feat: Resumable Download Helper and Manifest Preservation

- Route downloads through local cache directory
- Automatically resume interrupted downloads from the byte offset
- `setup_uninstaller_context` checks if a fail had happened. If yes then
  CLI preserves existing manifest instead of wiping it.
- Interruption Signal Traps and Prompts

.agents/skills/add_installer/SKILL.md

@@ -113,7 +113,9 @@ install_<name>() {
     # Use pkg_install for distro packages (it automatically handles rollback hooks!):
     #   pkg_install "arch:<pkg_a>|debian:<pkg_d>|fedora:<pkg_f>"
     
-    # Or manual downloads:
+    # Or manual downloads (always use download_file for resumability!):
+    #   local url="https://..."
+    #   download_file "$url" "$TMP_DIR/binary"
     #   cp "$TMP_DIR/binary" "$HOME/.local/bin/binary"
     #   track_file "$HOME/.local/bin/binary"  # Important for rollback!
 }
@@ -157,6 +159,7 @@ These are pre-loaded by `bootstrap.sh` — no need to source them manually in in
 | `confirm "prompt"` | Interactive yes/no prompt, returns 0 for yes |
 | `has_command <cmd>` | Check if a command exists (returns 0/1) |
 | `make_temp_dir` | Create and echo a temp directory path |
+| `download_file <url> <dest>` | Resumable and cached download of `<url>` to `<dest>`. Uses `~/.local/state/bootstrap/cache/`. |
 
 ### From `lib/platform.sh`
 
@@ -216,6 +219,21 @@ if [ -z "$latest_tag" ]; then
 fi
 ```
 
+### Resumable Download and Extraction
+
+```bash
+local url="https://github.com/owner/repo/releases/download/${version}/archive.tar.gz"
+local dest="$TMP_DIR/archive.tar.gz"
+
+# Resumable, cached download
+download_file "$url" "$dest"
+
+# Extract and install
+tar -xzf "$dest" -C "$TMP_DIR"
+sudo cp "$TMP_DIR/binary" /usr/local/bin/binary
+track_file "/usr/local/bin/binary"
+```
+
 ---
 
 ## Rules & Conventions

docs/rollback_design.md

@@ -105,3 +105,29 @@ Because `b ware <tool>` allows users to modify installation scripts:
 The `pkg_remove` helper utilizes reference counting via simple text files (e.g., `~/.local/state/bootstrap/packages/curl`). 
 - **On `pkg_install`**: Append tool name.
 - **On `pkg_remove`**: Remove tool name. If empty, proceed with system uninstallation.
+
+## 8. Fault Tolerance, Resumability, and Interrupted Installations
+
+To handle failures during installation (e.g., network drops, script errors, or user cancellation via `Ctrl+C`), the CLI incorporates a transactional approach that balances **automatic rollback** and **resumability**:
+
+### A. The Interruption Trap & Prompt
+When running an installer, the central router (`lib/routes.sh`) traps `SIGINT` and `SIGTERM` signals. If the installation fails or is interrupted:
+1. The trap catches the event and stops execution.
+2. The user is prompted interactively:
+   - **Rollback (r)**: Invokes `execute_rollback <tool>` immediately to clean up all partial modifications.
+   - **Keep (k)**: Preserves the partial changes and leaves the `.cmds` manifest intact.
+3. In non-interactive environments (e.g., CI/CD or scripts), the CLI defaults to **automatic rollback** to keep the system clean.
+
+### B. Resuming via Preserved Manifests
+If the user chooses to **keep** the partial state and runs `b <tool>` again:
+1. `setup_uninstaller_context` detects that a manifest already exists and that the tool was *not* successfully installed (no `INSTALL: <tool>` in the history log).
+2. It **preserves** the existing manifest instead of wiping it.
+3. As the script runs again from the top, new rollback commands are prepended to the existing manifest, maintaining the correct LIFO order without losing the tracking of previously completed steps.
+
+### C. Resumable Downloads (Caching Layer)
+To make rerunning an interrupted script fast and efficient, installers use `download_file <url> <dest>` instead of raw `curl`:
+1. It downloads the payload to a central cache directory: `~/.local/state/bootstrap/cache/`.
+2. It uses `curl -C -` to continue the download from the byte offset where it was interrupted.
+3. Once completed, it copies the cached file to the installer's temp directory.
+4. Distro package manager commands (`pkg_install`) and shell snippets (`write_env_snippet`) are naturally idempotent, allowing the script to breeze through already completed steps in milliseconds and resume exactly where the heavy work failed.
+

installers/install_agy.sh

@@ -96,7 +96,7 @@ install_agy() {
     fi
 
     log_info "Downloading release package..."
-        curl -fsSL "$url" -o "$staging_payload"
+    download_file "$url" "$staging_payload"
 
     # Verify SHA512 Checksum
     local actual_hash

installers/install_asciicinema.sh

@@ -76,7 +76,7 @@ install_asciicinema() {
     local download_url="https://github.com/asciinema/asciinema/releases/download/${latest_tag}/asciinema-${asciinema_arch}"
     
     log_info "Downloading asciinema ${latest_tag} for ${arch}..."
-    curl -fsSL "$download_url" -o "$TMP_DIR/asciinema"
+    download_file "$download_url" "$TMP_DIR/asciinema"
 
     log_info "Installing asciinema to /usr/local/bin..."
     sudo cp "$TMP_DIR/asciinema" /usr/local/bin/asciinema

installers/install_bat.sh

@@ -63,7 +63,7 @@ install_bat() {
 
         local deb_url="https://github.com/sharkdp/bat/releases/download/${latest_tag}/bat_${version}_${deb_arch}.deb"
         log_info "Downloading Bat from ${deb_url}..."
-            curl -fsSL "$deb_url" -o "$TMP_DIR/bat.deb"
+        download_file "$deb_url" "$TMP_DIR/bat.deb"
 
         log_info "Installing Bat package..."
         sudo apt install -y "$TMP_DIR/bat.deb"

installers/install_node.sh

@@ -45,8 +45,7 @@ install_nvm() {
 
     local nvm_url="https://github.com/nvm-sh/nvm/archive/refs/tags/${latest_tag}.tar.gz"
     log_info "Downloading NVM from $nvm_url..."
-
-        curl -fsSL "$nvm_url" -o "$TMP_DIR/nvm.tar.gz"
+    download_file "$nvm_url" "$TMP_DIR/nvm.tar.gz"
 
     log_info "Extracting NVM archive directly to $HOME/.nvm (stripping versioned subfolder to keep config generic)..."
     mkdir -p "$HOME/.nvm"

installers/install_nvim.sh

@@ -79,7 +79,7 @@ install_nvim() {
     local nvim_url="https://github.com/neovim/neovim/releases/download/v${NVIM_VERSION}/nvim-${nvim_arch}.tar.gz"
 
     log_info "Downloading Neovim v${NVIM_VERSION} for ${arch}..."
-        curl -fsSL "$nvim_url" -o "$TMP_DIR/nvim.tar.gz"
+    download_file "$nvim_url" "$TMP_DIR/nvim.tar.gz"
 
     tar -xzf "$TMP_DIR/nvim.tar.gz" -C "$TMP_DIR"
 

installers/install_pnpm.sh

@@ -34,7 +34,11 @@ trap cleanup EXIT
 # ─── Helper Functions ─────────────────────────────────────────────────
 
 download() {
+    if [ -n "${2:-}" ]; then
+        download_file "$1" "$2"
+    else
         curl -fsSL "$1"
+    fi
 }
 
 is_glibc_compatible() {
@@ -147,7 +151,7 @@ install_pnpm() {
 
     if [ "$major_version" -ge 11 ]; then
         # v11+: distributed as tarballs containing the binary and dist/ directory
-        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}.tar.gz" > "$TMP_DIR/pnpm.tar.gz" || {
+        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}.tar.gz" "$TMP_DIR/pnpm.tar.gz" || {
             log_error "Failed to download pnpm tarball."
             return 1
         }
@@ -162,7 +166,7 @@ install_pnpm() {
         }
     else
         # Older versions: distributed as a single executable binary
-        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}" > "$TMP_DIR/pnpm" || {
+        download "https://github.com/pnpm/pnpm/releases/download/v${version}/${asset_base}" "$TMP_DIR/pnpm" || {
             log_error "Failed to download pnpm binary."
             return 1
         }

installers/install_rust.sh

@@ -76,7 +76,7 @@ install_rust() {
     local dest="$TMP_DIR/rustup-init"
 
     log_info "Downloading rustup-init..."
-    curl -fsSL "$url" -o "$dest"
+    download_file "$url" "$dest"
 
     chmod +x "$dest"
 

installers/install_starship.sh

@@ -59,7 +59,7 @@ install_starship() {
 
     log_info "Downloading Starship from ${download_url}..."
     local archive="$TMP_DIR/starship.tar.gz"
-        curl -fsSL "$download_url" -o "$archive"
+    download_file "$download_url" "$archive"
 
     # Extract the binary
     log_info "Extracting Starship binary..."

installers/install_uv.sh

@@ -68,7 +68,7 @@ install_uv() {
 
     log_info "Downloading uv from ${download_url}..."
     local archive="$TMP_DIR/uv.tar.gz"
-        curl -fsSL "$download_url" -o "$archive"
+    download_file "$download_url" "$archive"
 
     # Extract the binaries
     log_info "Extracting uv binaries..."

installers/install_yazi.sh

@@ -76,7 +76,7 @@ install_yazi() {
 
         local deb_url="https://github.com/sxyazi/yazi/releases/download/${latest_tag}/yazi-x86_64-unknown-linux-gnu.deb"
         log_info "Downloading Yazi ${latest_tag} from ${deb_url}..."
-            curl -fsSL "$deb_url" -o "$TMP_DIR/yazi.deb"
+        download_file "$deb_url" "$TMP_DIR/yazi.deb"
 
         log_info "Installing Yazi package..."
         sudo apt install -y "$TMP_DIR/yazi.deb"

lib/common.sh

@@ -84,9 +84,46 @@ version_lt() {
     done
     return 1
 }
+# Cached and resumable download helper
+download_file() {
+    local url="$1"
+    local dest="$2"
+    local cache_dir="$HOME/.local/state/bootstrap/cache"
+    
+    mkdir -p "$cache_dir"
+    
+    local safe_name
+    if has_command md5sum; then
+        safe_name=$(echo -n "$url" | md5sum | cut -d' ' -f1)
+    elif has_command shasum; then
+        safe_name=$(echo -n "$url" | shasum | cut -d' ' -f1)
+    else
+        safe_name=$(echo -n "$url" | tr -c '[:alnum:]_.-' '_')
+    fi
+    
+    local base_name
+    base_name=$(basename "$url")
+    local cache_file="$cache_dir/${safe_name}_${base_name}"
+    
+    log_info "Downloading $base_name (resumable)..."
+    if ! curl -fL -C - "$url" -o "$cache_file"; then
+        local exit_code=$?
+        # Exit code 33: HTTP server doesn't support ranges/resuming
+        # Exit code 36: Bad download resume offset
+        if [ $exit_code -eq 33 ] || [ $exit_code -eq 36 ]; then
+            log_warn "Server does not support resuming. Retrying from scratch..."
+            rm -f "$cache_file"
+            curl -fL "$url" -o "$cache_file" || return 1
+        else
+            return $exit_code
+        fi
+    fi
+    
+    mkdir -p "$(dirname "$dest")"
+    cp "$cache_file" "$dest"
+}
 
 # Export functions and variables for subshells
 export _LIB_COMMON_SOURCED=1
 export RED GREEN YELLOW BLUE NC
-export -f require_bash log_info log_success log_warn log_error confirm has_command make_temp_dir version_lt
-
+export -f require_bash log_info log_success log_warn log_error confirm has_command make_temp_dir version_lt download_file

lib/rollback.sh

@@ -20,8 +20,16 @@ setup_uninstaller_context() {
     local tool="$1"
     export BOOTSTRAP_CURRENT_TOOL="$tool"
     export BOOTSTRAP_UNINSTALLER_CMDS="$BOOTSTRAP_UNINSTALLERS_DIR/${tool}.cmds"
-    # Ensure fresh manifest for this run
-    rm -f "$BOOTSTRAP_UNINSTALLER_CMDS"
+    
+    # If a manifest already exists and the tool is NOT marked as successfully installed
+    # in history.log, we treat this as a resumed run. We preserve the manifest so
+    # that new commands are prepended to the existing ones.
+    if [ -f "$BOOTSTRAP_UNINSTALLER_CMDS" ] && ! grep -q "^INSTALL: $tool$" "$BOOTSTRAP_HISTORY_LOG" 2>/dev/null; then
+        log_info "Resuming installation of '$tool'. Preserving existing rollback manifest."
+    else
+        # Fresh installation or reinstall, start with a clean slate
+        rm -f "$BOOTSTRAP_UNINSTALLER_CMDS"
+    fi
     touch "$BOOTSTRAP_UNINSTALLER_CMDS"
 }
 

lib/routes.sh

@@ -114,11 +114,54 @@ run_ware() {
     # Run the script (edited or unchanged)
     log_info "Running ${display_name} installer..."
     setup_uninstaller_context "$tool"
+    
+    # Set trap for signals to intercept interruption and allow user to choose rollback/keep
+    local interrupted=false
+    trap 'interrupted=true' INT TERM
+    
     bash "$temp_script" "${cmd_args[@]}"
     local run_status=$?
     
-    if [ "$run_status" -eq 0 ]; then
+    # Restore default traps
+    trap - INT TERM
+    
+    if [ "$run_status" -eq 0 ] && [ "$interrupted" = "false" ]; then
         mark_install_success "$tool"
+    else
+        echo
+        if [ "$interrupted" = "true" ]; then
+            log_error "Installation of ${display_name} was interrupted."
+            run_status=130
+        else
+            log_error "Installation of ${display_name} failed with exit code $run_status."
+        fi
+        
+        local choice=""
+        if [ -t 0 ]; then
+            while true; do
+                read -r -p "Would you like to [r]ollback partial changes, or [k]eep them to resume/debug later? (r/k): " choice </dev/tty || choice="r"
+                case "$choice" in
+                    [Rr]*)
+                        execute_rollback "$tool"
+                        run_status=1
+                        break
+                        ;;
+                    [Kk]*)
+                        log_info "Keeping partial changes. Run 'b ${tool}' again to resume."
+                        run_status=1
+                        break
+                        ;;
+                    *)
+                        echo "Invalid choice. Please enter 'r' or 'k'."
+                        ;;
+                esac
+            done
+        else
+            # Non-interactive environment, default to safe rollback
+            log_warn "Non-interactive shell detected. Defaulting to automatic rollback to keep system clean."
+            execute_rollback "$tool"
+            run_status=1
+        fi
     fi
     
     # Cleanup