Know what to test before you upgrade Next.js.
When you're responsible for an upgrade, you need to know which reported problems resemble your application and what to check before release. This analysis brings those examples together, with the conditions reported and links to the original issues.
3,114 work items · June–August 2026 · Original analysis reviewed September 8, 2026
Start with how your application behaves in production.
The examples below describe an image-rendering failure reported only in production SSR and intermittent route failures reported after an upgrade. They give an application team specific behavior to investigate alongside its existing tests.
The broader analysis groups runtime, routing, and build work so you can focus on the parts of Next.js you use. It also separates routine compatibility activity that can otherwise make the repository look busier than your upgrade investigation needs to be.
An image-rendering problem that didn't appear in development.
A reporter using Next.js 16.2.6 described a production SSR crash when the image component tried to sort frozen configuration arrays. They reported that the problem did not occur in development mode. Read issue #94740.
When this deserves attention: Your application uses next/image with server rendering, and its version and configuration resemble the report.
What to check: Render representative image-heavy pages using your production build and deployment configuration. Compare any failure with the report and its linked fix before deciding whether it affects your upgrade.
Source details
This is reported behavior, not a reproduction performed by BTA. The report includes environment information and a reproduction link.
A successful build still left routes returning 404s.
Another report describes intermittent 404 responses after an App Router application moved to Next.js 16.2.9. The author said the build succeeded and route files had not changed. Failures appeared during navigation and direct URL access. Read issue #94802.
When this deserves attention: You're testing an App Router upgrade and need to check that users can reach existing pages reliably.
What to check: Exercise important routes through in-app links, direct URLs, and refreshes in the deployment setup you plan to use. Compare the reported versions and hosting with your own before adding this issue to your upgrade watchlist.
Source details
The report describes production-mode reproduction steps but selects the development-stage field. That discrepancy and the intermittent behavior need checking; the report does not establish a confirmed cause.
Find the other records relevant to your application.
The original analysis organized the selected history into areas that an application team can review separately:
| Area | What the original analysis recorded | How to use it |
|---|---|---|
| Runtime, cache, and performance | 79 items; 32 open at the analysis date | Look for conditions that match how your application renders and serves requests. |
| Routing, output, and deployment | 84 records; 32 open at the analysis date | Narrow the search by router, output mode, and hosting setup. |
| Turbopack | 95 labeled items | Review this area if your upgrade changes or depends on this build path. |
| Routine compatibility work | 111 React-sync and React 18 test PRs | Distinguish maintenance activity from reported application behavior. |
These figures describe the original analysis window. The linked records may have changed since then.
Original analysis figures and scope
The original review recorded 891 open items, 18 stable releases and 113 prereleases. Median close time was reported as 0.83 days; the runtime/cache group reported a 54.07-day P95 close time. These are dated summaries, not estimates of your upgrade effort.
Bring a specific test plan to the upgrade discussion.
For each relevant example, record the affected route or feature, the conditions you need to reproduce, and who will check it. Keep the issue link with the test so another engineer can follow the reasoning. Set aside reports that do not match your application, and revisit unresolved ones when choosing the target version.
This is where the repository history becomes useful: it gives your team concrete cases to work through before release.
What this analysis is based on.
The original review covers selected public Next.js issues and pull requests from June through August 2026, alongside release records. It groups work by subject and examines status, timing, and discussion activity. The examples above expand on records already named in that review.
These are public reports rather than tests of your application. Check the original records for updates and confirm relevant behavior against your own versions and deployment.
The aggregate figures come from the original published analysis and have not been recalculated for this revision. Source descriptions were reviewed September 19, 2026.
These published analyses include additional source material beyond the standard collector. Read what each analysis view measures.
What needs checking in your upgrade?
Bring the version change you're considering and the parts of your application you're concerned about. We'll agree on a diagnostic that helps you find the relevant work and decide where to investigate.
Request a Diagnostic