diff --git a/cozo-core/src/algo/all_pairs_shortest_path.rs b/cozo-core/src/algo/all_pairs_shortest_path.rs
index 745ed960..4b2c8cfb 100644
--- a/cozo-core/src/algo/all_pairs_shortest_path.rs
+++ b/cozo-core/src/algo/all_pairs_shortest_path.rs
@@ -30,7 +30,7 @@ pub(crate) struct BetweennessCentrality;
 
 impl AlgoImpl for BetweennessCentrality {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
@@ -102,7 +102,7 @@ pub(crate) struct ClosenessCentrality;
 
 impl AlgoImpl for ClosenessCentrality {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/astar.rs b/cozo-core/src/algo/astar.rs
index f2214e3f..2dcc3730 100644
--- a/cozo-core/src/algo/astar.rs
+++ b/cozo-core/src/algo/astar.rs
@@ -27,7 +27,7 @@ pub(crate) struct ShortestPathAStar;
 
 impl AlgoImpl for ShortestPathAStar {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/bfs.rs b/cozo-core/src/algo/bfs.rs
index 252523f5..c3e3e1f4 100644
--- a/cozo-core/src/algo/bfs.rs
+++ b/cozo-core/src/algo/bfs.rs
@@ -23,7 +23,7 @@ pub(crate) struct Bfs;
 
 impl AlgoImpl for Bfs {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/constant.rs b/cozo-core/src/algo/constant.rs
index 1a6455be..9971f3a2 100644
--- a/cozo-core/src/algo/constant.rs
+++ b/cozo-core/src/algo/constant.rs
@@ -25,7 +25,7 @@ pub(crate) struct Constant;
 
 impl AlgoImpl for Constant {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         _poison: Poison,
diff --git a/cozo-core/src/algo/csv.rs b/cozo-core/src/algo/csv.rs
index 5fe5a975..5dca59ee 100644
--- a/cozo-core/src/algo/csv.rs
+++ b/cozo-core/src/algo/csv.rs
@@ -29,7 +29,7 @@ pub(crate) struct CsvReader;
 
 impl AlgoImpl for CsvReader {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         _poison: Poison,
diff --git a/cozo-core/src/algo/degree_centrality.rs b/cozo-core/src/algo/degree_centrality.rs
index a07b7268..e7dddfe1 100644
--- a/cozo-core/src/algo/degree_centrality.rs
+++ b/cozo-core/src/algo/degree_centrality.rs
@@ -23,7 +23,7 @@ pub(crate) struct DegreeCentrality;
 
 impl AlgoImpl for DegreeCentrality {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/dfs.rs b/cozo-core/src/algo/dfs.rs
index 5c2e6fea..ff161f1e 100644
--- a/cozo-core/src/algo/dfs.rs
+++ b/cozo-core/src/algo/dfs.rs
@@ -23,7 +23,7 @@ pub(crate) struct Dfs;
 
 impl AlgoImpl for Dfs {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/jlines.rs b/cozo-core/src/algo/jlines.rs
index 1c16f566..584d4317 100644
--- a/cozo-core/src/algo/jlines.rs
+++ b/cozo-core/src/algo/jlines.rs
@@ -33,7 +33,7 @@ pub(crate) struct JsonReader;
 
 impl AlgoImpl for JsonReader {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         _poison: Poison,
diff --git a/cozo-core/src/algo/kruskal.rs b/cozo-core/src/algo/kruskal.rs
index f414a11b..7de8c9cb 100644
--- a/cozo-core/src/algo/kruskal.rs
+++ b/cozo-core/src/algo/kruskal.rs
@@ -27,7 +27,7 @@ pub(crate) struct MinimumSpanningForestKruskal;
 
 impl AlgoImpl for MinimumSpanningForestKruskal {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/label_propagation.rs b/cozo-core/src/algo/label_propagation.rs
index 6ea01c6c..b385b6de 100644
--- a/cozo-core/src/algo/label_propagation.rs
+++ b/cozo-core/src/algo/label_propagation.rs
@@ -25,7 +25,7 @@ pub(crate) struct LabelPropagation;
 
 impl AlgoImpl for LabelPropagation {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/louvain.rs b/cozo-core/src/algo/louvain.rs
index e0d77ea6..53b25592 100644
--- a/cozo-core/src/algo/louvain.rs
+++ b/cozo-core/src/algo/louvain.rs
@@ -25,7 +25,7 @@ pub(crate) struct CommunityDetectionLouvain;
 
 impl AlgoImpl for CommunityDetectionLouvain {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/mod.rs b/cozo-core/src/algo/mod.rs
index 301f3f10..6fd8935e 100644
--- a/cozo-core/src/algo/mod.rs
+++ b/cozo-core/src/algo/mod.rs
@@ -392,7 +392,7 @@ pub trait AlgoImpl {
     /// The outputs are written to `out`. You should check `poison` periodically
     /// for user-initiated termination.
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &'_ mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/pagerank.rs b/cozo-core/src/algo/pagerank.rs
index af81456b..33c8cd23 100644
--- a/cozo-core/src/algo/pagerank.rs
+++ b/cozo-core/src/algo/pagerank.rs
@@ -30,7 +30,7 @@ pub(crate) struct PageRank;
 impl AlgoImpl for PageRank {
     #[allow(unused_variables)]
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/prim.rs b/cozo-core/src/algo/prim.rs
index 011139d3..81e3ea4a 100644
--- a/cozo-core/src/algo/prim.rs
+++ b/cozo-core/src/algo/prim.rs
@@ -28,7 +28,7 @@ pub(crate) struct MinimumSpanningTreePrim;
 
 impl AlgoImpl for MinimumSpanningTreePrim {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/random_walk.rs b/cozo-core/src/algo/random_walk.rs
index 706cee4d..2917c2ed 100644
--- a/cozo-core/src/algo/random_walk.rs
+++ b/cozo-core/src/algo/random_walk.rs
@@ -26,7 +26,7 @@ pub(crate) struct RandomWalk;
 
 impl AlgoImpl for RandomWalk {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/reorder_sort.rs b/cozo-core/src/algo/reorder_sort.rs
index e530753f..036a555f 100644
--- a/cozo-core/src/algo/reorder_sort.rs
+++ b/cozo-core/src/algo/reorder_sort.rs
@@ -26,7 +26,7 @@ pub(crate) struct ReorderSort;
 
 impl AlgoImpl for ReorderSort {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/shortest_path_dijkstra.rs b/cozo-core/src/algo/shortest_path_dijkstra.rs
index 97fa23f3..b04ebc30 100644
--- a/cozo-core/src/algo/shortest_path_dijkstra.rs
+++ b/cozo-core/src/algo/shortest_path_dijkstra.rs
@@ -31,7 +31,7 @@ pub(crate) struct ShortestPathDijkstra;
 
 impl AlgoImpl for ShortestPathDijkstra {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/strongly_connected_components.rs b/cozo-core/src/algo/strongly_connected_components.rs
index 1ac0f278..98b85e0a 100644
--- a/cozo-core/src/algo/strongly_connected_components.rs
+++ b/cozo-core/src/algo/strongly_connected_components.rs
@@ -39,7 +39,7 @@ impl StronglyConnectedComponent {
 #[cfg(feature = "graph-algo")]
 impl AlgoImpl for StronglyConnectedComponent {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/top_sort.rs b/cozo-core/src/algo/top_sort.rs
index a8daf0dc..9a4ae2c1 100644
--- a/cozo-core/src/algo/top_sort.rs
+++ b/cozo-core/src/algo/top_sort.rs
@@ -23,7 +23,7 @@ pub(crate) struct TopSort;
 
 impl AlgoImpl for TopSort {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/triangles.rs b/cozo-core/src/algo/triangles.rs
index c8f556bb..59584f93 100644
--- a/cozo-core/src/algo/triangles.rs
+++ b/cozo-core/src/algo/triangles.rs
@@ -25,7 +25,7 @@ pub(crate) struct ClusteringCoefficients;
 
 impl AlgoImpl for ClusteringCoefficients {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/algo/yen.rs b/cozo-core/src/algo/yen.rs
index 19e8c4e2..c6284b18 100644
--- a/cozo-core/src/algo/yen.rs
+++ b/cozo-core/src/algo/yen.rs
@@ -27,7 +27,7 @@ pub(crate) struct KShortestPathYen;
 
 impl AlgoImpl for KShortestPathYen {
     fn run(
-        &mut self,
+        &self,
         payload: AlgoPayload<'_, '_>,
         out: &mut RegularTempStore,
         poison: Poison,
diff --git a/cozo-core/src/data/program.rs b/cozo-core/src/data/program.rs
index 724daaf1..46c94a1c 100644
--- a/cozo-core/src/data/program.rs
+++ b/cozo-core/src/data/program.rs
@@ -9,6 +9,7 @@
 use std::collections::btree_map::Entry;
 use std::collections::{BTreeMap, BTreeSet};
 use std::fmt::{Debug, Display, Formatter};
+use std::rc::Rc;
 
 use miette::{ensure, Diagnostic, Result};
 use smallvec::SmallVec;
@@ -206,12 +207,12 @@ pub(crate) struct AlgoApply {
     pub(crate) head: Vec<Symbol>,
     pub(crate) arity: usize,
     pub(crate) span: SourceSpan,
-    pub(crate) algo_impl: Box<dyn AlgoImpl>,
+    pub(crate) algo_impl: Rc<Box<dyn AlgoImpl>>,
 }
 
 impl AlgoApply {
     pub(crate) fn arity(&self) -> Result<usize> {
-        self.algo_impl.arity(&self.options, &self.head, self.span)
+        self.algo_impl.as_ref().arity(&self.options, &self.head, self.span)
     }
 }
 
@@ -231,6 +232,7 @@ pub(crate) struct MagicAlgoApply {
     pub(crate) options: BTreeMap<SmartString<LazyCompact>, Expr>,
     pub(crate) span: SourceSpan,
     pub(crate) arity: usize,
+    pub(crate) algo_impl: Rc<Box<dyn AlgoImpl>>,
 }
 
 #[derive(Error, Diagnostic, Debug)]
diff --git a/cozo-core/src/parse/query.rs b/cozo-core/src/parse/query.rs
index 556a0320..dc7a1777 100644
--- a/cozo-core/src/parse/query.rs
+++ b/cozo-core/src/parse/query.rs
@@ -10,6 +10,7 @@ use std::collections::btree_map::Entry;
 use std::collections::BTreeMap;
 use std::error::Error;
 use std::fmt::{Display, Formatter};
+use std::rc::Rc;
 
 use either::{Left, Right};
 use itertools::Itertools;
@@ -217,7 +218,7 @@ pub(crate) fn parse_query(
                             head,
                             arity,
                             span,
-                            algo_impl,
+                            algo_impl: Rc::new(algo_impl),
                         },
                     },
                 );
@@ -762,7 +763,7 @@ fn parse_algo_rule(
             head,
             arity,
             span: args_list_span,
-            algo_impl,
+            algo_impl: Rc::new(algo_impl),
         },
     ))
 }
@@ -800,7 +801,7 @@ fn make_empty_const_rule(prog: &mut InputProgram, bindings: &[Symbol]) {
                 head: bindings.to_vec(),
                 arity: bindings.len(),
                 span: Default::default(),
-                algo_impl: Box::new(Constant),
+                algo_impl: Rc::new(Box::new(Constant)),
             },
         },
     );
diff --git a/cozo-core/src/query/eval.rs b/cozo-core/src/query/eval.rs
index d80dfbb4..95fd601d 100644
--- a/cozo-core/src/query/eval.rs
+++ b/cozo-core/src/query/eval.rs
@@ -12,8 +12,8 @@ use std::collections::BTreeMap;
 use itertools::Itertools;
 use log::{debug, trace};
 use miette::Result;
-use crate::algo::AlgoPayload;
 
+use crate::algo::AlgoPayload;
 use crate::data::aggr::Aggregation;
 use crate::data::program::{MagicSymbol, NoEntryError};
 use crate::data::symb::{Symbol, PROG_ENTRY};
@@ -153,7 +153,7 @@ impl<'a> SessionTx<'a> {
                             }
                         },
                         CompiledRuleSet::Algo(algo_apply) => {
-                            let mut algo_impl = algo_apply.algo.get_impl()?;
+                            let algo_impl = algo_apply.algo_impl.as_ref();
                             let mut out = RegularTempStore::default();
                             let payload = AlgoPayload {
                                 manifest: algo_apply,
diff --git a/cozo-core/src/query/magic.rs b/cozo-core/src/query/magic.rs
index 9490d788..bb1ed594 100644
--- a/cozo-core/src/query/magic.rs
+++ b/cozo-core/src/query/magic.rs
@@ -15,10 +15,10 @@ use smallvec::SmallVec;
 use smartstring::SmartString;
 
 use crate::data::program::{
-    AlgoRuleArg, MagicAlgoApply, MagicAlgoRuleArg, MagicAtom, MagicProgram, MagicRelationApplyAtom,
-    MagicInlineRule, MagicRuleApplyAtom, MagicRulesOrAlgo, MagicSymbol, NormalFormAlgoOrRules,
-    NormalFormAtom, NormalFormProgram, NormalFormInlineRule, StratifiedMagicProgram,
-    StratifiedNormalFormProgram,
+    AlgoRuleArg, MagicAlgoApply, MagicAlgoRuleArg, MagicAtom, MagicInlineRule, MagicProgram,
+    MagicRelationApplyAtom, MagicRuleApplyAtom, MagicRulesOrAlgo, MagicSymbol,
+    NormalFormAlgoOrRules, NormalFormAtom, NormalFormInlineRule, NormalFormProgram,
+    StratifiedMagicProgram, StratifiedNormalFormProgram,
 };
 use crate::data::symb::{Symbol, PROG_ENTRY};
 use crate::parse::SourceSpan;
@@ -51,9 +51,10 @@ impl StratifiedNormalFormProgram {
         let mut collected = vec![];
         for prog in self.0 {
             prog.exempt_aggr_rules_for_magic_sets(&mut exempt_rules);
+            let down_stream_rules = prog.get_downstream_rules();
             let adorned = prog.adorn(&exempt_rules, tx)?;
             collected.push(adorned.magic_rewrite());
-            exempt_rules.extend(prog.get_downstream_rules());
+            exempt_rules.extend(down_stream_rules);
         }
         Ok(StratifiedMagicProgram(collected))
     }
@@ -282,7 +283,7 @@ impl NormalFormProgram {
         }
         downstream_rules
     }
-    fn adorn(&self, upstream_rules: &BTreeSet<Symbol>, tx: &SessionTx<'_>) -> Result<MagicProgram> {
+    fn adorn(self, upstream_rules: &BTreeSet<Symbol>, tx: &SessionTx<'_>) -> Result<MagicProgram> {
         let rules_to_rewrite: BTreeSet<_> = self
             .prog
             .keys()
@@ -310,6 +311,7 @@ impl NormalFormProgram {
                             algo: MagicAlgoApply {
                                 span: algo_apply.span,
                                 algo: algo_apply.algo.clone(),
+                                algo_impl: algo_apply.algo_impl.clone(),
                                 rule_args: algo_apply
                                     .rule_args
                                     .iter()
@@ -382,7 +384,7 @@ impl NormalFormProgram {
                                     })
                                     .try_collect()?,
                                 options: algo_apply.options.clone(),
-                                arity: algo_apply.arity
+                                arity: algo_apply.arity,
                             },
                         },
                     );
diff --git a/cozo-core/src/query/stored.rs b/cozo-core/src/query/stored.rs
index 0dac084e..d4e8e360 100644
--- a/cozo-core/src/query/stored.rs
+++ b/cozo-core/src/query/stored.rs
@@ -7,6 +7,7 @@
  */
 
 use std::collections::BTreeMap;
+use std::rc::Rc;
 
 use itertools::Itertools;
 use miette::{bail, Diagnostic, Result, WrapErr};
@@ -441,7 +442,7 @@ fn make_const_rule(
                 head: bindings,
                 arity: bindings_arity,
                 span: Default::default(),
-                algo_impl: Box::new(Constant),
+                algo_impl: Rc::new(Box::new(Constant)),
             },
         },
     );