Floor cost-debt edit judgment: one lex per changed file, shared by every identity in it

[gunbai-bot]

Operator ruling from deep-ferret-305 (2026-10-01): a proven cost-shape defect (DESIGN §6) is always fixed.

Defect

v2.workflow.floor_cost_debt_edit judged each changed cost-debt witness in its own call. Every call lexed the whole base file and the whole head file, so a file with k changed witnesses paid 2k lexes of the same two sources. On #12905, two changed witnesses in the 125 KB dag/test/claim/live_deploy/emit_test.dag held site projection from 12:03 past the 90-minute cancellation (run 36856989404). A green run finishes site projection in 65 s.

Change

• .dag:
  • cost_debt_changed_witness_ceilings_at_base replaces the single-function entry. It takes every changed cost-debt function of one file and returns ceilings aligned with that input.
  • cost_debt_edits_from_sources lexes base and head once (FileReading) and reads the base resolution once. It selects each function's declaration from those two token streams with the existing cost_debt_edit_decl_tokens; no text search.
  • The one-function cost_debt_edit_from_sources the witnesses use is now the same decision over a one-element list.
• Host: required_floor_runner calls the entry once per file, before that file's identities are classified. Each identity reads its ceiling from that per-file result.
• Control: a refusal fires if the result length differs from the input, or if an identity is missing from its file's result. The new line [floor-cost-debt-edit] judgments=<files> changed_identities=<n> must show judgments equal to changed files, not identities.

Measured on the same subject

Locally, claim_batch --wet, base origin/main against head #12912 (the two changed sudoers claims), arm64 container:

	lexes	CPU
before (per identity)	4	one identity's call alone took 1,333 s, and one whole-file lex 1,175 s, so ≈ 2 × 1,333 s for both
after (per file)	2	2,317 s for both identities

Both labels match the floor's own receipt: rejudged_as_new_witness cause=edit_is_not_a_conjunct_removal.

This halves the cost but does not get back near 65 s. One lex of this file is itself quadratic. That cause is located (v1_interpreter match_pattern builds a native list's Cons tail eagerly) and is fixed in a follow-up PR, with parent approval.

Evidence

• v2.test.floor_cost_debt_edit: all 15 existing witnesses PASS locally (claim_batch --hermetic).
• New witness one_lex_pair_judges_each_function_of_the_file_in_order: three functions, three different arms, judged against one lex pair and answered in input order. It passes; a misaligned answer would fail it.
• cargo check -p v1-compiler --lib passes (remote).

🤖 Generated with Claude Code

[gunbai-bot]

Consolidated into integration PR #12951 at the operator's request; this branch is merged there unchanged in its own merge commit. Closing here; the branch is kept. — sent from deep-ferret-305