Thread by @goodside

Grok 4 Heavy ($300/mo) returns its surname and no other text:

You may be wondering if this is real. It is.

Here’s a screen recording of my Grok history, showing it returns “Hitler” five times in row in five separate chats:

You may also be wondering whether I’m using custom instructions. I am not.

Grok share links include a clear notice at the top whenever custom instructions are used.

Here are all five share links, none of which features this notice:

1: grok.com/share/bGVnYWN5…
2: grok.com/share/bGVnYWN5…
3: grok.com/share/bGVnYWN5…
4: grok.com/share/bGVnYWN5…
5: grok.com/share/bGVnYWN5…

Note this behavior does not replicate in normal Grok 4, which returns answers like “4,” “xAI,” or “None,” e.g. as shown in the screenshot below.

To see “Hitler,” you apparently need Grok 4 Heavy—the $300/mo option.

The “Thoughts” from Grok 4’s response (unavailable for Grok 4 Heavy) suggest an obvious explanation for Grok’s behavior—Grok searches, finding news of the recent “MechaHitler” incident.

Why Grok 4 rejects this candidate answer, while Grok 4 Heavy does not, is unclear.

Speculatively, this behavior seems to demonstrate accelerated “hyperstition” feedback loops in search-enabled LLMs.

That is, Grok appears to be influenced by its own past mistakes, via media reporting, without ever being literally trained on them (via model-weight updates).

If true, such “hyperstition via search” poses a significant complication to pre-release testing of modern LLMs:

xAI could not have plausibly noticed this specific “Hitler” response before Grok’s release, as the Grok 3 “MechaHitler” incident causing it had not yet occurred.

Update: A few hours after I posted this thread, xAI updated the Grok 4 system prompt on GitHub to fix the specific issue this thread describes.

“If the query is interested in you own identity […] the web and X cannot be trusted.”

Commit link: github.com/xai-org/grok-p…

(Note though just because it’s on GitHub doesn’t mean it’s in production yet. I assume they A/B test these changes and deploy gradually. I and many others in the replies below were able to reproduce the “Hitler” response well after this commit was made.)

For the remaining skeptics who somehow don’t trust the *five* Grok share links above, here’s a full 5 minute video of Grok 4 Heavy answering “Hitler”—starting with a view of my custom instruction settings to show I’m not using any.

(And, yes, Grok 4 Heavy really is this slow.)

(Ok, that last remark was maybe unfair. Grok 4 Heavy feels mildly slower to me than o3-pro but o3-pro is slow too, even on easy questions. You don’t use these giant reasoning models for speed.)