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Delegate tasks to coding agents (Claude, Codex, Antigravity) from any MCP client
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Delegate tasks to coding agents (Claude, Codex, Antigravity) from any MCP client
Security Report
Valid MCP server (2 strong, 4 medium validity signals). 2 known CVEs in dependencies (1 critical, 0 high severity) Package registry verified. Imported from the Official MCP Registry.
12 files analyzed · 3 issues found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Required
This plugin requests these system permissions. Most are normal for its category.
How to Install
Add this to your MCP configuration file:
{
"mcpServers": {
"io-github-j7an-nexus-mcp": {
"args": [
"--python",
"3.13",
"--with",
"nexus-mcp"
],
"command": "uvx"
}
}
}Documentation
View on GitHubFrom the project's GitHub README.
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.
| Extra | Backend | Adds |
|---|---|---|
claude | Claude Agent SDK | claude-agent-sdk (bundles the Claude Code CLI, ~100 MB) |
codex | Codex App Server | openai-codex (bundles the Codex CLI, ~120–150 MB) |
antigravity | Antigravity SDK | google-antigravity (bundles the Antigravity Go harness, ~40 MB) |
all | every 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.
| Parameter | Default | Meaning |
|---|---|---|
backend | required | claude, codex, or antigravity |
prompt | required | Task for the agent |
cwd | required | Absolute project directory |
profile | read_only | Permission profile (below) |
session_id | — | Continue this conversation |
fork | false | Branch session_id into a new conversation |
model | provider default | Model id or alias |
timeout | 600 | Seconds 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.
| Profile | Allows |
|---|---|
read_only | Read/Glob/Grep; git diff/log/show with --no-ext-diff --no-textconv |
workspace_write | Plus file edits inside cwd and Bash inside the OS sandbox |
full_access | Everything |
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
| Variable | Default | Meaning |
|---|---|---|
NEXUS_CLAUDE_SETTINGS_PROFILE | isolated | Claude settings to load: isolated (none), project (project .claude/), inherit (all, including user settings). Profiles still bound every tool call. |
Migrating from v1
| v1 | v2 |
|---|---|
prompt(cli="codex") (codex exec) | prompt(backend="codex", cwd=…) (App Server) |
prompt(cli=…, execution_mode="yolo") | prompt(backend=…, profile="full_access", cwd=…) |
batch_prompt | Parallel prompt calls from the client |
agent_start / agent_status / agent_result | prompt (synchronous) |
agent_continue / agent_fork | prompt(session_id=…) / prompt(session_id=…, fork=true) |
agent_review | prompt(profile="read_only", prompt="Review …") |
agent_cancel | Cancel the tool call in the client |
agent_respond, elicitation | Removed — choose a profile instead |
| Preferences, model tiers, MCP prompts | Removed |
| OpenCode runners and tools | Removed |
NEXUS_* variables | Removed 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
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