diff --git a/amlb/benchmarks/file.py b/amlb/benchmarks/file.py
index 034af74cc..3ff80e874 100644
--- a/amlb/benchmarks/file.py
+++ b/amlb/benchmarks/file.py
@@ -33,7 +33,7 @@ def load_file_benchmark(
     """Loads benchmark from a local file."""
     benchmark_file = _find_local_benchmark_definition(name, benchmark_definition_dirs)
     log.info("Loading benchmark definitions from %s.", benchmark_file)
-    tasks = config_load(benchmark_file)
+    tasks = config_load(benchmark_file, strict=True)
     benchmark_name, _ = os.path.splitext(os.path.basename(benchmark_file))
     for task in tasks:
         if task["openml_task_id"] is not None and not isinstance(
diff --git a/amlb/frameworks/definitions.py b/amlb/frameworks/definitions.py
index 2c2c68bc7..f30d4ae2a 100644
--- a/amlb/frameworks/definitions.py
+++ b/amlb/frameworks/definitions.py
@@ -44,7 +44,13 @@ def _load_and_merge_framework_definitions(
     definitions_by_tag = Namespace()
     for tag in [default_tag] + config.frameworks.tags:
         definitions_by_file = [
-            config_load(_definition_file(file, tag)) for file in frameworks_file
+            config_load(
+                _definition_file(file, tag),
+                strict=(
+                    tag == default_tag
+                ),  # Only strict for base files, not tagged variants
+            )
+            for file in frameworks_file
         ]
         if not config.frameworks.allow_duplicates:
             for d1, d2 in itertools.combinations(
diff --git a/amlb/resources.py b/amlb/resources.py
index 8a37977c4..05ce506ad 100644
--- a/amlb/resources.py
+++ b/amlb/resources.py
@@ -194,8 +194,10 @@ def _constraints(self):
             constraints_file = [constraints_file]
 
         constraints = Namespace()
-        for ef in constraints_file:
-            constraints += config_load(ef)
+        for i, ef in enumerate(constraints_file):
+            # First constraint file should exist (usually the default one)
+            # Additional files (e.g., user overrides) are optional
+            constraints += config_load(ef, strict=(i == 0))
 
         for name, c in constraints:
             c.name = str_sanitize(name)
diff --git a/amlb/utils/config.py b/amlb/utils/config.py
index a95ac1b51..b1c97d824 100644
--- a/amlb/utils/config.py
+++ b/amlb/utils/config.py
@@ -47,9 +47,22 @@ def yaml_load(*_, **__):  # type: ignore[misc]
         )
 
 
-def config_load(path, verbose=False):
+def config_load(path, verbose=False, strict=False):
+    """Load a configuration file.
+
+    :param path: Path to the configuration file.
+    :param verbose: If True, log at INFO level instead of DEBUG when loading.
+    :param strict: If True, raise an error when the file doesn't exist.
+                   If False, log a warning/debug message and return empty Namespace.
+    :return: Namespace containing the configuration.
+    """
     path = normalize_path(path)
     if not os.path.isfile(path):
+        if strict:
+            raise FileNotFoundError(
+                f"Configuration file not found: `{path}`. "
+                f"Please check the path for typos or verify the file exists."
+            )
         log.log(
             logging.WARNING if verbose else logging.DEBUG,
             "No config file at `%s`, ignoring it.",
diff --git a/amlb/utils/os.py b/amlb/utils/os.py
index 131b559c0..36fd680cf 100644
--- a/amlb/utils/os.py
+++ b/amlb/utils/os.py
@@ -56,10 +56,11 @@ def dir_of(caller_file, rel_to_project_root=False):
         return abs_path
 
 
-def list_all_files(paths, filter_=None):
+def list_all_files(paths, filter_=None, strict=False):
     """
     :param paths: the directories to look into.
     :param filter_: None, or a predicate function returning True iff the file should be listed.
+    :param strict: If True, raise an error when a path doesn't exist.
     """
     filter_ = filter_ or (lambda _: True)
     all_files = []
@@ -76,6 +77,11 @@ def list_all_files(paths, filter_=None):
             if filter_(path):
                 all_files.append(path)
         else:
+            if strict:
+                raise FileNotFoundError(
+                    f"Path not found: `{path}`. "
+                    f"Please check the path for typos or verify it exists."
+                )
             log.warning("Skipping file `%s` as it doesn't exist.", path)
 
     return all_files
diff --git a/recover_results.py b/recover_results.py
index 62ca00e45..35dfe7e0b 100644
--- a/recover_results.py
+++ b/recover_results.py
@@ -29,7 +29,7 @@
 amlb.logger.setup(root_level="DEBUG", console_level="INFO")
 
 root_dir = os.path.dirname(__file__)
-config = config_load(os.path.join(root_dir, "resources", "config.yaml"))
+config = config_load(os.path.join(root_dir, "resources", "config.yaml"), strict=True)
 config_args = ns.parse(
     root_dir=root_dir,
     script=os.path.basename(__file__),
diff --git a/runbenchmark.py b/runbenchmark.py
index 431e865ef..3adef3085 100644
--- a/runbenchmark.py
+++ b/runbenchmark.py
@@ -277,14 +277,16 @@
 log.debug("Script args: %s.", args)
 
 config_default = config_load(
-    os.path.join(default_dirs.root_dir, "resources", "config.yaml")
+    os.path.join(default_dirs.root_dir, "resources", "config.yaml"),
+    strict=True,  # Default config must exist
 )
 config_default_dirs = default_dirs
 # allowing config override from user_dir: useful to define custom benchmarks and frameworks for example.
 config_user = config_load(
     extras.get(
         "config", os.path.join(args.userdir or default_dirs.user_dir, "config.yaml")
-    )
+    ),
+    strict=False,  # User config is optional
 )
 # config listing properties set by command line
 config_args = ns.parse(
diff --git a/tests/conftest.py b/tests/conftest.py
index 3f93aea90..211baa78b 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -9,7 +9,8 @@
 @pytest.fixture
 def load_default_resources(tmp_path):
     config_default = config_load(
-        os.path.join(default_dirs.root_dir, "resources", "config.yaml")
+        os.path.join(default_dirs.root_dir, "resources", "config.yaml"),
+        strict=True,  # Default config must exist
     )
     config_default_dirs = default_dirs
     config_test = Namespace(
diff --git a/tests/unit/amlb/benchmarks/test_strict_loading.py b/tests/unit/amlb/benchmarks/test_strict_loading.py
new file mode 100644
index 000000000..cfcd8f597
--- /dev/null
+++ b/tests/unit/amlb/benchmarks/test_strict_loading.py
@@ -0,0 +1,23 @@
+import pytest
+from amlb.benchmarks.file import load_file_benchmark
+
+
+def test_missing_benchmark_file_raises_error():
+    """Missing benchmark file should raise ValueError when finding it, then FileNotFoundError when loading it."""
+    with pytest.raises(ValueError) as exc_info:
+        load_file_benchmark("nonexistent_benchmark", ["/tmp/nonexistent_dir"])
+
+    error_message = str(exc_info.value)
+    assert "incorrect benchmark" in error_message.lower()
+
+
+def test_benchmark_file_with_typo_in_path_raises_error():
+    """If a full path to benchmark is provided but has a typo, it should raise ValueError."""
+    with pytest.raises(ValueError) as exc_info:
+        load_file_benchmark(
+            "/tmp/nonexistent_benchmark_with_typo.yaml",
+            ["/tmp"],  # directory exists, but file doesn't
+        )
+
+    error_message = str(exc_info.value)
+    assert "incorrect benchmark" in error_message.lower()
diff --git a/tests/unit/amlb/frameworks/definitions/test_strict_loading.py b/tests/unit/amlb/frameworks/definitions/test_strict_loading.py
new file mode 100644
index 000000000..1a03e27a3
--- /dev/null
+++ b/tests/unit/amlb/frameworks/definitions/test_strict_loading.py
@@ -0,0 +1,57 @@
+import os
+import pytest
+import tempfile
+from amlb.frameworks.definitions import load_framework_definitions
+
+here = os.path.realpath(os.path.dirname(__file__))
+res = os.path.join(here, "resources")
+
+
+@pytest.mark.use_disk
+def test_missing_framework_file_raises_error(simple_resource):
+    """Missing base framework file should raise FileNotFoundError."""
+    with pytest.raises(FileNotFoundError) as exc_info:
+        load_framework_definitions(
+            "/tmp/nonexistent_frameworks.yaml", simple_resource.config
+        )
+
+    error_message = str(exc_info.value)
+    assert "not found" in error_message.lower()
+    assert "typo" in error_message.lower()
+
+
+@pytest.mark.use_disk
+def test_missing_tagged_framework_file_is_tolerated(simple_resource):
+    """Missing tagged variant files (e.g., frameworks_stable.yaml) should be tolerated."""
+    # Create a minimal framework file
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".yaml", delete=False) as f:
+        f.write("""
+TestFramework:
+  version: "1.0"
+""")
+        temp_file = f.name
+
+    try:
+        # This should work even if tagged variants don't exist
+        # (e.g., frameworks_stable.yaml, frameworks_latest.yaml, etc.)
+        definitions_by_tag = load_framework_definitions(
+            temp_file, simple_resource.config
+        )
+
+        # Should have loaded at least the default tag
+        assert len(definitions_by_tag) >= 1
+    finally:
+        os.unlink(temp_file)
+
+
+@pytest.mark.use_disk
+def test_multiple_framework_files_first_must_exist(simple_resource):
+    """When loading multiple files, all base files must exist."""
+    existing_file = f"{res}/frameworks_inheritance.yaml"
+    nonexistent_file = "/tmp/nonexistent_frameworks.yaml"
+
+    # Both files in the list must exist at the base level
+    with pytest.raises(FileNotFoundError):
+        load_framework_definitions(
+            [existing_file, nonexistent_file], simple_resource.config
+        )
diff --git a/tests/unit/amlb/utils/config/test_config_load_strict.py b/tests/unit/amlb/utils/config/test_config_load_strict.py
new file mode 100644
index 000000000..47957a35f
--- /dev/null
+++ b/tests/unit/amlb/utils/config/test_config_load_strict.py
@@ -0,0 +1,57 @@
+import os
+import tempfile
+import pytest
+from amlb.utils.config import config_load
+from amlb.utils import Namespace
+
+
+def test_config_load_nonexistent_file_strict_false():
+    """Non-existent file with strict=False should return empty Namespace."""
+    result = config_load("/tmp/definitely_nonexistent_file_12345.yaml", strict=False)
+    assert isinstance(result, Namespace)
+    assert len(dir(result)) == 0  # Empty namespace
+
+
+def test_config_load_nonexistent_file_strict_true():
+    """Non-existent file with strict=True should raise FileNotFoundError."""
+    with pytest.raises(FileNotFoundError) as exc_info:
+        config_load("/tmp/definitely_nonexistent_file_12345.yaml", strict=True)
+
+    error_message = str(exc_info.value)
+    assert "not found" in error_message.lower()
+    assert "typo" in error_message.lower()  # Should mention checking for typos
+
+
+def test_config_load_existing_file_strict_false():
+    """Existing file with strict=False should load normally."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".yaml", delete=False) as f:
+        f.write("test_key: test_value\n")
+        temp_file = f.name
+
+    try:
+        result = config_load(temp_file, strict=False)
+        assert isinstance(result, Namespace)
+        assert result.test_key == "test_value"
+    finally:
+        os.unlink(temp_file)
+
+
+def test_config_load_existing_file_strict_true():
+    """Existing file with strict=True should load normally."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".yaml", delete=False) as f:
+        f.write("test_key: test_value\n")
+        temp_file = f.name
+
+    try:
+        result = config_load(temp_file, strict=True)
+        assert isinstance(result, Namespace)
+        assert result.test_key == "test_value"
+    finally:
+        os.unlink(temp_file)
+
+
+def test_config_load_default_is_strict_false():
+    """Default behavior should be strict=False for backward compatibility."""
+    result = config_load("/tmp/definitely_nonexistent_file_12345.yaml")
+    assert isinstance(result, Namespace)
+    assert len(dir(result)) == 0  # Empty namespace
diff --git a/upload_results.py b/upload_results.py
index 310f020b8..ae3b53173 100644
--- a/upload_results.py
+++ b/upload_results.py
@@ -88,7 +88,7 @@ def parse_args():
 
 def find_most_recent_result_folder() -> pathlib.Path:
     root_dir = pathlib.Path(__file__).parent
-    config = config_load(root_dir / "resources" / "config.yaml")
+    config = config_load(root_dir / "resources" / "config.yaml", strict=True)
     output_dir = pathlib.Path(config.output_dir or default_dirs.output_dir)
 
     def dirname_to_datetime(dirname: str) -> datetime: