Better handling of upgrades, an option to avoid overwriting main and devserver scripts, writing .new.py instead. Error out on unix socket in devserver.

.gitignore

@@ -3,4 +3,3 @@
 *.lock
 __pycache__/
 dist/
-/_version.py

fastapi_vue_setup.py

@@ -15,20 +15,18 @@ import os
 import re
 import subprocess
 import sys
-import tomllib
 from pathlib import Path
 from textwrap import indent
 
-import tomli_w
+import tomlkit
-
-try:
-    from _version import __version__
-except ImportError:
-    __version__ = "0.0.0+unknown"
 
 # Template directory
 TEMPLATE_DIR = Path(__file__).parent / "template"
 
+# Marker comment indicating file can be auto-upgraded
+# Users should remove this line to prevent automatic updates
+UPGRADE_MARKER = "auto-upgrade@fastapi-vue-setup"
+
 # pyproject.toml additions for patched projects
 PYPROJECT_ADDITIONS = {
     "tool": {
@@ -131,8 +129,7 @@ def find_module_name(project_dir: Path) -> str | None:
     if not pyproject.exists():
         return None
 
-    with open(pyproject, "rb") as f:
+    data = tomlkit.parse(pyproject.read_text())
-        data = tomllib.load(f)
 
     if "project" in data and "name" in data["project"]:
         name = data["project"]["name"]
@@ -205,19 +202,15 @@ def patch_app_file(
         print(f"❌ Cannot patch {path} - file not found")
         return False
 
-    content = path.read_text()
+    original_content = path.read_text()
     marker = "from fastapi_vue import Frontend"
 
-    if marker in content:
+    if marker in original_content:
-        print(f"⚠️  Skipping {path} (already patched)")
+        print(f"✔️  {path} (already patched)")
         return False
 
-    if dry_run:
-        print(f"[DRY RUN] Would patch {path}")
-        return True
-
     # Find where to insert the import (after other imports)
-    lines = content.split("\n")
+    lines = original_content.split("\n")
     import_line = "from fastapi_vue import Frontend"
 
     route_line = f'frontend.route({app_var}, "/")'
@@ -235,6 +228,11 @@ def patch_app_file(
             # Stop at first non-import, non-comment, non-empty line after imports
             break
 
+    # Check if we found imports to insert after
+    if last_import_idx == 0 and not lines[0].strip().startswith(("import ", "from ")):
+        print(f"⚠️  Skipping {path} (no imports found to patch)")
+        return False
+
     # Insert imports after last import, then frontend instantiation
     if not has_pathlib:
         lines.insert(last_import_idx + 1, "from pathlib import Path")
@@ -273,6 +271,15 @@ def patch_app_file(
         content = content[:insert_pos] + load_code + content[insert_pos:]
         lifespan_patched = True
 
+    # Check if content actually changed
+    if content == original_content:
+        print(f"⚠️  Skipping {path} (no changes needed)")
+        return False
+
+    if dry_run:
+        print(f"[DRY RUN] Would patch {path}")
+        return True
+
     path.write_text(content)
     print(f"✅ Patched {path}")
 
@@ -308,21 +315,17 @@ def patch_vite_config(
         print(f"❌ Cannot patch {path} - file not found")
         return False
 
-    content = path.read_text()
+    original_content = path.read_text()
     marker = "vite-plugin-fastapi"
 
-    if marker in content:
+    if marker in original_content:
-        print(f"⚠️  Skipping {path} (already patched)")
+        print(f"✔️  {path} (already patched)")
         return False
 
-    if dry_run:
-        print(f"[DRY RUN] Would patch {path}")
-        return True
-
     # Add import for the plugin at the top (after other imports)
     import_line = f"import fastapiVue from './{marker}.js'"
 
-    lines = content.split("\n")
+    lines = original_content.split("\n")
     new_lines = []
     import_inserted = False
 
@@ -354,6 +357,18 @@ def patch_vite_config(
     if match:
         insert_pos = match.end()
         content = content[:insert_pos] + "\n    fastapiVue()," + content[insert_pos:]
+    else:
+        print(f"⚠️  Skipping {path} (no plugins array found)")
+        return False
+
+    # Check if content actually changed
+    if content == original_content:
+        print(f"⚠️  Skipping {path} (no changes needed)")
+        return False
+
+    if dry_run:
+        print(f"[DRY RUN] Would patch {path}")
+        return True
 
     path.write_text(content)
     print(f"✅ Patched {path}")
@@ -389,16 +404,14 @@ def patch_frontend_health_check(frontend_dir: Path, dry_run: bool = False) -> bo
         print("⚠️  No Vue file found to patch, skipping frontend health check")
         return False
 
-    content = target_file.read_text()
+    original_content = target_file.read_text()
 
     # Check if already patched
-    if "/api/health" in content:
+    if "/api/health" in original_content:
-        print(f"⚠️  Skipping {target_file} (already patched)")
+        print(f"✔️  {target_file} (already patched)")
         return False
 
-    if dry_run:
+    content = original_content
-        print(f"[DRY RUN] Would patch {target_file}")
-        return True
 
     # Detect if TypeScript (has lang="ts" in script tag)
     is_typescript = 'lang="ts"' in content
@@ -410,47 +423,95 @@ def patch_frontend_health_check(frontend_dir: Path, dry_run: bool = False) -> bo
 
     # Insert script addition before </script>
     script_end_match = re.search(r"</script>", content)
-    if script_end_match:
+    if not script_end_match:
+        print(f"⚠️  Skipping {target_file} (no </script> tag found)")
+        return False
+
     insert_pos = script_end_match.start()
     content = content[:insert_pos] + script_addition + content[insert_pos:]
 
     # Insert status inline - find the best place based on file type
     # For HelloWorld.vue: insert before </h3>
-    # For App.vue (minimal): insert before the last </p> in template
+    # For App.vue (minimal): only patch if it's the default "You did it!" template
     if "HelloWorld" in str(target_file):
         # Insert before closing </h3>
         h3_close = content.find("    </h3>")
         if h3_close == -1:
+            print(
+                f"⚠️  Skipping {target_file} (no </h3> tag found for status insertion)"
+            )
             return False
         before, after = content[:h3_close], content[h3_close:]
         content = f"{before}{indent(STATUS_SPAN_TEMPLATE, '  ')}{after}"
     else:
-        # Minimal App.vue - insert before the last </p> before </template>
+        # Minimal App.vue - only patch if it contains the default welcome message
+        if "<h1>You did it!</h1>" not in content:
+            print(f"⚠️  Skipping {target_file} (not a default Vue template)")
+            return False
+        # Insert before the </p> tag
         template_end = content.find("</template>")
-        if template_end != -1:
+        if template_end == -1:
-            # Find last </p> before </template>
+            print(f"⚠️  Skipping {target_file} (no </template> tag found)")
-            last_p = content.rfind("  </p>", 0, template_end)
+            return False
+        # Find </p> before </template>
+        last_p = content.rfind("</p>", 0, template_end)
         if last_p == -1:
+            print(f"⚠️  Skipping {target_file} (no </p> tag found for status insertion)")
             return False
         before, after = content[:last_p], content[last_p:]
         content = f"{before}{STATUS_SPAN_TEMPLATE}{after}"
 
+    # Check if content actually changed
+    if content == original_content:
+        print(f"⚠️  Skipping {target_file} (no changes needed)")
+        return False
+
+    if dry_run:
+        print(f"[DRY RUN] Would patch {target_file}")
+        return True
+
     target_file.write_text(content)
     print(f"✅ Patched {target_file}")
     return True
 
 
+# Track .new.py files written during setup (for merge notification)
+_new_files_written: list[tuple[Path, Path]] = []
+
+
 def write_file(
     path: Path,
     content: str,
     overwrite: bool = True,
     dry_run: bool = False,
     executable: bool = False,
+    fallback_path: Path | None = None,
 ) -> bool:
-    """Write content to a file, handling existing files and dry-run."""
+    """Write content to a file, handling existing files and dry-run.
+
+    If fallback_path is provided and the file exists without the upgrade marker,
+    the content will be written to fallback_path instead of being skipped.
+    """
     exists = path.exists()
     if exists and not overwrite:
-        print(f"⚠️  Skipping {path} (exists)")
+        print(f"ℹ️  Skipping {path} (exists)")
+        return False
+
+    # Check if content is the same
+    if exists:
+        existing_content = path.read_text()
+        if existing_content == content:
+            print(f"✔️  {path} (already up to date)")
+            return False
+
+        # If overwrite requested but file doesn't have upgrade marker
+        if overwrite and UPGRADE_MARKER not in existing_content:
+            if fallback_path is not None:
+                # Write to fallback path instead
+                return _write_fallback_file(
+                    path, fallback_path, content, dry_run, executable
+                )
+            print(f"ℹ️  Skipping {path} (customized by user)")
             return False
 
     if dry_run:
@@ -467,47 +528,100 @@ def write_file(
     return True
 
 
-def merge_pyproject(data: dict, additions: dict, module_name: str) -> dict:
+def _write_fallback_file(
-    """Merge additions into pyproject.toml data."""
+    original_path: Path,
-    result = data.copy()
+    fallback_path: Path,
+    content: str,
+    dry_run: bool,
+    executable: bool,
+) -> bool:
+    """Write content to a fallback .new.py file when original can't be overwritten."""
+    # Check if fallback already has same content
+    if fallback_path.exists():
+        if fallback_path.read_text() == content:
+            print(f"✔️  {fallback_path} (already up to date)")
+            return False
 
+    if dry_run:
+        print(f"[DRY RUN] Would create {fallback_path} (original customized by user)")
+        _new_files_written.append((fallback_path, original_path))
+        return True
+
+    fallback_path.parent.mkdir(parents=True, exist_ok=True)
+    fallback_path.write_text(content)
+    if executable and sys.platform != "win32":
+        fallback_path.chmod(fallback_path.stat().st_mode | 0o111)
+    print(f"✅ Created {fallback_path} (original customized by user)")
+    _new_files_written.append((fallback_path, original_path))
+    return True
+
+
+def merge_pyproject(
+    data: tomlkit.TOMLDocument, additions: dict, module_name: str
+) -> tomlkit.TOMLDocument:
+    """Merge additions into pyproject.toml data, preserving comments and existing values."""
     # Ensure hatchling build system is configured
-    if "build-system" not in result:
+    if "build-system" not in data:
-        result["build-system"] = {}
+        data["build-system"] = tomlkit.table()
-    result["build-system"]["requires"] = ["hatchling"]
-    result["build-system"]["build-backend"] = "hatchling.build"
 
-    # Add dependencies
+    # Add hatchling to requires if not present, preserving existing requires
-    if "project" not in result:
+    if "requires" not in data["build-system"]:
-        result["project"] = {}
+        data["build-system"]["requires"] = ["hatchling"]
-    if "dependencies" not in result["project"]:
+    else:
-        result["project"]["dependencies"] = []
+        requires = list(data["build-system"]["requires"])
+        if not any(r.startswith("hatchling") for r in requires):
+            requires.insert(0, "hatchling")
+            data["build-system"]["requires"] = requires
+
+    if "build-backend" not in data["build-system"]:
+        data["build-system"]["build-backend"] = "hatchling.build"
+
+    # Ensure project table exists
+    if "project" not in data:
+        data["project"] = tomlkit.table()
 
     # Add hatch build config
-    if "tool" not in result:
+    if "tool" not in data:
-        result["tool"] = {}
+        data["tool"] = tomlkit.table()
-    if "hatch" not in result["tool"]:
+    if "hatch" not in data["tool"]:
-        result["tool"]["hatch"] = {}
+        data["tool"]["hatch"] = tomlkit.table()
-    if "build" not in result["tool"]["hatch"]:
+    if "build" not in data["tool"]["hatch"]:
-        result["tool"]["hatch"]["build"] = {}
+        data["tool"]["hatch"]["build"] = tomlkit.table()
 
-    hatch_build = additions["tool"]["hatch"]["build"]
+    hatch_build = data["tool"]["hatch"]["build"]
-    result["tool"]["hatch"]["build"]["packages"] = [
+    hatch_additions = additions["tool"]["hatch"]["build"]
-        p.replace("MODULE_NAME", module_name) for p in hatch_build["packages"]
-    ]
-    result["tool"]["hatch"]["build"]["artifacts"] = [
-        a.replace("MODULE_NAME", module_name) for a in hatch_build["artifacts"]
-    ]
-    result["tool"]["hatch"]["build"]["only-packages"] = hatch_build["only-packages"]
 
-    if "targets" not in result["tool"]["hatch"]["build"]:
+    # Set packages if not already set
-        result["tool"]["hatch"]["build"]["targets"] = {}
+    if "packages" not in hatch_build:
-
+        hatch_build["packages"] = [
-    result["tool"]["hatch"]["build"]["targets"]["sdist"] = hatch_build["targets"][
+            p.replace("MODULE_NAME", module_name) for p in hatch_additions["packages"]
-        "sdist"
         ]
 
-    return result
+    # Set artifacts if not already set
+    if "artifacts" not in hatch_build:
+        hatch_build["artifacts"] = [
+            a.replace("MODULE_NAME", module_name) for a in hatch_additions["artifacts"]
+        ]
+
+    # Set only-packages if not already set
+    if "only-packages" not in hatch_build:
+        hatch_build["only-packages"] = hatch_additions["only-packages"]
+
+    # Add sdist target with custom hook
+    if "targets" not in hatch_build:
+        hatch_build["targets"] = tomlkit.table()
+    if "sdist" not in hatch_build["targets"]:
+        hatch_build["targets"]["sdist"] = tomlkit.table()
+    if "hooks" not in hatch_build["targets"]["sdist"]:
+        hatch_build["targets"]["sdist"]["hooks"] = tomlkit.table()
+    if "custom" not in hatch_build["targets"]["sdist"]["hooks"]:
+        hatch_build["targets"]["sdist"]["hooks"]["custom"] = tomlkit.table()
+    if "path" not in hatch_build["targets"]["sdist"]["hooks"]["custom"]:
+        hatch_build["targets"]["sdist"]["hooks"]["custom"]["path"] = hatch_additions[
+            "targets"
+        ]["sdist"]["hooks"]["custom"]["path"]
+
+    return data
 
 
 # =============================================================================
@@ -705,25 +819,38 @@ def cmd_setup(args: argparse.Namespace) -> int:
             module_dir.mkdir(parents=True)
 
     # === Install scripts (always update our own scripts) ===
-    script_files = [
+    # util.py and build-frontend.py are internal and always overwritten
+    # devserver.py can be customized, so use fallback if needed
+    internal_script_files = [
         (fastapi_vue_scripts / "util.py", "scripts/fastapi-vue/util.py"),
         (
             fastapi_vue_scripts / "build-frontend.py",
             "scripts/fastapi-vue/build-frontend.py",
         ),
-        (scripts_dir / "devserver.py", "scripts/devserver.py"),
     ]
 
-    for dest_path, template_path in script_files:
+    for dest_path, template_path in internal_script_files:
         template = load_template(template_path)
         content = render_template(template, **tpl_vars)
-        is_executable = dest_path.name == "devserver.py"
         write_file(
             dest_path,
             content,
             overwrite=True,
             dry_run=dry_run,
-            executable=is_executable,
+        )
+
+    # devserver.py - use fallback if customized by user
+    devserver_path = scripts_dir / "devserver.py"
+    devserver_fallback = scripts_dir / "devserver.new.py"
+    template = load_template("scripts/devserver.py")
+    content = render_template(template, **tpl_vars)
+    write_file(
+        devserver_path,
+        content,
+        overwrite=True,
+        dry_run=dry_run,
+        executable=True,
+        fallback_path=devserver_fallback,
     )
 
     # === Handle app module ===
@@ -747,10 +874,21 @@ def cmd_setup(args: argparse.Namespace) -> int:
 
     # === Handle __main__.py ===
     main_file = module_dir / "__main__.py"
-    if not main_file.exists():
+    main_fallback = module_dir / "__main__.new.py"
     template = load_template("backend/__main__.py")
-        content = render_template(template, **tpl_vars)
+    main_content = render_template(template, **tpl_vars)
-        write_file(main_file, content, overwrite=False, dry_run=dry_run)
+
+    # Use write_file with fallback - it handles all cases:
+    # - File doesn't exist: create it
+    # - File exists with marker: update it
+    # - File exists without marker: write to fallback
+    write_file(
+        main_file,
+        main_content,
+        overwrite=True,
+        dry_run=dry_run,
+        fallback_path=main_fallback,
+    )
 
     # === Update vite.config.js/ts ===
     frontend_dir = project_dir / "frontend"
@@ -779,39 +917,43 @@ def cmd_setup(args: argparse.Namespace) -> int:
     # === Update pyproject.toml ===
     pyproject_path = project_dir / "pyproject.toml"
     if pyproject_path.exists():
-        with open(pyproject_path, "rb") as f:
+        old_content = pyproject_path.read_text()
-            data = tomllib.load(f)
+        data = tomlkit.parse(old_content)
 
         updated = merge_pyproject(data, PYPROJECT_ADDITIONS, module_name)
 
-        # Add script entry pointing to the app we found/created
+        # Only add script entry if project doesn't already have scripts
-        if "scripts" not in updated["project"]:
+        if "scripts" not in updated["project"] or not updated["project"]["scripts"]:
-            updated["project"]["scripts"] = {}
+            updated["project"]["scripts"] = tomlkit.table()
             script_name = module_name.replace("_", "-")
             updated["project"]["scripts"][script_name] = f"{module_name}.__main__:main"
 
-        if dry_run:
+        # Check if content actually changed
+        new_content = tomlkit.dumps(updated)
+
+        if new_content == old_content:
+            print(f"✔️  {pyproject_path} (already up to date)")
+        elif dry_run:
             print(f"[DRY RUN] Would update {pyproject_path}")
         else:
-            with open(pyproject_path, "wb") as f:
+            pyproject_path.write_text(new_content)
-                tomli_w.dump(updated, f)
             print(f"✅ Updated {pyproject_path}")
 
     # === Add dependencies using uv ===
     if dry_run:
-        print("[DRY RUN] Would run: uv add 'fastapi[standard]' fastapi-vue")
+        print("[DRY RUN] Would run: uv add -U 'fastapi[standard]' fastapi-vue")
-        print("[DRY RUN] Would run: uv add --group dev httpx")
+        print("[DRY RUN] Would run: uv add -U --group dev httpx")
     else:
         print("📦 Adding dependencies...")
         result = subprocess.run(
-            ["uv", "add", "fastapi[standard]", "fastapi-vue"],
+            ["uv", "add", "-U", "fastapi[standard]", "fastapi-vue"],
             cwd=project_dir,
             check=False,
         )
         if result.returncode != 0:
             print("⚠️  Failed to add main dependencies")
         result = subprocess.run(
-            ["uv", "add", "--group", "dev", "httpx"],
+            ["uv", "add", "-U", "--group", "dev", "httpx"],
             cwd=project_dir,
             check=False,
         )
@@ -852,6 +994,19 @@ def cmd_setup(args: argparse.Namespace) -> int:
     )
     print(message)
 
+    # Show merge note if any .new.py files were written
+    if _new_files_written:
+        print()
+        print(
+            "⚠️  Note: Some files could not be auto-upgraded because you customized them."
+        )
+        print("   Please manually merge the following files:")
+        for new_file, original_file in _new_files_written:
+            print(f"     • {new_file.name} → {original_file.name}")
+        print()
+        # Clear the list for potential subsequent runs
+        _new_files_written.clear()
+
     return 0
 
 
@@ -901,11 +1056,6 @@ Examples:
     parser.add_argument(
         "--dry-run", action="store_true", help="Show what would be done"
     )
-    parser.add_argument(
-        "--version",
-        action="version",
-        version=f"%(prog)s {__version__}",
-    )
 
     args = parser.parse_args()
 

pyproject.toml

@@ -9,7 +9,7 @@ description = "Tool to create or patch FastAPI+Vue projects with integrated buil
 readme = "README.md"
 requires-python = ">=3.11"
 dependencies = [
-    "tomli-w>=1.0.0",
+    "tomlkit>=0.12.0",
 ]
 
 [project.urls]
@@ -22,9 +22,6 @@ fastapi-vue-setup = "fastapi_vue_setup:main"
 [tool.hatch.version]
 source = "vcs"
 
-[tool.hatch.build.hooks.vcs]
-version-file = "_version.py"
-
 [tool.hatch.build.targets.wheel]
 include = ["fastapi_vue_setup.py", "template/**/*", "_version.py"]
 

template/backend/__main__.py

@@ -1,3 +1,4 @@
+# auto-upgrade@fastapi-vue-setup - remove this if you modify this file
 import argparse
 import asyncio
 import os

template/scripts/devserver.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env -S uv run
+# auto-upgrade@fastapi-vue-setup - remove this if you modify this file
 """Run Vite development server for frontend and FastAPI backend with auto-reload.
 
 Usage:
@@ -16,17 +17,15 @@ Environment:
 import argparse
 import asyncio
 import contextlib
-import ipaddress
 import os
 from pathlib import Path
 from sys import stderr
-from urllib.parse import urlparse
 
 import httpx
+from fastapi_vue.hostutil import parse_endpoint
 
 exec((Path(__file__).parent / "fastapi-vue/util.py").read_text("UTF-8"))  # noqa: S102
 
-DEFAULT_HOST = "localhost"
 DEFAULT_VITE_PORT = 5173
 DEFAULT_BACKEND_PORT = 5180
 FRONTEND_PATH = Path(__file__).parent.parent / "frontend"
@@ -45,45 +44,8 @@ BUN_BUG = """\
 """
 
 
-def parse_endpoint(
-    value: str | None, default_port: int = DEFAULT_VITE_PORT
-) -> tuple[str | None, int, bool]:
-    """Parse an endpoint for Vite or backend.
-
-    Returns (host, port, all_ifaces).
-    """
-    if not value:
-        return DEFAULT_HOST, default_port, False
-
-    # Port only (numeric) -> localhost:port
-    if value.isdigit():
-        return DEFAULT_HOST, int(value), False
-
-    # Leading colon :port -> bind all interfaces
-    if value.startswith(":") and value != ":":
-        port_part = value[1:]
-        if not port_part.isdigit():
-            raise SystemExit(f"Invalid port in '{value}'")
-        return None, int(port_part), True
-
-    # Unbracketed IPv6 (cannot safely contain a port)
-    if value.count(":") > 1 and not value.startswith("["):
-        try:
-            ipaddress.IPv6Address(value)
-        except ValueError as e:
-            raise SystemExit(f"Invalid IPv6 address '{value}': {e}") from e
-        return value, default_port, False
-
-    # Use urllib.parse for everything else
-    parsed = urlparse(f"//{value}")
-    host = parsed.hostname or DEFAULT_HOST
-    port = parsed.port or default_port
-
-    return host, port, False
-
-
 def resolve_frontend_tools(
-    vite_host: str | None, vite_port: int, all_ifaces: bool
+    vite_port: int, all_ifaces: bool
 ) -> tuple[list[str], list[str], str]:
     """Resolve frontend install and dev commands.
 
@@ -123,8 +85,6 @@ def resolve_frontend_tools(
 
     if all_ifaces:
         dev_cmd.append("--host")
-    elif vite_host and vite_host != "localhost":
-        dev_cmd.append(f"--host={vite_host}")
 
     if name == "bun":
         stderr.write(BUN_BUG)
@@ -132,13 +92,15 @@ def resolve_frontend_tools(
     return install_cmd, dev_cmd, name
 
 
-async def wait_for_backend(backend_host: str, backend_port: int):
+async def wait_for_backend(host: str, port: int):
     """Wait for the backend to be ready by polling the health endpoint."""
     max_attempts = 50
+    url = f"http://{host}:{port}"
+
     async with httpx.AsyncClient() as client:
         for attempt in range(max_attempts):
             try:
-                await client.get(f"http://{backend_host}:{backend_port}", timeout=1.0)
+                await client.get(url, timeout=1.0)
                 stderr.write("✓ Backend ready!\n")
                 return True
             except httpx.RequestError:
@@ -168,23 +130,29 @@ async def _terminate_process(proc: asyncio.subprocess.Process, name: str) -> Non
 
 
 async def run_devserver(
-    vite_host: str | None,
     vite_port: int,
     all_ifaces: bool,
     backend_host: str,
     backend_port: int,
 ) -> None:
     """Run the development server with install, backend, and frontend."""
-    install_cmd, dev_cmd, tool_name = resolve_frontend_tools(
+    install_cmd, dev_cmd, tool_name = resolve_frontend_tools(vite_port, all_ifaces)
-        vite_host, vite_port, all_ifaces
-    )
 
     # Tell the backend where the Vite dev server is
-    os.environ["FASTAPI_VUE_FRONTEND_URL"] = (
+    os.environ["FASTAPI_VUE_FRONTEND_URL"] = f"http://localhost:{vite_port}"
-        f"http://{vite_host or 'localhost'}:{vite_port}"
-    )
     # Tell Vite where the backend is (for proxying /api requests)
     os.environ["FASTAPI_VUE_BACKEND_URL"] = f"http://{backend_host}:{backend_port}"
+
+    backend_cmd = [
+        "uvicorn",
+        "MODULE_NAME.app:app",
+        "--host",
+        backend_host,
+        "--port",
+        str(backend_port),
+        "--reload",
+    ]
+
     cwd = str(Path(__file__).parent.parent)
     frontend_cwd = str(FRONTEND_PATH)
 
@@ -202,15 +170,6 @@ async def run_devserver(
         await asyncio.sleep(0.1)
 
         # Start backend (concurrent with install)
-        backend_cmd = [
-            "uvicorn",
-            "MODULE_NAME.app:app",
-            "--host",
-            backend_host,
-            "--port",
-            str(backend_port),
-            "--reload",
-        ]
         stderr.write(f">>> {' '.join(backend_cmd)}\n")
         backend_proc = await asyncio.create_subprocess_exec(*backend_cmd, cwd=cwd)
 
@@ -292,15 +251,26 @@ def main():
     )
     args = parser.parse_args()
 
-    vite_host, vite_port, all_ifaces = parse_endpoint(args.frontend, DEFAULT_VITE_PORT)
+    # parse_endpoint returns list of dicts with host/port or uds keys
-    backend_host, backend_port, _ = parse_endpoint(args.backend, DEFAULT_BACKEND_PORT)
+    # Multiple entries means bind all interfaces (IPv4 + IPv6)
-    # Backend host defaults to localhost (never None)
+    vite_endpoints = parse_endpoint(args.frontend, DEFAULT_VITE_PORT)
-    backend_host = backend_host or DEFAULT_HOST
+    backend_endpoints = parse_endpoint(args.backend, DEFAULT_BACKEND_PORT)
+
+    # Vite doesn't support unix sockets
+    if "uds" in vite_endpoints[0]:
+        stderr.write("┃ ⚠️  Unix sockets not supported for frontend\n")
+        raise SystemExit(1)
+    if "uds" in backend_endpoints[0]:
+        stderr.write("┃ ⚠️  Unix sockets not supported for backend\n")
+        raise SystemExit(1)
+
+    vite_port = vite_endpoints[0]["port"]
+    all_ifaces = len(vite_endpoints) > 1
+    backend_host = backend_endpoints[0]["host"]
+    backend_port = backend_endpoints[0]["port"]
 
     with contextlib.suppress(KeyboardInterrupt):
-        asyncio.run(
+        asyncio.run(run_devserver(vite_port, all_ifaces, backend_host, backend_port))
-            run_devserver(vite_host, vite_port, all_ifaces, backend_host, backend_port)
-        )
 
 
 if __name__ == "__main__":