diff --git a/routes/shell_routes.py b/routes/shell_routes.py
index ffa230c..cd9a5d9 100644
--- a/routes/shell_routes.py
+++ b/routes/shell_routes.py
@@ -127,6 +127,24 @@ def _docker_row_status(*, on_remote, in_container, installed, default_hint):
     return DockerRowStatus(applicable=True, install_hint=default_hint)
 
 
+def _pip_dist_name(pkg: dict) -> str:
+    """Distribution name for importlib.metadata lookups.
+
+    The Cookbook package catalog carries both the import name (``name``, e.g.
+    ``llama_cpp``) and the pip spec (``pip``, e.g. ``llama-cpp-python[server]``).
+    The distribution is NOT always the import name with underscores swapped for
+    dashes — ``llama_cpp`` ships in the ``llama-cpp-python`` distribution — so
+    derive it from the pip spec (stripping any ``[extras]`` and version markers)
+    and fall back to the munged import name only when no pip spec is declared.
+    """
+    pip = (pkg.get("pip") or "").strip()
+    if pip:
+        base = re.split(r"[\[<>=!~;\s]", pip, maxsplit=1)[0].strip()
+        if base:
+            return base
+    return (pkg.get("name") or "").replace("_", "-")
+
+
 def _package_installed_from_probe(name: str, probe: dict) -> bool:
     """Return whether an optional dependency is usable by Cookbook.
 
@@ -945,7 +963,7 @@ def setup_shell_routes() -> APIRouter:
                     if pkg["name"] == "vllm":
                         pkg["installed"] = shutil.which("vllm") is not None
                     else:
-                        importlib_metadata.version(pkg["name"].replace("_", "-"))
+                        importlib_metadata.version(_pip_dist_name(pkg))
                         pkg["installed"] = True
                 except ImportError:
                     pkg["installed"] = False
diff --git a/tests/test_cookbook_package_detection.py b/tests/test_cookbook_package_detection.py
new file mode 100644
index 0000000..32aa7c9
--- /dev/null
+++ b/tests/test_cookbook_package_detection.py
@@ -0,0 +1,50 @@
+"""Local Cookbook dependency detection — distribution-name mapping (issue #1020).
+
+The Cookbook → Dependencies tab reported `llama-cpp-python[server]` as "not
+installed" even when it was installed. The local check looked up distribution
+metadata under `pkg["name"].replace("_", "-")` → "llama-cpp", but the import
+module `llama_cpp` ships in the **llama-cpp-python** distribution, so
+`importlib.metadata.version("llama-cpp")` raised PackageNotFoundError and the
+package was marked missing. The fix derives the distribution name from the
+package's declared pip spec instead.
+"""
+
+from pathlib import Path
+
+from routes.shell_routes import _pip_dist_name
+
+
+def test_llama_cpp_maps_to_llama_cpp_python_distribution():
+    pkg = {"name": "llama_cpp", "pip": "llama-cpp-python[server]"}
+    assert _pip_dist_name(pkg) == "llama-cpp-python"
+    # The old behaviour (munging the import name) produced the wrong dist name.
+    assert _pip_dist_name(pkg) != "llama-cpp"
+
+
+def test_extras_and_version_markers_are_stripped():
+    assert _pip_dist_name({"name": "diffusers", "pip": "diffusers[torch]"}) == "diffusers"
+    assert _pip_dist_name({"name": "sglang", "pip": "sglang[all]"}) == "sglang"
+    assert _pip_dist_name({"name": "rembg", "pip": "rembg[gpu]"}) == "rembg"
+    assert _pip_dist_name({"name": "x", "pip": "foo>=1.2,<2"}) == "foo"
+    assert _pip_dist_name({"name": "y", "pip": "bar==1.0 ; python_version>='3.9'"}) == "bar"
+
+
+def test_plain_names_pass_through():
+    assert _pip_dist_name({"name": "vllm", "pip": "vllm"}) == "vllm"
+    assert _pip_dist_name({"name": "playwright", "pip": "playwright"}) == "playwright"
+    assert _pip_dist_name({"name": "hf_transfer", "pip": "hf_transfer"}) == "hf_transfer"
+
+
+def test_falls_back_to_import_name_when_no_pip_spec():
+    # System rows (tmux/docker) declare no pip spec; fall back to the munged name.
+    assert _pip_dist_name({"name": "some_mod", "pip": ""}) == "some-mod"
+    assert _pip_dist_name({"name": "tmux"}) == "tmux"
+
+
+def test_route_uses_dist_name_helper_not_munged_import_name():
+    """Lock the wiring: the local package check must look up metadata by the
+    derived distribution name, not the old `name.replace('_','-')` (the exact
+    bug that hid llama-cpp-python)."""
+    src = (Path(__file__).resolve().parents[1] / "routes" / "shell_routes.py").read_text(encoding="utf-8")
+    assert "importlib_metadata.version(_pip_dist_name(pkg))" in src
+    assert 'importlib_metadata.version(pkg["name"].replace("_", "-"))' not in src