Serena fails to perfrom simple rename_symbol taks

[IvanKablar]

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Serena MCP rename_symbol fails silently, requires manual fallback

Description

The rename_symbol operation in Serena MCP Server is failing to perform actual renames, despite reporting success. When attempting to rename a Java class symbol, the operation claims success but renames 0 files, requiring
immediate fallback to manual shell commands.

Steps Executed

1. Use find_symbol to locate a class symbol (e.g., CameraActivity in a Java file)
2. Call rename_symbol with the found symbol to rename it to a new name (e.g., MyCameraActivity)
3. Observe the result

Expected Behavior

The rename_symbol operation should:

• Rename the symbol in all files where it appears
• Rename the file itself if it's a class definition
• Report the actual number of files modified
• Complete the operation without requiring fallback mechanisms

Actual Behavior

✓ rename_symbol (serena MCP Server)
{"name_path":"CameraActivity","relative_path":"app/src/main/java/com/example/biofotoapp/CameraActivity.java","new_name":"MyCameraActivity"}

 Successfully renamed 'CameraActivity' to 'MyCameraActivity' in 0 file(s)

The operation reports success but indicates 0 files were modified. The system then had to fall back to:

1. Manual mv shell commands (first attempt even had a path typo)
2. Manual text search showing 17 remaining references to the old name

Impact

This makes the rename_symbol feature unreliable and forces users/agents to manually handle renames through multiple fallback steps, defeating the purpose of having a dedicated rename operation.

Environment

• MCP Server: Serena
• CLI: Gemini CLI
• Language: Java
• File type: .java class file

[IvanKablar]

I am sorry to write this, but all my tests with Gemini CLI and Serena were disappointing. Even though you mention that Serena integrates with Gemini CLI, this is, at least with the current development status, not true.

[MischaPanch]

The rename_symbol tool was added recently, so it has been tested less in the wild and might have rough edges. We redirect the call directly to the language server, which for Java is eclipse. I guess it doesn't really do what it should. We should in particular not claim success if the renaming happened in 0 files. We will look into what is happening here for Java.

Regarding the integration with Gemini, could you say a few words on what did not work and what disappointed you? Serena is not a paid product, we and the community contributors are generally working on improving it. There are tons of clients, languages, situations and configurations, so sometimes things work better and sometimes worse. A general comment about disappointing performance in one of these many cases doesn't really help - but with more specifics it is often possible to resolve issues quickly. We (the dev team) work mostly with Claude Desktop, VSC, Codex or Claude Code, so we haven't tested Serena in Gemini CLI ourselves (though we know that people to use it there).

[opcode81]

The Java language server is notoriously problematic, so using Serena with Java is understandably not the best experience, unfortunately.

On the bright side, we will soon release the Serena JetBrains extension, which will give you excellent support for all languages supported by JetBrains IDEs, including Java.