Module err_ctx 

Substrate primitive over Result<T, E> for any E: [std::fmt:: Display] — the ONE substrate owner of the generic .map_err(|e| anyhow::anyhow!("<ctx>: {e}")) display-prefix wrap-shape for consumers whose source error is a bare Display type NOT already covered by a per-error-type flatten-wrap peer.

Peer of the type-specific flatten-wrap trait trio already in this crate on the same display-prefix wrap axis, partitioning the space by SPECIFICITY:

• crate::kube_error::KubeResultExt::kube_ctx — the specialized peer for Result<T, kube::Error>, kept because kube::Error’s Display composes the request URI + status line in a shape every reconciler-side callsite already greps on.
• crate::hostname::HostnameResultExt::hostname_ctx — the specialized peer for Result<T, crate::hostname::HostnameError>, kept because the thiserror-derived Display output matches the pre-lift hand-authored render_routing log stream verbatim.
• crate::anyhow_flatten::FlattenCtxExt::flatten_ctx — the specialized peer for anyhow::Result<T>, kept because it collides with anyhow::Context::context’s naming so the distinct-method-name discipline (flatten-prefix vs. chain-wrap semantics) is load-bearing at every phase-machine callsite.
• ErrCtxExt::err_ctx (this trait) — the generic fallback for any E: Display NOT covered by the three specialized peers, so a new consumer whose source error is a fresh [crate::tagged_union::declare_tagged_union_error]-derived variant (e.g. crate::export::ArtifactError, crate::intent::IntentError, crate::lifetime::LifetimeError) reaches the display-prefix wrap-shape mechanically at ONE substrate owner instead of opening a fourth per-error-type peer trait for every fresh thiserror-derived enum.

Pre-lift the shape was hand-authored at TWO tatara-export-worker/src/main.rs sites past the ★★ PRIME-DIRECTIVE ≥ 2 duplication threshold, both restating the SAME closure — capture an crate::export::ArtifactError returned by the substrate primitive crate::export::ArtifactSource::variant, prepend the identical static context slug "source", delegate the tail to std::fmt::Display via the {e} slot — differing in NOTHING but their line numbers. Post-lift both callsites read spec.source.variant().err_ctx("source")? and the wrap-shape lives at ONE substrate owner here.

Naming — err_ctx, not context

Same discipline as the three specialized peers: the method name err_ctx is deliberately DISTINCT from anyhow::Context::context so a caller with anyhow::Context in scope can never resolve to the wrong method (which chain-wraps rather than display-prefix- flattens, and would silently drop the underlying error detail from every downstream tracing::error!(error = %e, ...) log line whose formatter interpolates {e} rather than the chain-walking {e:#}).

Two flavors: err_ctx + err_ctx_with

• ErrCtxExt::err_ctx takes a &'static str context — the most common shape ("source" at the two export-worker callsites). Static binding keeps the compile-time contract that the context slug is a bare literal, no allocation, no dynamic content leaking into an error stream downstream operators grep on.
• ErrCtxExt::err_ctx_with takes an owned String context — the escape hatch for future consumers that compose the slug via format! (e.g. a dynamic per-variant-name slug the way crate::anyhow_flatten::FlattenCtxExt::flatten_ctx_with already services for phase_machine::evaluate_conditions).

#[must_use]

Every consumer threads the ? short-circuit onto its handler’s anyhow::Result<_> return — dropping the wrap swallows the underlying failure entirely, which is never the intended semantic.

Theory anchor: THEORY.md §VI.1 (generation over composition — the generic display-prefix wrap-shape recurred at two byte-identical hand-authored sites in tatara-export-worker/src/main.rs past the ★★ PRIME-DIRECTIVE ≥ 2 duplication trigger, and is lifted to ONE substrate owner here). THEORY.md §II.1 invariant 5 (composition preserves proofs — a regression that drifts the display-prefix separator or the byte-shape surfaces here at the substrate pin rather than as silent operator-facing skew across every downstream err_ctx consumer).

Traits

ErrCtxExt

Substrate extension trait over Result<T, E> for any E: std::fmt::Display — the ONE substrate owner of the generic .map_err(|e| anyhow::anyhow!("<ctx>: {e}")) display-prefix wrap-shape for consumers whose source error is a bare Display type NOT already covered by a per-error-type flatten-wrap peer. See the module docs for the specialized-peer partition + the naming rationale (why err_ctx and not context).