DeepSeek Reasonix CLI

Route DeepSeek Reasonix CLI through FastRouter for unified model access, observability, failover, and organizational controls.

What is DeepSeek Reasonix CLI?

DeepSeek Reasonix CLI is an open-source, DeepSeek-native AI coding agent that runs in your terminal. It supports DeepSeek-compatible model providers, including FastRouter.

By routing DeepSeek Reasonix CLI through FastRouter, you get:

• Unified API access through a single, consistent endpoint

• Provider failover and routing for outages, rate limits, and provider availability

• Unified observability for requests, latency, costs, and usage

• Bring Your Own Key (BYOK) support for centralized provider-key management

• Organization controls for projects, keys, budgets, and usage governance

This guide covers installing DeepSeek Reasonix CLI, creating a FastRouter API key, configuring ~/.reasonix/config.json, using the alternative installer, and installing the FastRouter Reasonix skill file. It does not cover general Reasonix usage outside FastRouter provider configuration.

Prerequisites

• Node.js and npm installed on your local machine

• A FastRouter account (dashboard)

• A FastRouter API key

• Terminal access to edit ~/.reasonix/config.json

---

Quick Start

Step 1: Install DeepSeek Reasonix CLI

Install Reasonix on your local machine. For platform-specific instructions, see the DeepSeek Reasonix GitHub repository.

npm install -g reasonix

Step 2: Create a FastRouter API Key

1. Sign up or log in to your FastRouter account.

2. Open the FastRouter dashboard.

3. Navigate to API Keys.

4. Create a new API key.

5. Copy and securely store your API key.

FastRouter API keys are only shown once. Store the key securely and do not commit it to source control.

Step 3: Configure DeepSeek Reasonix CLI to Use FastRouter

Edit ~/.reasonix/config.json and add the FastRouter API key, base URL, and model.

{
  "apiKey": "sk-v1-***",
  "baseUrl": "https://api.fastrouter.ai/api/v1",
  "model": "deepseek/deepseek-v3.2"
}

Step 4: Start DeepSeek Reasonix CLI

Start Reasonix from any project directory:

reasonix code

After configuration, Reasonix sends model requests through FastRouter.

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Alternative Install: Reasonix CLI with FastRouter

Use the FastRouter installer if you want a scripted setup. In the commands below, replace $API_KEY with your actual FastRouter API key.

One-Line Install Script

curl -fsSL https://fastrouter.ai/reasonix/install-fastrouter.sh | sh -s -- $API_KEY

Download, Inspect, Then Run

Use this option if you want to inspect the installer before running it.

curl -fsSL https://fastrouter.ai/reasonix/install-fastrouter.sh -o install-fastrouter.sh

less install-fastrouter.sh

chmod +x install-fastrouter.sh

./install-fastrouter.sh $API_KEY

---

Install Reasonix with the FastRouter Skill File

Reasonix can install the FastRouter setup skill directly from the hosted skill file.

reasonix skills install https://fastrouter.ai/reasonix/skill.md

Then ask Reasonix to install FastRouter with your key:

install fastrouter in reasonix with key <KEY>

The skill file is available at https://fastrouter.ai/reasonix/skill.md.

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Use DeepSeek Reasonix CLI with FastRouter Models

Reasonix uses the model value in ~/.reasonix/config.json. The default model in this guide is:

deepseek/deepseek-v3.2

To switch models, edit the model field in ~/.reasonix/config.json and restart Reasonix. Use a valid FastRouter model slug from the FastRouter models page.

Example DeepSeek-compatible slugs include:

deepseek/deepseek-v3.2
deepseek/deepseek-r1

---

Verify the Configuration

Check that Reasonix is installed:

reasonix --version

Check that ~/.reasonix/config.json contains the FastRouter settings. Do not print the full file if it contains a real API key.

jq 'del(.apiKey)' ~/.reasonix/config.json

Expected values:

Field	Expected value
baseUrl	https://api.fastrouter.ai/api/v1
model	deepseek/deepseek-v3.2
apiKey	A valid FastRouter key that starts with sk-v1-

For security, restrict the config file to the file owner:

chmod 600 ~/.reasonix/config.json

---

Why Use DeepSeek Reasonix CLI with FastRouter?

FastRouter centralizes access, routing, and governance for DeepSeek Reasonix CLI traffic.

Unified API

Access models from multiple AI providers through a single, consistent API interface.

Provider Failover & Routing

Automatically route requests to available providers and fail over during outages or rate limits.

Unified Observability

Monitor requests, latency, costs, and usage across all providers from a centralized dashboard.

Troubleshooting

Debug API requests, authentication, routing, and provider responses faster with FastRouter audit logs.

BYOK (Bring Your Own Key)

Use your own provider API keys while maintaining centralized routing and management.

Organization Controls

Manage organizations, projects, keys, and API usage with enterprise-grade governance controls.

---

Troubleshooting

Issue	Cause	Fix
401 or authentication error	The API key is missing, invalid, or redacted.	Confirm apiKey starts with sk-v1- and replace masked values such as *** or [REDACTED] with the real key.
Model not found	The model value is not a valid FastRouter slug.	Use a model slug from https://fastrouter.ai/models.
Reasonix still uses an old provider	An active Reasonix session loaded the previous config.	Restart reasonix code after editing ~/.reasonix/config.json.
Config values disappeared	The config file was overwritten instead of merged.	Re-add the apiKey, baseUrl, and model keys while preserving other settings.
API key appears in logs	The full config file was printed or shared.	Rotate the API key in FastRouter, update ~/.reasonix/config.json, and avoid using cat ~/.reasonix/config.json.

---

Security Notes

• Reasonix stores apiKey in ~/.reasonix/config.json in cleartext.

• Do not commit ~/.reasonix/config.json to git.

• Use chmod 600 ~/.reasonix/config.json to restrict file access.

• Show masked API keys only. Do not echo the full key in logs, screenshots, or support messages.

• If you accidentally expose a key, rotate it in the FastRouter dashboard.

---

FastRouter Reasonix Skill File Reference

You can find the skill.md file attached below, or at https://fastrouter.ai/reasonix/skill.md.

The skill configures fastrouter as the model provider in DeepSeek Reasonix CLI by writing apiKey, baseUrl, and model into ~/.reasonix/config.json. After setup, FastRouter models are invoked when the user runs reasonix code from any project.

---
name: reasonix-cli-fastrouter
description: "Install and configure FastRouter (https://fastrouter.ai) as the model provider in DeepSeek Reasonix CLI. Use this skill whenever the user asks to add, set up, install, configure, or register fastrouter as a provider in reasonix, edit ~/.reasonix/config.json, point reasonix or deepseek-reasonix at FastRouter, or wants to use FastRouter models with DeepSeek Reasonix CLI. The skill takes exactly one input: the FastRouter API key."
version: 1.0.0
author: FastRouter
license: MIT
metadata:
  reasonix:
    tags:
      [
        fastrouter,
        reasonix,
        deepseek,
        provider,
        setup,
        configuration,
        custom-provider,
        openai-compatible,
      ]
    homepage: https://fastrouter.ai
    docs: https://docs.fastrouter.ai
---

Inputs

This skill accepts exactly one input: the FastRouter API key. Everything else is hardcoded and must not be changed:

Field	Value
Provider	fastrouter
Base URL	https://api.fastrouter.ai/api/v1
Default model	deepseek/deepseek-v3.2
Config file	~/.reasonix/config.json
File mode	0600 (key is stored on disk)

When to Use This Skill

Trigger this skill when the user asks any of:

• "install fastrouter for reasonix"

• "install fastrouter in reasonix with key "

• "set up / configure / register fastrouter in reasonix"

• "add fastrouter as a provider in reasonix"

• "edit ~/.reasonix/config.json for fastrouter"

• "use fastrouter with deepseek reasonix cli"

• "point reasonix at fastrouter"

• "configure deepseek reasonix with fastrouter"

Anything similar referencing reasonix (or "deepseek reasonix") plus install / setup / configure / add / register / provider plus fastrouter should trigger it.

Extracting the API Key (single-argument rule)

Treat every invocation as a single-argument call: setup(api_key). Find the key in the user's message using these rules, in order:

1. If the message contains key=<value>, --key <value>, --api-key <value>, or apiKey=<value>, the value is the key.

2. Else, the last whitespace-separated token in the message that looks like an API key is the key. A token "looks like an API key" if it matches ^sk-v1-[A-Za-z0-9_\-]+$ (FastRouter keys always have the prefix sk-v1- followed by a random string of letters/digits/dashes/underscores).

3. Else, ask the user once: "Please paste your FastRouter API key (just the key, nothing else)." Then treat their next message as the key verbatim, after stripping surrounding whitespace and quotes.

Examples of correct extraction:

User message	Extracted key
install fastrouter for reasonix with key sk-v1-abc123	sk-v1-abc123
setup reasonix with fastrouter sk-v1-abc123	sk-v1-abc123
configure reasonix --api-key sk-v1-XYZ789	sk-v1-XYZ789
add fastrouter to reasonix key=sk-v1-9aBc_def-456	sk-v1-9aBc_def-456
set up reasonix with fastrouter	(prompt the user)

Once extracted, never modify, paraphrase, or transform the key. Do not strip characters you think are formatting. Do not lowercase. Do not echo the full key back to the user - only ever show it masked (**** + last 4 chars) in confirmations.

Redaction Check (do this before writing)

Some agent harnesses (Cursor, IDE extensions, CI loggers) may redact secrets in messages before the model sees them. After extracting the key, validate it. The key is invalid for write if any of:

• Equals [REDACTED], <redacted>, ***, ***REDACTED***, or any string containing the substring REDACTED (case-insensitive)

• Does not start with the literal prefix sk-v1- (all real FastRouter keys begin with sk-v1-; anything else is either redacted, mistyped, or from a different provider)

• Has nothing after the sk-v1- prefix (i.e. the random portion is empty)

• Contains only * or • characters

• Is empty / whitespace-only

If the key fails validation due to redaction, stop and tell the user:

"It looks like your environment is masking the API key before I can read it. To install fastrouter for Reasonix, please run these in your terminal directly so the key never passes through the model:

mkdir -p ~/.reasonix
cat > ~/.reasonix/config.json <<'EOF'
{
  "apiKey": "<YOUR_KEY>",
  "baseUrl": "https://api.fastrouter.ai/api/v1",
  "model": "deepseek/deepseek-v3.2"
}
EOF
chmod 600 ~/.reasonix/config.json

If ~/.reasonix/config.json already exists with other settings, edit it manually and merge the three keys above instead of overwriting."

Do not proceed with a redacted-looking value - writing [REDACTED] as apiKey silently breaks the provider with 401 errors that look unrelated to redaction.

Procedure

Once you have a valid key, follow these steps in order.

Step 1: Ensure Reasonix CLI is installed

Run via the terminal tool:

reasonix --version

If reasonix is not found, install it first:

npm install -g reasonix
reasonix --version

Reference: https://github.com/esengine/DeepSeek-Reasonix.

Step 2: Ensure ~/.reasonix/config.json exists

mkdir -p ~/.reasonix
[ -f ~/.reasonix/config.json ] || echo '{}' > ~/.reasonix/config.json

If the user prefers an interactive setup, they can instead run reasonix code once and paste the API key when prompted — Reasonix's built-in wizard generates the file automatically. Either path produces the same end state, but only proceed past this step once ~/.reasonix/config.json exists.

Step 3: Write the FastRouter config

Reasonix config is a flat JSON object. Merge these three keys, preserving any other existing keys in the file. Use the extracted key exactly as-is — never rename, lowercase, or transform it.

Required keys:

{
  "apiKey": "<USER_KEY>",
  "baseUrl": "https://api.fastrouter.ai/api/v1",
  "model": "deepseek/deepseek-v3.2"
}

Safe merge with jq (preferred — preserves other keys):

KEY="<USER_KEY>"
jq --arg key "$KEY" \
   '. + {apiKey: $key, baseUrl: "https://api.fastrouter.ai/api/v1", model: "deepseek/deepseek-v3.2"}' \
   ~/.reasonix/config.json > ~/.reasonix/config.json.tmp \
   && mv ~/.reasonix/config.json.tmp ~/.reasonix/config.json

Fallback merge with Python (when jq is unavailable):

python3 - "<USER_KEY>" <<'PY'
import json, os, sys
key = sys.argv[1]
path = os.path.expanduser("~/.reasonix/config.json")
try:
    with open(path) as f: cfg = json.load(f)
except Exception:
    cfg = {}
cfg["apiKey"]  = key
cfg["baseUrl"] = "https://api.fastrouter.ai/api/v1"
cfg["model"]   = "deepseek/deepseek-v3.2"
with open(path, "w") as f: json.dump(cfg, f, indent=2)
PY

Step 4: Restrict file permissions

The API key is stored on disk in cleartext. Make the file owner-only:

chmod 600 ~/.reasonix/config.json

Step 5: Verify

ls -l ~/.reasonix/config.json
jq 'del(.apiKey)' ~/.reasonix/config.json
jq -r '.apiKey | "apiKey ends in: ****" + .[-4:]' ~/.reasonix/config.json

Expected:

• File mode is -rw------- (octal 0600)

• baseUrl is "https://api.fastrouter.ai/api/v1" exactly

• model is "deepseek/deepseek-v3.2" (or the user-specified slug)

• Masked key suffix matches the last 4 chars the user provided

Never cat or otherwise dump the full file — the apiKey is in cleartext. Always use the jq 'del(.apiKey)' form when showing config.

Step 6: Report success

Reply to the user with usage examples. Show the API key only masked.

✓ FastRouter is configured for DeepSeek Reasonix CLI (****<last 4 chars>).

Start Reasonix from any project:

cd /path/to/your/project
reasonix code

Switch models by editing model in ~/.reasonix/config.json. Browse available DeepSeek slugs at https://fastrouter.ai/models.

Step 7: Optional model wiring

If (and only if) the user named a specific model in their request, set it as model instead of the default deepseek/deepseek-v3.2:

jq --arg m "<that_model>" '.model = $m' \
   ~/.reasonix/config.json > ~/.reasonix/config.json.tmp \
   && mv ~/.reasonix/config.json.tmp ~/.reasonix/config.json

Otherwise leave "model": "deepseek/deepseek-v3.2" untouched.

Pitfalls

• The API key IS stored in the config file. Reasonix reads apiKey directly from ~/.reasonix/config.json in cleartext (no env-var indirection). Never commit this file to git or share it. Always chmod 600 after writing. Add .reasonix/ and **/.reasonix/config.json to global ~/.gitignore if the user version-controls dotfiles.

• Don't cat ~/.reasonix/config.json when output may be streamed to logs, chat, or terminal recordings — the key is in cleartext. Use jq 'del(.apiKey)' for inspection.

• Use merge, not overwrite. A naive echo '{...}' > ~/.reasonix/config.json will wipe any other Reasonix settings the user has. Always merge via jq or the Python fallback.

• Restart reasonix after changing the config. An active session has the old config in memory; new values only apply to the next run.

• Don't run reasonix code mid-config-write. The interactive wizard may overwrite fields. Finish the procedure first, then launch.

• Model slug must exist on FastRouter. Use slugs from https://fastrouter.ai/models (DeepSeek-compatible models include deepseek/deepseek-v3.2, deepseek/deepseek-r1, etc.). A bad slug returns 404 from FastRouter, surfacing in Reasonix as a "model not found" error.

• Redacted keys silently corrupt config. Always run the redaction check before writing. Writing [REDACTED] (or pasting a masked key) as apiKey produces 401 errors later that look unrelated to redaction.

• Never echo the full key back. Only show it masked (last 4 chars). Some platforms log assistant output verbatim.

Verification Checklist

Before reporting success, confirm:

• Exactly one key was extracted (Inputs rule)

• The key passed the redaction check (starts with sk-v1-, no REDACTED substring)

• ~/.reasonix/config.json exists and contains all three required keys (apiKey, baseUrl, model)

• baseUrl equals https://api.fastrouter.ai/api/v1 exactly

• File mode is 0600 (owner read/write only)

• Other pre-existing keys in the file were preserved (merge, not overwrite)

• You did NOT echo the raw API key - only masked form

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References

• DeepSeek Reasonix: https://github.com/esengine/DeepSeek-Reasonix

• FastRouter dashboard: https://dashboard.fastrouter.ai/

• FastRouter API base: https://api.fastrouter.ai/api/v1

• FastRouter models: https://fastrouter.ai/models

• FastRouter docs: https://docs.fastrouter.ai

• FastRouter Reasonix skill file: https://fastrouter.ai/reasonix/skill.md