refactor!: Remove agent breakpoint and agent snapshot

[sjrl]

Related Issues

• Related to https://github.com/deepset-ai/haystack-private/issues/331

Proposed Changes:

Remove break point and snapshot support from the internals of Agent. Motivation is that it's not heavily used and adds a lot of complexity to the Agent internals.

Open to adding this back in the future if we see a strong need (e.g. HITL + Breakpoints to enable long running Agents). And if we decide to do so I think there is a simpler way to re-add it than in it's current form.

Updated MIGRATION.md and added an upgrade release note describing the breaking changes.

How did you test it?

Updated existing tests.

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I have documented my code.
• I have added a release note file, following the contributors guidelines.
• I have run pre-commit hooks and fixed any issue.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
haystack-docs	Ignored	Preview	May 19, 2026 11:25am

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/components/agents
agent.py					829, 835-851
haystack/core
errors.py					127, 142-144, 151-153
haystack/core/pipeline
breakpoint.py					53, 94-97, 188
pipeline.py					340, 356-357
haystack/dataclasses
__init__.py
breakpoints.py
haystack/human_in_the_loop
strategies.py					471
Project Total

This report was generated by python-coverage-comment-action

[claude]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

[anakin87]

Happy about the simplification!

I left a minor comment.

In addition, we should track documentation changes to be done. But maybe MIGRATION.md is sufficient. WDYT?

Please wait before merging: I want to understand if 3.0.0-rc0 version and tag are needed before...

[sjrl]

But maybe MIGRATION.md is sufficient. WDYT?

Good point. I think MIGRATION.md is sufficient for now and we can update the docs later after we're done merging our changes and before the v3 release. WDYT?

[anakin87]

Once you've applied the minor change I requested, feel free to merge: version tag has already been placed.