Same class as the Matrix readers: since 545e74d0 the WhatsApp YAML bridge seeds
`free_response_chats` into extra via the "csv" kind (any non-None value), so a
present-but-blank `free_response_chats: ''` reaches `_whatsapp_free_response_chats`
as '' and its `if raw is None` fallback never reads WHATSAPP_FREE_RESPONSE_CHATS.
Before 545e74d0 the hook returned None and the key never reached extra, so the
env CSV applied. Route it through the shared extra_or_secret reader (blank =
unset; an explicit empty list stays "no chats").
Sibling sweep of every "csv"-kind bridged key: dingtalk, mattermost and slack
readers already go through extra_or_secret and their bridges seeded extra before
0.21.2, so 008caa88 deliberately kept blank-means-clear there; whatsapp allow_from
uses key-presence semantics by design (_select_dm_allowlist); buzz reads env
first. Telegram allowed_chats: '' shadowing the env var is pre-existing (identical
on v2026.9.7, via the shared-key bridge) and left as is.
teknium1
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