[altvnk]

Scoped completion claim

Units: surface.surface_p6.

In scope: add the existing real canonical radius-2 Sphere to this unit's generic
surface protocol, and one successful interior CreateNaturalUVTrimCurves fixture.
The current builders admit B-spline, Plane, Bounded and Revolution, but cannot
reach the existing Sphere iso-curve dispatch. No production algorithm is ported.

Expected edits:

• crates/difftest/src/units/surface_surface_p6.rs
• crates/solidcore-ffi/src/units/surface_surface_p6.rs
• harness/cpp/shim/surface_surface_p6.cpp
• fixtures/surface.surface_p6/sphere-natural-trim.json

Evidence: inspected main b206d3f5a38127dc3a0b6c511f1b45116826b341 lacks this
kind in its runner, FFI and native builder. A bounded, noncanonical Rust-only probe
constructed the actual Sphere and produced four spatial circles and four UV lines,
with finite complete samples on radius 2, orientations [2,1,1,2], zero gaps and
the expected rectangle boundaries. Actual NURB domain is [0,0,1,1]; the fixture
trim is [0.125,0.25,0.375,0.75], side U, remove=false, not angular STEP units.
This probe does not establish fresh-head or C++ parity.

Reviewed protocol: fixed canonical origin/X/Y/radius, new leaf tag 4, no payload
parameters. Support the ordinary recursive builder positions and existing operation
validation without a Sphere-specific whitelist. Preserve all old tag 0–3 branches,
guards and error ordering. The inherited B-spline-backed capability remains eligible
for the existing Scls filter; do not invent a plain-enum-kind refusal. Strong
four-edge/circle/geometry assertions belong only in this fixture's tests, never in
generic native admission or serialization. Existing dynamic trim records are reused.

Validation planned: focused identity/geometry/protocol/admission tests; complete
146-scalar native record comparison for the one ordinary fixture; an interior-only
perturbation control; the full unfiltered affected unit and its perturbation run;
formatting, CPP-enabled Clippy, independent exact-diff review, and all canonical
current-head gates including value-share and exact-base retention. Compile the
changed shim against the existing shared reference, read-only; no reference rebuild.
Any native mismatch, undefined-input concern or extra interface need blocks this
coverage-only scope rather than justifying a production change or narrower guard.

Preserve all 103 old fixtures, generator inputs/draws/seeds/minimum 2000, numerical
formulas, tolerances, floors, mismatch entries and status. No production, shared
interface, cache, plan, workflow or old-fixture edits.

Related PRs / dependencies: #1031 owns p8 boundary memoization and shared caches;
those paths/interfaces remain untouched. #1041 owns p9 analytic diagonal fixtures,
which are independent. #686's ellipse STEP/revolution work is not part of this scope.

Available follow-ups: other Sphere operations, poles, removal modes, wrapper
positions and other analytic kinds are not newly demonstrated by this fixture.
Generic admission is not a coverage claim for them.

Status / blockers / next step: scoped draft; implement the reviewed generic leaf
and one named fixture, establish native equivalence, then await exact-head canonical
CI. Maintainers retain workflow authorization, approval, queue admission and merging.

Published draft: exact-head evidence

Head 324fc862a7a44af221a5bbd60c31b10606bf9832, safely synchronized with authoritative main f4d002bb0a6dc5d49928a80213eb9ade8cdab7bd.
Independent FINAL review accepted fingerprint 13591b6c18c55463e342ee321222f98a14f074fe5703ef23a7e4dac9e4940767; reviewed
binary PR diff and all103oldfixtures/generator inputs remain unchanged across merge.

3 focused CPP runner tests and1FFI admission test passed
PASS surface.surface_p6 cases=2104 passed=2104 failed=0 deferred=0 max_rel_err=0e0 with_values=2104 no_values=0 vacuous=0
SENSITIVE surface.surface_p6 perturbed=2104 detected=2104 unperturbed=0 deferred=0
CPP-enabled Clippy both changed Rust crates, all-targets -D warnings: PASS
workspace formatting and diff checks: PASS

Operation / symbols	Implementation	Successful native comparison	Remaining gap
Sphere CreateNaturalUVTrimCurves, named interior U case	Generic real radius2 Sphere leaf added in unit-local builders; existing production operation unchanged	Complete146-scalar records compare with max relative error0; four spatial curved edges and four UV lines, orientations/gaps/radius2/UV-boundary checks; interior-only perturbation detected	Only this interior U/remove=false case adds geometry coverage; other admitted modes/wrappers/operations unproven

Rust tests assert concrete Sphere/Ellipse-circle/UV-Line identities. Native uses
real SmSphere construction; nondegenerate iso class identity is source-backed, not
a new runtime class export. Shared reference hashes/mtimes unchanged, no rebuild.
This is local macOS evidence, not canonical Linux or full completeness proof.
Ready for review by explicit user instruction; canonical CI is still pending.

User-authorized review status

Marked ready for review at the user’s request after local native validation and independent source review. Canonical CI was authorization-blocked at the latest audit; this transition does not claim green CI, approval, queue admission or merge readiness. Maintainer workflow authorization and all required checks remain mandatory. No source commit or workflow configuration changed.

[altvnk]

@bherbruck — exact published draft head 324fc862a passed independent final source review and local3CPP+1FFI tests, full native surface.surface_p6 2104/2104 cases, perturbation2104/2104, CPP-enabled Clippy and formatting. All103oldfixtures, generator inputs/seeds/min2000, guards and tolerances remain unchanged. Canonical run40248128556 requires authorization and has executed zero jobs. Please inspect/authorize it; draft remains pending all13 canonical jobs including native/value-share/exact-base retention. No technical CI failure or merge-readiness claim.

[bherbruck]

Approved by the automated first-pass review: CI green, mergeable, no CI/build/dependency file changes, no red-flag patterns in added code (process/network/env/unsafe outside FFI/blobs/hidden unicode), 0 known-mismatch entries added. Logic is gated by CI and the difftest merge queue.