Exit codes

Source: src/node_exit_code.h. The leading comment in that file is unusually candid about which codes were intended versus what code actually does in practice.

Code	Symbol	When
0	NoFailure	Normal exit.
1	GenericUserError	Catch-all for uncaught JS exceptions and generic errors.
3	InternalJSParseError	Internal JS parse error (rare; usually pre-compiled builtins fail at snapshot).
4	InternalJSEvaluationFailure	Reserved (mostly produces exit 1 in practice).
5	V8FatalError	Reserved; SIGTRAP/SIGABRT often produce 133/134 instead.
6	InvalidFatalExceptionMonkeyPatching	User reassigned process._fatalException.
7	ExceptionInFatalExceptionHandler	The fatal exception handler itself threw.
9	InvalidCommandLineArgument	Unknown / malformed flag.
10	BootstrapFailure	The bootstrap (Realm::BootstrapRealm) failed.
12	InvalidCommandLineArgument2	Duplicate of 9 historically; retained for compatibility.
13	UnsettledTopLevelAwait	Top-level await in a main module never resolved.
14	StartupSnapshotFailure	--build-snapshot or snapshot deserialization failed.
128 + N	(signal)	Unix convention for "killed by signal N".
134	Abort	process.abort() or an internal CHECK failure.

Codes 2, 8, 11 are intentionally unassigned. The exit codes that come from V8 itself (V8FatalError, signal-based exits) often surface as the kernel's 128 + signum convention rather than the codes in this table.

The C++ helper node::Exit(ExitCode) (src/node_exit_code.h) is the canonical exit path. JS-side process.exit(code) ultimately calls Exit after running cleanup.