ElegantUVM

Free, open-source, UVM-aware SystemVerilog support for VS Code, built on the slang compiler front end.

• One-click class graph. Click the graph button in the editor title bar (or press Ctrl+Alt+G). You get inheritance, composition, factory creates and overrides, with UVM roles (driver, monitor, agent, …) recognised automatically.
• Component topology. The uvm_test_top tree for any test, built from type_id::create() calls. Factory overrides are applied, conditional components are marked, and TLM connect() calls are drawn.
• config_db cross-reference. Every set and get, matched by field and type. A get that nothing sets, or a set/get type mismatch, is flagged in the editor.
• Navigation that understands UVM. Go to definition, hover, completion, references, type hierarchy and document/workspace symbols. Navigation follows type parameters (req in a driver resolves to your item class), virtual interfaces, clocking blocks and extern methods.
• UVM lint. Factory registration and creation, constructor compatibility, phase calls and config_db checks, with lightbulb fixes and source waivers (details below).
• Elaboration diagnostics. slang compiles and elaborates the whole design in a background process when you save (uvm.elaboration), and reports what a simulator's elaboration would: type errors, unknown members, wrong argument counts, missing modules or packages. Errors raised inside a macro point at your code, not the macro. Errors the UVM library reports on its own are left out, while errors your code causes inside it (a constructor without a parent, a wrong type parameter) are reported, pointing at your type. The status bar shows the result; UVM: Elaborate Now runs it on demand.
• MCP server for agents. The extension registers python -m uvmls mcp with VS Code (MCP: List Servers shows "UVM Language Server"), so Copilot and other agents in the editor can ask the same index: classes by UVM role, a test's topology with its factory overrides applied, the effective type of every create, config_db sets and gets with their status, lint, slang elaboration, definition, hover, signature help, sequences and their start sites. It runs as a separate process on the first workspace folder with the uvm settings as its flags and reads the files on disk (unsaved editor text is not visible); it is read-only and refuses paths outside the workspace. uvm.mcp.enabled turns it off. The same command works without VS Code, for Claude Code or Claude Desktop.

Install

Python 3.11 or newer is needed; on first start the extension offers to create its own environment with pyslang and pygls (Set Up…, then Install automatically), or set uvm.pythonPath. Trust the folder when VS Code asks: the extension starts a Python process, so it stays disabled in Restricted Mode. On Debian and Ubuntu install python3-venv first. The Linux x86_64 package installs from the wheels it ships (Python 3.11 to 3.14), with no network access; elsewhere uvm.pipArgs passes a mirror or proxy to pip. Tested on Linux x86_64 (Remote-SSH and WSL included); on macOS and Windows the generic package is expected to work but is not yet tested, and Verible is not bundled there (set uvm.formatter.path). No telemetry: nothing is collected or sent. Free and open source under the Apache License 2.0; sources, issues and the CLI/MCP documentation are on GitHub.

Quick fixes and UVM lint

Use the lightbulb or Quick Fix… (Ctrl+.) on a finding. The eleven checks are create-unregistered, utils-mismatch, create-no-parent, create-virtual, unknown-base, config-db-no-set, config-db-type-mismatch, factory-ctor, create-new, utils-param and phase-no-super. Optional or conditional config_db gets with no set are informational; required gets are warnings. A dynamic field name in a set suppresses the no-set check. Matching is static and cannot resolve every runtime scope or value.

Four of them need a word of explanation:

• factory-ctor: a registered class cannot accept its factory's constructor calls (error); add a compatible constructor or an object's missing name default when possible. The selected UVM library and defines determine the required calls.
• create-new: direct new(name, parent) bypasses the factory for a registered project component (warning); change it to type_id::create.
• utils-param: used specializations collide under name registration, or a non-parameterized test uses param-utils without registering its name (warning); change the registration macro.
• phase-no-super: a nonempty build_phase or connect_phase skips work in a project base class (warning). A super fix is offered only when the base phase and every method it calls are fully visible and read no configuration. Configuration reads or calls with unknown bodies withhold the fix entirely; the warning remains. These fixes are never preferred by Auto Fix.

Other fixes register a class, swap object/component utils, supply a missing parent, correct a config_db field typo or compatible type, and show the field in the cross-reference. Virtual-class and unknown-base findings currently offer only Ignore. Supported slang “did you mean” diagnostics can replace a misspelling. A missing-include action adds to uvm.includeDirs with status-bar feedback, leaving simulator filelists unchanged: one candidate is preferred, two or three offer a choice, and more than three offer none.

Fixes check current text and do not edit macro-generated code or library files. A registration fix can edit another workspace file, named in its title. Saving those edits is controlled by the editor; check files.refactoring.autoSave for background edits and save any buffers left dirty.

Fix all N 'code' problems in this file appears when at least two findings of that code have safe fixes. Source Action… → Fix all auto-fixable UVM problems (source.fixAll.uvm) applies safe fixes across codes in the current file. Only safe registration, missing-parent, constructor and utils-mismatch fixes qualify; an object-to-component registration change still needs individual review. Factory rewrites, param-utils changes, phase calls, config_db/typo fixes, include settings and Ignore are excluded. Another pass can expose a fix hidden by the first problem.

Enable safe fixes on an explicit save with:

{
  "editor.codeActionsOnSave": {
    "source.fixAll.uvm": "explicit"
  }
}

Every UVM finding can offer Ignore 'code' on this line. For example:

m = mon::type_id::create("m"); // uvm-lint: ignore create-no-parent

Use the diagnostic code, with commas between multiple codes. After code the directive applies to that line; on its own line it applies to the next line containing code, skipping blank lines and comments. Preprocessor directives count as code; this is not a block-wide waiver. uvmls lint honours the same directive. slang parse and elaboration errors cannot be waived this way.

Point uvm.filelists at the same .f files your simulator uses, or leave it empty and every SystemVerilog file in the workspace is indexed with include paths inferred; simulator output folders such as work/ are skipped, and uvm.exclude leaves out more. The UVM library comes from uvm.uvmHome when set, else from $UVM_HOME, else from the project's own uvm_pkg.sv when it compiles one, and otherwise from the Accellera UVM 1.2 that ships with the extension. Turn off uvm.useBundledUvm to use a lightweight built-in UVM model instead.

Syntax highlighting for SystemVerilog and Verilog is built in (the grammars of the Verilog-HDL/SystemVerilog extension, MIT), with UVM-specific highlighting injected on top. If that extension is installed as well, both grammars are the same and either one applies. With Verible installed, set "verible.arguments": ["--rules_config_search"] to keep its style warnings about the bundled UVM sources out of Problems: the extension ships a .rules.verible_lint that turns Verible's lint off for them, and your own files keep Verible's defaults.

The bundled UVM 1.2 is Accellera's, under the Apache License 2.0. Its LICENSE.txt and NOTICE.txt are in server/uvmls/third_party/uvm-1.2/ inside the extension. The SystemVerilog and Verilog grammars in syntaxes/ are from the Verilog-HDL/SystemVerilog extension 1.29.0 (MIT; third_party/verilog-hdl-LICENSE). The npm packages bundled into the extension's JavaScript are listed with their licence texts in THIRD_PARTY_NOTICES.txt: elkjs, under the Eclipse Public License 2.0 (source code at https://github.com/kieler/elkjs), the vscode-languageclient packages (MIT), semver and minimatch (ISC), and brace-expansion and balanced-match (MIT).