diff --git a/package.json b/package.json
index f330ae7..4e75e06 100644
--- a/package.json
+++ b/package.json
@@ -117,6 +117,7 @@
     "test:relay": "jest --testPathPatterns=Relay",
     "test:locale": "jest --testPathPatterns=Locale",
     "test:manifest": "jest --testPathPatterns=src/cli/builders/manifest",
+    "test:typescript": "jest --testPathPatterns=src/cli/builders/typescript",
     "test:entrypoint": "jest --testPathPatterns=src/cli/entrypoint",
     "test:plugins": "jest --testPathPatterns=src/cli/plugins",
     "release": "release-it",
diff --git a/src/cli/builders/typescript/ConfigBuilder.test.ts b/src/cli/builders/typescript/ConfigBuilder.test.ts
new file mode 100644
index 0000000..0548181
--- /dev/null
+++ b/src/cli/builders/typescript/ConfigBuilder.test.ts
@@ -0,0 +1,188 @@
+import {ConfigBuilder} from "./ConfigBuilder";
+
+describe("TypeScript ConfigBuilder", () => {
+    let cfg: ReturnType<typeof ConfigBuilder.from>;
+
+    beforeEach(() => {
+        cfg = ConfigBuilder.from();
+    });
+
+    it("sets and gets nested value", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        expect(cfg.get("compilerOptions.target")).toBe("esnext");
+    });
+
+    it("creates missing nested objects on set", () => {
+        cfg.set("compilerOptions.strict", true);
+
+        expect(cfg.get("compilerOptions")).toEqual({
+            strict: true,
+        });
+    });
+
+    it("supports creating multiple nested properties across different paths", () => {
+        cfg.set("compilerOptions.types", ["jest"]);
+        cfg.set("compilerOptions.lib", ["es2020"]);
+
+        expect(cfg.get("compilerOptions")).toEqual({
+            types: ["jest"],
+            lib: ["es2020"],
+        });
+    });
+
+    it("returns undefined for a non-existing path", () => {
+        expect(cfg.get("compilerOptions.module")).toBeUndefined();
+    });
+
+    it("has() returns true for an existing path", () => {
+        cfg.set("compilerOptions.strict", true);
+
+        expect(cfg.has("compilerOptions.strict")).toBe(true);
+    });
+
+    it("has() returns false for a non-existing path", () => {
+        expect(cfg.has("compilerOptions.module")).toBe(false);
+    });
+
+    it("deletes a nested property", () => {
+        cfg.set("compilerOptions.module", "commonjs");
+        cfg.delete("compilerOptions.module");
+
+        expect(cfg.get("compilerOptions.module")).toBeUndefined();
+    });
+
+    it("delete does nothing for non-existing path", () => {
+        expect(() => cfg.delete("compilerOptions.module")).not.toThrow();
+    });
+
+    it("set/delete/merge/raw return the builder instance for chaining", () => {
+        const a = cfg.set("compilerOptions.target", "esnext");
+        const b = cfg.delete("compilerOptions.baseUrl");
+        const c = cfg.merge({include: ["src/**/*.ts"]});
+        const d = cfg.raw({compilerOptions: {strict: true}});
+        expect(a).toBe(cfg);
+        expect(b).toBe(cfg);
+        expect(c).toBe(cfg);
+        expect(d).toBe(cfg);
+    });
+
+    it("deep-merges objects without removing existing keys", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        cfg.merge({
+            compilerOptions: {
+                strict: true,
+            },
+        });
+
+        expect(cfg.get()).toEqual({
+            compilerOptions: {
+                target: "esnext",
+                strict: true,
+            },
+        });
+    });
+
+    it("overwrites arrays on merge", () => {
+        cfg.merge({
+            include: ["src/**/*.ts"],
+        });
+
+        cfg.merge({
+            include: ["tests/**/*.ts"],
+        });
+
+        expect(cfg.get("include")).toEqual(["tests/**/*.ts"]);
+    });
+
+    it("raw() behaves like merge()", () => {
+        cfg.raw({
+            compilerOptions: {
+                module: "commonjs",
+            },
+        });
+
+        expect(cfg.get("compilerOptions.module")).toBe("commonjs");
+    });
+
+    it("from(initial) clones the initial object (no shared references)", () => {
+        const initial = {compilerOptions: {target: "es5"}} as any;
+        const local = ConfigBuilder.from(initial);
+
+        (initial as any).compilerOptions.target = "es3";
+        expect(local.get("compilerOptions.target")).toBe("es5");
+
+        local.set("compilerOptions.module", "commonjs");
+        expect((initial as any).compilerOptions.module).toBeUndefined();
+    });
+
+    it("get() returns a deep-cloned read-only snapshot", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        const snapshot = cfg.get();
+
+        expect(snapshot).toEqual({
+            compilerOptions: {
+                target: "esnext",
+            },
+        });
+    });
+
+    it("mutating the snapshot does not affect internal state", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        const snapshot = cfg.get();
+
+        try {
+            (snapshot as any).compilerOptions.target = "es5";
+        } catch {}
+
+        expect(cfg.get("compilerOptions.target")).toBe("esnext");
+    });
+
+    it("toJSON returns a JSON string of the current config", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        const json = cfg.toJSON();
+
+        expect(typeof json).toBe("string");
+        expect(json).toBe(
+            JSON.stringify({
+                compilerOptions: {target: "esnext"},
+            })
+        );
+    });
+
+    it("set overwrites a primitive value with an object when needed", () => {
+        cfg.set("compilerOptions", {} as any);
+        cfg.set("compilerOptions.strict", true);
+
+        expect(cfg.get("compilerOptions.strict")).toBe(true);
+    });
+
+    it("delete removes only the targeted leaf, preserving siblings", () => {
+        cfg.set("compilerOptions.target", "esnext");
+        cfg.set("compilerOptions.strict", true);
+
+        cfg.delete("compilerOptions.target");
+
+        expect(cfg.get()).toEqual({
+            compilerOptions: {
+                strict: true,
+            },
+        });
+    });
+
+    it("merge does not remove existing keys (idempotent addition)", () => {
+        cfg.set("compilerOptions.target", "esnext");
+
+        cfg.merge({
+            compilerOptions: {
+                strict: true,
+            },
+        });
+
+        expect(cfg.get("compilerOptions.target")).toBe("esnext");
+    });
+});
diff --git a/src/cli/builders/typescript/ConfigBuilder.ts b/src/cli/builders/typescript/ConfigBuilder.ts
new file mode 100644
index 0000000..f7939cb
--- /dev/null
+++ b/src/cli/builders/typescript/ConfigBuilder.ts
@@ -0,0 +1,88 @@
+import _ from "lodash";
+
+import {isPlainObject, mergeDeep} from "./utils";
+
+import type {PartialDeep, TsConfigJson} from "type-fest";
+
+import type {DotPath, PathValue, TsConfigBuilder} from "@typing/typescript";
+
+export class ConfigBuilder implements TsConfigBuilder {
+    private readonly state?: TsConfigJson;
+
+    private constructor(initial?: TsConfigJson) {
+        this.state = mergeDeep({}, initial || {});
+    }
+
+    static from(initial?: TsConfigJson): TsConfigBuilder {
+        return new ConfigBuilder(initial);
+    }
+
+    public get(): TsConfigJson;
+    public get<P extends DotPath<TsConfigJson>>(path: P): PathValue<TsConfigJson, P> | undefined;
+    public get(path?: string) {
+        if (!path) {
+            return _.cloneDeep(this.state);
+        }
+
+        const segments = path.split(".");
+        let current: any = this.state;
+
+        for (const segment of segments) {
+            if (!current || typeof current !== "object") {
+                return undefined;
+            }
+            current = current[segment];
+        }
+
+        return current;
+    }
+
+    public set<P extends DotPath<TsConfigJson>>(path: P, value: PathValue<TsConfigJson, P>) {
+        const segments = path.split(".");
+        let current: any = this.state;
+
+        while (segments.length > 1) {
+            const segment = segments.shift()!;
+            if (!isPlainObject(current[segment])) {
+                current[segment] = {};
+            }
+            current = current[segment];
+        }
+
+        current[segments[0]] = value;
+        return this;
+    }
+
+    public has(path: DotPath<TsConfigJson>): boolean {
+        return this.get(path) !== undefined;
+    }
+
+    public delete(path: DotPath<TsConfigJson>) {
+        const segments = path.split(".");
+        let current: any = this.state;
+
+        while (segments.length > 1) {
+            const segment = segments.shift()!;
+            if (!isPlainObject(current[segment])) {
+                return this;
+            }
+            current = current[segment];
+        }
+
+        delete current[segments[0]];
+        return this;
+    }
+
+    public merge(config: PartialDeep<TsConfigJson>) {
+        return this.raw(config);
+    }
+
+    public raw(config: PartialDeep<TsConfigJson>) {
+        mergeDeep(this.state || {}, config);
+        return this;
+    }
+
+    public toJSON(): string {
+        return JSON.stringify(this.get());
+    }
+}
diff --git a/src/cli/builders/typescript/index.ts b/src/cli/builders/typescript/index.ts
new file mode 100644
index 0000000..4097ad9
--- /dev/null
+++ b/src/cli/builders/typescript/index.ts
@@ -0,0 +1 @@
+export {ConfigBuilder} from "./ConfigBuilder";
diff --git a/src/cli/builders/typescript/utils.ts b/src/cli/builders/typescript/utils.ts
new file mode 100644
index 0000000..59cb73a
--- /dev/null
+++ b/src/cli/builders/typescript/utils.ts
@@ -0,0 +1,18 @@
+import _ from "lodash";
+
+import type {PartialDeep} from "type-fest";
+
+export function isPlainObject(value: unknown): value is Record<string, unknown> {
+    if (typeof value !== "object" || value === null) return false;
+
+    const proto = Object.getPrototypeOf(value);
+    return proto === Object.prototype || proto === null;
+}
+
+export function mergeDeep<T extends object>(target: T, source: PartialDeep<T>): T {
+    return _.mergeWith(target, source, (_objValue, srcValue) => {
+        if (Array.isArray(srcValue)) {
+            return srcValue;
+        }
+    });
+}
diff --git a/src/cli/plugins/typescript/TypescriptConfig.ts b/src/cli/plugins/typescript/TypescriptConfig.ts
index 3ea3c2a..78e5226 100644
--- a/src/cli/plugins/typescript/TypescriptConfig.ts
+++ b/src/cli/plugins/typescript/TypescriptConfig.ts
@@ -10,6 +10,8 @@ import {ReadonlyConfig} from "@typing/config";
 import {PackageName} from "@typing/app";
 
 export default class extends FileBuilder {
+    protected tsConfig: TsConfigJson = {};
+
     protected readonly vendorAliases = {
         [`${PackageName}/browser`]: "@addon-core/browser",
         [`${PackageName}/storage`]: "@addon-core/storage",
@@ -32,7 +34,13 @@ export default class extends FileBuilder {
     }
 
     protected content(): string {
-        return JSON.stringify(this.json(), null, 2);
+        const json = _.mergeWith(this.tsConfig, this.json(), (_objValue, srcValue) => {
+            if (Array.isArray(srcValue)) {
+                return srcValue;
+            }
+        });
+
+        return JSON.stringify(json, null, 2);
     }
 
     protected alias(): Record<string, string> {
@@ -86,4 +94,15 @@ export default class extends FileBuilder {
             exclude: [outputDir],
         };
     }
+
+    public merge(config?: TsConfigJson) {
+        if (config) {
+            this.tsConfig = _.mergeWith(this.tsConfig, config, (_objValue, srcValue) => {
+                if (Array.isArray(srcValue)) {
+                    return srcValue;
+                }
+            });
+        }
+        return this;
+    }
 }
diff --git a/src/cli/plugins/typescript/index.ts b/src/cli/plugins/typescript/index.ts
index b8d940b..619a69b 100644
--- a/src/cli/plugins/typescript/index.ts
+++ b/src/cli/plugins/typescript/index.ts
@@ -2,6 +2,8 @@ import {Configuration as RspackConfig} from "@rspack/core";
 
 import {definePlugin} from "@main/plugin";
 
+import {ConfigBuilder} from "@cli/builders/typescript";
+
 import TypescriptConfig from "./TypescriptConfig";
 
 import {TransportDeclaration, TransportDeclarationLayer, VendorDeclaration} from "./declaration";
@@ -15,7 +17,16 @@ export default definePlugin(() => {
     return {
         name: "adnbn:typescript",
         startup: ({config}) => {
-            typescript = TypescriptConfig.make(config);
+            const {tsConfig} = config;
+            const configBuilder = ConfigBuilder.from();
+
+            if (typeof tsConfig === "function") {
+                tsConfig(configBuilder);
+            } else if (typeof tsConfig === "object") {
+                configBuilder.raw(tsConfig);
+            }
+
+            typescript = new TypescriptConfig(config).merge(configBuilder.get()).build();
 
             VendorDeclaration.make(config);
         },
diff --git a/src/cli/resolvers/config.ts b/src/cli/resolvers/config.ts
index d2800b7..555b4ac 100644
--- a/src/cli/resolvers/config.ts
+++ b/src/cli/resolvers/config.ts
@@ -196,6 +196,7 @@ export default async (config: OptionalConfig): Promise<Config> => {
         env = {},
         manifest,
         manifestVersion = (new Set<Browser>([Browser.Safari]).has(browser) ? 2 : 3) as ManifestVersion,
+        tsConfig,
         mode = Mode.Development,
         analyze = false,
         plugins = [],
@@ -250,6 +251,7 @@ export default async (config: OptionalConfig): Promise<Config> => {
         specific,
         manifest,
         manifestVersion,
+        tsConfig,
         rootDir,
         outDir,
         srcDir,
diff --git a/src/types/config.ts b/src/types/config.ts
index ada3e2a..0e566b9 100644
--- a/src/types/config.ts
+++ b/src/types/config.ts
@@ -1,5 +1,6 @@
 import type {Configuration as RspackConfig, Filename} from "@rspack/core";
 import type {Options as HtmlOptions} from "html-rspack-tags-plugin";
+import type {TsConfigJson} from "type-fest";
 
 import {Command, Mode} from "@typing/app";
 import {Browser, BrowserSpecific} from "@typing/browser";
@@ -7,6 +8,7 @@ import {ManifestIncognitoValue, ManifestVersion, ManifestBuilder, OptionalManife
 import {Plugin} from "@typing/plugin";
 import {Language} from "@typing/locale";
 import {Awaiter} from "@typing/helpers";
+import {TsConfigBuilder} from "@typing/typescript";
 import {EnvFilterOptions, EnvFilterVariant} from "@typing/env";
 
 /**
@@ -191,6 +193,11 @@ export interface Config {
      */
     manifestVersion: ManifestVersion;
 
+    /**
+     * TypeScript configuration for the project. This is the parsed tsconfig.json content.
+     */
+    tsConfig?: TsConfigJson | ((builder: TsConfigBuilder) => void);
+
     /**
      * Default locale for the extension.
      * @example "en"
diff --git a/src/types/typescript.ts b/src/types/typescript.ts
new file mode 100644
index 0000000..8d0b35e
--- /dev/null
+++ b/src/types/typescript.ts
@@ -0,0 +1,29 @@
+import type {Get, PartialDeep, TsConfigJson} from "type-fest";
+
+export type DotPath<T> = T extends object
+    ? {
+          [K in Extract<keyof T, string>]: NonNullable<T[K]> extends object
+              ? K | `${K}.${DotPath<NonNullable<T[K]>>}`
+              : K;
+      }[Extract<keyof T, string>]
+    : never;
+
+export type PathValue<T, P extends string> = Get<T, P>;
+
+export interface TsConfigBuilder {
+    get<P extends DotPath<TsConfigJson>>(path: P): PathValue<TsConfigJson, P> | undefined;
+
+    get(): TsConfigJson;
+
+    set<P extends DotPath<TsConfigJson>>(path: P, value: PathValue<TsConfigJson, P>): this;
+
+    has(path: DotPath<TsConfigJson>): boolean;
+
+    delete(path: DotPath<TsConfigJson>): this;
+
+    merge(config: PartialDeep<TsConfigJson>): this;
+
+    raw(config: PartialDeep<TsConfigJson>): this;
+
+    toJSON(): string;
+}