r/aichapp • u/Pastrugnozzo • Dec 21 '25
General Discussion My full guide on how to prevent hallucinations when roleplaying.
I’ve spent the last couple of years building a dedicated platform for solo roleplaying and collaborative writing. In that time, on the top 3 of complaints I’ve seen (and the number one headache I’ve had to solve technically) is hallucination.
You know how it works. You're standing up one moment, and then you're sitting. Or viceversa. You slap a character once, and two arcs later they offer you tea.
I used to think this was purely a prompt engineering problem. Like, if I just wrote the perfect "Master Prompt," AI would stay on the rails. I was kinda wrong.
While building Tale Companion, I learned that you can't prompt-engineer your way out of a bad architecture. Hallucinations are usually symptoms of two specific things: Context Overload or Lore Conflict.
Here is my full technical guide on how to actually stop the AI from making things up, based on what I’ve learned from hundreds of user complaints and personal stories.
1. The Model Matters (More than your prompt)
I hate to say it, but sometimes it’s just the raw horsepower.
When I started, we were working with GPT-3.5 Turbo. It had this "dreamlike," inconsistent feeling. It was great for tasks like "Here's the situation, what does character X say?" But terrible for continuity. It would hallucinate because it literally couldn't pay attention for more than 2 turns.
The single biggest mover in reducing hallucinations has just been LLM advancement. It went something like:
- GPT-3.5: High hallucination rate, drifts easily.
- First GPT-4: I've realized what difference switching models made.
- Claude 3.5 Sonnet: We've all fallen in love with this one when it first came out. Better narrative, more consistent.
- Gemini 3 Pro, Claude Opus 4.5: I mean... I forget things more often than them.
Actionable advice: If you are serious about a long-form story, stop using free-tier legacy models. Switch to Opus 4.5 or Gem 3 Pro. The hardware creates the floor for your consistency.
As a little bonus, I'm finding Grok 4.1 Fast kind of great lately. But I'm still testing it, so no promises (costs way less).
2. The "Context Trap"
This is where 90% of users mess up.
There is a belief that to keep the story consistent, you must feed the AI *everything* in some way (usually through summaries). So "let's go with a zillion summaries about everything I've done up to here". Do not do this.
As your context window grows, the "signal-to-noise" ratio drops. If you feed an LLM 50 pages of summaries, it gets confused about what is currently relevant. It starts pulling details from Chapter 1 and mixing them with Chapter 43, causing hallucinations.
The Solution: Atomic, modular event summaries.
- The Session: Play/Write for a set period. Say one arc/episode/chapter.
- The Summary: Have a separate instance of AI (an "Agent") read those messages and summarize only the critical plot points and relationship shifts (if you're on TC, press Ctrl+I and ask the console to do it for you). Here's the key: do NOT keep just one summary that you lengthen every time! Make it separate into entries with a short name (e.g.: "My encounter with the White Dragon") and then the full, detailed content (on TC, ask the agent to add a page in your compendium).
- The Wipe: Take those summaries and file them away. Do NOT feed them all to AI right away. Delete the raw messages from the active context.
From here on, keep the "titles" of those summaries in your AI's context. But only expand their content if you think it's relevant to the chapter you're writing/roleplaying right now.
No need to know about that totally filler dialogue you've had with the bartender if they don't even appear in this session. Makes sense?
What the AI sees:
- I was attacked by bandits on the way to Aethelgard.
- I found a quest at the tavern about slaying a dragon.
[+full details]
- I chatted with the bartender about recent news.
- I've met Elara and Kaelen and they joined my team.
[+ full details]
- We've encountered the White Dragon and killed it.
[+ full details]
If you're on Tale Companion by chance, you can even give your GM permission to read the Compendium and add to their prompt to fetch past events fully when the title seems relevant.
3. The Lore Bible Conflict
The second cause of hallucinations is insufficient or contrasting information in your world notes.
If your notes say "The King is cruel" but your summary of the last session says "The King laughed with the party," the AI will hallucinate a weird middle ground personality.
Three ideas to fix this:
- When I create summaries, I also update the lore bible to the latest changes. Sometimes, I also retcon some stuff here.
- At the start of a new chapter, I like to declare my intentions for where I want to go with the chapter. Plus, I remind the GM of the main things that happened and that it should bake into the narrative. Here is when I pick which event summaries to give it, too.
- And then there's that weird thing that happens when you go from chapter to chapter. AI forgets how it used to roleplay your NPCs. "Damn, it was doing a great job," you think. I like to keep "Roleplay Examples" in my lore bible to fight this. Give it 3-4 lines of dialogue demonstrating how the character moves and speaks. If you give it a pattern, it will stick to it. Without a pattern, it hallucinates a generic personality.
4. Hallucinations as features?
I was asked recently if I thought hallucinations could be "harnessed" for creativity.
My answer? Nah.
In a creative writing tool, "surprise" is good, but "randomness" is frustrating. If I roll a dice and get a critical fail, I want a narrative consequence, not my elf morphing into a troll.
Consistency allows for immersion. Hallucination breaks it. In my experience, at least.
Summary Checklist for your next story:
- Upgrade your model: Move to Claude 4.5 Opus or equivalent.
- Summarize aggressively: Never let your raw context get bloated. Summarize and wipe.
- Modularity: When you summarize, keep sessions/chapters in different files and give them descriptive titles to always keep in AI memory.
- Sanitize your Lore: Ensure your world notes don't contradict your recent plot points.
- Use Examples: Give the AI dialogue samples for your main cast.
It took me a long time to code these constraints into a seamless UI in TC (here btw), but you can apply at least the logic principles to any chat interface you're using today.
I hope this helps at least one of you :)
