Constant HELM_CHART_KEY_API_VERSION 

pub const HELM_CHART_KEY_API_VERSION: &str = "apiVersion";

Canonical Helm 3 Chart.yaml top-level YAML axis-key naming the per-chart chart-schema-apiVersion field whose scalar-value HELM_CHART_API_VERSION already owns as the peer axis-value lift. Where the peer axis-value lift pins the byte-shape of the apiVersion: field’s admitted scalar (Helm 3’s "v2"), this axis-key lift pins the byte-shape of the apiVersion: field’s YAML-key name itself: the load-bearing serde-rename literal at caixa-helm’s ChartYaml struct (caixa-helm/src/lib.rs:145, #[serde(rename = "apiVersion")]) that selects how the Rust field api_version serializes into the rendered Chart.yaml YAML mapping.

The byte-shape ("apiVersion") is byte-identical to the K8s-CR top-level per-CR schema-apiVersion axis key (KUBE_KEY_API_VERSION) by Helm’s design decision to inherit the K8s CR top-level shape verbatim (see chart-yaml-desc) — the paired helm_chart_key_api_version_matches_kube_key_api_version pin asserts the two byte-shapes coincide, so a future K8s-side rebrand at KUBE_KEY_API_VERSION that dropped the byte- identity would fail the pin, surfacing the axis divergence at substrate-build time rather than as a silent Helm-chart-schema- parser rejection at helm lint / helm template time. The two axes are structurally-independent schema surfaces (the Helm 3 chart-schema top-level shape vs. the K8s apiserver-side CR top-level shape) whose byte-shapes happen to coincide today; the paired pin makes the coincidence load-bearing rather than accidental.

The single source of truth every consumer that names the per- Chart.yaml top-level chart-schema-apiVersion YAML key reaches for:

• caixa-helm’s ChartYaml struct’s api_version field #[serde(rename = "apiVersion")] attribute (the sole production serialize-side site the literal appears at as a syntactic serde-rename argument; the attribute itself cannot consume a const because Rust’s attribute grammar admits only string literals, so the discipline here is: the const’s byte-shape must remain byte-identical to the literal the attribute pins, and the paired drift-detection pin at [caixa-helm]’s chart_yaml_serializes_api_version_axis_under_lifted_helm_chart_key_api_version round-trips a rendered [caixa-helm]-emitted Chart.yaml through serde_yaml::from_str::<serde_yaml::Value> and asserts the top-level Mapping::get(HELM_CHART_KEY_API_VERSION) resolves — closing the drift the syntactic-literal-only attribute would otherwise leave silent);
• every test-side navigator that inspects the serialized [caixa-helm]-emitted Chart.yaml YAML mapping by the top- level chart-schema-apiVersion key.

A drift on the emitter’s serde-rename literal (a future refactor that dropped the #[serde(rename = "apiVersion")] attribute or changed the target key to "ApiVersion" / "apiversion" / "schemaVersion") would silently serialize the field under Rust’s default snake_case api_version: key, which Helm’s chart-schema parser rejects at helm lint / helm dependency build / helm template time with an “apiVersion is required” error — the failure surfaces far from the drift site, and every downstream lareira-<nome> chart consumer drops with no field naming the serde-rename-drift root cause. Same drift-detection- pin discipline the peer HELM_CHART_KEY_TYPE / HELM_CHART_KEY_APP_VERSION lifts (d29bc23) established on the sibling per-Chart.yaml serde-rename-literal-only axis pair — extends the discipline from the two axes those lifts closed onto the third and last serde-rename-literal-only axis at [caixa-helm]’s ChartYaml struct, so every #[serde(rename = "...")] literal on the struct threads through a canonical substrate-side &'static str with a paired drift-detection pin.