on_codes

the failure grammar · this word only ever speaks inside the recovery block, so meeting it means you are reading what happens when something breaks

Descriptions are the schema's own; the deeper invariants (value languages and regexes) ride the same projection. A miss is a nika check finding before anything runs.

retry

arrayRetry ONLY on these canonical `NIKA-<NS>-<NNN>` codes · absent, the engine retries anything transient. Codes, never HTTP status numbers · the retry-side mirror of `on_error.on_codes`.inside retry:^NIKA-[A-Z]{2,9}(-[A-Z][A-Z0-9_]{1,15})?-[0-9]{3}$

on_error

arrayOptional catch-side filter (mirror of retry.on_codes · same regex) · the action applies ONLY when the final error code is listed · unlisted codes fall through to the default fail (spec/05-errors.md §Fields).inside on_error:^NIKA-[A-Z]{2,9}(-[A-Z][A-Z0-9_]{1,15})?-[0-9]{3}$

49  gather:50    ◆invoke:                         # SLOT: the fact source · nika:read / nika:fetch / exec51      tool: "nika:read"52      args: { path: "${{ const.source }}" }53    on_error:54      # Offline rehearsal. A freshly scaffolded directory has no README, and a55      # skeleton that dies on its first run teaches nothing — so a not-found56      # recovers into a literal standing in for the real document. `on_codes:`57      # keeps that narrow: ONLY not-found is forgiven, a permission error58      # still fails loudly. Delete this block once the source really exists.59      # In an EMPTY directory check prints one [inputs] hint that this read60      # would fail — the run does not: this recover carries it (measured ·61      # rc=0 · « 1 recovered »). The hint retires once your source exists.62      on_codes: [NIKA-BUILTIN-READ-001]63      recover: "REHEARSAL · no source document here yet."

a verbatim slice, real line numbers from chain.nika.yaml, conformance-gated upstream on every spec push. open the full skeleton →