@h0wzy/mcp Server Antigravity

🚀 H0wZy/mcp — The Ultimate Multi-Agent MCP Hub & Go CLI

Centralize, enhance, and distribute high-performance MCP (Model Context Protocol) servers connecting the world's leading AI developer CLIs:

• Claude Code (Anthropic)
• OpenAI Codex CLI (GPT-6 family, default GPT-6-Astra)
• Google Antigravity (Gemini, default Gemini 3.8 Flash)

Cross-model code reviews, independent second opinions, and autonomous multi-agent validation — configured effortlessly via an interactive Golang TUI CLI and distributed via standalone binaries and npx @h0wzy/mcp.

🏷️ #mcp #ai-agents #multi-agent #antigravity #claude-code #openai-codex #gemini #cli #go #bubbletea #tui #developer-tools #model-context-protocol

🏛️ Interactive Architecture Diagram

Explore the full interactive system architecture with Light/Dark themes and semantic tracing: 👉 View Interactive Architecture Diagram

🌟 Why H0wZy/mcp?

1. DRY Shared Core (@h0wzy/mcp-shared):
   • Eliminates matrix code duplication across host agents. A single createMcpServer() engine manages 100% of JSON-RPC 2.0 stdio protocol handling, error catching, and lifecycle handshakes.
2. Native Cross-Platform (Zero Windows Glitches):
   • Eliminates POSIX-only bugs like PATH.split(':') by utilizing native path delimiters (; on Windows, : on POSIX).
   • Resolves executable extensions automatically (.exe, .cmd, .bat from PATHEXT), finding agy.exe and codex.cmd without requiring manual environment path overrides.
3. Instant Performance (Zero npx Latency):
   • Directly executes local binaries with sub-50ms invocation overhead, removing runtime npx network/cache-checking delays.
4. Resilient Rate Limits & Quotas:
   • Gracefully traps HTTP 429 and ResourceExhausted provider quota limits, returning structured { isError: true } responses so host agents fall back seamlessly without crashing the session.
5. Interactive Go CLI (hmcp / h0wzy-mcp):
   • Auto-detects local CLI installations (claude, codex, agy), tests binary health, checks for updates, and guides the user through an interactive checklist to configure MCP connections globally or per-project.

📁 Repository Layout

H0wZy/mcp/
├── .github/workflows/          # CI/CD pipelines & cross-platform testing
├── cli/                        # Interactive CLI in Go (Bubble Tea / Lip Gloss)
│   ├── cmd/                    # Commands: doctor, install, list, remove, setup-path, upgrade, version
│   ├── config/                 # Read/write ~/.claude.json, config.toml, and mcp_config.json
│   ├── detector/               # Discovers local claude, codex, and agy CLIs + health checks
│   ├── ui/                     # Terminal user interface, lilac ASCII banner, and interactive TUI
│   └── version/                # Background update detector & registry version cache
├── servers/                    # Decoupled, host-agnostic MCP servers
│   ├── antigravity/            # Google Antigravity bridge (Gemini, default 3.8 Flash)
│   ├── claude/                 # Claude Code bridge (default opus), so Codex/Antigravity can call Claude
│   └── codex/                  # OpenAI Codex CLI bridge (GPT-6, default Astra)
├── shared/                     # Reusable core (@h0wzy/mcp-shared)
│   ├── server.js               # createMcpServer() generic JSON-RPC 2.0 stdio engine
│   ├── chain-guard.js          # Loop guard: depth, cycles, call budget, deadline (spec 006)
│   ├── ancestry.js · l1.js     # Nesting fallback via process ancestry · start agents without bridge tools
│   ├── configure-tool.js       # The configure_<agent> tool shared by every bridge
│   ├── executor.js             # Child process runner: timeouts, tree kill, cancel, output cap
│   ├── validate.js             # cwd / paths / timeout validation for agent command lines
│   ├── agent-config.js         # Model & reasoning-effort catalogs, tiers and ceilings
│   ├── resolver.js             # Cross-platform executable resolver
│   └── errors.js               # Resilient Quota, HTTP 429 handler & secret/token sanitizer
├── npm/                        # Lightweight npx runner wrapper & cross-platform binary installer
├── specs/                      # SpecKit feature specs & Archify diagrams
├── test/                       # Node.js integration & security resilience tests
├── SECURITY_AUDIT.md           # Security audit, credential double-check & hardening report
├── LICENSE                     # MIT License
└── package.json                # Monorepo workspaces configuration

🚀 Quick Start

1. Interactive Setup (Recommended)

Choose your preferred way to run H0wZy/mcp:

# 1. Instant execution via npx (Zero setup):
npx @h0wzy/mcp

# 2. Or install globally via npm (provides 'hmcp', 'hwzmcp', and 'h0wzy-mcp'):
npm install -g @h0wzy/mcp
hmcp

# 3. Or directly from source with Go:
go run ./cli setup-path
hmcp

📦 Precompiled Standalone Binaries (v1.0.7)

Download zero-dependency native binaries directly from Releases:

• 🪟 Windows (amd64): h0wzy-mcp-windows-amd64.exe
• 🐧 Linux (amd64): h0wzy-mcp-linux-amd64
• 🍏 macOS Apple Silicon (arm64): h0wzy-mcp-darwin-arm64
• 🍏 macOS Intel (amd64): h0wzy-mcp-darwin-amd64

The CLI will scan your system:

🚀 H0wZy/mcp — Multi-Agent MCP Hub Setup
Scanning local AI developer CLIs...
  ✓ Claude Code (C:\Users\...\claude.exe)
  ✓ OpenAI Codex CLI (C:\Users\...\codex.cmd)
  ✓ Google Antigravity (C:\Users\...\agy.exe)

? Select MCP bridges to configure:
  [x] Claude Code -> Google Antigravity (Gemini)
  [x] Claude Code -> OpenAI Codex (GPT-6)
  [ ] OpenAI Codex -> Google Antigravity (Gemini)

? Configuration Scope: User (Global across all projects)
? Apply configuration now? Yes

✅ All selected bridges configured successfully!

2. Commands & Management

# Launch interactive TUI setup and configuration
hmcp

# Check version and verify if updates are available
hmcp version

# Upgrade hmcp to latest release (or 'hmcp update')
hmcp upgrade

# Windows, upgrading FROM v1.0.6 or older: those versions can't replace the running
# hmcp.exe, yet still print "Successfully upgraded". Upgrade through another alias,
# then check with 'hmcp version':
h0wzy-mcp upgrade --force

# Setup PATH and shims (~/.local/bin) so 'hmcp', 'hwzmcp', and 'h0wzy-mcp' work everywhere
hmcp setup-path

# Diagnose local environment, paths, and agent communication health
hmcp doctor

# Diagnose and output as JSON ({ tools, bridges, cycles, guard })
hmcp doctor --json

# Install all supported integrations automatically (asks before creating cycles;
# non-interactive runs skip cycle-forming directions unless --allow-cycles is given)
hmcp install --all
hmcp install --all --allow-cycles

# Install a specific bridge globally or locally
hmcp install claude-antigravity --scope user
hmcp install claude-codex --scope project
hmcp install codex-claude          # Codex → Claude Code
hmcp install antigravity-claude    # Antigravity → Claude Code

# List available bridges
hmcp list

# Remove an integration
hmcp remove claude-antigravity

🔌 Available MCP Tools (Symmetrical Parity)

🎛️ Dynamic Model & Reasoning Effort Control

Claude Code can now autonomously (or on request) escalate or de-escalate reasoning power according to task complexity:

Every task execution appends a standardized verification footer confirming the active settings: [codex · model=gpt-6-astra · effort=high · source=tier:deep]

Developer Ceilings & Environment Overrides

To keep resource and quota consumption under strict developer control, set optional ceilings in your client's environment:

• AGY_MAX_EFFORT / CODEX_MAX_EFFORT: Clamps reasoning effort to a maximum level (e.g. medium).
• AGY_MAX_TIER / CODEX_MAX_TIER: Clamps autonomous model escalation to a maximum tier (e.g. balanced).
• AGY_TIER_LIGHT / CODEX_TIER_DEEP: Override default tier mappings using model[:effort] syntax (e.g. gpt-6-sol:high).
• Claude Code bridge: the same settings with the CLAUDE_BRIDGE_ prefix (CLAUDE_BRIDGE_MODEL, CLAUDE_BRIDGE_MAX_TIER, …), plus CLAUDE_BRIDGE_MAX_TURNS and CLAUDE_BRIDGE_MAX_BUDGET_USD caps per call. The prefix is not CLAUDE_, because Claude Code exports CLAUDE_EFFORT and other CLAUDE_* variables to its children.

Delegation tools write to disk. delegate_codex and delegate_antigravity run the agent inside the given cwd and may create or modify files. They never commit for you: always review the resulting diff (git diff) before keeping the changes.

Startup defaults: Antigravity tools default to Gemini 3.8 Flash (High) (override with AGY_MODEL / AGY_EFFORT). Codex tools default to gpt-6-astra at medium effort (override with CODEX_MODEL / CODEX_EFFORT). Codex's read-only tools run in Codex's read-only sandbox, and Antigravity's run without auto-approval, so actions that need approval are skipped; only the delegate_* tools can write.

🛡️ Loop Guard (agents calling agents)

With bridges in every direction, Codex can ask Antigravity, which asks Claude, which asks Codex… Every bridge runs the same guard before it starts an agent:

• Each top-level call starts its own chain. The chain context travels to child agents in H0WZY_MCP_* variables. When a host strips them (Codex forwards only allow-listed variables), the bridge still finds its chain through a registry of running bridge-started agents (~/.h0wzy-mcp/) and its process ancestry. If it can't tell, it refuses.
• No bridge tools at the maximum depth. An agent started there gets no bridge tools where its CLI allows it (Claude Code --strict-mcp-config, Codex mcp_servers.<name>.enabled=false), and its prompt opens with its position in the chain.
• Refusals start nothing. They come back as ⛔ [Loop guard: …] errors that tell the calling agent to finish the work itself. Every reply ends with a trace line such as [chain claude→codex · depth 1/2 · calls 1/8 · run a1b2c3d4].
• H0WZY_MCP_CHAIN_LOG=1 keeps a JSON Lines log at ~/.h0wzy-mcp/chain.log (run id, agents, depth, outcome, duration; never prompt text).
• hmcp doctor lists every installed direction, the cycles they form, and the active limits.

What an agent started by a bridge loads

A nested agent gets the mesh bridges (codex, antigravity, claude) and none of your other MCP servers. Measured on a real setup (11 MCP servers plus the claude.ai connectors in Claude Code, 11 servers in Codex):

• Claude Code runs with --strict-mcp-config plus a temporary --mcp-config that lists only the bridges registered in your user config (~/.claude.json, user and local scope). A project's .mcp.json is never passed on, because Claude Code asks you before it starts those servers.
• Codex runs with -c mcp_servers.<name>.enabled=false for every server that isn't a bridge.
• Antigravity has no per-call switch, so it always loads every server in ~/.gemini/config/mcp_config.json, and it waits until all of them have connected before it starts. If an Antigravity call returns ⏱️ Antigravity did not finish… and names a server it was waiting for, bring that server back online or remove it (agy mcp remove <name>); agy mcp disable was not enough in agy 1.3.1.
  • ⚠️ Antigravity can call those servers' tools without asking. In agy 1.3.1 an MCP tool runs without a permission prompt in every mode the bridge uses (read-only ask_* / review_* / …, and delegate_antigravity), and a custom --agent with a tools list does not restrict it. If your agy config has servers that publish, spend credits or drive other apps (a shop, a video generator, Blender, Unity…), any Antigravity bridge call or agy teammate can reach them. Keep such servers out of agy's config, or don't install the Antigravity bridge on that machine.
  • If agy rejects one MCP tool's schema, every call fails at once; the bridge's error names the tool. agy mcp disable <server> fixes that case.
• Read-only calls never reach the bridges' editing tools: nested Claude Code gets --disallowedTools for delegate_* / configure_*, nested Codex gets them in disabled_tools, whatever permission mode your own settings give the nested run.
• H0WZY_MCP_USER_SERVERS=1 lets nested Claude Code and Codex load your own servers again. At the maximum depth they still get none.

👥 Agent Teams across vendors (spec 007)

@h0wzy/mcp-server-team lets any of the three agents lead a team whose teammates are any mix of Claude Code, Codex and Antigravity. It works like Claude Code's Agent Teams, but across vendors:

hmcp install team   # team server in every detected CLI + the agent-team skill where each one finds skills

Then, in your usual interactive session:

• Background teammates: team_spawn returns at once. Each teammate has a role, a vendor and a tier, and is read-only unless spawned with can_edit. Editing teammates work in their own git worktree.
• Shared task list: tasks have dependencies, and claims are atomic. Teammates claim the next task themselves, and the orchestrator owns every status change.
• Messages: teammates message each other or the lead by name, and an idle teammate wakes for one turn.
• team_wait: returns as soon as something happens, with compact results capped at 8,000 chars. Full outputs are read on demand with team_result, which keeps the lead's own token use low.
• Hard limits: 3 teammates, 10 turns each, 30 in total, 60 min (H0WZY_TEAM_*). Every turn goes through the loop guard, and teammates can't start teams of their own.
• Lean teammates: like any agent a bridge starts, Claude Code and Codex teammates load only the mesh bridges, not your other MCP servers (see above).

See servers/team/README.md for every tool and setting.

🗂️ Your own MCP servers (spec 008)

hmcp registry keeps one list of the MCP servers you build or run, and writes each into Claude Code (user scope), Codex and Antigravity. Move a server once, and every agent follows:

hmcp registry add my-server --url http://<host>:<port>/my-server/mcp
hmcp registry add my-local-server --env MY_TOKEN -- node <path>/server.js --stdio
hmcp registry update my-local-server -- node <new path>/server.js --stdio   # every client follows
hmcp registry status                       # in sync / differs / missing, and whether URLs answer
hmcp registry apply [name…] [--codex-project] [--replace]
hmcp registry list | remove <name>

• Private by design: the registry lives in ~/.h0wzy-mcp/registry.json (or $H0WZY_MCP_REGISTRY), never in a repository. It holds names, targets and env var names, never secret values.
• Only what it manages: hmcp touches only the client entries it wrote or adopted. A hand-made entry with the same target is adopted, and one that points elsewhere is reported as a conflict until you pass --replace. Other keys you add to an entry (env, headers, …) are kept.
• --clients claude,codex keeps a server out of Antigravity, which calls its MCP tools without asking. --no-apply changes the registry only.
• Agents started by a bridge don't load these servers unless H0WZY_MCP_USER_SERVERS=1 (see above).

🔒 Security & Privacy

H0wZy/mcp is built with privacy and execution safety as first-class guarantees:

• Automatic Token Redaction: Built-in regex sanitizers proactively scrub OpenAI keys, Google Gemini keys, GitHub/NPM tokens, and Bearer authorization headers before errors or diagnostic messages reach host agents.
• Owner-Only File Permissions: Configuration files (.claude.json, .codex/config.toml, .gemini/config/mcp_config.json) are secured with POSIX mode 0600 (0700 for directories) on Unix systems to prevent unauthorized local reading.
• Atomic Precompiled Downloads: The npm binary installer streams release archives to unique temporary files and validates payloads before atomic renames, preventing corrupt or truncated executables.

For full audit methodology and double-check verification, read the Security Audit & Codebase Integrity Report.

🧪 Testing

# Run all Node.js MCP server & resilience tests
npm test

# Run all Go CLI detector & config tests
go test -v ./cli/...

📄 License & Acknowledgements

Created and architected by Marcos (H0wZy) under the MIT License.

This project unifies and enhances foundational work from the open-source MCP community:

• antigravity-claude-mcp by Arjun Thilak (MIT License)
• codex-mcp-tool by Taras Trishchuk (MIT License)