Syntax, idioms and conventions for writing .grob programs — sample scripts, integration-test fixtures, error examples. Use this skill whenever you create or edit a .grob file, so the language source is idiomatic and valid against the v1 surface. Covers bindings, the three string forms, nullability, control flow, lambdas, collection pipelines, structs, errors, the stdlib surface and numerics.
The single authoritative procedure for allocating a Grob error code — the pre-declared-budget model with an allocate-and-surface fallback for the unanticipated case. Use whenever an increment needs a diagnostic code: to confirm the budget covers it, to make the fold-into-existing versus register-new judgement, or to register a new code in lockstep. Codes are immutable once shipped (ADR-0017), so this keeps the design judgement explicit while making the mechanics deterministic. writing-an-error-test defers to this skill for the code itself.
Use when an increment introduces, resolves or constructs a Grob type — a `type` declaration, a struct construction, an anonymous struct, a new type-annotation position, a new built-in type, or any feature where a value carries a type the checker must resolve and the VM must represent. Encodes the four failure modes that produced the Sprint 5 post-close interludes (type-reference-grammar gaps, conflated cycle walks, non-uniform redeclaration and lifecycle objects escaping through new containers) as a standing pre-flight and a closing checklist. Reuses, does not replace, `adding-an-opcode` and `tdd-cycle`.
The sanctioned procedure for adding a parser production or an AST node to Grob — the parser/AST analogue of adding-an-opcode. Use when an increment genuinely needs a new surface form or a new node that is not already there (a new construction expression, a new literal, a new annotation position). The front end is built incrementally, so this is a real and expected job — not a wall to route around with an improvised gap-fix. It is deliberate and reviewable, never silent.
How to add or update a gold-master error-example pair (_grob.txt + _expected.txt) and register the error code, without breaking the negative-test release gate.
Use during a manual PR review to pull SonarQube Cloud (SonarCloud) findings for the pull request straight from the Web API — issues on new code, the quality-gate verdict and the new-code coverage against the floor — without the Docker-based Sonar MCP server. Produces a compact findings block for the reviewer to fold into its PR comment. It does not post anything; the human composes and posts the comment. Assumes the PR's Sonar scan has already completed (the reviewer is triggered manually after all scans).
The procedure for compiling and executing closures in Grob — the four-category variable resolution, upvalue capture of enclosing-function locals, the open/closed upvalue lifecycle, the close-on-return hand-off and per-call capture independence. Use when implementing or reviewing lambda capture (Sprint 5 Increment D), not for top-level-only lambdas.
The strict red/green/refactor TDD procedure for Grob, with xUnit specifics. Use when starting a new test, when about to write production code, when finishing a cycle or when uncertain whether you should be writing a test or implementation next.