Add experimental crewai run --definition for flows (#6147)

Let users run a Flow from a Flow Definition YAML file or inline string
without writing Python, passing kickoff inputs as `--inputs` JSON. The
flag is gated behind an experimental warning since the definition format
may still change.

lib/cli/src/crewai_cli/cli.py

@@ -26,6 +26,7 @@ from crewai_cli.remote_template.main import TemplateCommand
 from crewai_cli.replay_from_task import replay_task_command
 from crewai_cli.reset_memories_command import reset_memories_command
 from crewai_cli.run_crew import run_crew
+from crewai_cli.run_flow_definition import run_flow_definition
 from crewai_cli.settings.main import SettingsCommand
 from crewai_cli.task_outputs import load_task_outputs
 from crewai_cli.tools.main import ToolCommand
@@ -398,8 +399,36 @@ def install(context: click.Context) -> None:
         "CREWAI_TRAINED_AGENTS_FILE."
     ),
 )
-def run(trained_agents_file: str | None) -> None:
-    """Run the Crew."""
+@click.option(
+    "--definition",
+    type=str,
+    default=None,
+    help=(
+        "Experimental: path to a Flow Definition YAML/JSON file, "
+        "or an inline YAML/JSON string."
+    ),
+)
+@click.option(
+    "--inputs",
+    type=str,
+    default=None,
+    help='Experimental: JSON object passed to flow.kickoff(), e.g. \'{"topic":"AI"}\'.',
+)
+def run(
+    trained_agents_file: str | None, definition: str | None, inputs: str | None
+) -> None:
+    """Run the Crew or Flow."""
+    if inputs is not None and definition is None:
+        raise click.UsageError("--inputs requires --definition")
+
+    if definition is not None:
+        click.secho(
+            "Warning: `crewai run --definition` is experimental and may change without notice.",
+            fg="yellow",
+        )
+        run_flow_definition(definition=definition, inputs=inputs)
+        return
+
     run_crew(trained_agents_file=trained_agents_file)
 
 

lib/cli/src/crewai_cli/run_flow_definition.py

@@ -0,0 +1,113 @@
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+import click
+
+
+def run_flow_definition(definition: str, inputs: str | None = None) -> None:
+    """Run a flow from a Flow Definition YAML/JSON string or file path."""
+    try:
+        from crewai.flow.flow import Flow
+        from crewai.flow.flow_definition import FlowDefinition
+    except ImportError as exc:
+        click.echo(
+            "Running flows from definitions requires the full crewai package.",
+            err=True,
+        )
+        raise SystemExit(1) from exc
+
+    parsed_inputs = _parse_inputs(inputs)
+    definition_source = _read_definition_source(definition)
+
+    try:
+        flow_definition = _parse_flow_definition(FlowDefinition, definition_source)
+        flow = Flow.from_definition(flow_definition)
+        result = flow.kickoff(inputs=parsed_inputs)
+    except Exception as exc:
+        click.echo(
+            f"An error occurred while running the flow definition: {exc}", err=True
+        )
+        raise SystemExit(1) from exc
+
+    click.echo(_format_result(result))
+
+
+def _parse_inputs(inputs: str | None) -> dict[str, Any] | None:
+    if inputs is None:
+        return None
+
+    try:
+        parsed = json.loads(inputs)
+    except json.JSONDecodeError as exc:
+        click.echo(f"Invalid --inputs JSON: {exc}", err=True)
+        raise SystemExit(1) from exc
+
+    if not isinstance(parsed, dict):
+        click.echo("Invalid --inputs JSON: expected an object.", err=True)
+        raise SystemExit(1)
+
+    return parsed
+
+
+def _read_definition_source(definition: str) -> str:
+    path = Path(definition).expanduser()
+    try:
+        is_file = path.is_file()
+    except OSError as exc:
+        if _looks_like_inline_definition(definition):
+            return definition
+        click.echo(f"Invalid --definition path: {definition} ({exc})", err=True)
+        raise SystemExit(1) from exc
+
+    if is_file:
+        try:
+            return path.read_text(encoding="utf-8")
+        except (OSError, UnicodeError) as exc:
+            click.echo(
+                f"Unable to read --definition path {path}: {exc}",
+                err=True,
+            )
+            raise SystemExit(1) from exc
+
+    try:
+        if path.exists():
+            click.echo(
+                f"Invalid --definition path: {definition} is not a file.", err=True
+            )
+            raise SystemExit(1)
+    except OSError as exc:
+        click.echo(f"Invalid --definition path: {definition} ({exc})", err=True)
+        raise SystemExit(1) from exc
+
+    return definition
+
+
+def _looks_like_inline_definition(definition: str) -> bool:
+    stripped = definition.lstrip()
+    return "\n" in definition or stripped.startswith(("{", "---")) or ":" in stripped
+
+
+def _parse_flow_definition(flow_definition_cls: type[Any], source: str) -> Any:
+    if _looks_like_json(source):
+        return flow_definition_cls.from_json(source)
+
+    return flow_definition_cls.from_yaml(source)
+
+
+def _looks_like_json(source: str) -> bool:
+    stripped = source.lstrip()
+    return stripped.startswith("{")
+
+
+def _format_result(result: Any) -> str:
+    raw_result = getattr(result, "raw", result)
+    if isinstance(raw_result, str):
+        return raw_result
+
+    try:
+        return json.dumps(raw_result, default=str)
+    except TypeError:
+        return str(raw_result)