Measure how
they prompt.
Measure what
they catch.

Acuity drops candidates into a live IDE with an AI pair-programmer on a strict token budget — then quietly corrupts a slice of its replies. You watch from the other side as they ration prompts and catch the lies. Or don't.

Start a session
Acuity is free — you only pay Anthropic for the AI calls(bring your own API key)
↑ drag to change
Interviewer view · hallucination injector
Probability30%
Sithu · 14:22:48
What's the time complexity of heapq.heappush and heappop?
AI · 14:22:50corrupted
Both heapq.heappush and heapq.heappop run in O(n) time, because each operation has to walk the full array to restore the heap invariant. heappush appends and sifts up, heappop swaps the last element to position 0 and sifts down. Space is O(1) auxiliary.
↑ hover the underlined spans
livetokens 1,242 / 6,000injected 2 / 4
session · 7I1Q5K5Y
How it works

Three surfaces, one truth.

acuity.app — watch in silencestep 2/3
live · 04:32K-th largest · debugging
1heap = []
2for n in nums:
3    if len(heap) < k:candidate cursor
4        heapq.heappush(heap, n)
5    elif n > heap[0]:
AI · 14:22:50corrupted
Heap ops are O(n); each one walks the full array.
Tokens
1,242 / 6,000
Caught
1 / 2
Pastes
0
Eight interview formats included
change anytime
Algorithm / LeetCode
4k tokens
syntax-only · 0% halluc
syntax_only
API integration
12k tokens
hints · 12k tokens
hints_only
Debugging
6k tokens
30% halluc
hints_only
Code review
4k tokens
open · 4k tokens
open
Refactor / optimize
6k tokens
same-behavior tests
no_full_solutions
SQL / data query
3k tokens
expected-output
hints_only
Test writing (TDD)
4k tokens
explain don't write
explain_only
System design
20k tokens
open · 20k tokens
open
Features

Built for the way engineers actually work today.

integrity
Catch every suspicious moment, in order.

Every paste, tab switch, idle gap, and AI corruption shows up as a marker on the replay scrubber — chronologically, never aggregated away.

4% first edit
11% AI corrupted
15% pushed back
23% paste 142ch
34% tab switch
41% idle 92s
58% 3/3 ✓
67% submitted
editpaste / AItab switchcaught / done
dashboard
Mission-control dashboard.

One screen for everything: live sessions, queued interviews, completed scorecards, with token spend and caught-rate trends across your team.

Search infra — onsite #2live—
Stripe payment flowpending—
Binary search — buggyended8.6
Aggregate orders queryended7.4
share
One link. No webcam. No install.

Send candidates a single URL — they create a free account in 10 seconds, then land in a real Monaco editor. No browser plugins, no screen-recording permission, no microphone. Just the code, the chat, and the moments that matter.

acuity.app/join/7I1Q5K5Y
link is single-use · expires when session ends
schedule
Schedule ahead. Or start cold.

Create a session and run it now, or assign a time slot and the invite link goes live automatically when the window opens.

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guardrails
Stack guardrails. Or write your own.

Pick from five built-in policies — hints only, no full solutions, explain don't write, syntax only, open — and stack as many as you want. Custom presets and free-form rules let you shape the AI's behavior to match how your team actually interviews.

hints_only
no_full_solutions
syntax_only
+ custom rule
cost
Always free. Bring your own Anthropic key.

Acuity charges nothing. You pay Anthropic directly for the Claude calls your interviews use — a Haiku-powered 50-minute session lands well under a dollar.

Per session
$0.32
billed by
Anthropic, not us

Typical 50-minute interview · claude-haiku-4-5 · ~5k tokens. Your key, your bill.

grading
Claude grades the judgement, not the typing.

Four dimensions: prompt quality, errors caught, code correctness, and how much they leaned on the AI. With a written justification per dimension.

7.6/10 · Alex ChenStrong hire
Prompt quality82
Caught AI errors75
Code correctness60
Approach88
Contact

Get in touch with the team.

Acuity is always free — you only pay Anthropic for the AI calls you use. Tell us a bit about how you'd use it and we'll send you a sandbox key and walk through the platform together.

Cost
Free, forever
Bring your own AI
Plug in your Anthropic key
Response time
Usually under 24 hours