README.md

daslang MCP Server

A Model Context Protocol (MCP) server that exposes 28 daslang compiler-backed tools to AI coding assistants like Claude Code — compilation diagnostics, program introspection, AOT generation, live-reload control, and more.

Tools

Compiler & Introspection

Tool	Description
compile_check	Compile a .das file and return errors/warnings plus a categorized function listing on success. Optional json for structured output
list_functions	Compile a .das file and list all user functions, class methods, and generic instances (after macro expansion)
list_types	Compile a .das file and list all structs, classes (with fields), enums (with values), and type aliases
run_test	Run dastest on a .das test file and return pass/fail results. Optional json for structured output
format_file	Format a .das file using daslib/das_source_formatter
run_script	Run a .das file or inline code snippet and return stdout/stderr
ast_dump	Dump AST of an expression or compiled function. mode=ast returns S-expression (node types/fields), mode=source returns post-macro daslang code. Optional lineinfo to include file and line:col spans on each node
program_log	Produce full post-compilation program text (like options log). Shows all types, globals, and functions after macro expansion, template instantiation, and inference. Optional function filter
list_modules	List all available daslang modules (builtin C++ modules and daslib). Optional json for structured output
find_symbol	Cross-module symbol search (functions, generics, structs, handled types, enums, globals, typedefs/aliases, fields). Case-insensitive substring by default; =query for exact match
list_requires	Compile a .das file and list all require dependencies (direct and transitive), with source file paths and builtin annotations. Optional json for structured output
list_module_api	List all functions, types, enums, and globals exported by a builtin or daslib module (e.g. math, strings, fio, daslib/json). Optional compact mode for large modules
convert_to_gen2	Convert a .das file from gen1 (indentation-based) syntax to gen2 (braces/parentheses) using das-fmt. Optional inplace flag to modify the file directly
goto_definition	Given a cursor position (file, line, column), resolve the definition of the symbol under the cursor. Returns location, kind (variable/function/field/builtin/struct/enum/typedef), and source snippet. Optional no_opt to preserve pre-optimization AST
type_of	Given a cursor position (file, line, column), return the resolved type of the expression under the cursor. Shows all expressions at position from innermost to outermost. Optional no_opt
find_references	Find all references to the symbol under the cursor (function calls, variable uses, field accesses, type refs, enum/bitfield values, aliases). Works from both usage and declaration sites. Scope: file (default) or all (all loaded modules). Optional no_opt
eval_expression	Evaluate a daslang expression and return its printed result. Supports comma-separated module imports via require parameter
describe_type	Describe a type's fields, methods, values, and base type. Supports structs, classes, handled types, enums, bitfields, variants, tuples, typedefs
grep_usage	Parse-aware symbol search across .das files using ast-grep + tree-sitter. Finds identifier occurrences excluding comments and strings. Conditional on sg CLI
outline	List all declarations (functions, structs, classes, enums, bitfields, variants, globals, typedefs) in a file or set of files using tree-sitter. Works on broken/incomplete code — no compilation needed. Conditional on sg CLI
aot	Generate AOT (ahead-of-time) C++ code for a .das file or a single function. Without function, returns full AOT output. With function, extracts that function's C++ only. Overloaded names return a disambiguation list with mangled names for exact selection

Live-Reload Control

These tools interact with a running daslang-live.exe instance via its REST API (default port 9090). All accept an optional port parameter.

Tool	Description
live_launch	Start a daslang-live instance with a script file. Sets working directory to the script's folder. Detects if already running. Polls up to 10 seconds to confirm startup
live_status	Get status (fps, uptime, paused, dt, has_error)
live_error	Get last compilation error (null if none)
live_reload	Trigger reload. Optional full param for full recompile. Works even during compilation errors
live_pause	Pause or unpause (paused = "true"/"false"). Returns 503 on compilation error
live_command	Dispatch a [live_command] (name required, optional args JSON string). Returns 503 on compilation error. Use name="help" to list all commands
live_shutdown	Graceful shutdown of the live instance

Server Management

Tool	Description
shutdown	Shut down the MCP server itself. Claude Code auto-restarts it, picking up code changes to .das tool files. Tool registration changes require a manual restart

Setup

No extra build dependencies — the MCP server uses stdio transport. Claude Code manages the process lifecycle automatically.

# Manual test (Windows):
bin/Release/daslang.exe utils/mcp/main.das

# Manual test (Linux):
./bin/daslang utils/mcp/main.das

Configure in .mcp.json (project root):

// Windows
{
  "mcpServers": {
    "daslang": {
      "command": "bin/Release/daslang.exe",
      "args": ["utils/mcp/main.das"]
    }
  }
}

// Linux
{
  "mcpServers": {
    "daslang": {
      "command": "./bin/daslang",
      "args": ["utils/mcp/main.das"]
    }
  }
}

Or add via CLI:

# Windows
claude mcp add daslang -- bin/Release/daslang.exe utils/mcp/main.das

# Linux
claude mcp add daslang -- ./bin/daslang utils/mcp/main.das

Claude Code starts and stops the server automatically with each session.

Architecture

• Each tool invocation runs in a separate thread (new_thread) with its own context/heap — when the thread ends, its memory is freed without GC
• Exception: live_* tools run on the main thread (they use system() and sleep() which don't work well from new_thread)
• Protocol logic lives in protocol.das, the entry point is main.das
• Heap is collected after each request when over threshold (1 MB)
• Tool handlers are modular: each tool lives in tools/*.das, shared utilities in tools/common.das

Configuring Claude Code

Optionally, allow the MCP tools without prompting by adding to .claude/settings.json:

{
  "permissions": {
    "allow": [
      "mcp__daslang__compile_check",
      "mcp__daslang__list_functions",
      "mcp__daslang__list_types",
      "mcp__daslang__run_test",
      "mcp__daslang__format_file",
      "mcp__daslang__run_script",
      "mcp__daslang__ast_dump",
      "mcp__daslang__list_modules",
      "mcp__daslang__find_symbol",
      "mcp__daslang__list_requires",
      "mcp__daslang__list_module_api",
      "mcp__daslang__convert_to_gen2",
      "mcp__daslang__goto_definition",
      "mcp__daslang__type_of",
      "mcp__daslang__find_references",
      "mcp__daslang__program_log",
      "mcp__daslang__eval_expression",
      "mcp__daslang__describe_type",
      "mcp__daslang__grep_usage",
      "mcp__daslang__outline",
      "mcp__daslang__aot",
      "mcp__daslang__live_launch",
      "mcp__daslang__live_status",
      "mcp__daslang__live_error",
      "mcp__daslang__live_reload",
      "mcp__daslang__live_pause",
      "mcp__daslang__live_command",
      "mcp__daslang__live_shutdown",
      "mcp__daslang__shutdown"
    ]
  }
}

After creating/editing these files, restart Claude Code (or start a new session) for it to pick up the MCP server.

ast-grep / tree-sitter setup

The grep_usage and outline tools use ast-grep (sg CLI) with a custom tree-sitter grammar for daslang. The sgconfig.yml config file is platform-specific (shared library extension differs), so it is gitignored.

Copy the appropriate template to sgconfig.yml in the project root:

# Windows
cp sgconfig.yml.windows sgconfig.yml

# Linux
cp sgconfig.yml.linux sgconfig.yml

# macOS
cp sgconfig.yml.osx sgconfig.yml

How It Works

The server implements the MCP protocol via JSON-RPC 2.0 over stdio, handling initialize, tools/list, tools/call, and ping.

• Reads newline-delimited JSON (NDJSON) from stdin
• Writes JSON-RPC responses to stdout (one line per message)
• Logs to stderr and to utils/mcp/mcp_server.log

File paths passed to tools are resolved relative to the server's working directory.