diff --git a/features/steps/tdd_validation_attach_named_options_steps.py b/features/steps/tdd_validation_attach_named_options_steps.py
index 0a56c112f..940269b15 100644
--- a/features/steps/tdd_validation_attach_named_options_steps.py
+++ b/features/steps/tdd_validation_attach_named_options_steps.py
@@ -115,15 +115,19 @@ def step_named_opts_attach_succeeds(context: Context) -> None:
 def step_named_opts_received_coverage_threshold(
     context: Context, expected_val: str
 ) -> None:
-    """Verify the service received coverage-threshold in the args dict."""
+    """Verify the service received coverage_threshold in the args dict.
+
+    The CLI converts hyphens in option names to underscores when forwarding
+    to the service layer (``--coverage-threshold`` → ``coverage_threshold``).
+    """
     call_kwargs = context.named_opts_mock_service.attach_validation.call_args
     assert call_kwargs is not None, "attach_validation was not called"
     args_dict = call_kwargs.kwargs.get("args") or {}
-    assert "coverage-threshold" in args_dict, (
-        f"Expected 'coverage-threshold' in args, got: {args_dict}"
+    assert "coverage_threshold" in args_dict, (
+        f"Expected 'coverage_threshold' in args, got: {args_dict}"
     )
-    assert args_dict["coverage-threshold"] == expected_val, (
-        f"Expected coverage-threshold={expected_val!r}, got {args_dict['coverage-threshold']!r}"
+    assert args_dict["coverage_threshold"] == expected_val, (
+        f"Expected coverage_threshold={expected_val!r}, got {args_dict['coverage_threshold']!r}"
     )
 
 
diff --git a/robot/helper_validation_attach_named_options.py b/robot/helper_validation_attach_named_options.py
index 5c7159467..ea322b792 100644
--- a/robot/helper_validation_attach_named_options.py
+++ b/robot/helper_validation_attach_named_options.py
@@ -82,8 +82,8 @@ def attach_with_coverage_threshold() -> None:
         sys.exit(1)
 
     args_dict = call_kwargs.kwargs.get("args") or {}
-    if args_dict.get("coverage-threshold") != "90":
-        print(f"FAIL: expected args={{'coverage-threshold': '90'}}, got {args_dict!r}")
+    if args_dict.get("coverage_threshold") != "90":
+        print(f"FAIL: expected args={{'coverage_threshold': '90'}}, got {args_dict!r}")
         sys.exit(1)
 
     print("validation-attach-named-option-coverage-threshold-ok")
diff --git a/src/cleveragents/cli/commands/validation.py b/src/cleveragents/cli/commands/validation.py
index 5a4c0b47a..8fea9a511 100644
--- a/src/cleveragents/cli/commands/validation.py
+++ b/src/cleveragents/cli/commands/validation.py
@@ -291,18 +291,19 @@ def attach(
 ) -> None:
     """Attach a validation to a resource.
 
-    Extra validation arguments are passed as named options using ``--key value``
-    format (e.g. ``--coverage-threshold 90``).  The ``--`` prefix is stripped
-    and the remaining key/value pairs are forwarded to the validation service.
-
     The validation mode (required or informational) is determined by the
     validation's registered definition, not overridden at attach time.
 
+    Validation-specific arguments are passed as named options using the
+    ``--key value`` format (e.g. ``--coverage-threshold 90``).  Hyphens in
+    option names are converted to underscores in the stored argument dict
+    (e.g. ``--coverage-threshold`` becomes ``coverage_threshold``).
+
     Examples:
         agents validation attach git-checkout/my-repo local/coverage-check
         agents validation attach --project myproj git-checkout/my-repo local/lint
-        agents validation attach git-checkout/my-repo local/coverage-check \
-            --coverage-threshold 90
+        agents validation attach --project local/api-service \\
+            local/api-repo local/run-tests --coverage-threshold 90
     """
     try:
         # Parse extra named options from ctx.args (--key value pairs).
@@ -315,15 +316,20 @@ def attach(
             while i < len(raw_extra):
                 token = raw_extra[i]
                 if token.startswith("--"):
-                    key = token[2:]  # strip leading "--"
+                    key = token[2:].replace(
+                        "-", "_"
+                    )  # --coverage-threshold → coverage_threshold
                     if not key:
                         console.print(
                             "[red]Invalid option:[/red] bare '--' is not allowed"
                         )
                         raise typer.Abort()
-                    # Next token is the value
-                    if i + 1 >= len(raw_extra):
-                        console.print(f"[red]Missing value for option:[/red] {token}")
+                    # Next token is the value (must not be another --flag)
+                    if i + 1 >= len(raw_extra) or raw_extra[i + 1].startswith("--"):
+                        console.print(
+                            f"[red]Missing value for option:[/red] {token} "
+                            "(expected --key value, e.g. --coverage-threshold 90)"
+                        )
                         raise typer.Abort()
                     val = raw_extra[i + 1]
                     extra_args[key] = val