McKinsey Solve 2026: What's Changed and What to Expect

If you've started preparing for McKinsey Solve using materials from 2023 or earlier, there's a good chance that a significant portion of what you've been studying no longer exists in the current assessment. The food-chain game. The plant defence module. The 110-minute format. All gone.

McKinsey Solve has changed more in the last three years than in the previous five combined, and the prep landscape hasn't fully caught up. Guides describing Ecosystem Building as a current module still rank prominently in search results. Candidate forum posts from 2023 circulate as if they were current. Prep materials continue to sell practice for games you won't see.

This article is a complete account of what Solve looked like, what it looks like now, and what changed in between — so you can verify your preparation materials are current before investing time in them.

For a full breakdown of the current format, see our complete McKinsey Solve 2026 overview.

Why McKinsey keeps changing Solve

The original reason McKinsey replaced the Problem Solving Test (PST) with a gamified assessment was straightforward: a multiple-choice test with a stable question bank can be gamed through memorisation and rote practice. Once enough prep material exists, the signal degrades — high scores start reflecting preparation rather than the underlying cognitive skills McKinsey actually wants to measure.

The same logic applies to Solve itself. Any stable game format will eventually develop a robust prep ecosystem. As that happens, scores start reflecting familiarity with the specific game mechanics rather than the reasoning skills those mechanics were designed to surface. McKinsey's response is to evolve the format — retiring games that have become too practised-for, introducing new ones that restore the signal.

This is worth understanding because it has a direct practical implication: the format you prepare for must be the current one. Materials more than 12–18 months old carry real risk of describing modules you won't see.

One important caveat: not everything changes. The underlying cognitive skills Solve tests — quantitative reasoning, structured decision-making, working memory under time pressure, pattern recognition — are stable across all versions. The interface and game mechanics change. The fundamentals don't. Mental arithmetic, fast analytical reading, and time management are worth drilling regardless of which specific games are current.

The complete timeline

2017 — Solve enters beta

Imbellus, a specialist cognitive assessment company, begins developing and testing the gamified assessment in partnership with McKinsey. Initial trials at select offices globally. The test is called the "Digital Assessment" at this stage.

2020–2021 — Global rollout, PST officially retired

By January 2021, the Problem Solving Game had replaced the paper-based PST in virtually every McKinsey office worldwide. The standard two-module format at this point: Ecosystem Building (the food-chain/food-web game) and Plant Defense (a tower-defence puzzle).

Several alternative second modules were deployed to small candidate groups during this period — Disaster Management, Disease Management, and Migration Management — but none became standard and all were eventually retired. If you've seen prep materials covering these, they describe beta games that no longer appear in the test.

Imbellus was acquired by Roblox in 2021. The name changed; test development continued under McKinsey's direction.

The assessment was renamed from "Digital Assessment" to "Problem Solving Game" (PSG) in 2021.

2022 — Renamed "Solve", Redrock Study introduced in US

The assessment was renamed from PSG to "Solve." Redrock Study was introduced in the United States as a replacement for Plant Defense — more calculation-heavy than any previous module, closer to the original PST in its arithmetic demands. Per-module timers were introduced at this point, ending the flexible time allocation that had existed previously.

The Cases section of Redrock (the six independent mini-cases that make up Part 2) was not yet present in this version.

February 2023 — Plant Defense retired, Redrock Study becomes standard globally

Plant Defense was phased out across all offices. Redrock Study became the universal second module alongside Ecosystem Building. The remaining beta modules — Disaster Management, Disease Management, Migration Management — were also retired at this point.

Standard format: Ecosystem Building + Redrock Study, approximately 70 minutes total.

The Redrock Cases section (six mini-cases) was added around this time. Prep materials describing Redrock without Cases are describing the pre-2023 version.

2024 — Sea Wolf introduced in beta

Sea Wolf — also referred to as the Ocean Cleanup game, Ocean Treatment game, or Microbe game — was piloted globally as a third module, appearing after Ecosystem Building and Redrock Study. When all three were present, the total assessment time reached approximately 110 minutes.

The beta version had only two ocean sites rather than three, and ran for 35 minutes. Neither of these specifications matches the current format. Sea Wolf appeared for approximately 20% of candidates during 2024 — most still received the two-game Ecosystem + Redrock format.

Mid-2025 — Ecosystem Building phased out, format stabilises

The most significant format change since 2021. Ecosystem Building — the food-web game that had been a fixture of Solve since its introduction — was phased out globally. Sea Wolf became the standard second module.

The format settled at two games, 65 minutes: Redrock Study (35 minutes) + Sea Wolf (30 minutes). Note the time reduction: Sea Wolf dropped from 35 minutes in beta to 30 minutes in the standardised format. Any prep material citing 35 minutes for Sea Wolf is out of date.

The Sustainable Futures Lab (SFL) also began rolling out in select regions as an additional third module — adding approximately 20 minutes for candidates who receive it, bringing their total to 85 minutes.

2026 — Current stable format

Redrock Study + Sea Wolf is the standard format for all candidates globally. 65 minutes. Two separate timers, one per module. Sea Wolf fully standardised at three sites, 30 minutes, fixed mechanics across all regions.

The SFL is present in select regions and roles, producing an 85-minute format for those candidates. Check your invitation email for the stated duration — 65 minutes means Redrock + Sea Wolf only, 85 minutes means the SFL is also included.

One honest note on Ecosystem Building: the overwhelming majority of candidates in 2026 are receiving the 65-minute two-game format. However, a small number of candidate reports suggest the 110-minute format with Ecosystem Building may still appear in some regions or recruitment tracks. If your invitation specifies 110 minutes, Ecosystem Building may still be present — prepare accordingly. For everyone else, Ecosystem Building is gone.

What this means if you're preparing now

Ignore any guide that covers Ecosystem Building as a current module. Building a food web, managing species slots, balancing populations — none of this is relevant to the 2026 format. The strategies are specific to the game interface and don't transfer to Redrock or Sea Wolf.

Ignore Plant Defense, Disaster Management, Disease Management, and Migration Management. All retired, none returning.

Warning sign in prep materials: if a guide says the test is 110 minutes, it is describing the 2024 three-game format with Sea Wolf as an optional third module. That format is no longer standard.

Warning sign in Redrock materials: if a guide's Redrock section doesn't mention the six mini-cases in Part 2, it's describing the 2022 version of the game before Cases were introduced. The Cases section is now a significant portion of the Redrock score.

Warning sign in Sea Wolf materials: if a guide says Sea Wolf runs for 35 minutes, it's describing the beta version. The current time limit is 30 minutes. That five-minute difference is meaningful — anything that tells you to budget 35 minutes per session is calibrating your pacing wrong.

The three modules to prepare for in 2026:

• Redrock Study — 35 minutes, Part 1 study (Investigation → Analysis → Report) plus Part 2 (six mini-cases)
• Sea Wolf — 30 minutes, three contaminated ocean sites across five phases each
• Sustainable Futures Lab — ~20 minutes, only if your invitation specifies 85 minutes

What hasn't changed

Amid the format evolution, several things have remained constant since Solve replaced the PST:

• Percentile scoring. You are ranked against the candidate pool, not graded against a fixed standard.
• Dual product and process scoring. McKinsey has evaluated both what you decided and how you decided it since the beginning. For more on this, see our behavioural score article.
• The five cognitive dimensions. Critical thinking, decision-making, metacognition, situational awareness, and systems thinking are what the assessment is designed to measure across every module and every version.
• Untimed tutorials. Every module begins with an untimed walkthrough. The clock starts only after you complete it.
• Allowed tools. Pen, paper, and a physical calculator have always been permitted. No external software.
• Home format. Solve has always been taken remotely on your own computer.
• One sitting. No breaks between modules. The full duration runs continuously.
• Global result sharing. Your result is shared across McKinsey offices worldwide. One score follows all your applications in the same cycle.
• 12-month retake policy. If you don't advance, you can reapply after 12 months.

What to do if you've been preparing with outdated materials

If you've been studying Ecosystem Building strategy, the most useful thing to know is that the quantitative and reasoning skills transfer — pattern recognition, systematic evaluation, time management — but the specific mechanics don't. An hour spent on Ecosystem Building strategies is not entirely wasted, but it is less valuable than the same hour on Redrock or Sea Wolf.

If your remaining prep time is limited, prioritise in this order:

1. Redrock Study — 35 minutes, the longer module, more calculation-heavy. Mental arithmetic speed and the Investigation-to-Analysis-to-Report flow are the things to drill.
2. Sea Wolf — 30 minutes, the more spatial and working-memory-heavy module. Full end-to-end runs under the 30-minute clock are the most effective preparation.
3. SFL — only if your invitation says 85 minutes. Shorter module, harder to prepare for mechanically, lower time-weighting in the overall assessment.

The mental arithmetic work you've been doing transfers regardless of which modules you've been studying for. Percentages, weighted averages, growth rates — these appear throughout Redrock and inform Sea Wolf decisions. That time wasn't wasted.

Related guides

• What is the McKinsey Solve assessment? — Complete 2026 overview
• The McKinsey Sea Wolf Game — complete 2026 guide
• McKinsey Redrock Study — phases, scoring, and strategy
• McKinsey Sustainable Futures Lab — what to expect
• McKinsey's behavioural score explained
• Sea Wolf strategy guide — optimal play for each phase (simulator access required)