Contributing: kernel operations migrate to solidcore; features call its API

AGENTS.md, CONTRIBUTING.md and the contributing skill say how the work is
split since 0.40: SolidCraft is the application and calls the solidcore API;
geometry math (evaluators, intersections, solvers, tessellation, kernel cases)
is added to solidcore first. New features are discussed on Discord, then get
an issue and a claim, after a search of all issues and pull requests, open and
closed, for similar work. Work begun before 0.40 is ported onto today's code
before it lands. The kernel-paused section becomes "Kernel work goes to
solidcore".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/kernel-paused.yml

@@ -1,6 +1,6 @@
 # While a new geometry kernel is evaluated, new issues and discussions about kernel work, and new
 # pull requests that change the kernel directories, are labelled `kernel-paused` for a maintainer to
-# answer (CONTRIBUTING.md, "Kernel work is paused"). The logic is in scripts/kernel-paused/ (tested
+# answer (CONTRIBUTING.md, "Kernel work goes to solidcore"). The logic is in scripts/kernel-paused/ (tested
 # in ci.yml).
 name: Kernel paused
 

AGENTS.md

@@ -3,7 +3,7 @@
 SolidCraft is a clean-room, pure-Rust parametric 3D CAD app (sketch solver, feature timeline, B-rep kernel, an egui UI that agents drive). This file is a router: the hard rules, then the skill to read for your task. Humans: CONTRIBUTING.md.
 
 ## Start here
-Work: ROADMAP.md, "Where help is wanted most" in CONTRIBUTING.md, issues labelled `help wanted`, `good first issue`, `needs-triage`; architecture in `docs/architecture.md`. Act when the code, docs and rules settle a question; ask only when it changes what users see. Local `plan/` notes are optional.
+Work: ROADMAP.md, "Where help is wanted most" in CONTRIBUTING.md, issues labelled `help wanted`, `good first issue`, `needs-triage`; architecture in `docs/architecture.md`. Act when the code, docs and rules settle a question; ask only when it changes what users see.
 
 ## Hard rules (what enforces each)
 - Independent: never copy another product's code, icons, text or templates; never drive or take data from commercial CAD. `skills/solidcraft-ground-rules/SKILL.md`.
@@ -11,7 +11,7 @@ Work: ROADMAP.md, "Where help is wanted most" in CONTRIBUTING.md, issues labelle
 - Every asset is original or openly licensed with a row in ATTRIBUTION.md; read `assets/AGENTS.md` before icon work: `cargo xtask assets`, `cargo xtask icons`.
 - Never crash: no unwrap/expect/panic/unsafe in non-test code (unsafe allowlist in crash-safety), errors are `Result`, input is hostile: clippy `-D warnings`, `hostile_params_never_panic`.
 - Model decisions (what an operation does, which bodies it touches, which face or edge a point or name means, depths, nearness) use exact geometry; a mesh is for display, export, previews and mesh bodies (`xtask/mesh-decisions.txt` only shrinks): `cargo xtask mesh-decisions`.
-- New kernel cases go to solidcore: `cargo xtask lists`.
+- Kernel ops and math go to solidcore; features call its API: `cargo xtask lists`.
 - Everything is a command and programmatic calls never open dialogs: `skills/solidcraft-commands/SKILL.md`.
 - Layering (geom, sketch/kernel/render, doc, io, engine, ui-egui, apps); only `crates/kernel` uses truck: `cargo xtask layers`.
 - One outer UI container, one camera path (`navigation::handle`), colours from theme tokens: `cargo xtask ui-containers`.
@@ -31,7 +31,7 @@ Work: ROADMAP.md, "Where help is wanted most" in CONTRIBUTING.md, issues labelle
 ## Working on X: read the skill first
 | Working on | Read |
 |---|---|
-| A PR, a claim, review, CI or evidence | `skills/solidcraft-contributing/SKILL.md` |
+| A feature, PR, claim, review, CI, evidence | `skills/solidcraft-contributing/SKILL.md` |
 | Licences, assets, clean-room, the name | `skills/solidcraft-ground-rules/SKILL.md` |
 | Non-test Rust, hostile input, a crash report | `skills/solidcraft-crash-safety/SKILL.md` |
 | A command, a crate boundary | `skills/solidcraft-commands/SKILL.md` |

CONTRIBUTING.md

@@ -17,15 +17,27 @@ Before choosing a task, check the [command inventory](docs/features.md) and
 
 Questions, ideas or want to say what you're working on? Join the [Discord](https://discord.gg/FtU4NQNVDH).
 
-## Kernel work is paused
+## Kernel work goes to solidcore
 
-We're moving to a new geometry kernel. Until that's done, please don't open pull requests that
+Since 0.40, SolidCraft's geometry kernel is [solidcore](https://github.com/tangency-labs/solidcore),
-change `crates/kernel/`, `crates/geom/` or `vendor/truck*`, or issues and discussions about kernel
+and the kernel operations still in this repository are migrating there. The split:
-work: booleans, fillets, chamfers, shell, offsets, sweeps and lofts, threads and holes, STEP/IGES
+
-import and export, or tessellation. The pinned issue on the tracker explains it. New ones get the
+- **SolidCraft** is the application: commands, the timeline, sketches, the UI, file handling. A new
-`kernel-paused` label (`.github/workflows/kernel-paused.yml`) and a maintainer answers them. Crashes
+  feature calls the solidcore API and builds on the operations it offers.
-and data loss are still taken as issues. Pull requests outside those directories carry on as normal,
+- **solidcore** holds the geometry: evaluators, intersections, booleans, blends, shells, sweeps,
-including the dialogs and tools for these features.
+  tessellation and the rest of the math. If a feature needs kernel functionality solidcore does not
+  have yet, add it to solidcore first (its own issue and PR), then use it here.
+
+So pull requests that add geometry math to SolidCraft (`crates/kernel/`, `crates/geom/`, or a new
+evaluator or solver anywhere else) are not taken; they get the `kernel-paused` label
+(`.github/workflows/kernel-paused.yml`) and a maintainer points them to solidcore. Crashes and data
+loss are still taken as issues here, and the dialogs and tools for kernel features carry on as
+normal.
+
+Work started before 0.40 was written against the earlier kernel. It is still welcome: port it onto
+today's code, calling solidcore for the geometry, before it can land. Expect a substantial rework
+for anything that touched the kernel. Designs keep opening and rebuilding on the new kernel; where a
+result changes, the PR says so and why.
 
 ## Get it running (about 10 minutes on a fast machine)
 
@@ -329,8 +341,11 @@ and a fresh CI run:
 
 1. Work is tracked in [GitHub issues](https://github.com/tangency-labs/solidcraft/issues), labelled
    by area (`area:kernel`, `area:sketch`, `area:doc`, `area:ui`, `area:infra`). For anything
-   bigger than a bug fix that has no issue yet, open one first. **Claim the issue with a draft
+   bigger than a bug fix that has no issue yet, discuss it on [Discord](https://discord.gg/FtU4NQNVDH)
-   PR** before you start, so two people don't build the same thing:
+   first, then open an issue. Before you start, search **all** issues and pull requests, open and
+   closed, for similar work (`gh issue list -R tangency-labs/solidcraft --state all --search "<words>"`,
+   and the same with `gh pr list`). **Claim the issue with a draft PR** before you start, so two
+   people don't build the same thing:
    - Check nobody has it: `gh pr list -R tangency-labs/solidcraft --state open --search "#N"`.
    - Branch from the latest `main`, commit `git commit --allow-empty -m "claim: #N"`, push, and
      open a **draft** PR titled `<summary> (#N)`, e.g. `Fillet: variable radius along a chain (#123)`.
@@ -443,7 +458,7 @@ correct them freely and it won't put them back.
 
 ## Where help is wanted most
 
-**Kernel speed (slow fillets, booleans, STEP):** please don't rewrite the current kernel code for speed; it is being replaced by [solidcore](https://github.com/bherbruck/solidcore) ([progress](https://tangency-labs.github.io/solidcore/)). Report slow cases with a file under the `kernel-perf` label, and put kernel effort into solidcore instead. See [#1597](https://github.com/tangency-labs/solidcraft/issues/1597).
+**Kernel speed (slow fillets, booleans, STEP):** please don't rewrite the current kernel code for speed; the kernel is [solidcore](https://github.com/tangency-labs/solidcore) ([progress](https://tangency-labs.github.io/solidcore/)). Report slow cases with a file under the `kernel-perf` label, and put kernel effort into solidcore instead. See [#1597](https://github.com/tangency-labs/solidcraft/issues/1597).
 
 See the [`help wanted`](https://github.com/tangency-labs/solidcraft/labels/help%20wanted) and
 [`good first issue`](https://github.com/tangency-labs/solidcraft/labels/good%20first%20issue) labels.

skills/solidcraft-contributing/SKILL.md

@@ -19,6 +19,7 @@ not modelling a part through MCP.
   feature under another number, and PRs that change the files you will change
   (`gh pr list ... --json number,title,files`). If someone has it, comment on their PR or issue
   instead of opening a second one: two PRs for one change cannot both land.
+- **Search before you start.** Scan ALL issues and PRs, open and closed, for similar work (`gh issue list` and `gh pr list --state all --search`). New features are discussed on Discord, then get an issue. Kernel functionality goes to solidcore, not here (CONTRIBUTING.md, "Kernel work goes to solidcore"); work begun before 0.40 is ported onto today's code first.
 - **Claim with a draft PR.** `gh pr list -R tangency-labs/solidcraft --state open --search "#N"`; if none,
   branch from the latest `origin/main`, `git commit --allow-empty -m "claim: #N"`, push, and open a
   draft PR titled `<summary> (#N)`. The lowest-numbered open PR for an issue wins; close yours if it