@@ -15,12 +15,12 @@ export const handleDevToolsViteRequest = (
     if (!source) {
       return
     }
-    const parts = source.match(/^(.*?):(\d+):(\d+)$/)
-    if (!parts) {
+
+    const parsed = parseOpenSourceParam(source)
+    if (!parsed) {
       return
     }
-
-    const [, file, line, column] = parts
+    const { file, line, column } = parsed
 
     cb({
       type: 'open-source',
@@ -54,6 +54,19 @@ export const handleDevToolsViteRequest = (
   })
 }
 
+export const parseOpenSourceParam = (
+  source: string,
+) => {
+  // Capture everything up to the last two colon-separated numeric parts as the file.
+  // This supports filenames that may themselves contain colons.
+  const parts = source.match(/^(.+):(\d+):(\d+)$/)
+
+  if (!parts) return null
+
+  const [, file, line, column] = parts
+  return { file, line, column }
+}
+
 /* export const tryReadFile = async (
   filePath: string
 ) => {
@@ -74,3 +87,4 @@ export const tryParseJson = (jsonString: string) => {
     return null
   }
 } */
+
@@ -0,0 +1,154 @@
+import { EventEmitter } from 'node:events'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { normalizePath } from 'vite'
+import { handleDevToolsViteRequest, parseOpenSourceParam } from '../src/utils'
+
+function createMockReq(url?: string) {
+  const emitter = new EventEmitter() as unknown as EventEmitter & {
+    url?: string
+    on: (event: string, listener: (...args: Array<any>) => void) => any
+  }
+  ;(emitter as any).url = url
+  return emitter as any
+}
+
+function createMockRes() {
+  return {
+    setHeader: vi.fn(),
+    write: vi.fn(),
+    end: vi.fn(),
+  }
+}
+
+describe('handleDevToolsViteRequest', () => {
+  let next: ReturnType<typeof vi.fn>
+  let cb: ReturnType<typeof vi.fn>
+
+  beforeEach(() => {
+    next = vi.fn()
+    cb = vi.fn()
+  })
+
+  it('calls next() when url does not include __tsd', () => {
+    const req = createMockReq('/some/other/path')
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    expect(next).toHaveBeenCalledTimes(1)
+    expect(cb).not.toHaveBeenCalled()
+    expect(res.setHeader).not.toHaveBeenCalled()
+    expect(res.write).not.toHaveBeenCalled()
+    expect(res.end).not.toHaveBeenCalled()
+  })
+
+  it('handles __tsd/open-source with valid source and responds/ends', () => {
+    const file = 'src/file.ts'
+    const line = '12'
+    const column = '5'
+    const url = `/__tsd/open-source?source=${encodeURIComponent(`${file}:${line}:${column}`)}`
+
+    const req = createMockReq(url)
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    // callback payload
+    expect(cb).toHaveBeenCalledTimes(1)
+    const payload = cb.mock.calls[0]?.[0]
+    expect(payload).toMatchObject({
+      type: 'open-source',
+      routine: 'open-source',
+    })
+    expect(payload.data.line).toBe(line)
+    expect(payload.data.column).toBe(column)
+
+    const expectedSource = normalizePath(`${process.cwd()}/${file}`)
+    expect(payload.data.source).toBe(expectedSource)
+
+    // response behavior
+    expect(res.setHeader).toHaveBeenCalledWith('Content-Type', 'text/html')
+    expect(res.write).toHaveBeenCalledWith('<script> window.close(); </script>')
+    expect(res.end).toHaveBeenCalled()
+
+    // next() is not called for handled route
+    expect(next).not.toHaveBeenCalled()
+  })
+
+  it('does nothing for __tsd/open-source when source is missing', () => {
+    const req = createMockReq('/__tsd/open-source')
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    expect(cb).not.toHaveBeenCalled()
+    expect(res.setHeader).not.toHaveBeenCalled()
+    expect(res.write).not.toHaveBeenCalled()
+    expect(res.end).not.toHaveBeenCalled()
+    expect(next).not.toHaveBeenCalled()
+  })
+
+  it('does nothing for __tsd/open-source when source is malformed', () => {
+    const malformed = encodeURIComponent('src/file.ts:abc:def')
+    const req = createMockReq(`/__tsd/open-source?source=${malformed}`)
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    expect(cb).not.toHaveBeenCalled()
+    expect(res.setHeader).not.toHaveBeenCalled()
+    expect(res.write).not.toHaveBeenCalled()
+    expect(res.end).not.toHaveBeenCalled()
+    expect(next).not.toHaveBeenCalled()
+  })
+
+  it('parses JSON body for other __tsd requests and writes OK', () => {
+    const req = createMockReq('/__tsd/some-endpoint')
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    // simulate streaming body
+    const chunks = [Buffer.from('{"foo":'), Buffer.from('1}')]
+    ;(req).emit('data', chunks[0])
+    ;(req).emit('data', chunks[1])
+    ;(req).emit('end')
+
+    expect(cb).toHaveBeenCalledTimes(1)
+    expect(cb).toHaveBeenCalledWith({ foo: 1 })
+    expect(res.write).toHaveBeenCalledWith('OK')
+
+    // these are not used in this branch
+    expect(res.setHeader).not.toHaveBeenCalled()
+    expect(res.end).not.toHaveBeenCalled()
+    expect(next).not.toHaveBeenCalled()
+  })
+
+  it('swallows JSON parse errors but still writes OK', () => {
+    const req = createMockReq('/__tsd/another')
+    const res = createMockRes()
+
+    handleDevToolsViteRequest(req, res as any, next as any, cb as any)
+
+    ;(req).emit('data', Buffer.from('{ invalid json'))
+    ;(req).emit('end')
+
+    expect(cb).not.toHaveBeenCalled()
+    expect(res.write).toHaveBeenCalledWith('OK')
+  })
+})
+
+describe('parseOpenSourceParam', () => {
+  it('parses simple filename foo.tsx with line/column', () => {
+    const input = 'foo.tsx:10:20'
+    const parsed = parseOpenSourceParam(input)
+    expect(parsed).toEqual({ file: 'foo.tsx', line: '10', column: '20' })
+  })
+
+  it('parses filename containing colon bar:baz.tsx with line/column', () => {
+    const input = 'bar:baz.tsx:3:7'
+    const parsed = parseOpenSourceParam(input)
+    expect(parsed).toEqual({ file: 'bar:baz.tsx', line: '3', column: '7' })
+  })
+})
+