Documentation

Localization

Language, region, timezone, and model reply-language settings via nikcli locale. Source: packages/nikcli/src/cli/cmd/locale.ts.

Overview

The locale command controls the language and regional settings used by nikcli and, optionally, the language in which the underlying model replies. Settings are stored in the global nikcli config by default (--global is true). Pass --global false to write to the project-level nikcli.json instead.

When no overrides are set, nikcli auto-detects locale from the environment (LANG, LC_ALL, system timezone, etc.). Auto-detection can be disabled permanently with --no-auto-detect in a set call, or overridden for a single invocation with the environment variables described below.

Terminal

bash

nikcli locale           # show resolved locale (same as "locale show")
      nikcli locale show      # print current language, region, timezone, currency, reply language
      nikcli locale set ...   # apply one or more overrides
      nikcli locale reset     # clear all overrides and return to auto-detect

Actions

Action	Description
`show` (default)	Print the fully resolved locale fields: locale tag, language name, region, timezone, currency, reply language, and source (`auto-detect`, `config`, or `override`).
`set`	Apply one or more locale overrides. Any flags that are not supplied are left unchanged.
`reset`	Delete all stored locale overrides and revert to auto-detection from the environment.

Flags

All flags apply to the set action. Unrecognised values are stored as-is and resolved at runtime.

Flag	Format	Description
`--language`	BCP-47 language subtag (e.g. `it`, `ja`, `ar`)	Sets the primary language for display and model interaction.
`--region`	ISO-3166 country code (e.g. `IT`, `JP`, `US`)	Sets the regional variant used for formatting numbers, dates, and currency.
`--locale`	BCP-47 full tag (e.g. `it-IT`, `ja-JP`)	Sets both language and region in a single value. Overrides `--language` and `--region` when all three are supplied.
`--timezone`	IANA timezone (e.g. `Europe/Rome`, `Asia/Tokyo`, `America/New_York`)	Sets the timezone used in timestamps and date formatting.
`--currency`	ISO-4217 code (e.g. `EUR`, `JPY`, `USD`)	Sets the currency used in cost and usage displays.
`--reply-language`	`true` \| `false` \| BCP-47 tag (e.g. `fr`, `de`)	Steers the model's answer language independently of the CLI display language. See Reply Language below.
`--no-auto-detect`	boolean	Disables automatic locale detection from the environment. Only the stored config values are used.
`--global`	boolean (default `true`)	Write to the global config file. Pass `--global false` to write to the project-level `nikcli.json` instead.

Reply Language

--reply-language controls the language in which the underlying model responds. This is independent of the CLI display language — for example you can display the UI in English while asking the model to answer in French.

Value	Behaviour
`true` / `on` / `yes`	The model replies in the same language as the configured `--language`.
`false` / `off` / `no`	Reply-language steering is disabled; the model answers in its default language (usually English).
A BCP-47 tag (e.g. `fr`, `de`, `zh-TW`)	The model is steered to respond in the specified language, regardless of the CLI display language.

Terminal

bash

# CLI stays in English but model answers in French
      nikcli locale set --reply-language fr

      # Match reply language to the current --language setting
      nikcli locale set --language ja --reply-language true

      # Disable reply-language steering entirely
      nikcli locale set --reply-language false

Model support

Reply-language steering is a best-effort instruction injected into the system prompt. Model compliance varies by provider and model capability.

Environment Variable Overrides

Three environment variables override the stored config for a single invocation. They take effect even if auto-detection is disabled. The resolved locale source shows override when any of these is set.

Variable	Description
`NIKCLI_LOCALE`	Full BCP-47 locale tag, e.g. `it-IT`. Overrides both language and region.
`NIKCLI_LANGUAGE`	Language subtag only, e.g. `ja`.
`NIKCLI_REGION`	ISO-3166 country code only, e.g. `DE`.

Terminal

bash

# One-off run in Italian, regardless of stored config
      NIKCLI_LOCALE=it-IT nikcli run "spiega questo codice"

      # Override just the language
      NIKCLI_LANGUAGE=de nikcli run "erkläre diesen Code"

Examples

Terminal

bash

# Show the current resolved locale
      nikcli locale

      # Set Italian locale with Rome timezone and Euro currency
      nikcli locale set --language it --region IT --timezone Europe/Rome --currency EUR

      # Use the combined BCP-47 tag instead
      nikcli locale set --locale it-IT --timezone Europe/Rome --currency EUR

      # Ask the model to always reply in Japanese (CLI remains in English)
      nikcli locale set --reply-language ja

      # Set a project-level override (does not touch global config)
      nikcli locale set --language fr --global false

      # Disable auto-detection globally
      nikcli locale set --no-auto-detect

      # Reset all overrides and return to auto-detect
      nikcli locale reset