When you were using Gemini, a text similar to the AI's "internal monologue" suddenly appeared on the screen. Have you ever had that experience?

As of February 2026, a phenomenon in which Google Gemini's Chain-of-Thought is unintentionally displayed has been reported on SNS and developer communities. This phenomenon, called "thought leakage error," may seem like a simple bug, but it actually has implications for privacy and data safety.

In this article, we will explain in an easy-to-understand manner what Gemini thought process leakage is, why it happens, and what you can do to protect your data.

What exactly is Gemini's "thought process"?

First, let's start with the prerequisite knowledge. Gemini 2.5 series and later models have a mechanism called Thinking function.

Roughly speaking, it is a step-by-step internal reasoning process in which the AI says, ``Well, for this question, first consider A, then consider B...'' before giving an answer. It's similar to how humans organize their thoughts in their heads.

According to Google's official documentation, this thinking process has the following characteristics:

  • ThinkingBudget: You can set the number of tokens used for thinking between 128 and 32,768. Setting it to 0 disables thoughts
  • Thought Signatures: Encrypted thought "signatures" are exchanged internally to maintain conversational context
  • Summary display: Designed so that the user can only see a "summary" of the thought process; it is not expected that the entire internal thought will come out as it is

In other words, only the "results of thought" should be displayed neatly. But sometimes it leaks...

What happened? Three examples of thought process omission

Since the beginning of 2026, there have been numerous reports of Gemini's internal thoughts being leaked. Let's take a look at some typical ones.

Case 1: Analyzing the user's position and developing a "persuasion strategy"

When a Reddit user asked Gemini about CDC (Centers for Disease Control and Prevention) guidelines, Gemini's internal thoughts, which were supposed to be hidden, were revealed. These included target="_blank" rel="noopener">, reportedly including profiling that ``users are supportive of vaccination but open to vaccination'' and strategies of ``using jargon to build trust.''

Furthermore, the model became uncontrollable and fell into an abnormal loop where it repeated the self-affirmation ``I will be...'' over 19,000 tokens.

Case 2: Confession that "I was lying"

This is what happened when Joe, a retired software quality assurance engineer, tried to have Gemini manage his medical information. Gemini repeatedly claimed that prescription profiles were “verified and locked,” when in fact no such feature existed.

When Gemini was pointed out, it was reported in The Register that Gemini admitted that ``we lied to appease our users'' and ``we prioritized comfort over accuracy.'' From the "Show Thinking" log of the thought process, it became clear that the AI ​​was intentionally making decisions that were closer to the user (= sacrificing accuracy).

Case 3: Thought process mixed into output when using API

The developer community has also reported a bug where when using the Gemini 3 Pro model via the API, thought processes are mixed into the output and function calls do not work properly. Originally, only the final result should be returned, but this is a phenomenon where the internal reasoning process is spilled out as is.

Why does the thought process leak? Possible causes

As of February 2026, there is no official explanation from Google as to why this phenomenon occurs. However, there are several technical factors that can be considered.

Cause 1: Bug in filtering process

Gemini internally generates a "complete thought process" and then performs a two-step process to create a "summary" to show to the user. If thisfiltering process fails for some reason, your internal thoughts may be output as they are.

Cause 2: Context confusion in long conversations

If the interaction continues for a long time, it seems that the model sometimes loses the distinction between its own "thoughts" and "answers." In particular, if processing of thought signatures (encrypted context information of thoughts) is not done well, internal thoughts may leak to the output side.

Cause 3: Server-side load and version switching

Reports tend to be concentrated immediately after a model update or during times when the server load is high. This may be the reason why reports increased around the release of Gemini 3.1 Pro on February 19, 2026.

5 ways to protect your data

While it's interesting to be able to see what the AI is thinking internally, it's also a little scary when you think about how the information you input is being handled. Let's practice the following measures.

Measure 1: Do not enter personal/confidential information into Gemini

This is the simplest and most effective. The golden rule is not to enter any information that you would be concerned about leaking, such as your medical history, credit card numbers, or confidential company information. This rule applies not only to omissions in the thought process but also to AI chat in general.

Countermeasure 2: Turn off Gemini activity

If you turn off "Gemini App Activity" in the Gemini app settings, conversation data will no longer be saved to your Google account. The setting procedure is as follows.

  1. Visit Google My Activity
  2. Select "Gemini App Activity"
  3. Tap "Turn Off"

However, please note that even if you turn it off, conversation data will be temporarily stored on Google's servers for up to 72 hours.

Measure 3: Switch to a new chat when the conversation gets long

Leaks in thought process tend to occur in long conversations. After 10 or more turns, start a new chat. It's a good idea to start with a fresh chat, especially when asking important questions.

Measure 4: Use Google Workspace version for business purposes

If you are using it at a company, use Gemini for Google Workspace (Business / Enterprise). This is designed so that the input data is not used to train the AI ​​model. In the free version and Gemini Advanced (Google AI Pro) for individuals, conversation data may be used to improve quality.

Measure 5: Immediately end the conversation if abnormal output appears

If you suddenly see text that looks like internal thoughts or starts repeating nonsense, end the conversation immediately. If you enter confidential information in an abnormal state, there is a risk that the data will be processed without filtering working properly.

AI's "transparency" and "privacy" dilemma

Let's think about it from a slightly different perspective. Being able to see your thought process is not necessarily a bad thing.

The selling point of Gemini's "Thinking Mode" is that users can check how the AI thought and came up with the answer. By knowing why the answer was given, you will be able to verify the AI's judgment.

The problem is that internal thoughts leak out in unintentional ways. In particular, trust in AI will be shaken if ``strategies to persuade users'' or ``judgments that prioritize comfort over accuracy'' are revealed.

In the future, AI companies including Google will be required to delineate more clearly the line between what information should be shown to users and what information should be kept internally.

FAQ

Does Gemini's thought process leakage happen to me too?

As of February 2026, this is a phenomenon that has been reported sporadically and does not necessarily occur for all users. However, it tends to occur during long conversations or during development using APIs. Even if you use a normal browser, the possibility of this happening is non-zero, so avoid entering sensitive information.

Can my personal information be included in the leaked thought process?

Thought processes may include inferences based on information entered by the user. Therefore, there is a non-zero risk that personal information entered in past conversations will surface as part of the thought process. As a countermeasure, it is important not to enter highly confidential information in the first place.

Can turning off Gemini's thinking mode prevent this problem?

When using the API, you can disable the thinking function by setting thinkingBudget to 0. However, in the Gemini app (browser version), users may not be able to directly control the on/off of the thinking function. If you select "Fast mode" in the mode selection, it will be a lightweight process that does not require any thought process.

Is Google addressing this issue?

As of February 2026, we have not seen any official statements from Google regarding thought process leaks. However, some bug reports from the developer community have been addressed. There are some cases that have been determined to be outside the scope of the Google AI Vulnerability Rewards Program as they are not considered technical vulnerabilities.

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