Programming languages in the judge image and how to add or customize language support.
Languages are defined in src/judge/languages.toml and registered in Postgres via /v1/languages. On startup the judge maps database IDs to local configs by name. A mismatch between the database and config file causes compile failures for all submissions in that language.
Runtimes
Section titled “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 |
Resource limits on problems
Section titled “Resource limits on problems”Problems store accept_timeout, execution_timeout, and memory_limit. Admins set these when creating problems or attaching them to contests.
Important: the judge currently uses fixed nsjail defaults (10s run CPU, ~6 MB virtual memory) and does not read per-problem limits from the API. Values in the UI are stored for future use and display. See Judge service — resource limits.
Execution
Section titled “Execution”All languages run through nsjail. See Judge service for sandbox and grading details.
languages.toml
Section titled “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
Section titled “Add a language”- Install toolchain in
Dockerfile.newbase - Write build script and test it in isolation if possible
- Rebuild judge image
POST /v1/languages- Submit a known AC solution. If step 5 fails, verify the build script before debugging the solution logic.
Language-specific notes
Section titled “Language-specific notes”Java: public class name must match filename, or the judge renames the file automatically.
Go: first submission after cold start is slow due to module download. Warm the cache or warn contestants.
TypeScript / Kotlin: compile errors appear as COMPILE_TIME_ERROR. Read stderr.
Python vs PyPy: same .py extension, different language IDs. Select the intended runtime explicitly.
Output comparison: line-by-line with trimmed whitespace. "42\n" and "42" can differ if output omits the trailing newline.