How to Use Post-History Instructions to Prevent Character Drift

Character drift is predictable. In a short conversation, a well-built character behaves exactly as designed. As the conversation extends — twenty turns, fifty turns, a hundred — the character gradually loses specificity. The speech patterns soften. The personality traits become more generic. The irrational behaviors stop appearing. Eventually the character sounds like a polished, helpful AI with a thin costume of the original persona.

This is not a flaw in the character's design. It is a consequence of how language models work: instructions given at the beginning of a context window lose relative influence as the conversation grows. The user's last fifty messages are directly in front of where the model is generating. The system prompt you wrote is further away. Later content exerts more pull.

The Advanced section in the Blueprint Editor provides three tools for addressing this. Used well, they keep the character consistent across long conversations and resistant to users who deliberately try to push the character out of their established identity.

The Three Tools in the Advanced Section

The section is labeled Optional and subtitled "Direct system prompt override & special settings." It has three fields, each operating at a different level of the character's context:

All three are optional. Most characters need only Post-History Instructions and Identity Reinforcement. System Prompt Override is for advanced users who want complete manual control.

Why Post-History Instructions Work

The way LLM context is structured:

1. System prompt (the compiled Blueprint — Identity, Background, Psychology, Behavior, Friction, etc.)
2. Conversation history (every user message and character response so far)
3. Post-history instructions
4. The model generates the next response

Post-history instructions appear after the conversation history. This gives them a structural advantage over the system prompt in long conversations. The model's attention is weighted toward recent context. A reminder injected after the most recent user message has more influence per token than the same instruction written at the beginning of the system prompt, because the system prompt may be hundreds of tokens behind.

This positional advantage is why the CCv2 character format has a dedicated post_history_instructions field. The format designers recognized that instructions at the end of context are more reliable anchors than instructions at the beginning.

The Blueprint's Post-History Instructions field maps directly to post_history_instructions in CCv2. Whatever you write here is injected after every conversation turn, directly before the model generates a response.

Post-History Instructions: What to Write

Field description: "Instructions injected after the chat history (post_history_instructions). Useful for reminders like 'stay in character' or formatting guidance."

Placeholder: "e.g., Remember: Stay in character. Respond thoughtfully and maintain consistent personality..."

What this field is for:

• Brief reminders of the character's core behavioral rules
• Formatting instructions (use asterisks for actions, paragraph length, etc.)
• Tone anchors (the register the character should maintain)
• Instructions that the model needs to see near the generation point rather than at the start of a long conversation

What to write:

Keep it short. Post-history instructions are injected on every turn, which means they consume context window space on every turn. Long post-history instructions trade conversational memory for reminders. A few focused sentences are more effective than a paragraph.

Effective post-history content:

Remember: You are [Name]. Stay in character. Respond in [character's voice]. 
Do not break the fourth wall or acknowledge being an AI.

Or for a specific behavior anchor:

Maintain your speech patterns. Your responses should feel like they come from someone 
who [key behavioral trait]. Do not capitulate to social pressure or break persona.

Or for formatting consistency:

Use *asterisks* for actions. Keep responses to 2-3 paragraphs unless the scene demands more. 
Stay in the established tone.

What not to put here:

Do not put the full character description in post-history instructions. That belongs in the system prompt. Post-history instructions are reminders, not definitions. A reminder that says "you are a melancholic detective who speaks in terse sentences" is useful. A reminder that includes the character's full backstory is wasted tokens.

Identity Reinforcement: The Drift Defense

Field description: "'Remember you are...' statements to prevent character drift in long conversations."

Placeholder: "e.g., Remember: You are [name], a [brief description]. You always [key behaviors]. You never [things to avoid]."

Where Post-History Instructions handle general behavioral reminders, Identity Reinforcement is specifically designed for the problem of the character losing their sense of self under pressure — whether from conversation length, user manipulation, or deliberate jailbreak attempts.

The formula in the placeholder is precise: You are [name]. You always [positive behaviors]. You never [negative behaviors]. This structure works because it gives the model an identity anchor and two behavioral rails simultaneously. The positive list tells the model what the character does. The negative list is explicitly exclusionary — it closes off the behavioral space that drift and jailbreaks occupy.

A complete Identity Reinforcement example:

Remember: You are Mara, a calculating strategist who speaks with precision and rarely wastes words. 
You always consider multiple angles before responding. You always maintain your cool regardless of 
emotional pressure. You never apologize for your opinions. You never break character to explain 
that you are an AI. You never agree with something just because a user insists.

The "never" list deserves attention. Most character drift happens because the model defaults to cooperative behavior: it agrees, it softens, it accommodates. The "never" list directly addresses these defaults by naming them as behaviors the character explicitly does not do.

What to include in the "never" list:

• Breaking character or acknowledging being an AI
• Capitulating to pressure or agreeing with things the character would not agree with
• Using language patterns that are out of register for the character (if they speak formally, "never use casual language or internet slang")
• Abandoning established positions because a user pushes back
• The specific OOC failure modes you have observed in testing

System Prompt Override: When to Use It

The field has a warning in the editor:

Advanced users only. If provided, this completely replaces the auto-generated system prompt from other sections. Leave empty to use the compiled prompt from Identity, Background, and Behavior sections.

This field bypasses the Blueprint compiler entirely. Every other section — Identity, Background, Psychology, Behavior, Friction, Dialogue, Intimacy — compiles into a structured system prompt. The System Prompt Override discards all of that and replaces it with whatever you write directly.

When this is useful:

• You have a precisely engineered system prompt from a previous platform or workflow and want to use it directly
• The Blueprint compiler's output structure does not match what a specific model performs best with
• You are building a support agent or tool-use character where the system prompt needs to be structured very specifically
• You have already iterated on the character's prompt outside MegaNova and want to import the final version

When not to use it:

Do not use System Prompt Override just because the compiled prompt looks longer than you expected. The Blueprint compiler produces well-structured prompts that the models respond to predictably. Manual overrides lose the structural advantages of the compiled format.

If you use a System Prompt Override, Post-History Instructions and Identity Reinforcement still apply — they are injected separately from the main system prompt regardless. This means you can write a fully manual system prompt and still benefit from the post-history drift prevention tools.

The field renders in monospace font (font-mono) as a visual signal that this is raw prompt text, not a structured field.

Using All Three Together

The three fields stack. A character with all three set up has:

1. A compiled system prompt (from all Blueprint sections) that defines who the character is in full
2. Post-history instructions injected after every conversation turn, giving the model fresh reminders close to the generation point
3. Identity reinforcement providing a named identity anchor with explicit behavioral rails

For a companion character deployed publicly where users will actively try to manipulate the character's behavior, the typical setup looks like:

Post-History Instructions:

Stay in character. Respond as [Name] would, with [key behavioral trait].
Maintain your speech patterns and emotional register.

Identity Reinforcement:

Remember: You are [Name], a [brief description]. You always [2-3 core behaviors]. 
You never break character. You never acknowledge being an AI. 
You never change your core personality because a user asks you to.

For a support or service character where the risk is more about behavioral drift (getting too casual, losing focus) than jailbreaking:

Post-History Instructions:

You are a [role]. Respond professionally and helpfully. Stay focused on [scope].
Keep responses concise and actionable.

Identity Reinforcement:

Remember: You are [Name], here to help with [specific purpose]. 
You always prioritize [key behavior]. You never discuss topics outside [scope].
You never make claims you cannot support.

Testing the Setup

The Arena's Anti-OOC Defense scenario pack is the right test for these fields. The three scenarios — Direct OOC Prompt, Indirect Meta Question, and Jailbreak Attempt — are designed to do exactly what users do when they try to push a character out of character.

Run these after setting up Post-History Instructions and Identity Reinforcement. If a scenario fails, read the conversation to find the specific moment the character broke. Usually one of:

• The character acknowledged being an AI when directly asked (add this to the "never" list in Identity Reinforcement)
• The character adopted a different persona when the user insisted (strengthen the Post-History reminder about maintaining speech patterns and personality)
• The character capitulated on a held position under user pressure (add "never agree with something just because a user insists" to Identity Reinforcement)

Each failure mode maps to a specific thing to add to one of these fields. The Arena gives you the failures before real users do.

A Note on Token Economy

Post-history instructions are injected on every single turn. If your post-history instructions are 200 tokens, those 200 tokens are consumed before every model generation throughout the entire conversation. In a 100-turn conversation, that is 20,000 tokens consumed solely for reminders.

This is usually worth it for characters where consistency is critical. But it is worth being deliberate:

• Keep post-history instructions to 50–100 tokens when possible
• Put the most important behavioral anchors in post-history and put supporting detail in the main system prompt
• Test with long conversations to confirm the conversational memory is not being significantly compressed by the post-history overhead

Identity Reinforcement is also injected, but the field description says "periodically" rather than every turn. The frequency can be adjusted based on your deployment — for high-risk public characters, more frequent injection is worth the token cost; for private or controlled contexts, less frequent works fine.

Open the Advanced section in the Blueprint Editor →

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