Serialization error

Support Bug Reports
147

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

I am facing error in the recent updates of Cursor. Do we need to install Cursor (system) or Cursor (User) ?
And also frequently getting error like below
Request ID: 993fce0e-5643-437d-91f9-f267c6542bc4
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Users/user/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7349:369901

Request ID: 5a0b319e-2a47-44cf-afab-881b73314db8

{“error”:“ERROR_USER_ABORTED_REQUEST”,“details”:{“title”:“User aborted request.”,“detail”:“Tool call ended before result was received”,“isRetryable”:false,“additionalInfo”:{},“buttons”:,“planChoices”:},“isExpected”:true}
ConnectError: [aborted] Error
at ZWl.$endAiConnectTransportReportError (vscode-file://vscode-app/c:/Users/user/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:375028)
How to resolve this ?

Steps to Reproduce

How can i reprodice?

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version:1.7.53 (user)

Does this stop you from using Cursor

No - Cursor works, but with this issue

148

Request ID: d6965003-561a-425d-9fb9-290bebcc7e8b
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472

149

Persistent Serialization Error Despite Updates and Workarounds (Request ID: e0201ffa-773d-4680-a89f-98e932701dfe)Hi Cursor Team and Community,I’m experiencing the ongoing “Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools” bug, which has been reported in this thread since July. Despite trying multiple workarounds, it persists and disrupts my workflow.Details:

  • Cursor Version: [Your Cursor Version, e.g., 1.7.4] (just updated via official download)

  • OS: [Your OS, e.g., Windows 11]

  • Trigger: [Brief description of when it happens, e.g., when using Agent to run/debug Python scripts with command outputs; happens mid-response during tool calls]

  • Request ID: e0201ffa-773d-4680-a89f-98e932701dfe

  • Model Used: [e.g., Claude 3.5 Sonnet / DeepSeek / Auto]

  • Location: China (using VPN for access, but error seems client-side)

What I’ve Tried (No Luck):

  • Updated to latest version and restarted.

  • Cleared all caches (CachedData, globalStorage, workspaceStorage, etc.) via manual deletion and in-app Clear Cache.

  • Logged out/in and reloaded window.

  • Created .cursorrules in project root to limit outputs (content below).

  • Switched to shorter prompts and new chat sessions.

  • Disabled linter interactions.

.cursorrules Content:

# é™ćˆ¶ć‘œä»€èŸ“ć‡ș长ćșŠïŒŒéżć… serialization error
- Limit command outputs to 1000 characters max
- Truncate verbose logs or progress bars in responses
- Avoid running files with verbose logging (use --quiet flag if possible)
- Summarize long outputs instead of pasting full logs

The error still occurs consistently on long-ish responses or tool executions, making Agent mode unreliable. Any ETA on a fix? Or additional diagnostics I can run?Thanks for the great tool—looking forward to resolution!

150

Request ID: 01495017-ac0d-40f8-b6a1-9a3205620fc4
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Users/webmarke22/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472
Versione: 1.7.44 (user setup)
Commit: 1.99.3
Data: 9d178a4■■■89981b62546448bb32920a8219a5d0
Electron: 2025-10-10T15:43:37.500Z
ElectronBuildId: 34.5.8
Chromium: undefined
Node.js: 132.0.6834.210
V8: 20.19.1
Sistema operativo: 13.2.152.41-electron.0

151

Same here:
Request ID: 802086bf-50fe-4410-be18-86d1d977d4ce
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7349:369901

152

After last update - same Issue
.

153

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Request ID: dfd27a3b-1060-4109-b2f4-cc0f559a4ae1

Error Message:ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472

Description:
When testing the runtime system in a C++ project, a serialization error occurs that interrupts the execution of AI assistant commands. The error appears specifically when attempting to run runtime tests (test_runtime.exe), while Cursor works normally in other cases.

Steps to Reproduce

  1. Open a C++ project with CMake
  2. Build the project using cmake --build build --config Release --target test_runtime
  3. Attempt to run the runtime test through the AI assistant: .\Release\test_runtime.exe
  4. The error occurs when trying to execute the test run command
  5. In other operations (editing, building, other tests) the error does not appear

Expected Behavior

The AI assistant should successfully execute runtime test commands without serialization errors.

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.3.5
VSCode Version: 1.99.3
Commit: 9f33c2e793460d00cf95c06d957e1d1b8135fad0
Date: 2025-07-30T00:32:27.448Z
Electron: 34.5.1
Chromium: 132.0.6834.210
Node.js: 20.19.0
V8: 13.2.152.41-electron.0
OS: Windows x64 10.0.26200

Additional Information

The error does not make Cursor completely unusable, but it interferes with runtime system testing, which is critical for development.

The error occurs only when attempting to run runtime tests
The project uses CMake and C++
The runtime test works when run manually through the command line
The problem is not related to internet connection
The error appears specifically when executing AI assistant commands related to testing

NEW!!!
Đ’ĐŸŃ‚ пДрДĐČĐŸĐŽ ĐœĐ° Đ°ĐœĐłĐ»ĐžĐčсĐșĐžĐč:

Additional information regarding the ConnectError:

Context of occurrence:
The error occurs exclusively when attempting to run compiled exe files through Cursor’s built-in terminal, not during normal code work.

Reproduction details:

  1. Creating a C++ project with an error handling system in Russian
  2. Compiling exe file through CMake
  3. When attempting to run test_error.exe through Cursor AI, getting serialization error
  4. The same exe file runs normally through regular cmd

Project content causing the error:

  • Error handling system with Russian messages
  • Error, ErrorManager, ErrorUtils classes
  • Output contains Unicode characters (emojis, Russian text)
  • Structured error messages with codes

Suspected causes:

  1. Unicode characters - Russian text and emojis in program output
  2. Complex data structures - Error objects with multiple fields
  3. Object serialization - Cursor attempting to serialize runtime data
  4. Encoding - UTF-8/UTF-16 issues when transmitting data

Temporary solution:
Running exe files through external cmd completely resolves the issue.

Question:
Is it possible to configure Cursor so that it doesn’t attempt to serialize exe file output, or is there a way to bypass this issue when working with programs containing Unicode characters?
Historical context:

  • This issue appeared recently - yesterday and before, similar exe files worked fine

  • Previously worked with Python projects without problems

  • Issue specifically emerged when working with C++ runtime system containing complex data structures

  • Suggests recent changes in Cursor’s serialization logic or increased sensitivity to certain data types

Comparison:

  • Python scripts: simple text output, no serialization issues

  • C++ exe files: complex objects, Unicode characters, structured error messages

  • Problem likely related to Cursor’s handling of compiled binary output vs interpreted language output

Does this stop you from using Cursor

Sometimes - I can sometimes use Cursor

155

PROBLEM SOLVED! :tada:

After solving two serialization cases in a C++ project, I’ve derived universal patterns:

:magnifying_glass_tilted_left: DIAGNOSTIC STRATEGY:

  1. Create minimal tests for each component
  2. Use step-by-step complexity addition
  3. Stop at the problematic component

:building_construction: ARCHITECTURAL PRINCIPLES:

  1. Avoid name conflicts (renaming)
  2. Use two-phase initialization for complex objects
  3. Separate responsibilities between components

:counterclockwise_arrows_button: SOLUTION CYCLE:
Problem → Diagnosis → Isolation → Analysis → Solution → Validation

These patterns will help solve similar issues in the future! :flexed_biceps:

#C++ #Serialization #Debugging #ProblemSolving

157

how and where did you solve what? I still have this issue

Request ID: cc5fe32a-8873-41de-9401-baa91736db2a
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7349:396794

1 Like
158

Still no fix to this issue?? Cursor is unusable to me on latest version(1.7.54)

1 Like
159

I get this error when I am testing with scripts that cursor runs automatically. My workaround is to tell it to let me run the scripts manually.

160

Request ID: 18bed53d-b996-4141-902b-b36e048b7233
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Users/Matt/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472

So we have an entire thread of people with this issue and Cursor has offered no support or solution other than occasionally posting that people should update to the latest version of the software, which does not fix the issue?

161

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Request ID: d1925574-1b36-4f02-bb15-998f51a9f691
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Users/beuve/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472

Steps to Reproduce

Request ID: d1925574-1b36-4f02-bb15-998f51a9f691
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Users/beuve/AppData/Local/Programs/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:373472

Screenshots / Screen Recordings

Capture d’écran 2025-10-28 122526.png
Capture d’écran 2025-10-28 122526.png559×986 12.6 KB

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 1.7.54 (user setup)
VSCode Version: 1.99.3
Commit: 5c17eb2968a37f66bc6662f48d6356a100b67be0
Date: 2025-10-21T19:07:38.476Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.19045

Does this stop you from using Cursor

Yes - Cursor is unusable

1 Like
162

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Request ID: 1abba708-ac31-4982-847d-0b11accd3fb1
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7337:396432

Steps to Reproduce

Use the agent mode with any model

Expected Behavior

no have serialisation error

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.34 (system setup)
VSCode Version: 1.99.3
Commit: 45fd70f3fe72037444ba35c9e51ce86a1977ac10
Date: 2025-10-29T06:51:29.202Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

Had it in previous version too

For AI issues: which model did you use?

Any

For AI issues: add Request ID with privacy disabled

1abba708-ac31-4982-847d-0b11accd3fb1

Does this stop you from using Cursor

No - Cursor works, but with this issue

163

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

After a few prompts this serialization issue popped up, no matter what I do I cannot continue the same chat, creating a new chat was the only option
I think there is a thread here with this issue that is going on for months now, please do prioritize this issue

Steps to Reproduce

It was very random, can pop up any time on the chat after a few prompts

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.40 (system setup)
VSCode Version: 1.99.3
Commit: a9b73428ca6aeb2d24623da2841a271543735560
Date: 2025-10-30T04:12:35.564Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26200

For AI issues: which model did you use?

Composer 1

For AI issues: add Request ID with privacy disabled

Request ID: d76548a6-1516-4c96-b2ad-52dc2c5f8c9f
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:7338:396432

Does this stop you from using Cursor

No - Cursor works, but with this issue

164

Build very explicit guardrails and .mdc rules to prevent that freaking notorious “memory-drift” Cursor is famous for - then suddenly, BAM - locked up tighter than Dicks Hat Band - still locked out.

You either fix memory drift and hallucinations that Cursor now has a reputation for, or fix this error.

165

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

Connection failed. If the problem persists, please check your internet connection or VPN

Request ID: 76fd1522-6f64-41db-a072-8fad9fe18203
ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools
at vscode-file://vscode-app/c:/Program%20Files/cursor/resources/app/out/vs/workbench/workbench.desktop.main.js:4984:396432

Steps to Reproduce

  1. Open Cursor IDE.
  2. Create a new chat with the agent in “Auto” mode.
  3. Type any normal request (for example: “generate some Python code”).
  4. After a few seconds, the error appears: “Connection failed. If the problem persists, please check your internet connection or VPN.”
  5. Tested on different networks (Wi-Fi, mobile data) and the problem still occurs.

Expected Behavior

The agent should process the request and return the response normally, without losing the connection or showing the “Connection failed” error.

  • The problem happens when “Auto” mode and with single agent selected

  • Internet: tested with and without VPN

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.43 (system setup)
VSCode Version: 1.99.3
Commit: 8e4da76ad196925accaa169efcae28c45454cce0
Date: 2025-10-30T18:49:27.589Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26200

Does this stop you from using Cursor

Yes - Cursor is unusable

166

ok, heres a solution that INSTANTLY solved it. Seems like the ISP is blocking or slowing something down with cursor specifically. As soon as I used a VPN, instantly all requests went through normally. So even though cursor throws that VPN error, turns out USING the VPN is what solves it. The ISP might have some rules in place that inteferes with cursor. .

1 Like
167

I’ll test it and see what I can find out, then I’ll report back.

Thanks!

168

Where does the bug appear (feature/product)?

Cursor IDE

Describe the Bug

After a fresh launch or sign-in + sending prompt, streams start then freeze after ~10–30s. The UI shows:
“Connection failed. If the problem persists, please check your internet connection or VPN.”
From that point, all Ask/Agent chats fail until I fully restart Cursor. This repeats reliably.
Error surfaced in console/banner:

ConnectError: [internal] Serialization error in aiserver.v1.StreamUnifiedChatRequestWithTools

This happens on a home network with no VPN/proxy. Other LLM apps (ChatGPT, Perplexity, etc.) work fine on the same machine.
HTTP2 or HTTP1.1 makes no difference.

Steps to Reproduce

  1. Launch Cursor (fresh).
  2. Send any prompt in Ask or Agent using any provider/model.
  3. Tokens begin to stream for ~10–30s, then freeze; UI shows “Connection failed” and subsequent requests won’t stream until a full app restart.

Expected Behavior

Streaming responses should complete without freezing, and the app should remain usable for subsequent chats without requiring a full restart. This worked flawlessly in Cursor 1.0.

Operating System

Windows 10/11

Current Cursor Version (Menu → About Cursor → Copy)

Version: 2.0.43 (user setup)
VSCode Version: 1.99.3
Commit: 8e4da76ad196925accaa169efcae28c45454cce0
Date: 2025-10-30T18:49:27.589Z
Electron: 34.5.8
Chromium: 132.0.6834.210
Node.js: 20.19.1
V8: 13.2.152.41-electron.0
OS: Windows_NT x64 10.0.26100

For AI issues: which model did you use?

Anthropic: Claude 4.5 Sonnet
OpenAI: GPT-5

For AI issues: add Request ID with privacy disabled

Request ID: 31af217e-292b-474e-8ae5-dd0857996380

Additional Information

Diagnostics (Settings → Network → Run Diagnostics): All PASS

Tried (no change):

Toggled HTTP/2 on/off; tested both Ask and Agent

Switched providers/models

Full sign out/in; app restart

Deleted local state: %APPDATA%\Cursor\User\globalStorage\state.vscdb* and workspaceStorage\ (restored since it didn’t help and I have many settings/chats)

No system proxy; no VPN; other LLM apps stream normally

Impact: Paying customer; this currently makes Cursor unusable for any chat/agent work.

Does this stop you from using Cursor

Yes - Cursor is unusable