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Builtins catalog / nika:write

File

Tool family from the canonical registry.

invoke

Call this builtin through the invoke verb.

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Read this contract

This reference preserves the specification at the revision linked below. Source examples are fragments: their surrounding tasks, inputs and permissions are not supplied here. Consult engine status and nika catalog --tools --json for the installed implementation; a registry declaration is not a runtime qualification.

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Usage and behavior

illustration
Write a file · path: names a FILE, never a directory · returns the path. A binary content value (an opaque bytes output from an upstream tool · e.g. MCP image content) is written as-is · no output_format declaration needed (the value carries its own type). A directory is never the target: it is made by writing its first file inside it with create_dirs: true, never by an empty write at the directory’s path. overwrite: defaults true · create_dirs: defaults false — and a false create_dirs: is ENFORCED, not ignored: a missing parent directory is refused loudly (a typo’d path surfaces rather than silently materializing a directory tree), so pass create_dirs: true to create the parent. One carve-out, by decision (engine #433 option C): a declared permits.fs.write entry covering the target path IS the intent — the boundary creates the parent tree before the builtin’s gate, and the write lands without create_dirs: (measured on the reference engine: a literal grant deep/dir/new.txt and a glob grant out/** both materialize their tree · run green). The refusal keeps its teeth where no declared grant covers the path — and there the boundary itself speaks first: an uncovered write is NIKA-SEC-004 before the parent gate can. A typo’d path under a narrow grant still surfaces (it falls outside the grant → SEC-004); the tree-scatter the enforcement exists to catch cannot hide inside a boundary the author drew. Throws · NIKA-BUILTIN-WRITE-001 (IO failure, or a missing parent while create_dirs: false outside a covering grant · a directory-shaped path: — a trailing / is write failed: path not found, an existing directory is filesystem I/O error: Is a directory · a file in the way of create_dirs: — create_dirs failed: path already exists, the mark an earlier empty write at the directory’s path leaves behind, and nothing deletes it; all three measured on the reference engine 0.118.7) · -002 (overwrite: false and the path exists). Both tool_error · transient: false.

Arguments

Pass the values required by the tool contract.

Permissions

Understand authority before granting effects.

Errors and recovery

Read diagnostics and choose a recovery policy.

Workflow templates

Put the fragment inside a complete workflow.

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Contract provenance

Read the pinned specification · Canonical registry. Tool identity: nika:write. Specification revision: f8c5df2127c7. The Lab language identity is language:tool:write; the registry view is ecosystem:tool/nika:write. They refer to this contract without merging their graph identities.