Add support for Model Context Protocol by martin-fleck-at · Pull Request #271 · eclipse-glsp/glsp-theia-integration

martin-fleck-at · 2025-12-18T19:34:38Z

What it does

Registers GLSP-announced MCP servers with the IDE's MCP frontend
service so the agent can use them immediately after IDE startup.

MCP integration

Discovers MCP server descriptors on each GLSP client contribution
and adds them to the IDE's MCP host on startup.
Triggers an explicit start since the host's autostart hook only
fires at frontend init.
Per-registration cleanup releases server entries and state-change
subscriptions on GLSP failure or extension dispose, avoiding
stale entries across IDE restarts under random-port defaults.

Adopters

Set the configuration on the GLSP client contribution to enable
MCP for a diagram language.
The workflow example demonstrates the end-to-end wiring with a
transient connect notification and a copy-URL action.

Misc

Sends a shutdown notification before the GLSP connection drops
so the server tears down cleanly with the parent session.

Part of eclipse-glsp/glsp#1546
Requires eclipse-glsp/glsp-client#456 and eclipse-glsp/glsp-server-node#120

How to test

Nothing should break in the default case
To use the new mcp server, you need to use a GLSP server that supports it, i.e., the GLSP Node Server
Startup the Workflow example
Check the AI Configuration > MCP Server view that should show the GLSP MCP server correctly and allow you to connect to it and show all tools. Please note that there is no support for MCP resources in Theia yet.

Follow-ups

Changelog

This PR should be mentioned in the changelog
This PR introduces a breaking change (if yes, provide more details below for the changelog and the migration guide)

Copilot

Pull request overview

This PR adds support for the Model Context Protocol (MCP) by integrating GLSP MCP servers with Theia AI. The changes enable GLSP diagram editors to expose their functionality through MCP servers that can be discovered and utilized by Theia's AI features.

Key changes:

New theia-mcp-integration package that automatically registers GLSP MCP servers with Theia's AI MCP service
Fixed shutdown notification handling to properly notify servers before connection disposal
Updated workflow example to demonstrate MCP server initialization

Reviewed changes

Copilot reviewed 12 out of 14 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/theia-mcp-integration/package.json	Defines new package for MCP integration with dependencies on Theia AI and GLSP integration
packages/theia-mcp-integration/tsconfig.json	TypeScript configuration for the new MCP integration package
packages/theia-mcp-integration/src/browser/theia-mcp-integration-frontend-module.ts	Container module that registers the MCP registration service
packages/theia-mcp-integration/src/browser/glsp-mcp-registration.ts	Service that discovers GLSP clients and registers their MCP servers with Theia
packages/theia-integration/src/browser/glsp-client-contribution.ts	Fixed to send shutdown notification before disposing connection
examples/workflow-theia/src/browser/workflow-glsp-client-contribution.ts	Updated to include MCP server initialization parameters
examples/workflow-theia/package.json	Added dependency on new theia-mcp-integration package
examples/workflow-theia/tsconfig.json	Added TypeScript project reference to theia-mcp-integration
examples/browser-app/package.json	Added Theia AI dependencies to demonstrate MCP integration
package.json	Updated workspace pattern to include all packages
configs/local-linking.sh	Added server-mcp package to local linking script
.vscode/launch.json	Added debug configuration for server-mcp package

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Registers GLSP-announced MCP servers with the IDE's MCP frontend service so the agent can use them immediately after IDE startup. MCP integration - Discovers MCP server descriptors on each GLSP client contribution and adds them to the IDE's MCP host on startup. - Triggers an explicit start since the host's autostart hook only fires at frontend init. - Per-registration cleanup releases server entries and state-change subscriptions on GLSP failure or extension dispose, avoiding stale entries across IDE restarts under random-port defaults. Adopters - Set the configuration on the GLSP client contribution to enable MCP for a diagram language. - The workflow example demonstrates the end-to-end wiring with a transient connect notification and a copy-URL action. Misc - Sends a shutdown notification before the GLSP connection drops so the server tears down cleanly with the parent session. Part of eclipse-glsp/glsp#1546

tortmayr · 2026-05-11T12:06:38Z

    env:
      STANDALONE_URL: 'file://${{ github.workspace }}/glsp-client/examples/workflow-standalone/app/diagram.html'
      GLSP_SERVER_PORT: '8081'
+      GLSP_MCP_SERVER_PORT: '64577'


Why was this added?
Do we currently even have e2e tests for the mcp feature?

We do not, so I removed it again.

tortmayr · 2026-05-11T12:08:26Z

+    # Defensive: stale nested @eclipse-glsp copies from prior installs shadow the workspace
+    # symlinks via Node's nearest-node_modules-wins resolution → bundle fails.
+    # Remove them before re-linking.
+    find packages examples -path '*/node_modules/@eclipse-glsp' -type d -exec rm -rf {} + 2>/dev/null || true


Not sure if it's worth maintaining this script any longer.
We now have linking functionality built in the glsp cli tool.

We should probably update our repos accordingly.
But that's a thing for a follow-up

yeah, I think so too, should be done in a proper cleanup.

tortmayr · 2026-05-11T12:10:38Z

        return undefined;
    }
+
+    protected async getMcpServerPortFromEnv(): Promise<number | undefined> {


We could probably align this into one getPortFromEnv() method that just takes the env var as parameter
Instead of three more or less identical methods

tortmayr · 2026-05-11T12:16:04Z

+                        this.toDispose.push(
+                            Disposable.create(async () => {
+                                // Await the shutdown so the wire flushes before we dispose the connection.
+                                const client = await this.glspClient;


If this.glspClient hasn't resolved yet when dispose fires (e.g., contribution disposed during startup), the await will block the async body indefinitely, and connection.dispose() / channel.dispose() will never execute.
The previous code pushed connection and channel as separate disposables, guaranteeing synchronous cleanu

Good catch! We do a best effort shutdown now if the client already resolved but otherwise we will simply dispose as before.

tortmayr · 2026-05-11T12:19:08Z

+  "scripts": {
+    "build": "tsc -b",
+    "clean": "rimraf lib *.tsbuildinfo ",
+    "generate:index": "glsp generateIndex src/browser src/common src/node -s -f",


Suggested change

"generate:index": "glsp generateIndex src/browser src/common src/node -s -f",

"generate:index": "glsp generateIndex src/browser -s -f",

tortmayr · 2026-05-11T12:25:48Z

 Generate changelog entries by analyzing merged PRs since the last release.

 Execute these phases in order:
+


The CHANGELOG entry formatting changed from - (dash + 3 spaces) to - (dash + 1 space), which contradicts the style guide in SKILL.md line 84 that specifies "Entry prefix: - (dash + exactly 3 spaces)". If this is an intentional style migration,
the SKILL.md should be updated to match. If not, the CHANGELOG entry should retain the original format.

This might be related to the underlying version of prettier/eslint/markdown-lint that is used. I also experienced similar issues in other glsp projects.

The prettier actually enforces the 1 space when we do yarn format. I updated the skill for this as it proposes 3 spaces

tortmayr · 2026-05-11T12:26:57Z

+     * override via `rebind(GlspMcpRegistration).to(YourSubclass)` for environments where
+     * servers should be registered but kept off until the user starts them on-demand.
+     */
+    protected readonly autostart: boolean = true;


Remove the override fluff. (everything after the ;)

tortmayr · 2026-05-11T12:27:27Z

+     * Aggregated cleanup — owns one inner {@link DisposableCollection} per registration. Dispose
+     * triggers `removeServer` for every registration and drops the state-change subscriptions.
+     */
+    protected readonly toDispose = new DisposableCollection();


No need to add an additional comment for the general toDispose pattern

tortmayr · 2026-05-11T12:27:47Z

+     * GLSP servers boot on a random port by default, so a registered URL is stale on the next IDE
+     * launch. Drop our registrations on shutdown so the next session starts fresh.
+     */
+    dispose(): void {


Same. no need to comment dispose

tortmayr · 2026-05-11T12:28:30Z

+        // Per-registration cleanup group. Disposing it removes the MCP server entry AND drops the
+        // state-change subscription. Triggers either on definitive GLSP failure (state listener
+        // self-disposes) or on extension dispose (parent collection cascades).
+        const perRegistration = new DisposableCollection(


maybe remove comment here...

martin-fleck-at · 2026-05-12T10:15:37Z

@tortmayr Thank you for your feedback. Once the server is merged, I'll do a final update on the PR integrating all your comments.

martin-fleck-at requested review from Copilot and tortmayr December 18, 2025 19:34

Copilot AI reviewed Dec 18, 2025

View reviewed changes

Comment thread packages/theia-integration/src/browser/glsp-client-contribution.ts

Comment thread examples/workflow-theia/src/browser/workflow-glsp-client-contribution.ts

martin-fleck-at force-pushed the issues/1546 branch from 95ebe92 to 974b6d4 Compare December 18, 2025 19:43

This was referenced Dec 19, 2025

Add support for Model Context Protocol eclipse-glsp/glsp-server-node#120

Merged

Add support for Model Context Protocol eclipse-glsp/glsp-client#456

Merged

martin-fleck-at force-pushed the issues/1546 branch from 974b6d4 to 9e1afb7 Compare May 6, 2026 15:18

martin-fleck-at force-pushed the issues/1546 branch from 9e1afb7 to f944f7b Compare May 8, 2026 09:59

tortmayr requested changes May 11, 2026

View reviewed changes

	"generate:index": "glsp generateIndex src/browser src/common src/node -s -f",
	"generate:index": "glsp generateIndex src/browser -s -f",

		Generate changelog entries by analyzing merged PRs since the last release.

		Execute these phases in order:

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martin-fleck-at commented May 12, 2026

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martin-fleck-at commented Dec 18, 2025 •

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