feat: auto-build hawk image on first run (no fallback to bare ubuntu)

Author: Patel230

cmd/container_boot.go

@@ -3,7 +3,10 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"os"
 	"os/exec"
+	"path/filepath"
+	"runtime"
 	"time"
 
 	tea "github.com/charmbracelet/bubbletea"
@@ -19,6 +22,40 @@ type containerStatusMsg struct {
 	sandbox *sandbox.ContainerSandbox
 }
 
+// buildHawkImage builds the hawk container image from the bundled Dockerfile.
+// It writes the Dockerfile to a temp dir and runs docker build.
+func buildHawkImage(ctx context.Context, tag string) bool {
+	dockerfile := `FROM ubuntu:24.04
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    git curl wget jq tree ripgrep fd-find make gcc \
+    python3 python3-pip nodejs npm ca-certificates openssh-client \
+    && rm -rf /var/lib/apt/lists/* \
+    && ln -sf /usr/bin/fdfind /usr/bin/fd
+ENV TERM=xterm-256color LANG=C.UTF-8
+`
+	// Use platform-appropriate arch
+	platform := runtime.GOARCH
+	if platform == "arm64" {
+		platform = "linux/arm64"
+	} else {
+		platform = "linux/amd64"
+	}
+
+	tmpDir, err := os.MkdirTemp("", "hawk-build-")
+	if err != nil {
+		return false
+	}
+	defer os.RemoveAll(tmpDir)
+
+	dfPath := filepath.Join(tmpDir, "Dockerfile")
+	if err := os.WriteFile(dfPath, []byte(dockerfile), 0644); err != nil {
+		return false
+	}
+
+	cmd := exec.CommandContext(ctx, "docker", "build", "--platform", platform, "-t", tag, "-f", dfPath, tmpDir)
+	return cmd.Run() == nil
+}
+
 // shouldUseContainer determines if hawk should run in container mode.
 // Default: YES if Docker is available (like herm). User can override with --no-container.
 func shouldUseContainer() bool {
@@ -45,17 +82,23 @@ func bootContainerCmd(projectDir string) tea.Cmd {
 			}
 		}
 
-		// Ensure image exists locally, pull if needed (like herm)
+		// Ensure image exists locally — pull or build as needed (like herm)
 		image := cs.Image()
-		pullCtx, pullCancel := context.WithTimeout(context.Background(), 300*time.Second)
-		defer pullCancel()
-		checkCmd := exec.CommandContext(pullCtx, "docker", "image", "inspect", image)
+		imgCtx, imgCancel := context.WithTimeout(context.Background(), 300*time.Second)
+		defer imgCancel()
+		checkCmd := exec.CommandContext(imgCtx, "docker", "image", "inspect", image)
 		if checkCmd.Run() != nil {
-			// Image not available locally — pull it
-			pullCmd := exec.CommandContext(pullCtx, "docker", "pull", image)
-			if err := pullCmd.Run(); err != nil {
-				// Fall back to ubuntu:24.04 if custom image can't be pulled
-				cs.SetImage("ubuntu:24.04")
+			// Image not available locally — try pull first
+			pullCmd := exec.CommandContext(imgCtx, "docker", "pull", image)
+			if pullCmd.Run() != nil {
+				// Pull failed — build from bundled Dockerfile
+				built := buildHawkImage(imgCtx, image)
+				if !built {
+					return containerStatusMsg{
+						status: "image build failed",
+						err:    fmt.Errorf("could not pull or build %s", image),
+					}
+				}
 			}
 		}