Mcp Mat

io.github.codelipenghuiPublished by GitHub account codelipenghuiv0.1.0Updated Oct 24, 2026

Headless Eclipse MAT MCP server for Java heap dump analysis

VerifiedSTDIODesktop onlyDeveloper Tools Data & Analytics

Server details

Identifier: io.github.codelipenghui/mcp-mat
Transport: STDIO
Runtime: Desktop only
Trust: Verified
Published: Sep 16, 2026

Security note

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Overview

AI-generated overview

Headless Eclipse MAT MCP server that lets an assistant analyze Java heap dumps: run reports, OQL queries and built-in MAT commands.

What you can do: Check MAT and Java runtime availability and whether index artifacts exist for a heap dump, and get OQL parser guidance and supported patterns. Run predefined MAT reports such as leak suspects and system overview. Execute OQL queries and return results inline. Run built-in MAT analysis commands covering dominator trees, GC root paths, histograms, leak detection, threads, collections, references, finalizers, retained sets, top consumers, strings and heap overview. Export heap dumps and run comparison reports against a baseline dump.
When to use it: Useful when investigating Java memory problems from a heap dump: finding leaks, dominator trees, GC root paths, thread and collection analysis, or comparing two dumps. Meant for developers and operators who already have Eclipse MAT installed and a .hprof file to inspect.
Requirements: Runs locally as a Node.js process (npm package mcp-mat, or built from source). Needs a Java runtime (JAVA_PATH, default java) and an Eclipse MAT installation (MAT_HOME, or MAT_LAUNCHER). Optional settings include MAT_XMX_MB (default 4096), MAT_TIMEOUT_SEC (default 1800) and working directories under /tmp. Desktop only.

Before you install

Analysis runs MAT as a local Java process with a large default heap (MAT_XMX_MB 4096) and a long default timeout (MAT_TIMEOUT_SEC 1800), so large dumps can consume significant memory and time. Heap dumps contain sensitive application data, and MAT writes config, workspace and debug logs to local directories by default; MAT_PRIVACY_MODE and the log directory settings control what is kept.

Installation

In SourceWeft

Open Mcp Mat in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

mcp-mat

Headless MCP server for Eclipse MAT using direct java -jar org.eclipse.equinox.launcher_*.jar execution.

Features

mat_healthcheck — Validate MAT launcher and Java runtime availability
mat_parse_report — Run predefined MAT reports (leak suspects, system overview, etc.)
mat_oql_query — Execute OQL queries and return inline results
mat_run_command — Execute 56 built-in MAT analysis commands (histogram, dominator_tree, path2gc, thread_overview, etc.)
mat_index_status — Check whether MAT index artifacts exist for a heap dump
mat_oql_spec — Return OQL parser guidance and supported patterns

Supported Commands (`mat_run_command`)

Dominator tree analysis

dominator_tree, show_dominator_tree, immediate_dominators, big_drops_in_dominator_tree

Path to GC roots

path2gc, merge_shortest_paths, gc_roots

Histogram & object listing

histogram, delta_histogram*, list_objects, group_by_value, duplicate_classes

Leak detection

leakhunter, leakhunter2, find_leaks, find_leaks2, reference_leak

Thread analysis

thread_overview, thread_details, thread_stack

Collection analysis

collection_fill_ratio, collections_grouped_by_size, array_fill_ratio, arrays_grouped_by_size, hash_entries, map_collision_ratio, extract_list_values, hash_set_values, primitive_arrays_with_a_constant_value

Reference analysis

references_statistics, weak_references_statistics, soft_references_statistics, phantom_references_statistics, finalizer_references_statistics

Finalizer analysis

finalizer_overview, finalizer_thread, finalizer_queue, finalizer_in_processing, finalizer_thread_locals

Retained set

show_retained_set, customized_retained_set

Component & top consumers

component_report, component_report_top, top_consumers, top_consumers_html, pie_biggest_objects

String & memory waste

find_strings, waste_in_char_arrays

Heap info & misc

heap_dump_overview, unreachable_objects, system_properties, class_references, comparison_report*

Eclipse/OSGi specific

bundle_registry, leaking_bundles

Export

export_hprof

* Requires a baseline heap dump (second .hprof file).

OQL mode notes

This server normalizes client OQL input and wraps it for MAT parse-app command mode.
You can send OQL with or without outer quotes.
For class ranking and top consumers, prefer mat_parse_report with org.eclipse.mat.api:overview and parse Class_Histogram*.txt.
For object inspection, use simple field-level OQL patterns (INSTANCEOF, OBJECTS 0x...).

Environment

All environment variables are optional:

MAT_HOME
MAT_LAUNCHER
JAVA_PATH (default java)
MAT_XMX_MB (default 4096)
MAT_TIMEOUT_SEC (default 1800)
MAT_CONFIG_DIR (default /tmp/mat-config)
MAT_DATA_DIR (default /tmp/mat-workspace)
MAT_DEBUG (default false)
MAT_DEBUG_LOG_DIR (default /tmp/mcp-mat-logs)
MAT_PRIVACY_MODE (default false)
MAT_OQL_MAX_BYTES (default 16384)
MAT_RESULT_PREVIEW_LINES (default 20)
MAT_STDIO_TAIL_CHARS (default 4000)

Run

Test

Install via npx

No build step required. Install directly from npm:

Claude Code

Add to ~/.claude/settings.json or project .claude/settings.json:

json

{  "mcpServers": {    "mat": {      "command": "npx",      "args": ["-y", "mcp-mat"],      "env": {        "MAT_HOME": "/Applications/MemoryAnalyzer.app/Contents/Eclipse"      }    }  }}

{  "mcpServers": {    "mat": {      "command": "npx",      "args": ["-y", "mcp-mat"],      "env": {        "MAT_HOME": "/Applications/MemoryAnalyzer.app/Contents/Eclipse"      }    }  }}

Codex

bash

codex mcp add \  --env MAT_HOME=/Applications/MemoryAnalyzer.app/Contents/Eclipse \  mat \  npx -y mcp-mat

codex mcp add \  --env MAT_HOME=/Applications/MemoryAnalyzer.app/Contents/Eclipse \  mat \  npx -y mcp-mat

Install in Claude Code (from source)

Add the MCP server to Claude Code settings (~/.claude/settings.json or project .claude/settings.json):

json

{  "mcpServers": {    "mat": {      "command": "node",      "args": ["/path/to/mcp-mat/dist/src/server.js"],      "env": {        "MAT_HOME": "/Applications/MemoryAnalyzer.app/Contents/Eclipse"      }    }  }}

{  "mcpServers": {    "mat": {      "command": "node",      "args": ["/path/to/mcp-mat/dist/src/server.js"],      "env": {        "MAT_HOME": "/Applications/MemoryAnalyzer.app/Contents/Eclipse"      }    }  }}

Install in Codex (from source)

Build first:

Add MCP server to Codex: