[lucasbraum]

What and why

1. Shared root through a setup or declaration file. In the vitest pack test (#57, ground truth votingworks/vxsuite), check reported a breaking finding at libs/image-utils/src/jest_pdf_snapshot.ts:42 (TS2551, toMatchImageSnapshot missing on Assertion) beside the declaration at libs/image-utils/src/vitest_setup.ts:10 the pack already reports. The tracer did not link them: #51 handles parameters only, and this is a global augmentation. Two things turned out to be true on inspection:

• The failing member is not a parameter and not declared in the setup file either: toMatchImageSnapshot comes from jest-image-snapshot's own types, which declare it on the global jest.Matchers. The setup file augments that same interface (declare global { namespace jest { interface Matchers<R> { toMatchImage…; toMatchPdfSnapshot… } } }) and registers all three matchers with expect.extend. Vitest 5 stops reading the global namespace, so every matcher on it has to move to Matchers<R, T> of "vitest" together, and the repository's augmentation is where that edit goes.

The cause tracer (adapters/typescript/cause.ts, augmentationCause) now handles missing-member diagnostics (TS2339, TS2551): the member is resolved in the baseline program, where it still exists, and

• when its declaration is in a repository file, the diagnostic is anchored there: a declare global block at the block, a declare module "x" augmentation at the interface inside it, any other repository declaration at itself;
• when its declaration is a package's (or another fixture's) on an interface the repository augments, it is anchored at the repository's augmentation of that interface, this workspace's first, with the package named in the reason;
• one site is enough, unlike a parameter: the edit is never at the call. The anchor is also the diagnostic's root, so sites in other workspaces fold with it after the merge (feat(check): one finding when call sites in several workspaces trace to one declaration #51's model, same report fields: anchorOnly, downstream, root, "N call sites").

It is tried after the compiler-option cause and before the parameter cause. On vxsuite the finding is now one site at vitest_setup.ts:10, with the jest_pdf_snapshot.ts call as evidence.

2. README line limit. readme.test.ts capped the file at 150 lines and every pack row pushed against it. The test now excludes the generated block between <!-- packs:start --> and <!-- packs:end --> from the count. #57's two joined documentation lines are not on main (that change lives on #57's branch), so there is nothing to restore here; once this merges, #57 can drop that edit.

No pack's rules, expectations or ground truth were edited.

How it was verified

Unit tests in cause.test.ts on a new fixture pair, fixtures/deps/matchers-v1 (an assertion that reads the global checks.Matchers) and matchers-v2 (its own Matchers<R, T>, the global no longer read), plus matchers-extra-v1 (a package declaring a matcher on that global):

• three call sites in two files, for a matcher the setup file declares, fold into one anchor at the setup file's declare global line, each site carrying the cause and the root;
• a call site for a matcher another package declares on the interface the setup file augments anchors at that augmentation, naming the package;
• a member the package itself dropped is left at the site.

pnpm lint, pnpm typecheck, pnpm docs:links, pnpm docs:packs --check, the private-material guard, core (930 tests) and CLI (350 tests) pass.

Pack tests, before (main at 45677eb) and after (this branch), breaking findings; vitest run in a scratch worktree with #57's pack copied in uncommitted:

pack	before: precision / recall, breaking FP	after: precision / recall, breaking FP
vitest (#57, candidate)	94% / 50%, 1 (jest_pdf_snapshot.ts:42)	100% / 50%, 0
zod	100% / 71%, 0	100% / 71%, 0, identical
stripe	100% / 90%, 0	100% / 90%, 0, identical
ai	100% / 36%, 0	100% / 36%, 0, identical
react	100% / 69%, 0	100% / 69%, 0, identical

vitest per rule after: matcher-types 100% / 100% (3 of 3), was 75% / 100%. pack test vitest still exits non-zero on this branch only because #57's verification.json records 94% / 1 false positive and no longer matches; that file is #57's to rewrite with --write. Its 16 false negatives and the 18,900-odd generic (unverified) sites (not breaking) are unchanged.

Checklist

• Tests for the change (a bug fix starts with a failing test)
• pnpm lint && pnpm typecheck && pnpm test pass
• README and docs updated if behavior changed (docs/architecture.md, docs/concepts.md)
• Changeset added if a user would notice (pnpm changeset): minor
• No new dependency, or it was agreed in an issue
• No private code, names or paths in fixtures, tests or docs
• The rules in CONTRIBUTING.md ("Rules that do not bend") still hold

🤖 Generated with Claude Code

https://claude.ai/code/session_018u9b3Pp5H68DdYZGp5Qg1U

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