diff --git a/dockerimg/dockerimg.go b/dockerimg/dockerimg.go
index 18284b1..2ada9c6 100644
--- a/dockerimg/dockerimg.go
+++ b/dockerimg/dockerimg.go
@@ -809,11 +809,8 @@
 // We also set up fake temporary Go module(s) so we can run "go mod download".
 // TODO: maybe 'go list ./...' and then do a build as well to populate the build cache.
 // TODO: 'npm install', etc? We have the rails for it.
-// This is an ok compromise, but a power user might want
-// less caching or more caching, depending on their use case. One approach we could take
-// is to punt entirely if /app/.git already exists. If the user has provided a -base-image with
-// their git repo, let's assume they know what they're doing, and they've customized their image
-// for their use case.
+// If /app/.git already exists, we fetch from the existing repo instead of cloning.
+// This lets advanced users arrange their git repo exactly as they desire.
 // Note that buildx has some support for conditional COPY, but without buildx, which
 // we can't reliably depend on, we have to run the base image to inspect its file system,
 // and then we can decide what to do.
diff --git a/loop/agent.go b/loop/agent.go
index 1416ab6..c4fc52d 100644
--- a/loop/agent.go
+++ b/loop/agent.go
@@ -1124,11 +1124,20 @@
 
 	// If a remote + commit was specified, clone it.
 	if a.config.Commit != "" && a.gitState.gitRemoteAddr != "" {
-		slog.InfoContext(ctx, "cloning git repo", "commit", a.config.Commit)
-		// TODO: --reference-if-able instead?
-		cmd := exec.CommandContext(ctx, "git", "clone", "--reference", "/git-ref", a.gitState.gitRemoteAddr, "/app")
-		if out, err := cmd.CombinedOutput(); err != nil {
-			return fmt.Errorf("failed to clone repository from %s: %s: %w", a.gitState.gitRemoteAddr, out, err)
+		if _, err := os.Stat("/app/.git"); err == nil {
+			// Already a repo in /app.
+			// Make sure that the remote is configured correctly.
+			// We do a fetch below.
+			if err := upsertRemoteOrigin(ctx, "/app", a.gitState.gitRemoteAddr); err != nil {
+				return err
+			}
+		} else {
+			slog.InfoContext(ctx, "cloning git repo", "commit", a.config.Commit)
+			// TODO: --reference-if-able instead?
+			cmd := exec.CommandContext(ctx, "git", "clone", "--reference", "/git-ref", a.gitState.gitRemoteAddr, "/app")
+			if out, err := cmd.CombinedOutput(); err != nil {
+				return fmt.Errorf("failed to clone repository from %s: %s: %w", a.gitState.gitRemoteAddr, out, err)
+			}
 		}
 	}
 
@@ -2241,6 +2250,25 @@
 	return strings.TrimSpace(string(out)), nil
 }
 
+// upsertRemoteOrigin configures the origin remote to point to the given URL.
+// If the origin remote exists, it updates the URL. If it doesn't exist, it adds it.
+func upsertRemoteOrigin(ctx context.Context, repoDir, remoteURL string) error {
+	// Try to set the URL for existing origin remote
+	cmd := exec.CommandContext(ctx, "git", "remote", "set-url", "origin", remoteURL)
+	cmd.Dir = repoDir
+	if _, err := cmd.CombinedOutput(); err == nil {
+		// Success.
+		return nil
+	}
+	// Origin doesn't exist; add it.
+	cmd = exec.CommandContext(ctx, "git", "remote", "add", "origin", remoteURL)
+	cmd.Dir = repoDir
+	if out, err := cmd.CombinedOutput(); err != nil {
+		return fmt.Errorf("failed to add git remote origin: %s: %w", out, err)
+	}
+	return nil
+}
+
 func resolveRef(ctx context.Context, dir, refName string) (string, error) {
 	cmd := exec.CommandContext(ctx, "git", "rev-parse", refName)
 	stderr := new(strings.Builder)