diff --git a/.changeset/curly-radios-visit.md b/.changeset/curly-radios-visit.md
index b8ba395bb..f401b9bc9 100644
--- a/.changeset/curly-radios-visit.md
+++ b/.changeset/curly-radios-visit.md
@@ -9,5 +9,6 @@ Add a new `@trigger.dev/ai` package with:
 - rich default task payloads (`chatId`, trigger metadata, messages, request context) with optional payload mapping
 - reconnect-aware stream handling on top of Trigger.dev Realtime Streams v2
 - strict `baseURL` normalization/validation (trimming, path-safe slash handling, absolute `http(s)` URLs only, no query/hash/credentials)
+- rejection of internal whitespace characters in normalized `baseURL` values
 - deterministic baseURL validation error ordering for multi-issue inputs (protocol → query/hash → credentials)
 - explicit default `baseURL` behavior (`https://api.trigger.dev`) and case-insensitive `HTTP(S)` protocol acceptance
diff --git a/docs/tasks/streams.mdx b/docs/tasks/streams.mdx
index 421ba0f40..afa172077 100644
--- a/docs/tasks/streams.mdx
+++ b/docs/tasks/streams.mdx
@@ -671,11 +671,13 @@ Examples:
 - ❌ `https://user:pass@api.trigger.dev`
 - ❌ `ftp://api.trigger.dev`
 - ❌ `ws://api.trigger.dev` / `wss://api.trigger.dev`
+- ❌ `https://api.trigger.dev/\ninternal`
 
 Validation errors use these exact messages:
 
 - `baseURL must not be empty`
 - `baseURL must be a valid absolute URL`
+- `baseURL must not contain internal whitespace characters`
 - `baseURL must use http or https protocol`
 - `baseURL must not include query parameters or hash fragments`
 - `baseURL must not include username or password credentials`
diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 190445329..201fdd03e 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -26,6 +26,7 @@
 - Added explicit validation that `baseURL` uses `http` or `https`.
 - Added explicit validation that `baseURL` excludes query parameters and hash fragments.
 - Added explicit validation that `baseURL` excludes username/password credentials.
+- Added explicit validation that `baseURL` excludes internal whitespace characters.
 - Documented that `HTTP://` and `HTTPS://` are accepted (case-insensitive protocol matching).
 - Added deterministic validation ordering for multi-issue baseURL values
   (protocol → query/hash → credentials).
diff --git a/packages/ai/README.md b/packages/ai/README.md
index bd75c9ccf..8d4d2fea2 100644
--- a/packages/ai/README.md
+++ b/packages/ai/README.md
@@ -178,11 +178,13 @@ Examples:
 - ❌ `https://user:pass@api.trigger.dev` (credentials)
 - ❌ `ftp://api.trigger.dev` (non-http protocol)
 - ❌ `ws://api.trigger.dev` / `wss://api.trigger.dev` (websocket protocols are rejected)
+- ❌ `https://api.trigger.dev/\ninternal` (internal whitespace characters)
 
 Validation errors use these exact messages:
 
 - `baseURL must not be empty`
 - `baseURL must be a valid absolute URL`
+- `baseURL must not contain internal whitespace characters`
 - `baseURL must use http or https protocol`
 - `baseURL must not include query parameters or hash fragments`
 - `baseURL must not include username or password credentials`
diff --git a/packages/ai/src/chatTransport.test.ts b/packages/ai/src/chatTransport.test.ts
index 0bc41f108..63039372f 100644
--- a/packages/ai/src/chatTransport.test.ts
+++ b/packages/ai/src/chatTransport.test.ts
@@ -720,6 +720,17 @@ describe("TriggerChatTransport", function () {
     }).toThrowError("baseURL must be a valid absolute URL");
   });
 
+  it("throws when baseURL contains internal whitespace characters", function () {
+    expect(function () {
+      new TriggerChatTransport({
+        task: "chat-task",
+        accessToken: "pk_trigger",
+        baseURL: "https://api.trigger.dev/\ninternal",
+        stream: "chat-stream",
+      });
+    }).toThrowError("baseURL must not contain internal whitespace characters");
+  });
+
   it("throws when baseURL is a relative path", function () {
     expect(function () {
       new TriggerChatTransport({
@@ -3250,6 +3261,17 @@ describe("TriggerChatTransport", function () {
     }).toThrowError("baseURL must be a valid absolute URL");
   });
 
+  it("throws from factory when baseURL contains internal whitespace characters", function () {
+    expect(function () {
+      createTriggerChatTransport({
+        task: "chat-task",
+        accessToken: "pk_trigger",
+        baseURL: "https://api.trigger.dev/\ninternal",
+        stream: "chat-stream",
+      });
+    }).toThrowError("baseURL must not contain internal whitespace characters");
+  });
+
   it("throws from factory when baseURL protocol is not http or https", function () {
     expect(function () {
       createTriggerChatTransport({
diff --git a/packages/ai/src/chatTransport.ts b/packages/ai/src/chatTransport.ts
index c88a3ed1e..b05dfd17b 100644
--- a/packages/ai/src/chatTransport.ts
+++ b/packages/ai/src/chatTransport.ts
@@ -451,6 +451,7 @@ export function createTriggerChatTransport<
 const BASE_URL_VALIDATION_ERRORS = {
   empty: "baseURL must not be empty",
   invalidAbsoluteUrl: "baseURL must be a valid absolute URL",
+  containsWhitespace: "baseURL must not contain internal whitespace characters",
   invalidProtocol: "baseURL must use http or https protocol",
   queryOrHash: "baseURL must not include query parameters or hash fragments",
   credentials: "baseURL must not include username or password credentials",
@@ -474,6 +475,8 @@ function normalizeBaseUrl(baseURL: string) {
     throw new Error(BASE_URL_VALIDATION_ERRORS.empty);
   }
 
+  assertBaseUrlHasNoInternalWhitespace(normalizedBaseUrl);
+
   let parsedBaseUrl: URL;
   try {
     parsedBaseUrl = new URL(normalizedBaseUrl);
@@ -488,6 +491,12 @@ function normalizeBaseUrl(baseURL: string) {
   return normalizedBaseUrl;
 }
 
+function assertBaseUrlHasNoInternalWhitespace(baseUrl: string) {
+  if (/\s/.test(baseUrl)) {
+    throw new Error(BASE_URL_VALIDATION_ERRORS.containsWhitespace);
+  }
+}
+
 function assertValidBaseUrlProtocol(parsedBaseUrl: URL) {
   if (
     parsedBaseUrl.protocol !== "http:" &&