diff --git a/CHANGELOG_NEXT.md b/CHANGELOG_NEXT.md
index 9b49d478..7bb2cd4b 100644
--- a/CHANGELOG_NEXT.md
+++ b/CHANGELOG_NEXT.md
@@ -26,3 +26,5 @@
 - Release 7.0.2 with type check fix for recursive schema
 - Test GenType compatibility with d.ts
 - Clean up error tags
+- Set 8.0.x for rescript-schema in ppx deps
+- Update github ci to run on "v*.*.\*-patch"
diff --git a/packages/tests/src/benchmark/Benchmark.bs.mjs b/packages/tests/src/benchmark/Benchmark.bs.mjs
index d391e5b3..4c624412 100644
--- a/packages/tests/src/benchmark/Benchmark.bs.mjs
+++ b/packages/tests/src/benchmark/Benchmark.bs.mjs
@@ -1,6 +1,7 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 
 import * as Benchmark from "benchmark";
+import * as Core__Array from "@rescript/core/src/Core__Array.bs.mjs";
 import * as S$RescriptSchema from "rescript-schema/src/S.bs.mjs";
 
 function addWithPrepare(suite, name, fn) {
@@ -74,47 +75,129 @@ S$RescriptSchema.setGlobalConfig({
       disableNanNumberCheck: true
     });
 
+var schema = S$RescriptSchema.recursive(function (schema) {
+      return S$RescriptSchema.union([
+                  S$RescriptSchema.object(function (s) {
+                        s.tag("type", "A");
+                        return {
+                                TAG: "A",
+                                _0: s.f("nested", S$RescriptSchema.array(schema))
+                              };
+                      }),
+                  S$RescriptSchema.literal("B"),
+                  S$RescriptSchema.literal("C"),
+                  S$RescriptSchema.literal("D"),
+                  S$RescriptSchema.literal("E"),
+                  S$RescriptSchema.literal("F"),
+                  S$RescriptSchema.literal("G"),
+                  S$RescriptSchema.literal("H"),
+                  S$RescriptSchema.literal("I"),
+                  S$RescriptSchema.literal("J"),
+                  S$RescriptSchema.literal("K"),
+                  S$RescriptSchema.literal("L"),
+                  S$RescriptSchema.literal("M"),
+                  S$RescriptSchema.literal("N"),
+                  S$RescriptSchema.literal("O"),
+                  S$RescriptSchema.literal("P"),
+                  S$RescriptSchema.literal("Q"),
+                  S$RescriptSchema.literal("R"),
+                  S$RescriptSchema.literal("S"),
+                  S$RescriptSchema.literal("T"),
+                  S$RescriptSchema.literal("U"),
+                  S$RescriptSchema.literal("V"),
+                  S$RescriptSchema.literal("W"),
+                  S$RescriptSchema.literal("X"),
+                  S$RescriptSchema.literal("Y"),
+                  S$RescriptSchema.object(function (s) {
+                        s.tag("type", "Z");
+                        return {
+                                TAG: "Z",
+                                _0: s.f("nested", S$RescriptSchema.array(schema))
+                              };
+                      })
+                ]);
+    });
+
+var testData1 = {
+  TAG: "Z",
+  _0: Core__Array.make(25, {
+        TAG: "Z",
+        _0: Core__Array.make(25, {
+              TAG: "Z",
+              _0: Core__Array.make(25, "Y")
+            })
+      })
+};
+
+var testData2 = {
+  TAG: "A",
+  _0: Core__Array.make(25, {
+        TAG: "A",
+        _0: Core__Array.make(25, {
+              TAG: "A",
+              _0: Core__Array.make(25, "B")
+            })
+      })
+};
+
+function test() {
+  console.time("testData1 serialize");
+  var json = S$RescriptSchema.serializeOrRaiseWith(testData1, schema);
+  console.timeEnd("testData1 serialize");
+  console.time("testData1 parse");
+  S$RescriptSchema.parseOrRaiseWith(json, schema);
+  console.timeEnd("testData1 parse");
+  console.time("testData2 serialize");
+  var json$1 = S$RescriptSchema.serializeOrRaiseWith(testData2, schema);
+  console.timeEnd("testData2 serialize");
+  console.time("testData2 parse");
+  S$RescriptSchema.parseOrRaiseWith(json$1, schema);
+  console.timeEnd("testData2 parse");
+}
+
+test();
+
 var data = makeTestObject();
 
 console.time("makeAdvancedObjectSchema");
 
-var schema = makeAdvancedObjectSchema();
+var schema$1 = makeAdvancedObjectSchema();
 
 console.timeEnd("makeAdvancedObjectSchema");
 
 console.time("parseAnyWith: 1");
 
-S$RescriptSchema.parseAnyWith(data, schema);
+S$RescriptSchema.parseAnyWith(data, schema$1);
 
 console.timeEnd("parseAnyWith: 1");
 
 console.time("parseAnyWith: 2");
 
-S$RescriptSchema.parseAnyWith(data, schema);
+S$RescriptSchema.parseAnyWith(data, schema$1);
 
 console.timeEnd("parseAnyWith: 2");
 
 console.time("parseAnyWith: 3");
 
-S$RescriptSchema.parseAnyWith(data, schema);
+S$RescriptSchema.parseAnyWith(data, schema$1);
 
 console.timeEnd("parseAnyWith: 3");
 
 console.time("serializeWith: 1");
 
-S$RescriptSchema.serializeWith(data, schema);
+S$RescriptSchema.serializeWith(data, schema$1);
 
 console.timeEnd("serializeWith: 1");
 
 console.time("serializeWith: 2");
 
-S$RescriptSchema.serializeWith(data, schema);
+S$RescriptSchema.serializeWith(data, schema$1);
 
 console.timeEnd("serializeWith: 2");
 
 console.time("serializeWith: 3");
 
-S$RescriptSchema.serializeWith(data, schema);
+S$RescriptSchema.serializeWith(data, schema$1);
 
 console.timeEnd("serializeWith: 3");
 
diff --git a/packages/tests/src/benchmark/Benchmark.res b/packages/tests/src/benchmark/Benchmark.res
index 4a8fe6f2..1735ae7e 100644
--- a/packages/tests/src/benchmark/Benchmark.res
+++ b/packages/tests/src/benchmark/Benchmark.res
@@ -103,6 +103,116 @@ S.setGlobalConfig({
   disableNanNumberCheck: true,
 })
 
+// Reported in https://gist.github.com/cknitt/4ac6813a3f3bc907187105e01a4324ca
+module CrazyUnion = {
+  type rec test =
+    | A(array<test>)
+    | B
+    | C
+    | D
+    | E
+    | F
+    | G
+    | H
+    | I
+    | J
+    | K
+    | L
+    | M
+    | N
+    | O
+    | P
+    | Q
+    | R
+    | S
+    | T
+    | U
+    | V
+    | W
+    | X
+    | Y
+    | Z(array<test>)
+
+  let schema = S.recursive(schema =>
+    S.union([
+      S.object(s => {
+        s.tag("type", "A")
+        A(s.field("nested", S.array(schema)))
+      }),
+      S.literal(B),
+      S.literal(C),
+      S.literal(D),
+      S.literal(E),
+      S.literal(F),
+      S.literal(G),
+      S.literal(H),
+      S.literal(I),
+      S.literal(J),
+      S.literal(K),
+      S.literal(L),
+      S.literal(M),
+      S.literal(N),
+      S.literal(O),
+      S.literal(P),
+      S.literal(Q),
+      S.literal(R),
+      S.literal(S),
+      S.literal(T),
+      S.literal(U),
+      S.literal(V),
+      S.literal(W),
+      S.literal(X),
+      S.literal(Y),
+      S.object(s => {
+        s.tag("type", "Z")
+        Z(s.field("nested", S.array(schema)))
+      }),
+    ])
+  )
+
+  let testData1 = Z(Array.make(~length=25, Z(Array.make(~length=25, Z(Array.make(~length=25, Y))))))
+
+  let testData2 = A(Array.make(~length=25, A(Array.make(~length=25, A(Array.make(~length=25, B))))))
+
+  let test = () => {
+    Console.time("testData1 serialize")
+    let json = S.serializeOrRaiseWith(testData1, schema)
+    Console.timeEnd("testData1 serialize")
+
+    Console.time("testData1 parse")
+    let _ = S.parseOrRaiseWith(json, schema)
+    Console.timeEnd("testData1 parse")
+
+    Console.time("testData2 serialize")
+    let json = S.serializeOrRaiseWith(testData2, schema)
+    Console.timeEnd("testData2 serialize")
+
+    Console.time("testData2 parse")
+    let _ = S.parseOrRaiseWith(json, schema)
+    Console.timeEnd("testData2 parse")
+
+    // Js.log((schema->Obj.magic)["parseOrThrow"]["toString"]())
+  }
+}
+
+// Full
+// testData1 serialize: 5.414s
+// testData1 parse: 5.519s
+// testData2 serialize: 70.864ms
+// testData2 parse: 70.967ms
+
+// Wip
+// testData1 serialize: 5.398s
+// testData1 parse: 6.171ms
+// testData2 serialize: 69.621ms
+// testData2 parse: 0.878ms
+
+// Partial
+// testData1 serialize: 1.802ms
+// testData1 parse: 1.411ms
+// 734 Error.make
+CrazyUnion.test()
+
 let data = makeTestObject()
 Console.time("makeAdvancedObjectSchema")
 let schema = makeAdvancedObjectSchema()
diff --git a/packages/tests/src/core/Example_test.res b/packages/tests/src/core/Example_test.res
index 29ea5e5a..803e5f65 100644
--- a/packages/tests/src/core/Example_test.res
+++ b/packages/tests/src/core/Example_test.res
@@ -69,7 +69,7 @@ test("Compiled parse code snapshot", t => {
   t->U.assertCompiledCode(
     ~schema=filmSchema,
     ~op=#Parse,
-    `i=>{if(!i||i.constructor!==Object){e[11](i)}let v0=i["Id"],v1=i["Title"],v2=i["Tags"],v6=i["Rating"],v7,v8=i["Age"];if(typeof v0!=="number"||Number.isNaN(v0)){e[0](v0)}if(typeof v1!=="string"){e[1](v1)}if(v2!==void 0&&(!Array.isArray(v2))){e[2](v2)}if(v2!==void 0){for(let v3=0;v3<v2.length;++v3){let v5=v2[v3];try{if(typeof v5!=="string"){e[3](v5)}}catch(v4){if(v4&&v4.s===s){v4.path="[\\"Tags\\"]"+\'["\'+v3+\'"]\'+v4.path}throw v4}}}try{v6==="G"||e[5](v6);v7=v6}catch(e0){try{v6==="PG"||e[6](v6);v7=v6}catch(e1){try{v6==="PG13"||e[7](v6);v7=v6}catch(e2){try{v6==="R"||e[8](v6);v7=v6}catch(e3){e[9]([e0,e1,e2,e3,])}}}}if(v8!==void 0&&(typeof v8!=="number"||v8>2147483647||v8<-2147483648||v8%1!==0)){e[10](v8)}return {"id":v0,"title":v1,"tags":v2===void 0?e[4]:v2,"rating":v7,"deprecatedAgeRestriction":v8,}}`,
+    `i=>{if(!i||i.constructor!==Object){e[11](i)}let v0=i["Id"],v1=i["Title"],v2=i["Tags"],v6=i["Rating"],v7,v8=i["Age"];if(typeof v0!=="number"||Number.isNaN(v0)){e[0](v0)}if(typeof v1!=="string"){e[1](v1)}if(v2!==void 0&&(!Array.isArray(v2))){e[2](v2)}if(v2!==void 0){for(let v3=0;v3<v2.length;++v3){let v5=v2[v3];try{if(typeof v5!=="string"){e[3](v5)}}catch(v4){if(v4&&v4.s===s){v4.path="[\\"Tags\\"]"+\'["\'+v3+\'"]\'+v4.path}throw v4}}}if(!(v6==="G")){if(!(v6==="PG")){if(!(v6==="PG13")){if(!(v6==="R")){e[5](v6)}else{v7=v6}}else{v7=v6}}else{v7=v6}}else{v7=v6}if(v8!==void 0&&(typeof v8!=="number"||v8>2147483647||v8<-2147483648||v8%1!==0)){e[10](v8)}return {"id":v0,"title":v1,"tags":v2===void 0?e[4]:v2,"rating":v7,"deprecatedAgeRestriction":v8,}}`,
   )
 })
 
diff --git a/packages/tests/src/core/S_parseAnyAsyncInStepsWith_deprecatedTest.bs.mjs b/packages/tests/src/core/S_parseAnyAsyncInStepsWith_deprecatedTest.bs.mjs
new file mode 100644
index 00000000..d856702b
--- /dev/null
+++ b/packages/tests/src/core/S_parseAnyAsyncInStepsWith_deprecatedTest.bs.mjs
@@ -0,0 +1,2 @@
+// Generated by ReScript, PLEASE EDIT WITH CARE
+/* This output is empty. Its source's type definitions, externals and/or unused code got optimized away. */
diff --git a/packages/tests/src/core/S_union_test.res b/packages/tests/src/core/S_union_test.res
index 3150d808..01e161ca 100644
--- a/packages/tests/src/core/S_union_test.res
+++ b/packages/tests/src/core/S_union_test.res
@@ -25,14 +25,26 @@ test("Successfully parses polymorphic variants", t => {
   t->Assert.deepEqual(%raw(`"apple"`)->S.parseAnyWith(schema), Ok(#apple), ())
 })
 
-test("Parses when both schemas misses parser", t => {
+test("Parses when both schemas misses parser and have the same type", t => {
   let schema = S.union([
-    S.literal(#apple)->S.transform(_ => {serializer: _ => #apple}),
+    S.string->S.transform(_ => {serializer: _ => "apple"}),
     S.string->S.transform(_ => {serializer: _ => "apple"}),
   ])
 
   t->U.assertErrorResult(
     %raw(`null`)->S.parseAnyWith(schema),
+    {
+      code: InvalidType({
+        expected: schema->S.toUnknown,
+        received: %raw(`null`),
+      }),
+      operation: Parse,
+      path: S.Path.empty,
+    },
+  )
+
+  t->U.assertErrorResult(
+    %raw(`"foo"`)->S.parseAnyWith(schema),
     {
       code: InvalidUnion([
         U.error({
@@ -51,7 +63,45 @@ test("Parses when both schemas misses parser", t => {
     },
   )
 
-  t->U.assertCompiledCode(~schema, ~op=#Parse, `i=>{e[4]([e[1],e[3],]);return i}`)
+  t->U.assertCompiledCode(
+    ~schema,
+    ~op=#Parse,
+    `i=>{if(typeof i!=="string"){e[0](i)}else{e[5]([e[2],e[4],]);}return undefined}`,
+  )
+})
+
+test("Parses when both schemas misses parser and have different types", t => {
+  let schema = S.union([
+    S.literal(#apple)->S.transform(_ => {serializer: _ => #apple}),
+    S.string->S.transform(_ => {serializer: _ => "apple"}),
+  ])
+
+  t->U.assertErrorResult(
+    %raw(`null`)->S.parseAnyWith(schema),
+    {
+      code: InvalidType({
+        expected: schema->S.toUnknown,
+        received: %raw(`null`),
+      }),
+      operation: Parse,
+      path: S.Path.empty,
+    },
+  )
+
+  t->U.assertErrorResult(
+    %raw(`"abc"`)->S.parseAnyWith(schema),
+    {
+      code: InvalidOperation({description: "The S.transform parser is missing"}),
+      operation: Parse,
+      path: S.Path.empty,
+    },
+  )
+
+  t->U.assertCompiledCode(
+    ~schema,
+    ~op=#Parse,
+    `i=>{if(!(i==="apple")){if(typeof i!=="string"){e[0](i)}else{throw e[1]}}else{throw e[3]}return undefined}`,
+  )
 })
 
 test("Serializes when both schemas misses serializer", t => {
@@ -91,7 +141,7 @@ test("Parses when second struct misses parser", t => {
   t->U.assertCompiledCode(
     ~schema,
     ~op=#Parse,
-    `i=>{let v0;try{i==="apple"||e[0](i);v0=i}catch(e0){e[3]([e0,e[2],])}return v0}`,
+    `i=>{let v0;if(!(i==="apple")){if(typeof i!=="string"){e[0](i)}else{throw e[1]}}else{v0=i}return v0}`,
   )
 })
 
@@ -258,32 +308,10 @@ module Advanced = {
     t->U.assertErrorResult(
       %raw(`"Hello world!"`)->S.parseAnyWith(shapeSchema),
       {
-        code: InvalidUnion([
-          U.error({
-            code: InvalidType({
-              expected: circleSchema->S.toUnknown,
-              received: %raw(`"Hello world!"`),
-            }),
-            operation: Parse,
-            path: S.Path.empty,
-          }),
-          U.error({
-            code: InvalidType({
-              expected: squareSchema->S.toUnknown,
-              received: %raw(`"Hello world!"`),
-            }),
-            operation: Parse,
-            path: S.Path.empty,
-          }),
-          U.error({
-            code: InvalidType({
-              expected: triangleSchema->S.toUnknown,
-              received: %raw(`"Hello world!"`),
-            }),
-            operation: Parse,
-            path: S.Path.empty,
-          }),
-        ]),
+        code: InvalidType({
+          expected: shapeSchema->S.toUnknown,
+          received: %raw(`"Hello world!"`),
+        }),
         operation: Parse,
         path: S.Path.empty,
       },
@@ -377,7 +405,7 @@ module Advanced = {
     t->U.assertCompiledCode(
       ~schema=shapeSchema,
       ~op=#Parse,
-      `i=>{let v2;try{if(!i||i.constructor!==Object){e[0](i)}let v0=i["kind"],v1=i["radius"];v0==="circle"||e[1](v0);if(typeof v1!=="number"||Number.isNaN(v1)){e[2](v1)}v2={"TAG":e[3],"radius":v1,}}catch(e0){try{if(!i||i.constructor!==Object){e[4](i)}let v3=i["kind"],v4=i["x"];v3==="square"||e[5](v3);if(typeof v4!=="number"||Number.isNaN(v4)){e[6](v4)}v2={"TAG":e[7],"x":v4,}}catch(e1){try{if(!i||i.constructor!==Object){e[8](i)}let v5=i["kind"],v6=i["x"],v7=i["y"];v5==="triangle"||e[9](v5);if(typeof v6!=="number"||Number.isNaN(v6)){e[10](v6)}if(typeof v7!=="number"||Number.isNaN(v7)){e[11](v7)}v2={"TAG":e[12],"x":v6,"y":v7,}}catch(e2){e[13]([e0,e1,e2,])}}}return v2}`,
+      `i=>{let v2;if(!i||i.constructor!==Object){e[0](i)}else{try{if(!i||i.constructor!==Object){e[1](i)}let v0=i["kind"],v1=i["radius"];v0==="circle"||e[2](v0);if(typeof v1!=="number"||Number.isNaN(v1)){e[3](v1)}v2={"TAG":e[4],"radius":v1,}}catch(e0){try{if(!i||i.constructor!==Object){e[5](i)}let v3=i["kind"],v4=i["x"];v3==="square"||e[6](v3);if(typeof v4!=="number"||Number.isNaN(v4)){e[7](v4)}v2={"TAG":e[8],"x":v4,}}catch(e1){try{if(!i||i.constructor!==Object){e[9](i)}let v5=i["kind"],v6=i["x"],v7=i["y"];v5==="triangle"||e[10](v5);if(typeof v6!=="number"||Number.isNaN(v6)){e[11](v6)}if(typeof v7!=="number"||Number.isNaN(v7)){e[12](v7)}v2={"TAG":e[13],"x":v6,"y":v7,}}catch(e2){e[14]([e0,e1,e2,])}}}}return v2}`,
     )
   })
 
@@ -413,7 +441,7 @@ test("Compiled parse code snapshot", t => {
   t->U.assertCompiledCode(
     ~schema,
     ~op=#Parse,
-    `i=>{let v0;try{i===0||e[0](i);v0=i}catch(e0){try{i===1||e[1](i);v0=i}catch(e1){e[2]([e0,e1,])}}return v0}`,
+    `i=>{let v0;if(!(i===0)){if(!(i===1)){e[0](i)}else{v0=i}}else{v0=i}return v0}`,
   )
 })
 
@@ -500,3 +528,86 @@ module CknittelBugReport = {
     )
   })
 }
+
+// Reported in https://gist.github.com/cknitt/4ac6813a3f3bc907187105e01a4324ca
+module CrazyUnion = {
+  type rec test =
+    | A(array<test>)
+    | B
+    | C
+    | D
+    | E
+    | F
+    | G
+    | H
+    | I
+    | J
+    | K
+    | L
+    | M
+    | N
+    | O
+    | P
+    | Q
+    | R
+    | S
+    | T
+    | U
+    | V
+    | W
+    | X
+    | Y
+    | Z(array<test>)
+
+  let schema = S.recursive(schema =>
+    S.union([
+      S.object(s => {
+        s.tag("type", "A")
+        A(s.field("nested", S.array(schema)))
+      }),
+      S.literal(B),
+      S.literal(C),
+      S.literal(D),
+      S.literal(E),
+      S.literal(F),
+      S.literal(G),
+      S.literal(H),
+      S.literal(I),
+      S.literal(J),
+      S.literal(K),
+      S.literal(L),
+      S.literal(M),
+      S.literal(N),
+      S.literal(O),
+      S.literal(P),
+      S.literal(Q),
+      S.literal(R),
+      S.literal(S),
+      S.literal(T),
+      S.literal(U),
+      S.literal(V),
+      S.literal(W),
+      S.literal(X),
+      S.literal(Y),
+      S.object(s => {
+        s.tag("type", "Z")
+        Z(s.field("nested", S.array(schema)))
+      }),
+    ])
+  )
+
+  // test("Compiled code snapshot of crazy union", t => {
+  //   S.setGlobalConfig({})
+  //   t->U.assertCompiledCode(
+  //     ~schema,
+  //     ~op=#Parse,
+  //     `i=>{let r0=i=>{let v6;try{if(!i||i.constructor!==Object){e[0](i)}let v0=i["type"],v1=i["nested"],v5=[];v0==="A"||e[1](v0);if(!Array.isArray(v1)){e[2](v1)}for(let v2=0;v2<v1.length;++v2){let v4;try{v4=r0(v1[v2])}catch(v3){if(v3&&v3.s===s){v3.path="[\\"nested\\"]"+\'["\'+v2+\'"]\'+v3.path}throw v3}v5.push(v4)}v6={"TAG":e[3],"_0":v5,}}catch(e0){try{i==="B"||e[4](i);v6=i}catch(e1){try{i==="C"||e[5](i);v6=i}catch(e2){try{i==="D"||e[6](i);v6=i}catch(e3){try{i==="E"||e[7](i);v6=i}catch(e4){try{i==="F"||e[8](i);v6=i}catch(e5){try{i==="G"||e[9](i);v6=i}catch(e6){try{i==="H"||e[10](i);v6=i}catch(e7){try{i==="I"||e[11](i);v6=i}catch(e8){try{i==="J"||e[12](i);v6=i}catch(e9){try{i==="K"||e[13](i);v6=i}catch(e10){try{i==="L"||e[14](i);v6=i}catch(e11){try{i==="M"||e[15](i);v6=i}catch(e12){try{i==="N"||e[16](i);v6=i}catch(e13){try{i==="O"||e[17](i);v6=i}catch(e14){try{i==="P"||e[18](i);v6=i}catch(e15){try{i==="Q"||e[19](i);v6=i}catch(e16){try{i==="R"||e[20](i);v6=i}catch(e17){try{i==="S"||e[21](i);v6=i}catch(e18){try{i==="T"||e[22](i);v6=i}catch(e19){try{i==="U"||e[23](i);v6=i}catch(e20){try{i==="V"||e[24](i);v6=i}catch(e21){try{i==="W"||e[25](i);v6=i}catch(e22){try{i==="X"||e[26](i);v6=i}catch(e23){try{i==="Y"||e[27](i);v6=i}catch(e24){try{if(!i||i.constructor!==Object){e[28](i)}let v7=i["type"],v8=i["nested"],v12=[];v7==="Z"||e[29](v7);if(!Array.isArray(v8)){e[30](v8)}for(let v9=0;v9<v8.length;++v9){let v11;try{v11=r0(v8[v9])}catch(v10){if(v10&&v10.s===s){v10.path="[\\"nested\\"]"+\'["\'+v9+\'"]\'+v10.path}throw v10}v12.push(v11)}v6={"TAG":e[31],"_0":v12,}}catch(e25){e[32]([e0,e1,e2,e3,e4,e5,e6,e7,e8,e9,e10,e11,e12,e13,e14,e15,e16,e17,e18,e19,e20,e21,e22,e23,e24,e25,])}}}}}}}}}}}}}}}}}}}}}}}}}}return v6};return r0(i)}`,
+  //   )
+  //   S.setGlobalConfig({})
+  //   t->U.assertCompiledCode(
+  //     ~schema,
+  //     ~op=#Serialize,
+  //     `i=>{let r0=i=>{let v5,v6,v12;try{let v0=i["_0"],v4=[];if(i["TAG"]!==e[0]){e[1](i["TAG"])}for(let v1=0;v1<v0.length;++v1){let v3;try{v3=r0(v0[v1])}catch(v2){if(v2&&v2.s===s){v2.path="[\\"_0\\"]"+\'["\'+v1+\'"]\'+v2.path}throw v2}v4.push(v3)}v5={"type":e[2],"nested":v4,};if(!v5||v5.constructor!==Object){e[3](v5)}v6=v5}catch(e0){try{i==="B"||e[4](i);v6=i}catch(e1){try{i==="C"||e[5](i);v6=i}catch(e2){try{i==="D"||e[6](i);v6=i}catch(e3){try{i==="E"||e[7](i);v6=i}catch(e4){try{i==="F"||e[8](i);v6=i}catch(e5){try{i==="G"||e[9](i);v6=i}catch(e6){try{i==="H"||e[10](i);v6=i}catch(e7){try{i==="I"||e[11](i);v6=i}catch(e8){try{i==="J"||e[12](i);v6=i}catch(e9){try{i==="K"||e[13](i);v6=i}catch(e10){try{i==="L"||e[14](i);v6=i}catch(e11){try{i==="M"||e[15](i);v6=i}catch(e12){try{i==="N"||e[16](i);v6=i}catch(e13){try{i==="O"||e[17](i);v6=i}catch(e14){try{i==="P"||e[18](i);v6=i}catch(e15){try{i==="Q"||e[19](i);v6=i}catch(e16){try{i==="R"||e[20](i);v6=i}catch(e17){try{i==="S"||e[21](i);v6=i}catch(e18){try{i==="T"||e[22](i);v6=i}catch(e19){try{i==="U"||e[23](i);v6=i}catch(e20){try{i==="V"||e[24](i);v6=i}catch(e21){try{i==="W"||e[25](i);v6=i}catch(e22){try{i==="X"||e[26](i);v6=i}catch(e23){try{i==="Y"||e[27](i);v6=i}catch(e24){try{let v7=i["_0"],v11=[];if(i["TAG"]!==e[28]){e[29](i["TAG"])}for(let v8=0;v8<v7.length;++v8){let v10;try{v10=r0(v7[v8])}catch(v9){if(v9&&v9.s===s){v9.path="[\\"_0\\"]"+\'["\'+v8+\'"]\'+v9.path}throw v9}v11.push(v10)}v12={"type":e[30],"nested":v11,};if(!v12||v12.constructor!==Object){e[31](v12)}v6=v12}catch(e25){e[32]([e0,e1,e2,e3,e4,e5,e6,e7,e8,e9,e10,e11,e12,e13,e14,e15,e16,e17,e18,e19,e20,e21,e22,e23,e24,e25,])}}}}}}}}}}}}}}}}}}}}}}}}}}return v6};return r0(i)}`,
+  //   )
+  // })
+}
diff --git a/src/S_Core.bs.mjs b/src/S_Core.bs.mjs
index 1896566f..fe0e0940 100644
--- a/src/S_Core.bs.mjs
+++ b/src/S_Core.bs.mjs
@@ -66,8 +66,11 @@ function toJsResult(result) {
   }
 }
 
-class RescriptSchemaError extends Error {
+// let index = 0;
+    class RescriptSchemaError extends Error {
       constructor(code, operation, path) {
+        // console.log(index)
+        // index = index + 1;
         super();
         this.operation = operation;
         this.code = code;
@@ -1924,6 +1927,48 @@ function factory$7(definer) {
               }));
 }
 
+function genericParse(b, schemas, input, output, path) {
+  var codeEndRef = "";
+  var errorCodeRef = "";
+  var isAsync = false;
+  for(var idx = 0 ,idx_finish = schemas.length; idx < idx_finish; ++idx){
+    var prevCode = b.c;
+    try {
+      var schema = schemas[idx];
+      var errorVar = "e" + idx;
+      b.c = b.c + "try{";
+      var itemOutput = parseWithTypeCheck(b, schema, input, "");
+      if (itemOutput.a) {
+        isAsync = true;
+      }
+      b.c = b.c + (set(b, output, itemOutput) + "}catch(" + errorVar + "){");
+      codeEndRef = codeEndRef + "}";
+      errorCodeRef = errorCodeRef + errorVar + ",";
+    }
+    catch (raw_exn){
+      var exn = Caml_js_exceptions.internalToOCamlException(raw_exn);
+      var value = getOrRethrow(exn);
+      errorCodeRef = errorCodeRef + ("e[" + (b.g.e.push(value) - 1) + "]") + ",";
+      b.c = prevCode;
+    }
+  }
+  if (isAsync) {
+    invalidOperation(b, path, "S.union doesn't support async items. Please create an issue to rescript-schema if you nead the feature");
+  }
+  b.c = b.c + failWithArg(b, path, (function (internalErrors) {
+          return {
+                  TAG: "InvalidUnion",
+                  _0: internalErrors
+                };
+        }), "[" + errorCodeRef + "]") + codeEndRef;
+  var isAllSchemasBuilderFailed = codeEndRef === "";
+  if (isAllSchemasBuilderFailed) {
+    b.c = b.c + ";";
+    return ;
+  }
+  
+}
+
 function factory$8(schemas) {
   var len = schemas.length;
   if (len === 1) {
@@ -1939,47 +1984,68 @@ function factory$8(schemas) {
                 _0: schemas
               }, empty, (function (b, input, selfSchema, path) {
                   var schemas = selfSchema.r._0;
-                  var output = allocateVal(b);
-                  var codeEndRef = "";
-                  var errorCodeRef = "";
-                  var isAsync = false;
+                  var inputVar = $$var(b, input);
+                  var groupsByTypeFilter = {};
+                  var typeFilters = [];
                   for(var idx = 0 ,idx_finish = schemas.length; idx < idx_finish; ++idx){
-                    var prevCode = b.c;
-                    try {
-                      var schema = schemas[idx];
-                      var errorVar = "e" + idx;
-                      b.c = b.c + "try{";
-                      var itemOutput = parseWithTypeCheck(b, schema, input, "");
-                      if (itemOutput.a) {
-                        isAsync = true;
+                    var schema = schemas[idx];
+                    var typeFilter = schema.f;
+                    var typeFilterCode;
+                    if (typeFilter !== undefined) {
+                      typeFilterCode = typeFilter(inputVar);
+                    } else {
+                      var literal = schema.r;
+                      if (typeof literal !== "object" || literal.TAG !== "Literal") {
+                        typeFilterCode = "false";
+                      } else {
+                        var literal$1 = literal._0;
+                        typeFilterCode = "!(" + literal$1.b(b, inputVar, literal$1) + ")";
                       }
-                      b.c = b.c + (set(b, output, itemOutput) + "}catch(" + errorVar + "){");
-                      codeEndRef = codeEndRef + "}";
-                      errorCodeRef = errorCodeRef + errorVar + ",";
                     }
-                    catch (raw_exn){
-                      var exn = Caml_js_exceptions.internalToOCamlException(raw_exn);
-                      var value = getOrRethrow(exn);
-                      errorCodeRef = errorCodeRef + ("e[" + (b.g.e.push(value) - 1) + "]") + ",";
-                      b.c = prevCode;
+                    var schemas$1 = Js_dict.get(groupsByTypeFilter, typeFilterCode);
+                    if (schemas$1 !== undefined) {
+                      schemas$1.push(schema);
+                    } else {
+                      typeFilters.push(typeFilterCode);
+                      groupsByTypeFilter[typeFilterCode] = [schema];
                     }
                   }
-                  if (isAsync) {
-                    invalidOperation(b, path, "S.union doesn't support async items. Please create an issue to rescript-schema if you nead the feature");
-                  }
-                  b.c = b.c + failWithArg(b, path, (function (internalErrors) {
-                          return {
-                                  TAG: "InvalidUnion",
-                                  _0: internalErrors
-                                };
-                        }), "[" + errorCodeRef + "]") + codeEndRef;
-                  var isAllSchemasBuilderFailed = codeEndRef === "";
-                  if (isAllSchemasBuilderFailed) {
-                    b.c = b.c + ";";
-                    return input;
-                  } else {
-                    return output;
-                  }
+                  var output = allocateVal(b);
+                  var loopTypeFilters = function (idx) {
+                    var isLastItem = idx === (typeFilters.length - 1 | 0);
+                    var typeFilterCode = typeFilters[idx];
+                    var schemas = groupsByTypeFilter[typeFilterCode];
+                    b.c = b.c + ("if(" + typeFilterCode + "){");
+                    if (isLastItem) {
+                      b.c = b.c + failWithArg(b, path, (function (received) {
+                              return {
+                                      TAG: "InvalidType",
+                                      expected: selfSchema,
+                                      received: received
+                                    };
+                            }), inputVar);
+                    } else {
+                      loopTypeFilters(idx + 1 | 0);
+                    }
+                    b.c = b.c + "}else{";
+                    if (schemas.length !== 1) {
+                      genericParse(b, schemas, input, output, path);
+                    } else {
+                      var schema = schemas[0];
+                      var prevCode = b.c;
+                      try {
+                        b.c = b.c + set(b, output, schema.p(b, input, schema, path));
+                      }
+                      catch (raw_exn){
+                        var exn = Caml_js_exceptions.internalToOCamlException(raw_exn);
+                        var value = getOrRethrow(exn);
+                        b.c = prevCode + "throw " + ("e[" + (b.g.e.push(value) - 1) + "]");
+                      }
+                    }
+                    b.c = b.c + "}";
+                  };
+                  loopTypeFilters(0);
+                  return output;
                 }), (function (b, input, selfSchema, path) {
                   var schemas = selfSchema.r._0;
                   var output = allocateVal(b);
diff --git a/src/S_Core.res b/src/S_Core.res
index 7374693b..d32e1ab5 100644
--- a/src/S_Core.res
+++ b/src/S_Core.res
@@ -379,8 +379,11 @@ let toJsResult = (result: result<'value, error>): jsResult<'value> => {
 
 module InternalError = {
   %%raw(`
+    // let index = 0;
     class RescriptSchemaError extends Error {
       constructor(code, operation, path) {
+        // console.log(index)
+        // index = index + 1;
         super();
         this.operation = operation;
         this.code = code;
@@ -2838,6 +2841,58 @@ module Tuple = {
 }
 
 module Union = {
+  let genericParse = (b, ~schemas, ~input, ~output, ~path) => {
+    let codeEndRef = ref("")
+    let errorCodeRef = ref("")
+    let isAsync = ref(false)
+
+    // TODO: Add support for async
+    for idx in 0 to schemas->Js.Array2.length - 1 {
+      let prevCode = b.code
+      try {
+        let schema = schemas->Js.Array2.unsafe_get(idx)
+        let errorVar = `e` ++ idx->Stdlib.Int.unsafeToString
+        b.code = b.code ++ `try{`
+        let itemOutput = b->B.parseWithTypeCheck(~schema, ~input, ~path=Path.empty)
+        if itemOutput.isAsync {
+          isAsync := true
+        }
+
+        b.code = b.code ++ `${b->B.Val.set(output, itemOutput)}}catch(${errorVar}){`
+        codeEndRef := codeEndRef.contents ++ "}"
+
+        errorCodeRef := errorCodeRef.contents ++ errorVar ++ ","
+      } catch {
+      | exn =>
+        errorCodeRef := errorCodeRef.contents ++ b->B.embed(exn->InternalError.getOrRethrow) ++ ","
+        b.code = prevCode
+      }
+    }
+
+    if isAsync.contents {
+      b->B.invalidOperation(
+        ~path,
+        ~description="S.union doesn't support async items. Please create an issue to rescript-schema if you nead the feature",
+      )
+    }
+
+    b.code =
+      b.code ++
+      b->B.failWithArg(
+        ~path,
+        internalErrors => {
+          InvalidUnion(internalErrors)
+        },
+        `[${errorCodeRef.contents}]`,
+      ) ++
+      codeEndRef.contents
+
+    let isAllSchemasBuilderFailed = codeEndRef.contents === ""
+    if isAllSchemasBuilderFailed {
+      b.code = b.code ++ ";"
+    }
+  }
+
   let factory = schemas => {
     let schemas: array<t<unknown>> = schemas->Obj.magic
 
@@ -2851,61 +2906,68 @@ module Union = {
         ~rawTagged=Union(schemas),
         ~parseOperationBuilder=Builder.make((b, ~input, ~selfSchema, ~path) => {
           let schemas = selfSchema->classify->unsafeGetVariantPayload
+          let inputVar = b->B.Val.var(input)
 
-          let output = b->B.allocateVal
-          let codeEndRef = ref("")
-          let errorCodeRef = ref("")
-          let isAsync = ref(false)
-
-          // TODO: Add support for async
+          let groupsByTypeFilter = Js.Dict.empty()
+          let typeFilters = []
           for idx in 0 to schemas->Js.Array2.length - 1 {
-            let prevCode = b.code
-            try {
-              let schema = schemas->Js.Array2.unsafe_get(idx)
-              let errorVar = `e` ++ idx->Stdlib.Int.unsafeToString
-              b.code = b.code ++ `try{`
-              let itemOutput = b->B.parseWithTypeCheck(~schema, ~input, ~path=Path.empty)
-              if itemOutput.isAsync {
-                isAsync := true
+            let schema = schemas->Js.Array2.unsafe_get(idx)
+            let typeFilterCode = switch schema.maybeTypeFilter {
+            | Some(typeFilter) => typeFilter(~inputVar)
+            | None =>
+              switch schema.rawTagged {
+              | Literal(literal) =>
+                `!(${b->(literal->Literal.toInternal).checkBuilder(~inputVar, ~literal)})`
+              | _ => "false"
+              }
+            }
+            switch groupsByTypeFilter->Js.Dict.get(typeFilterCode) {
+            | Some(schemas) => schemas->Js.Array2.push(schema)->ignore
+            | None => {
+                typeFilters->Js.Array2.push(typeFilterCode)->ignore
+                groupsByTypeFilter->Js.Dict.set(typeFilterCode, [schema])
               }
-
-              b.code = b.code ++ `${b->B.Val.set(output, itemOutput)}}catch(${errorVar}){`
-              codeEndRef := codeEndRef.contents ++ "}"
-
-              errorCodeRef := errorCodeRef.contents ++ errorVar ++ ","
-            } catch {
-            | exn =>
-              errorCodeRef :=
-                errorCodeRef.contents ++ b->B.embed(exn->InternalError.getOrRethrow) ++ ","
-              b.code = prevCode
             }
           }
 
-          if isAsync.contents {
-            b->B.invalidOperation(
-              ~path,
-              ~description="S.union doesn't support async items. Please create an issue to rescript-schema if you nead the feature",
-            )
-          }
+          let output = b->B.allocateVal
 
-          b.code =
-            b.code ++
-            b->B.failWithArg(
-              ~path,
-              internalErrors => {
-                InvalidUnion(internalErrors)
-              },
-              `[${errorCodeRef.contents}]`,
-            ) ++
-            codeEndRef.contents
+          let rec loopTypeFilters = idx => {
+            let isLastItem = idx === typeFilters->Js.Array2.length - 1
+            let typeFilterCode = typeFilters->Js.Array2.unsafe_get(idx)
+            let schemas = groupsByTypeFilter->Js.Dict.unsafeGet(typeFilterCode)
 
-          let isAllSchemasBuilderFailed = codeEndRef.contents === ""
-          if isAllSchemasBuilderFailed {
-            b.code = b.code ++ ";"
-            input
-          } else {
-            output
+            b.code = b.code ++ `if(${typeFilterCode}){`
+            if isLastItem {
+              b.code =
+                b.code ++
+                b->B.failWithArg(
+                  ~path,
+                  received => InvalidType({
+                    expected: selfSchema,
+                    received,
+                  }),
+                  inputVar,
+                )
+            } else {
+              loopTypeFilters(idx + 1)
+            }
+            b.code = b.code ++ `}else{`
+            switch schemas {
+            | [schema] =>
+              let prevCode = b.code
+              try {
+                b.code = b.code ++ b->B.Val.set(output, b->B.parse(~schema, ~input, ~path))
+              } catch {
+              | exn => b.code = prevCode ++ "throw " ++ b->B.embed(exn->InternalError.getOrRethrow)
+              }
+            | _ => genericParse(b, ~schemas, ~input, ~output, ~path)
+            }
+            b.code = b.code ++ `}`
           }
+          loopTypeFilters(0)
+
+          output
         }),
         ~serializeOperationBuilder=Builder.make((b, ~input, ~selfSchema, ~path) => {
           let schemas = selfSchema->classify->unsafeGetVariantPayload
diff --git a/test.js b/test.js
index 952a7610..1a2f24ef 100644
--- a/test.js
+++ b/test.js
@@ -1,14 +1,226 @@
 (i) => {
-  return e[0](i).then((v0) => {
-    return e[1](v0)
-      .then((v1) => {
-        if (typeof v1 !== "string") {
-          e[2](v1);
+  let r0 = (i) => {
+    let v5, v6, v12;
+    try {
+      let v0 = i["_0"],
+        v4 = [];
+      if (i["TAG"] !== e[0]) {
+        e[1](i["TAG"]);
+      }
+      for (let v1 = 0; v1 < v0.length; ++v1) {
+        let v3;
+        try {
+          v3 = r0(v0[v1]);
+        } catch (v2) {
+          if (v2 && v2.s === s) {
+            v2.path = '["_0"]' + '["' + v1 + '"]' + v2.path;
+          }
+          throw v2;
         }
-        return v1;
-      })
-      .then((v2) => {
-        return e[3](v2);
-      });
-  });
+        v4.push(v3);
+      }
+      v5 = { type: e[2], nested: v4 };
+      if (!v5 || v5.constructor !== Object) {
+        e[3](v5);
+      }
+      v6 = v5;
+    } catch (e0) {
+      try {
+        i === "B" || e[4](i);
+        v6 = i;
+      } catch (e1) {
+        try {
+          i === "C" || e[5](i);
+          v6 = i;
+        } catch (e2) {
+          try {
+            i === "D" || e[6](i);
+            v6 = i;
+          } catch (e3) {
+            try {
+              i === "E" || e[7](i);
+              v6 = i;
+            } catch (e4) {
+              try {
+                i === "F" || e[8](i);
+                v6 = i;
+              } catch (e5) {
+                try {
+                  i === "G" || e[9](i);
+                  v6 = i;
+                } catch (e6) {
+                  try {
+                    i === "H" || e[10](i);
+                    v6 = i;
+                  } catch (e7) {
+                    try {
+                      i === "I" || e[11](i);
+                      v6 = i;
+                    } catch (e8) {
+                      try {
+                        i === "J" || e[12](i);
+                        v6 = i;
+                      } catch (e9) {
+                        try {
+                          i === "K" || e[13](i);
+                          v6 = i;
+                        } catch (e10) {
+                          try {
+                            i === "L" || e[14](i);
+                            v6 = i;
+                          } catch (e11) {
+                            try {
+                              i === "M" || e[15](i);
+                              v6 = i;
+                            } catch (e12) {
+                              try {
+                                i === "N" || e[16](i);
+                                v6 = i;
+                              } catch (e13) {
+                                try {
+                                  i === "O" || e[17](i);
+                                  v6 = i;
+                                } catch (e14) {
+                                  try {
+                                    i === "P" || e[18](i);
+                                    v6 = i;
+                                  } catch (e15) {
+                                    try {
+                                      i === "Q" || e[19](i);
+                                      v6 = i;
+                                    } catch (e16) {
+                                      try {
+                                        i === "R" || e[20](i);
+                                        v6 = i;
+                                      } catch (e17) {
+                                        try {
+                                          i === "S" || e[21](i);
+                                          v6 = i;
+                                        } catch (e18) {
+                                          try {
+                                            i === "T" || e[22](i);
+                                            v6 = i;
+                                          } catch (e19) {
+                                            try {
+                                              i === "U" || e[23](i);
+                                              v6 = i;
+                                            } catch (e20) {
+                                              try {
+                                                i === "V" || e[24](i);
+                                                v6 = i;
+                                              } catch (e21) {
+                                                try {
+                                                  i === "W" || e[25](i);
+                                                  v6 = i;
+                                                } catch (e22) {
+                                                  try {
+                                                    i === "X" || e[26](i);
+                                                    v6 = i;
+                                                  } catch (e23) {
+                                                    try {
+                                                      i === "Y" || e[27](i);
+                                                      v6 = i;
+                                                    } catch (e24) {
+                                                      try {
+                                                        let v7 = i["_0"],
+                                                          v11 = [];
+                                                        if (
+                                                          i["TAG"] !== e[28]
+                                                        ) {
+                                                          e[29](i["TAG"]);
+                                                        }
+                                                        for (
+                                                          let v8 = 0;
+                                                          v8 < v7.length;
+                                                          ++v8
+                                                        ) {
+                                                          let v10;
+                                                          try {
+                                                            v10 = r0(v7[v8]);
+                                                          } catch (v9) {
+                                                            if (
+                                                              v9 &&
+                                                              v9.s === s
+                                                            ) {
+                                                              v9.path =
+                                                                '["_0"]' +
+                                                                '["' +
+                                                                v8 +
+                                                                '"]' +
+                                                                v9.path;
+                                                            }
+                                                            throw v9;
+                                                          }
+                                                          v11.push(v10);
+                                                        }
+                                                        v12 = {
+                                                          type: e[30],
+                                                          nested: v11,
+                                                        };
+                                                        if (
+                                                          !v12 ||
+                                                          v12.constructor !==
+                                                            Object
+                                                        ) {
+                                                          e[31](v12);
+                                                        }
+                                                        v6 = v12;
+                                                      } catch (e25) {
+                                                        e[32]([
+                                                          e0,
+                                                          e1,
+                                                          e2,
+                                                          e3,
+                                                          e4,
+                                                          e5,
+                                                          e6,
+                                                          e7,
+                                                          e8,
+                                                          e9,
+                                                          e10,
+                                                          e11,
+                                                          e12,
+                                                          e13,
+                                                          e14,
+                                                          e15,
+                                                          e16,
+                                                          e17,
+                                                          e18,
+                                                          e19,
+                                                          e20,
+                                                          e21,
+                                                          e22,
+                                                          e23,
+                                                          e24,
+                                                          e25,
+                                                        ]);
+                                                      }
+                                                    }
+                                                  }
+                                                }
+                                              }
+                                            }
+                                          }
+                                        }
+                                      }
+                                    }
+                                  }
+                                }
+                              }
+                            }
+                          }
+                        }
+                      }
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    return v6;
+  };
+  return r0(i);
 };