Lightning Network Daemon version 0.21.5-beta.rc1, released as a candidate build on October 22, introduces a safeguard against unusually high external fee estimates. The update applies a ceiling of 10,000 satoshis per virtual byte to values supplied by external fee-estimation services.
The fee-estimate change addresses a gap in existing protections. External estimates previously had a lower bound but lacked an upper limit, allowing extreme values to flow into fee-sensitive wallet operations. The new ceiling acts as a guardrail against such outliers without implying that fees at this level are normal or economically necessary under current network conditions.
External fee estimates serve as inputs to wallet decisions rather than mandatory instructions. According to the release notes, a service can return unusable values due to errors, changed data formats, or compromised dependencies. Bounding the input limits the ways upstream problems can affect wallet behavior.
The candidate build also addresses a native SQL connection-pool deadlock. Node reliability depends on storage behavior as well as network communication; a process that continues running while requests stop completing can still fail applications that depend on it.
As a pre-release, the build requires testing across actual deployment conditions. The release notes specify that no database migration is required and provide signature and binary-verification instructions. Testing should cover the service's actual operations including request handling, storage access, failure handling, and clean restarts.
