Discord raised the default file upload limit from 10 MiB to 20 MiB for
users, bots, webhooks and interaction responses (developer changelog,
Sep 3 2026). The 25 MiB constant here predates the preflight salvage and
never matched the platform; more importantly discord.py 2.7.1 still
reports 10 MiB via guild.filesize_limit for unboosted guilds, so the
guild-aware path under-reported the cap and rejected 10-20 MiB files
Discord now accepts. Floor the guild value at the platform default so a
stale library constant can only widen, never shrink, the preflight.
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