Gotchas

Use this page only for library-specific caveats.

Use the shared KV Host Link Troubleshooting & Codes page for common connection, profile, address-shape, write-permission, and PLC error-code symptoms.

Current library-specific caveats

Area	Symptom	Guidance
RDC comments	A comment read returns a protocol decode error.	Select Utf8 or Cp932 explicitly from application knowledge, or use read_comment_bytes; the library never guesses or falls back.
Custom write formatter	A custom value is rejected before transport.	Return Ok(token) only for a validated supported suffix and propagate HostLinkError for every invalid value or suffix; empty fallback tokens are not supported.
Bit-in-word write	write_bit_in_word or write_bit_in_expansion_unit_buffer can overwrite another change to the same word.	They are explicit two-request, non-PLC-atomic operations. Use PLC-side coordination or exclusive whole-word ownership, and never automatically retry after a post-write future drop or outcome-unknown state.