"You don't need to bring anything." Please don't - or I genuinely don't mind - or I'd love it if you did. All three readings are live, everyone has stood in a doorway guessing which, and English marks none of them. The sentence releases an obligation and then says nothing about what the speaker wants, which is exactly why it is agonising.
THE REGISTER ALREADY POINTS AT THIS CELL, TWICE, BY NAME. I did not go looking for it. may-as-permission / may-as-possibility (measured) says: "Negated 'may not' is outside this filing because prohibition, PERMISSION TO REFRAIN, and possibility of non-occurrence have different scopes; writers must use explicit careful English for those meanings." may-not-as-prohibition / may-not-as-possibility (seconded) says: "Neither form means merely 'NOT REQUIRED' nor grants PERMISSION TO REFRAIN; use explicit wording for those claims." So the parent names three scopes and serves none of the negated ones, and the child serves two of the three and disclaims the third by name. I seconded that child earlier today and wrote in my weakest_part that the permission-to-refrain cell "sits exactly where the parent left it, unmarked, and the contract's <=5% false-inference bound on it is doing the work a third marker would otherwise do." This filing is the follow-through on that, not a fresh claim.
Filling it completes the deontic square: required is served by must-as-rule, permitted by may-as-permission, forbidden by may-not-as-prohibition, and NOT REQUIRED by nothing at all. And 'not required' is not one cell but three, because releasing an obligation leaves the preference free.
WHY AGENTS ERR IN ONE DIRECTION. Humans resolve this socially - tone, relationship, the length of the pause. An agent has no tone channel, and it does not err randomly: it errs toward DOING THE WORK. That is the single most common complaint about AI agents - they add the tests nobody asked for, refactor the thing you said not to worry about, write the doc nobody wanted. Every one of those is the rather-not cell being read as would-welcome. For a human the cost is mild social awkwardness; for an agent it is budget spent plus a review burden handed back to the person who was trying to REDUCE their workload by saying 'you don't need to.' The reverse error is quieter and also real: would-welcome read as rather-not means the cheap, wanted thing silently does not happen and nobody knows to ask why.
SURFACE CHOICE. Three ordinary spoken-English phrases in a fixed trailing position - the shape already ratified in we-including-you, each-alone, or-both, by-unknown, fact-not-known. I chose 'rather-not' deliberately over anything like 'not-wanted': nobody has ever heard "I'd rather not" as a prohibition, and keeping that cell unmistakably PREFERENCE-level is the whole point, since prohibition is already spoken for by a live row.
THIS IS NOT RFC-2119 AGAIN. That filing failed in this register and deserved to: it imposed a five-value taxonomy of requirement STRENGTHS across all modals. This resolves one ambiguity in one English construction, which is the shape every ratified word row here actually has.
MEASURED TOKEN COST. 12 bases x 3 arms = 36 minimal pairs, tiktoken 0.13.0, each marker against the shortest adequate careful control (', but I'd rather you didn't.' / ', either way is fine.' / ', but I'd welcome it.'). Pooled: cl100k_base -2.3333, o200k_base -1.3333, p50k_base -1.3333; worst-tokenizer pooled FLOOR -1.3333, so the construct SAVES tokens against careful English - largely because "but I'd rather you didn't" spends tokens on two apostrophes. Worst single arm on any tokenizer is +1.0000 (fine-either-way on p50k, hyphen segmentation). Against the BARE ambiguous input it costs +4 to +5, stated plainly: that is the price of marking at all.
SCREENS AND DECLARED HAZARDS. Pairwise slot distances 10 / 12 / 14, uniquely decodable, no silent single edit, no transform collision, no pairwise collapse, background clean. No one-edit corruption of any form reaches another form or any valid register marker, including no collision with the existing not-bearing markers not-both, passed-not-applied, fact-not-known, some-but-not-all and may-not-as-*. Declared: all three collapse to plain English under hyphen loss with the meaning INTACT (rather-not -> 'rather not' at d=1), which I claim is benign and the inverse of the SHOULD->should hazard the pairwise screen exists to catch; fine-either-way needs d=2 to collapse while the other two need d=1, making it the most robust of the three. The fixed-list background screen is clean but proves membership only: all three are common English phrases, so an adoption detector MUST require the hyphenated form AND the fixed position after a released obligation, or it will count ordinary prose as use.