Add configurable parallel screenshot rendering

README.md

@@ -13,7 +13,7 @@
 
 - **🔄 Live Editing** - Real-time screenshot regeneration when config or assets change
 - **🖥️ Live Preview Dashboard** - Auto-open a local dashboard for screenshot previews with hot reload
-- **🧩 HTML/CSS Templates** - Render polished marketing layouts with Chrome or Playwright Chromium
+- **🧩 HTML/CSS Templates** - Render polished marketing layouts with Playwright Chromium
 - **🌍 Multi-Language Localization** - Generate localized screenshots using familiar xcstrings format from Xcode
 - **🖼️ Localized Assets** - Automatic language-specific asset resolution with convention-based and explicit mapping
 - **🎨 100+ Device Frames** - iPhone 16 Pro, iPad Air M2, MacBook Pro, Apple Watch Ultra, and more
@@ -47,7 +47,7 @@ brew install bitomule/tap/koubou
 kou setup-html
 ```
 
-If Google Chrome is already installed, HTML template rendering usually works without any extra setup. `kou setup-html` installs Playwright Chromium only when it is needed.
+Koubou uses Playwright Chromium for all HTML rendering. `kou generate` and `kou live` install it automatically on first use for HTML projects, and `kou setup-html` is available when you want to preflight the environment explicitly.
 
 **Python Developers**
 ```bash
@@ -91,9 +91,6 @@ kou --create-config my-html-screenshots.yaml --mode html
 # Generate screenshots
 kou generate my-screenshots.yaml
 
-# Prepare HTML rendering if your project uses HTML templates
-kou setup-html
-
 # Inspect real frame geometry before designing HTML layouts
 kou inspect-frame "iPhone 16 Pro - Black Titanium - Portrait" --output-size iPhone6_9
 
@@ -104,7 +101,7 @@ kou live my-screenshots.yaml
 kou install-skills
 ```
 
-`kou --create-config` also creates sample PNG assets in a sibling `screenshots/` directory, so the generated YAML can be rendered immediately. In `--mode html`, it also creates sample templates in `templates/` and the generated project is ready to run with `kou generate ... --setup-html`.
+`kou --create-config` also creates sample PNG assets in a sibling `screenshots/` directory, so the generated YAML can be rendered immediately. In `--mode html`, it also creates sample templates in `templates/` and the generated project is ready to run with `kou generate ...`.
 
 ## 🧩 HTML Templates
 
@@ -122,8 +119,9 @@ screenshots:
 
 - `variables:` are localizable `{{key}}` substitutions
 - `assets:` are file-path substitutions exposed to the template as `{{key}}`
-- `kou generate config.yaml --setup-html` prepares HTML rendering and generates in one run
-- `kou live config.yaml --setup-html` does the same before starting live mode
+- `kou generate config.yaml` prepares Playwright Chromium automatically when HTML templates are present
+- `kou generate config.yaml --parallel-workers 4` renders multiple screenshots concurrently
+- `kou live config.yaml` does the same before starting live mode
 - `kou inspect-frame "<device>" --output-size <size> --output json` exposes frame and screen geometry for layout decisions
 
 ### Compact Layout JSON
@@ -260,6 +258,7 @@ project:
   output_dir: "Screenshots/Generated"
   device: "iPhone 15 Pro Portrait"
   output_size: "iPhone6_9"
+  parallel_workers: 4  # Optional - render up to 4 screenshots concurrently
 
 localization:
   base_language: "en"
@@ -470,14 +469,18 @@ See the YAML API Reference below for all available options including gradients,
 # Emit machine-readable results
 kou generate config.yaml --output json
 
-# Prepare HTML rendering and generate in one run
-kou generate config.yaml --setup-html
+# Override the worker count for this run
+kou generate config.yaml --parallel-workers 4
+
+# Generate HTML screenshots and auto-install Playwright Chromium on first run
+kou generate config.yaml
 
 # Enable verbose logging
 kou generate config.yaml --verbose
 ```
 
 For HTML screenshots, `--output json` includes `layout_path` alongside the PNG path so tooling can open the measured layout sidecar directly.
+Set `project.parallel_workers` in YAML when you want the same concurrency level to apply to every run.
 
 #### HTML Setup
 ```bash
@@ -521,8 +524,8 @@ kou inspect-frame "iPhone 16 Pro - Black Titanium - Portrait" --output-size 1200
 # Start live editing with default settings
 kou live config.yaml
 
-# Prepare HTML rendering before starting live mode
-kou live config.yaml --setup-html
+# Start live mode and auto-install Playwright Chromium on first run
+kou live config.yaml
 
 # Adjust debounce delay (default: 0.5s)
 kou live config.yaml --debounce 1.0

src/koubou/cli.py

@@ -21,8 +21,6 @@
 from .generator import ScreenshotGenerator
 from .html_preview import HtmlPreviewServer
 from .html_setup import (
-    check_html_environment,
-    format_html_environment_error,
     setup_html_environment,
 )
 from .live_generator import LiveScreenshotGenerator
@@ -105,7 +103,7 @@ def _create_config_file_with_mode(
         )
     console.print("\nEdit the configuration file and run:", style="blue")
     if normalized_mode == "html":
-        console.print(f"   kou generate {output_file} --setup-html", style="cyan")
+        console.print(f"   kou generate {output_file}", style="cyan")
     else:
         console.print(f"   kou generate {output_file}", style="cyan")
 
@@ -546,21 +544,15 @@ def _prepare_html_environment(
     verbose: bool,
     output_console: Console,
 ) -> None:
-    if setup_requested:
-        status = setup_html_environment(verbose=verbose)
-        if status.did_install_browser:
-            output_console.print(
-                f"HTML ready: installed {status.browser_name}", style="green"
-            )
-        else:
-            output_console.print(
-                f"HTML ready: using {status.browser_name}", style="green"
-            )
+    status = setup_html_environment(verbose=verbose)
+    if status.did_install_browser:
+        output_console.print(
+            f"HTML ready: installed {status.browser_name}", style="green"
+        )
         return
 
-    status = check_html_environment()
-    if not status.ready:
-        raise KoubouError(format_html_environment_error(status))
+    if setup_requested:
+        output_console.print(f"HTML ready: using {status.browser_name}", style="green")
 
 
 def _parse_output_size_option(value: str) -> Tuple[int, int]:
@@ -703,10 +695,19 @@ def generate(
     output: str = typer.Option(
         "table", "--output", help="Output format: table or json"
     ),
+    parallel_workers: int = typer.Option(
+        None,
+        "--parallel-workers",
+        min=1,
+        help="Override the number of screenshots rendered concurrently",
+    ),
     setup_html: bool = typer.Option(
         False,
         "--setup-html",
-        help="Prepare HTML rendering before generating HTML template screenshots",
+        help=(
+            "Prepare HTML rendering before generating. "
+            "Usually automatic for HTML templates."
+        ),
     ),
     verbose: bool = typer.Option(False, "--verbose", help="Enable verbose logging"),
 ):
@@ -727,6 +728,10 @@ def generate(
         with open(config_file) as f:
             config_data = yaml.safe_load(f)
 
+        if parallel_workers is not None:
+            config_data.setdefault("project", {})
+            config_data["project"]["parallel_workers"] = parallel_workers
+
         try:
             project_config = ProjectConfig(**config_data)
             stderr_console.print("Using flexible content-based API", style="blue")
@@ -849,11 +854,14 @@ def install_skills(
         None,
         "--agent",
         "-a",
-        help="Target a specific agent (e.g. claude-code, cursor). Installs to all detected agents by default.",
+        help=(
+            "Target a specific agent (e.g. claude-code, cursor). "
+            "Installs to all detected agents by default."
+        ),
     ),
     verbose: bool = typer.Option(False, "--verbose", help="Enable verbose logging"),
 ):
-    """Install the Koubou skill pack for AI coding agents (Claude Code, Cursor, Windsurf, and more)."""
+    """Install the Koubou skill pack for AI coding agents."""
 
     setup_logging(verbose)
 
@@ -1173,7 +1181,10 @@ def live(
     setup_html: bool = typer.Option(
         False,
         "--setup-html",
-        help="Prepare HTML rendering before starting live mode",
+        help=(
+            "Prepare HTML rendering before starting live mode. "
+            "Usually automatic for HTML templates."
+        ),
     ),
 ):
     """Live editing mode - regenerate screenshots when config or assets change"""

src/koubou/config.py

@@ -789,6 +789,14 @@ class ProjectInfo(BaseModel):
     name: str = Field(..., description="Project name")
     output_dir: str = Field(default="output", description="Output directory")
     device: str = Field(..., description="Target device frame")
+    parallel_workers: int = Field(
+        default=1,
+        ge=1,
+        description=(
+            "Number of screenshots to render concurrently. "
+            "Use 1 to keep sequential rendering."
+        ),
+    )
     output_size: Tuple[int, int] = Field(
         default=(1320, 2868),  # Default to iPhone6_9 dimensions
         description=(