[thekevinbot]

Fixes #1074. Part of #1072.

The published-target table existed twice — a TypeScript literal in
packages/ts/src/platforms.ts and a hand-maintained Python subset in
internals/distcheck/.../node_flow/platforms.py — and a third component,
internals/checks/src/checks/platforms_mirror/, existed only to parse both and
prove they agreed. This collapses the duplicate and deletes the check.

The direction, and why

Canonical artifact: packages/ts/src/platforms.json. The rows move there
verbatim. platforms.ts imports it and types it; the distcheck flow reads the
same file with json.loads. Nothing is generated, nothing is committed twice,
and there is no derivation step to drift — the file is the table.

Three constraints picked that location, and each ruled out an alternative:

• It has to ship to npm. loadNativeCore() calls libTriples() at runtime
  in the published package, so the data cannot live at the repo root or in
  putitoutthere.toml — neither is inside packages/ts, and npm files cannot
  reach a parent directory. Under src/ with resolveJsonModule, tsc copies
  the JSON into dist/ next to the compiled modules, and files: ["dist/", …]
  ships it. Verified, not assumed — see the manual run below.
• It has to be read, not generated. A generated file that is committed can
  drift, which would need a check to police it — the exact thing being deleted
  here. A generated file that is not committed has to exist before any
  consumer builds, including tsx tools/stage-platform.ts and a Python process
  that never runs tsc. Reading one declarative file sidesteps both.
• The subset stays a subset. The JSON carries every field; each reader takes
  what it needs. triple and libc remain TypeScript-only, as before.

Types at the boundary. JSON widens nodePlatform / nodeArch to string,
so PLATFORMS is a single as readonly Platform[] cast — one cast, in the one
place the JSON and node vocabularies meet. The Platform interface is
unchanged. On the Python side the only derivation is slug, stripped from
libName; existing assertions (p.slug, p.name, p.addon_name) pin it.

Public surface

Unaffected. packages/ts/src/index.ts exports only DirSQL and Table,
and package.json's exports map has a single "." entry — PLATFORMS,
libTriples() and librarySlug() were never reachable by a consumer and still
are not. librarySlug keeps its home in library-slug.ts and its behavior.
No SDK public API moved, so PARITY.md needs no update.

The one packaging-visible change: dist/platforms.json is now in the tarball
alongside the .js/.d.ts files.

Deleted

• internals/checks/src/checks/platforms_mirror/ — 24 files (12 source, 12
  colocated tests), including everything refactor(checks): one function per file across attestation_guard and platforms_mirror #1102 split out of it.
• internals/checks/tests/integration/platforms_mirror_test.py and
  internals/checks/tests/e2e/platforms_mirror_test.py.
• Its import + add_command line in checks/cli.py, and the
  test_platforms_mirror_is_registered case in cli_test.py.
• .github/workflows/platforms-mirror-check.yml.

Added in its place: packages/ts/src/platforms.json on
internals-distcheck-ci.yml's path filter, so a table edit still triggers the
lane whose lookup reads it.

Source-line delta

Measured with #1072's srcline.py (non-test, non-comment, non-blank), base
3a1e427 vs this branch. JSON is data, not source, and is outside the metric —
as are the Python and TypeScript comments.

scan root	before	after	delta
packages/ts/src	544	502	−42
internals/checks/src	1,613	1,310	−303
internals/distcheck/src	354	361	+7
total (all 8 roots)	10,557	10,219	−338

24 fewer files. The issue estimated ~−276; the extra comes from platforms_mirror
having grown under #1020's extraction rungs since that estimate was taken.

Red/green

This is a refactor plus a removal, so neither arm of the rule demands a pushed
RED. The removal is exempt by AGENTS.md. The refactor introduces no new
observable behavior: PLATFORMS holds byte-identical rows, libTriples()
returns the same map, and the Python Platform tuple is unchanged — all of it
already pinned by packages/ts/src/platforms.test.ts and
internals/distcheck/.../platforms_test.py, which are untouched. Not one
test assertion changed anywhere in this PR. Every deleted test is a test of
deleted source.

Added assertions (not changed ones)

The colocated-test co-change gate requires a changed source file's test to
change with it, so each side gained one new case — a strengthening, never a
rewrite, and aimed at exactly the risk this PR introduces:

• platforms.test.ts pins every ${nodePlatform}-${nodeArch} key. PLATFORMS
  is a cast, so no type stops a hand-edited row carrying a value node never
  reports.
• platforms_test.py pins the full slug set. slug is the one field the
  Python side derives rather than carries, and a moved constant is a mutation
  survivor without a test on its literal.

Notes

• tools/stage-platform.ts's "unsupported host" message pointed at
  src/platforms.ts; it now points at src/platforms.json. Not asserted by any
  test (stage-platform.test.ts matches /unsupported host/ only).
• arch.py's "extend platforms.py" message was already pointing at the wrong
  file before this PR (the arch map lives in arch.py). Left alone — unrelated,
  and its own one-line fix.
• one_function_per_file at threshold 1: internals/checks/src,
  packages/ts/src and internals/distcheck/src all still report zero
  violations. Measured with npx -y testing-conventions@latest, resolved
  version 0.0.116.

Manual verification

$ npx tsc -p tsconfig.build.json          # resolveJsonModule on
$ ls dist/platforms.json                  # → emitted, 1.0K
$ node -e "import('./dist/platforms.js')" # libTriples() → the same 5-entry map as main
$ npm pack --dry-run                      # "1.1kB dist/platforms.json" in the tarball
$ cd /tmp/demo && node .../dist/cli/dirsql.js "select * from './'"
[{"basename":"a.txt","ctime":…,"dir":"","ext":"txt","mtime":…,"path":"a.txt","size":6}]
$ uv run --project internals/distcheck python -c "from distcheck.node_flow.platforms import PLATFORMS; ..."
linux-x64-gnu   @dirsql/lib-linux-x64-gnu   dirsql.linux-x64-gnu.node   ['linux'] ['x64']
linux-arm64-gnu @dirsql/lib-linux-arm64-gnu dirsql.linux-arm64-gnu.node ['linux'] ['arm64']
darwin-x64      @dirsql/lib-darwin-x64      dirsql.darwin-x64.node      ['darwin'] ['x64']
darwin-arm64    @dirsql/lib-darwin-arm64    dirsql.darwin-arm64.node    ['darwin'] ['arm64']
win32-x64-msvc  @dirsql/lib-win32-x64-msvc  dirsql.win32-x64-msvc.node  ['win32'] ['x64']

Identical to the table on main, field for field.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: N/A — packages/python untouched
• TypeScript SDK e2e: pass (5 files, 16 tests)
• Rust core e2e (if applicable): N/A — packages/rust untouched
• packages/python/e2e-attestations/<branch>.json receipt written if packages/python changed (just e2e-attest-python) — N/A, unchanged
• packages/ts/e2e-attestations/<branch>.json receipt written if packages/ts changed (just e2e-attest-ts)
• internals/checks/e2e-attestations/<branch>.json receipt written (internals/checks/src changed)
• Command(s) run:
  • pnpm test:e2e in packages/ts → 5 files, 16 tests, all pass
  • uv run python -m pytest tests/e2e -x -q in internals/checks → 25 pass
  • uvx testing-conventions@latest e2e attest '<above>' in each, receipts committed
  • just preflight → all pairs green (3 packaging SKIPs, which need a built artifact)
• Result summary: green. Both receipts are pure additions — git show --stat on each
  attestation commit shows one file, 7 insertions, no sibling receipt pruned.

Changelog / Migrations

• Changelog fragment added under <root>/<pkg>/changelog.d/ for each changed package — packages/ts/changelog.d/2026-09-05-platform-table-single-source.md. internals/** is outside changelog_gate's _ROOTS.
• Migration fragment added under <root>/<pkg>/migrations.d/ (or: not required — additive/bugfix only) — not required: no public API breaks, no deprecated symbol removed, and no runtime behavior change. PLATFORMS and libTriples() return exactly what they returned before.