diff --git a/apps/sim/tools/request-transport.test.ts b/apps/sim/tools/request-transport.test.ts
index 49645c56935..0b27336edbd 100644
--- a/apps/sim/tools/request-transport.test.ts
+++ b/apps/sim/tools/request-transport.test.ts
@@ -32,6 +32,7 @@ const PROBE_FILE = {
   mimeType: 'text/plain',
   data: 'data:text/plain;base64,cHJvYmU=',
 } as const
+const DOT_SEGMENT_ERROR = 'Tool request URL cannot contain "." or ".." path segments'
 const EXCEL_MIME_TYPE = 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
 
 function createSchemaProbeParams(
@@ -79,6 +80,12 @@ function isAbsoluteHttpUrl(url: string): boolean {
   }
 }
 
+function hasDotDotPathSegment(url: string): boolean {
+  const pathStart = url.indexOf('/', url.indexOf('//') + 2)
+  if (pathStart === -1) return false
+  return url.slice(pathStart).split(/[?#]/)[0].split('/').includes('..')
+}
+
 function createRequestTool(
   url: string | ((params: Record<string, unknown>) => string)
 ): ToolConfig {
@@ -129,6 +136,40 @@ describe('external request transport', () => {
     ).toBe('https://example.com')
   })
 
+  it.each([
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/..',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/../../../v0/inboxes/other',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/.',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/%2e%2E',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/.%2e?force=true',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/.\t.',
+    'https://api.example.com/v0/inboxes/inbox_1\\drafts\\..',
+    'https://api.example.com/v0/inboxes/inbox_1/drafts/..\u0001',
+    ' https://api.example.com/v0/inboxes/inbox_1/drafts/..\u0000 ',
+  ])('rejects a URL whose path resolves a dot segment: %s', (url) => {
+    expect(() =>
+      prepareToolRequest(
+        createRequestTool(() => url),
+        {}
+      )
+    ).toThrow(DOT_SEGMENT_ERROR)
+  })
+
+  it.each([
+    'https://my-app.vercel.app/v1/domains/example.com',
+    'https://api.example.com/v1/files/..foo/foo../.env',
+    'https://api.example.com/v1/search?path=../x#..',
+    'https://api.example.com/',
+    'https://api.example.com/v1/files/..\u00a0',
+  ])('allows dots that are not whole path segments: %s', (url) => {
+    expect(
+      prepareToolRequest(
+        createRequestTool(() => url),
+        {}
+      ).url
+    ).toBe(url)
+  })
+
   it.each([
     ['http_request', requestTool, { url: '/api/auth/oauth/token', method: 'GET' }],
     ['webhook_request', webhookRequestTool, { url: '/api/auth/oauth/token', body: {} }],
@@ -188,12 +229,16 @@ describe('dynamic external request registry invariant', () => {
           isAbsoluteHttpUrl(url),
           `${toolId} resolved ${url} outside the external HTTP transport`
         ).toBe(true)
-        expect(() =>
+        const prepare = () =>
           prepareToolRequest(
             createRequestTool(() => url),
             {}
           )
-        ).not.toThrow()
+        if (hasDotDotPathSegment(url)) {
+          expect(prepare, `${toolId} dispatched ${url}`).toThrow(DOT_SEGMENT_ERROR)
+        } else {
+          expect(prepare, `${toolId} rejected ${url}`).not.toThrow()
+        }
       }
 
       if (observations.length === 0) continue
diff --git a/apps/sim/tools/request-transport.ts b/apps/sim/tools/request-transport.ts
index 9f52a09f4be..0dfb6543654 100644
--- a/apps/sim/tools/request-transport.ts
+++ b/apps/sim/tools/request-transport.ts
@@ -10,6 +10,7 @@ import {
   type ToolConfig,
   type ToolDefinition,
 } from '@/tools/types'
+import { assertNoDotPathSegments } from '@/tools/url-path'
 
 const MODEL_INPUT_PROJECTION_ERROR_MESSAGE = 'Model input could not be safely projected'
 const PRIVATE_MODEL_INPUT_EXTERNAL_URL_ERROR_MESSAGE =
@@ -232,6 +233,7 @@ function assertExternalRequestUrl(url: string): void {
   if (parsedUrl.protocol !== 'http:' && parsedUrl.protocol !== 'https:') {
     throw new Error(EXTERNAL_REQUEST_URL_ERROR_MESSAGE)
   }
+  assertNoDotPathSegments(url)
 }
 
 /** Materializes one external HTTP request after enforcing the model-input boundary. */
diff --git a/apps/sim/tools/url-path.ts b/apps/sim/tools/url-path.ts
index 83ef707172f..08bf1663c18 100644
--- a/apps/sim/tools/url-path.ts
+++ b/apps/sim/tools/url-path.ts
@@ -186,3 +186,29 @@ export function safeUrlPathSegment(value: string | number | bigint, paramName: s
 
   return encodeSegment(trimmed, paramName)
 }
+
+/** Matches a scheme and authority, which end at the first `/`, `\`, `?`, or `#` in a special-scheme URL. */
+const SCHEME_AND_AUTHORITY = /^[a-z][a-z\d+.-]*:[\\/]*[^\\/?#]*/i
+
+/**
+ * Rejects a request URL whose path carries a dot segment the WHATWG parser
+ * would resolve away. Mirrors the parser: boundary C0 controls and spaces,
+ * then tabs and newlines, are stripped, `\` separates segments like `/`, and
+ * `%2e` counts as a dot.
+ *
+ * @throws If the path contains a `.` or `..` segment in any spelling.
+ */
+export function assertNoDotPathSegments(url: string): void {
+  const path = url
+    .replace(/^[\u0000-\u0020]+|[\u0000-\u0020]+$/g, '')
+    .replace(/[\t\n\r]/g, '')
+    .replace(SCHEME_AND_AUTHORITY, '')
+    .split(/[?#]/, 1)[0]
+  const hasDotSegment = path.split(/[\\/]/).some((segment) => {
+    const decoded = segment.replace(/%2e/gi, '.')
+    return decoded === '.' || decoded === '..'
+  })
+  if (hasDotSegment) {
+    throw new Error('Tool request URL cannot contain "." or ".." path segments')
+  }
+}