Harness Compatibility

Compare FireRouter support, closed-model credentials, and MCP behavior across coding harnesses connected through FireConnect.

Use this page to check whether FireConnect can add FireRouter to your harness and what it changes about Model Context Protocol (MCP) configuration. For setup commands and restart rules, see Coding Harnesses.

FireRouter

Harness	Request API	FireRouter compatibility	Local provider credentials
Claude Code	Messages	Supports firerouter and firerouter/... IDs	Anthropic login, OAuth, or ANTHROPIC_API_KEY
Claude Agent SDK	Messages	Supported when the SDK reads the user settings written by FireConnect	Same as Claude Code
OpenCode	Chat Completions	Supports firerouter and firerouter/... IDs	Anthropic key
Codex	Responses	Supports firerouter and firerouter/... IDs	ANTHROPIC_API_KEY environment reference
Codex app, ChatGPT desktop	Responses	Uses the FireRouter IDs registered through the shared Codex configuration	No separate local provider-key configuration
Pi	Chat Completions	Supports firerouter and firerouter/... IDs	Anthropic key
Cursor IDE	Chat Completions	Partial: FireConnect rejects routes that require an Anthropic credential	None
VS Code	Chat Completions	Supports firerouter and firerouter/... IDs	Anthropic key
Copilot App	Chat Completions	Partial: FireConnect rejects routes that require an Anthropic credential	None
Copilot CLI	Chat Completions	Partial: FireConnect rejects routes that require an Anthropic credential. Manual setup supports them	Provider-key headers in manual setup
DeepSeek Harness	Chat Completions	Partial: FireConnect rejects routes that require an Anthropic credential. Manual setup supports them	Provider-key headers in manual setup
Claude Desktop	Not applicable	Not supported by FireConnect	Not applicable

Provide a local Anthropic key. Where a harness supports one, pass it when you connect, or store it once for every harness:

fireconnect opencode --model firerouter/opus --anthropic-api-key "$ANTHROPIC_API_KEY"
fireconnect configure --anthropic-api-key "$ANTHROPIC_API_KEY"

FireConnect also reads ANTHROPIC_API_KEY from your environment. Codex stores an ANTHROPIC_API_KEY environment reference, so export the key in the shell that starts Codex.

FireConnect refuses routes that need a local Anthropic key on Cursor IDE, Copilot App, Copilot CLI, and DeepSeek Harness. Cursor IDE and the Copilot App cannot send extra headers, so they need an Anthropic Provider Key and manual setup. Copilot CLI and DeepSeek Harness can send the header with manual setup. Routes with only Fireworks models work on every harness.

OpenAI models. FireConnect has no local OpenAI-key option yet. Connect an OpenAI key in Provider Keys, or send x-openai-api-key with manual setup on any harness except Cursor IDE and the Copilot App. Provider Keys is not yet available on every account; contact the Fireworks team to enable it. For direct HTTP calls, see APIs and SDKs or LLM Gateways.

Automated live-inference validation covers Claude Code, OpenCode, Codex, Pi, and DeepSeek Harness. Cursor IDE, VS Code, Copilot App, Copilot CLI, and ChatGPT desktop are validated at the configuration layer.

MCP

Your MCP servers keep working after you connect a harness to Fireworks. FireConnect changes where model requests go, not which tools the harness loads. Fireworks models call MCP tools the same way the harness’s default models do.

Your servers stay

FireConnect keeps every MCP server you configured, and fireconnect <harness> off leaves them in place.

Tool search stays on

In Claude Code, FireConnect sets ENABLE_TOOL_SEARCH so large MCP tool sets still load on demand.

Web search is built in

The Fireworks WebSearch MCP is retired. Claude Code’s native WebSearch tool replaces it.

What FireConnect changes

Harness	What happens to MCP
Claude Code	Your servers stay in ~/.claude.json. FireConnect removes only its retired fireworks-websearch server and sets ENABLE_TOOL_SEARCH
Codex	Your servers stay in [mcp_servers] in ~/.codex/config.toml
OpenCode	Your servers stay in the mcp block of opencode.json
Codex app	FireConnect doesn’t touch MCP. Set up servers in the app as usual
ChatGPT desktop	Unreliable MCP servers and plugins don’t work reliably while FireConnect is on
Pi, Cursor IDE, VS Code, Copilot App, Copilot CLI, DeepSeek Harness	FireConnect doesn’t touch MCP. Set up servers in the harness as usual
Claude Agent SDK	FireConnect doesn’t touch MCP. MCP follows the setting sources your application loads
Claude Desktop	Not supported FireConnect doesn’t connect Claude Desktop

MCP servers and plugins in ChatGPT desktop don’t work reliably while FireConnect is on. If you depend on them there, run fireconnect codex off before using them.

Check that an MCP tool works

1. Connect the harness

   fireconnect claude
   

   Use fireconnect codex or fireconnect opencode for the other harnesses.

2. Confirm the server is configured

   Claude Code

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

   In Claude Code, add a server with claude mcp add <name> -- <command>.

3. Ask the model to call a tool

   Start a new session and ask for something only the tool can answer, such as “Call the docs search tool and summarize the first result.” The harness shows the tool call, and the answer uses the tool’s output.

Setting up Claude Code by hand? Add "ENABLE_TOOL_SEARCH": "true" to env in ~/.claude/settings.json. Claude Code turns MCP tool search off when ANTHROPIC_BASE_URL points anywhere other than Anthropic.

Upgrading from the Fireworks WebSearch MCP? fireconnect claude removes the fireworks-websearch server for you and leaves your other servers in place. See Web Search for which harnesses have native web search.

Troubleshooting

Nothing changed after --model

Restart or reopen the harness. Claude Code and Codex load a new model in a new or resumed session. See Coding Harnesses for each harness.

FireConnect refuses a FireRouter route

The harness cannot send an Anthropic key. Use a route with only Fireworks models, or use a harness that supports a local Anthropic key.

Microsoft Foundry

FireRouter is not available on Microsoft Foundry, and Foundry support differs by harness. See the compatibility matrix in Foundry for Coding Harnesses, including Claude Code through a gateway.

Related setup

• Coding Harnesses: connect commands, files changed, and restart rules
• FireRouter: router IDs and composition
• Provider Keys: account-level closed-model credentials
• Routing Preferences: quality and savings controls by harness