jdtls-lsp Plugin Fails on Windows Due to Invalid File URI Format

Can confirm this issue on Windows 11 with Claude Code 2.1.11

Environment:

• OS: Windows 11
• Claude Code: 2.1.11
• Java: JDK 21.0.9.10 (Eclipse Adoptium)
• jdtls: Installed via VSCode Java extension (redhat.java-1.51.0-win32-x64)

Error in logs:
LSP error: plugin:jdtls-lsp:jdtls - ENOENT: no such file or directory, uv_spawn 'jdtls'

Observations:

1. The LSP manager appears to ignore the command field in .lsp.json configurations
2. Attempted workarounds (.cmd wrapper, absolute paths, python with args) had no effect - the error message remains identical
3. jdtls executable is in PATH and works when invoked directly from command line

This suggests the LSP manager has two issues on Windows:

• Not respecting custom command configurations in .lsp.json
• Not properly resolving executables that require file extensions (.cmd, .bat, .exe)

The URI format issue mentioned in this thread is likely compounding the problem.

+1

I am able to load with it in using this wrapper

jdtls_proxy.py

import sys
import subprocess
import re
import os

# 1. Path to your actual jdtls Python script
# Since your .bat uses %~dp0/jdtls, we target that file
real_jdtls = os.path.join(os.path.dirname(__file__), 'jdtls')

# 2. Launch the real JDTLS process
# We use subprocess.PIPE to intercept the input (stdin)
cmd = [sys.executable, real_jdtls] + sys.argv[1:]
process = subprocess.Popen(
    cmd, 
    stdin=subprocess.PIPE, 
    stdout=sys.stdout, 
    stderr=sys.stderr, 
    bufsize=0
)

try:
    while True:
        # JSON-RPC messages start with a Header (Content-Length: X)
        header = sys.stdin.readline()
        if not header:
            break
        
        if header.startswith("Content-Length:"):
            try:
                length = int(header.split(":")[1])
                # Skip the empty line (\r\n) after the header
                sys.stdin.readline() 
                
                # Read the actual JSON body
                body = sys.stdin.read(length)
                
                # THE FIX: Find "file://C:\" and change to "file:///C:/"
                # Also handles escaped backslashes often sent by Node.js
                new_body = re.sub(r'file://([a-zA-Z]):\\+', r'file:///\1:/', body)
                new_body = new_body.replace('\\\\', '/')
                
                # Recalculate length because adding the '/' and changing chars 
                # might change the byte count
                encoded_body = new_body.encode('utf-8')
                new_length = len(encoded_body)
                
                # Send the fixed message to the real Java server
                process.stdin.write(f"Content-Length: {new_length}\r\n\r\n".encode('utf-8'))
                process.stdin.write(encoded_body)
                process.stdin.flush()
            except Exception as e:
                # If parsing fails, just pass the original through
                process.stdin.write(header.encode('utf-8'))
                process.stdin.write(b"\r\n")
                process.stdin.write(body.encode('utf-8'))
                process.stdin.flush()
        else:
            # Pass through any other lines (like headers we don't care about)
            process.stdin.write(header.encode('utf-8'))
            process.stdin.flush()

except EOFError:
    pass
except KeyboardInterrupt:
    pass
finally:
    process.terminate()

Edit marketplace.json:

    {
      "name": "jdtls-lsp",
      "description": "Java language server (Eclipse JDT.LS) for code intelligence",
      "version": "1.0.0",
      "author": {
        "name": "Anthropic",
        "email": "support@anthropic.com"
      },
      "source": "./plugins/jdtls-lsp",
      "category": "development",
      "strict": false,
      "lspServers": {
        "jdtls": {
          "command": "jdtls.bat",
          "extensionToLanguage": {
            ".java": "java"
          }
        }
      }
    },

and jdtls.bat:

@echo off
python "%~dp0jdtls_proxy.py" %*

Seems like very minor error that could be addressed quickly, but I don't think they are any humans from Anthropic on this whole repo.

There is also a non fatal error about not being able to read "marketplace.json":

2026-01-27T16:31:59.499Z [DEBUG] Loading plugin jdtls-lsp from source: "./plugins/jdtls-lsp"
2026-01-27T16:31:59.500Z [DEBUG] Using provided version for jdtls-lsp@claude-plugins-official: 1.0.0
2026-01-27T16:31:59.504Z [DEBUG] Plugin jdtls-lsp@claude-plugins-official version 1.0.0 already cached at C:\Users\[REDACTED]\.claude\plugins\cache\claude-plugins-official\jdtls-lsp\1.0.0
2026-01-27T16:31:59.537Z [DEBUG] Copied local plugin jdtls-lsp to versioned cache: C:\Users\[REDACTED]\.claude\plugins\cache\claude-plugins-official\jdtls-lsp\1.0.0
2026-01-27T16:31:59.538Z [DEBUG] Plugin jdtls-lsp has no entry.skills defined
2026-01-27T16:31:59.550Z [DEBUG] Checking plugin jdtls-lsp: skillsPath=none, skillsPaths=0 paths
2026-01-27T16:32:02.244Z [DEBUG] Loaded 1 LSP server(s) from plugin: jdtls-lsp
2026-01-27T16:32:02.244Z [DEBUG] Queued request handler for plugin:jdtls-lsp:jdtls.workspace/configuration (connection not ready)
2026-01-27T16:32:02.245Z [DEBUG] Starting LSP server instance: plugin:jdtls-lsp:jdtls
2026-01-27T16:32:02.251Z [DEBUG] Queued notification handler for plugin:jdtls-lsp:jdtls.textDocument/publishDiagnostics (connection not ready)
2026-01-27T16:32:02.251Z [DEBUG] Registered diagnostics handler for plugin:jdtls-lsp:jdtls
2026-01-27T16:32:02.254Z [DEBUG] Applied queued notification handler for plugin:jdtls-lsp:jdtls.textDocument/publishDiagnostics
2026-01-27T16:32:02.254Z [DEBUG] Applied queued request handler for plugin:jdtls-lsp:jdtls.workspace/configuration
2026-01-27T16:32:02.254Z [DEBUG] LSP client started for plugin:jdtls-lsp:jdtls
2026-01-27T16:32:02.255Z [DEBUG] [LSP PROTOCOL plugin:jdtls-lsp:jdtls] Sending request 'initialize - (0)'.
2026-01-27T16:32:02.920Z [DEBUG] [LSP SERVER plugin:jdtls-lsp:jdtls] WARNING: Using incubator modules: jdk.incubator.vector
2026-01-27T16:32:03.830Z [DEBUG] [LSP SERVER plugin:jdtls-lsp:jdtls] Jan 27, 2026 4:32:03 PM org.apache.aries.spifly.BaseActivator log
2026-01-27T16:32:06.516Z [DEBUG] [LSP PROTOCOL plugin:jdtls-lsp:jdtls] Received response 'initialize - (0)' in 4261ms.
2026-01-27T16:32:06.516Z [DEBUG] [LSP PROTOCOL plugin:jdtls-lsp:jdtls] Sending notification 'initialized'.
2026-01-27T16:32:06.516Z [DEBUG] LSP server plugin:jdtls-lsp:jdtls initialized
2026-01-27T16:32:06.516Z [DEBUG] LSP server instance started: plugin:jdtls-lsp:jdtls
2026-01-27T16:32:06.803Z [DEBUG] Using provided version for jdtls-lsp@claude-plugins-official: 1.0.0
2026-01-27T16:32:11.758Z [DEBUG] Failed to read raw marketplace.json: Error: ENOENT: no such file or directory, open 'C:\Users\[REDACTED]\.claude\plugins\cache\claude-plugins-official\jdtls-lsp\.claude-plugin\marketplace.json'

Frankly I don't know who let this into a release buid ... Claude is great, but this is an absolute MESS.

The same for me. jdtls-lsp is not working on Windows.

Do these defects actually get looked at? Also. I don't see the point of releasing functionality that hasn't been tested. These are not edge cases, these are basic smoke test type defects.

Do these defects actually get looked at? Also. I don't see the point of releasing functionality that hasn't been tested. These are not edge cases, these are basic smoke test type defects.

Maybe if these this issue gets enough attention and there are many duplicates somehow it bubbles up as something that actually gets worked on. Another issue was closed as a duplicate and linked here by Claude itself. So there is some kind of awareness of it.

Still reproduces as of 2.1.45

> Do these defects actually get looked at? Also. I don't see the point of releasing functionality that hasn't been tested. These are not edge cases, these are basic smoke test type defects. Maybe if these this issue gets enough attention and there are many duplicates somehow it bubbles up as something that actually gets worked on. Another issue was closed as a duplicate and linked here by Claude itself. So there is some kind of awareness of it.

It needs 10 upvotes to "bubble up" - get your friends on the case.

Still happening in 2.1.71

I cannot believe how long this has been going on. I also created a proxy, using Java, to convert the URL format, but I cannot share it with the rest of my team that way - the underlying issue needs resolving!

reproduces on v2.1.78

Same on 2.1.80 with php-lsp

Still reproducing on v2.1.87

still reproducing in v2.1.97

I have a practical solution, and the specific steps are as follows:

1. Download the latest stable JDTLS compressed package: https://www.eclipse.org/downloads/download.php?file=/jdtls/milestones/1.58.0/jdt-language-server-1.58.0-202604151538.tar.gz
2. Unzip it to a local directory, for example: D:\Tools\jdtls
3. Add D:\Tools\jdtls\bin to your PATH environment variable.
4. Open the ~\.claude\plugins\marketplaces\claude-plugins-official\.claude-plugin\marketplace.json file and search for jdtls.
5. Modify the found JDTLS LSP configuration information as follows. Note: change "command": "jdtls" to "command": "jdtls.bat":

``json
"lspServers": {
"jdtls": {
"command": "jdtls.bat",
"extensionToLanguage": {
".java": "java"
},
"startupTimeout": 120000
}
}
``

1. Restart Claude Code, and Claude Code's LSP tool will be able to use JDTLS correctly.

I have a practical solution, and the specific steps are as follows: 1. Download the latest stable JDTLS compressed package: https://www.eclipse.org/downloads/download.php?file=/jdtls/milestones/1.58.0/jdt-language-server-1.58.0-202604151538.tar.gz 2. Unzip it to a local directory, for example: D:\Tools\jdtls 3. Add D:\Tools\jdtls\bin to your PATH environment variable. 4. Open the ~\.claude\plugins\marketplaces\claude-plugins-official\.claude-plugin\marketplace.json file and search for jdtls. 5. Modify the found JDTLS LSP configuration information as follows. Note: change "command": "jdtls" to "command": "jdtls.bat": "lspServers": { "jdtls": { "command": "jdtls.bat", "extensionToLanguage": { ".java": "java" }, "startupTimeout": 120000 } } 6. Restart Claude Code, and Claude Code's LSP tool will be able to use JDTLS correctly.

note that: jdtls-1.58.0 required jdk-version is 21 but not 17.

@Pcyslist I was doing the same, but this configuration keeps getting restored to the defaults. It seems like Claude Code pulls marketplace settings every new session or periodically.
I made a hook that overwrites those settings on session startup.
It works.

6 new issues have been created and linked here by the bots. Why can't you use Claude to fix this?