UAX #14 rev. 57, Section 9.2: does Legacy-CM intentionally keep the LB8 break inside ZW SP CM?

Legacy-CM changes a space that is the base of a combining mark to ID only in rules following LB8. For ZERO WIDTH SPACE, SPACE and a combining mark, LB8 gives a break before the mark before the tailoring applies, so the break falls inside SP CM*, which Section 9.2 describes as an indivisible cluster under the earlier practice.

Consequence

U+200B, U+0020, U+0301, U+0062: under Legacy-CM a line may start with the combining mark.

Proposed correction

If the exception is intended, state it in Section 9.2.

Issued by

Unicode Consortium — Unicode Technical Committee

Act

UAX #14 revision 57 (Unicode 18.0.0)

Place

Section 9.2, Legacy-CM

Record

Question of reading or data

Class

Question of reading or data

Where it arose

The text of the act

Arxo's conclusion

Confirmed

Official text

Unchanged at last check

Last checked

2026-10-31

Evidence

Contradiction within the text. Quotations are verbatim from the official material; translations are ours and marked.

Legacy-CM: In all of the rules following rule LB8, if a space is the base character for a combining mark, the space is changed to type ID.

LB8 Break before any character following a zero-width space, even if one or more spaces intervene. ZW SP* ÷

Previously, whenever the base character was SP, the sequences CM* and SP CM* were defined to act like indivisible clusters

How to check it without Arxo's tools

1. Open UAX #14 revision 57 (Unicode 18.0.0), Unicode Consortium and find Section 9.2, Legacy-CM; rule LB8. Compare the text with the quotation above. A copy is kept in this register: 296df5332aefe695-tr14-57.html (SHA-256 296df5332aefe695b4951b511288b118bc6a7b43db7fadfd60f6062096acc7c0, copy of the official file).
2. The finding holds if the quoted passages read as shown and the comparison gives the result stated at the top of this page. If it does not, write to us with the record ID.

How this finding was made

AI agents read the annexes and the data files and compared them; the examples were run through published implementations. An AI coordinator checked each place against the full annex and the trackers, and two further AI models checked the report before filing.

Responsible institutions

• Unicode Consortium — publishes the annex and the Unicode Character Database

Reported to

Responses

No response recorded.

History

1. 2026-10-31Confirmed by Arxo
2. 2026-10-31Entered in the register
3. 2026-10-31Reported to Unicode Consortium (e-mail)

Cite this record

Arxo Law, Arxo Findings Register, ARXO-2026-0465, https://arxo.io/findings/ARXO-2026-0465/ (status as of 2026-10-31). Data: ARXO-2026-0465.json.