Upstream migration 20260324102005_repurpose_response_bot_flag_for_custom_tools
calls InstallationConfig.value before the normalization migration
(20260418020000) runs. On instances whose serialized_value column holds
native jsonb hashes, that read raises "TypeError: no implicit conversion of
Hash into String" and aborts the whole migration chain, leaving db:migrate
stuck and production unable to deploy.
Restore SerializedValueCoder.load that tolerates either shape. dump is
updated to always emit YAML strings so new writes converge on the upstream
format; the 20260418020000 migration still normalizes the backlog.
c9b1917886