Dependent Select Fields
Load one select's options from another's choice without stale values slipping through.
What it adds
A parent select that constrains a child select's options, loaded on demand, with the request ordering and invalidation handled properly.
What your agent is told to do
5
What your agent is told to do
5-
1
Find the selects whose valid options depend on another field and load the child options from the server when the parent changes.
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2
Track requests so only the newest response is applied. A user changing the parent three times quickly must not end up with the first response's options.
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3
Clear the child selection whenever the new option set no longer contains it, and say so rather than silently blanking the field.
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4
Give the child a real disabled, loading, empty, and error state, and re-validate the pair on the server — never trust that the submitted child belongs to the submitted parent.
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5
Do NOT preload every combination into the page. It bloats the payload and goes stale; fetch on demand and cache per parent value.
Edge cases it handles
6
Edge cases it handles
6- Out-of-order responses must be discarded, not merged.
- An edit form whose saved child option is now inactive or absent must still display the saved value rather than showing an empty select.
- An empty option set needs its own message and a disabled control, not a select with one blank row.
- A failed load must offer a retry and must not leave the child enabled with nothing in it.
- Clearing the parent must clear and disable the child, not freeze the last options.
- Deep chains — country, region, city — must invalidate every level below the one that changed.
Definition of done
8
Definition of done
8- Changing the parent reloads the child options and discards superseded responses.
- A child value invalidated by the parent change is cleared and the user is told.
- Loading, empty, and error states exist and disable the control appropriately.
- Saved-but-inactive child values still render on edit forms.
- The server rejects a child value that does not belong to the submitted parent.
- Every level below a changed level in a chain is invalidated.
- The feature matches the existing design system.
- No existing functionality is broken.
Related features
Unit Converter
Unit Converter
Let people convert a value between units without leaving the page they are on.
What it does
An inline converter that takes a typed value in one unit and shows the equivalent in another, in place.
How it works
- 1 Start from the units the app actually deals in. A shipping tool needs weight and length; a recipe tool needs volume and temperature. Ship those and leave the rest out.
- 2 Convert as the user types, with the result visible beside the input rather than behind a submit button. Let either side be edited so the conversion runs in both directions.
- 3 Reuse the app's existing number parsing and display formatting rather than writing new ones. If Locale-Aware Numbers and Dates or Number Formatting Component is already present, the converter must render through it so grouping and decimal marks match the rest of the app.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/unit-converter
Voice Dictation
Voice Dictation
Put a microphone in text fields so people can speak their input instead of typing it.
What it does
A dictation control on the app's longer text inputs that transcribes speech into the field as the user talks.
How it works
- 1 Add the control to the fields where typing is genuinely tedious: long descriptions, notes, comments, and message bodies. A microphone on a postcode field is clutter.
- 2 Show interim results in the field as they arrive, visually distinct from committed text, so the speaker can see it is working and correct course before they finish.
- 3 Reuse the app's existing Voice Transcription for the server-side path so one recognition configuration and one set of language settings serve both dictation and recorded audio.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/voice-dictation
Code Editor Field
Code Editor Field
Edit code, JSON, and config with syntax highlighting instead of a bare textarea.
What it does
A form field backed by a real code editor: syntax highlighting, a language mode per field, and inline validation that tolerates work in progress.
How it works
- 1 Load the editor library lazily, only on views that use it, and render a usable plain textarea until it arrives. It must never block first paint.
- 2 Set the language mode per field from what the field actually holds, and validate against that mode.
- 3 Report syntax errors as you go, but never block typing or reset the content. Half-written JSON is a normal intermediate state; only submission should be gated.
Copy the prompt
No account needed
Add this feature to my app:
https://addthisfeature.com/x/code-editor-field
How it works
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1
Copy the link
Grab the Markdown instruction URL for this feature.
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2
Give it to your AI
Paste it into Claude Code, Cursor, v0, Lovable — whatever you build with.
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3
It inspects, then implements
Your agent reads your existing app first, then adds the feature to fit it.
Works with your stack
These instructions are written to adapt. They tell the agent to detect your framework, match your existing design system, and reuse what you already have — rather than assuming a particular stack.
Need it tighter than that? Customize the feature and tell it exactly what you're running.