Install opencode in Void rootfs

Bring the experimental Void image closer to the default dev image path by installing pinned mise inside the rootfs build, using it to install opencode, and activating mise automatically for root bash sessions.

Keep the change scoped to the Void builder rather than packages.void so the image still stays language-agnostic at the package-manifest level, then clean mise download/cache artifacts before sealing the rootfs and work-seed.

Extend verify-void so the smoke path now proves mise and opencode are actually present in a fresh void-exp VM. Verified with bash -n make-rootfs-void.sh verify.sh, GOCACHE=/tmp/banger-gocache go test ./..., and make build.

AGENTS.md

@@ -36,7 +36,7 @@
 - Manual verification for VM lifecycle changes: `./banger vm create`, confirm SSH access, then stop/delete the VM.
 - For host-integration changes, run `./banger doctor` as a quick readiness check before the live VM smoke.
 - Rebuilt images now include `mise`, `opencode`, `tmux-resurrect`/`tmux-continuum` defaults for `root`, and the `banger-vsock-agent` service used by the SSH reminder and guest health-check path; if you change guest provisioning, document whether users need to rebuild `./runtime/rootfs-docker.ext4` or another base image to pick it up.
-- The experimental Void rootfs path now includes the repo's basic dev baseline plus Docker and Compose, alongside boot, SSH, the vsock HTTP health agent, a `bash` root shell while leaving `/bin/sh` alone, and the `/root` work-seed. Keep further baked-in tooling deliberate and user-driven.
+- The experimental Void rootfs path now includes the repo's basic dev baseline plus Docker and Compose, alongside boot, SSH, the vsock HTTP health agent, pinned `mise` plus `opencode` for `root`, a `bash` root shell while leaving `/bin/sh` alone, and the `/root` work-seed. Keep further baked-in tooling deliberate and user-driven.
 - Rebuilt images also emit a `work-seed.ext4` sidecar used to speed up future VM creates. If you touch `/root` provisioning, verify both the rootfs and the work-seed output.
 - The daemon may keep idle TAP devices in a pool for faster creates. Smoke tests should treat `tap-pool-*` devices as reusable capacity, not cleanup leaks.
 - If you add a new operational workflow, document how to exercise it in `README.md`.

README.md

@@ -325,6 +325,8 @@ This path is intentionally local-only and does not change the default Debian
 image flow. It reuses the current runtime bundle kernel, initrd, and modules,
 but builds a lean `x86_64-glibc` Void userspace with:
 - `bash` installed for interactive/admin use
+- pinned `mise` installed at `/usr/local/bin/mise`, activated for `root` bash shells
+- `opencode` installed through `mise`, with `/usr/local/bin/opencode` available by default
 - `docker` plus `docker-compose` installed from Void packages
 - the `docker` runit service enabled, with Docker netfilter/forwarding kernel prep
 - `openssh` enabled under runit
@@ -332,9 +334,7 @@ but builds a lean `x86_64-glibc` Void userspace with:
 - `root` normalized to `/bin/bash` while keeping `/bin/sh` as the distro's system shell
 - a generated `/root` work-seed for fast creates
 
-It does not install the Debian-oriented extras from rebuilt default images:
-- no `mise`
-- no `opencode`
+It still keeps some Debian-oriented extras out for now:
 - no tmux plugin defaults
 
 The builder fetches official static XBPS tools and packages from the Void

make-rootfs-void.sh

@@ -260,6 +260,11 @@ case "$-" in
   *) return ;;
 esac
 
+if [ -z "${BANGER_MISE_ACTIVATED:-}" ] && [ -x '/usr/local/bin/mise' ]; then
+  export BANGER_MISE_ACTIVATED=1
+  eval "$(/usr/local/bin/mise activate bash)"
+fi
+
 PS1='\u@\h:\w\$ '
 EOF
   cat <<'EOF' | sudo tee "$bash_profile" >/dev/null
@@ -280,6 +285,38 @@ EOF
   sudo chmod 0644 "$bashrc" "$bash_profile" "$profile_prompt"
 }
 
+install_mise_and_opencode() {
+  local profile_mise="$ROOT_MOUNT/etc/profile.d/mise.sh"
+
+  sudo mkdir -p "$ROOT_MOUNT/etc/profile.d"
+  if [[ -r /etc/resolv.conf ]]; then
+    sudo install -m 0644 /etc/resolv.conf "$ROOT_MOUNT/etc/resolv.conf"
+  fi
+
+  sudo env \
+    HOME=/root \
+    PATH=/usr/local/bin:/usr/bin:/bin \
+    chroot "$ROOT_MOUNT" /bin/bash -se <<EOF
+set -euo pipefail
+curl -fsSL https://mise.run | MISE_INSTALL_PATH="$MISE_INSTALL_PATH" MISE_VERSION="$MISE_VERSION" sh
+"$MISE_INSTALL_PATH" use -g "$OPENCODE_TOOL"
+"$MISE_INSTALL_PATH" reshim
+if [[ ! -e /root/.local/share/mise/shims/opencode ]]; then
+  echo "opencode shim not found after mise install" >&2
+  exit 1
+fi
+ln -snf /root/.local/share/mise/shims/opencode /usr/local/bin/opencode
+EOF
+
+  cat <<'EOF' | sudo tee "$profile_mise" >/dev/null
+if [ -n "${BASH_VERSION:-}" ] && [ -z "${BANGER_MISE_ACTIVATED:-}" ] && [ -x '/usr/local/bin/mise' ]; then
+  export BANGER_MISE_ACTIVATED=1
+  eval "$(/usr/local/bin/mise activate bash)"
+fi
+EOF
+  sudo chmod 0644 "$profile_mise"
+}
+
 cleanup() {
   if [[ -n "${ROOT_MOUNT:-}" ]] && command -v mountpoint >/dev/null 2>&1 && mountpoint -q "$ROOT_MOUNT"; then
     sudo umount "$ROOT_MOUNT" || true
@@ -313,6 +350,9 @@ OUT_ROOTFS="$RUNTIME_DIR/rootfs-void.ext4"
 SIZE_SPEC="2G"
 MIRROR="https://repo-default.voidlinux.org"
 ARCH="x86_64"
+MISE_VERSION="v2025.12.0"
+MISE_INSTALL_PATH="/usr/local/bin/mise"
+OPENCODE_TOOL="github:anomalyco/opencode"
 MODULES_DIR="$(bundle_path default_modules_dir "$RUNTIME_DIR/wtf/root/lib/modules/6.8.0-94-generic")"
 VSOCK_AGENT="$(bundle_path vsock_agent_path "$RUNTIME_DIR/banger-vsock-agent")"
 if [[ "$VSOCK_AGENT" == "$RUNTIME_DIR/banger-vsock-agent" && ! -x "$VSOCK_AGENT" ]]; then
@@ -474,6 +514,8 @@ configure_docker_bootstrap
 enable_docker_service
 normalize_root_shell
 configure_root_bash_prompt
+log "installing mise and opencode"
+install_mise_and_opencode
 sudo mkdir -p "$ROOT_MOUNT/root/.ssh"
 sudo touch "$ROOT_MOUNT/etc/fstab" "$ROOT_MOUNT/etc/hostname"
 sudo chroot "$ROOT_MOUNT" /usr/bin/ssh-keygen -A
@@ -487,8 +529,13 @@ sudo rm -rf \
 sudo rm -f \
   "$ROOT_MOUNT/root/get-docker" \
   "$ROOT_MOUNT/root/get-docker.sh" \
+  "$ROOT_MOUNT/root/.cache/opencode" \
   "$ROOT_MOUNT/tmp/get-docker" \
   "$ROOT_MOUNT/tmp/get-docker.sh"
+sudo rm -rf \
+  "$ROOT_MOUNT/root/.cache/mise" \
+  "$ROOT_MOUNT/root/.local/share/mise/downloads" \
+  "$ROOT_MOUNT/root/.local/share/mise/tmp"
 
 sudo umount "$ROOT_MOUNT"
 

verify.sh

@@ -240,6 +240,11 @@ if ! wait_for_ssh "$GUEST_IP" "$BOOT_DEADLINE"; then
 fi
 ssh "${SSH_COMMON_ARGS[@]}" "root@${GUEST_IP}" "uname -a" >/dev/null
 
+if [[ "$IMAGE_NAME" == "void-exp" ]]; then
+  log "asserting mise and opencode are available in the Void guest"
+  ssh "${SSH_COMMON_ARGS[@]}" "root@${GUEST_IP}" "command -v mise >/dev/null 2>&1 && command -v opencode >/dev/null 2>&1 && mise --version >/dev/null 2>&1 && opencode --version >/dev/null 2>&1" >/dev/null
+fi
+
 if (( NAT_ENABLED )); then
   log "asserting VM has outbound network access"
   ssh "${SSH_COMMON_ARGS[@]}" "root@${GUEST_IP}" "curl -fsS https://example.com >/dev/null" >/dev/null