GeneXus MCP Server — GeneXus 18 for Claude, Cursor, and AI Agents

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GeneXus MCP Server lets AI agents — Claude Desktop, Claude Code, Cursor, Antigravity, and any MCP-compatible client — read, edit, analyze, and refactor objects inside a GeneXus 18 Knowledge Base. It talks to the native GeneXus SDK, so the agent works with the *real* KB, not a copy or a parsed approximation.

In practice: you point the MCP at your KB, then ask your AI assistant things like *"list all transactions with attribute CustomerId"*, *"add a rule to the Order transaction that validates the total"*, or *"refactor this procedure to use the new SDT"* — and it does it.

What you can do with it

A quick map of what the agent can do against your real KB through the 49 tools (details in Tool Surface):

It works through the native GeneXus SDK — the same code paths the IDE uses — so edits are real and validated, not text hacks on KB files.

Prerequisites

Before you start, make sure you have:

• ✅ Windows (GeneXus is Windows-only)
• ✅ GeneXus 18 installed locally (default path: `C:\Program Files (x86)\GeneXus\GeneXus18`)
• ✅ A GeneXus 18 Knowledge Base opened at least once in the IDE (so it's initialized)
• ✅ Node.js 18+ — check with `node --version` in a terminal; install from nodejs.org if missing
• ✅ An MCP-compatible AI client — Claude Desktop, Claude Code, Cursor, Antigravity, etc.

You do not need to clone this repo or install anything globally — `npx` handles it.

Never used a terminal before? Press `Win+R`, type `powershell`, hit Enter. That's your terminal.

Quickstart (3 steps, ~5 minutes)

Find your two paths first

Before running the installer, note these down:

1. GeneXus install folder — where `GeneXus.exe` lives. Usually `C:\Program Files (x86)\GeneXus\GeneXus18`.

2. Your KB folder — the root folder of your Knowledge Base (contains the `.gx` file and subfolders like `Model/`, `WebSpa/`).

Not sure where your KB lives? Open it in GeneXus and check the title bar, or look in `File → Recent`.

Step 1 — Run the installer

Open a terminal and run, replacing the paths with your KB folder and your GeneXus install:

npx genexus-mcp@latest init --kb "C:\KBs\YourKB" --gx "C:\Program Files (x86)\GeneXus\GeneXus18"

> Prefer the wizard? Run `npx genexus-mcp@latest init --interactive` and answer the prompts.

What you'll see (takes ~30 seconds first time, faster on re-runs):

1. `npx` downloads the package.

2. The installer verifies the paths exist and GeneXus is present.

3. It auto-detects which AI clients you have installed and adds the MCP config to each one.

4. Prints a JSON snippet at the end — keep it in case you need to configure a client manually.

5. Finishes with `🎉 You are all set!`.

On Windows, Antigravity is registered with the gateway executable bundled in the

current npm package when that artifact is available, so it skips the npx bootstrap

chain on every MCP handshake. That path follows the package in the npx cache; after

an upgrade, run `npx genexus-mcp@latest clients add --clients antigravity` again if

`genexus-mcp clients` reports a stale launcher. Other clients keep the `npx genexus-mcp@latest`

launcher unless you use the fixed-path installer below.

Step 2 — Register the MCP in your AI client

Step 1 auto-registers every supported client it detects, including Claude Desktop, Claude Code, Cursor, Antigravity, Gemini CLI, OpenCode, Codex CLI, and VS Code. If yours wasn't detected, copy the JSON snippet from Step 1 into your client's MCP config manually. See the client setup guide if unsure where that file lives.

Step 3 — Restart your AI client, then test

This part trips most people: fully close your AI client and reopen it. Not just the window — the whole process.

• Claude Desktop: right-click the system-tray icon → Quit. Then launch it again. (Closing the window is not enough.)
• Claude Code: end the session and start a fresh one.
• Cursor / Antigravity: close all windows and reopen.
• OpenCode: fully quit and reopen it so it reloads `opencode.json` / `opencode.jsonc`.
• Gemini CLI / Codex CLI: start a new process or session.

Then paste this prompt:

> *"Using the GeneXus MCP, list the first 5 objects in my KB and show name + type."*

What should happen:

• The AI invokes the `genexus_list_objects` tool (some UIs show "calling tool…").
• A few seconds later, you get a list of objects from your KB.

If you get a list back — you're done. Skip to What can I ask the AI? for ideas.

If the AI says it doesn't have a GeneXus tool, or nothing happens, go to Troubleshooting — most issues are covered there.

🤖 Let your AI install it for you

If you'd rather not run anything in the terminal yourself, paste this into your AI chat:

> Please configure the GeneXus MCP server. Run `npx genexus-mcp@latest init --kb "" --gx ""` in the terminal. If I haven't told you my GeneXus path and KB path yet, ask me first. Once it succeeds, read the JSON block it printed and add it to my MCP client config. Tell me when I should restart the client to start using GeneXus tools.

Replace the placeholders or let the AI ask you for them.

Corporate install (fixed path, ASR-friendly)

If your machine has Microsoft Defender ASR, SmartScreen, or another endpoint policy blocking unsigned binaries, the default `npx` flow is painful — `npx` caches the package under `%LOCALAPPDATA%\npm-cache\_npx\\...`, and the `` changes per version, so IT can't whitelist a stable path without a wildcard over the whole npm cache (which is too broad).

Use the corporate installer instead. It extracts the binaries to a stable directory and registers the AI clients to launch the gateway directly from there — `npx` is never on the runtime path.

# One-liner — installs latest release, registers AI clients
iex (irm https://raw.githubusercontent.com/lennix1337/Genexus18MCP/main/scripts/install.ps1)

# With explicit KB and GeneXus paths
$s = irm https://raw.githubusercontent.com/lennix1337/Genexus18MCP/main/scripts/install.ps1
& ([scriptblock]::Create($s)) -Kb "C:\KBs\MyKB" -Gx "C:\Program Files (x86)\GeneXus\GeneXus18"

Install location:

• Admin shell → `C:\Tools\GenexusMCP\`
• Non-admin shell → `%LOCALAPPDATA%\Programs\GenexusMCP\`

Paths to give to IT for the ASR / Defender exclusion list:

\GxMcp.Gateway.exe
\worker\GxMcp.Worker.exe

Re-run the same one-liner later to upgrade — it detects the installed version (`version.txt` in the install dir) and downloads only if a newer release is available. Use `-Force` to reinstall the same version, `-Version v2.3.0` to pin a specific tag, `-NoClient` to skip AI client registration. Node.js 18+ must be installed for client registration; without it the script still extracts the binaries but you'll need to edit the client config (`claude_desktop_config.json` etc.) manually.

What can I ask the AI?

Once installed, here's what unlocks. Try these as your first prompts:

Exploration

• *"List all objects of type Procedure in the KB."*
• *"Show me the source of the procedure CalculateInvoiceTotal."*
• *"Find all transactions that reference the attribute CustomerId."*

Editing

• *"Add a rule to the Order transaction: error('Total must be positive') if Total Multi-KB (v2.3.0+): every non-meta tool takes an optional `kb` argument (alias or absolute path). The gateway can hold up to `Server.MaxOpenKbs` (default 3) KBs open at once, each in its own Worker process — calls to different KBs run truly in parallel. See Advanced Configuration for the `KBs[]` schema.

WorkWithPlus & theming (via `genexus_read` / `genexus_edit`)

• Full read/write of `PatternInstance` / `PatternVirtual` XML: containers (``, groups), controls (``, ``, ``, ``, ``), actions (``, ``), grids, orders, rules, event blocks. Transaction and Selection views are addressable independently.
• `Documentation` (markdown) and `Help` (HTML) are first-class write targets.
• Apply real ThemeClass values (`themeClass`, `buttonClass`, `groupThemeClass`, …); discover them with `genexus_list_objects --typeFilter ThemeClass`.

Edit modes (`genexus_edit`): `full` (whole-part replacement, default), `patch` (Replace/Insert_After/Append over a context anchor — works on source code AND pattern XML), `ops` (typed semantic ops like `set_attribute`, `add_rule` for source-bearing parts).

Pattern XML auto-reconcile: WorkWithPlus encodes IDE rendering order in a per-parent `childrenOrderedList` attribute. The MCP now rebuilds (and creates if missing) every list from the actual XML child order on each write — callers only describe *where* an element goes in the tree and the MCP makes the IDE render it there. The response includes a `childrenOrderedListReconciliation` block listing each (re)written parent plus any structural elements that couldn't be inferred safely.

Safe by default: all write tools accept `dryRun: true` (returns a preview without mutating the KB) and `idempotencyKey` (safe retries; concurrent calls coalesce, results cached 15 min).

WorkWithPlus pattern editing — what you can actually do

WorkWithPlus patterns are XML documents that drive Transaction-and-Selection screens. The MCP exposes the entire surface so an agent can design or restructure a screen without opening the IDE:

Recommended workflow for a screen redesign:

1. `genexus_list_objects --typeFilter ThemeClass --nameFilter Button` — discover the actual button classes available in this KB (`ButtonGreen`, `ButtonBlue`, `ButtonRed`, etc — names vary per KB).

2. `genexus_read --name WorkWithPlus --part PatternInstance` — get the current XML.

3. Edit the XML in memory (LLM): wrap attributes in a ``, reorder buttons, add a new ``, attach `buttonClass="btn ButtonGreen"`, etc.

4. `genexus_edit --mode full --part PatternInstance --content ""` — the MCP rewrites the part, reconciles `childrenOrderedList` on every container, and verifies the round-trip.

5. Read back to confirm; refresh the GeneXus IDE to see the result.

Custom buttons use ``, not ``. `Trn_Enter` / `Trn_Cancel` / `Trn_Delete` are the only registered standard actions on a WorkWithPlus transaction; any custom button (Duplicate, Audit, Export, etc.) must be a ``. The MCP's reconciler treats `` as a peer of `` (same typeCode 17/18 by context), so they coexist in the same `TableActions` row and the IDE renders them side-by-side.

Things to know (orientation, not gotchas):

• WorkWithPlus normalizes some attributes after every save. Certain fields are bound to the underlying transaction (e.g., `title` on top-level groups derives from the transaction's friendly name). When `"Apply this pattern on save"` is enabled on the WorkWithPlus object, the engine recomputes those fields — same behavior whether you edit in the IDE or via MCP. To make a hard override stick, toggle that flag via MCP:

{ "tool": "genexus_properties",
    "arguments": { "action": "set", "name": "WorkWithPlus",
                   "propertyName": "SDPlus_Editor_Apply_On_Save", "value": "False" } }

Accepts `"True" | "False" | "Default"` (Default inherits the KB-level setting). Set back to `"Default"` to re-enable engine recomputation. Validated live in this repo.

• Structural safety is enforced by the SDK. If you submit XML that violates pattern invariants (e.g., a `` without a ``, or a `` whose `name` isn't a registered action), the SDK rejects the save and the MCP returns the exact error so you can fix the input. The KB never ends up half-written.
• The IDE Pattern preview is a structural mockup, not a styled render. Theme CSS (`buttonClass`, `themeClass`, fonts, colors) is resolved at runtime, not in the preview canvas — so even after a successful MCP write the preview pane will look generic. To verify styling: open the element in the IDE tree and check the right-hand Properties panel (the applied classes show there), or hit Run / Live Editing to see the real CSS. This is GeneXus IDE behavior, independent of how the pattern was edited.

AXI CLI (for agents and automation)

The `genexus-mcp` command itself is also an agent-facing CLI with token-optimized output:

genexus-mcp status               # gateway/worker state
genexus-mcp doctor --mcp-smoke   # health check + protocol probe
genexus-mcp tools list           # list available tools
genexus-mcp config show          # current resolved config
genexus-mcp layout status        # native layout automation state

Global flags: `--format toon|json|text` · `--fields f1,f2,...` · `--limit N` · `--query ` · `--quiet` · `--no-color`.

Full contract: `docs/axi_cli_contract.md`. Best-practices playbook: `docs/llm_cli_mcp_playbook.md`.

Advanced Configuration

The installer writes a `config.json` for you. To customize networking, timeouts, or shadow paths:

{
  "Server": {
    "HttpPort": 5000,
    "BindAddress": "127.0.0.1",
    "SessionIdleTimeoutMinutes": 10,
    "WorkerIdleTimeoutMinutes": 5,
    "MaxOpenKbs": 3
  },
  "GeneXus": {
    "InstallationPath": "C:\\Program Files (x86)\\GeneXus\\GeneXus18",
    "WorkerExecutable": "worker\\GxMcp.Worker.exe"
  },
  "Environment": {
    "DefaultKb": "main",
    "KBs": [
      { "alias": "main",   "path": "C:\\KBs\\YourKB" },
      { "alias": "legacy", "path": "C:\\KBs\\OtherKB" }
    ]
  }
}

> Backward compatibility: old configs with a single `Environment.KBPath` keep working — the gateway auto-migrates them to `KBs[]` + `DefaultKb` at load time.

Working with multiple KBs

Once you declare more than one KB in `Environment.KBs[]`, every tool accepts an optional `kb` argument:

// LLM example: list procedures in two KBs in parallel
{ "tool": "genexus_list_objects", "arguments": { "kb": "main",   "type": "Procedure" } }
{ "tool": "genexus_list_objects", "arguments": { "kb": "legacy", "type": "Transaction" } }

Resolution rules when `kb` is omitted:

• an explicit `kb` always wins; use it for parallel work or when a prompt touches more than one KB
• each MCP session snapshots the configured `DefaultKb` at `initialize`; `set_default` changes the current session and persists the startup fallback for future sessions
• `open` only starts/registers a Worker; it does not silently change another session's target. Select it with `set_default`, or pass `kb` explicitly
• exactly 1 KB open → uses that KB when the session has no selection
• 2+ KBs open with no session selection → server returns `KB_AMBIGUOUS`; choose one with `set_default` or pass `kb` explicitly

Manage the pool at runtime:

{ "tool": "genexus_kb", "arguments": { "action": "list" } }
// → { selectedKb, activeKb, openKbs: [{alias, path, pid, workingSetMB, idleSeconds}], knownKbs, maxOpenKbs, defaultKb, declaredKbs }

{ "tool": "genexus_kb", "arguments": { "action": "open", "alias": "adhoc", "path": "C:/KBs/ScratchKB" } }
{ "tool": "genexus_kb", "arguments": { "action": "close", "alias": "legacy" } }
{ "tool": "genexus_kb", "arguments": { "action": "set_default", "alias": "main" } }   // persists to config.json

For OpenCode, call `genexus_whoami` once at the start of a session. Use

`kb.selected`, `kb.default`, `kb.openKbs`, `kb.knownKbs`, and `kb.declaredKbs`

to understand the target, then select the normal working KB with

`genexus_kb action=set_default`. Every KB-bound response also includes `kbAlias`

in its JSON payload, which lets OpenCode correlate text-only responses. Keep

`kb=` on calls that intentionally compare or update another KB.

The installer registers both OpenCode configuration layouts: the legacy direct

`mcp.genexus` entry used by OpenCode 1.x and the current `mcp.servers.genexus`

layout. `clients add --clients opencode` is only needed to repair or explicitly

re-register a client after installation; normal `init` handles detected clients

automatically. Restart OpenCode after a registration so it reloads the MCP

configuration.

When the pool is full and no Worker is idle, the server returns `KB_POOL_FULL` — close one explicitly or raise `Server.MaxOpenKbs`. Each Worker carries the SDK in its own process (~200–400 MB idle, up to 1–2 GB on heavy KBs), so size the pool against available RAM.

Architecture

graph LR
    A[AI Client / Nexus-IDE] -->|MCP stdio or HTTP /mcp| B[Gateway .NET 8]
    B -->|JSON-RPC over process boundary| C[Worker .NET Framework 4.8]
    C -->|Native SDK| D[GeneXus KB]

• Worker pool (v2.3.0+): one .NET 4.8 Worker process per open KB, capped by `MaxOpenKbs` (default 3). Workers are spawned lazily, recycled by `WorkerIdleTimeoutMinutes`, and evicted LRU when the pool is full.
• Cross-KB parallelism: tool calls to different KBs run on different Worker processes and never block each other. Calls to the same KB are still serialized by the GeneXus SDK's STA requirement.
• Gateway reuse: multiple IDE instances share one gateway via lease files at `%LOCALAPPDATA%\GenexusMCP\gateway-leases`.
• HTTP mode: also available at `http://127.0.0.1:5000/mcp` with SSE. Header: `MCP-Protocol-Version: 2025-11-25`.

Development & building from source

Want to contribute or run a local dev build?

1. Clone this repo on Windows.

2. Run `.\setup.bat` — checks prerequisites, builds the C# components, and auto-registers the local build with detected AI clients.

3. If GeneXus or your KB aren't auto-detected, follow the prompts.

Bundled AI skills (`.gemini/skills/`)

This repo ships a set of agent skills under `.gemini/skills/` that any MCP-compatible client with skill support (Gemini CLI, Claude Code via plugin, etc.) can load to ground its GeneXus reasoning:

Third-party skills are Apache 2.0 (see `.gemini/skills/NOTICE.md`). To refresh against upstream, follow the steps in `NOTICE.md`.

Nexus-IDE (VS Code extension — optional, not auto-installed)

`src/nexus-ide` is a lightweight, experimental VS Code extension in the repo. The installer no longer packages or installs it — VS Code is wired up as a native MCP client instead (see Supported AI clients). If you want the extension, build and install it manually:

cd src/nexus-ide; npm ci; npm run compile
npx --yes @vscode/vsce package --out nexus-ide.vsix
code --install-extension nexus-ide.vsix --force

It provides a virtual filesystem (`genexus://` scheme), a KB explorer with multi-part editing, and MCP discovery commands.

Automated release

• Workflow: `.github/workflows/release.yml`
• Trigger: push to `main` with a `package.json` version bump
• Behavior: publishes to npm if version is new + creates a GitHub Release tagged `v`
• Required secret: `NPM_TOKEN`

License

MIT — see LICENSE.

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