Stage287: Contract Compatibility for QSP Product Contracts

Overview

Stage287 introduces contract compatibility verification for QSP product contracts.

Stage286 defined the product contract. Stage287 proves that the contract can evolve without breaking verification.

This stage adds a version-aware compatibility policy and a deterministic compatibility report.

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Why This Stage Matters

A product gains long-term value not only by being verifiable, but by remaining verifiable across versions.

Stage287 establishes:

• explicit compatibility policy
• backward-compatible verification semantics
• stable core contract expectations
• version-aware checks for future evolution

This matters for:

• SaaS deployment
• standardization
• OpenSSF-style review
• long-lived public verification systems

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Core Idea

A product contract should remain compatible as the system evolves.

Stage287 verifies whether a contract still preserves:

• known version identity
• required core layers
• stable decision semantics
• explicit fail-closed meaning
• derivable public verification status

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What This Stage Adds

This stage adds:

• spec/compatibility_policy.json
• schemas/qsp_product_contract_v1.schema.json
• schemas/qsp_product_contract_compatibility.schema.json
• tools/check_stage287_compatibility.py
• tools/verify_stage287_compatibility.py
• out/compatibility/compatibility_report.json

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Repository Structure

spec/
  compatibility_policy.json
  qsp_product_spec.json

schemas/
  qsp_product_contract.schema.json
  qsp_product_contract_v1.schema.json
  qsp_product_contract_compatibility.schema.json

tools/
  build_stage286_product_contract.py
  verify_stage286_product_contract.py
  check_stage287_compatibility.py
  verify_stage287_compatibility.py

out/product/
  qsp_product_contract.json
  qsp_product_contract.json.sha256

out/compatibility/
  compatibility_report.json
Build Product Contract
python3 tools/build_stage286_product_contract.py
Check Compatibility
python3 tools/check_stage287_compatibility.py
Verify Compatibility
python3 tools/verify_stage287_compatibility.py
Expected Result

A successful run produces:

a compatibility report
explicit version binding
compatibility status = true
five policy checks passed
What This Stage Proves
product contract versions can be checked explicitly
backward-compatible semantics can be defined as policy
future versions can evolve without silently breaking verification
later public verification systems can depend on a stable compatibility layer
Conceptual Transition

Stage286:

Define the product contract

Stage287:

Prove the contract can evolve without breaking verification

Significance

This stage moves the project from:

a defined product contract

to:

a version-stable product contract

That is a major step toward:

durable verification
product reliability
future-proof interfaces
public-facing verification services
Future Directions
compatibility adapters for future major versions
negotiation between contract versions
compatibility-aware verification URLs
remote public contract validation
policy-aware multi-version verification services
License

MIT License
Copyright (c) 2025