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Custom Instructions let you tell ZeroTwo who you are and how you want it to respond — once, and it applies everywhere. Instead of re-explaining your background or reformatting every response, set it once and every new chat starts with that context baked in.

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What custom instructions are

Custom Instructions are a persistent system-level instruction set. Every time you start a new chat, ZeroTwo reads your Custom Instructions and uses them to shape its behavior — before you’ve said anything. Access: Settings → Personalization → Custom Instructions

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The two fields

Custom Instructions are split into two focused fields:

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Field 1: “What should ZeroTwo know about you?”

This is your background. Tell ZeroTwo who you are, what you do, what context is relevant to most of your conversations. Good things to include:
  • Your job title and field
  • Technologies, languages, or tools you use
  • The stage or type of company you work at
  • Projects or goals that often come up in your work
  • Domain knowledge you have (so ZeroTwo doesn’t over-explain basics)

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Field 2: “How should ZeroTwo respond?”

This is your communication preferences. Tell ZeroTwo how to format responses, what tone to use, what to include or avoid. Good things to include:
  • Preferred response length (concise vs. comprehensive)
  • Preferred format (bullet points, prose, tables)
  • Code style preferences
  • Things to skip (no disclaimers, no “Great question!”, no padding)
  • Tone (formal, casual, direct)

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Examples

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Example 1: Software Engineer

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Example 2: Marketing Manager

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Example 3: Researcher / Academic

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What makes good custom instructions

Focus on things that are true across most of your conversations. Very specific instructions that only apply in rare cases can be given in-chat instead.

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Custom instructions vs. project instructions

If you’re working on a project with its own context, set Project Instructions for that project. They’ll override your Custom Instructions when you’re in that project’s chats.

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How custom instructions interact with memory

Custom Instructions and Memory are complementary:
  • Custom Instructions = things you explicitly choose to tell ZeroTwo
  • Memory = things ZeroTwo infers and saves from your conversations
Both are applied to new chats. If they overlap (e.g., your Custom Instructions say you prefer Python and a memory also says you prefer Python), they reinforce each other. If they conflict, Custom Instructions generally take precedence since they’re explicit.

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Applying changes

Changes to Custom Instructions take effect immediately for all new chats. They are not applied retroactively to existing chats already in progress.

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Character limits

Both fields accept substantial text. For best results, keep each field under 2,000 characters — focused, specific instructions are more effective than exhaustive ones.