RFC: Pact MkII — a ground-up redesign of the Pact framework - #146
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RFC: Pact MkII — a ground-up redesign of the Pact framework#146rholshausen wants to merge 2 commits into
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Proposes a single-engine architecture with thin generated SDKs, declarative interactions compiled to inspectable matching plans, components/plugins as the core design, a shape language with variant testing for optional and polymorphic values, provider shapes with a subsumption check, and scriptable lifecycle hooks. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
rholshausen
marked this pull request as ready for review
July 30, 2026 06:13
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good read, will take some time to mull over. sounds really promising |
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Even Claude agrees: |
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This RFC is a thought experiment made concrete: if we designed Pact from scratch today, what would we keep, change, and throw away? It proposes Pact MkII (working title), built on five pillars:
pact explain), building on the v2 matching engine prototyped in pact-reference.optional,oneOf,anyOfand cardinality, made safe by variant testing (every declared variation is actually exercised and replayed), plus provider-published shapes with a subsumption check to catch response variance the consumer never declared.The consumer-driven workflow, the pact file as artifact, and the broker/
can-i-deployworkflow are all retained. v1–v4 pact files remain verifiable and apact upgradetool is proposed. Deterministic verification remains the foundation; AI assistance (SDK maintenance, mismatch diagnosis, agentic orchestration) is strictly optional.Backwards compatibility is explicitly not a constraint for this exercise, though a migration path is sketched. Feedback is welcome on any part, but the unresolved questions section lists the areas where community input would help most: naming/versioning, the day-one scope of the component model, variant sampling defaults, and subsumption policy.
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