) == 0 {
+			return status.Error(codes.Unauthenticated, "missing authorization header")
+		}
+
+		authHeader := authValues[0]
+		if !strings.HasPrefix(authHeader, "Bearer ") {
+			return status.Error(codes.Unauthenticated, "malformed authorization header")
+		}
+		token := strings.TrimPrefix(authHeader, "Bearer ")
+
+		tokenInfo, err := validator.ValidateToken(ss.Context(), token)
+		if err != nil {
+			slog.Error("token validation failed", "method", info.FullMethod, "error", err)
+			return status.Error(codes.Unauthenticated, "token validation failed")
+		}
+
+		if !tokenInfo.Valid {
+			return status.Error(codes.Unauthenticated, "invalid token")
+		}
+
+		if tokenInfo.HasRole("guest") {
+			slog.Warn("guest access denied", "method", info.FullMethod, "user", tokenInfo.Username)
+			return status.Error(codes.PermissionDenied, "guest access not permitted")
+		}
+
+		slog.Info("rpc", "method", info.FullMethod, "user", tokenInfo.Username, "account_type", tokenInfo.AccountType)
+
+		return handler(srv, ss)
+	}
+}
+
 // Login authenticates with MCIAS and returns a bearer token.
 func Login(serverURL, caCertPath, username, password string) (string, error) {
 	client, err := newHTTPClient(caCertPath)

internal/runtime/podman.go

@@ -178,6 +178,49 @@ func (p *Podman) Inspect(ctx context.Context, name string) (ContainerInfo, error
 	return info, nil
 }
 
+// Logs returns an exec.Cmd that streams container logs. For containers
+// using the journald log driver, it uses journalctl (podman logs can't
+// read journald outside the originating user session). For k8s-file or
+// other drivers, it uses podman logs directly.
+func (p *Podman) Logs(ctx context.Context, containerName string, tail int, follow, timestamps bool, since string) *exec.Cmd {
+	// Check if this container uses the journald log driver.
+	inspectCmd := exec.CommandContext(ctx, p.command(), "inspect", "--format", "{{.HostConfig.LogConfig.Type}}", containerName) //nolint:gosec
+	if out, err := inspectCmd.Output(); err == nil && strings.TrimSpace(string(out)) == "journald" {
+		return p.journalLogs(ctx, containerName, tail, follow, since)
+	}
+
+	args := []string{"logs"}
+	if tail > 0 {
+		args = append(args, "--tail", fmt.Sprintf("%d", tail))
+	}
+	if follow {
+		args = append(args, "--follow")
+	}
+	if timestamps {
+		args = append(args, "--timestamps")
+	}
+	if since != "" {
+		args = append(args, "--since", since)
+	}
+	args = append(args, containerName)
+	return exec.CommandContext(ctx, p.command(), args...) //nolint:gosec // args built programmatically
+}
+
+// journalLogs returns a journalctl command filtered by container name.
+func (p *Podman) journalLogs(ctx context.Context, containerName string, tail int, follow bool, since string) *exec.Cmd {
+	args := []string{"--no-pager", "--output", "cat", "CONTAINER_NAME=" + containerName}
+	if tail > 0 {
+		args = append(args, "--lines", fmt.Sprintf("%d", tail))
+	}
+	if follow {
+		args = append(args, "--follow")
+	}
+	if since != "" {
+		args = append(args, "--since", since)
+	}
+	return exec.CommandContext(ctx, "journalctl", args...) //nolint:gosec // args built programmatically
+}
+
 // Login authenticates to a container registry using the given token as
 // the password. This enables non-interactive push with service account
 // tokens (MCR accepts MCIAS JWTs as passwords).