diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000000..a23f313eff
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,7 @@
+## 2026-05-25 - Harden sanitizeRelativePath
+
+**Context**: Identified a directory traversal vulnerability in `sanitizeRelativePath` (`packages/cli-kit/src/public/node/path.ts`) where absolute paths and Windows drive letters were not stripped, potentially allowing escapes when joined.
+
+**Action**: Hardened `sanitizeRelativePath` to strip empty segments (leading/multiple slashes) and Windows drive letters. Updated JSDoc and the warning message to reflect these changes.
+
+**Learning**: When sanitizing paths intended to be relative, always strip leading slashes and platform-specific root markers (like drive letters) to prevent absolute path escapes.
diff --git a/packages/cli-kit/src/public/node/path.test.ts b/packages/cli-kit/src/public/node/path.test.ts
index 4972b3ac27..767ac47979 100644
--- a/packages/cli-kit/src/public/node/path.test.ts
+++ b/packages/cli-kit/src/public/node/path.test.ts
@@ -1,5 +1,5 @@
-import {relativizePath, normalizePath, cwd, sniffForPath, commonParentDirectory} from './path.js'
-import {describe, test, expect} from 'vitest'
+import {relativizePath, normalizePath, cwd, sniffForPath, commonParentDirectory, sanitizeRelativePath} from './path.js'
+import {describe, test, expect, vi} from 'vitest'
 
 describe('relativize', () => {
   test('relativizes the path', () => {
@@ -93,3 +93,46 @@ describe('sniffForPath', () => {
     expect(path).toStrictEqual('/path/to/project')
   })
 })
+
+describe('sanitizeRelativePath', () => {
+  test('strips traversal segments', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('../../etc/passwd', warn)).toBe('etc/passwd')
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining('contains traversal or absolute segments'))
+  })
+
+  test('strips leading slashes (absolute Unix paths)', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('/etc/passwd', warn)).toBe('etc/passwd')
+  })
+
+  test('strips multiple leading slashes', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('//etc/passwd', warn)).toBe('etc/passwd')
+  })
+
+  test('strips Windows drive letters', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('C:/Windows/System32', warn)).toBe('Windows/System32')
+  })
+
+  test('handles Windows backslashes', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('..\\..\\etc\\passwd', warn)).toBe('etc/passwd')
+  })
+
+  test('collapses internal current directory markers', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('foo/./bar', warn)).toBe('foo/bar')
+  })
+
+  test('returns empty string for empty result', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('../..', warn)).toBe('')
+  })
+
+  test('returns empty string for single slash', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('/', warn)).toBe('')
+  })
+})
diff --git a/packages/cli-kit/src/public/node/path.ts b/packages/cli-kit/src/public/node/path.ts
index f372178011..93349a5995 100644
--- a/packages/cli-kit/src/public/node/path.ts
+++ b/packages/cli-kit/src/public/node/path.ts
@@ -224,13 +224,20 @@ export function sanitizeRelativePath(input: string, warn: (msg: string) => void)
     if (seg === '..') {
       stripped = true
       stack.pop()
-    } else if (seg !== '.') {
+    } else if (seg === '.' || seg === '') {
+      // Skip empty segments (leading/multiple slashes) and current directory markers.
+      // This prevents absolute paths like '/etc/passwd' from being treated as such.
+      if (seg === '') stripped = true
+    } else if (/^[a-zA-Z]:$/.test(seg)) {
+      // Skip Windows drive letters (e.g. 'C:') to prevent escaping to other drives.
+      stripped = true
+    } else {
       stack.push(seg)
     }
   }
   const result = stack.join('/')
   if (stripped) {
-    warn(`Warning: path '${input}' contains '..' traversal — sanitized to '${result || '.'}'\n`)
+    warn(`Warning: path '${input}' contains traversal or absolute segments — sanitized to '${result || '.'}'\n`)
   }
   return result
 }