Epic: cobolrt as a product — a COBOL runtime for Java that carries its own evidence #4710

Goal. Make cobolrt, the Java runtime that gives translated code COBOL's exact behaviour, a distinctive product. It's faithful to IBM z/OS under each estate's options, it carries its own evidence, it produces maintainable Java, and it offers customers an exit route instead of lock-in.

Why. Translation fidelity is almost entirely the runtime's job: nearly every correctness bug fixed on 2026-10-07/08 was a runtime rule. Competitors ship proprietary runtimes that customers must trust and license forever. Ours can be provable, customer-owned and option-aware.

Principles.

• IBM is the reference; GnuCOBOL is the instrument (oracle policy: IBM is the reference, GnuCOBOL the instrument — audit register entries + z/OS calibration oracle #4702).
• Options are a first-class input (compile & runtime options as a first-class estate input: one resolver for oracle + det port, provenance, evidence fingerprint #4704).
• Fail loudly, never silently.

Issues

• cobolrt: rule catalogue — an ID, IBM reference, option dependencies and register status for every runtime rule #4711 rule catalogue: an ID, IBM reference, options and register status per rule
• cobolrt: rules as data — generate runtime code, test vectors and docs from rule tables (start with one family) #4712 rules as data: generate code, vectors and docs (first family)
• evidence report: list the runtime rules each program exercises, with their calibration status #4713 evidence report: the rules each program exercises, with calibration status
• cobolrt: take an explicit per-estate options profile instead of baked-in behaviour #4714 per-estate options profile in the runtime (builds on compile & runtime options as a first-class estate input: one resolver for oracle + det port, provenance, evidence fingerprint #4704)
• det translator: more readable Java — extend provably-safe lifting from bytes to plain Java types #4715 more readable Java: provably-safe lifting
• cobolrt exit route: record which COBOL quirks fire in production so customers can safely simplify the Java #4716 exit route: production quirk telemetry, then a simplification report
• cobolrt performance: benchmark vs COBOL batch volumes, then add proven fast paths #4717 performance benchmark plus proven fast paths
• cobolrt as a shippable product: stable API, versioning, licence, documentation #4718 runtime as a shippable product: API, versioning, licence, docs, fail-loudly audit

Related.

• oracle policy: IBM is the reference, GnuCOBOL the instrument — audit register entries + z/OS calibration oracle #4702: IBM reference and z/OS calibration.
• compile & runtime options as a first-class estate input: one resolver for oracle + det port, provenance, evidence fingerprint #4704: compile and runtime options.
• Evidence report: purchaser-facing levels and numbers per program and estate (no binary "proven") #4601 / evidence report: regenerate on main by bot, advisory in PRs, strict at release (stop per-PR report churn) #4703: evidence report.
• Evidence L5: mutation testing on det ports, survivors accounted for (#4601) #4628: det-port mutation (L5).

Suggested order. 4711 → 4712 (with #4702 calibration) → 4713 and 4714 → 4717 → 4715 / 4716 → 4718 (the licence question runs in parallel with counsel).

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