Behavior Intelligence · Scoped answers

What persistent or custom instruction mechanisms are documented?

Codex documents user guidance in Codex home, followed by project files in discovery order. Claude Code and Gemini CLI document user or global instruction files; ChatGPT and Cursor document persistent preferences in product settings. These mechanisms carry authored guidance, with different scope and precedence. The selected Claude chat evidence still does not establish a comparable persistent-instruction mechanism.

Six product answers

What the selected evidence establishes

Decide whether durable guidance belongs in user settings, repository files, workspace context, or another documented scope.

Open-source agentic coding interface

OpenAI Codex

Documented

Direct factual answer

Codex home defaults to ~/.codex unless CODEX_HOME changes it. Global AGENTS.override.md takes precedence over AGENTS.md; only the first non-empty file is used. At startup, project discovery walks from project root to working directory, selecting at most one file per directory: override, AGENTS.md, then configured fallback names. Deeper guidance follows earlier guidance. Empty files are skipped; the combined limit defaults to 32 KiB. This is authored guidance, not automatic memory.

Surface: Codex CLI
Model context: Not established
Configuration / version scope: Current product documentation consulted 2026-09-14; enabled mode, settings, and deployment still determine availability.
Reviewed: 2026-09-14

Limits and uncertainty

This claim does not update the dated prompt snapshot or establish every runtime configuration.

Evidence

SourceCodex custom instructions with AGENTS.md

Web, desktop, and mobile AI assistant

Claude

Not established

Direct factual answer

The selected dated Claude product-prompt entries do not establish a persistent custom-instruction mechanism for the represented chat surfaces.

Surface: Not established
Model context: Not established
Configuration / version scope: Not established
Reviewed: 2026-08-11

Limits and uncertainty

This is a coverage gap, not a claim that no such product feature exists.

Evidence

No supporting evidence is linked because the selected sources do not establish this behavior.

Multi-surface agentic coding product

Claude Code

Documented

Direct factual answer

Claude Code documents persistent human-authored instructions through managed, user, project, and local CLAUDE.md scopes.

Surface: Claude Code terminal CLI · Claude Code IDE integrations
Model context: Not established
Configuration / version scope: Not established
Reviewed: 2026-08-11

Limits and uncertainty

Authored instructions are distinct from auto memory and enforced settings or hooks.

Evidence

Open-source agentic command-line interface

Gemini CLI

Documented

Direct factual answer

Gemini CLI documents global and workspace GEMINI.md context, and it also supports a configured full system-prompt replacement.

Surface: Gemini CLI
Model context: Not established
Configuration / version scope: Not established
Reviewed: 2026-08-11

Limits and uncertainty

A system-prompt override replaces the built-in prompt rather than adding a small preference layer.

Evidence

Multi-surface conversational AI product

ChatGPT

Documented

Direct factual answer

ChatGPT documents custom instructions that can apply across conversations and project instructions that remain associated with a Project.

Surface: ChatGPT web · ChatGPT apps
Model context: Not established
Configuration / version scope: Not established
Reviewed: 2026-08-11

Limits and uncertainty

Behavior can vary with product settings, model, plan, and surface.

Evidence

AI code editor, coding-agent platform, and early-beta git forge

Cursor

Documented

Direct factual answer

Cursor documents user rules that apply across projects and project rules that provide repository or path-specific guidance.

Surface: Cursor editor
Model context: Not established
Configuration / version scope: Not established
Reviewed: 2026-08-11

Limits and uncertainty

The selected evidence does not establish the complete instruction assembly.

Evidence