# How to Configure the Reasoning Language Display (auto, zh, en) in Reasonix > Learn to configure the reasoning language display auto zh en in Reasonix using agent.reasoning_language. Easily control visible reasoning text for your needs. - Repository: [YHH/DeepSeek-Reasonix](https://github.com/esengine/DeepSeek-Reasonix) - Tags: how-to-guide - Published: 2026-08-05 --- **Reasonix controls visible reasoning text language via the `agent.reasoning_language` setting, which accepts `auto`, `zh`, or `en` and prepends a transient `` block to user turns without altering system prompts.** The **DeepSeek-Reasonix** repository provides a configurable reasoning language feature that lets you dictate whether the model's visible thinking process appears in Simplified Chinese, English, or automatic detection. This setting, configured under the `[agent]` section, affects only the *displayed* reasoning text and never changes the final answer language or code output. By injecting a small transient block rather than modifying system prompts, Reasonix maintains high cache-hit rates while giving users full control over the linguistic presentation of the model's thought process. ## Understanding the Reasoning Language Modes Reasonix supports three distinct modes for the `reasoning_language` parameter, each triggering different behavior in [`internal/agent/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/agent/reasoning_language.go). | Mode | Behavior | |------|----------| | **auto** | Automatically injects a `` block when the raw user prompt is clearly Chinese. English or ambiguous prompts receive no extra instruction. | | **zh** | Forces visible reasoning to appear in Simplified Chinese for the entire turn. | | **en** | Forces visible reasoning to appear in English for the entire turn. | The preference applies **transiently** by prepending the `` directive to the user turn immediately before the model call. This approach preserves the system prompt and tool schemas unchanged, ensuring consistent cache behavior across requests. ## Configuration Methods You can adjust the reasoning language through four interfaces, depending on your workflow context. ### Desktop UI Configuration Navigate to **Settings → Models → Usage → Agent runtime → Thinking language** in the Reasonix desktop application. The UI writes the selected value to your user-level configuration file at `~/.reasonix/config.toml`. ### CLI Commands Use the `reasonix config reasoning-language` command to set the global preference or a project-local override. ```bash # Set global preference to automatic detection reasonix config reasoning-language auto # Force Chinese reasoning output globally reasonix config reasoning-language zh # Set English for the current project only reasonix config reasoning-language --local en ``` The `--local` flag writes the setting to [`./reasonix.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/./reasonix.toml) in your current working directory instead of the global user config. ### Slash Commands During Sessions While chatting in a Reasonix session, use the slash command to change the language dynamically. This updates the current chat controller and persists the setting to your user-level config. ```text /reasoning-language auto /reasoning-language zh /reasoning-language en ``` The slash command implementation resides in [`internal/cli/slash_registry.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/cli/slash_registry.go), which registers the command and provides completion hints. Note that this method does **not** modify the project's [`reasonix.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/reasonix.toml); use the CLI with `--local` for permanent project overrides. ### TOML Configuration Files Represent the setting explicitly in TOML format for version-controlled projects or shared configurations. ```toml [agent] reasoning_language = "auto" # auto | zh | en ``` Reference the example configuration in [`reasonix.example.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/reasonix.example.toml) for additional `[agent]` section options. ## Configuration Resolution Order Reasonix resolves the `reasoning_language` setting using a hierarchical fallback mechanism: ```text ./reasonix.toml → ~/.reasonix/config.toml → built-in defaults ``` Project-local settings take precedence over user preferences, allowing repository-specific language requirements without affecting global behavior. No dedicated command-line flag exists for single invocations because the preference belongs to the user or project context rather than individual executions. ## Technical Implementation The reasoning language feature spans multiple components in the DeepSeek-Reasonix codebase: - **[`internal/cli/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/cli/reasoning_language.go)**: Implements the `reasonix config reasoning-language` CLI command, handling argument parsing and status messages. - **[`internal/agent/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/agent/reasoning_language.go)**: Generates the transient `` blocks for all three modes and provides the `WithReasoningLanguage` helper function that injects these blocks into user turns. - **[`internal/cli/slash_registry.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/cli/slash_registry.go)**: Registers the `/reasoning-language` slash command for runtime adjustment. - **[`docs/REASONING_LANGUAGE.md`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/docs/REASONING_LANGUAGE.md)**: Contains comprehensive user-facing documentation covering UI locations, CLI syntax, and configuration examples. These components work together to provide the full stack for configuring Reasonix's visible reasoning language across desktop, CLI/TUI, and programmatic contexts. ## Summary - Reasonix uses `agent.reasoning_language` with values `auto`, `zh`, or `en` to control visible thinking text. - The setting injects a transient `` block without modifying system prompts, preserving cache efficiency. - Configure via Desktop UI, CLI (`reasonix config reasoning-language`), slash commands (`/reasoning-language`), or TOML files. - Resolution follows the order: project [`reasonix.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/reasonix.toml) → user [`config.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/config.toml) → defaults. - Source implementations reside in [`internal/agent/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/agent/reasoning_language.go) and [`internal/cli/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/cli/reasoning_language.go). ## Frequently Asked Questions ### Does changing the reasoning language affect the model's final output language? No. The `reasoning_language` setting controls only the visible thinking process that the model emits before generating the final response. It does not constrain the language of the final answer, code blocks, or tool outputs. According to the implementation in [`internal/agent/reasoning_language.go`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/internal/agent/reasoning_language.go), the directive applies transiently to the reasoning phase only. ### What is the difference between `auto` mode and explicitly setting `zh` or `en`? **Auto** mode analyzes the raw user prompt to detect Chinese text, injecting a `` block only when the input is clearly Chinese. English or ambiguous prompts receive no special instruction. Setting **zh** or **en** explicitly forces that language for the reasoning text regardless of input language, ensuring consistent thinking display across all turns. ### Can I set different reasoning languages for different projects? Yes. Use the `--local` flag with the CLI command to write the setting to the project's [`./reasonix.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/./reasonix.toml) file: `reasonix config reasoning-language --local zh`. Project-local configurations override user-level settings, allowing per-repository language preferences without affecting your global `~/.reasonix/config.toml`. ### Why doesn't Reasonix use a command-line flag for reasoning language? The reasoning language preference belongs to the user or project context rather than a single invocation. Since the setting persists across sessions and affects how the agent interprets requests over time, it is managed through configuration files ([`reasonix.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/reasonix.toml) or [`config.toml`](https://github.com/esengine/DeepSeek-Reasonix/blob/main/config.toml)) rather than ephemeral command-line flags. This design ensures consistent behavior across desktop, CLI, and TUI interfaces.