[python]

[python]
target = "3.13"
free-threaded = false

Key	Type	Default	Description
target	"3.13" | "3.13t" | "3.14" | "3.14t" | "3.15" | "3.15t"	"3.13"	Target CPython version. Drives syntax choices and a few lowering decisions. The t suffix selects free-threaded emission paths — see free-threaded below. A 3.15+ target additionally unlocks native PEP 810 lazy-import lowering — see lazy.
free-threaded	bool	false	Allow emit paths that use threads for parallelism (requires 3.13t/3.14t/3.15t). Default false until 3.14 ships as the default Python. free-threaded = true with a target lacking the t suffix is accepted — it only switches on advice lints — but tyc check / tyc build warn that a GIL build cannot benefit.

Targets

• "3.13" — default. Supports PEP 695 generics natively. Most projects.
• "3.14" — same, plus 3.14 syntax: t-strings and unparenthesised except A, B:.
• "3.15" — same, plus native PEP 810 lowering for lazy import: the emitter drops the typhon_runtime proxy-class helper entirely and emits the native lazy import MODULE as ALIAS statement instead. A project whose only runtime-touching feature was lazy import ships no generated typhon_runtime/ package at all on this target. 3.13 / 3.14 output is unaffected — byte-for-byte unchanged. A 3.15 target also unlocks unpacking comprehensions ([*xs for xs in lists], {**d for d in ds}) and the frozendict and sentinel builtins.

Syntax and builtins newer than the target are rejected with tyc::requires_newer_python, since the emitted .py could not compile or run there. Stdlib imports are vetted against the target as well: import sre_parse warns on 3.15, where the module was removed.

Older targets ("3.12", "3.11") are not supported in v1 — they would need a PEP 695 → TypeVar rewrite that we haven’t built.

free-threaded = true

Opts into the threading-based parallelism emit paths:

• go always lowers through typhon_runtime.tasks.spawn (an asyncio task held in a strong-ref registry) — there is no ThreadPoolExecutor lowering for go, including on free-threaded builds.
• The analyser may emit a thread-pool (or, with parallel-backend = "interpreters", a PEP 734 sub-interpreter pool) map for pure-function comprehensions over large collections ([strictness] auto-parallel) — including comprehensions with a pure filter, extra invariant call arguments, or nested pure calls — and, with [strictness] auto-parallel-reductions, int-only accumulator loops (for x in xs: total += f(x)).
• Every emitted parallel block first checks sys._is_gil_enabled() and falls back to sequential if a GIL build is detected.
• Two advice-only lints nudge free-threaded projects toward the above: tyc::parallel_opportunity (a parallelisable loop whose enabling knob is off) and tyc::shared_mut_across_tasks (a go-spawned function racing on shared module state). Both gated by [strictness] suggest-parallel (default true) and both silent unless free-threaded = true.

Requires the special python3.13t / python3.14t / python3.15t interpreter build. On a stock GIL build, the runtime fallback keeps the code correct (sequential execution).

See async, await, gather, go for the full parallelism surface, and [strictness] for every knob.

Default off until 3.14 ships as the default Python.