diff --git a/dist/index.js b/dist/index.js
index f9c3efc7f..05401967b 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -92818,6 +92818,21 @@ async function setupOpam() {
         await initializeOpam();
     });
 }
+function setupOpamEnv() {
+    const githubWorkspace = process.env.GITHUB_WORKSPACE ?? process.cwd();
+    const OPAM_SWITCH_PREFIX = external_node_path_namespaceObject.join(githubWorkspace, "_opam");
+    const CAML_LD_LIBRARY_PATH = [
+        external_node_path_namespaceObject.join(OPAM_SWITCH_PREFIX, "lib", "stublibs"),
+        external_node_path_namespaceObject.join(OPAM_SWITCH_PREFIX, "lib", "ocaml", "stublibs"),
+        external_node_path_namespaceObject.join(OPAM_SWITCH_PREFIX, "lib", "ocaml"),
+    ].join(external_node_path_namespaceObject.delimiter);
+    const OCAML_TOPLEVEL_PATH = external_node_path_namespaceObject.join(OPAM_SWITCH_PREFIX, "lib", "toplevel");
+    const OPAM_SWITCH_BIN = external_node_path_namespaceObject.join(OPAM_SWITCH_PREFIX, "bin");
+    lib_core.exportVariable("OPAM_SWITCH_PREFIX", OPAM_SWITCH_PREFIX);
+    lib_core.exportVariable("CAML_LD_LIBRARY_PATH", CAML_LD_LIBRARY_PATH);
+    lib_core.exportVariable("OCAML_TOPLEVEL_PATH", OCAML_TOPLEVEL_PATH);
+    lib_core.addPath(OPAM_SWITCH_BIN);
+}
 async function installOcaml(ocamlCompiler) {
     await lib_core.group("Install OCaml", async () => {
         await (0,lib_exec.exec)("opam", [
@@ -110482,14 +110497,7 @@ async function trimDuneCache() {
             run_id,
         });
         const cacheSize = Math.floor(5000 / totalCount);
-        await exec("opam", [
-            "exec",
-            "--",
-            "dune",
-            "cache",
-            "trim",
-            `--size=${cacheSize}MB`,
-        ]);
+        await exec("dune", ["dune", "cache", "trim", `--size=${cacheSize}MB`]);
     });
 }
 
@@ -110558,6 +110566,7 @@ async function installer() {
         await installOcaml(ocamlCompiler);
         await saveOpamCache();
     }
+    setupOpamEnv();
     if (DUNE_CACHE) {
         await restoreDuneCache();
         await installDune();
@@ -110565,7 +110574,6 @@ async function installer() {
         lib_core.exportVariable("DUNE_CACHE_TRANSPORT", "direct");
         lib_core.exportVariable("DUNE_CACHE_STORAGE_MODE", "copy");
     }
-    lib_core.exportVariable("CLICOLOR_FORCE", "1");
     const fnames = await getOpamLocalPackages();
     if (fnames.length > 0) {
         if (OPAM_PIN) {
@@ -110573,7 +110581,7 @@ async function installer() {
         }
     }
     await (0,lib_exec.exec)("opam", ["--version"]);
-    await (0,lib_exec.exec)("opam", ["exec", "--", "ocaml", "-version"]);
+    await (0,lib_exec.exec)("ocaml", ["-version"]);
 }
 
 ;// CONCATENATED MODULE: ./src/index.ts
diff --git a/dist/post/index.js b/dist/post/index.js
index 3d77ca75c..5be087adf 100644
--- a/dist/post/index.js
+++ b/dist/post/index.js
@@ -84985,14 +84985,7 @@ async function trimDuneCache() {
             run_id,
         });
         const cacheSize = Math.floor(5000 / totalCount);
-        await (0,lib_exec.exec)("opam", [
-            "exec",
-            "--",
-            "dune",
-            "cache",
-            "trim",
-            `--size=${cacheSize}MB`,
-        ]);
+        await (0,lib_exec.exec)("dune", ["dune", "cache", "trim", `--size=${cacheSize}MB`]);
     });
 }
 
diff --git a/lint-doc/dist/index.js b/lint-doc/dist/index.js
index ac1c2a254..f2b5e52c1 100644
--- a/lint-doc/dist/index.js
+++ b/lint-doc/dist/index.js
@@ -27920,7 +27920,7 @@ var exec = __nccwpck_require__(6473);
 
 
 async function lintOdoc() {
-    const exitCode = await (0,exec.exec)("opam", ["exec", "--", "dune", "build", "@doc"], {
+    const exitCode = await (0,exec.exec)("dune", ["build", "@doc"], {
         env: {
             ...external_node_process_namespaceObject.env,
             PATH: external_node_process_namespaceObject.env.PATH ?? "",
diff --git a/lint-fmt/dist/index.js b/lint-fmt/dist/index.js
index 4168291c7..82f2519fc 100644
--- a/lint-fmt/dist/index.js
+++ b/lint-fmt/dist/index.js
@@ -27919,7 +27919,7 @@ var exec = __nccwpck_require__(6473);
 ;// CONCATENATED MODULE: ./src/lint.ts
 
 async function checkFmt() {
-    await (0,exec.exec)("opam", ["exec", "--", "dune", "build", "@fmt"]);
+    await (0,exec.exec)("dune", ["build", "@fmt"]);
 }
 
 ;// CONCATENATED MODULE: external "node:fs"
diff --git a/lint-opam/dist/index.js b/lint-opam/dist/index.js
index dbb4929b1..8ccfd9f24 100644
--- a/lint-opam/dist/index.js
+++ b/lint-opam/dist/index.js
@@ -27922,7 +27922,7 @@ async function opamLint() {
     await (0,exec.exec)("opam", ["lint"]);
 }
 async function opamDuneLint() {
-    await (0,exec.exec)("opam", ["exec", "--", "opam-dune-lint"]);
+    await (0,exec.exec)("opam-dune-lint");
 }
 
 ;// CONCATENATED MODULE: ./src/opam.ts
diff --git a/packages/lint-doc/src/odoc.ts b/packages/lint-doc/src/odoc.ts
index 2514f9161..d11d9acb0 100644
--- a/packages/lint-doc/src/odoc.ts
+++ b/packages/lint-doc/src/odoc.ts
@@ -2,7 +2,7 @@ import * as process from "node:process";
 import { exec } from "@actions/exec";
 
 export async function lintOdoc() {
-  const exitCode = await exec("opam", ["exec", "--", "dune", "build", "@doc"], {
+  const exitCode = await exec("dune", ["build", "@doc"], {
     env: {
       ...process.env,
       PATH: process.env.PATH ?? "",
diff --git a/packages/lint-fmt/src/lint.ts b/packages/lint-fmt/src/lint.ts
index eba1ab5cf..3301eda51 100644
--- a/packages/lint-fmt/src/lint.ts
+++ b/packages/lint-fmt/src/lint.ts
@@ -1,5 +1,5 @@
 import { exec } from "@actions/exec";
 
 export async function checkFmt() {
-  await exec("opam", ["exec", "--", "dune", "build", "@fmt"]);
+  await exec("dune", ["build", "@fmt"]);
 }
diff --git a/packages/lint-opam/src/lint.ts b/packages/lint-opam/src/lint.ts
index 2ef46e2c6..5c13353f9 100644
--- a/packages/lint-opam/src/lint.ts
+++ b/packages/lint-opam/src/lint.ts
@@ -5,5 +5,5 @@ export async function opamLint() {
 }
 
 export async function opamDuneLint() {
-  await exec("opam", ["exec", "--", "opam-dune-lint"]);
+  await exec("opam-dune-lint");
 }
diff --git a/packages/setup-ocaml/src/dune.ts b/packages/setup-ocaml/src/dune.ts
index 2c3c49bd2..864a4bba7 100644
--- a/packages/setup-ocaml/src/dune.ts
+++ b/packages/setup-ocaml/src/dune.ts
@@ -27,14 +27,7 @@ export async function trimDuneCache() {
         run_id,
       });
       const cacheSize = Math.floor(5000 / totalCount);
-      await exec("opam", [
-        "exec",
-        "--",
-        "dune",
-        "cache",
-        "trim",
-        `--size=${cacheSize}MB`,
-      ]);
+      await exec("dune", ["dune", "cache", "trim", `--size=${cacheSize}MB`]);
     },
   );
 }
diff --git a/packages/setup-ocaml/src/installer.ts b/packages/setup-ocaml/src/installer.ts
index 3e271a0fb..dbe8974f5 100644
--- a/packages/setup-ocaml/src/installer.ts
+++ b/packages/setup-ocaml/src/installer.ts
@@ -24,6 +24,7 @@ import {
   repositoryAddAll,
   repositoryRemoveAll,
   setupOpam,
+  setupOpamEnv,
 } from "./opam.js";
 import { getOpamLocalPackages } from "./packages.js";
 import { resolveCompiler } from "./version.js";
@@ -71,6 +72,7 @@ export async function installer() {
     await installOcaml(ocamlCompiler);
     await saveOpamCache();
   }
+  setupOpamEnv();
   if (DUNE_CACHE) {
     await restoreDuneCache();
     await installDune();
@@ -78,7 +80,6 @@ export async function installer() {
     core.exportVariable("DUNE_CACHE_TRANSPORT", "direct");
     core.exportVariable("DUNE_CACHE_STORAGE_MODE", "copy");
   }
-  core.exportVariable("CLICOLOR_FORCE", "1");
   const fnames = await getOpamLocalPackages();
   if (fnames.length > 0) {
     if (OPAM_PIN) {
@@ -86,5 +87,5 @@ export async function installer() {
     }
   }
   await exec("opam", ["--version"]);
-  await exec("opam", ["exec", "--", "ocaml", "-version"]);
+  await exec("ocaml", ["-version"]);
 }
diff --git a/packages/setup-ocaml/src/opam.ts b/packages/setup-ocaml/src/opam.ts
index a3e8bdfc2..7b96f08cc 100644
--- a/packages/setup-ocaml/src/opam.ts
+++ b/packages/setup-ocaml/src/opam.ts
@@ -120,6 +120,22 @@ export async function setupOpam() {
   });
 }
 
+export function setupOpamEnv() {
+  const githubWorkspace = process.env.GITHUB_WORKSPACE ?? process.cwd();
+  const OPAM_SWITCH_PREFIX = path.join(githubWorkspace, "_opam");
+  const CAML_LD_LIBRARY_PATH = [
+    path.join(OPAM_SWITCH_PREFIX, "lib", "stublibs"),
+    path.join(OPAM_SWITCH_PREFIX, "lib", "ocaml", "stublibs"),
+    path.join(OPAM_SWITCH_PREFIX, "lib", "ocaml"),
+  ].join(path.delimiter);
+  const OCAML_TOPLEVEL_PATH = path.join(OPAM_SWITCH_PREFIX, "lib", "toplevel");
+  const OPAM_SWITCH_BIN = path.join(OPAM_SWITCH_PREFIX, "bin");
+  core.exportVariable("OPAM_SWITCH_PREFIX", OPAM_SWITCH_PREFIX);
+  core.exportVariable("CAML_LD_LIBRARY_PATH", CAML_LD_LIBRARY_PATH);
+  core.exportVariable("OCAML_TOPLEVEL_PATH", OCAML_TOPLEVEL_PATH);
+  core.addPath(OPAM_SWITCH_BIN);
+}
+
 export async function installOcaml(ocamlCompiler: string) {
   await core.group("Install OCaml", async () => {
     await exec("opam", [