OpenTUI Agent Guide

Engineering

• Reuse existing seams; do not duplicate policy, ownership, or state across TypeScript, Zig, and framework layers.
• For bug fixes, first add a focused regression test of observable behavior or invariants. If automation is impossible, record the evidence and remaining manual verification; do not substitute contract sketches or guesses.
• Make native ownership explicit; clean up handles, callbacks, buffers, and listeners on every exit path. Bound input-driven work and test lifecycle failures.
• Do not interchange byte lengths, code points, graphemes, and terminal display-cell widths.
• oxfmt is the formatting source of truth (semi: false, printWidth: 120); avoid unrelated formatting churn.
• In delegated tasks, name the local rendering behavior, owned files, and required checks. Describe ordinary renderer work as correctness and compatibility testing; reserve security terminology for actual security work. Use concrete scopes such as frame parity, callback ordering, resource cleanup, or loopback SSH output tests. Request an independent correctness review and a separate reproduction check of actionable findings.

Tooling And Runtimes

• Use Bun for dependency management and development commands: bun install, bun run <script>, bun test, and bun <file>.
• Run package scripts from the package directory unless the script is defined at the repository root.
• Shared runtime code must preserve the supported Bun and Node paths. Keep runtime-specific behavior behind existing platform/runtime/build seams; do not introduce Bun-only APIs into shared modules. Node checks use the minimum version enforced by scripts/node26.mjs.

Verification

• Run the narrowest relevant test first, then the affected package suite.
• Ordinary TypeScript source changes do not require the root build. Use the affected package's test, typecheck, build, or validation scripts as applicable.
• Run bun run build from the repository root after native or cross-package build/output changes, or when tests report a missing/stale native artifact. It does not build web or examples; use their package scripts.
• For native changes, run bun run test:native from packages/core. Filter with bun run test:native -Dtest-filter="test name" while iterating.
• For runtime, FFI, build, or export changes, run the relevant Node and packed-distribution scripts from that package (such as test:js:node or test:dist) when present.
• Use root bun run fmt:check and bun run lint for final static checks when relevant.

Prefer tests and TestRenderer for automated debugging. For interactive behavior, load the terminal-control skill and use its terminal tool to run, drive, and inspect the app; repository examples bind backtick to renderer.console.toggle() for captured console.log output. Ask for a user-run reproduction only when the required terminal or platform is unavailable locally.

Portable FFI

• Portable symbol signatures must stay within the node:ffi/bun:ffi intersection. Use explicit widths such as u32/u64, not backend-only ABI names such as usize, napi_env, or napi_value; represent i64/u64 as bigint, native booleans as 0/1, and shared pointers as number | bigint.
• Default to buffer for transient, non-null TypedArray parameters and pass the view directly. Do not call ptr().
• For a raw ArrayBuffer, create one Uint8Array view over it, keep that view, and declare buffer. A buffer call costs less than a ptr call. buffer rejects an argument that is not a view with a TypeError. ptr sends a bad argument to native code as an address.
• Use ptr only when a parameter can be null, accepts a numeric native address, or is a callback. Pass transient owner objects directly to ptr parameters. Do not pre-resolve them.
• Bun 1.3 does not accept DataView directly for buffer or ptr parameters. Pass an equivalent typed array such as new Uint8Array(view.buffer, view.byteOffset, view.byteLength).
• On Bun 1.4+, use buffer when you pass a DataView directly to FFI.
• Use ptr(view) only when native code stores the address beyond the call. Before resolving it, access view.buffer to move any inline typed-array storage into a stable ArrayBuffer, then keep the view alive for the complete native lifetime. The order is required: const owner = view.buffer; const address = ptr(view). Calling ptr(view) first and accessing view.buffer later can move the storage and invalidate address.
• Model C-string inputs as pointer parameters and pass owned, NUL-terminated byte buffers directly; string returns are not portable. Create callbacks through the loaded library/platform facade, not new JSCallback(...), and assume only same-thread callbacks.