Planning Major Dependency Upgrades With Claude

1. The challenge of major version upgrades

A major version jump, say from Symfony 6 to Symfony 7 or from a PHP-7-compatible library to a PHP-8-only version, almost always brings breaking changes that cannot simply be resolved by Composer or npm automatically. The actual work rarely lies in the version bump itself in composer.json or package.json, but in tracking down every place in your own code affected by a changed signature, a removed method, or altered default behavior.

Especially on grown codebases with hundreds of usage sites of a library, this search is labor-intensive and error-prone by hand. Claude can support this as a research and analysis tool that structures the groundwork, but it does not replace the final domain judgment and testing in your own project.

2. Extracting breaking changes from changelogs and migration guides

The first sensible step is feeding the official changelog or upgrade guide of the target version into the context and having Claude extract the relevant breaking changes in a structured way, organized by affected class, method, or configuration option. That is noticeably faster than manually reading through an often several-thousand-line UPGRADE.md, especially when only a subset of the library is actually used in your own project.

It is important to supply the full text of the official guide as the source rather than relying on the model's knowledge of the library. Only that guarantees the extracted breaking changes actually match the official documentation instead of resting on outdated or incomplete training knowledge.

# Provide the official upgrade guide as context
curl -s https://raw.githubusercontent.com/symfony/symfony/7.0/UPGRADE-7.0.md \
  -o upgrade-guide.md

claude "Read upgrade-guide.md and list all breaking changes \
  affecting the classes Symfony\Component\HttpFoundation\Request \
  and Symfony\Component\Routing\Router. Group by class and give \
  the concrete code change for each."

3. Identifying affected code in your own project

With the list of breaking changes as a basis, Claude Code can search your own repository specifically for every usage site of the affected classes, methods, or configuration keys. This happens through targeted searches in the code, combined with an understanding of which usage patterns are actually affected by a given breaking change and which only look superficially similar but stay unproblematic.

This step is noticeably more valuable than a plain grep text search, because Claude understands the context of a match: a call to a same-named method from a different class is correctly recognized as unaffected, while a call with an actually changed signature is flagged. On very large codebases, splitting the analysis by module or directory is advisable to keep it manageable.

claude "Search src/app/code for every call to \
  Request::getContent() with the second parameter set to true. \
  This signature was removed in Symfony 7. List every match \
  with file, line, and a suggested replacement."

4. Building a step-by-step migration plan

Once the affected code is known, Claude can turn it into a concrete, prioritized migration plan that breaks the changes into sensible, independently testable steps. A sequence that starts with the lowest-risk, isolated changes and works toward the spots with the most dependencies makes sense, so a failure is caught early instead of only at the end of one large, monolithic migration pull request.

A good migration plan lists, for every step, not just the code change itself but also which tests need to run afterward and which observable behavior changes. That makes it easier for the team to track progress and pause the migration if needed, without losing track of what has already been done and what remains open.

claude "Turn the list of 23 matches into a migration plan \
  with at most 6 steps. Start with isolated spots that have \
  no dependencies on other modules. State the affected files \
  and expected test cases for every step."

5. Practical example: a major upgrade of a PHP library

A realistic scenario: a team plans the move from guzzlehttp/guzzle 6 to version 7, because a new Symfony version requires it as a minimum. The official upgrade guide lists, among other things, changed exception classes and altered default redirect behavior. Claude extracts these points from the guide, then searches the project for catch blocks referencing the old exception class and for explicit redirect configuration in HTTP client calls.

These findings turn into a migration plan of typically three to five steps: first adjust exception handling, then set the redirect configuration explicitly instead of relying on the old default behavior, and finally bump the Composer version, accompanied by a full test run. This order minimizes the risk of a single large commit introducing several independent sources of failure at once.

6. Limits: Claude does not know every library version up to date

One reservation holds without exception: Claude's training knowledge has a cutoff date, and very recent library versions or recently released patch releases with follow-up breaking-change fixes may simply not be known to the model. Anyone relying solely on the model's internal knowledge instead of explicitly supplying the current official changelog risks outdated or incomplete information.

That is why the approach described in this article, actively supplying the migration guide as context, is not an optional convenience step but the basic prerequisite for reliable results. Without this current context, Claude may in the worst case work off an outdated mental model of a library version that sounds plausible but is factually wrong.

7. Why verification remains mandatory

Even with current context, every code change Claude suggests remains a proposal that must be verified against the project's actual test suite. Especially for behavior changes that do not show up as a compile or lint error but only become visible at runtime, say altered default behavior around time zones or character encoding, purely static analysis is not enough.

A reliable migration process therefore always combines Claude's suggested changes with a full test run, ideally supplemented by targeted manual spot checks on critical spots like payment processing or authentication, where an undetected bug would be especially expensive. Automated tests alone rarely cover every behavior change a major upgrade brings.

8. Automation versus human control in the upgrade process

The sensible division of labor has Claude handling the time-consuming but mechanical research and search work, while the domain judgment of whether a suggested change is correct in the specific context of the project stays with an experienced developer. This split uses the model's strength at quickly searching and structuring large amounts of text without handing off responsibility for final correctness to the model.

Especially on security-relevant or financially critical code, no suggestion should be accepted unchecked, no matter how plausibly it is phrased. A migration process that consistently respects this boundary benefits from the speed of AI-assisted research without giving up control over critical decisions.

9. A practical workflow for a development team

A four-step process has proven effective for teams: first, supply the official migration guide as context and extract breaking changes. Second, have the project searched specifically for affected code. Third, have a prioritized migration plan broken into small steps created. Fourth, implement, test, and only then begin each step in turn, instead of bundling the entire migration into one single, hard-to-review commit.

This process integrates well into existing pull request conventions by submitting each migration step as its own, small pull request. That makes not only code review easier but also a targeted rollback of individual steps possible, should an unexpected problem show up after implementation.

10. Summary

11. FAQ: Planning Dependency Upgrades: The Essentials