hermes - 💡(How to fix) Fix FAL Veo 3.1 video generation sends duration as "4" but API expects "4s"

Bug description

The bundled FAL video generation plugin appears to send Veo 3.1 duration as a bare numeric string such as "4". FAL's current fal-ai/veo3.1 endpoint validates this field as a literal enum with an s suffix: "4s", "6s", or "8s".

Steps to reproduce

1. Configure video_gen with provider fal and model veo3.1.
2. Call the video_generate tool with a simple text prompt and duration=4.
3. Observe the FAL queue request failing with HTTP 422.

Actual behavior

The request fails with a validation error similar to:

FAL video generation failed: [{'type': 'literal_error', 'loc': ['body', 'duration'], 'msg': "Input should be '4s', '6s' or '8s'", 'input': '4', 'ctx': {'expected': "'4s', '6s' or '8s'"}}]

Expected behavior

The FAL plugin should send duration in the format expected by the target endpoint, e.g. "4s" for Veo 3.1.

Local workaround tested

In plugins/video_gen/fal/__init__.py, changing payload construction from:

payload["duration"] = str(clamped)

to:

payload["duration"] = f"{clamped}s"

and parsing the success response duration by stripping a trailing s made a 4s fal-ai/veo3.1 generation succeed.

Environment

• Hermes checkout commit: 9f182bd7b
• OS: Ubuntu 24.04 / Linux
• Provider: FAL
• Model family: veo3.1