TypeScript-first source policy

Kontour product and runtime source defaults to TypeScript across Flow, Flow Agents, Surface, Veritas, and kontourai.io. New durable product code, runtime adapters, package APIs, CLI behavior, workflow orchestration, hooks, provider bridges, and shared contracts are authored in TypeScript by default in repositories that are TypeScript-enabled or migrating toward TypeScript.

Decision

• TypeScript-enabled repositories expose a typecheck or build validation that proves the authored TypeScript surface compiles, and CI runs that validation before code is treated as releasable.
• Narrow JavaScript/MJS/CJS exceptions remain acceptable: package/tool configuration that expects JS/MJS, generated docs/site assets, thin shell-adjacent launchers, fixtures/examples/tests following existing local convention, and historical archived/vendored/generated artifacts that are not edited as active source. Exceptions stay narrow — expanding product/runtime behavior in JS/MJS is a deliberate exception or routed into a migration plan.
• Repositories with nontrivial non-TypeScript runtime source track staged migration through repo-specific issues rather than being grandfathered as permanent direction (see the original inventory and linked migration issues in the frozen ADR below).

Rationale

Cross-repo shared source, contracts, adapters, and workflow tooling need a consistent default language, or new work deepens fragmentation and turns every existing non-TypeScript file into an implicit permanent exception. This is a purely technical, already-settled call: the frozen ADR below made the decision on 2026-05-31 and it has not changed. This entry upgrades the ADR-freeze cutover’s needs-decision stub for this subject (issue #314) to a living decision — nothing new is decided here beyond recording that the frozen ADR’s call still stands, per the Probe docs-write contract’s worked example (context/contracts/probe-docs-write-contract.md).