feat: add requestTransform for deterministic matching and recording

[jpr5]

Summary

From #63. Full credit to @iskhakovt, this is just me taking on the rebase/re-do work from the large 1.7.0 PR that just merged.

Adds requestTransform to MockServerOptions — a function that normalizes requests before both matching and recording, solving the problem of dynamic data (timestamps, UUIDs, session IDs) causing fixture mismatches on replay.

const mock = new LLMock({
  requestTransform: (req) => ({
    ...req,
    messages: req.messages.map(m => ({
      ...m,
      content: typeof m.content === "string"
        ? m.content.replace(/\d{4}-\d{2}-\d{2}T[\d:.+Z]+/g, "")
        : m.content,
    })),
  }),
});

Recording: saves the transformed match key — no timestamps in fixture.
Matching: transforms incoming request before comparison — same clean key.

When requestTransform is set, string matching switches from includes (substring) to === (exact equality). Without a transform, existing includes behavior is preserved (backward compatible).

Changes

• types.ts: Add requestTransform to MockServerOptions and HandlerDefaults
• router.ts: Optional 4th param on matchFixture, exact match when transform set
• server.ts: Thread transform into defaults
• recorder.ts: Apply transform before match key extraction
• All 15 provider handlers: Pass defaults.requestTransform to matchFixture
• docs/record-replay.html: Document the feature with use case and example
• 16 new tests covering basic transform, exact vs includes, backward compat, embeddings, predicates, streaming, tool calls

Attribution

Based on the design by @iskhakovt in #63, rebuilt cleanly on the 1.7.0 codebase. The original PR had 100 commits and was conflicting after the v1.7.0 rebrand — this is a fresh implementation of the same concept.

Test plan

• npx vitest run — 2064 tests pass (58 files)
• npx tsc --noEmit — clean
• Backward compatible — no transform = existing includes behavior unchanged

[pkg-pr-new]

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npm i https://pkg.pr.new/CopilotKit/aimock/@copilotkit/aimock@79

commit: aafe82a

[jpr5]

Full credit to @iskhakovt, this is just his work rebuilt on top of the new release of aimock.