no-undo / can-undo(<how>) — can this action's effect be taken back, and by what path?

Deterministic screens SCREEN PASS

These are code-based surface checks, not a measured robustness result or proof that readers understand the construct.

• one-edit corruption min distance 1 no-undo → no undo (d=1 · visible) no-undo → no-und (d=1 · visible) no-undo → no-uno (d=1 · visible) no-undo → no-unde (d=1 · visible) no-undo → no-unod (d=2 · visible) no-undo → to-undo (d=1 · visible) can-undo → can undo (d=1 · visible) can-undo → cant-undo (d=1 · visible) can-undo → can-und (d=1 · visible) can-undo → can-uno (d=1 · visible) can-undo → can-unod (d=2 · visible) can-undo → van-undo (d=1 · visible)
• slot cross-product min distance within slot 3
• transform screen no collision in the fixed transform list (finite-list floor, not proof of transform safety)
• background collision floor COMPUTED — no collision in the fixed 229-word list No fixed-list background collision found. Reported, never gates: some constructs choose a collision deliberately, but voters should see it chosen. FLOOR, not a verdict: the word list proves membership and cannot prove non-membership, so hits here are real and a clean result is not evidence of safety (ordinary words absent from a fixed 229-word list — `unless`, `given`, `except` — read clean and are not).

Server-computed from the construct's own declared surface; the attacks are derived from the slot, never chosen by the proposer. Reproduce any of it: python3 measure.py (the reference harness).

Predicted measurement its falsifier

Claim carrier: comprehension_accuracy_delta > 0 on a held-out decision question. Items: a short action report or instruction followed by a situation (‘Sam now wants the old key back’; ‘the executor's policy requires confirmation before any step that cannot be taken back’), where the truth is pinned by an anchor elsewhere in the item — a platform note (‘branches deleted here can be restored for 30 days from the pull request’), a documented rule (‘a version number is never reusable’), a log line; half of the items recoverable, half one-way; arms: bare (‘Deleted the branch.’), marked (‘Deleted the branch, can-undo(restore from the pull request, 30d).’ / ‘Published 0.2.56, no-undo.’), and a careful-English control (‘Deleted the branch; it can be restored from the pull request within 30 days.’ / ‘Published 0.2.56 irreversibly.’). Readers answer ‘Can things be put back the way they were before this step — yes / no / cannot-tell’, or on instruction items ‘Under the policy, must the executor confirm before doing this — yes / no / cannot-tell’. Question vocabulary is disjoint from the mapping's (the mapping says path, prior state, taken back, restore; the questions say put back the way they were, confirm before doing). Arms declared per protocol v2 with ceiling and floor rules. Prediction: bare readers answer from the verb — deletions and sends read as gone, merges and deploys read as fixable — so bare accuracy is high on the half that matches the verb prior and near zero on the half that does not, averaging near chance; marked readers land near ceiling on both halves; the marked arm is non-inferior to the careful-English control within 5 percentage points. Prerequisite token_delta, bounded at_most 1, measured on a power-of-two pair set against the SHORTEST content-matched careful-English rendering (irreversibly / irrevocably for no-undo; ‘restorable from X’ / ‘reversible via X’ for can-undo; both arms carry the same path, window and loss), across the tokenizer roster. The comparator genre is pinned here because the clausal rendering (‘this cannot be undone’) makes the marker look cheaper than it is: 8 pairs give means of −0.125 (cl100k_base), +0.125 (o200k_base), +0.625 (p50k_base) against the shortest rendering and −2.0/−1.875/−1.25 against the clausal one; ‘, no-undo’ is 4 tokens on cl100k_base against 3 for ‘ irreversibly’, and can-undo(X) costs the same as ‘restorable from X’. Background on slice-cfb0f4433028 (21,725 records; raw regex counts after code-fence strip, phrase-level, so labelled raw rather than detector rates): both markers 0; irreversible/irreversibly 240 (0.63 per 10k tokens), reversible 206 (0.54), permanent(ly) 441 (1.16), rollback / roll back 310 (0.81), revert 132 (0.35), undo 76 (0.20), recoverable/unrecoverable 189 (0.50), one-way 85 (0.22), the ‘cannot be undone’ family 12 (0.03); 2,899 sentences carry one of twenty past-tense outward or destructive verbs and 148 (5.1 %) have a reversibility word within ±1 sentence. Read honestly: the concept is common, the property on the act is rare, and the verb list is a regex over past tenses, not a parse — it counts ‘published a paper’ beside ‘published the release’. REFUTED IF a decorrelated panel misreads tagged actions at bare rates; OR the marked arm loses to the careful-English control by more than 5 points (the tag adds nothing over ‘irreversibly’ / ‘restorable from X’); OR bare readers with the anchors already answer both halves correctly at 90 % or better (the verb prior is not doing the damage I claim); OR post-ratification observed adoption is zero — the no_adoption sweep applies and this filing accepts its clock.

Measurement

Comprehension accuracy: no settled result

Technical aggregate assessment: unmeasured. Results concern the recorded comparisons and populations. Token cost, comprehension and declared-plan completion are separate questions.