diff --git a/.changeset/big-boats-lay.md b/.changeset/big-boats-lay.md
new file mode 100644
index 0000000000..233d05975f
--- /dev/null
+++ b/.changeset/big-boats-lay.md
@@ -0,0 +1,5 @@
+---
+"@blitzjs/generator": patch
+---
+
+Guard `blitz g` input via an allow-list of characters; throw if unwanted characters are found. Prevents to break the blitz command by accident (https://github.com/blitz-js/blitz/issues/4021).
diff --git a/packages/generator/src/generators/model-generator.ts b/packages/generator/src/generators/model-generator.ts
index 2d10b25e31..c9163eb96a 100644
--- a/packages/generator/src/generators/model-generator.ts
+++ b/packages/generator/src/generators/model-generator.ts
@@ -2,11 +2,12 @@ import * as ast from "@mrleebo/prisma-ast"
 import {spawn} from "cross-spawn"
 import which from "npm-which"
 import path from "path"
-import {log} from "../utils/log"
 import {Generator, GeneratorOptions, SourceRootType} from "../generator"
 import {Field} from "../prisma/field"
 import {Model} from "../prisma/model"
+import {checkInputsOrRaise} from "../utils/checkInputOrRaise"
 import {getTemplateRoot} from "../utils/get-template-root"
+import {log} from "../utils/log"
 
 export interface ModelGeneratorOptions extends GeneratorOptions {
   modelName: string
@@ -59,9 +60,13 @@ export class ModelGenerator extends Generator<ModelGeneratorOptions> {
     const {modelName, extraArgs, dryRun} = this.options
     let updatedOrCreated = "created"
 
-    let fields = (
-      extraArgs.length === 1 && extraArgs[0]?.includes(" ") ? extraArgs[0]?.split(" ") : extraArgs
-    ).flatMap((input) => Field.parse(input, schema))
+    const splitInputCommans = (input: typeof extraArgs) => {
+      const inputs = input.length === 1 && input[0]?.includes(" ") ? input[0]?.split(" ") : input
+      checkInputsOrRaise(inputs)
+      return inputs
+    }
+
+    let fields = splitInputCommans(extraArgs).flatMap((input) => Field.parse(input, schema))
 
     const modelDefinition = new Model(modelName, fields)
 
diff --git a/packages/generator/src/prisma/field.ts b/packages/generator/src/prisma/field.ts
index c40056d3d4..e7260126ab 100644
--- a/packages/generator/src/prisma/field.ts
+++ b/packages/generator/src/prisma/field.ts
@@ -1,4 +1,5 @@
 import * as ast from "@mrleebo/prisma-ast"
+import {checkInputsOrRaise} from "../utils/checkInputOrRaise"
 import {capitalize, singlePascal, uncapitalize} from "../utils/inflector"
 
 export enum FieldType {
@@ -55,6 +56,8 @@ export class Field {
 
   // 'name:type?[]:attribute' => Field
   static parse(input: string, schema?: ast.Schema): Field[] {
+    checkInputsOrRaise(input)
+
     const [_fieldName, _fieldType = "String", _attribute] = input.split(":")
     let attribute = _attribute as string
     let fieldName = uncapitalize(_fieldName as string)
diff --git a/packages/generator/src/utils/checkInputOrRaise.ts b/packages/generator/src/utils/checkInputOrRaise.ts
new file mode 100644
index 0000000000..cddae0b92a
--- /dev/null
+++ b/packages/generator/src/utils/checkInputOrRaise.ts
@@ -0,0 +1,28 @@
+import chalk from "chalk"
+import {log} from "./log"
+
+export const checkInputsOrRaise = (inputs: string[] | string) => {
+  if (typeof inputs === "string") {
+    checkInputOrRaise(inputs)
+  } else {
+    inputs.forEach((input) => checkInputOrRaise(input))
+  }
+}
+
+const checkInputOrRaise = (input: string) => {
+  const regex = /^[a-zA-Z0-9-_:=\?[\]\s]+$/
+  if (!regex.test(input)) {
+    const firstInvalidCharacter = input.match(/[^a-zA-Z0-9-_:=\?[\]\s]/)
+    if (firstInvalidCharacter) {
+      log.branded(
+        "Blitz Generator Parser Error: " +
+          chalk.red(
+            `Input contains invalid character: "${firstInvalidCharacter[0]}" in ${firstInvalidCharacter.input} at position ${firstInvalidCharacter.index}`,
+          ),
+      )
+    }
+    throw new Error(
+      "Input should only contain alphanumeric characters, spaces, and the following characters: - _ : = ? [ ]",
+    )
+  }
+}
diff --git a/packages/generator/test/generators/utils/checkInputOrRaise.test.ts b/packages/generator/test/generators/utils/checkInputOrRaise.test.ts
new file mode 100644
index 0000000000..ea103980c5
--- /dev/null
+++ b/packages/generator/test/generators/utils/checkInputOrRaise.test.ts
@@ -0,0 +1,26 @@
+import {checkInputsOrRaise} from "../../../../generator/src/utils/checkInputOrRaise"
+import {describe, expect, it} from "vitest"
+
+describe("checkInputsOrRaise()", () => {
+  describe("with input string", () => {
+    it("does not raise when input string OK", () => {
+      expect(() => checkInputsOrRaise("Foo:foo=bar[]?:-_ ")).not.toThrow()
+    })
+    it("raisees when input has unwanted characters", () => {
+      expect(() => checkInputsOrRaise("()!")).toThrowError(
+        "Input should only contain alphanumeric characters, spaces, and the following characters: - _ : = ? [ ]",
+      )
+    })
+  })
+
+  describe("with input string[]", () => {
+    it("does not raise when input strings OK", () => {
+      expect(() => checkInputsOrRaise(["ok:ok=ok", "also ok:ok"])).not.toThrow()
+    })
+    it("raisees when one input has unwanted characters", () => {
+      expect(() => checkInputsOrRaise(["ok:ok=ok", "not ok!"])).toThrowError(
+        "Input should only contain alphanumeric characters, spaces, and the following characters: - _ : = ? [ ]",
+      )
+    })
+  })
+})
diff --git a/packages/generator/test/prisma/field.test.ts b/packages/generator/test/prisma/field.test.ts
index 75f6f1e8b0..febfe0a77a 100644
--- a/packages/generator/test/prisma/field.test.ts
+++ b/packages/generator/test/prisma/field.test.ts
@@ -28,6 +28,14 @@ describe("Field", () => {
     expect(field?.default).toMatchObject({name: "uuid"})
   })
 
+  it("disallow brackes `()` as default attribute", () => {
+    expect(() => Field.parse("id:string:default=now()")).toThrow()
+  })
+
+  it("disallow not allowed characters like `!`", () => {
+    expect(() => Field.parse("id:string!")).toThrow()
+  })
+
   it("handles uuid convenience syntax", () => {
     const [field] = Field.parse("someSpecialToken:uuid")
     expect(field?.type).toBe("String")