OpenAI Developer Experience
Chapter 06of 08
2:00–2:45 CDT
Chapter 062:00–2:45 CDT

Existing
projects

Give Codex enough project context to make a change that belongs in the codebase.

01

Working in an existing codebase

The project already contains decisions about architecture, visual language, accessibility, data flow, and review. Codex should find and follow them before it changes the code.

Project instructions

Codex starts with AGENTS.md to find the right commands, constraints, and parts of the repository it should not change.

Relevant skills

Codex opens the closest skill when the project has a repeatable workflow for this kind of change.

Existing system

Codex finds the shared components, tokens, typography, icons, layout primitives, and local wrappers before adding anything new.

Project tools

Codex follows the project’s existing data access, browser checks, screenshots, tests, and build tooling.

Stable project knowledge belongs in AGENTS.md. Repeatable work belongs in skills.

02

Add Audience momentum

The feature should fit User Insights’ existing data flow and visual system instead of feeling pasted beside it.

Feature

Audience momentum

Show where activity is speeding up or slowing down for the selected region and time period.

Shared controls

Use the selected region and the existing 7-day or 28-day period.

Existing data

Derive the result from the project’s current data helpers and fictional fixtures.

Product behavior

Selecting a country should highlight the same country on the globe.

Product hierarchy

Keep the globe as the main focus instead of turning the page into another dashboard grid.

User Insights prompt
Add an Audience momentum panel to User Insights.
It should show where audience activity is speeding up or slowing down
for the selected region and time period.
Highlight the fastest-growing country, show a compact trend,
and list a few countries gaining or losing momentum.
When I select a country, highlight it on the globe.
Before you build it, look through the project and reuse the existing region and period state,
data helpers, components, charts, tokens, and interaction patterns.
Keep the globe as the main focus, use the existing fictional data,
and check the result on mobile, tablet, and desktop.
03

Make reviews easy

Codex should leave the reviewer with enough evidence to understand the change without rebuilding the environment and rediscovering the behavior.

User-facing change

A short explanation of what changed and why.

Affected routes and states

The exact parts of the product the reviewer should inspect.

Checks run

Focused tests, browser checks, and the production build.

Breakpoint evidence

Screenshots at the widths the change can affect.

Interaction evidence

A short recording when motion or a multi-step interaction cannot be judged from still images.

Open questions

Anything that still needs product or visual judgment.

The evidence should follow the risk of the change. One focused comparison is often more useful than a gallery of screenshots.

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