`BasePlatformAdapter.send_multiple_images` passes `metadata=metadata` to
`send_image` / `send_image_file` / `send_animation` on every send. The
WhatsApp and email `send_image` overrides stopped their signature at
`reply_to`, so any image delivered as a URL (the common case — image-gen
backends return URLs) raised:
TypeError: send_image() got an unexpected keyword argument "metadata"
and the image silently failed to send. Their sibling overrides
(`send_image_file` / `send_video` / `send_voice` / `send_document`)
already absorb it via **kwargs, which is why only plain image-URL sends
broke.
- whatsapp/email `send_image`: accept `metadata` (matches the base
signature); WhatsApp forwards it to the super() text fallback.
- Add `tests/gateway/test_media_metadata_contract.py`: asserts WhatsApp +
email accept it, plus a best-effort sweep over every adapter so the next
slip fails at test time instead of in production.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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