diff --git a/examples/hello-world/main.orc b/examples/hello-world/main.orc
index fa6faaf..d8a6b9d 100644
--- a/examples/hello-world/main.orc
+++ b/examples/hello-world/main.orc
@@ -1,2 +1,2 @@
-const user = "dave"
-const main = println "Hello $user!" exit_status::success
+let user = "dave"
+let main = println "Hello $user!" exit_status::success
diff --git a/orchid-api-traits/src/coding.rs b/orchid-api-traits/src/coding.rs
index 8e6445d..d8aeb59 100644
--- a/orchid-api-traits/src/coding.rs
+++ b/orchid-api-traits/src/coding.rs
@@ -270,7 +270,6 @@ impl Encode for bool {
 }
 impl<T: Decode, const N: usize> Decode for [T; N] {
 	async fn decode<R: AsyncRead + ?Sized>(mut read: Pin<&mut R>) -> Self {
-		// TODO: figure out how to do this in safe rust on the stack
 		let v = stream(async |mut cx| {
 			for _ in 0..N {
 				cx.emit(T::decode(read.as_mut()).await).await
diff --git a/orchid-api/src/parser.rs b/orchid-api/src/parser.rs
index 190dffc..22da5d2 100644
--- a/orchid-api/src/parser.rs
+++ b/orchid-api/src/parser.rs
@@ -30,6 +30,7 @@ pub struct ParseLine {
 	pub src: TStrv,
 	pub comments: Vec<Comment>,
 	pub exported: bool,
+	pub idx: u16,
 	pub line: Vec<TokenTree>,
 }
 impl Request for ParseLine {
diff --git a/orchid-base/src/number.rs b/orchid-base/src/number.rs
index fef744b..83d1ae6 100644
--- a/orchid-base/src/number.rs
+++ b/orchid-base/src/number.rs
@@ -79,7 +79,6 @@ pub fn parse_num(string: &str) -> Result<Numeric, NumError> {
 		.or_else(|| string.strip_prefix("0b").map(|s| (2u8, s, 2)))
 		.or_else(|| string.strip_prefix("0o").map(|s| (8u8, s, 2)))
 		.unwrap_or((10u8, string, 0));
-	eprintln!("({radix}, {noprefix}, {pos})");
 	// identity
 	let (base_s, exponent) = match noprefix.split_once('p') {
 		Some((b, e)) => {
@@ -88,7 +87,6 @@ pub fn parse_num(string: &str) -> Result<Numeric, NumError> {
 		},
 		None => (noprefix, 0),
 	};
-	eprintln!("({base_s},{exponent})");
 	match base_s.split_once('.') {
 		None => {
 			let base = int_parse(base_s, radix, pos)?;
diff --git a/orchid-base/src/reqnot.rs b/orchid-base/src/reqnot.rs
index d7b6035..6c4a59a 100644
--- a/orchid-base/src/reqnot.rs
+++ b/orchid-base/src/reqnot.rs
@@ -252,15 +252,14 @@ mod test {
 
 	use futures::FutureExt;
 	use futures::lock::Mutex;
-	use orchid_api::LogStrategy;
 	use orchid_api_derive::Coding;
 	use orchid_api_traits::{Channel, Request};
 	use test_executors::spin_on;
 
 	use super::{MsgSet, ReqNot};
-	use crate::clone;
 	use crate::logging::Logger;
 	use crate::reqnot::Requester as _;
+	use crate::{api, clone};
 
 	#[derive(Clone, Debug, Coding, PartialEq)]
 	pub struct TestReq(u8);
@@ -283,7 +282,7 @@ mod test {
 	#[test]
 	fn notification() {
 		spin_on(async {
-			let logger = Logger::new(LogStrategy::StdErr);
+			let logger = Logger::new(api::LogStrategy::StdErr);
 			let received = Arc::new(Mutex::new(None));
 			let receiver = ReqNot::<TestMsgSet>::new(
 				logger.clone(),
@@ -311,7 +310,7 @@ mod test {
 	#[test]
 	fn request() {
 		spin_on(async {
-			let logger = Logger::new(LogStrategy::StdErr);
+			let logger = Logger::new(api::LogStrategy::StdErr);
 			let receiver = Rc::new(Mutex::<Option<ReqNot<TestMsgSet>>>::new(None));
 			let sender = Rc::new(ReqNot::<TestMsgSet>::new(
 				logger.clone(),
diff --git a/orchid-extension/src/atom_owned.rs b/orchid-extension/src/atom_owned.rs
index afd938e..c3876c1 100644
--- a/orchid-extension/src/atom_owned.rs
+++ b/orchid-extension/src/atom_owned.rs
@@ -13,7 +13,6 @@ use futures::{AsyncRead, AsyncWrite, FutureExt};
 use itertools::Itertools;
 use memo_map::MemoMap;
 use never::Never;
-use orchid_api::AtomId;
 use orchid_api_traits::{Decode, Encode, enc_vec};
 use orchid_base::error::OrcRes;
 use orchid_base::format::{FmtCtx, FmtCtxImpl, FmtUnit};
@@ -41,7 +40,6 @@ impl<A: OwnedAtom + Atomic<Variant = OwnedVariant>> AtomicFeaturesImpl<OwnedVari
 			let mut data = enc_vec(&typ_id).await;
 			self.encode(Pin::<&mut Vec<u8>>::new(&mut data)).await;
 			ctx.get_or_default::<ObjStore>().objects.read().await.insert(atom_id, Box::new(self));
-			eprintln!("Created atom {:?} of type {}", atom_id, type_name::<A>());
 			api::Atom { drop: Some(atom_id), data, owner: ctx.sys_id() }
 		})
 	}
@@ -52,7 +50,7 @@ impl<A: OwnedAtom + Atomic<Variant = OwnedVariant>> AtomicFeaturesImpl<OwnedVari
 /// While an atom read guard is held, no atom can be removed.
 pub(crate) struct AtomReadGuard<'a> {
 	id: api::AtomId,
-	guard: RwLockReadGuard<'a, MemoMap<AtomId, Box<dyn DynOwnedAtom>>>,
+	guard: RwLockReadGuard<'a, MemoMap<api::AtomId, Box<dyn DynOwnedAtom>>>,
 }
 impl<'a> AtomReadGuard<'a> {
 	async fn new(id: api::AtomId, ctx: &'a SysCtx) -> Self {
diff --git a/orchid-extension/src/coroutine_exec.rs b/orchid-extension/src/coroutine_exec.rs
index bf56ca6..f528e92 100644
--- a/orchid-extension/src/coroutine_exec.rs
+++ b/orchid-extension/src/coroutine_exec.rs
@@ -1,14 +1,14 @@
 use std::borrow::Cow;
 use std::marker::PhantomData;
-use std::pin::Pin;
 use std::rc::Rc;
 
-use futures::channel::mpsc::{Receiver, Sender, channel};
-use futures::future::Fuse;
+use futures::channel::mpsc::{Sender, channel};
 use futures::lock::Mutex;
-use futures::{FutureExt, SinkExt, StreamExt, select};
+use futures::stream::{self, LocalBoxStream};
+use futures::{FutureExt, SinkExt, StreamExt};
 use never::Never;
 use orchid_base::error::OrcRes;
+use orchid_base::format::{FmtCtx, FmtUnit};
 
 use crate::atom::Atomic;
 use crate::atom_owned::{OwnedAtom, OwnedVariant};
@@ -19,35 +19,30 @@ use crate::gen_expr::{GExpr, arg, call, lambda, seq};
 enum Command {
 	Execute(GExpr, Sender<Expr>),
 	Register(GExpr, Sender<Expr>),
+	Halt(GExpr),
 }
 
 struct BuilderCoroutineData {
-	work: Fuse<Pin<Box<dyn Future<Output = GExpr>>>>,
-	cmd_recv: Receiver<Command>,
+	name: Option<String>,
+	receiver: Mutex<LocalBoxStream<'static, Command>>,
 }
+
 #[derive(Clone)]
-struct BuilderCoroutine(Rc<Mutex<BuilderCoroutineData>>);
+struct BuilderCoroutine(Rc<BuilderCoroutineData>);
 impl BuilderCoroutine {
 	pub async fn run(self) -> GExpr {
-		let cmd = {
-			let this = &mut *self.0.lock().await;
-			select! {
-				ret_val = &mut this.work => { return ret_val },
-				cmd_res = this.cmd_recv.next().fuse() => match cmd_res {
-					Some(cmd) => cmd,
-					None => return (&mut this.work).await
-				},
-			}
-		};
+		let cmd = self.0.receiver.lock().await.next().await;
 		match cmd {
-			Command::Execute(expr, reply) => call([
+			None => panic!("Before the stream ends, we should have gotten a Halt"),
+			Some(Command::Halt(expr)) => expr,
+			Some(Command::Execute(expr, reply)) => call([
 				lambda(0, [seq([
 					arg(0),
 					call([Replier { reply, builder: self }.to_expr().await, arg(0)]),
 				])]),
 				expr,
 			]),
-			Command::Register(expr, reply) =>
+			Some(Command::Register(expr, reply)) =>
 				call([Replier { reply, builder: self }.to_expr().await, expr]),
 		}
 	}
@@ -66,16 +61,29 @@ impl OwnedAtom for Replier {
 	type Refs = Never;
 	async fn val(&self) -> Cow<'_, Self::Data> { Cow::Owned(()) }
 	async fn call(mut self, arg: Expr) -> GExpr {
-		let _ = self.reply.send(arg).await;
+		self.reply.send(arg).await.expect("What the heck");
+		std::mem::drop(self.reply);
 		self.builder.run().await
 	}
+	async fn print_atom<'a>(&'a self, _: &'a (impl FmtCtx + ?Sized + 'a)) -> FmtUnit {
+		match &self.builder.0.name {
+			None => "BuilderCoroutine".into(),
+			Some(name) => format!("BuilderCoroutine({name})").into(),
+		}
+	}
 }
 
-pub async fn exec<R: ToExpr>(f: impl for<'a> AsyncFnOnce(ExecHandle<'a>) -> R + 'static) -> GExpr {
+pub async fn exec<R: ToExpr>(
+	debug: impl AsRef<str>,
+	f: impl for<'a> AsyncFnOnce(ExecHandle<'a>) -> R + 'static,
+) -> GExpr {
 	let (cmd_snd, cmd_recv) = channel(0);
-	let work =
-		async { f(ExecHandle(cmd_snd, PhantomData)).await.to_expr().await }.boxed_local().fuse();
-	let coro = BuilderCoroutine(Rc::new(Mutex::new(BuilderCoroutineData { cmd_recv, work })));
+	let halt = async { Command::Halt(f(ExecHandle(cmd_snd, PhantomData)).await.to_expr().await) }
+		.into_stream();
+	let coro = BuilderCoroutine(Rc::new(BuilderCoroutineData {
+		name: Some(debug.as_ref().to_string()),
+		receiver: Mutex::new(stream::select(halt, cmd_recv).boxed_local()),
+	}));
 	coro.run().await
 }
 
@@ -84,12 +92,12 @@ static WEIRD_DROP_ERR: &str = "Coroutine dropped while we are being polled someh
 pub struct ExecHandle<'a>(Sender<Command>, PhantomData<&'a ()>);
 impl ExecHandle<'_> {
 	pub async fn exec<T: TryFromExpr>(&mut self, val: impl ToExpr) -> OrcRes<T> {
-		let (reply_snd, mut reply_recv) = channel(0);
+		let (reply_snd, mut reply_recv) = channel(1);
 		self.0.send(Command::Execute(val.to_expr().await, reply_snd)).await.expect(WEIRD_DROP_ERR);
 		T::try_from_expr(reply_recv.next().await.expect(WEIRD_DROP_ERR)).await
 	}
 	pub async fn register(&mut self, val: impl ToExpr) -> Expr {
-		let (reply_snd, mut reply_recv) = channel(0);
+		let (reply_snd, mut reply_recv) = channel(1);
 		self.0.send(Command::Register(val.to_expr().await, reply_snd)).await.expect(WEIRD_DROP_ERR);
 		reply_recv.next().await.expect(WEIRD_DROP_ERR)
 	}
diff --git a/orchid-extension/src/entrypoint.rs b/orchid-extension/src/entrypoint.rs
index 2986490..5d5699d 100644
--- a/orchid-extension/src/entrypoint.rs
+++ b/orchid-extension/src/entrypoint.rs
@@ -11,7 +11,6 @@ use futures::lock::Mutex;
 use futures::{FutureExt, SinkExt, StreamExt, stream, stream_select};
 use hashbrown::HashMap;
 use itertools::Itertools;
-use orchid_api::{ExtMsgSet, IntReq};
 use orchid_api_traits::{Decode, UnderRoot, enc_vec};
 use orchid_base::builtin::{ExtInit, ExtPort, Spawner};
 use orchid_base::char_filter::{char_filter_match, char_filter_union, mk_char_filter};
@@ -29,9 +28,9 @@ use trait_set::trait_set;
 use crate::api;
 use crate::atom::{AtomCtx, AtomDynfo, AtomTypeId};
 use crate::atom_owned::take_atom;
-use crate::expr::{Expr, ExprHandle};
+use crate::expr::{BorrowedExprStore, Expr, ExprHandle};
 use crate::lexer::{LexContext, ekey_cascade, ekey_not_applicable};
-use crate::parser::{PTok, PTokTree, ParsCtx, get_const, linev_into_api};
+use crate::parser::{PTokTree, ParsCtx, get_const, linev_into_api};
 use crate::system::{SysCtx, atom_by_idx};
 use crate::system_ctor::{CtedObj, DynSystemCtor};
 use crate::tree::{LazyMemberFactory, TreeIntoApiCtxImpl};
@@ -124,7 +123,7 @@ pub fn extension_init(
 	}));
 	let init_ctx = {
 		clone!(interner_weak, spawner, logger);
-		move |id: api::SysId, cted: CtedObj, reqnot: ReqNot<ExtMsgSet>| {
+		move |id: api::SysId, cted: CtedObj, reqnot: ReqNot<api::ExtMsgSet>| {
 			clone!(interner_weak, spawner, logger; async move {
 				let interner_rc =
 					interner_weak.upgrade().expect("System construction order while shutting down");
@@ -242,49 +241,62 @@ pub fn extension_init(
 							let text = Tok::from_api(text, &i).await;
 							let src = Sym::from_api(src, sys_ctx.i()).await;
 							let rep = Reporter::new();
-							let ctx = LexContext { id, pos, text: &text, src, ctx: sys_ctx.clone(), rep: &rep };
+							let expr_store = BorrowedExprStore::new();
 							let trigger_char = text.chars().nth(pos as usize).unwrap();
 							let ekey_na = ekey_not_applicable(&i).await;
 							let ekey_cascade = ekey_cascade(&i).await;
 							let lexers = sys_ctx.cted().inst().dyn_lexers();
 							for lx in lexers.iter().filter(|l| char_filter_match(l.char_filter(), trigger_char)) {
+								let ctx = LexContext {
+									id,
+									pos,
+									text: &text,
+									src: src.clone(),
+									ctx: sys_ctx.clone(),
+									rep: &rep,
+									exprs: &expr_store,
+								};
 								match lx.lex(&text[pos as usize..], &ctx).await {
 									Err(e) if e.any(|e| *e == ekey_na) => continue,
 									Err(e) => {
 										let eopt = e.keep_only(|e| *e != ekey_cascade).map(|e| Err(e.to_api()));
+										expr_store.dispose().await;
 										return hand.handle(&lex, &eopt).await;
 									},
 									Ok((s, expr)) => {
 										let expr = expr.into_api(&mut (), &mut (sys_ctx, &hand)).await;
 										let pos = (text.len() - s.len()) as u32;
+										expr_store.dispose().await;
 										return hand.handle(&lex, &Some(Ok(api::LexedExpr { pos, expr }))).await;
 									},
 								}
 							}
 							writeln!(logger, "Got notified about n/a character '{trigger_char}'");
+							expr_store.dispose().await;
 							hand.handle(&lex, &None).await
 						},
 						api::HostExtReq::ParseLine(pline) => {
-							let api::ParseLine { module, src, exported, comments, sys, line } = &pline;
-							let mut ctx = get_ctx(*sys).await;
+							let api::ParseLine { module, src, exported, comments, sys, line, idx } = &pline;
+							let ctx = get_ctx(*sys).await;
 							let parsers = ctx.cted().inst().dyn_parsers();
 							let src = Sym::from_api(*src, ctx.i()).await;
 							let comments =
 								join_all(comments.iter().map(|c| Comment::from_api(c, src.clone(), &i))).await;
-							let line: Vec<PTokTree> = ttv_from_api(line, &mut ctx, &mut (), &src, &i).await;
+							let expr_store = BorrowedExprStore::new();
+							let mut from_api_ctx = (ctx.clone(), &expr_store);
+							let line: Vec<PTokTree> =
+								ttv_from_api(line, &mut from_api_ctx, &mut (), &src, &i).await;
 							let snip = Snippet::new(line.first().expect("Empty line"), &line);
-							let (head, tail) = snip.pop_front().unwrap();
-							let name = if let PTok::Name(n) = &head.tok { n } else { panic!("No line head") };
-							let parser =
-								parsers.iter().find(|p| p.line_head() == **name).expect("No parser candidate");
+							let parser = parsers[*idx as usize];
 							let module = Sym::from_api(*module, ctx.i()).await;
 							let reporter = Reporter::new();
 							let pctx = ParsCtx::new(ctx.clone(), module, &reporter);
-							let parse_res = parser.parse(pctx, *exported, comments, tail).await;
+							let parse_res = parser.parse(pctx, *exported, comments, snip).await;
 							let o_line = match reporter.merge(parse_res) {
 								Err(e) => Err(e.to_api()),
 								Ok(t) => Ok(linev_into_api(t, ctx.clone(), &hand).await),
 							};
+							expr_store.dispose().await;
 							hand.handle(&pline, &o_line).await
 						},
 						api::HostExtReq::FetchParsedConst(ref fpc @ api::FetchParsedConst { id, sys }) => {
@@ -297,6 +309,7 @@ pub fn extension_init(
 							let atom_req = atom_req.clone();
 							with_atom_record(&get_ctx, atom, async move |nfo, ctx, id, buf| {
 								let actx = AtomCtx(buf, atom.drop, ctx.clone());
+
 								match &atom_req {
 									api::AtomReq::SerializeAtom(ser) => {
 										let mut buf = enc_vec(&id).await;
@@ -327,16 +340,23 @@ pub fn extension_init(
 										hand.handle(fwded, &some.then_some(reply)).await
 									},
 									api::AtomReq::CallRef(call @ api::CallRef(_, arg)) => {
-										// SAFETY: function calls own their argument implicitly
-										let expr_handle = unsafe { ExprHandle::from_args(ctx.clone(), *arg) };
-										let ret = nfo.call_ref(actx, Expr::from_handle(Rc::new(expr_handle))).await;
-										hand.handle(call, &ret.api_return(ctx.clone(), &hand).await).await
+										// SAFETY: function calls borrow their argument implicitly
+										let expr_store = BorrowedExprStore::new();
+										let expr_handle = ExprHandle::borrowed(ctx.clone(), *arg, &expr_store);
+										let ret = nfo.call_ref(actx, Expr::from_handle(expr_handle.clone())).await;
+										expr_handle.drop_one().await;
+										let api_expr = ret.api_return(ctx.clone(), &hand).await;
+										expr_store.dispose().await;
+										hand.handle(call, &api_expr).await
 									},
 									api::AtomReq::FinalCall(call @ api::FinalCall(_, arg)) => {
-										// SAFETY: function calls own their argument implicitly
-										let expr_handle = unsafe { ExprHandle::from_args(ctx.clone(), *arg) };
-										let ret = nfo.call(actx, Expr::from_handle(Rc::new(expr_handle))).await;
-										hand.handle(call, &ret.api_return(ctx.clone(), &hand).await).await
+										// SAFETY: function calls borrow their argument implicitly
+										let expr_store = BorrowedExprStore::new();
+										let expr_handle = ExprHandle::borrowed(ctx.clone(), *arg, &expr_store);
+										let ret = nfo.call(actx, Expr::from_handle(expr_handle.clone())).await;
+										let api_expr = ret.api_return(ctx.clone(), &hand).await;
+										expr_store.dispose().await;
+										hand.handle(call, &api_expr).await
 									},
 									api::AtomReq::Command(cmd @ api::Command(_)) => match nfo.command(actx).await {
 										Err(e) => hand.handle(cmd, &Err(e.to_api())).await,
@@ -358,8 +378,7 @@ pub fn extension_init(
 							let ctx = get_ctx(*sys).await;
 							// SAFETY: deserialization implicitly grants ownership to previously owned exprs
 							let refs = (refs.iter())
-								.map(|tk| unsafe { ExprHandle::from_args(ctx.clone(), *tk) })
-								.map(|handle| Expr::from_handle(Rc::new(handle)))
+								.map(|tk| Expr::from_handle(ExprHandle::deserialize(ctx.clone(), *tk)))
 								.collect_vec();
 							let id = AtomTypeId::decode(Pin::new(&mut read)).await;
 							let inst = ctx.cted().inst();
@@ -373,7 +392,7 @@ pub fn extension_init(
 		},
 	);
 	*interner_cell.borrow_mut() =
-		Some(Interner::new_replica(rn.clone().map(|ir: IntReq| ir.into_root())));
+		Some(Interner::new_replica(rn.clone().map(|ir: api::IntReq| ir.into_root())));
 	spawner(Box::pin(clone!(spawner; async move {
 		let mut streams = stream_select! { in_recv.map(Some), exit_recv.map(|_| None) };
 		while let Some(item) = streams.next().await {
diff --git a/orchid-extension/src/expr.rs b/orchid-extension/src/expr.rs
index b9dd56b..bb30104 100644
--- a/orchid-extension/src/expr.rs
+++ b/orchid-extension/src/expr.rs
@@ -1,9 +1,11 @@
+use std::cell::RefCell;
 use std::fmt;
+use std::hash::Hash;
 use std::rc::Rc;
 
 use async_once_cell::OnceCell;
 use derive_destructure::destructure;
-use orchid_api::ExtAtomPrint;
+use hashbrown::HashSet;
 use orchid_base::error::OrcErrv;
 use orchid_base::format::{FmtCtx, FmtUnit, Format};
 use orchid_base::location::Pos;
@@ -14,26 +16,61 @@ use crate::atom::ForeignAtom;
 use crate::gen_expr::{GExpr, GExprKind};
 use crate::system::SysCtx;
 
+pub struct BorrowedExprStore(RefCell<Option<HashSet<Rc<ExprHandle>>>>);
+impl BorrowedExprStore {
+	pub(crate) fn new() -> Self { Self(RefCell::new(Some(HashSet::new()))) }
+	pub async fn dispose(self) {
+		let elements = self.0.borrow_mut().take().unwrap();
+		for handle in elements {
+			handle.drop_one().await
+		}
+	}
+}
+impl Drop for BorrowedExprStore {
+	fn drop(&mut self) {
+		if self.0.borrow().is_some() {
+			panic!("This should always be explicitly disposed")
+		}
+	}
+}
+
 #[derive(destructure)]
 pub struct ExprHandle {
 	pub tk: api::ExprTicket,
 	pub ctx: SysCtx,
 }
 impl ExprHandle {
-	/// # Safety
-	///
-	/// This function does not signal to take ownership of the expr. It must only
-	/// be called on tickets that are already implicitly owned.
-	pub unsafe fn from_args(ctx: SysCtx, tk: api::ExprTicket) -> Self { Self { ctx, tk } }
+	/// This function does not signal to take ownership of the expr.
+	pub fn borrowed(ctx: SysCtx, tk: api::ExprTicket, store: &BorrowedExprStore) -> Rc<Self> {
+		let this = Rc::new(Self { ctx, tk });
+		store.0.borrow_mut().as_mut().unwrap().insert(this.clone());
+		this
+	}
+	pub fn deserialize(ctx: SysCtx, tk: api::ExprTicket) -> Rc<Self> { Rc::new(Self { ctx, tk }) }
 	pub fn get_ctx(&self) -> SysCtx { self.ctx.clone() }
-	pub async fn clone(&self) -> Self {
-		self.ctx.reqnot().notify(api::Acquire(self.ctx.sys_id(), self.tk)).await;
-		Self { ctx: self.ctx.clone(), tk: self.tk }
+	/// Drop one instance of the handle silently; if it's the last one, do
+	/// nothing, otherwise send an Acquire
+	pub async fn drop_one(self: Rc<Self>) {
+		if let Err(rc) = Rc::try_unwrap(self) {
+			rc.ctx.reqnot().notify(api::Acquire(rc.ctx.sys_id(), rc.tk)).await
+		}
 	}
 	/// Drop the handle and get the ticket without a release notification.
 	/// Use this with messages that imply ownership transfer. This function is
 	/// safe because abusing it is a memory leak.
-	pub fn into_tk(self) -> api::ExprTicket { self.destructure().0 }
+	pub fn serialize(self) -> api::ExprTicket { self.destructure().0 }
+}
+impl Eq for ExprHandle {}
+impl PartialEq for ExprHandle {
+	fn eq(&self, other: &Self) -> bool {
+		self.ctx.sys_id() == other.ctx.sys_id() && self.tk == other.tk
+	}
+}
+impl Hash for ExprHandle {
+	fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+		self.ctx.sys_id().hash(state);
+		self.tk.hash(state);
+	}
 }
 impl fmt::Debug for ExprHandle {
 	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
@@ -92,8 +129,9 @@ impl Format for Expr {
 		match &self.data().await.kind {
 			ExprKind::Opaque => "OPAQUE".to_string().into(),
 			ExprKind::Bottom(b) => format!("Bottom({b})").into(),
-			ExprKind::Atom(a) =>
-				FmtUnit::from_api(&self.handle.ctx.reqnot().request(ExtAtomPrint(a.atom.clone())).await),
+			ExprKind::Atom(a) => FmtUnit::from_api(
+				&self.handle.ctx.reqnot().request(api::ExtAtomPrint(a.atom.clone())).await,
+			),
 		}
 	}
 }
diff --git a/orchid-extension/src/func_atom.rs b/orchid-extension/src/func_atom.rs
index b62bc1c..cddc8b4 100644
--- a/orchid-extension/src/func_atom.rs
+++ b/orchid-extension/src/func_atom.rs
@@ -1,8 +1,3 @@
-//! #TODO: redefine this in terms of [crate::coroutine_exec::exec]. Try
-//! differentiating between eager and lazy arguments. [ExprFunc] can remain with
-//! tweaks but other techniques probably must go.
-//!
-//! Notice also that Func must still be resumable
 use std::any::TypeId;
 use std::borrow::Cow;
 use std::collections::HashMap;
@@ -48,11 +43,14 @@ struct FunRecord {
 	fun: Rc<dyn FunCB>,
 }
 
-async fn process_args<I, O, F: ExprFunc<I, O>>(f: F) -> FunRecord {
+async fn process_args<I, O, F: ExprFunc<I, O>>(
+	debug: impl AsRef<str> + Clone + 'static,
+	f: F,
+) -> FunRecord {
 	let argtyps = F::argtyps();
 	let fun = Rc::new(move |v: Vec<Expr>| {
 		clone!(f, v mut);
-		exec(async move |mut hand| {
+		exec(debug.clone(), async move |mut hand| {
 			let mut norm_args = Vec::with_capacity(v.len());
 			for (expr, typ) in v.into_iter().zip(argtyps) {
 				if *typ != TypeId::of::<Expr>() {
@@ -85,7 +83,7 @@ impl Fun {
 		let record = if let Some(record) = fung.get(&path) {
 			record.clone()
 		} else {
-			let record = process_args(f).await;
+			let record = process_args(path.to_string(), f).await;
 			fung.insert(path.clone(), record.clone());
 			record
 		};
@@ -101,7 +99,6 @@ impl OwnedAtom for Fun {
 	type Refs = Vec<Expr>;
 	async fn val(&self) -> Cow<'_, Self::Data> { Cow::Owned(()) }
 	async fn call_ref(&self, arg: Expr) -> GExpr {
-		std::io::Write::flush(&mut std::io::stderr()).unwrap();
 		let new_args = self.args.iter().cloned().chain([arg]).collect_vec();
 		if new_args.len() == self.record.argtyps.len() {
 			(self.record.fun)(new_args).await.to_expr().await
@@ -137,8 +134,11 @@ pub struct Lambda {
 	record: FunRecord,
 }
 impl Lambda {
-	pub async fn new<I, O, F: ExprFunc<I, O>>(f: F) -> Self {
-		Self { args: vec![], record: process_args(f).await }
+	pub async fn new<I, O, F: ExprFunc<I, O>>(
+		debug: impl AsRef<str> + Clone + 'static,
+		f: F,
+	) -> Self {
+		Self { args: vec![], record: process_args(debug, f).await }
 	}
 }
 impl Atomic for Lambda {
diff --git a/orchid-extension/src/gen_expr.rs b/orchid-extension/src/gen_expr.rs
index e7efa29..767cf51 100644
--- a/orchid-extension/src/gen_expr.rs
+++ b/orchid-extension/src/gen_expr.rs
@@ -66,7 +66,6 @@ impl GExprKind {
 			Lambda(arg, body => Box::new(body.api_return(ctx, hand).await)),
 			Arg(arg),
 			Const(name.to_api()),
-			Const(name.to_api()),
 			Bottom(err.to_api()),
 			NewAtom(fac.clone().build(ctx).await),
 		} {
diff --git a/orchid-extension/src/lexer.rs b/orchid-extension/src/lexer.rs
index 0d2442f..b41c1b2 100644
--- a/orchid-extension/src/lexer.rs
+++ b/orchid-extension/src/lexer.rs
@@ -12,6 +12,7 @@ use orchid_base::parse::ParseCtx;
 use orchid_base::reqnot::Requester;
 
 use crate::api;
+use crate::expr::BorrowedExprStore;
 use crate::parser::PTokTree;
 use crate::system::SysCtx;
 use crate::tree::GenTokTree;
@@ -34,6 +35,7 @@ pub async fn err_not_applicable(i: &Interner) -> OrcErrv {
 }
 
 pub struct LexContext<'a> {
+	pub(crate) exprs: &'a BorrowedExprStore,
 	pub ctx: SysCtx,
 	pub text: &'a Tok<String>,
 	pub id: api::ParsId,
@@ -52,8 +54,14 @@ impl<'a> LexContext<'a> {
 		let Some(lx) = self.ctx.reqnot().request(api::SubLex { pos: start, id: self.id }).await else {
 			return Err(err_cascade(self.ctx.i()).await);
 		};
-		let tree =
-			PTokTree::from_api(&lx.tree, &mut self.ctx.clone(), &mut (), &self.src, self.ctx.i()).await;
+		let tree = PTokTree::from_api(
+			&lx.tree,
+			&mut (self.ctx.clone(), self.exprs),
+			&mut (),
+			&self.src,
+			self.ctx.i(),
+		)
+		.await;
 		Ok((&self.text[lx.pos as usize..], tree))
 	}
 
diff --git a/orchid-extension/src/parser.rs b/orchid-extension/src/parser.rs
index fa48e7f..8494123 100644
--- a/orchid-extension/src/parser.rs
+++ b/orchid-extension/src/parser.rs
@@ -5,7 +5,6 @@ use futures::future::{LocalBoxFuture, join_all};
 use futures::{FutureExt, Stream, StreamExt};
 use itertools::Itertools;
 use never::Never;
-use orchid_api::ResolveNames;
 use orchid_base::error::{OrcErrv, OrcRes, Reporter};
 use orchid_base::id_store::IdStore;
 use orchid_base::interner::{Interner, Tok};
@@ -186,21 +185,6 @@ pub enum ParsedMemKind {
 	Mod { lines: Vec<ParsedLine>, use_prelude: bool },
 }
 
-/* TODO: how the macro runner uses the multi-stage loader
-
-Since the macro runner actually has to invoke the interpreter,
-it'll run at const-time and not at postparse-time anyway.
-
-pasing stage establishes the role of every constant as a macro keyword
-postparse / const load links up constants with every macro they can directly invoke
-	the constants representing the keywords might not actually be postparsed,
-	\ the connection is instead made by detecting in the macro system that the
-	\ resolved name is owned by a macro
-	the returned constant from this call is always an entrypoint call to
-	\ the macro system
-	the constants representing the keywords resolve to panic
-execute relies on these links detected in the extension to dispatch relevant macros
-*/
 #[derive(Clone)]
 pub struct ConstCtx {
 	ctx: SysCtx,
@@ -213,7 +197,7 @@ impl ConstCtx {
 		&'b self,
 		names: impl IntoIterator<Item = &'b Sym> + 'b,
 	) -> impl Stream<Item = OrcRes<Sym>> + 'b {
-		let resolve_names = ResolveNames {
+		let resolve_names = api::ResolveNames {
 			constid: self.constid,
 			sys: self.ctx.sys_id(),
 			names: names.into_iter().map(|n| n.to_api()).collect_vec(),
diff --git a/orchid-extension/src/system.rs b/orchid-extension/src/system.rs
index 40b9f6e..abf4972 100644
--- a/orchid-extension/src/system.rs
+++ b/orchid-extension/src/system.rs
@@ -7,7 +7,6 @@ use std::rc::{Rc, Weak};
 
 use futures::future::LocalBoxFuture;
 use memo_map::MemoMap;
-use orchid_api::ExtMsgSet;
 use orchid_api_traits::{Coding, Decode};
 use orchid_base::boxed_iter::BoxedIter;
 use orchid_base::builtin::Spawner;
@@ -18,8 +17,9 @@ use orchid_base::reqnot::{Receipt, ReqNot};
 
 use crate::api;
 use crate::atom::{AtomCtx, AtomDynfo, AtomTypeId, AtomicFeatures, ForeignAtom, TypAtom, get_info};
+use crate::coroutine_exec::Replier;
 use crate::entrypoint::ExtReq;
-use crate::func_atom::Fun;
+use crate::func_atom::{Fun, Lambda};
 use crate::lexer::LexerObj;
 use crate::parser::ParserObj;
 use crate::system_ctor::{CtedObj, SystemCtor};
@@ -43,7 +43,7 @@ pub trait DynSystemCard: Send + Sync + 'static {
 /// The indices of these are bitwise negated, such that the MSB of an atom index
 /// marks whether it belongs to this package (0) or the importer (1)
 fn general_atoms() -> impl Iterator<Item = Option<Box<dyn AtomDynfo>>> {
-	[Some(Fun::dynfo())].into_iter()
+	[Some(Fun::dynfo()), Some(Lambda::dynfo()), Some(Replier::dynfo())].into_iter()
 }
 
 pub fn atom_info_for(
@@ -149,7 +149,7 @@ impl SysCtx {
 	pub fn new(
 		id: api::SysId,
 		i: Interner,
-		reqnot: ReqNot<ExtMsgSet>,
+		reqnot: ReqNot<api::ExtMsgSet>,
 		spawner: Spawner,
 		logger: Logger,
 		cted: CtedObj,
@@ -167,13 +167,7 @@ impl SysCtx {
 		(self.0.get_or_insert_owned(TypeId::of::<T>(), || Box::new(f())).downcast_ref())
 			.expect("Keyed by TypeId")
 	}
-	pub fn get_or_default<T: SysCtxEntry + Default>(&self) -> &T {
-		self.get_or_insert(|| {
-			let rc_id = self.0.as_ref() as *const _ as *const () as usize;
-			eprintln!("Default-initializing {} in {}", type_name::<T>(), rc_id);
-			T::default()
-		})
-	}
+	pub fn get_or_default<T: SysCtxEntry + Default>(&self) -> &T { self.get_or_insert(T::default) }
 	pub fn try_get<T: SysCtxEntry>(&self) -> Option<&T> {
 		Some(self.0.get(&TypeId::of::<T>())?.downcast_ref().expect("Keyed by TypeId"))
 	}
@@ -183,7 +177,7 @@ impl SysCtx {
 	/// Shorthand to get the [Interner] instance
 	pub fn i(&self) -> &Interner { self.get::<Interner>() }
 	/// Shorthand to get the messaging link
-	pub fn reqnot(&self) -> &ReqNot<ExtMsgSet> { self.get::<ReqNot<ExtMsgSet>>() }
+	pub fn reqnot(&self) -> &ReqNot<api::ExtMsgSet> { self.get::<ReqNot<api::ExtMsgSet>>() }
 	/// Shorthand to get the system ID
 	pub fn sys_id(&self) -> api::SysId { *self.get::<api::SysId>() }
 	/// Shorthand to get the task spawner callback
diff --git a/orchid-extension/src/tree.rs b/orchid-extension/src/tree.rs
index 73fafaa..89b4dcb 100644
--- a/orchid-extension/src/tree.rs
+++ b/orchid-extension/src/tree.rs
@@ -1,5 +1,4 @@
 use std::num::NonZero;
-use std::rc::Rc;
 
 use async_fn_stream::stream;
 use dyn_clone::{DynClone, clone_box};
@@ -18,9 +17,9 @@ use trait_set::trait_set;
 use crate::api;
 use crate::conv::ToExpr;
 use crate::entrypoint::MemberRecord;
-use crate::expr::{Expr, ExprHandle};
+use crate::expr::{BorrowedExprStore, Expr, ExprHandle};
 use crate::func_atom::{ExprFunc, Fun};
-use crate::gen_expr::{GExpr, arg, call, lambda, seq, sym_ref};
+use crate::gen_expr::{GExpr, sym_ref};
 use crate::system::SysCtx;
 
 pub type GenTokTree = TokTree<Expr, GExpr>;
@@ -43,26 +42,18 @@ impl TokenVariant<api::Expression> for GExpr {
 }
 
 impl TokenVariant<api::ExprTicket> for Expr {
-	type FromApiCtx<'a> = SysCtx;
+	type FromApiCtx<'a> = (SysCtx, &'a BorrowedExprStore);
 	async fn from_api(
 		api: &api::ExprTicket,
-		ctx: &mut Self::FromApiCtx<'_>,
+		(ctx, exprs): &mut Self::FromApiCtx<'_>,
 		_: SrcRange,
 		_: &Interner,
 	) -> Self {
-		// SAFETY: receiving trees from sublexers implies ownership transfer
-		Expr::from_handle(Rc::new(unsafe { ExprHandle::from_args(ctx.clone(), *api) }))
+		// SAFETY: receiving trees from sublexers implies borrowing
+		Expr::from_handle(ExprHandle::borrowed(ctx.clone(), *api, exprs))
 	}
 	type ToApiCtx<'a> = ();
-	async fn into_api(self, (): &mut Self::ToApiCtx<'_>) -> api::ExprTicket {
-		let hand = self.handle();
-		std::mem::drop(self);
-		let h = match Rc::try_unwrap(hand) {
-			Ok(h) => h,
-			Err(h) => h.as_ref().clone().await,
-		};
-		h.into_tk()
-	}
+	async fn into_api(self, (): &mut Self::ToApiCtx<'_>) -> api::ExprTicket { self.handle().tk }
 }
 
 pub async fn x_tok(x: impl ToExpr) -> GenTok { GenTok::NewExpr(x.to_expr().await) }
@@ -96,19 +87,9 @@ pub fn root_mod(name: &str, mems: impl IntoIterator<Item = Vec<GenMember>>) -> (
 	(name.to_string(), kind)
 }
 pub fn fun<I, O>(public: bool, name: &str, xf: impl ExprFunc<I, O>) -> Vec<GenMember> {
-	let fac =
-		LazyMemberFactory::new(move |sym, ctx| async {
-			return MemKind::Const(build_lambdas(Fun::new(sym, ctx, xf).await, 0).await);
-			async fn build_lambdas(fun: Fun, i: u64) -> GExpr {
-				if i < fun.arity().into() {
-					return lambda(i, [build_lambdas(fun, i + 1).boxed_local().await]);
-				}
-				let arity = fun.arity();
-				seq((0..arity).map(|i| arg(i as u64)).chain([call(
-					[fun.to_expr().await].into_iter().chain((0..arity).map(|i| arg(i as u64))),
-				)]))
-			}
-		});
+	let fac = LazyMemberFactory::new(async move |sym, ctx| {
+		MemKind::Const(Fun::new(sym, ctx, xf).await.to_expr().await)
+	});
 	vec![GenMember { name: name.to_string(), kind: MemKind::Lazy(fac), public, comments: vec![] }]
 }
 pub fn prefix(path: &str, items: impl IntoIterator<Item = Vec<GenMember>>) -> Vec<GenMember> {
diff --git a/orchid-host/src/atom.rs b/orchid-host/src/atom.rs
index 2418f72..5487008 100644
--- a/orchid-host/src/atom.rs
+++ b/orchid-host/src/atom.rs
@@ -1,6 +1,7 @@
 use std::fmt;
 use std::rc::{Rc, Weak};
 
+use async_lock::OnceCell;
 use derive_destructure::destructure;
 use orchid_base::format::{FmtCtx, FmtUnit, Format, take_first_fmt};
 use orchid_base::location::Pos;
@@ -9,7 +10,7 @@ use orchid_base::tree::AtomRepr;
 
 use crate::api;
 use crate::ctx::Ctx;
-use crate::expr::Expr;
+use crate::expr::{Expr, ExprParseCtx, PathSetBuilder};
 use crate::extension::Extension;
 use crate::system::System;
 
@@ -18,11 +19,12 @@ pub struct AtomData {
 	owner: System,
 	drop: Option<api::AtomId>,
 	data: Vec<u8>,
+	pub(crate) display: OnceCell<FmtUnit>,
 }
 impl AtomData {
 	#[must_use]
 	fn api(self) -> api::Atom {
-		let (owner, drop, data) = self.destructure();
+		let (owner, drop, data, _display) = self.destructure();
 		api::Atom { data, drop, owner: owner.id() }
 	}
 	#[must_use]
@@ -50,35 +52,22 @@ impl fmt::Debug for AtomData {
 #[derive(Clone, Debug)]
 pub struct AtomHand(Rc<AtomData>);
 impl AtomHand {
-	#[must_use]
-	pub(crate) async fn new(api::Atom { data, drop, owner }: api::Atom, ctx: &Ctx) -> Self {
-		let create = || async {
-			let owner = ctx.system_inst(owner).await.expect("Dropped system created atom");
-			AtomHand(Rc::new(AtomData { data, owner, drop }))
-		};
-		if let Some(id) = drop {
-			let mut owned_g = ctx.owned_atoms.write().await;
-			if let Some(data) = owned_g.get(&id)
-				&& let Some(atom) = data.upgrade()
-			{
-				return atom;
-			}
-			let new = create().await;
-			owned_g.insert(id, new.downgrade());
-			new
-		} else {
-			create().await
-		}
+	pub(crate) fn new(data: Vec<u8>, owner: System, drop: Option<api::AtomId>) -> Self {
+		Self(Rc::new(AtomData { owner, drop, data, display: OnceCell::new() }))
 	}
 	#[must_use]
-	pub async fn call(self, arg: Expr) -> api::Expression {
+	pub async fn call(self, arg: Expr) -> Expr {
 		let owner_sys = self.0.owner.clone();
 		let reqnot = owner_sys.reqnot();
 		owner_sys.ext().exprs().give_expr(arg.clone());
-		match Rc::try_unwrap(self.0) {
+		let ret = match Rc::try_unwrap(self.0) {
 			Ok(data) => reqnot.request(api::FinalCall(data.api(), arg.id())).await,
 			Err(hand) => reqnot.request(api::CallRef(hand.api_ref(), arg.id())).await,
-		}
+		};
+		let mut parse_ctx = ExprParseCtx { ctx: owner_sys.ctx(), exprs: owner_sys.ext().exprs() };
+		let val = Expr::from_api(&ret, PathSetBuilder::new(), &mut parse_ctx).await;
+		owner_sys.ext().exprs().take_expr(arg.id());
+		val
 	}
 	#[must_use]
 	pub fn sys(&self) -> &System { &self.0.owner }
@@ -96,13 +85,19 @@ impl AtomHand {
 }
 impl Format for AtomHand {
 	async fn print<'a>(&'a self, _c: &'a (impl FmtCtx + ?Sized + 'a)) -> FmtUnit {
-		FmtUnit::from_api(&self.0.owner.reqnot().request(api::AtomPrint(self.0.api_ref())).await)
+		(self.0.display.get_or_init(|| async {
+			FmtUnit::from_api(&self.0.owner.reqnot().request(api::AtomPrint(self.0.api_ref())).await)
+		}))
+		.await
+		.clone()
 	}
 }
 impl AtomRepr for AtomHand {
 	type Ctx = Ctx;
-	async fn from_api(atom: &orchid_api::Atom, _: Pos, ctx: &mut Self::Ctx) -> Self {
-		Self::new(atom.clone(), ctx).await
+	async fn from_api(atom: &api::Atom, _: Pos, ctx: &mut Self::Ctx) -> Self {
+		let api::Atom { data, drop, owner } = atom.clone();
+		let sys = ctx.system_inst(owner).await.expect("Dropped system created atom");
+		if let Some(id) = drop { sys.new_atom(data, id).await } else { AtomHand::new(data, sys, drop) }
 	}
 	async fn to_api(&self) -> orchid_api::Atom { self.api_ref() }
 }
diff --git a/orchid-host/src/ctx.rs b/orchid-host/src/ctx.rs
index bb517bd..f653409 100644
--- a/orchid-host/src/ctx.rs
+++ b/orchid-host/src/ctx.rs
@@ -5,12 +5,10 @@ use std::{fmt, ops};
 
 use async_lock::RwLock;
 use hashbrown::HashMap;
-use orchid_api::SysId;
 use orchid_base::builtin::Spawner;
 use orchid_base::interner::Interner;
 
 use crate::api;
-use crate::atom::WeakAtomHand;
 use crate::expr_store::ExprStore;
 use crate::system::{System, WeakSystem};
 use crate::tree::WeakRoot;
@@ -20,7 +18,6 @@ pub struct CtxData {
 	pub spawn: Spawner,
 	pub systems: RwLock<HashMap<api::SysId, WeakSystem>>,
 	pub system_id: RefCell<NonZeroU16>,
-	pub owned_atoms: RwLock<HashMap<api::AtomId, WeakAtomHand>>,
 	pub common_exprs: ExprStore,
 	pub root: RwLock<WeakRoot>,
 }
@@ -46,7 +43,6 @@ impl Ctx {
 			i: Interner::default(),
 			systems: RwLock::default(),
 			system_id: RefCell::new(NonZero::new(1).unwrap()),
-			owned_atoms: RwLock::default(),
 			common_exprs: ExprStore::default(),
 			root: RwLock::default(),
 		}))
@@ -59,7 +55,7 @@ impl Ctx {
 	pub(crate) fn next_sys_id(&self) -> api::SysId {
 		let mut g = self.system_id.borrow_mut();
 		*g = g.checked_add(1).unwrap_or(NonZeroU16::new(1).unwrap());
-		SysId(*g)
+		api::SysId(*g)
 	}
 	#[must_use]
 	pub fn downgrade(&self) -> WeakCtx { WeakCtx(Rc::downgrade(&self.0)) }
diff --git a/orchid-host/src/execute.rs b/orchid-host/src/execute.rs
index 80b67a1..4744793 100644
--- a/orchid-host/src/execute.rs
+++ b/orchid-host/src/execute.rs
@@ -9,7 +9,7 @@ use orchid_base::location::Pos;
 use orchid_base::logging::Logger;
 
 use crate::ctx::Ctx;
-use crate::expr::{Expr, ExprKind, ExprParseCtx, PathSet, PathSetBuilder, Step};
+use crate::expr::{Expr, ExprKind, PathSet, Step};
 use crate::tree::Root;
 
 type ExprGuard = Bound<RwLockWriteGuard<'static, ExprKind>, Expr>;
@@ -109,11 +109,8 @@ impl ExecCtx {
 				ExprKind::Call(f, x) if !self.did_pop => (ExprKind::Call(f.clone(), x), StackOp::Push(f)),
 				ExprKind::Call(f, x) => match f.try_into_owned_atom().await {
 					Ok(atom) => {
-						let ext = atom.sys().ext().clone();
 						let x_norm = self.unpack_ident(&x).await;
-						let mut parse_ctx = ExprParseCtx { ctx: &self.ctx, exprs: ext.exprs() };
-						let val =
-							Expr::from_api(&atom.call(x_norm).await, PathSetBuilder::new(), &mut parse_ctx).await;
+						let val = atom.call(x_norm).await;
 						(ExprKind::Identity(val.clone()), StackOp::Swap(val))
 					},
 					Err(f) => match &*f.kind().read().await {
@@ -121,15 +118,9 @@ impl ExecCtx {
 							panic!("This should not appear outside function bodies"),
 						ExprKind::Missing => panic!("Should have been replaced"),
 						ExprKind::Atom(a) => {
-							let ext = a.sys().ext().clone();
 							let x_norm = self.unpack_ident(&x).await;
-							let val = Expr::from_api(
-								&a.clone().call(x_norm).await,
-								PathSetBuilder::new(),
-								&mut ExprParseCtx { ctx: ext.ctx(), exprs: ext.exprs() },
-							)
-							.await;
-							(ExprKind::Identity(val.clone()), StackOp::Swap(val))
+							let ret = a.clone().call(x_norm).await;
+							(ExprKind::Identity(ret.clone()), StackOp::Swap(ret))
 						},
 						ExprKind::Bottom(exprv) => (ExprKind::Bottom(exprv.clone()), StackOp::Pop),
 						ExprKind::Lambda(None, body) =>
diff --git a/orchid-host/src/expr.rs b/orchid-host/src/expr.rs
index 5d76c93..36e8e17 100644
--- a/orchid-host/src/expr.rs
+++ b/orchid-host/src/expr.rs
@@ -6,7 +6,6 @@ use std::{fmt, mem};
 
 use async_lock::RwLock;
 use futures::FutureExt;
-use hashbrown::HashSet;
 use itertools::Itertools;
 use orchid_base::error::OrcErrv;
 use orchid_base::format::{FmtCtx, FmtUnit, Format, Variants};
@@ -116,19 +115,18 @@ impl Expr {
 }
 impl Format for Expr {
 	async fn print<'a>(&'a self, c: &'a (impl FmtCtx + ?Sized + 'a)) -> FmtUnit {
-		return print_expr(self, c, &mut HashSet::new()).await;
+		return print_expr(self, c, Substack::Bottom).await;
 	}
 }
 async fn print_expr<'a>(
 	expr: &'a Expr,
 	c: &'a (impl FmtCtx + ?Sized + 'a),
-	visited: &mut HashSet<api::ExprTicket>,
+	visited: Substack<'_, api::ExprTicket>,
 ) -> FmtUnit {
-	if visited.contains(&expr.id()) {
+	if visited.iter().any(|id| id == &expr.id()) {
 		return "CYCLIC_EXPR".to_string().into();
 	}
-	visited.insert(expr.id());
-	print_exprkind(&*expr.kind().read().await, c, visited).boxed_local().await
+	print_exprkind(&*expr.kind().read().await, c, visited.push(expr.id())).boxed_local().await
 }
 
 #[derive(Clone, Debug)]
@@ -152,13 +150,13 @@ impl ExprKind {
 }
 impl Format for ExprKind {
 	async fn print<'a>(&'a self, c: &'a (impl FmtCtx + ?Sized + 'a)) -> FmtUnit {
-		print_exprkind(self, c, &mut HashSet::new()).await
+		print_exprkind(self, c, Substack::Bottom).await
 	}
 }
 async fn print_exprkind<'a>(
 	ek: &ExprKind,
 	c: &'a (impl FmtCtx + ?Sized + 'a),
-	visited: &mut HashSet<api::ExprTicket>,
+	visited: Substack<'_, api::ExprTicket>,
 ) -> FmtUnit {
 	match &ek {
 		ExprKind::Arg => "Arg".to_string().into(),
diff --git a/orchid-host/src/expr_store.rs b/orchid-host/src/expr_store.rs
index f706d13..f786771 100644
--- a/orchid-host/src/expr_store.rs
+++ b/orchid-host/src/expr_store.rs
@@ -28,9 +28,15 @@ impl ExprStore {
 			},
 		}
 	}
-	pub fn take_expr(&self, ticket: api::ExprTicket) {
-		(self.0.exprs.borrow_mut().entry(ticket))
-			.and_replace_entry_with(|_, (rc, rt)| (1 < rc).then_some((rc - 1, rt)));
+	pub fn take_expr(&self, ticket: api::ExprTicket) -> Option<Expr> {
+		match self.0.exprs.borrow_mut().entry(ticket) {
+			Entry::Vacant(_) => None,
+			Entry::Occupied(oe) if oe.get().0 == 1 => Some(oe.remove().1),
+			Entry::Occupied(mut oe) => {
+				oe.get_mut().0 -= 1;
+				Some(oe.get().1.clone())
+			},
+		}
 	}
 	#[must_use]
 	pub fn get_expr(&self, ticket: api::ExprTicket) -> Option<Expr> {
diff --git a/orchid-host/src/extension.rs b/orchid-host/src/extension.rs
index 542d09d..2a5d679 100644
--- a/orchid-host/src/extension.rs
+++ b/orchid-host/src/extension.rs
@@ -18,9 +18,11 @@ use orchid_base::builtin::ExtInit;
 use orchid_base::clone;
 use orchid_base::format::{FmtCtxImpl, Format};
 use orchid_base::interner::Tok;
+use orchid_base::location::Pos;
 use orchid_base::logging::Logger;
 use orchid_base::name::Sym;
 use orchid_base::reqnot::{DynRequester, ReqNot, Requester as _};
+use orchid_base::tree::AtomRepr;
 
 use crate::api;
 use crate::atom::AtomHand;
@@ -100,7 +102,7 @@ impl Extension {
 							}
 							api::ExtHostNotif::ExprNotif(api::ExprNotif::Release(rel)) => {
 								this.assert_own_sys(rel.0).await;
-								this.0.exprs.take_expr(rel.1)
+								this.0.exprs.take_expr(rel.1);
 							}
 							api::ExtHostNotif::ExprNotif(api::ExprNotif::Move(mov)) => {
 								this.assert_own_sys(mov.dec).await;
@@ -173,8 +175,8 @@ impl Extension {
 											let path = i.ex(path).await;
 											let root = (ctx.root.read().await.upgrade())
 												.expect("LSModule called when root isn't in context");
-											let root_data = &mut *root.0.write().await;
-											let mut walk_ctx = (ctx.clone(), &mut root_data.consts);
+											let root_data = &*root.0.read().await;
+											let mut walk_ctx = (ctx.clone(), &root_data.consts);
 											let module =
 												match walk(&root_data.root, false, path.iter().cloned(), &mut walk_ctx)
 													.await
@@ -189,7 +191,7 @@ impl Extension {
 												};
 											let mut members = std::collections::HashMap::new();
 											for (k, v) in &module.members {
-												let kind = match v.kind(ctx.clone(), &mut root_data.consts).await {
+												let kind = match v.kind(ctx.clone(), &root_data.consts).await {
 													MemberKind::Const => api::MemberInfoKind::Constant,
 													MemberKind::Module(_) => api::MemberInfoKind::Module,
 												};
@@ -221,7 +223,7 @@ impl Extension {
 										hand.handle(rn, &responses).await
 									},
 									api::ExtHostReq::ExtAtomPrint(ref eap @ api::ExtAtomPrint(ref atom)) => {
-										let atom = AtomHand::new(atom.clone(), &ctx).await;
+										let atom = AtomHand::from_api(atom, Pos::None, &mut ctx.clone()).await;
 										let unit = atom.print(&FmtCtxImpl { i: &this.ctx().i }).await;
 										hand.handle(eap, &unit.to_api()).await
 									},
diff --git a/orchid-host/src/lex.rs b/orchid-host/src/lex.rs
index 423b5bc..5786a14 100644
--- a/orchid-host/src/lex.rs
+++ b/orchid-host/src/lex.rs
@@ -8,12 +8,11 @@ use orchid_base::location::SrcRange;
 use orchid_base::name::Sym;
 use orchid_base::parse::{name_char, name_start, op_char, unrep_space};
 use orchid_base::tokens::PARENS;
-use orchid_base::tree::recur;
 
 use crate::api;
 use crate::ctx::Ctx;
-use crate::expr::{Expr, ExprParseCtx, ExprWillPanic};
-use crate::parsed::{ParsTok, ParsTokTree};
+use crate::expr::{Expr, ExprParseCtx};
+use crate::parsed::{ParsTok, ParsTokTree, tt_to_api};
 use crate::system::System;
 
 pub struct LexCtx<'a> {
@@ -54,14 +53,7 @@ impl<'a> LexCtx<'a> {
 	}
 	#[must_use]
 	pub async fn ser_subtree(&mut self, subtree: ParsTokTree) -> api::TokenTree {
-		let mut exprs = self.ctx.common_exprs.clone();
-		let without_new_expr = recur(subtree, &|tt, r| {
-			if let ParsTok::NewExpr(expr) = tt.tok {
-				return ParsTok::Handle(expr).at(tt.sr);
-			}
-			r(tt)
-		});
-		without_new_expr.into_api(&mut exprs, &mut ExprWillPanic).await
+		tt_to_api(&mut self.ctx.common_exprs.clone(), subtree).await
 	}
 	#[must_use]
 	pub async fn des_subtree(&mut self, tree: &api::TokenTree) -> ParsTokTree {
diff --git a/orchid-host/src/lib.rs b/orchid-host/src/lib.rs
index eb9617a..929a57d 100644
--- a/orchid-host/src/lib.rs
+++ b/orchid-host/src/lib.rs
@@ -11,5 +11,6 @@ pub mod lex;
 pub mod parse;
 pub mod parsed;
 pub mod subprocess;
+mod sys_parser;
 pub mod system;
 pub mod tree;
diff --git a/orchid-host/src/parse.rs b/orchid-host/src/parse.rs
index ac7d9a8..92d6c79 100644
--- a/orchid-host/src/parse.rs
+++ b/orchid-host/src/parse.rs
@@ -33,6 +33,7 @@ impl ParseCtx for HostParseCtxImpl<'_> {
 impl HostParseCtx for HostParseCtxImpl<'_> {
 	fn ctx(&self) -> &Ctx { &self.ctx }
 	fn systems(&self) -> impl Iterator<Item = &System> { self.systems.iter() }
+	fn src_path(&self) -> Sym { self.src.clone() }
 }
 
 pub trait HostParseCtx: ParseCtx {
@@ -40,6 +41,8 @@ pub trait HostParseCtx: ParseCtx {
 	fn ctx(&self) -> &Ctx;
 	#[must_use]
 	fn systems(&self) -> impl Iterator<Item = &System>;
+	#[must_use]
+	fn src_path(&self) -> Sym;
 }
 
 pub async fn parse_items(
@@ -109,9 +112,9 @@ pub async fn parse_exportable_item<'a>(
 	let kind = if discr == ctx.i().i("mod").await {
 		let (name, body) = parse_module(ctx, path, tail).await?;
 		ItemKind::Member(ParsedMember { name, exported, kind: ParsedMemberKind::Mod(body) })
-	} else if let Some(sys) = ctx.systems().find(|s| s.can_parse(discr.clone())) {
-		return sys
-			.parse(path, tail.to_vec(), exported, comments, &mut async |stack, lines| {
+	} else if let Some(parser) = ctx.systems().find_map(|s| s.get_parser(discr.clone())) {
+		return parser
+			.parse(ctx, path, tail.to_vec(), exported, comments, &mut async |stack, lines| {
 				let source = Snippet::new(lines.first().unwrap(), &lines);
 				parse_items(ctx, stack, source).await
 			})
diff --git a/orchid-host/src/parsed.rs b/orchid-host/src/parsed.rs
index c2bdc7c..bcb76b6 100644
--- a/orchid-host/src/parsed.rs
+++ b/orchid-host/src/parsed.rs
@@ -10,11 +10,12 @@ use orchid_base::interner::Tok;
 use orchid_base::location::SrcRange;
 use orchid_base::parse::{Comment, Import};
 use orchid_base::tl_cache;
-use orchid_base::tree::{TokTree, Token};
+use orchid_base::tree::{TokTree, Token, recur};
 
 use crate::api;
 use crate::dealias::{ChildErrorKind, ChildResult, Tree};
-use crate::expr::Expr;
+use crate::expr::{Expr, ExprWillPanic};
+use crate::expr_store::ExprStore;
 use crate::system::System;
 
 pub type ParsTokTree = TokTree<Expr, Expr>;
@@ -54,7 +55,7 @@ impl Format for Item {
 		let item_text = match &self.kind {
 			ItemKind::Import(i) => format!("import {i}").into(),
 			ItemKind::Member(mem) => match &mem.kind {
-				ParsedMemberKind::DeferredConst(_, sys) =>
+				ParsedMemberKind::Const(_, sys) =>
 					tl_cache!(Rc<Variants>: Rc::new(Variants::default().bounded("const {0} via {1}")))
 						.units([mem.name.rc().into(), sys.print(c).await]),
 				ParsedMemberKind::Mod(module) =>
@@ -106,7 +107,7 @@ impl fmt::Debug for ParsedExpr {
 
 #[derive(Debug)]
 pub enum ParsedMemberKind {
-	DeferredConst(api::ParsedConstId, System),
+	Const(api::ParsedConstId, System),
 	Mod(ParsedModule),
 }
 impl From<ParsedModule> for ParsedMemberKind {
@@ -162,7 +163,7 @@ impl Tree for ParsedModule {
 			.find(|m| m.name == key)
 		{
 			match &member.kind {
-				ParsedMemberKind::DeferredConst(..) => return ChildResult::Err(ChildErrorKind::Constant),
+				ParsedMemberKind::Const(..) => return ChildResult::Err(ChildErrorKind::Constant),
 				ParsedMemberKind::Mod(m) => return ChildResult::Ok(m),
 			}
 		}
@@ -191,15 +192,6 @@ impl Format for ParsedModule {
 	}
 }
 
-/// TODO:
-///
-/// idea, does the host need an IR here or can we figure out a way to transcribe
-/// these? Should we spin off a new stage for value parsing so that ParsTokTree
-/// doesn't appear in the interpreter's ingress?
-pub struct Const {
-	pub source: Option<Vec<ParsTokTree>>,
-}
-
 /// Selects a code element
 ///
 /// Either the steps point to a constant and rule_loc is None, or the steps
@@ -212,3 +204,13 @@ impl ConstPath {
 	#[must_use]
 	pub fn to_const(steps: Tok<Vec<Tok<String>>>) -> Self { Self { steps } }
 }
+
+pub async fn tt_to_api(exprs: &mut ExprStore, subtree: ParsTokTree) -> api::TokenTree {
+	let without_new_expr = recur(subtree, &|tt, r| {
+		if let ParsTok::NewExpr(expr) = tt.tok {
+			return ParsTok::Handle(expr).at(tt.sr);
+		}
+		r(tt)
+	});
+	without_new_expr.into_api(exprs, &mut ExprWillPanic).await
+}
diff --git a/orchid-host/src/sys_parser.rs b/orchid-host/src/sys_parser.rs
new file mode 100644
index 0000000..9805498
--- /dev/null
+++ b/orchid-host/src/sys_parser.rs
@@ -0,0 +1,119 @@
+use futures::FutureExt;
+use futures::future::join_all;
+use itertools::Itertools;
+use orchid_base::error::{OrcErrv, OrcRes};
+use orchid_base::interner::{Interner, Tok};
+use orchid_base::location::SrcRange;
+use orchid_base::name::Sym;
+use orchid_base::parse::Comment;
+use orchid_base::reqnot::Requester;
+use orchid_base::tree::ttv_from_api;
+use substack::Substack;
+
+use crate::api;
+use crate::expr::ExprParseCtx;
+use crate::expr_store::ExprStore;
+use crate::parse::HostParseCtx;
+use crate::parsed::{
+	Item, ItemKind, ParsTokTree, ParsedMember, ParsedMemberKind, ParsedModule, tt_to_api,
+};
+use crate::system::System;
+
+pub struct Parser {
+	pub(crate) system: System,
+	pub(crate) idx: u16,
+}
+type ModPath<'a> = Substack<'a, Tok<String>>;
+
+impl Parser {
+	pub async fn parse(
+		&self,
+		ctx: &impl HostParseCtx,
+		path: ModPath<'_>,
+		line: Vec<ParsTokTree>,
+		exported: bool,
+		comments: Vec<Comment>,
+		callback: &mut impl AsyncFnMut(ModPath<'_>, Vec<ParsTokTree>) -> OrcRes<Vec<Item>>,
+	) -> OrcRes<Vec<Item>> {
+		let src_path = line.first().expect("cannot be empty").sr.path();
+		let line = join_all(
+			(line.into_iter())
+				.map(|t| async { tt_to_api(&mut self.system.ext().exprs().clone(), t).await }),
+		)
+		.await;
+		let mod_path = ctx.src_path().suffix(path.unreverse(), self.system.i()).await;
+		let comments = comments.iter().map(Comment::to_api).collect_vec();
+		let req = api::ParseLine {
+			idx: self.idx,
+			module: mod_path.to_api(),
+			src: src_path.to_api(),
+			exported,
+			sys: self.system.id(),
+			comments,
+			line,
+		};
+		match self.system.reqnot().request(req).await {
+			Ok(parsed_v) => {
+				let mut ext_exprs = self.system.ext().exprs().clone();
+				conv(parsed_v, path, callback, &mut ConvCtx {
+					i: self.system.i(),
+					mod_path: &mod_path,
+					ext_exprs: &mut ext_exprs,
+					pctx: &mut ExprParseCtx { ctx: self.system.ctx(), exprs: self.system.ext().exprs() },
+					src_path: &src_path,
+					sys: &self.system,
+				})
+				.await
+			},
+			Err(e) => Err(OrcErrv::from_api(&e, &self.system.ctx().i).await),
+		}
+	}
+}
+
+struct ConvCtx<'a> {
+	sys: &'a System,
+	mod_path: &'a Sym,
+	src_path: &'a Sym,
+	i: &'a Interner,
+	ext_exprs: &'a mut ExprStore,
+	pctx: &'a mut ExprParseCtx<'a>,
+}
+async fn conv(
+	parsed_v: Vec<api::ParsedLine>,
+	module: Substack<'_, Tok<String>>,
+	callback: &'_ mut impl AsyncFnMut(Substack<'_, Tok<String>>, Vec<ParsTokTree>) -> OrcRes<Vec<Item>>,
+	ctx: &mut ConvCtx<'_>,
+) -> OrcRes<Vec<Item>> {
+	let mut items = Vec::new();
+	for parsed in parsed_v {
+		let (name, exported, kind) = match parsed.kind {
+			api::ParsedLineKind::Member(api::ParsedMember { name, exported, kind }) =>
+				(name, exported, kind),
+			api::ParsedLineKind::Recursive(rec) => {
+				let tokens = ttv_from_api(rec, ctx.ext_exprs, ctx.pctx, ctx.src_path, ctx.i).await;
+				items.extend(callback(module.clone(), tokens).await?);
+				continue;
+			},
+		};
+		let name = ctx.i.ex(name).await;
+		let mkind = match kind {
+			api::ParsedMemberKind::Module { lines, use_prelude } => {
+				let items = conv(lines, module.push(name.clone()), callback, ctx).boxed_local().await?;
+				ParsedMemberKind::Mod(ParsedModule::new(use_prelude, items))
+			},
+			api::ParsedMemberKind::Constant(cid) => {
+				ctx.sys.0.const_paths.insert(cid, ctx.mod_path.suffix(module.unreverse(), ctx.i).await);
+				ParsedMemberKind::Const(cid, ctx.sys.clone())
+			},
+		};
+		items.push(Item {
+			comments: join_all(
+				parsed.comments.iter().map(|c| Comment::from_api(c, ctx.src_path.clone(), ctx.i)),
+			)
+			.await,
+			sr: SrcRange::from_api(&parsed.source_range, ctx.i).await,
+			kind: ItemKind::Member(ParsedMember { name, exported, kind: mkind }),
+		})
+	}
+	Ok(items)
+}
diff --git a/orchid-host/src/system.rs b/orchid-host/src/system.rs
index 00bf53c..a1019df 100644
--- a/orchid-host/src/system.rs
+++ b/orchid-host/src/system.rs
@@ -3,38 +3,32 @@ use std::fmt;
 use std::future::Future;
 use std::rc::{Rc, Weak};
 
+use async_lock::RwLock;
 use derive_destructure::destructure;
-use futures::FutureExt;
 use futures::future::join_all;
 use hashbrown::HashMap;
 use itertools::Itertools;
 use memo_map::MemoMap;
 use orchid_base::char_filter::char_filter_match;
-use orchid_base::error::{OrcErrv, OrcRes, mk_errv_floating};
+use orchid_base::error::{OrcRes, mk_errv_floating};
 use orchid_base::format::{FmtCtx, FmtUnit, Format};
 use orchid_base::interner::{Interner, Tok};
 use orchid_base::iter_utils::IteratorPrint;
-use orchid_base::location::SrcRange;
 use orchid_base::name::{NameLike, Sym, VName, VPath};
-use orchid_base::parse::Comment;
 use orchid_base::reqnot::{ReqNot, Requester};
-use orchid_base::tree::{recur, ttv_from_api};
 use ordered_float::NotNan;
 use substack::{Stackframe, Substack};
 
 use crate::api;
+use crate::atom::{AtomHand, WeakAtomHand};
 use crate::ctx::Ctx;
 use crate::dealias::walk;
-use crate::expr::{ExprParseCtx, ExprWillPanic};
-use crate::expr_store::ExprStore;
 use crate::extension::{Extension, WeakExtension};
-use crate::parsed::{
-	Item, ItemKind, ParsTok, ParsTokTree, ParsedMember, ParsedMemberKind, ParsedModule,
-};
+use crate::sys_parser::Parser;
 use crate::tree::Root;
 
 #[derive(destructure)]
-struct SystemInstData {
+pub(crate) struct SystemInstData {
 	deps: Vec<System>,
 	ctx: Ctx,
 	ext: Extension,
@@ -43,6 +37,7 @@ struct SystemInstData {
 	id: api::SysId,
 	line_types: Vec<Tok<String>>,
 	prelude: Vec<Sym>,
+	owned_atoms: RwLock<HashMap<api::AtomId, WeakAtomHand>>,
 	pub(crate) const_paths: MemoMap<api::ParsedConstId, Sym>,
 }
 impl Drop for SystemInstData {
@@ -60,7 +55,7 @@ impl fmt::Debug for SystemInstData {
 }
 
 #[derive(Clone, Debug)]
-pub struct System(Rc<SystemInstData>);
+pub struct System(pub(crate) Rc<SystemInstData>);
 impl System {
 	#[must_use]
 	pub fn id(&self) -> api::SysId { self.0.id }
@@ -101,108 +96,32 @@ impl System {
 		self.0.ext.lex_req(source, src, pos, self.id(), r).await
 	}
 	#[must_use]
-	pub fn can_parse(&self, ltyp: Tok<String>) -> bool { self.0.line_types.contains(&ltyp) }
-	pub fn line_types(&self) -> impl Iterator<Item = &Tok<String>> + '_ { self.0.line_types.iter() }
-	pub async fn parse(
-		&self,
-		path: Substack<'_, Tok<String>>,
-		line: Vec<ParsTokTree>,
-		exported: bool,
-		comments: Vec<Comment>,
-		callback: &mut impl AsyncFnMut(Substack<'_, Tok<String>>, Vec<ParsTokTree>) -> OrcRes<Vec<Item>>,
-	) -> OrcRes<Vec<Item>> {
-		let src_path = line.first().expect("cannot be empty").sr.path();
-		let line = join_all(line.into_iter().map(|t| async {
-			let mut expr_store = self.0.ext.exprs().clone();
-			let without_new_expr = recur(t, &|t, r| {
-				if let ParsTok::NewExpr(expr) = t.tok {
-					return ParsTok::Handle(expr).at(t.sr);
-				}
-				r(t)
-			});
-			without_new_expr.into_api(&mut expr_store, &mut ExprWillPanic).await
-		}))
-		.await;
-		let comments = comments.iter().map(Comment::to_api).collect_vec();
-		let req = api::ParseLine {
-			module: self.i().i(&path.unreverse()).await.to_api(),
-			src: src_path.to_api(),
-			exported,
-			sys: self.id(),
-			comments,
-			line,
-		};
-		match self.reqnot().request(req).await {
-			Ok(parsed_v) => {
-				let mut ext_exprs = self.ext().exprs().clone();
-				struct ConvCtx<'a> {
-					sys: &'a System,
-					src_path: &'a Sym,
-					i: &'a Interner,
-					ext_exprs: &'a mut ExprStore,
-					pctx: &'a mut ExprParseCtx<'a>,
-				}
-				async fn conv(
-					parsed_v: Vec<api::ParsedLine>,
-					module: Substack<'_, Tok<String>>,
-					callback: &'_ mut impl AsyncFnMut(
-						Substack<'_, Tok<String>>,
-						Vec<ParsTokTree>,
-					) -> OrcRes<Vec<Item>>,
-					ctx: &mut ConvCtx<'_>,
-				) -> OrcRes<Vec<Item>> {
-					let mut items = Vec::new();
-					for parsed in parsed_v {
-						let (name, exported, kind) = match parsed.kind {
-							api::ParsedLineKind::Member(api::ParsedMember { name, exported, kind }) =>
-								(name, exported, kind),
-							api::ParsedLineKind::Recursive(rec) => {
-								let tokens = ttv_from_api(rec, ctx.ext_exprs, ctx.pctx, ctx.src_path, ctx.i).await;
-								items.extend(callback(module.clone(), tokens).await?);
-								continue;
-							},
-						};
-						let name = ctx.i.ex(name).await;
-						let mkind = match kind {
-							api::ParsedMemberKind::Module { lines, use_prelude } => {
-								let items =
-									conv(lines, module.push(name.clone()), callback, ctx).boxed_local().await?;
-								ParsedMemberKind::Mod(ParsedModule::new(use_prelude, items))
-							},
-							api::ParsedMemberKind::Constant(cid) =>
-								ParsedMemberKind::DeferredConst(cid, ctx.sys.clone()),
-						};
-						items.push(Item {
-							comments: join_all(
-								parsed.comments.iter().map(|c| Comment::from_api(c, ctx.src_path.clone(), ctx.i)),
-							)
-							.await,
-							sr: SrcRange::from_api(&parsed.source_range, ctx.i).await,
-							kind: ItemKind::Member(ParsedMember { name, exported, kind: mkind }),
-						})
-					}
-					Ok(items)
-				}
-				conv(parsed_v, path, callback, &mut ConvCtx {
-					i: self.i(),
-					ext_exprs: &mut ext_exprs,
-					pctx: &mut ExprParseCtx { ctx: self.ctx(), exprs: self.ext().exprs() },
-					src_path: &src_path,
-					sys: self,
-				})
-				.await
-			},
-			Err(e) => Err(OrcErrv::from_api(&e, &self.ctx().i).await),
-		}
+	pub fn get_parser(&self, ltyp: Tok<String>) -> Option<Parser> {
+		(self.0.line_types.iter().enumerate())
+			.find(|(_, txt)| *txt == &ltyp)
+			.map(|(idx, _)| Parser { idx: idx as u16, system: self.clone() })
 	}
+	pub fn line_types(&self) -> impl Iterator<Item = &Tok<String>> + '_ { self.0.line_types.iter() }
+
 	#[must_use]
 	pub async fn request(&self, req: Vec<u8>) -> Vec<u8> {
 		self.reqnot().request(api::SysFwded(self.id(), req)).await
 	}
+	pub(crate) async fn new_atom(&self, data: Vec<u8>, id: api::AtomId) -> AtomHand {
+		let mut owned_g = self.0.owned_atoms.write().await;
+		if let Some(data) = owned_g.get(&id)
+			&& let Some(atom) = data.upgrade()
+		{
+			return atom;
+		}
+		let new = AtomHand::new(data, self.clone(), Some(id));
+		owned_g.insert(id, new.downgrade());
+		new
+	}
 	pub(crate) fn drop_atom(&self, drop: api::AtomId) {
 		let this = self.0.clone();
 		(self.0.ctx.spawn)(Box::pin(async move {
-			this.ctx.owned_atoms.write().await.remove(&drop);
+			this.owned_atoms.write().await.remove(&drop);
 		}))
 	}
 	#[must_use]
@@ -218,7 +137,7 @@ impl System {
 		async move |rel| {
 			let cwd = orig.split_last_seg().1;
 			let root_data = &mut *root.0.write().await;
-			let walk_ctx = &mut (ctx.clone(), &mut root_data.consts);
+			let walk_ctx = &mut (ctx.clone(), &root_data.consts);
 			let cmod = (walk(&root_data.root, false, cwd.iter().cloned(), walk_ctx).await)
 				.expect("the parent module of a constant should exist");
 			let (selector, tail) = rel.split_first().expect("Names cannot be empty");
@@ -298,6 +217,7 @@ impl SystemCtor {
 				.await,
 			id,
 			prelude: join_all(sys_inst.prelude.iter().map(|tok| Sym::from_api(*tok, &ext.ctx().i))).await,
+			owned_atoms: RwLock::new(HashMap::new()),
 			const_paths: MemoMap::new(),
 		}));
 		let api_module_root = api::Module {
diff --git a/orchid-host/src/tree.rs b/orchid-host/src/tree.rs
index 51b10e6..0821bbb 100644
--- a/orchid-host/src/tree.rs
+++ b/orchid-host/src/tree.rs
@@ -10,6 +10,7 @@ use futures::{FutureExt, StreamExt, stream};
 use hashbrown::HashMap;
 use hashbrown::hash_map::Entry;
 use itertools::Itertools;
+use memo_map::MemoMap;
 use orchid_base::clone;
 use orchid_base::error::{OrcRes, Reporter, mk_errv};
 use orchid_base::interner::Tok;
@@ -26,7 +27,7 @@ use crate::system::System;
 
 pub struct RootData {
 	pub root: Module,
-	pub consts: HashMap<Sym, Expr>,
+	pub consts: MemoMap<Sym, Expr>,
 	pub ctx: Ctx,
 }
 #[derive(Clone)]
@@ -36,23 +37,25 @@ impl Root {
 	pub fn new(ctx: Ctx) -> Self {
 		Root(Rc::new(RwLock::new(RootData {
 			root: Module::default(),
-			consts: HashMap::default(),
+			consts: MemoMap::default(),
 			ctx,
 		})))
 	}
 	#[must_use]
 	pub async fn from_api(api: api::Module, sys: &System) -> Self {
-		let mut consts = HashMap::new();
-		let mut tfac = TreeFromApiCtx { consts: &mut consts, path: sys.i().i(&[][..]).await, sys };
+		let consts = MemoMap::new();
+		let mut tfac = TreeFromApiCtx { consts: &consts, path: sys.i().i(&[][..]).await, sys };
 		let root = Module::from_api(api, &mut tfac).await;
 		Root(Rc::new(RwLock::new(RootData { root, consts, ctx: sys.ctx().clone() })))
 	}
 	pub async fn merge(&self, new: &Root) -> Result<Self, MergeErr> {
-		let this = self.0.read().await;
-		let that = new.0.read().await;
-		let mut consts =
-			this.consts.iter().chain(&that.consts).map(|(k, v)| (k.clone(), v.clone())).collect();
-		let root = this.root.merge(&that.root, this.ctx.clone(), &mut consts).await?;
+		let this = self.0.write().await;
+		let that = new.0.write().await;
+		let consts = MemoMap::new();
+		for (k, v) in this.consts.iter().chain(that.consts.iter()) {
+			consts.insert(k.clone(), v.clone());
+		}
+		let root = this.root.merge(&that.root, this.ctx.clone(), &consts).await?;
 		Ok(Self(Rc::new(RwLock::new(RootData { root, consts, ctx: this.ctx.clone() }))))
 	}
 	#[must_use]
@@ -60,11 +63,11 @@ impl Root {
 		let mut ref_this = self.0.write().await;
 		let this = &mut *ref_this;
 		let mut deferred_consts = HashMap::new();
-		let mut consts = this.consts.clone();
+		let consts = this.consts.clone();
 		let mut tfpctx = FromParsedCtx {
 			pars_root: parsed,
 			deferred_consts: &mut deferred_consts,
-			consts: &mut consts,
+			consts: &consts,
 			pars_prefix: pars_prefix.clone(),
 			root: &this.root,
 			ctx: &this.ctx,
@@ -79,7 +82,7 @@ impl Root {
 			)]);
 			module = Module { imports: HashMap::new(), members }
 		}
-		let root = (this.root.merge(&module, this.ctx.clone(), &mut consts).await)
+		let root = (this.root.merge(&module, this.ctx.clone(), &consts).await)
 			.expect("Merge conflict between parsed and existing module");
 		let new = Root(Rc::new(RwLock::new(RootData { root, consts, ctx: this.ctx.clone() })));
 		*this.ctx.root.write().await = new.downgrade();
@@ -93,7 +96,7 @@ impl Root {
 		new
 	}
 	pub async fn get_const_value(&self, name: Sym, pos: Pos) -> OrcRes<Expr> {
-		let this = &mut *self.0.write().await;
+		let this = &*self.0.read().await;
 		// shortcut for previously visited
 		if let Some(val) = this.consts.get(&name) {
 			return Ok(val.clone());
@@ -101,7 +104,7 @@ impl Root {
 		// load the node, then check if this "walk" call added it to the map
 		let ctx = this.ctx.clone();
 		let module =
-			walk(&this.root, false, name.iter().cloned(), &mut (ctx.clone(), &mut this.consts)).await;
+			walk(&this.root, false, name.iter().cloned(), &mut (ctx.clone(), &this.consts)).await;
 		if let Some(val) = this.consts.get(&name) {
 			return Ok(val.clone());
 		}
@@ -140,14 +143,14 @@ impl Default for WeakRoot {
 
 pub struct TreeFromApiCtx<'a> {
 	pub sys: &'a System,
-	pub consts: &'a mut HashMap<Sym, Expr>,
+	pub consts: &'a MemoMap<Sym, Expr>,
 	pub path: Tok<Vec<Tok<String>>>,
 }
 impl<'a> TreeFromApiCtx<'a> {
 	#[must_use]
-	pub async fn push<'c>(&'c mut self, name: Tok<String>) -> TreeFromApiCtx<'c> {
+	pub async fn push<'c>(&'c self, name: Tok<String>) -> TreeFromApiCtx<'c> {
 		let path = self.sys.ctx().i.i(&self.path.iter().cloned().chain([name]).collect_vec()).await;
-		TreeFromApiCtx { path, consts: &mut *self.consts, sys: self.sys }
+		TreeFromApiCtx { path, consts: self.consts, sys: self.sys }
 	}
 }
 
@@ -208,7 +211,7 @@ impl Module {
 				Ok(abs_path) => {
 					let names_res = match abs_path.strip_prefix(&ctx.pars_prefix[..]) {
 						None => {
-							let mut tree_ctx = (ctx.ctx.clone(), &mut *ctx.consts);
+							let mut tree_ctx = (ctx.ctx.clone(), ctx.consts);
 							resolv_glob(&path, ctx.root, &abs_path, pos, &ctx.ctx.i, &mut tree_ctx).await
 						},
 						Some(sub_tgt) => {
@@ -322,7 +325,7 @@ impl Module {
 		&self,
 		other: &Module,
 		ctx: Ctx,
-		consts: &mut HashMap<Sym, Expr>,
+		consts: &MemoMap<Sym, Expr>,
 	) -> Result<Module, MergeErr> {
 		if !self.imports.is_empty() || !other.imports.is_empty() {
 			return Err(MergeErr { path: VPath::new([]), kind: MergeErrKind::Imports });
@@ -385,12 +388,12 @@ pub struct FromParsedCtx<'a> {
 	root: &'a Module,
 	rep: &'a Reporter,
 	ctx: &'a Ctx,
-	consts: &'a mut HashMap<Sym, Expr>,
+	consts: &'a MemoMap<Sym, Expr>,
 	deferred_consts: &'a mut HashMap<Sym, (api::SysId, api::ParsedConstId)>,
 }
 
 impl Tree for Module {
-	type Ctx<'a> = (Ctx, &'a mut HashMap<Sym, Expr>);
+	type Ctx<'a> = (Ctx, &'a MemoMap<Sym, Expr>);
 	async fn child(
 		&self,
 		key: Tok<String>,
@@ -420,7 +423,7 @@ pub struct Member {
 }
 impl Member {
 	#[must_use]
-	pub async fn kind<'a>(&'a self, ctx: Ctx, consts: &mut HashMap<Sym, Expr>) -> &'a MemberKind {
+	pub async fn kind<'a>(&'a self, ctx: Ctx, consts: &MemoMap<Sym, Expr>) -> &'a MemberKind {
 		(self.kind.get_or_init(async {
 			let handle = self.lazy.borrow_mut().take().expect("If kind is uninit, lazy must be Some");
 			handle.run(ctx, consts).await
@@ -437,7 +440,7 @@ impl MemberKind {
 	#[must_use]
 	async fn from_parsed(parsed: &ParsedMemberKind, path: Sym, ctx: &mut FromParsedCtx<'_>) -> Self {
 		match parsed {
-			ParsedMemberKind::DeferredConst(id, sys) => {
+			ParsedMemberKind::Const(id, sys) => {
 				ctx.deferred_consts.insert(path, (sys.id(), *id));
 				MemberKind::Const
 			},
@@ -454,12 +457,13 @@ pub struct LazyMemberHandle {
 }
 impl LazyMemberHandle {
 	#[must_use]
-	pub async fn run(self, ctx: Ctx, consts: &mut HashMap<Sym, Expr>) -> MemberKind {
+	pub async fn run(self, ctx: Ctx, consts: &MemoMap<Sym, Expr>) -> MemberKind {
 		let sys = ctx.system_inst(self.sys).await.expect("Missing system for lazy member");
 		match sys.get_tree(self.id).await {
 			api::MemberKind::Const(c) => {
 				let mut pctx = ExprParseCtx { ctx: &ctx, exprs: sys.ext().exprs() };
-				consts.insert(self.path, Expr::from_api(&c, PathSetBuilder::new(), &mut pctx).await);
+				let expr = Expr::from_api(&c, PathSetBuilder::new(), &mut pctx).await;
+				consts.insert(self.path, expr);
 				MemberKind::Const
 			},
 			api::MemberKind::Module(m) => MemberKind::Module(
diff --git a/orchid-std/src/macros/let_line.rs b/orchid-std/src/macros/let_line.rs
index 636049a..d0d884c 100644
--- a/orchid-std/src/macros/let_line.rs
+++ b/orchid-std/src/macros/let_line.rs
@@ -3,13 +3,13 @@ use std::pin::pin;
 use futures::{FutureExt, StreamExt, stream};
 use hashbrown::HashMap;
 use itertools::Itertools;
-use orchid_api::Paren;
 use orchid_base::error::{OrcRes, Reporter};
 use orchid_base::name::Sym;
 use orchid_base::parse::{
 	Comment, ParseCtx, Parsed, Snippet, expect_tok, token_errv, try_pop_no_fluff,
 };
 use orchid_base::sym;
+use orchid_base::tree::Paren;
 use orchid_extension::gen_expr::{atom, call, sym_ref};
 use orchid_extension::parser::{ConstCtx, PSnippet, PTok, PTokTree, ParsCtx, ParsedLine, Parser};
 
diff --git a/orchid-std/src/macros/macro_lib.rs b/orchid-std/src/macros/macro_lib.rs
index a1c01b5..e2507bd 100644
--- a/orchid-std/src/macros/macro_lib.rs
+++ b/orchid-std/src/macros/macro_lib.rs
@@ -32,7 +32,7 @@ pub fn gen_macro_lib() -> Vec<GenMember> {
 		),
 		fun(true, "resolve", |tpl: TypAtom<MacTree>| async move {
 			call([
-				sym_ref(sym!(macro::resolve_recur; tpl.untyped.ctx().i()).await),
+				sym_ref(sym!(macros::resolve_recur; tpl.untyped.ctx().i()).await),
 				atom(RecurState::Bottom),
 				tpl.untyped.ex().to_expr().await,
 			])
@@ -43,7 +43,7 @@ pub fn gen_macro_lib() -> Vec<GenMember> {
 			if let Some(e) = Reporter::new().errv() { Err(e) } else { Ok(res) }
 		}),
 		fun(true, "resolve_recur", |state: TypAtom<RecurState>, tpl: TypAtom<MacTree>| async move {
-			exec(async move |mut h| {
+			exec("macros::resolve_recur", async move |mut h| {
 				let ctx = tpl.ctx().clone();
 				let root = refl(&ctx);
 				let tpl = own(tpl.clone()).await;
diff --git a/orchid-std/src/macros/macro_line.rs b/orchid-std/src/macros/macro_line.rs
index 12c200a..03dc51a 100644
--- a/orchid-std/src/macros/macro_line.rs
+++ b/orchid-std/src/macros/macro_line.rs
@@ -7,7 +7,6 @@ use futures::{StreamExt, stream};
 use hashbrown::{HashMap, HashSet};
 use itertools::Itertools;
 use never::Never;
-use orchid_api::Paren;
 use orchid_base::error::{OrcRes, Reporter, mk_errv};
 use orchid_base::interner::Tok;
 use orchid_base::location::Pos;
@@ -16,7 +15,7 @@ use orchid_base::parse::{
 	Comment, ParseCtx, Parsed, Snippet, expect_end, expect_tok, line_items, token_errv,
 	try_pop_no_fluff,
 };
-use orchid_base::tree::Token;
+use orchid_base::tree::{Paren, Token};
 use orchid_base::{clone, sym};
 use orchid_extension::atom::{Atomic, TypAtom};
 use orchid_extension::atom_owned::{OwnedAtom, OwnedVariant};
@@ -142,7 +141,7 @@ impl Parser for MacroLine {
 					return Err(e);
 				}
 				Ok(call([
-					sym_ref(sym!(macro::resolve_recur; ctx.i()).await),
+					sym_ref(sym!(macros::resolve_recur; ctx.i()).await),
 					atom(RecurState::base(path)),
 					macro_input.to_expr().await,
 				]))
diff --git a/orchid-std/src/macros/mactree.rs b/orchid-std/src/macros/mactree.rs
index 6ecd7c6..519c5ab 100644
--- a/orchid-std/src/macros/mactree.rs
+++ b/orchid-std/src/macros/mactree.rs
@@ -6,14 +6,13 @@ use futures::FutureExt;
 use futures::future::join_all;
 use hashbrown::HashSet;
 use itertools::Itertools;
-use orchid_api::Paren;
 use orchid_base::error::{OrcErrv, Reporter, mk_errv};
 use orchid_base::format::{FmtCtx, FmtUnit, Format, Variants, fmt};
 use orchid_base::interner::Tok;
 use orchid_base::location::Pos;
 use orchid_base::name::Sym;
 use orchid_base::tl_cache;
-use orchid_base::tree::indent;
+use orchid_base::tree::{Paren, indent};
 use orchid_extension::atom::Atomic;
 use orchid_extension::atom_owned::{OwnedAtom, OwnedVariant};
 use orchid_extension::conv::ToExpr;
diff --git a/orchid-std/src/macros/resolve.rs b/orchid-std/src/macros/resolve.rs
index 5420459..633f9ab 100644
--- a/orchid-std/src/macros/resolve.rs
+++ b/orchid-std/src/macros/resolve.rs
@@ -39,26 +39,29 @@ pub async fn resolve_seq(ctx: &mut ResolveCtx<'_>, val: &[MacTree]) -> Option<Ve
 	let mut any_changed = false;
 	let mut i = 0;
 	let mut val = val.to_vec();
-	while i < val.len() {
-		let MacTok::Name(key) = val[i].tok() else { continue };
-		let Some(options) = ctx.named.get(key) else { continue };
-		let matches = (options.iter())
-			.filter_map(|r| Some((r.1, r.2, r.0.apply(&val[i..], |_| false)?)))
-			.collect_vec();
-		match matches.len() {
-			0 => i += 1,
-			1 => {
-				any_changed = true;
-				let (mac, rule, (state, tail)) = matches.into_iter().exactly_one().unwrap();
-				let end = val.len() - tail.len();
-				let new_i = val.len() - tail.len();
-				let body_call = mk_body_call(mac, rule, &state, &ctx.ctx, ctx.recur.clone()).await;
-				std::mem::drop(state);
-				val.splice(i..end, [MacTok::Value(ctx.h.register(body_call).await).at(Pos::None)]);
-				i = new_i;
-			},
-			2.. => todo!("Named macros conflict!"),
+	'all_named: while i < val.len() {
+		'one_named: {
+			let MacTok::Name(key) = val[i].tok() else { break 'one_named };
+			let Some(options) = ctx.named.get(key) else { break 'one_named };
+			let matches = (options.iter())
+				.filter_map(|r| Some((r.1, r.2, r.0.apply(&val[i..], |_| false)?)))
+				.collect_vec();
+			match matches.len() {
+				0 => break 'one_named,
+				1 => {
+					any_changed = true;
+					let (mac, rule, (state, tail)) = matches.into_iter().exactly_one().unwrap();
+					let end = val.len() - tail.len();
+					let body_call = mk_body_call(mac, rule, &state, &ctx.ctx, ctx.recur.clone()).await;
+					std::mem::drop(state);
+					val.splice(i..end, [MacTok::Value(ctx.h.register(body_call).await).at(Pos::None)]);
+					i = end;
+				},
+				2.. => todo!("Named macros conflict!"),
+			}
+			continue 'all_named;
 		}
+		i += 1;
 	}
 	for (matcher, mac, rule) in &ctx.priod {
 		let Some(state) = matcher.apply(&val, |_| false) else { continue };
diff --git a/orcx/src/main.rs b/orcx/src/main.rs
index 9214410..bb3ac80 100644
--- a/orcx/src/main.rs
+++ b/orcx/src/main.rs
@@ -228,7 +228,7 @@ async fn main() -> io::Result<ExitCode> {
 			},
 			Commands::Exec { proj, code } => {
 				let reporter = Reporter::new();
-				let path = sym!(usercode::entrypoint; i).await;
+				let path = sym!(usercode; i).await;
 				let prefix_sr = SrcRange::zw(path.clone(), 0);
 				let (mut root, systems) = init_systems(&args.system, &extensions).await.unwrap();
 				if let Some(proj_path) = proj {
diff --git a/xtask/src/check_api_refs.rs b/xtask/src/check_api_refs.rs
index 66b77dc..088871a 100644
--- a/xtask/src/check_api_refs.rs
+++ b/xtask/src/check_api_refs.rs
@@ -20,7 +20,7 @@ pub fn check_api_refs(_args: &Args) -> io::Result<()> {
 					continue;
 				}
 				let dname = file.path().to_string_lossy().to_string();
-				eprintln!("orchid_api imported in {dname} at {};{}", l + 1, c + 1)
+				eprintln!("orchid_api imported in {dname}:{}:{}", l + 1, c + 1)
 			}
 		}
 		Ok(())
diff --git a/xtask/src/orcx.rs b/xtask/src/orcx.rs
index dd9e698..f0d7d5b 100644
--- a/xtask/src/orcx.rs
+++ b/xtask/src/orcx.rs
@@ -5,18 +5,23 @@ use std::sync::atomic::Ordering;
 use crate::{Args, EXIT_OK};
 
 pub fn orcx(_args: &Args, argv: &[String]) -> io::Result<()> {
-	if !Command::new("cargo").args(["build", "-p", "orchid-std"]).status()?.success() {
+	if !Command::new("cargo").args(["build", "-p", "orchid-std", "--quiet"]).status()?.success() {
 		EXIT_OK.store(false, Ordering::Relaxed);
 		return Ok(());
 	}
-	if !Command::new("cargo").args(["run", "-p", "orcx", "--"]).args(argv).status()?.success() {
+	if !Command::new("cargo")
+		.args(["run", "-p", "orcx", "--quiet", "--"])
+		.args(argv)
+		.status()?
+		.success()
+	{
 		EXIT_OK.store(false, Ordering::Relaxed);
 	}
 	Ok(())
 }
 
 pub fn orcxdb(_args: &Args, argv: &[String]) -> io::Result<()> {
-	if !Command::new("cargo").args(["build", "-p", "orchid-std"]).status()?.success() {
+	if !Command::new("cargo").args(["build", "-p", "orchid-std", "--quiet"]).status()?.success() {
 		EXIT_OK.store(false, Ordering::Relaxed);
 		return Ok(());
 	}