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Serena

An MCP toolkit that gives coding agents IDE-grade powers — symbol-level retrieval and editing via language servers, across 40+ languages.

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Updated Jun 11, 2026
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Serena (MIT, ~25k stars) is 'the IDE for your agent': an MCP server backed by language servers giving agents symbol-level tools — find symbol, find references, replace symbol body, rename — across 40+ languages. Precise, token-efficient edits at the symbol level instead of regex surgery, plus a project memory for cross-session knowledge.

Serena's tagline — "the IDE for your agent" — is accurate. Where coding agents normally navigate by text search, Serena plugs language servers underneath and exposes symbol-level tools: find this function, list every reference to it, replace exactly its body, rename it everywhere. On a large codebase, that's the difference between surgical edits and regex archaeology.

Highlights

  • Symbolic retrieval — find symbol, file symbol overview, find referencing symbols, diagnostics: the agent locates code by meaning, not string-matching.
  • Symbolic editing — replace symbol body, insert before/after symbol, safe deletes, and LSP-powered rename refactoring.
  • 40+ languages — Python, TypeScript/JS, Java, C/C++, C#, Go, Rust, Ruby, PHP, Swift, Kotlin, Elixir, and more via the LSP backend.
  • Token-efficient by design — symbol overviews and targeted reads keep big-repo work inside a sane context budget.
  • Project memory — a cross-session knowledge store, so what the agent learns about the codebase persists.
  • Contexts and modes — --context claude-code, ide-assistant, and others tune the toolset to the host; stdio or HTTP transport.

In an AI-assisted workflow

uv tool install -p 3.13 serena-agent
serena init
claude mcp add --scope user serena -- serena start-mcp-server \
  --context claude-code --project-from-cwd
# then:
# > Find every caller of resolveSession, then rename it to resolveUserSession
# > and update the call sites — use Serena's symbol tools

It shines on exactly the work the refactoring-specialist agent does: cross-cutting renames, signature changes, dead-code sweeps — now with reference-accurate ground truth instead of grep confidence.

TIP

Slow first start? Language servers take a moment to warm up on big repos — launch with MCP_TIMEOUT=60000 claude and let serena init's indexing finish once per project.

Good to know

MIT, Python-based (installed via uv; PyPI package serena-agent), v1.0 landed April 2026 with the streamlined install flow. Inside Claude Code, Serena's generic file/shell tools are deliberately disabled — its value there is purely the symbolic layer. The optional JetBrains-plugin backend (paid, free trial) unlocks IDE-exclusive operations: move/inline refactorings, type hierarchies, and interactive debugging.

Frequently asked questions

What does Serena add that Claude Code doesn't have?
Symbol-level semantics. Claude Code's built-in search and edit work on text; Serena works on the language server's understanding — find a symbol, list everything referencing it, replace exactly its body, rename it project-wide. On large codebases that's both more precise and more token-efficient than reading whole files to locate one function.
How do I add Serena to Claude Code?
Install once: uv tool install -p 3.13 serena-agent && serena init. Then globally: claude mcp add --scope user serena -- serena start-mcp-server --context claude-code --project-from-cwd, or per-project with --project "$(pwd)". The --context claude-code flag tunes its toolset for the harness (its generic file/shell tools stay disabled to avoid overlap).
Is Serena free?
Yes — MIT core with the free LSP backend covering 40+ languages. The optional JetBrains-plugin backend (which adds IDE-exclusive operations like move/inline refactorings and interactive debugging) is a paid plugin with a free trial.

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