MaxListenersExceededWarning: Possible EventEmitter memory leak detected in copilot-language-server

## Background

Since switching our copilot integration from using non-incremental updating (sending the entire document with each `textDocument/didChange` and keeping the version at 0) to incremental, I'm seeing the following error (doesn't always repro, feels like there's a timing issue involved). Not noticing any user impact, but wondering if I'm doing something wrong in my calling pattern to cause this.

> (node:4231) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 change listeners added to [EventEmitter]. MaxListeners is 10. Use emitter.setMaxListeners() to increase limit
(Use `copilot-language-server --trace-warnings ...` to show where the warning was created)

## RPC calls

Here are the messages involved in my most recent repro attempt (I've left out `statusNotification`, `didChangeStatus`, `preconditionsNotification`, and `featureFlagsNotification` messages as they seem ignorable in this context).

The document started in this state:

Final state:

### initialize (call)

```json
{"jsonrpc":"2.0","method":"initialize","params":{"processId":4218,"locale":"en","initializationOptions":{"editorInfo":{"name":"RStudio","version":"2025.06.999-dev+999"},"editorPluginInfo":{"name":"RStudio","version":"2025.06.999-dev+999"}},"capabilities":{"workspace":{"workspaceFolders":false}}},"id":"ca2a707b-e2c9-4e8d-959f-04e91bd9a9ef"}
```

### initialize (response)

```json
{"jsonrpc":"2.0","id":"ca2a707b-e2c9-4e8d-959f-04e91bd9a9ef","result":{"capabilities":{"textDocumentSync":{"openClose":true,"change":2},"notebookDocumentSync":{"notebookSelector":[{"notebook":"*"}]},"workspace":{"workspaceFolders":{"supported":false,"changeNotifications":false}},"executeCommandProvider":{"commands":["github.copilot.finishDeviceFlow","github.copilot.didAcceptCompletionItem","github.copilot.didAcceptNextEditSuggestionItem","github.copilot.didAcceptPanelCompletionItem"]},"inlineCompletionProvider":{}},"serverInfo":{"name":"GitHub Copilot Language Server","version":"1.335.0","nodeVersion":"20.18.2"}}}
```

### initialized (call)

```json
{"jsonrpc":"2.0","method":"initialized","params":{}}
```

### didChangeConfiguration (call)

```json
{"jsonrpc":"2.0","method":"workspace/didChangeConfiguration","params":{"settings":{}}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[lsp] GitHub Copilot Language Server 1.335.0 initialized"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[certificates] Removed 3 expired certificates"}}
```

### didFocus (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didFocus","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R"}}}
```

### didOpen (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":0,"text":"\na <- 5\nb <- a\nc <- 6\n\n# this is a comment\n"}}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":0},"position":{"line":6,"character":0},"context":{"triggerKind":2}},"id":"eddc0b88-a571-4714-8675-a789bf28537b"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[default] Context provider relatedFilesShim exceeded time budget of 150ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request 0d617a2f-ade8-4171-92f0-1eff00770737 at finished with 200 status after 772.2371669999998ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"eddc0b88-a571-4714-8675-a789bf28537b","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["027f8cfb-bd81-4aa4-a530-be2ff5b823d0"]},"insertText":"d <- b + c","range":{"start":{"line":6,"character":0},"end":{"line":6,"character":0}}}]}}
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["027f8cfb-bd81-4aa4-a530-be2ff5b823d0"]},"insertText":"d <- b + c","range":{"start":{"line":6,"character":0},"end":{"line":6,"character":0}}}}}
```

### didFocus (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didFocus","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R"}}}
```

### executeCommand (call -- accepted completion)

```json
{"jsonrpc":"2.0","method":"workspace/executeCommand","params":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["027f8cfb-bd81-4aa4-a530-be2ff5b823d0"]}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":1},"contentChanges":[{"range":{"start":{"line":6,"character":0},"end":{"line":6,"character":0}},"text":"d <- b + c\n"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":1},"position":{"line":7,"character":0},"context":{"triggerKind":2}},"id":"688ea3f7-b00e-488f-bd91-d980354ac3e0"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request 7aa36d44-e14a-4f67-bbb8-640b6d69b373 at finished with 200 status after 386.9849579999991ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"688ea3f7-b00e-488f-bd91-d980354ac3e0","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["1a6aece6-9d05-4ccf-9d55-ce4ec3b9b6d6"]},"insertText":"# this is another comment","range":{"start":{"line":7,"character":0},"end":{"line":7,"character":0}}}]}}
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["1a6aece6-9d05-4ccf-9d55-ce4ec3b9b6d6"]},"insertText":"# this is another comment","range":{"start":{"line":7,"character":0},"end":{"line":7,"character":0}}}}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":2},"contentChanges":[{"range":{"start":{"line":7,"character":0},"end":{"line":7,"character":0}},"text":"\n"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":2},"position":{"line":8,"character":0},"context":{"triggerKind":2}},"id":"55bc2bd3-c2bd-4333-be54-9b6e5cd95dc4"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request b3c77ec7-673d-4fb7-b898-d851a4fd9577 at finished with 200 status after 420.9779579999995ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"55bc2bd3-c2bd-4333-be54-9b6e5cd95dc4","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["192b74e7-f239-47a7-839e-74ca56bb4fca"]},"insertText":"# this is another comment","range":{"start":{"line":8,"character":0},"end":{"line":8,"character":0}}}]}}
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["192b74e7-f239-47a7-839e-74ca56bb4fca"]},"insertText":"# this is another comment","range":{"start":{"line":8,"character":0},"end":{"line":8,"character":0}}}}}
```

### executeCommand (call -- accepted completion)

```json
{"jsonrpc":"2.0","method":"workspace/executeCommand","params":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["192b74e7-f239-47a7-839e-74ca56bb4fca"]}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":3},"contentChanges":[{"range":{"start":{"line":8,"character":0},"end":{"line":8,"character":0}},"text":"# this is another comment"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":3},"position":{"line":8,"character":25},"context":{"triggerKind":2}},"id":"e75d818e-4ecd-48fa-960b-4570c77674a9"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request d30dc207-9119-49d5-94f4-77630cc21038 at finished with 200 status after 179.9752499999995ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"e75d818e-4ecd-48fa-960b-4570c77674a9","result":{"items":[]}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":4},"contentChanges":[{"range":{"start":{"line":8,"character":25},"end":{"line":8,"character":25}},"text":"\n"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":4},"position":{"line":9,"character":0},"context":{"triggerKind":2}},"id":"3272b1b2-c5a8-407b-86ee-2dee3d9f8241"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request bb7d86a2-fdab-4cb1-b0bc-a50e257da4d3 at finished with 200 status after 261.87508399999933ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"3272b1b2-c5a8-407b-86ee-2dee3d9f8241","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["5c6a8018-2378-4690-a859-4ecb00575201"]},"insertText":"e <- d + 1","range":{"start":{"line":9,"character":0},"end":{"line":9,"character":0}}}]}}
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["5c6a8018-2378-4690-a859-4ecb00575201"]},"insertText":"e <- d + 1","range":{"start":{"line":9,"character":0},"end":{"line":9,"character":0}}}}}
```

### executeCommand (call -- accepted completion)

```json
{"jsonrpc":"2.0","method":"workspace/executeCommand","params":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["5c6a8018-2378-4690-a859-4ecb00575201"]}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":5},"contentChanges":[{"range":{"start":{"line":9,"character":0},"end":{"line":9,"character":0}},"text":"e <- d + 1"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":5},"position":{"line":9,"character":10},"context":{"triggerKind":2}},"id":"5a24dd9f-1537-4588-ba0c-cb8ee9c9255c"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request a37a6e57-16e7-4cae-95d5-7223d7b57233 at finished with 200 status after 263.04254200000105ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"5a24dd9f-1537-4588-ba0c-cb8ee9c9255c","result":{"items":[]}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":6},"contentChanges":[{"range":{"start":{"line":9,"character":10},"end":{"line":9,"character":10}},"text":"\n"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":6},"position":{"line":10,"character":0},"context":{"triggerKind":2}},"id":"00566178-61ca-4957-9a26-00ff04e8921d"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request 03b5aa8c-5f6c-4229-8457-2ff872ef0142 at finished with 200 status after 365.898459ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"00566178-61ca-4957-9a26-00ff04e8921d","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["c389786a-5015-4cae-b3d2-cd93036f494b"]},"insertText":"# this is a third comment","range":{"start":{"line":10,"character":0},"end":{"line":10,"character":0}}}]}}
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["c389786a-5015-4cae-b3d2-cd93036f494b"]},"insertText":"# this is a third comment","range":{"start":{"line":10,"character":0},"end":{"line":10,"character":0}}}}}
```

### didChange (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","languageId":"r","version":7},"contentChanges":[{"range":{"start":{"line":10,"character":0},"end":{"line":10,"character":0}},"text":"\n"}]}}
```

### inlineCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/inlineCompletion","params":{"textDocument":{"uri":"file:///Users/gary/aaa/aaa/a.R","version":7},"position":{"line":11,"character":0},"context":{"triggerKind":2}},"id":"2b090533-d462-4bd0-b62b-57d2979e9dc7"}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[fetchCompletions] Request 3d022adc-effa-4b2a-bcd0-339a7e96f5fa at finished with 200 status after 374.5305420000004ms"}}
```

### logMessage (notification)

```json
{"jsonrpc":"2.0","method":"window/logMessage","params":{"type":3,"message":"[streamChoices] solution 0 returned. finish reason: [stop]"}}
```

### inlineCompletion (response)

```json
{"jsonrpc":"2.0","id":"2b090533-d462-4bd0-b62b-57d2979e9dc7","result":{"items":[{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["bb922201-3132-4a38-83a7-e935fdc1f032"]},"insertText":"f <- e + 2","range":{"start":{"line":11,"character":0},"end":{"line":11,"character":0}}}]}}
```

```
(node:4231) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 change listeners added to [EventEmitter]. MaxListeners is 10. Use emitter.setMaxListeners() to increase limit
(Use `copilot-language-server --trace-warnings ...` to show where the warning was created)
```

### didShowCompletion (call)

```json
{"jsonrpc":"2.0","method":"textDocument/didShowCompletion","params":{"item":{"command":{"title":"Completion Accepted","command":"github.copilot.didAcceptCompletionItem","arguments":["bb922201-3132-4a38-83a7-e935fdc1f032"]},"insertText":"f <- e + 2","range":{"start":{"line":11,"character":0},"end":{"line":11,"character":0}}}}}
```

Start with the reported Node.js MaxListenersExceededWarning and the incremental textDocument/didChange sequence in the issue. Reproduce the sequence around didFocus, didOpen, inlineCompletion, didShowCompletion, and accepted completions, using --trace-warnings as suggested. Done means determining whether the calling pattern causes the warning and documenting an actionable cause or fix.

Vom Indexierungsmodell aus dem Issue-Text verfasst.