diff --git a/compiler/bin-wasm_of_ocaml/compile.ml b/compiler/bin-wasm_of_ocaml/compile.ml
index cd91ca450a..85f9a33255 100644
--- a/compiler/bin-wasm_of_ocaml/compile.ml
+++ b/compiler/bin-wasm_of_ocaml/compile.ml
@@ -81,6 +81,42 @@ let with_runtime_files ~runtime_wasm_files f =
   in
   Wat_preprocess.with_preprocessed_files ~variables:[] ~inputs f
 
+let build_runtime ~runtime_file =
+  (* Keep this variables in sync with gen/gen.ml *)
+  let variables =
+    [ ( "effects"
+      , Wat_preprocess.String
+          (match Config.effects () with
+          | `Jspi -> "jspi"
+          | `Cps -> "cps"
+          | `Disabled | `Double_translation -> assert false) )
+    ]
+  in
+  match
+    List.find_opt Runtime_files.precompiled_runtimes ~f:(fun (flags, _) ->
+        assert (
+          List.length flags = List.length variables
+          && List.for_all2 ~f:(fun (k, _) (k', _) -> String.equal k k') flags variables);
+        Poly.equal flags variables)
+  with
+  | Some (_, contents) -> Fs.write_file ~name:runtime_file ~contents
+  | None ->
+      let inputs =
+        List.map
+          ~f:(fun (module_name, contents) ->
+            { Wat_preprocess.module_name
+            ; file = module_name ^ ".wat"
+            ; source = Contents contents
+            })
+          Runtime_files.wat_files
+      in
+      Runtime.build
+        ~link_options:[ "-g" ]
+        ~opt_options:[ "-g"; "-O2" ]
+        ~variables
+        ~inputs
+        ~output_file:runtime_file
+
 let link_and_optimize
     ~profile
     ~sourcemap_root
@@ -99,7 +135,7 @@ let link_and_optimize
   let enable_source_maps = Option.is_some opt_sourcemap_file in
   Fs.with_intermediate_file (Filename.temp_file "runtime" ".wasm")
   @@ fun runtime_file ->
-  Fs.write_file ~name:runtime_file ~contents:Runtime_files.wasm_runtime;
+  build_runtime ~runtime_file;
   Fs.with_intermediate_file (Filename.temp_file "wasm-merged" ".wasm")
   @@ fun temp_file ->
   opt_with
@@ -145,7 +181,7 @@ let link_and_optimize
 
 let link_runtime ~profile runtime_wasm_files output_file =
   if List.is_empty runtime_wasm_files
-  then Fs.write_file ~name:output_file ~contents:Runtime_files.wasm_runtime
+  then build_runtime ~runtime_file:output_file
   else
     Fs.with_intermediate_file (Filename.temp_file "extra_runtime" ".wasm")
     @@ fun extra_runtime ->
@@ -167,7 +203,7 @@ let link_runtime ~profile runtime_wasm_files output_file =
       ();
     Fs.with_intermediate_file (Filename.temp_file "runtime" ".wasm")
     @@ fun runtime_file ->
-    Fs.write_file ~name:runtime_file ~contents:Runtime_files.wasm_runtime;
+    build_runtime ~runtime_file;
     Binaryen.link
       ~opt_output_sourcemap:None
       ~inputs:
diff --git a/compiler/bin-wasm_of_ocaml/dune b/compiler/bin-wasm_of_ocaml/dune
index 48619f0fe4..1870a60f7c 100644
--- a/compiler/bin-wasm_of_ocaml/dune
+++ b/compiler/bin-wasm_of_ocaml/dune
@@ -25,9 +25,10 @@
  (target runtime_files.ml)
  (deps
   gen/gen.exe
-  ../../runtime/wasm/runtime.wasm
   ../../runtime/wasm/runtime.js
-  ../../runtime/wasm/deps.json)
+  ../../runtime/wasm/deps.json
+  (glob_files ../../runtime/wasm/*.wat)
+  (glob_files ../../runtime/wasm/runtime-*.wasm))
  (action
   (with-stdout-to
    %{target}
diff --git a/compiler/bin-wasm_of_ocaml/gen/gen.ml b/compiler/bin-wasm_of_ocaml/gen/gen.ml
index b7a20c4e3e..6cc0146bc6 100644
--- a/compiler/bin-wasm_of_ocaml/gen/gen.ml
+++ b/compiler/bin-wasm_of_ocaml/gen/gen.ml
@@ -1,13 +1,77 @@
 let read_file ic = really_input_string ic (in_channel_length ic)
 
+(* Keep the two variables below in sync with function build_runtime in
+   ../compile.ml *)
+
+let default_flags = []
+
+let interesting_runtimes = [ [ "effects", `S "jspi" ]; [ "effects", `S "cps" ] ]
+
+let name_runtime standard l =
+  let flags =
+    List.filter_map
+      (fun (k, v) ->
+        match v with
+        | `S s -> Some s
+        | `B b -> if b then Some k else None)
+      l
+  in
+  String.concat "-" ("runtime" :: (if standard then [ "standard" ] else flags)) ^ ".wasm"
+
+let print_flags f flags =
+  Format.fprintf
+    f
+    "@[<2>[ %a ]@]"
+    (Format.pp_print_list
+       ~pp_sep:(fun f () -> Format.fprintf f ";@ ")
+       (fun f (k, v) ->
+         Format.fprintf
+           f
+           "@[\"%s\",@ %a@]"
+           k
+           (fun f v ->
+             match v with
+             | `S s -> Format.fprintf f "Wat_preprocess.String \"%s\"" s
+             | `B b ->
+                 Format.fprintf f "Wat_preprocess.Bool %s" (if b then "true" else "false"))
+           v))
+    flags
+
 let () =
   let () = set_binary_mode_out stdout true in
+  Format.printf "open Wasm_of_ocaml_compiler@.";
   Format.printf
-    "let wasm_runtime = \"%s\"@."
+    "let js_runtime = \"%s\"@."
     (String.escaped (read_file (open_in_bin Sys.argv.(1))));
   Format.printf
-    "let js_runtime = \"%s\"@."
+    "let dependencies = \"%s\"@."
     (String.escaped (read_file (open_in_bin Sys.argv.(2))));
+  let wat_files, runtimes =
+    List.partition
+      (fun f -> Filename.check_suffix f ".wat")
+      (Array.to_list (Array.sub Sys.argv 3 (Array.length Sys.argv - 3)))
+  in
   Format.printf
-    "let dependencies = \"%s\"@."
-    (String.escaped (read_file (open_in_bin Sys.argv.(3))))
+    "let wat_files = [%a]@."
+    (Format.pp_print_list (fun f file ->
+         Format.fprintf
+           f
+           "\"%s\", \"%s\"; "
+           Filename.(chop_suffix (basename file) ".wat")
+           (String.escaped (read_file (open_in_bin file)))))
+    wat_files;
+  Format.printf
+    "let precompiled_runtimes = [%a]@."
+    (Format.pp_print_list (fun f (standard, flags) ->
+         let flags = flags @ default_flags in
+         let name = name_runtime standard flags in
+         match List.find_opt (fun file -> Filename.basename file = name) runtimes with
+         | None -> failwith ("Missing runtime " ^ name)
+         | Some file ->
+             Format.fprintf
+               f
+               "%a, \"%s\"; "
+               print_flags
+               flags
+               (String.escaped (read_file (open_in_bin file)))))
+    (List.mapi (fun i flags -> i = 0, flags) interesting_runtimes)
diff --git a/compiler/lib-wasm/gc_target.ml b/compiler/lib-wasm/gc_target.ml
index cd82902c31..e450183da1 100644
--- a/compiler/lib-wasm/gc_target.ml
+++ b/compiler/lib-wasm/gc_target.ml
@@ -1703,18 +1703,6 @@ let post_process_function_body = Initialize_locals.f
 
 let entry_point ~toplevel_fun =
   let code =
-    let* () =
-      match Config.effects () with
-      | `Cps | `Double_translation ->
-          let* f =
-            register_import
-              ~name:"caml_cps_initialize_effects"
-              (Fun { W.params = []; result = [] })
-          in
-          instr (W.CallInstr (f, []))
-      | `Jspi -> return ()
-      | `Disabled -> assert false
-    in
     let* main =
       register_import
         ~name:"caml_main"
diff --git a/compiler/lib-wasm/generate.ml b/compiler/lib-wasm/generate.ml
index 45f76c6f27..46ba5e4bf4 100644
--- a/compiler/lib-wasm/generate.ml
+++ b/compiler/lib-wasm/generate.ml
@@ -1189,9 +1189,6 @@ let init () =
     ]
   in
   Primitive.register "caml_array_of_uniform_array" `Mutable None None;
-  let l =
-    if effects_cps () then ("caml_alloc_stack", "caml_cps_alloc_stack") :: l else l
-  in
   List.iter ~f:(fun (nm, nm') -> Primitive.alias nm nm') l
 
 (* Make sure we can use [br_table] for switches *)
diff --git a/runtime/wasm/dune b/runtime/wasm/dune
index 0df18be889..778660b290 100644
--- a/runtime/wasm/dune
+++ b/runtime/wasm/dune
@@ -1,10 +1,13 @@
 (install
  (section lib)
  (package wasm_of_ocaml-compiler)
- (files runtime.wasm runtime.js))
+ (files
+  (glob_files *.wat)
+  (glob_files runtime-*.wasm)
+  runtime.js))
 
 (rule
- (target runtime.wasm)
+ (target runtime-standard.wasm)
  (deps
   args
   (glob_files *.wat))
@@ -13,6 +16,21 @@
    ../../compiler/bin-wasm_of_ocaml/wasmoo_link_wasm.exe
    --binaryen=-g
    --binaryen-opt=-O3
+   --set=effects=jspi
+   %{target}
+   %{read-lines:args})))
+
+(rule
+ (target runtime-cps.wasm)
+ (deps
+  args
+  (glob_files *.wat))
+ (action
+  (run
+   ../../compiler/bin-wasm_of_ocaml/wasmoo_link_wasm.exe
+   --binaryen=-g
+   --binaryen-opt=-O3
+   --set=effects=cps
    %{target}
    %{read-lines:args})))
 
diff --git a/runtime/wasm/effect.wat b/runtime/wasm/effect.wat
index 2a579fd1c3..e71be4f60c 100644
--- a/runtime/wasm/effect.wat
+++ b/runtime/wasm/effect.wat
@@ -52,6 +52,88 @@
       (sub $closure
          (struct (field (ref $function_1)) (field (ref $function_3)))))
 
+   ;; Generic fibers
+
+   (type $generic_fiber
+      (sub
+         (struct
+            (field $value (mut (ref eq)))
+            (field $exn (mut (ref eq)))
+            (field $effect (mut (ref eq))))))
+
+   (@string $already_resumed "Effect.Continuation_already_resumed")
+
+   (@string $effect_unhandled "Effect.Unhandled")
+
+   (func $raise_unhandled
+      (param $eff (ref eq)) (param (ref eq)) (result (ref eq))
+      (block $null
+         (call $caml_raise_with_arg
+            (br_on_null $null
+               (call $caml_named_value (global.get $effect_unhandled)))
+            (local.get $eff)))
+      (call $caml_raise_constant
+         (array.new_fixed $block 3 (ref.i31 (global.get $object_tag))
+            (global.get $effect_unhandled)
+            (call $caml_fresh_oo_id (ref.i31 (i32.const 0)))))
+      (ref.i31 (i32.const 0)))
+
+   (global $raise_unhandled (ref $closure)
+      (struct.new $closure (ref.func $raise_unhandled)))
+
+   (global $effect_allowed (mut i32) (i32.const 1))
+
+   (func $caml_continuation_use_noexc (export "caml_continuation_use_noexc")
+      (param (ref eq)) (result (ref eq))
+      (local $cont (ref $block))
+      (local $stack (ref eq))
+      (drop (block $used (result (ref eq))
+         (local.set $cont (ref.cast (ref $block) (local.get 0)))
+         (local.set $stack
+            (br_on_cast_fail $used (ref eq) (ref $generic_fiber)
+               (array.get $block (local.get $cont) (i32.const 1))))
+         (array.set $block (local.get $cont) (i32.const 1)
+            (ref.i31 (i32.const 0)))
+         (return (local.get $stack))))
+      (ref.i31 (i32.const 0)))
+
+   (func (export "caml_continuation_use_and_update_handler_noexc")
+      (param $cont (ref eq)) (param $hval (ref eq)) (param $hexn (ref eq))
+      (param $heff (ref eq)) (result (ref eq))
+      (local $stack (ref eq))
+      (local $tail (ref $generic_fiber))
+      (local.set $stack (call $caml_continuation_use_noexc (local.get $cont)))
+      (if (ref.test (ref $generic_fiber) (local.get $stack))
+         (then
+            (local.set $tail
+               (ref.cast (ref $generic_fiber)
+                  (array.get $block
+                     (ref.cast (ref $block) (local.get $cont))
+                        (i32.const 2))))
+            (struct.set $generic_fiber $value (local.get $tail)
+               (local.get $hval))
+            (struct.set $generic_fiber $exn (local.get $tail) (local.get $hexn))
+            (struct.set $generic_fiber $effect (local.get $tail)
+               (local.get $heff))))
+      (local.get $stack))
+
+   (func (export "caml_get_continuation_callstack")
+      (param (ref eq) (ref eq)) (result (ref eq))
+      (array.new_fixed $block 1 (ref.i31 (i32.const 0))))
+
+   (func (export "caml_is_continuation") (param (ref eq)) (result i32)
+      (drop (block $not_continuation (result (ref eq))
+         (return
+            (ref.eq
+               (array.get $block
+                  (br_on_cast_fail $not_continuation (ref eq) (ref $block)
+                     (local.get 0))
+                  (i32.const 0))
+               (ref.i31 (global.get $cont_tag))))))
+      (i32.const 0))
+
+(@if (= effects "jspi")
+(@then
    ;; Apply a function f to a value v, both contained in a pair (f, v)
 
    (type $pair (struct (field (ref eq)) (field (ref eq))))
@@ -114,13 +196,6 @@
 
    ;; Stack of fibers
 
-   (type $generic_fiber
-      (sub
-         (struct
-            (field $value (mut (ref eq)))
-            (field $exn (mut (ref eq)))
-            (field $effect (mut (ref eq))))))
-
    (type $fiber
       (sub final $generic_fiber
          (struct
@@ -130,24 +205,6 @@
             (field $cont (mut (ref $cont)))
             (field $next (mut (ref null $fiber))))))
 
-   (@string $effect_unhandled "Effect.Unhandled")
-
-   (func $raise_unhandled
-      (param $eff (ref eq)) (param (ref eq)) (result (ref eq))
-      (block $null
-         (call $caml_raise_with_arg
-            (br_on_null $null
-               (call $caml_named_value (global.get $effect_unhandled)))
-            (local.get $eff)))
-      (call $caml_raise_constant
-         (array.new_fixed $block 3 (ref.i31 (global.get $object_tag))
-            (global.get $effect_unhandled)
-            (call $caml_fresh_oo_id (ref.i31 (i32.const 0)))))
-      (ref.i31 (i32.const 0)))
-
-   (global $raise_unhandled (ref $closure)
-      (struct.new $closure (ref.func $raise_unhandled)))
-
    (func $initial_cont (param $p (ref $pair)) (param (ref eq))
       (return_call $start_fiber (local.get $p)))
 
@@ -214,8 +271,6 @@
          (local.get $k)
          (struct.get $cont $cont_func (local.get $k))))
 
-   (@string $already_resumed "Effect.Continuation_already_resumed")
-
    (func $resume (export "%resume")
       (param $stack_head (ref eq)) (param $f (ref eq)) (param $v (ref eq))
       (param $stack_tail (ref eq)) (result (ref eq))
@@ -280,8 +335,6 @@
          (local.get $k1)
          (struct.get $cont $cont_func (local.get $k1))))
 
-   (global $effect_allowed (mut i32) (i32.const 1))
-
    (func (export "%perform") (param $eff (ref eq)) (result (ref eq))
       (if (i32.or (i32.eqz (global.get $effect_allowed))
              (ref.is_null (struct.get $fiber $next (global.get $stack))))
@@ -380,60 +433,10 @@
          (local.get $hv) (local.get $hx) (local.get $hf)
          (global.get $initial_cont)
          (ref.null $fiber)))
+))
 
-   ;; Other functions
-
-   (func $caml_continuation_use_noexc (export "caml_continuation_use_noexc")
-      (param (ref eq)) (result (ref eq))
-      (local $cont (ref $block))
-      (local $stack (ref eq))
-      (drop (block $used (result (ref eq))
-         (local.set $cont (ref.cast (ref $block) (local.get 0)))
-         (local.set $stack
-            (br_on_cast_fail $used (ref eq) (ref $generic_fiber)
-               (array.get $block (local.get $cont) (i32.const 1))))
-         (array.set $block (local.get $cont) (i32.const 1)
-            (ref.i31 (i32.const 0)))
-         (return (local.get $stack))))
-      (ref.i31 (i32.const 0)))
-
-   (func (export "caml_continuation_use_and_update_handler_noexc")
-      (param $cont (ref eq)) (param $hval (ref eq)) (param $hexn (ref eq))
-      (param $heff (ref eq)) (result (ref eq))
-      (local $stack (ref eq))
-      (local $tail (ref $generic_fiber))
-      (local.set $stack (call $caml_continuation_use_noexc (local.get $cont)))
-      (if (ref.test (ref $generic_fiber) (local.get $stack))
-         (then
-            (local.set $tail
-               (ref.cast (ref $generic_fiber)
-                  (array.get $block
-                     (ref.cast (ref $block) (local.get $cont))
-                        (i32.const 2))))
-            (struct.set $generic_fiber $value (local.get $tail)
-               (local.get $hval))
-            (struct.set $generic_fiber $exn (local.get $tail) (local.get $hexn))
-            (struct.set $generic_fiber $effect (local.get $tail)
-               (local.get $heff))))
-      (local.get $stack))
-
-   (func (export "caml_get_continuation_callstack")
-      (param (ref eq) (ref eq)) (result (ref eq))
-      (array.new_fixed $block 1 (ref.i31 (i32.const 0))))
-
-   (func (export "caml_is_continuation") (param (ref eq)) (result i32)
-      (drop (block $not_continuation (result (ref eq))
-         (return
-            (ref.eq
-               (array.get $block
-                  (br_on_cast_fail $not_continuation (ref eq) (ref $block)
-                     (local.get 0))
-                  (i32.const 0))
-               (ref.i31 (global.get $cont_tag))))))
-      (i32.const 0))
-
-   ;; Effects through CPS transformation
-
+(@if (= effects "cps")
+(@then
    (type $function_2
       (func (param (ref eq) (ref eq) (ref eq)) (result (ref eq))))
    (type $function_4
@@ -562,7 +565,7 @@
       (param (ref eq)) (param (ref eq)) (param (ref eq)) (result (ref eq))
       (unreachable))
 
-   (func $caml_trampoline (export "caml_trampoline")
+   (func (export "caml_trampoline")
       (param $f (ref eq)) (param $vargs (ref eq)) (result (ref eq))
       (local $args (ref $block))
       (local $i i32) (local $res (ref eq))
@@ -639,9 +642,6 @@
       (global.set $cps_fiber_stack (local.get $saved_fiber_stack))
       (throw $ocaml_exception (local.get $exn)))
 
-   (global $caml_trampoline_ref (export "caml_trampoline_ref")
-      (mut (ref null $function_1)) (ref.null $function_1))
-
    (func $caml_pop_fiber (result (ref eq))
       (local $f (ref $cps_fiber))
       (local.set $f
@@ -765,7 +765,7 @@
    (global $exn_handler (ref $closure)
       (struct.new $closure (ref.func $exn_handler)))
 
-   (func (export "caml_cps_alloc_stack")
+   (func (export "caml_alloc_stack")
       (param $hv (ref eq)) (param $hx (ref eq)) (param $hf (ref eq))
       (result (ref eq))
       (struct.new $cps_fiber
@@ -773,9 +773,7 @@
          (global.get $value_handler)
          (struct.new $exn_stack (global.get $exn_handler) (ref.null $exn_stack))
          (ref.null $cps_fiber)))
-
-   (func (export "caml_cps_initialize_effects")
-      (global.set $caml_trampoline_ref (ref.func $caml_trampoline)))
+))
 
    (func (export "caml_assume_no_perform") (param $f (ref eq)) (result (ref eq))
       (local $saved_effect_allowed i32)
diff --git a/runtime/wasm/obj.wat b/runtime/wasm/obj.wat
index 8e44ecd376..4eba296265 100644
--- a/runtime/wasm/obj.wat
+++ b/runtime/wasm/obj.wat
@@ -23,8 +23,12 @@
       (func $caml_dup_custom (param (ref eq)) (result (ref eq))))
    (import "effect" "caml_is_continuation"
       (func $caml_is_continuation (param (ref eq)) (result i32)))
-   (import "effect" "caml_trampoline_ref"
-      (global $caml_trampoline_ref (mut (ref null $function_1))))
+(@if (= effects "cps")
+(@then
+   (import "effect" "caml_trampoline"
+      (func $caml_trampoline (param (ref eq) (ref eq)) (result (ref eq))))
+))
+
 
    (type $block (array (mut (ref eq))))
    (type $bytes (array (mut i8)))
@@ -452,18 +456,28 @@
    (func (export "caml_obj_reachable_words") (param (ref eq)) (result (ref eq))
       (ref.i31 (i32.const 0)))
 
+(@if (= effects "cps")
+(@then
    (func $caml_callback_1 (export "caml_callback_1")
       (param $f (ref eq)) (param $x (ref eq)) (result (ref eq))
-      (drop (block $cps (result (ref eq))
-         (return_call_ref $function_1 (local.get $x)
-            (local.get $f)
-            (struct.get $closure 0
-               (br_on_cast_fail $cps (ref eq) (ref $closure)
-                  (local.get $f))))))
-      (return_call_ref $function_1
+      (return_call $caml_trampoline
+         (local.get $f)
+         (array.new_fixed $block 2 (ref.i31 (i32.const 0)) (local.get $x))))
+
+   (func (export "caml_callback_2")
+      (param $f (ref eq)) (param $x (ref eq)) (param $y (ref eq))
+      (result (ref eq))
+      (return_call $caml_trampoline
          (local.get $f)
-         (array.new_fixed $block 2 (ref.i31 (i32.const 0)) (local.get $x))
-         (ref.as_non_null (global.get $caml_trampoline_ref))))
+         (array.new_fixed $block 3 (ref.i31 (i32.const 0))
+           (local.get $x) (local.get $y))))
+)
+(@else
+   (func $caml_callback_1 (export "caml_callback_1")
+      (param $f (ref eq)) (param $x (ref eq)) (result (ref eq))
+      (return_call_ref $function_1 (local.get $x)
+         (local.get $f)
+         (struct.get $closure 0 (ref.cast (ref $closure) (local.get $f)))))
 
    (func (export "caml_callback_2")
       (param $f (ref eq)) (param $x (ref eq)) (param $y (ref eq))
@@ -474,15 +488,8 @@
             (struct.get $closure_2 1
                (br_on_cast_fail $not_direct (ref eq) (ref $closure_2)
                   (local.get $f))))))
-      (if (ref.test (ref $closure) (local.get $f))
-         (then
-            (return_call $caml_callback_1
-               (call $caml_callback_1 (local.get $f) (local.get $x))
-               (local.get $y)))
-         (else
-            (return_call_ref $function_1
-               (local.get $f)
-               (array.new_fixed $block 3 (ref.i31 (i32.const 0))
-                 (local.get $x) (local.get $y))
-               (ref.as_non_null (global.get $caml_trampoline_ref))))))
+      (return_call $caml_callback_1
+         (call $caml_callback_1 (local.get $f) (local.get $x))
+         (local.get $y)))
+))
 )