Initialize versioned Dag bundle for callbacks when bundle_version is None

[nikolauspschuetz]

When bundle versioning is disabled (disable_bundle_versioning=True), DagRun.produce_dag_callback() sets bundle_version=None on the callback request. DagFileProcessorManager.prepare_callback_bundle() then skipped bundle.initialize() for versioning-capable bundles because the guard required a truthy request.bundle_version. As a result, _add_callback_to_queue() built DagFileInfo from an unresolved bundle.path (observed as /dev/null for backends whose path is only valid after initialization).

This initializes the bundle whenever it supports versioning — even when bundle_version is None — so the bundle resolves its current effective version and callbacks always queue a usable path. The normal versioned path and the non-versioning path are unchanged.

closes: #64891

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Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Opus 4.8)

Generated-by: Claude Code (Opus 4.8) following the guidelines

[boring-cyborg]

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[Copilot]

Pull request overview

Fixes callback-only Dag processing when bundle versioning is disabled (so callback requests carry bundle_version=None) by ensuring versioning-capable Dag bundles are still initialized, allowing bundle.path to be resolved before queueing callbacks.

Changes:

• Initialize bundles for callbacks whenever bundle.supports_versioning, even when request.bundle_version is None.
• Add unit tests covering initialization and resolved bundle.path behavior for bundle_version=None.
• Add a bugfix newsfragment documenting the change.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
airflow-core/src/airflow/dag_processing/manager.py	Initialize versioning-capable bundles for callbacks even when bundle_version is None, ensuring bundle.path is resolved before building DagFileInfo.
airflow-core/tests/unit/dag_processing/test_manager.py	Adds/updates tests to validate initialization and resolved bundle paths for callback requests with bundle_version=None.
airflow-core/newsfragments/64891.bugfix.rst	Documents the bugfix in the release notes.