# C17 — Authoring surface

**Guarantee.** All *logic* — nodes, strategies, **and experiments/harnesses** —
is authored in native Rust through **Claude Code + the skills pipeline**: the
human describes, Claude writes the Rust, builds it, runs it via the `aura` CLI,
and reports metrics. This binds **computation** — a node's math, a
meta-program's control flow — to native Rust (the RustAst lesson, sharpened: a
small LLM cannot reliably *apply* a computational DSL, and a strong one does not
need one). It does **not** bind **topology** — which node feeds which, the
structural axes, the param-space — to Rust *source*: topology is a
**serializable data value** the World owns (C24), a non-Turing static DAG over
the closed, compiled-in node vocabulary (C8/C16) that carries no computation
(#109, resolved 2026-06-29). The no-DSL guard therefore forbids a
*computational* experiment / strategy language, not a static topology-data
format — the experiment-matrix *generator* may stay Rust (C20); its *output* is
topology-data. Declarative config (`Aura.toml`) carries only **static project
context** (paths only: data archive root, runs dir), never logic. aura ships
**no embedded coding-LLM**; IONOS LLMs are used only as a *runtime data source*
(news-agent bias, C11), gated by per-session consent, never in the code path.

**Forbids.** An in-app LLM chat that generates node code inside aura; using
IONOS (weaker models) as the authoring brain; a *computational* experiment /
strategy DSL the author must apply (the RustAst trap) — distinct from a static
topology-data format, which is permitted.

**Why.** LLMs author Rust well in Claude Code — that is the fix to RustAst's
failure; making weaker models the coding brain reintroduces the very problem.
Keeps aura's scope an engine + playground, not an LLM-IDE. Topology-as-data is
*not* the RustAst trap re-opened: that trap is a DSL the author must *apply*; a
topology-data blueprint is machine-generated / owned and applied by no one, so
the no-DSL guard stands unbroken — a *closed-vocabulary* data artifact is not
the forbidden *open, logic-bearing* language (C25).

## Current state

The authoring loop is the skills pipeline over native Rust: node / strategy /
harness logic compiles into the closed node vocabulary, and the `aura` CLI runs
it. Topology-as-data is realized as **blueprints** — a data-only project's
`blueprints/*.json` are serialized static DAGs over the std vocabulary (the
`aura new` scaffold writes a starter `blueprints/signal.json`;
`crates/aura-cli/src/scaffold.rs`); the blueprint data format itself is C24's
contract. `Aura.toml` carries paths-only project context (C16). The IONOS
runtime-source path (news-agent bias) is the only external-LLM use — C11's
record-then-replay edge, consent-gated, never in the sim code path.

## See also
- [C8](c08-node-contract.md) — the closed, compiled-in node vocabulary topology draws on
- [C11](c11-sources-record-replay.md) — IONOS news bias as a recorded runtime source
- [C16](c16-engine-project-split.md) — the engine/project split and `Aura.toml` project context
- [C20](c20-strategy-harness.md) — the experiment-matrix generator that stays Rust
- [C24](c24-blueprint-data.md) — the topology / blueprint data format the World owns
- [C25](c25-role-model.md) — a closed-vocabulary artifact vs the forbidden open DSL