rsigma-lsp

rsigma-lsp is a Language Server Protocol (LSP) server that brings real-time Sigma rule development support to any editor — VSCode, Neovim, Helix, Zed, Emacs, and more. Built on the same parser, linter, and compiler as the CLI.

This binary is part of rsigma.

Installation

cargo install --path crates/rsigma-lsp

LSP Capabilities

Capability	Details
Text document sync	Full (entire document on every change)
Diagnostics	Lint (65 rules), parse errors, compile errors
Code actions	Quick-fix actions for auto-fixable lint warnings
Completions	Context-aware; trigger characters: |, :, , \n
Hover	Field modifiers, MITRE ATT&CK tactics and techniques
Document symbols	Hierarchical outline of rule structure

Diagnostics

Diagnostics run through three layers, each adding errors from a different stage:

Layer 1 — Lint

Runs all 65 lint rules from rsigma-parser (Sigma spec v2.1.0). Loads .rsigma-lint.yml config from ancestor directories and respects inline # rsigma-disable comments.

Lint severity	LSP severity
Error	DiagnosticSeverity::ERROR
Warning	DiagnosticSeverity::WARNING
Info	DiagnosticSeverity::INFORMATION
Hint	DiagnosticSeverity::HINT

Diagnostic code: the lint rule name (e.g. missing_title, invalid_level).

Layer 2 — Parse errors

YAML and condition expression parse failures from rsigma-parser.

Severity	ERROR
Code	parse_error
Range	Extracted from "at line X column Y" in the error message, or falls back to the first content line

Layer 3 — Compile errors

Per-rule compilation errors from rsigma-eval (unknown selections, invalid modifier combos).

Severity	ERROR
Code	compile_error
Range	For "unknown detection identifier: X", highlights X in the condition: line; otherwise falls back to /detection/condition

All diagnostics have source: "rsigma".

Timing

Event	Behavior
Document open	Diagnostics run immediately
Document change	Diagnostics debounced at 150 ms
Document save	Diagnostics run immediately
Document close	Pending diagnostics aborted; existing diagnostics cleared

Code Actions

Quick-fix code actions for lint warnings with auto-fix suggestions. When the cursor is on a diagnostic that has a safe fix, the editor offers a one-click action to apply it.

Fixable rule	Action
non_lowercase_key	Rename key to lowercase
logsource_value_not_lowercase	Lowercase the value
invalid_status	Replace with closest valid status
invalid_level	Replace with closest valid level
unknown_key	Rename to closest known key (typo correction)
duplicate_tags	Remove duplicate tag entry
duplicate_references	Remove duplicate reference entry
duplicate_fields	Remove duplicate field entry
all_with_re	Remove redundant |all modifier
single_value_all_modifier	Remove redundant |all modifier
wildcard_only_value	Replace with |exists: true
filter_has_level / filter_has_status	Remove the field

All code actions are marked as quickfix with isPreferred: true. Only Safe disposition fixes are offered.

Completions

Context-aware completions triggered by |, :, (space), and newline. Contexts are evaluated in priority order:

1. Modifier completions

Trigger: | character in the current line.

Offers all 25 field modifiers matching the typed prefix, with descriptions. Completion kind: ENUM_MEMBER.

2. Tag completions

Trigger: Inside the tags section, on a line starting with - .

Offers all 14 MITRE ATT&CK tactic tags (attack.initial_access, attack.execution, ...) plus extra tags:

• cve.
• detection.dfir
• detection.emerging_threats
• detection.threat_hunting
• tlp.white, tlp.green, tlp.amber, tlp.red

Completion kind: VALUE.

3. Condition completions

Trigger: Line starts with condition: or cursor is within the condition section.

Offers:

• Selection names extracted from the current rule's detection section (kind: VARIABLE)
• Condition keywords: and, or, not, 1 of, all of, 1 of them, all of them (kind: KEYWORD)

4. Value completions

Trigger: After : for known keys.

Key	Offered values
status	stable, test, experimental, deprecated, unsupported
level	informational, low, medium, high, critical
product	windows, linux, macos, aws, azure, gcp, m365, okta, github
category	27 values (process_creation, file_event, network_connection, image_load, registry_event, dns_query, file_access, file_change, file_delete, file_rename, driver_load, pipe_created, process_access, process_tampering, process_termination, ps_classic_start, ps_module, ps_script, registry_add, registry_delete, registry_set, sysmon_error, sysmon_status, wmi_event, clipboard_capture, create_remote_thread, create_stream_hash)
service	20 values (sysmon, security, system, powershell, powershell-classic, taskscheduler, wmi, application, dns-server, driver-framework, firewall-as, ldap_debug, msexchange-management, ntlm, openssh, printservice-admin, printservice-operational, smbclient-security, terminalservices-localsessionmanager, windefend)

Completion kind: ENUM_MEMBER.

5. Top-level key completions

Trigger: Indent level 0, no : on the line.

Offers all 17 top-level keys with snippet placeholders: title, id, related, status, description, references, author, date, modified, tags, logsource, detection, falsepositives, level, fields, correlation, filter.

Completion kind: PROPERTY. Insert format: SNIPPET (with $0, $1, etc.).

6. Logsource sub-key completions

Trigger: Inside logsource section, indent > 0, no :.

Offers: category, product, service, definition.

7. Detection sub-key completions

Trigger: Inside detection section, indent > 0, no :.

Offers: selection, filter, condition.

Hover

Hover provides documentation at the cursor position. The server checks (in priority order):

MITRE ATT&CK techniques

Pattern: attack.t* (e.g. attack.t1059, attack.t1059.001).

Shows technique ID as a heading with a link to https://attack.mitre.org/techniques/{id}.

MITRE ATT&CK tactics

Any of the 14 tactic names (e.g. attack.execution, attack.persistence).

Shows the tactic description.

Field modifiers

Any of the 25 modifier names (e.g. contains, base64, windash).

Shows the modifier name and description in Markdown.

Document Symbols

Provides a hierarchical outline of the rule structure:

Symbol	Kind	Condition
title	STRING	When present
logsource	NAMESPACE	When present
correlation	NAMESPACE	When present
detection	NAMESPACE	When present; includes child symbols

Detection children

Child keys within detection at the first indented level:

Key	Kind
condition	BOOLEAN
Other keys (selections)	FIELD

Each child has a range (full section) and selection_range (key line only).

Document Lifecycle

Event	Behavior
textDocument/didOpen	If .yml/.yaml: run diagnostics immediately, store document
textDocument/didChange	Full sync (entire document replaced). If Sigma file: schedule debounced diagnostics (150 ms)
textDocument/didSave	If Sigma file: run diagnostics immediately (no debounce)
textDocument/didClose	Abort pending diagnostics, remove document, publish empty diagnostics to clear

Only .yml and .yaml files trigger diagnostics. Non-Sigma files are stored for document state but produce no diagnostics.

Error Recovery

All handler functions (completion, hover, document_symbol, diagnostics) are wrapped in catch_unwind. On panic:

• An error is logged.
• Completions return empty; hover returns None; symbols return empty; diagnostics return empty.
• The server continues operating.

If a document URI is not found in the store, handlers return None or empty results.

Editor Setup

Neovim (native LSP)

vim.api.nvim_create_autocmd('FileType', {
  pattern = 'yaml',
  callback = function()
    vim.lsp.start({
      name = 'rsigma-lsp',
      cmd = { 'rsigma-lsp' },
    })
  end,
})

VSCode / Cursor

A thin extension wrapper is provided in editors/vscode/. To use it:

cd editors/vscode
npm install
npm run package              # builds with esbuild + creates .vsix
code --install-extension rsigma-0.1.0.vsix    # VSCode
cursor --install-extension rsigma-0.1.0.vsix  # Cursor

The extension launches rsigma-lsp from your $PATH by default. Override via the rsigma.serverPath setting.

Helix (~/.config/helix/languages.toml)

[language-server.rsigma-lsp]
command = "rsigma-lsp"

[[language]]
name = "yaml"
language-servers = ["yaml-language-server", "rsigma-lsp"]

Debugging

Set the RUST_LOG environment variable to enable logging:

RUST_LOG=rsigma_lsp=debug rsigma-lsp

Log messages include initialization, diagnostics errors, and handler panics.

License

MIT License.