From Imbellus to McKinsey Solve: What Actually Changed (2026)
If you Googled "Imbellus" and landed on a page about McKinsey Solve, the rebrand caught you mid-prep. This is the honest naming history — Imbellus → PSG → Solve — and what's actually different about the test in 2026 versus the original Imbellus version. Plus which old prep advice still holds up, and which to throw out.
TL;DR
- 2020: McKinsey acquired Imbellus. The company "Imbellus" no longer exists as a separate brand — the team is inside McKinsey.
- 2024: The candidate-facing test was renamed from "Problem Solving Game (PSG)" to "McKinsey Solve". Same engine, new label.
- Format today: 2–3 mini-games (Sea Wolf microbe selection, Redrock Study, Sustainable Future Lab) totaling ~70 minutes. No live score feedback during the test. The original Imbellus Ecosystem Building game was retired in early 2026.
- Old prep that still works: reasoning frameworks, exhibit-reading drills, structured decision-making under time pressure. Old prep to throw out: Ecosystem Building food-chain walkthroughs, species/calorie lists, Plants & Animals scenarios, anything claiming live score feedback.
- Practice the current format: one free play of each 2026 game — no credit card.
Timeline: Imbellus to Solve
The short version of nine years of product history. If you saw "Imbellus" in a forum thread, "Problem Solving Game" on McKinsey's site, and "McKinsey Solve" in a recruiter email — they're the same test at different points on this timeline.
Imbellus founded
Rebecca Kantar founds Imbellus to build scenario-based assessments. The Ecosystem Building game (8-species food chain, calorie balance) becomes the flagship.
McKinsey adopts the Ecosystem Game
McKinsey rolls out the Imbellus-built Problem Solving Game (PSG) as a screening step for consultant candidates. Plants & Animals and Disaster Management join the rotation.
McKinsey acquires Imbellus
McKinsey acquires Imbellus and brings the assessment fully in-house. The candidate-facing brand is still 'Problem Solving Game'.
Redrock Study added
McKinsey ships the Redrock Study mini-game — a structured quant + case task that swaps the older Plants & Animals scenario for many candidates.
'Solve' rebrand + Sea Wolf launches
McKinsey publicly renames the test to 'McKinsey Solve' and introduces the Sea Wolf game — a microbe-selection task for cleaning 3 contaminated ocean sites. Mechanically unrelated to the older food-chain Ecosystem game. Sustainable Future Lab (SFL) is added for select candidates.
Ecosystem Building retired
The original Imbellus Ecosystem game (food chain / calorie balance) is removed from the active Solve rotation. Sea Wolf replaces it as the biology-themed mini-game.
Current 3-game format
Most candidates see two of: Sea Wolf (microbe selection, 3 ocean sites), Redrock Study, and Sustainable Future Lab. Total runtime ~70 minutes. No live score feedback.
Naming sourced from McKinsey careers pages, Imbellus's press release archive, and direct candidate reports captured through SolvePrep between 2024 and 2026.
What's still the same as the original Imbellus
The design philosophy is intact. McKinsey kept the scenario-based, applied-reasoning structure Imbellus pioneered and built on top of it. If you read an old 2019 article describing what the test measures (structured problem-solving under partial information, pattern recognition, data interpretation, judgment under time pressure), that description still applies in 2026 — even though the specific games have changed.
What didn't carry over: the games themselves. The original Ecosystem Building game (food chain, 8 species, calorie balance) was retired in early 2026 and replaced by Sea Wolf, a different game with different mechanics — pick 3 microbes for each of 3 ocean sites, where the average of their numeric attributes must fall inside target ranges and the chosen traits must include at least one desirable and zero undesirable. A candidate who only practiced Ecosystem food-chain logic will be lost in Sea Wolf.
Skills that transferred cleanly: trait-matching pace, exhibit-reading speed, and mental arithmetic under time pressure. Skills that no longer apply: food-chain validity checks and calorie balancing — those mechanics are gone from the current assessment.
What actually changed
Two new mini-games
Redrock Study (added 2022) is a structured quant + case task — closer to a traditional consulting case than to the original Imbellus design. Sustainable Future Lab (added 2024) is a judgment / stakeholder scenario. Neither existed in the original Imbellus rollout.
No live score feedback
Older Imbellus builds gave intermediate signals as candidates worked. The current Solve test hides this — you finish blind. Practically: timed full-rep reps now matter more than 'just understand the rules' practice.
UI polish
Cleaner interface, faster animations, mobile-restricted (desktop only). The interaction model is the same — drag/click/select — but the surface feels like a 2024 SaaS product, not a 2018 prototype.
Refreshed content libraries
Species lists, microbe sets, exhibit data, and Redrock case data are all rotated periodically. Anyone selling you 'the answer key from a real test' is either selling stale data or fabricating it.
Plants & Animals retired (for most)
The Plants & Animals scenario from early Imbellus is rarely seen in 2026 — most candidates get Sea Wolf or Redrock instead. Disaster Management is also no longer in active rotation for the majority of test slots.
Tighter total runtime
Original PSG could run 70–80 minutes including instructions. The current Solve test is more crisply paced — most candidates finish in ~70 minutes flat, with clearer per-game timers.
Does old Imbellus prep still work?
Still useful
- • Strategy guides on how to read exhibits under time pressure
- • General consulting-math drills (rates, ratios, weighted averages)
- • Historical context on the retired Ecosystem game: Ecosystem Game (retired) explainer
- • Mental models for trait-matching and structured decision-making
Throw it out
- • Specific species or microbe ID lists from 2018–2022 walkthroughs
- • Anything claiming live in-test score feedback (no longer present)
- • Plants & Animals deep dives — rarely shown in 2026
- • Disaster Management walkthroughs — same reason
- • "Leaked answer keys" — content libraries rotate, these are stale by design
The honest test: if a piece of prep teaches a skill (reasoning, math, exhibit reading), it probably still applies. If it teaches a specific answer (this species, that microbe, this exhibit), discard it. McKinsey rotates the content libraries precisely so memorized answers stop working.
How to practice the current format
The most useful thing you can do in a 2-week window is run full timed reps of the actual 2026 mini-games. SolvePrep gives one free play of each — no credit card — which is enough for a diagnostic.
Sea Wolf
Pick 3 microbes for each of 3 contaminated ocean sites. Averaged attributes must fall in target ranges; traits must include ≥1 desirable and 0 undesirable. Replaced the retired Ecosystem Building game in 2026.
Try free →Redrock Study
Quant-heavy case task added in 2022. Closer to a traditional consulting case than to original Imbellus.
Try free →Sustainable Future Lab
Judgment scenario added in 2024. Stakeholder priorities under sustainability constraints.
Try free →FAQ
Practice the current 2026 format
The names changed. The skills didn't. One free play of each current mini-game — Sea Wolf, Redrock Study, and Sustainable Future Lab. No credit card.
Sources & method: naming history reconstructed from McKinsey careers pages, Imbellus's press release archive, and ~1,200 SolvePrep simulator attempts captured between 2024 and 2026. If McKinsey shifts the format again, we update this post — check the date stamp above. Updated May 30, 2026.