Claude Code

Connect the Claude Code CLI to Fireworks with the Nexus CLI or manual setup, and use Nexus Auto with your Claude login.

Connect the Claude Code CLI to Fireworks models and Nexus Auto. Your Claude login stays signed in for Anthropic model turns.

Generally available Anthropic Messages Nexus Auto Native web search

Quick start

1. Install and sign in

   curl -fsSL https://nexus.fireworks.ai/install.sh | bash
   

   You need Node.js 22 or later, git, and bash. On Windows, run the installer from Git Bash. PowerShell breaks the script’s line endings.

   nexus login
   

   Sign in with your browser, or paste a Fireworks API key (fw_...).

   Already set up? Skip to step 2.

2. Connect Claude Code

   nexus claude
   nexus claude status
   

   Nexus CLI selects Nexus Auto by default. To choose another model, pass --model:

   nexus claude --model glm-5p3-flash
   

   --model sets the default model for new sessions and adds it to /model. /model also lists the Fireworks catalog and an Auto row for Nexus Auto (auto). Your own picker rows are not changed. Set effort in that same picker.

   To send one Anthropic model tier or your subagents to a specific model, pin that slot:

   nexus claude --sonnet deepseek-flash-latest --subagent deepseek-flash-latest
   

   Tier flags are --opus, --sonnet, --haiku, --fable, and --subagent. Unpinned slots stay on Claude Code’s defaults. Running nexus claude again keeps your pins. Pass native, such as --sonnet native, to release a slot.

3. Restart and pick a model

   Start a new session, or exit and run claude --resume <id>. Open /model:

   

   Fireworks models in the Claude Code model picker

   nexus claude status shows the provider, where the key comes from, and the configured model.

   The Fireworks catalog in /model needs Claude Code 2.1.242 or later. On an older version, nexus claude says so. Run claude update, then nexus claude again.

Use Nexus Auto

Nexus Auto (auto) is supported on the Messages API.

• Anthropic model turns: your Claude login (OAuth), or an exported ANTHROPIC_API_KEY.
• OpenAI model turns: connect an OpenAI Provider Key, or save your own key with nexus auto --openai-api-key (it prompts for the key) and run nexus claude again. Nexus CLI adds the saved key to ANTHROPIC_CUSTOM_HEADERS.
• Nexus CLI never sends an Anthropic key you saved with nexus auto to Claude Code. Your Claude login covers Anthropic model turns.
• See which models auto can use.
• Manual setup: send x-anthropic-api-key and x-openai-api-key headers yourself. See Manual setup (advanced).

MCP and tools

Your MCP servers stay in ~/.claude.json. Nexus CLI sets ENABLE_TOOL_SEARCH so MCP tool search stays on.

Add a server with claude mcp add <name> -- <command>, and confirm it’s configured:

claude mcp list
# docs: npx -y your-mcp-server - ✔ Connected

Native web search and web fetch keep working while connected through Nexus CLI. Fireworks runs the search server-side and returns the results. You don’t need an MCP server or a search service.

Usage and cost

For the session cost status line, nexus claude usage, and how its estimate differs from Claude Code’s own cost, see Usage and Cost.

Troubleshooting

• Upgrading from an earlier version? See Upgrading from earlier versions.
• Text-only models fail on pasted images. Use /rewind, or switch to a vision model such as glm-5p3-flash.
• Resume or restart the session after changing models.
• /model doesn’t list the Fireworks catalog: update Claude Code to 2.1.242 or later with claude update, then run nexus claude again.
• Auto mode says classifier requests are billed: this notice is expected. It appears once per session, and auto mode keeps working. The safety checks run on your Sonnet slot, so they bill to Anthropic. To bill them at Fireworks rates, pin Sonnet with nexus claude --sonnet <id>.

Manual setup (advanced)

1. Point Claude Code at Fireworks

   Add these values to ~/.claude/settings.json:

   ~/.claude/settings.json

   {
     "env": {
       "ANTHROPIC_BASE_URL": "https://api.fireworks.ai/inference",
       "ANTHROPIC_AUTH_TOKEN": "fw_YOUR_FIREWORKS_API_KEY",
       "ENABLE_TOOL_SEARCH": "true"
     },
     "model": "glm-latest"
   }
   

   ENABLE_TOOL_SEARCH keeps MCP tool search on. Claude Code turns it off when ANTHROPIC_BASE_URL points anywhere other than Anthropic.

   Or set them for one shell:

   export ANTHROPIC_BASE_URL="https://api.fireworks.ai/inference"
   export ANTHROPIC_API_KEY="$FIREWORKS_API_KEY"
   claude --model glm-latest
   

   ANTHROPIC_AUTH_TOKEN sends the key as an Authorization: Bearer header. ANTHROPIC_API_KEY sends it as an x-api-key header, so Claude Code asks you to approve it.

2. Start a session

   Run claude. Claude Code may ask once whether to use the API key; approve it.

3. Optional: use Nexus Auto

   Set "model": "auto". For Anthropic model turns, connect an Anthropic Provider Key, or add x-anthropic-api-key to ANTHROPIC_CUSTOM_HEADERS.

Claude Code’s /model picker does not list Fireworks models you set by hand. Change models in settings.json or with claude --model <id>. Claude Code may log unrecognized_model for Fireworks IDs; requests still succeed.

See what changes without the Nexus CLI.

What the Nexus CLI writes

~

.claude

settings.json

.claude.json

.nexus

See what Nexus CLI writes

~/.claude/settings.json

{
  "env": {
    "ANTHROPIC_BASE_URL": "https://api.fireworks.ai/inference",
    "ANTHROPIC_CUSTOM_HEADERS": "X-Fireworks-Api-Key: fw_...\nX-Title: Claude Code\nHTTP-Referer: nexus/v<version>",
    "CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING": "1",
    "ENABLE_TOOL_SEARCH": "true",
    "CLAUDE_CODE_DISABLE_EXPLORE_INHERIT_CAP": "1"
  },
  "modelPicker": {
    "options": [
      { "model": "auto[1m]", "label": "Auto" }
    ]
  },
  "model": "auto[1m]",
  "statusLine": { "type": "command", "command": "... claude-statusline.mjs" }
}

• The Fireworks key goes in a custom header, so your Claude login stays available for Anthropic model turns. The same header names the client (X-Title, HTTP-Referer).
• An OpenAI key saved with nexus auto --openai-api-key adds an x-openai-api-key line to that header.
• [1m] marks 1M-context models.
• A pinned tier adds ANTHROPIC_DEFAULT_<TIER>_MODEL to env, such as ANTHROPIC_DEFAULT_SONNET_MODEL. A pinned subagent adds CLAUDE_CODE_SUBAGENT_MODEL.
• The status line shows the estimated session cost and, on auto, the model that served the latest turn. Nexus CLI adds it only if you don’t already have one.
• The other env values turn off adaptive thinking, keep MCP tool search on, and let the Explore agent inherit the session model. Exploration then stays on Fireworks rates.
• Nexus CLI leaves Claude Code telemetry and auto-updates as you have them. An upgrade removes the telemetry and auto-update settings that earlier versions wrote.
• ~/.claude.json: if you export ANTHROPIC_API_KEY, Nexus CLI pre-approves it so Claude Code doesn’t prompt. Nexus CLI also removes its retired fireworks-websearch server from this file.

Claude Agent SDK

Preview Anthropic Messages

The Claude Agent SDK can reuse the Claude Code settings above. Connect Claude Code first, with Nexus CLI or manually:

nexus claude --model auto

In the SDK query options, include settingSources: ["user"]. The SDK then reads the Fireworks endpoint, model, and credentials from ~/.claude/settings.json.

Nexus CLI doesn’t touch MCP for the SDK. MCP follows the setting sources your application loads.

nexus claude does not configure Claude Desktop. See Claude Desktop.