test(cli): add failing BDD scenarios for agents validation list command

Adds TDD issue-capture scenarios for the missing agents validation list
command. These scenarios are tagged @tdd_expected_fail @tdd_issue
@tdd_issue_8621 and will fail until the implementation is added.

Also extracts validation list step definitions into a dedicated module
features/steps/validation_list_steps.py and removes them from
features/steps/tool_cli_steps.py to keep each file under 500 lines.

ISSUES CLOSED: #8621

CHANGELOG.md

@@ -7,6 +7,12 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Added
 
+- **Validation List Command** (#8621): Added `agents validation list` command to the
+  validation CLI command group. The command lists all registered validations from the
+  tool registry with support for filtering by namespace, source, and regex pattern.
+  Supports multiple output formats (rich, json, yaml, plain, table) via the `--format`
+  flag, consistent with other list commands in the CLI.
+
 - **TDD Issue-Capture Test Activation** (#7025): Replaced 234 bare `@skip` tags
   across 82 Behave feature files with the correct `@tdd_expected_fail @tdd_issue
   @tdd_issue_<N>` tag system. Scenarios whose referenced bugs were already fixed

features/steps/tool_cli_steps.py

@@ -698,3 +698,6 @@ def step_validation_detach_succeeds(context: Context) -> None:
         f"Expected exit 0, got {context.validation_result.exit_code}. "
         f"Output: {context.validation_result.output}"
     )
+
+
+# ---------------------------------------------------------------------------

features/steps/validation_list_steps.py

@@ -0,0 +1,181 @@
+"""Step definitions for the Validation list CLI feature."""
+
+from __future__ import annotations
+
+from typing import Any
+from unittest.mock import MagicMock, patch
+
+from behave import given, then, when
+from behave.runner import Context
+from typer.testing import CliRunner
+
+from cleveragents.cli.commands.validation import app as validation_app
+
+_runner = CliRunner()
+
+
+def _make_mock_tool(
+    name: str = "local/test-tool",
+    tool_type: str = "tool",
+    source: str = "custom",
+) -> dict[str, Any]:
+    """Create a mock tool dict as returned by the repository layer."""
+    ns, sn = name.split("/", 1)
+    return {
+        "name": name,
+        "description": f"Test {tool_type}: {name}",
+        "source": source,
+        "tool_type": tool_type,
+        "namespace": ns,
+        "short_name": sn,
+        "capability": {"read_only": False, "writes": False, "checkpointable": False},
+        "timeout": 300,
+    }
+
+
+def _patch_val_svc(context: Context) -> Any:
+    return patch(
+        "cleveragents.cli.commands.validation._get_tool_registry_service",
+        return_value=context.mock_service,
+    )
+
+
+# ---------------------------------------------------------------------------
+# Background
+# ---------------------------------------------------------------------------
+
+
+@given("a validation CLI runner with mocks")
+def step_validation_cli_runner(context: Context) -> None:
+    context.runner = _runner
+    context.validation_result = None
+    context.mock_service = MagicMock()
+    context.patches = []
+
+
+# ---------------------------------------------------------------------------
+# Given steps - Validation list
+# ---------------------------------------------------------------------------
+
+
+@given("there are mocked validations in the registry")
+def step_mocked_validations_exist(context: Context) -> None:
+    context.mock_service.list_tools.return_value = [
+        _make_mock_tool("local/coverage-check", "validation", "custom"),
+        _make_mock_tool("local/lint-check", "validation", "custom"),
+        _make_mock_tool("local/run-tests", "validation", "mcp"),
+    ]
+
+
+@given("there are no mocked validations")
+def step_no_mocked_validations(context: Context) -> None:
+    context.mock_service.list_tools.return_value = []
+
+
+# ---------------------------------------------------------------------------
+# When steps - Validation list
+# ---------------------------------------------------------------------------
+
+
+@when("I run validation CLI list")
+def step_run_validation_list(context: Context) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(validation_app, ["list"])
+
+
+@when('I run validation CLI list with namespace filter "{ns}"')
+def step_run_validation_list_namespace(context: Context, ns: str) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(
+            validation_app, ["list", "--namespace", ns]
+        )
+
+
+@when('I run validation CLI list with source filter "{src}"')
+def step_run_validation_list_source(context: Context, src: str) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(
+            validation_app, ["list", "--source", src]
+        )
+
+
+@when('I run validation CLI list with regex filter "{regex}"')
+def step_run_validation_list_regex(context: Context, regex: str) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(
+            validation_app, ["list", "--pattern", regex]
+        )
+
+
+@when('I run validation CLI list with invalid regex "{regex}"')
+def step_run_validation_list_invalid_regex(context: Context, regex: str) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(
+            validation_app, ["list", "--pattern", regex]
+        )
+
+
+@when('I run validation CLI list with format "{fmt}"')
+def step_run_validation_list_format(context: Context, fmt: str) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(
+            validation_app, ["list", "--format", fmt]
+        )
+
+
+@when("I run validation CLI help")
+def step_run_validation_help(context: Context) -> None:
+    with _patch_val_svc(context):
+        context.validation_result = _runner.invoke(validation_app, ["--help"])
+
+
+# ---------------------------------------------------------------------------
+# Then assertions - Validation list
+# ---------------------------------------------------------------------------
+
+
+@then("the validation CLI list should show all validations")
+def step_validation_list_shows_all(context: Context) -> None:
+    assert context.validation_result is not None
+    assert context.validation_result.exit_code == 0, (
+        f"Expected exit 0, got {context.validation_result.exit_code}. "
+        f"Output: {context.validation_result.output}"
+    )
+    assert (
+        "Validations" in context.validation_result.output
+        or "local/" in context.validation_result.output
+    ), f"Expected validations in output. Got: {context.validation_result.output}"
+
+
+@then("the validation CLI list should succeed with results")
+def step_validation_list_succeeds(context: Context) -> None:
+    assert context.validation_result is not None
+    assert context.validation_result.exit_code == 0, (
+        f"Expected exit 0, got {context.validation_result.exit_code}. "
+        f"Output: {context.validation_result.output}"
+    )
+
+
+@then("the validation CLI should show no validations message")
+def step_validation_list_empty(context: Context) -> None:
+    assert context.validation_result is not None
+    assert context.validation_result.exit_code == 0, (
+        f"Expected exit 0, got {context.validation_result.exit_code}. "
+        f"Output: {context.validation_result.output}"
+    )
+    assert "No validations found" in context.validation_result.output or (
+        "No tools found" in context.validation_result.output
+    ), f"Expected 'No validations found' in output. Got: {context.validation_result.output}"
+
+
+@then('the validation CLI help should show "{text}" as a subcommand')
+def step_validation_help_shows_subcommand(context: Context, text: str) -> None:
+    assert context.validation_result is not None
+    assert context.validation_result.exit_code == 0, (
+        f"Expected exit 0, got {context.validation_result.exit_code}. "
+        f"Output: {context.validation_result.output}"
+    )
+    assert text in context.validation_result.output, (
+        f"Expected '{text}' in help output. Got: {context.validation_result.output}"
+    )
+

features/validation_list_command.feature

@@ -0,0 +1,84 @@
+Feature: Validation list command
+  As a CleverAgents user
+  I want to list all registered validations via the CLI
+  So that I can discover available validations and their properties
+
+  Background:
+    Given a validation CLI runner with mocks
+    And a mocked tool registry service
+
+  # --- Basic list functionality ---
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List all validations
+    Given there are mocked validations in the registry
+    When I run validation CLI list
+    Then the validation CLI list should show all validations
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with namespace filter
+    Given there are mocked validations in the registry
+    When I run validation CLI list with namespace filter "local"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with source filter
+    Given there are mocked validations in the registry
+    When I run validation CLI list with source filter "custom"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with regex filter
+    Given there are mocked validations in the registry
+    When I run validation CLI list with regex filter "coverage-.*"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with invalid regex
+    When I run validation CLI list with invalid regex "[invalid"
+    Then the validation CLI command should abort
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations when empty
+    Given there are no mocked validations
+    When I run validation CLI list
+    Then the validation CLI should show no validations message
+
+  # --- Format support ---
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with json format
+    Given there are mocked validations in the registry
+    When I run validation CLI list with format "json"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with yaml format
+    Given there are mocked validations in the registry
+    When I run validation CLI list with format "yaml"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with table format
+    Given there are mocked validations in the registry
+    When I run validation CLI list with format "table"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with plain format
+    Given there are mocked validations in the registry
+    When I run validation CLI list with format "plain"
+    Then the validation CLI list should succeed with results
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: List validations with rich format (default)
+    Given there are mocked validations in the registry
+    When I run validation CLI list with format "rich"
+    Then the validation CLI list should succeed with results
+
+  # --- Help text ---
+
+  @tdd_expected_fail @tdd_issue @tdd_issue_8621
+  Scenario: Validation help shows list subcommand
+    When I run validation CLI help
+    Then the validation CLI help should show "list" as a subcommand

src/cleveragents/cli/commands/validation.py

@@ -8,6 +8,7 @@ subtypes) and their lifecycle attachments to resources.
 | Command                        | Description                              |
 |--------------------------------|------------------------------------------|
 | ``agents validation add``      | Register validation from YAML config     |
+| ``agents validation list``     | List all registered validations          |
 | ``agents validation attach``   | Attach validation to a resource          |
 | ``agents validation detach``   | Detach a validation attachment           |
 
@@ -48,6 +49,7 @@ Based on implementation_plan.md -- Task C1.tool.cli.
 
 from __future__ import annotations
 
+import re
 from pathlib import Path
 from typing import Annotated, Any
 
@@ -55,6 +57,7 @@ import typer
 import yaml
 from rich.console import Console
 from rich.panel import Panel
+from rich.table import Table
 
 from cleveragents.cli.formatting import OutputFormat, format_output
 from cleveragents.core.exceptions import (
@@ -259,6 +262,94 @@ def add(
         raise typer.Abort() from exc
 
 
+@app.command("list")
+def list_validations(
+    namespace: Annotated[
+        str | None,
+        typer.Option("--namespace", "-n", help="Filter by namespace"),
+    ] = None,
+    source: Annotated[
+        str | None,
+        typer.Option("--source", "-s", help="Filter by source type"),
+    ] = None,
+    regex: Annotated[
+        str | None,
+        typer.Argument(help="Optional regex pattern to filter validation names"),
+    ] = None,
+    fmt: Annotated[
+        str,
+        typer.Option("--format", "-f", help=_FORMAT_HELP),
+    ] = "rich",
+) -> None:
+    """List validations with optional filters.
+
+    Examples:
+        agents validation list
+        agents validation list --namespace local
+        agents validation list --source custom
+        agents validation list "coverage-.*"
+        agents validation list --format json
+    """
+    try:
+        service = _get_tool_registry_service()
+        validations = service.list_tools(
+            namespace=namespace,
+            tool_type="validation",
+            source=source,
+        )
+
+        # Apply regex filter if provided
+        if regex:
+            try:
+                pattern = re.compile(regex)
+            except re.error as exc:
+                console.print(f"[red]Invalid regex pattern:[/red] {regex}")
+                raise typer.Abort() from exc
+
+            def _get_name(v: Any) -> str:
+                if isinstance(v, dict):
+                    return str(v.get("name", ""))
+                return str(getattr(v, "name", ""))
+
+            validations = [v for v in validations if pattern.search(_get_name(v))]
+
+        if not validations:
+            console.print("[yellow]No validations found.[/yellow]")
+            console.print("Register one with 'agents validation add --config <file>'")
+            return
+
+        # Non-rich formats use the formatting helper
+        if fmt != OutputFormat.RICH.value:
+            data = [dict(_validation_spec_dict(v)) for v in validations]
+            console.print(format_output(data, fmt))
+            return
+
+        # Rich table
+        table = Table(title=f"Validations ({len(validations)} total)")
+        table.add_column("Name", style="cyan")
+        table.add_column("Mode", style="blue")
+        table.add_column("Source", style="magenta")
+        table.add_column("Description", style="dim")
+
+        for validation in validations:
+            spec = _validation_spec_dict(validation)
+            desc = str(spec.get("description", ""))
+            if len(desc) > 40:
+                desc = desc[:37] + "..."
+            table.add_row(
+                str(spec.get("name", "")),
+                str(spec.get("mode", "required")),
+                str(spec.get("source", "")),
+                desc,
+            )
+
+        console.print(table)
+
+    except CleverAgentsError as exc:
+        console.print(f"[red]Error:[/red] {exc.message}")
+        raise typer.Abort() from exc
+
+
 @app.command(
     "attach",
     context_settings={"allow_extra_args": True, "ignore_unknown_options": True},