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io.github.j7an/nexus-mcp

Official registry Developer tools

Delegate tasks to coding agents (Claude, Codex, Antigravity) from any MCP client

Source code Documentation

Install

Add this to your client's MCP configuration (Claude Desktop: claude_desktop_config.json; Cursor: .cursor/mcp.json; VS Code and others use the same "mcpServers" shape).

PYPI package nexus-mcp
Claude Code 
claude mcp add nexus-mcp -- uvx nexus-mcp==2.1.3
JSON configuration (Claude Desktop, Cursor, VS Code) 
{
    "mcpServers": {
        "nexus-mcp": {
            "command": "uvx",
            "args": [
                "nexus-mcp==2.1.3"
            ]
        }
    }
}

Documentation

From the project's README on GitHub, refreshed weekly. Links open on GitHub.

Contents
  1. nexus-mcp
  2. Install
  3. Tool: prompt
  4. Resource: nexus://backends
  5. Configuration
  6. Migrating from v1
  7. Development
  8. License

nexus-mcp

MCP server that delegates tasks to coding agents — Claude Code via the Claude Agent SDK, Codex via the Codex App Server, and Antigravity via the Antigravity SDK — from any MCP client.

Install

Backends are optional extras; install the ones you use.

ExtraBackendAdds
claudeClaude Agent SDKclaude-agent-sdk (bundles the Claude Code CLI, ~100 MB)
codexCodex App Serveropenai-codex (bundles the Codex CLI, ~120–150 MB)
antigravityAntigravity SDKgoogle-antigravity (bundles the Antigravity Go harness, ~40 MB)
allevery backend
uvx --with 'nexus-mcp[all]' nexus-mcp          # run directly
pip install 'nexus-mcp[claude]'                 # or install
pip install 'nexus-mcp[codex]'                  # Codex only
pip install 'nexus-mcp[antigravity]'

Claude Code MCP config:

{ "mcpServers": { "nexus": { "command": "uvx", "args": ["--with", "nexus-mcp[all]", "nexus-mcp"] } } }

Authentication is the agent's own: log in with claude, or set ANTHROPIC_API_KEY; for Codex, log in with codex login (credentials in ~/.codex are shared). Antigravity uses GEMINI_API_KEY, or Vertex AI with GOOGLE_GENAI_USE_VERTEXAI, GOOGLE_CLOUD_PROJECT, and GOOGLE_CLOUD_LOCATION, authenticated through Application Default Credentials (ADC). It does not use Google-account login.

Windows: recent claude-agent-sdk releases ship no Windows wheel with a bundled CLI; install Claude Code so claude is on PATH.

Tool: prompt

Runs one agent turn and returns its final answer.

ParameterDefaultMeaning
backendrequiredclaude, codex, or antigravity
promptrequiredTask for the agent
cwdrequiredAbsolute project directory
profileread_onlyPermission profile (below)
session_id—Continue this conversation
forkfalseBranch session_id into a new conversation
modelprovider defaultModel id or alias
timeout600Seconds before the turn is cancelled

Returns {backend, session_id, output, usage}. Conversations are stored by the agent itself (~/.claude/projects, $CODEX_HOME/sessions, ~/.nexus-mcp/antigravity), so a session_id keeps working after nexus-mcp restarts. Antigravity does not support fork=true.

Permission profiles

Actions outside the chosen profile are denied automatically — nobody is prompted.

ProfileAllows
read_onlyRead/Glob/Grep; git diff/log/show with --no-ext-diff --no-textconv
workspace_writePlus file edits inside cwd and Bash inside the OS sandbox
full_accessEverything

Codex enforces profiles with its OS sandbox (read-only, workspace-write, danger-full-access) and never asks for approval.

Antigravity enforces workspace containment in its harness and uses the OS sandbox for commands. workspace_write fails if that sandbox is unavailable.

Resource: nexus://backends

JSON list of {name, installed, models, hint}; hint gives the install command for a missing extra. Codex lists its models; Claude and Antigravity report null (Antigravity does not provide a model list).

Configuration

VariableDefaultMeaning
NEXUS_CLAUDE_SETTINGS_PROFILEisolatedClaude settings to load: isolated (none), project (project .claude/), inherit (all, including user settings). Profiles still bound every tool call.

Migrating from v1

v1v2
prompt(cli="codex") (codex exec)prompt(backend="codex", cwd=…) (App Server)
prompt(cli=…, execution_mode="yolo")prompt(backend=…, profile="full_access", cwd=…)
batch_promptParallel prompt calls from the client
agent_start / agent_status / agent_resultprompt (synchronous)
agent_continue / agent_forkprompt(session_id=…) / prompt(session_id=…, fork=true)
agent_reviewprompt(profile="read_only", prompt="Review …")
agent_cancelCancel the tool call in the client
agent_respond, elicitationRemoved — choose a profile instead
Preferences, model tiers, MCP promptsRemoved
OpenCode runners and toolsRemoved
NEXUS_* variablesRemoved except NEXUS_CLAUDE_SETTINGS_PROFILE

Development

uv sync --all-extras --all-groups
uv run pytest                    # unit + e2e
uv run pytest -m integration     # real CLI (slow, makes model calls)
uv run mypy src/nexus_mcp && uv run ruff check . && uv run ruff format --check .

License

MIT

Frequently asked questions

What is io.github.j7an/nexus-mcp?

Delegate tasks to coding agents (Claude, Codex, Antigravity) from any MCP client

How do I install io.github.j7an/nexus-mcp?

It runs on your machine. In Claude Code: claude mcp add nexus-mcp -- uvx nexus-mcp==2.1.3. For other clients, paste the JSON configuration from this page into their MCP settings.

Does io.github.j7an/nexus-mcp need an API key?

Its registry entry lists no required key or secret. Some features may still need an account with the service it connects to.

Is io.github.j7an/nexus-mcp open source?

Yes. Its code is on GitHub under the MIT license.

Who maintains io.github.j7an/nexus-mcp?

It is published by j7an. AI.tn lists it but does not maintain or endorse it.

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