diff --git a/.opencode/templates/backend/cookiecutter.json b/.opencode/templates/backend/cookiecutter.json
index 313f5c2..8e16a53 100644
--- a/.opencode/templates/backend/cookiecutter.json
+++ b/.opencode/templates/backend/cookiecutter.json
@@ -1,5 +1,5 @@
 {
-  "project_name": "my-project",
+  "project_name": "my_project",
   "project_type": "backend",
   "description": "Project description",
   "use_auth": ["no", "yes"],
diff --git a/.opencode/templates/backend/hooks/pre_gen_project.py b/.opencode/templates/backend/hooks/pre_gen_project.py
new file mode 100644
index 0000000..05edf89
--- /dev/null
+++ b/.opencode/templates/backend/hooks/pre_gen_project.py
@@ -0,0 +1,35 @@
+"""Pre-generation hook for the backend cookiecutter template.
+
+Validates that ``project_name`` is a valid Python identifier so the
+generated package dir + imports (``from <project_name>.X import Y``) do
+not raise ``SyntaxError``. Hyphens, dots, spaces and leading digits are
+rejected with a hint to use an underscore-separated name instead.
+
+See issue #262: default ``my-project`` used to render as
+``from my-project.config.settings import settings`` which is a
+``SyntaxError`` (``-`` is not allowed in a Python identifier).
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+
+_VALID_IDENTIFIER = re.compile(r"^[a-z][a-z0-9_]*$")
+
+
+def main() -> None:
+    project_name = "{{ cookiecutter.project_name }}"
+    if not _VALID_IDENTIFIER.fullmatch(project_name):
+        sys.exit(
+            f"Invalid project_name: {project_name!r}\n"
+            "project_name must be a valid Python identifier matching "
+            "^[a-z][a-z0-9_]*$ (lowercase, no hyphens/dots/spaces, "
+            "no leading digit).\n"
+            f"Use 'my_project' instead of 'my-project' (or 'my.project', "
+            "'my project')."
+        )
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/.opencode/templates/cli/cookiecutter.json b/.opencode/templates/cli/cookiecutter.json
index ac8dbe2..02b0160 100644
--- a/.opencode/templates/cli/cookiecutter.json
+++ b/.opencode/templates/cli/cookiecutter.json
@@ -1,5 +1,5 @@
 {
-  "project_name": "my-cli",
+  "project_name": "my_cli",
   "project_type": "cli",
   "description": "CLI tool description",
   "use_auth": ["no", "yes"],
diff --git a/.opencode/templates/cli/hooks/pre_gen_project.py b/.opencode/templates/cli/hooks/pre_gen_project.py
new file mode 100644
index 0000000..3bcdfa9
--- /dev/null
+++ b/.opencode/templates/cli/hooks/pre_gen_project.py
@@ -0,0 +1,34 @@
+"""Pre-generation hook for the cli cookiecutter template.
+
+Validates that ``project_name`` is a valid Python identifier so the
+generated package dir + imports (``from <project_name>.X import Y``) do
+not raise ``SyntaxError``. Hyphens, dots, spaces and leading digits are
+rejected with a hint to use an underscore-separated name instead.
+
+See issue #262: default ``my-cli`` used to render as
+``from my-cli.core import app`` which is a ``SyntaxError`` (``-`` is not
+allowed in a Python identifier).
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+
+_VALID_IDENTIFIER = re.compile(r"^[a-z][a-z0-9_]*$")
+
+
+def main() -> None:
+    project_name = "{{ cookiecutter.project_name }}"
+    if not _VALID_IDENTIFIER.fullmatch(project_name):
+        sys.exit(
+            f"Invalid project_name: {project_name!r}\n"
+            "project_name must be a valid Python identifier matching "
+            "^[a-z][a-z0-9_]*$ (lowercase, no hyphens/dots/spaces, "
+            "no leading digit).\n"
+            f"Use 'my_cli' instead of 'my-cli' (or 'my.cli', 'my cli')."
+        )
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/.opencode/templates/fullstack/cookiecutter.json b/.opencode/templates/fullstack/cookiecutter.json
index ad8f1e8..2702b94 100644
--- a/.opencode/templates/fullstack/cookiecutter.json
+++ b/.opencode/templates/fullstack/cookiecutter.json
@@ -1,5 +1,5 @@
 {
-  "project_name": "my-fullstack",
+  "project_name": "my_fullstack",
   "project_type": "fullstack",
   "description": "Fullstack project description",
   "use_auth": ["no", "yes"],
diff --git a/.opencode/templates/fullstack/hooks/pre_gen_project.py b/.opencode/templates/fullstack/hooks/pre_gen_project.py
new file mode 100644
index 0000000..7e4583b
--- /dev/null
+++ b/.opencode/templates/fullstack/hooks/pre_gen_project.py
@@ -0,0 +1,35 @@
+"""Pre-generation hook for the fullstack cookiecutter template.
+
+Validates that ``project_name`` is a valid Python identifier so the
+generated package dir + imports (``from <project_name>.X import Y``) do
+not raise ``SyntaxError``. Hyphens, dots, spaces and leading digits are
+rejected with a hint to use an underscore-separated name instead.
+
+See issue #262: default ``my-fullstack`` used to render as
+``from my-fullstack.config.settings import settings`` which is a
+``SyntaxError`` (``-`` is not allowed in a Python identifier).
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+
+_VALID_IDENTIFIER = re.compile(r"^[a-z][a-z0-9_]*$")
+
+
+def main() -> None:
+    project_name = "{{ cookiecutter.project_name }}"
+    if not _VALID_IDENTIFIER.fullmatch(project_name):
+        sys.exit(
+            f"Invalid project_name: {project_name!r}\n"
+            "project_name must be a valid Python identifier matching "
+            "^[a-z][a-z0-9_]*$ (lowercase, no hyphens/dots/spaces, "
+            "no leading digit).\n"
+            f"Use 'my_fullstack' instead of 'my-fullstack' (or 'my.fullstack', "
+            "'my fullstack')."
+        )
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/tests/test_cookiecutter_templates.py b/tests/test_cookiecutter_templates.py
index 6d98646..0ed94a1 100644
--- a/tests/test_cookiecutter_templates.py
+++ b/tests/test_cookiecutter_templates.py
@@ -14,12 +14,15 @@ Covers:
 
 from __future__ import annotations
 
+import ast
 import importlib.util
 import json
+import re
 import sys
 from pathlib import Path
 
 import pytest
+from cookiecutter.exceptions import FailedHookException
 from cookiecutter.main import cookiecutter
 
 REPO_ROOT = Path(__file__).resolve().parent.parent
@@ -53,15 +56,15 @@ def render(tmp_path, template_name, extra_context):
 @pytest.mark.parametrize(
     "template_name, extra_context",
     [
-        ("backend", {"project_name": "demo-be"}),
-        ("cli", {"project_name": "demo-cli"}),
-        ("fullstack", {"project_name": "demo-fs"}),
+        ("backend", {"project_name": "demo_be"}),
+        ("cli", {"project_name": "demo_cli"}),
+        ("fullstack", {"project_name": "demo_fs"}),
     ],
 )
 def test_template_dir_exists(render):
     """Each template renders to a project dir of the given name."""
     assert render.is_dir()
-    assert render.name in {"demo-be", "demo-cli", "demo-fs"}
+    assert render.name in {"demo_be", "demo_cli", "demo_fs"}
 
 
 @pytest.mark.parametrize("template_name", ["backend", "cli", "fullstack"])
@@ -824,3 +827,142 @@ def test_main_imports_setup_logging_unconditionally(render):
     # ``setup_logging()`` call without a preceding import in the same file.
     import_lines = [ln for ln in main.splitlines() if "import" in ln and "setup_logging" in ln]
     assert import_lines, "setup_logging not imported in main.py"
+
+
+# ── issue #262: project_name must be a valid Python identifier ──────────────
+
+# Regex mirrored in every ``pre_gen_project.py`` hook (kept here as a single
+# source of truth for the test, validated against the actual hook files).
+_VALID_PROJECT_NAME = re.compile(r"^[a-z][a-z0-9_]*$")
+
+
+@pytest.mark.parametrize(
+    "template_name, bad_name",
+    [
+        ("backend", "my-project"),  # hyphen
+        ("backend", "my.project"),  # dot
+        ("backend", "my project"),  # space
+        ("backend", "My_Project"),  # uppercase
+        ("backend", "123abc"),  # leading digit
+        ("fullstack", "my-fullstack"),
+        ("fullstack", "My_Fullstack"),
+        ("cli", "my-cli"),
+        ("cli", "123cli"),
+    ],
+)
+def test_pre_gen_hook_rejects_invalid_project_name(tmp_path, template_name, bad_name):
+    """pre_gen_project.py exits non-zero for invalid project_name.
+
+    Regression guard for issue #262: hyphens/dots/spaces/uppercase/leading
+    digits in ``project_name`` would render as ``from my-project.X import Y``
+    which is a ``SyntaxError`` in the generated project. The hook must abort
+    cookiecutter with ``FailedHookException`` BEFORE any file is rendered.
+    """
+    with pytest.raises(FailedHookException):
+        cookiecutter(
+            template=str(TEMPLATES_DIR / template_name),
+            no_input=True,
+            output_dir=str(tmp_path),
+            extra_context={"project_name": bad_name},
+        )
+    # nothing rendered
+    assert not (tmp_path / bad_name).exists()
+
+
+@pytest.mark.parametrize(
+    "template_name, good_name",
+    [
+        ("backend", "my_project"),
+        ("fullstack", "my_fullstack"),
+        ("cli", "my_cli"),
+        ("backend", "be"),
+        ("cli", "cl"),
+        ("fullstack", "fs"),
+    ],
+)
+def test_pre_gen_hook_accepts_valid_project_name(tmp_path, template_name, good_name):
+    """Valid identifiers pass the hook and render a project."""
+    out = cookiecutter(
+        template=str(TEMPLATES_DIR / template_name),
+        no_input=True,
+        output_dir=str(tmp_path),
+        extra_context={"project_name": good_name},
+    )
+    assert Path(out).is_dir()
+
+
+@pytest.mark.parametrize("template_name", ["backend", "cli", "fullstack"])
+def test_cookiecutter_json_default_is_valid_identifier(template_name):
+    """The default ``project_name`` in cookiecutter.json passes the hook regex.
+
+    Issue #262: defaults must NOT contain hyphens (``my-project``) — they
+    are used as-is in paths/imports and would break the no-input flow.
+    """
+    cfg = json.loads((TEMPLATES_DIR / template_name / "cookiecutter.json").read_text())
+    default = cfg["project_name"]
+    assert _VALID_PROJECT_NAME.fullmatch(default), (
+        f"default project_name {default!r} in {template_name}/cookiecutter.json "
+        f"is not a valid Python identifier (^[a-z][a-z0-9_]*$)"
+    )
+
+
+@pytest.mark.parametrize(
+    "template_name, extra_context",
+    [
+        ("backend", {"project_name": "demo_be", "use_db": "yes", "use_auth": "yes"}),
+        ("cli", {"project_name": "demo_cli"}),
+        ("fullstack", {"project_name": "demo_fs", "use_db": "yes", "use_auth": "yes"}),
+    ],
+)
+def test_generated_imports_are_parseable(render, template_name, extra_context):
+    """Every generated ``.py`` parses with ``ast.parse`` (no SyntaxError).
+
+    Issue #262: hyphens in ``project_name`` produced ``from my-project.X
+    import Y`` which is a ``SyntaxError``. With the pre_gen hook the name
+    is already a valid identifier, so all generated imports must parse.
+    """
+    pkg = extra_context["project_name"]
+    offenders: list[str] = []
+    for py in render.rglob("*.py"):
+        text = py.read_text()
+        try:
+            ast.parse(text)
+        except SyntaxError as exc:
+            offenders.append(f"{py.relative_to(render)}: {exc}")
+    assert not offenders, f"SyntaxError in generated files (pkg={pkg}):\n" + "\n".join(offenders)
+
+
+@pytest.mark.parametrize(
+    "template_name, extra_context",
+    [
+        ("backend", {"project_name": "demo_be"}),
+        ("cli", {"project_name": "demo_cli"}),
+        ("fullstack", {"project_name": "demo_fs"}),
+    ],
+)
+def test_resolve_package_name_matches_directory(render, template_name, extra_context):
+    """``_resolve_package_name`` from project-status matches the package dir.
+
+    Issue #262: with a valid identifier ``project_name``, the directory name
+    equals the package name, and ``_resolve_package_name`` (which normalizes
+    ``[project].name`` via PEP 503) returns the same value. This is the
+    contract that ``project-status`` relies on to detect BACKEND/FULLSTACK/
+    CLI without false FAIL/WARN.
+    """
+    pkg = extra_context["project_name"]
+    ctx = ps.RepoCtx(root=render, config=ps.load_config(render))
+    # fullstack: pyproject.toml lives under ``backend/`` (see _api_dirs_for
+    # in project-status.py), so resolve against a backend-rooted context.
+    if template_name == "fullstack":
+        ctx = ps.RepoCtx(root=render / "backend", config=ps.load_config(render / "backend"))
+    resolved = ps._resolve_package_name(ctx)
+    assert resolved is not None, "_resolve_package_name returned None"
+    assert resolved == pkg, (
+        f"_resolve_package_name()={resolved!r} != directory name {pkg!r}; "
+        f"project-status would look for src/{resolved}/ but the real dir is src/{pkg}/"
+    )
+    # fullstack: the package dir lives under backend/src/
+    if template_name == "fullstack":
+        assert (render / "backend" / "src" / pkg).is_dir()
+    else:
+        assert (render / "src" / pkg).is_dir()