Add support for Model Context Protocol (#120)

Exposes each GLSP server as an MCP server over Streamable HTTP, so LLM
clients can query and mutate diagrams via MCP resources, tools, and
prompts.

Architecture
- One MCP endpoint per GLSP server process; under per-window
  deployment, one endpoint per application instance.
- Auto-discovers diagram-scoped contributions from all GLSP client
  sessions and merges them into a shared surface with cross-session
  ID aliasing.
- Pluggable model-serializer, label-provider, and element-types
  extension points for diagram-specific overrides.
- Opt-in: started only when configured on initialize.
- Random port by default; the announced URL is surfaced for adopter
  discovery.
- No built-in auth; loopback-only unless explicitly acknowledged.
- Targets MCP spec 2025-06-18 via the official SDK.

Adopters
- Diagram module: register language-specific tools, prompts,
  resources, and override the diagram extension points.
- Server module: configure server-wide options (port, route, auth
  acknowledgement).
- The workflow server example wires both end-to-end.

Server framework
- Adds an initialize-contribution extension point on the default
  GLSP server, used by MCP to surface configuration on initialize.
  The previous `handleInitializeArgs` hook is deprecated — adopters
  subclassing the default server should migrate.

Documentation
- Adopter README plus a separate architecture document covering the
  feature matrix, lifecycle, extension points, and rationale.

Misc
- Small fix to a base type-guard on edges in the graph package.
- Disposes the server instance when the JSON-RPC client connection
  closes uncleanly (browser/IDE force-close).
- Action dispatcher drops stale response actions arriving without a
  registered handler instead of throwing.

Part of eclipse-glsp/glsp#1546

Co-authored-by: Andreas Hell <44035624+Sakrafux@users.noreply.github.com>

Author: martin-fleck-at

.claude/skills/generate-changelog/SKILL.md

@@ -8,6 +8,7 @@ description: Generate changelog entries from merged PRs since the last release.
 Generate changelog entries by analyzing merged PRs since the last release.
 
 Execute these phases in order:
+
 1. **Data Gathering** — find last release, fetch PRs, classify, generate entries
 2. **Changelog Update** — write entries into CHANGELOG.md
 3. **Review & Approval** — present the actual diff to the user for review
@@ -20,11 +21,13 @@ Execute these phases in order:
 ### Step 1.1: Find the latest release tag
 
 Run:
+
 ```bash
 git tag --sort=-creatordate | grep -E '^v[0-9]+\.[0-9]+\.[0-9]+$' | head -1
 ```
 
 Record as `LAST_TAG`. Get the tag's date:
+
 ```bash
 git log -1 --format=%aI $LAST_TAG
 ```
@@ -46,12 +49,13 @@ Use the date portion only from `TAG_DATE` (e.g. `2026-02-09`).
 ### Step 1.4: Filter PRs
 
 **Skip rules** (in order):
+
 1. PR has the `changelog` label → skip (already tracked in a previous changelog update)
 2. Author login is `dependabot` or `dependabot[bot]` → skip
 3. Title matches version bump patterns → skip:
-   - Starts with `Switch to` and contains `-next`
-   - Title is a bare version like `vX.Y.Z`
-   - Title starts with `Release v`
+    - Starts with `Switch to` and contains `-next`
+    - Title is a bare version like `vX.Y.Z`
+    - Title starts with `Release v`
 4. Title contains `update changelog` (case insensitive) → skip
 5. Title is purely CI/metadata (readme badges, workflow config) AND body does NOT contain `[x] This PR should be mentioned in the changelog` → skip
 
@@ -62,9 +66,9 @@ Use the date portion only from `TAG_DATE` (e.g. `2026-02-09`).
 1. If body contains `[x] This PR introduces a breaking change` → **breaking**
 2. If body contains `[ ] This PR introduces a breaking change` → **normal**
 3. If no checkbox info, analyze title and body:
-   - Breaking keywords: "refactor", "rename", "remove", "replace", "migrate", "breaking", "deprecate"
-   - Clearly non-breaking (bug fix, docs, minor enhancement) → **normal**
-   - Uncertain → flag for user review
+    - Breaking keywords: "refactor", "rename", "remove", "replace", "migrate", "breaking", "deprecate"
+    - Clearly non-breaking (bug fix, docs, minor enhancement) → **normal**
+    - Uncertain → flag for user review
 
 ### Step 1.6: Assign category tags
 
@@ -75,57 +79,65 @@ Pick the most fitting tag from the vocabulary (Step 1.2) based on PR title and b
 #### Entry Format
 
 **Normal changes:**
+
 ```
 -   [tag] Description [#N](https://github.com/OWNER/REPO/pull/N)
 ```
 
 **Breaking changes** with migration sub-items:
+
 ```
 -   [tag] Description [#N](https://github.com/OWNER/REPO/pull/N)
     -   Migration detail 1
     -   Migration detail 2
 ```
 
 **Multiple PRs for the same change:**
+
 ```
 -   [tag] Description [#N](url) [#M](url)
 ```
 
 #### Style Guide
 
 **Formatting:**
-- Entry prefix: `-   ` (dash + exactly 3 spaces)
-- Sub-item indent: 4 spaces + `-   ` (4 spaces from parent dash)
-- Sub-sub-item indent: 8 spaces + `-   `
-- Single space between `[tag]` and description text
-- Single space before PR link at end of line
-- PR links are mandatory, full URLs: `[#123](https://github.com/OWNER/REPO/pull/123)`
+
+-   Entry prefix: `-   ` (dash + exactly 3 spaces)
+-   Sub-item indent: 4 spaces + `-   ` (4 spaces from parent dash)
+-   Sub-sub-item indent: 8 spaces + `-   `
+-   Single space between `[tag]` and description text
+-   Single space before PR link at end of line
+-   PR links are mandatory, full URLs: `[#123](https://github.com/OWNER/REPO/pull/123)`
 
 **Wording:**
-- Always start with a **present tense imperative verb** (not past tense)
-- Common verbs: Fix, Improve, Add, Update, Extend, Ensure, Introduce, Remove, Refactor, Rename, Provide, Allow, Support
-- **Bug fixes**: "Fix a bug that caused/prevented...", "Fix X behavior"
-- **Features**: "Introduce...", "Add support for...", "Provide..."
-- **Enhancements**: "Improve...", "Extend...", "Ensure that..."
-- **Refactors**: "Refactor...", "Rework...", "Rename..."
-- Be specific — never "Fix various issues"
+
+-   Always start with a **present tense imperative verb** (not past tense)
+-   Common verbs: Fix, Improve, Add, Update, Extend, Ensure, Introduce, Remove, Refactor, Rename, Provide, Allow, Support
+-   **Bug fixes**: "Fix a bug that caused/prevented...", "Fix X behavior"
+-   **Features**: "Introduce...", "Add support for...", "Provide..."
+-   **Enhancements**: "Improve...", "Extend...", "Ensure that..."
+-   **Refactors**: "Refactor...", "Rework...", "Rename..."
+-   Be specific — never "Fix various issues"
 
 **Capitalization:**
-- Tags are always lowercase: `[diagram]`, not `[Diagram]`
-- Description starts lowercase after the tag (unless proper noun or code element)
-- Section headers: Title Case (`### Potentially Breaking Changes`)
+
+-   Tags are always lowercase: `[diagram]`, not `[Diagram]`
+-   Description starts lowercase after the tag (unless proper noun or code element)
+-   Section headers: Title Case (`### Potentially Breaking Changes`)
 
 **Description cleanup from PR title:**
-- Remove issue tracker prefixes (e.g. `GLSP-1234:`, `GH-123:`, `ISSUE-456:`)
-- Remove conventional commit prefixes: `fix:`, `feat:`, `chore:`
-- Rephrase bug-report style to changelog style:
-  - BAD: "Edit label UI does not resize on graph zoom"
-  - GOOD: "Fix edit label UI not resizing on graph zoom"
-- Keep concise — one line
+
+-   Remove issue tracker prefixes (e.g. `GLSP-1234:`, `GH-123:`, `ISSUE-456:`)
+-   Remove conventional commit prefixes: `fix:`, `feat:`, `chore:`
+-   Rephrase bug-report style to changelog style:
+    -   BAD: "Edit label UI does not resize on graph zoom"
+    -   GOOD: "Fix edit label UI not resizing on graph zoom"
+-   Keep concise — one line
 
 **Breaking changes:**
-- Describe what changed, why it's breaking, and how to migrate
-- Extract migration sub-items from the PR body's "What it does" section
+
+-   Describe what changed, why it's breaking, and how to migrate
+-   Extract migration sub-items from the PR body's "What it does" section
 
 ---
 
@@ -136,13 +148,15 @@ Pick the most fitting tag from the vocabulary (Step 1.2) based on PR title and b
 Read `CHANGELOG.md` in the repository root.
 
 **Active section detection:**
-- An active section has the `- active` suffix (e.g. `## v2.7.0 - active`)
-- If an active section exists → merge new entries into it
-- If the topmost section is a released version (no `- active` suffix) → create a new active section above it
+
+-   An active section has the `- active` suffix (e.g. `## v2.7.0 - active`)
+-   If an active section exists → merge new entries into it
+-   If the topmost section is a released version (no `- active` suffix) → create a new active section above it
 
 **Creating a new section:**
-- Bump the minor version of `LAST_TAG` (e.g. `v2.6.0` → `v2.7.0`)
-- Insert after the title line, before the first `## ` heading:
+
+-   Bump the minor version of `LAST_TAG` (e.g. `v2.6.0` → `v2.7.0`)
+-   Insert after the title line, before the first `## ` heading:
 
 ```markdown
 ## v2.7.0 - active
@@ -160,9 +174,10 @@ Read `CHANGELOG.md` in the repository root.
 Only include "Potentially Breaking Changes" if there are breaking entries.
 
 **Merging into existing active section:**
-- Check PR numbers against existing entries to avoid duplicates
-- Append new entries to the appropriate subsection
-- Create missing subsections as needed
+
+-   Check PR numbers against existing entries to avoid duplicates
+-   Append new entries to the appropriate subsection
+-   Create missing subsections as needed
 
 ### Step 2.2: Write the updated CHANGELOG.md
 
@@ -185,13 +200,14 @@ Present the diff to the user.
 List any entries flagged as uncertain (category or breaking status) and ask the user to resolve them.
 
 Even if nothing is uncertain, ask:
+
 > "Does everything look correct, or would you like to adjust any entries?"
 
 ### Step 3.3: Collect user feedback
 
-- **Approve as-is** → done (or proceed to Phase 4 if PR was requested)
-- **Request edits** → apply changes, show updated diff, ask again
-- **Resolve uncertain items** → apply, show updated diff
+-   **Approve as-is** → done (or proceed to Phase 4 if PR was requested)
+-   **Request edits** → apply changes, show updated diff, ask again
+-   **Resolve uncertain items** → apply, show updated diff
 
 **Do NOT proceed to Phase 4 unless the user explicitly requests a PR.**
 
@@ -200,11 +216,13 @@ Even if nothing is uncertain, ask:
 ## Phase 4: PR Creation (Optional)
 
 Only execute this phase if the user explicitly requests a PR (either in their initial prompt or after reviewing the changelog). If the user hasn't mentioned a PR, ask after approval:
+
 > "Would you like me to create a PR for this changelog update, or are you done?"
 
 ### Step 4.1: Determine the branch name
 
 Check if `changelog-update` exists on remote:
+
 ```bash
 git ls-remote --heads origin changelog-update
 ```
@@ -229,6 +247,7 @@ Report the PR URL.
 ### Step 4.4: Label referenced PRs
 
 Add the `changelog` label to every PR mentioned in the new entries:
+
 ```bash
 gh pr edit PR_NUMBER --add-label "changelog"
 ```

eslint.config.mjs

@@ -22,6 +22,11 @@ export default [
         rules: {
             '@typescript-eslint/no-shadow': 'off',
             '@typescript-eslint/padding-line-between-statements': 'off',
+            // The MCP SDK uses `exports` subpath patterns with explicit `.js` suffixes (e.g.
+            // `@modelcontextprotocol/sdk/server/mcp.js`). The TypeScript import resolver does
+            // not match these against the `./*` wildcard, even though tsc and Node resolve
+            // them correctly at compile- and runtime.
+            'import-x/no-unresolved': ['error', { ignore: ['^@modelcontextprotocol/sdk/'] }],
             'no-restricted-imports': [
                 'warn',
                 {

examples/workflow-server/package.json

@@ -58,6 +58,7 @@
   "dependencies": {
     "@eclipse-glsp/layout-elk": "2.7.0-next",
     "@eclipse-glsp/server": "2.7.0-next",
+    "@eclipse-glsp/server-mcp": "2.7.0-next",
     "inversify": "^6.1.3"
   },
   "devDependencies": {

examples/workflow-server/src/common/graph-extension.ts

@@ -1,5 +1,5 @@
 /********************************************************************************
- * Copyright (c) 2022-2023 STMicroelectronics and others.
+ * Copyright (c) 2022-2026 STMicroelectronics and others.
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v. 2.0 which is available at
@@ -86,7 +86,7 @@ export class TaskNodeBuilder<T extends TaskNode = TaskNode> extends GNodeBuilder
     protected createCompartmentHeader(): GLabel {
         return new GLabelBuilder(GLabel)
             .type(ModelTypes.LABEL_HEADING)
-            .id(this.proxy.id + '_classname')
+            .id(this.proxy.id + '_label')
             .text(this.proxy.name)
             .build();
     }
@@ -151,7 +151,7 @@ export class CategoryNodeBuilder<T extends Category = Category> extends Activity
     protected createCompartmentHeader(): GLabel {
         return new GLabelBuilder(GLabel)
             .type(ModelTypes.LABEL_HEADING)
-            .id(this.proxy.id + '_classname')
+            .id(this.proxy.id + '_label')
             .text(this.proxy.name)
             .build();
     }

examples/workflow-server/src/common/mcp/workflow-element-types-provider.ts

@@ -0,0 +1,54 @@
+/********************************************************************************
+ * Copyright (c) 2026 EclipseSource and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the Eclipse
+ * Public License v. 2.0 are satisfied: GNU General Public License, version 2
+ * with the GNU Classpath Exception which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ ********************************************************************************/
+
+import { DefaultTypes } from '@eclipse-glsp/server';
+import { ElementTypeEntry, ElementTypes, ElementTypesProvider } from '@eclipse-glsp/server-mcp';
+import { injectable } from 'inversify';
+import { ModelTypes } from '../util/model-types';
+
+const NODE_TYPES: ElementTypeEntry[] = [
+    { id: ModelTypes.AUTOMATED_TASK, label: 'Automated Task', description: 'Task without human input', acceptsText: true },
+    { id: ModelTypes.MANUAL_TASK, label: 'Manual Task', description: 'Task done by a human', acceptsText: true },
+    { id: ModelTypes.JOIN_NODE, label: 'Join Node', description: 'Gateway that merges parallel flows', acceptsText: false },
+    { id: ModelTypes.FORK_NODE, label: 'Fork Node', description: 'Gateway that splits into parallel flows', acceptsText: false },
+    { id: ModelTypes.MERGE_NODE, label: 'Merge Node', description: 'Gateway that merges alternative flows', acceptsText: false },
+    { id: ModelTypes.DECISION_NODE, label: 'Decision Node', description: 'Gateway that splits into alternative flows', acceptsText: false },
+    { id: ModelTypes.CATEGORY, label: 'Category', description: 'Container node that groups other elements', acceptsText: true }
+];
+
+const EDGE_TYPES: ElementTypeEntry[] = [
+    { id: DefaultTypes.EDGE, label: 'Edge', description: 'Standard control flow edge', acceptsText: false },
+    {
+        id: ModelTypes.WEIGHTED_EDGE,
+        label: 'Weighted Edge',
+        description: 'Edge that indicates a weighted probability. Typically used with a Decision Node.',
+        acceptsText: false
+    }
+];
+
+/**
+ * Workflow-specific {@link ElementTypesProvider}. Returns the constant set of creatable types
+ * with richer LLM-facing fields (`description`, `acceptsText`) than the default registry-scrape
+ * impl can infer. Bound on the workflow MCP diagram module via `bindElementTypesProvider()`;
+ * the standard `element-types` tool handler exposes the full entries via `structuredContent`
+ * (with a short summary in the text content) — no handler rebind needed.
+ */
+@injectable()
+export class WorkflowElementTypesProvider implements ElementTypesProvider {
+    get(): ElementTypes {
+        return { nodeTypes: NODE_TYPES, edgeTypes: EDGE_TYPES };
+    }
+}

examples/workflow-server/src/common/mcp/workflow-mcp-label-provider.ts

@@ -0,0 +1,37 @@
+/********************************************************************************
+ * Copyright (c) 2026 EclipseSource and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the Eclipse
+ * Public License v. 2.0 are satisfied: GNU General Public License, version 2
+ * with the GNU Classpath Exception which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ ********************************************************************************/
+
+import { GLabel, GModelElement } from '@eclipse-glsp/server';
+import { DefaultMcpLabelProvider } from '@eclipse-glsp/server-mcp';
+import { injectable } from 'inversify';
+import { ModelTypes } from '../util/model-types';
+
+/**
+ * Workflow-specific {@link DefaultMcpLabelProvider}: category labels are nested inside a
+ * compartment-header child rather than directly under the category, so the default
+ * direct-child lookup misses them. Other workflow element types fall through to the
+ * inherited default.
+ */
+@injectable()
+export class WorkflowMcpLabelProvider extends DefaultMcpLabelProvider {
+    override getLabel(element: GModelElement): GLabel | undefined {
+        if (element.type === ModelTypes.CATEGORY) {
+            const header = element.children.find(child => child.type === ModelTypes.COMP_HEADER);
+            return header?.children.find((child): child is GLabel => child instanceof GLabel);
+        }
+        return super.getLabel(element);
+    }
+}