Config reference

The wit.sources.json schema, the built-in env source, the format catalogue, and the security model behind --allow-exec. Source: packages/cli/src/data-sources.ts, packages/runtime/src/data-loader.ts.

wit.sources.json

{
  "sources": {
    "<alias>": {
      "run": ["program", "arg", "{{capture}}"],
      "format": "json",
      "timeoutMs": 30000
    }
  }
}

Schema fields
Field	Required	Meaning	Default
sources	yes	top-level object of aliases	—
alias.run	yes	non-empty argv array; first element is the program	—
alias.format	no	one of the seven formats	json
alias.timeoutMs	no	spawn timeout in ms	30000

A missing or non-object sources → expected a top-level "sources" object. An empty or non-array run → source "run" must be a non-empty argv array. Any {{name}} token in run is replaced by the matching capture value (missing → empty string). Output cap: 16 MB.

Formats — 7

The value that crosses the seam from a program's stdout.

Formats
Format	stdout becomes
json	parsed JSON — empty is null
csv	array of records; first row is the header
tsv	same but tab-delimited
lines	array of non-empty lines
text	the raw string
svg	the raw string
html	the raw string

The built-in env source

No config needed. @load env load@ returns process.env merged with the --env dotenv file, as a record; access it with dotted paths.

@load env load@

User is @env.USER

The dotenv parser reads KEY=value lines, treats # as a comment, strips optional surrounding quotes, and skips blank or key-less lines. The env source needs no --allow-exec.

Binding forms for load

Binding forms
Form	Effect
body prose alias	names the source to load
from alias pipe	names the source explicitly
as name pipe	renames the resulting data def
any other named pipe	becomes a capture passed to the program

@load results load@
@load sales |from warehouse| |as rows| |region West| load@

A @load with no resolvable alias → E_LOAD_FAILED(@load needs an alias). The def is named for the alias unless as renames it.

Security and capture-passing

Security model
Rule	Behaviour
--allow-exec required	without it any non-env load throws
unknown alias	no source configured for that alias
child cwd	the document's directory
child env	the merged environment
captures via argv	name tokens substituted into run
captures via stdin	the full args object as JSON
non-zero exit or spawn error	surfaces as E_LOAD_FAILED at the load site