diff --git a/apps/server/src/provider/Layers/CodexProvider.ts b/apps/server/src/provider/Layers/CodexProvider.ts
index a0e2b744c2a72febda1f4bc8a5c51238acf98457..cdf40f73b1bdddab0cbfdb52b16de68cd1509364 100644
--- a/apps/server/src/provider/Layers/CodexProvider.ts
+++ b/apps/server/src/provider/Layers/CodexProvider.ts
@@ -628,7 +628,10 @@ export const checkCodexProviderStatus = Effect.fn("checkCodexProviderStatus")(fu
         auth: { status: "unknown" },
         message: installed
           ? `Codex app-server provider probe failed: ${error.message}.`
-          : "Codex CLI (`codex`) was not found on PATH.",
+          : `Could not start Codex CLI (\`${codexSettings.binaryPath}\`). Check Settings → Providers → Codex → Binary path on the server.` +
+            (codexSettings.binaryPath === "codex"
+              ? " Installing ChatGPT or Codex desktop may not add codex to PATH."
+              : " Make sure the configured executable exists and can be run."),
       },
     });
   }
diff --git a/apps/server/src/provider/Layers/ProviderRegistry.test.ts b/apps/server/src/provider/Layers/ProviderRegistry.test.ts
index 988c89e1e679d5782c0b1c4ba08af3195e73cf35..caee1981d79f3fd269a42ed3161818dfbf5a1ea3 100644
--- a/apps/server/src/provider/Layers/ProviderRegistry.test.ts
+++ b/apps/server/src/provider/Layers/ProviderRegistry.test.ts
@@ -513,20 +513,35 @@ it.layer(Layer.mergeAll(NodeServices.layer, ServerSettingsModule.layerTest(), Te
         }),
       );
 
-      it.effect("returns unavailable when codex is missing", () =>
+      it.effect.each([
+        "codex",
+        "/Applications/Custom App.app/Contents/Resources/codex",
+        "C:\\Tools\\codex.exe",
+      ])("explains how to configure a Codex executable that cannot start: %s", (binaryPath) =>
         Effect.gen(function* () {
-          const status = yield* checkCodexProviderStatus(defaultCodexSettings, () =>
-            Effect.fail(
+          const settings = { ...defaultCodexSettings, binaryPath };
+          const status = yield* checkCodexProviderStatus(settings, (input) => {
+            assert.strictEqual(input.binaryPath, binaryPath);
+            return Effect.fail(
               new CodexErrors.CodexAppServerSpawnError({
-                command: "codex app-server",
-                cause: new Error("spawn codex ENOENT"),
+                command: `${binaryPath} app-server`,
+                cause: new Error("spawn ENOENT"),
               }),
-            ),
-          );
+            );
+          });
           assert.strictEqual(status.status, "error");
           assert.strictEqual(status.installed, false);
           assert.strictEqual(status.auth.status, "unknown");
-          assert.strictEqual(status.message, "Codex CLI (`codex`) was not found on PATH.");
+          assert.include(status.message, binaryPath);
+          assert.include(
+            status.message,
+            "Settings → Providers → Codex → Binary path on the server",
+          );
+          assert.strictEqual(
+            status.message?.includes("Installing ChatGPT or Codex desktop"),
+            binaryPath === "codex",
+          );
+          assert.strictEqual(settings.binaryPath, binaryPath);
         }),
       );
 
@@ -2331,10 +2346,8 @@ it.layer(Layer.mergeAll(NodeServices.layer, ServerSettingsModule.layerTest(), Te
               "Real Codex probe against a missing binary should surface as 'error' in the aggregator",
             );
             assert.strictEqual(codexPersonal?.installed, false);
-            assert.strictEqual(
-              codexPersonal?.message,
-              "Codex CLI (`codex`) was not found on PATH.",
-            );
+            assert.include(codexPersonal?.message, missingBinary);
+            assert.include(codexPersonal?.message, "Settings → Providers → Codex → Binary path");
           }).pipe(Effect.provide(runtimeServices));
         }),
       );