CLI

bin/chad is a small wrapper that runs the compiler under bun from any directory (symlink it onto your PATH if you like).

Command	What it does	Exit status
bin/chad check <entry.ts>	Typecheck and validate only; no binary. Prints ok: typechecks and is in-subset.	0, or 1 with diagnostics
bin/chad build <entry.ts> -o <out>	Compile the entry file and everything it imports to a native binary at -O2.	0, or 1 with diagnostics
bin/chad run <entry.ts> [args...]	Build into a temp directory, then run the binary with args.	the program's exit status
bin/chad doctor	Check bun, node, clang, opt and Milo, then compile and run a hello world.	0 when every check passes, else 1
bin/chad --version	Print the compiler version and the pinned Milo commit.	0

Diagnostics go to stderr, one per problem, followed by a count:

$ bin/chad check rejected.ts
error[CS1222]: iterating a Map directly with `for...of` is not supported yet
  --> rejected.ts:6:1
  help: iterate its keys and read each value: `for (const k of m.keys())`
error[CS1203]: `==` is not supported
  --> rejected.ts:7:7
  help: use `===`

2 error(s)

doctor

bin/chad doctor checks each tool the compiler needs, prints the fix for anything missing, and finally compiles and runs a hello world:

  ok    bun          1.3.10
  ok    node         v25.3.0
  ok    clang        22.1.8 (clang)
  ok    opt          22.1.8 (opt)
  ok    milo         pinned ba9484985954
  ok    hello world  compiled and ran

all checks passed

--version

$ bin/chad --version
chad 2.0.0-alpha.1 (milo ba9484985954aa8ecd7df24517dede04e7484a0a)

Environment variables

Variable	Effect
CHAD_CLANG	The clang to compile and link with (default clang), e.g. clang-18.
CHAD_OPT	The opt used by the test suite's IR verification (default opt).
CHAD_MILO	A milo compiler to build the runtime with, instead of the pinned one in .milo/.
CHAD_SAN=1	Build the runtime and the program with AddressSanitizer and UndefinedBehaviorSanitizer.
CHAD_GC_STRESS=N	Collect garbage before every Nth allocation (debugging the collector).
CHAD_GC_VERIFY=1	Poison freed memory and check traced pointers during collection.

The runtime is compiled on first use and cached under .build/; the cache key includes the runtime sources, the Milo commit and the build flags.

Repository scripts

Command	What it does
sh scripts/check-prereqs.sh	Check bun, clang, opt, Milo and dependencies (bin/chad doctor does more).
sh scripts/setup-milo.sh	Fetch the pinned Milo compiler into .milo/.
bun run test	Fast lane (under 10 s): unit, rejection, admission and definition-of-done tests.
bun run test:slow	Every test program checked against Node at -O0 and -O2, fuzzers, runtime tests.
bun run scripts/bench.ts	Benchmarks: ChadScript vs Node vs Rust.

Next: Accepted subset.