7.23. watchdog — Program Supervisor

One supervisor for any daslang program that needs to stay up. It restarts the child with bounded backoff, captures crashes into bundles, reports startup progress, and polls health. In-tree it supervises utils/dasllama-server (JIT) and the telegram dictation example (a baked exe).

It ships as a static executable, bin/watchdog (bin/Release/watchdog.exe in an MSVC tree): a standalone context on the full runtime that compiles nothing at run time, loads no shared module, and holds no lock on any file a deploy replaces. The same code runs under the interpreter for development.

7.23.1. Quick start

In a deployed bundle, beside the program:

./watchdog

From the source tree, point it at the program’s directory:

bin/watchdog --cwd utils/dasllama-server

or, under the interpreter:

daslang utils/watchdog/main.das -- --cwd utils/dasllama-server

What to supervise resolves in order, first match winning: command-line flags (--program, --script, --name, …); watchdog.json beside the executable (each key is a flag name with underscores and sets the default for that flag; unknown keys are a hard error); layout discovery (main.das beside bin/Release/daslang → daslang -jit main.das; exactly one program → that program, where a program is a *.exe file - a flat daspkg release bundle keeps the suffix on Linux too - or, on a Unix layout, an executable file with no extension, which is how the macOS .app names its exe; the watchdog’s own executable never counts; a main.das with no daslang in reach is refused, never traded for a program; anything ambiguous is an error, never a guess). Everything after -- goes to the child.

--tray (the tray key in watchdog.json) puts a status icon in the notification area: a mark badged by state, the status line as its tooltip and the menu’s first row, Open <name> for the page named by --tray-url (or the health URL’s origin), live while the health check is green, and Shutdown. --tray-icon <file> (the tray_icon key) replaces the stock disc with the program’s own mark - a PNG, or an ICO whose frames are PNG-compressed, square, up to 256 px - and the badge is drawn over it; a file it cannot use is logged as tray_icon_unavailable with the reason and the disc shows. Where no desktop can show an icon, the log says tray_unavailable and supervision runs without it.

7.23.2. Serving an editor or an assistant

-tool <name> starts the server an editor or an AI assistant talks to over stdio. The package managers put the watchdog on PATH as daslang-watchdog:

daslang-watchdog -tool mcp     # the daslang MCP server
daslang-watchdog -tool dap     # the DAP bridge for debugging
daslang-watchdog -tool lsp     # the language server

mcp and dap run daslang -tool <name> with the daslang beside the watchdog, and restart it after a crash or a rebuild; lsp is the watchdog’s own language-server front. The directory the client starts it in is the project root, or pass --cwd <dir> before -tool. Arguments after the name go to the server. An MCP client’s configuration needs no path:

{ "command": "daslang-watchdog", "args": ["-tool", "mcp"] }