Supported Languages

Defined in src/judge/languages.toml, registered in Postgres via /v1/languages. On startup the judge maps DB IDs to local configs by name. Typo in either place = compile failures for everyone. Fun afternoon.

Runtimes

Language	Version	Ext	Notes
C++	13.2.0	.cpp	g++ -O2
C	13.2.0	.c	gcc -O2
Python	3.12	.py	interpreted
PyPy	3.9.18	.py	same ext as Python, different ID
Java	21.0.3	.java	512 MB heap, renames file if class ≠ filename
JavaScript	21.6.2	.js	Node
TypeScript	5.4.5	.ts	tsc → Node
Go	1.24.11	.go	module cache mounts, 2 cores at compile
Rust	1.78.0	.rs	rustc
Ruby	3.2.3	.rb
Lua	5.4.6	.lua
Kotlin	1.9.24	.kt	JVM, InputKt.class entry
Haskell	9.4.7	.hs	GHC

Time/memory limits come from the problem, not this table. Defaults are usually 5 to 10s CPU and 256 to 512 MB unless you override on create.

Execution

Everything through nsjail. Judge service for the gory details.

languages.toml

Each block needs name, version, extension, and script. The script runs at compile time and must produce /executable/main. {IN_FILE} is the source path placeholder.

Add a language

1. Install toolchain in Dockerfile.newbase
2. Write build script, test it in isolation if you can
3. Rebuild judge image
4. POST /v1/languages
5. Submit a known AC solution. If step 5 fails, fix step 2 before blaming the algorithm.

Gotchas (read before your first contest)

Java: public class name must match filename, or the judge renames the file for you.

Go: first submission after cold start is slow (module download). Warm the cache or warn contestants.

TypeScript / Kotlin: compile errors show as COMPILE_TIME_ERROR, not runtime. Read stderr.

Python vs PyPy: same .py extension, different language IDs. Pick deliberately.

Output comparison: line-by-line, trimmed. "42\n" vs "42" can matter if you’re not printing newlines. Classic.