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venu-banaras · 2026-06-05T20:57:26Z

Problem

Older YOLO variant checkpoints sometimes saved without separate YAML files might sometimes have missing, None or malformed names property. Due to this and the current Exporter class logic, we immediately fallback to default_class_names() which assigns 999 generic classes silently, regardless of model's actual class count.

Solution

Add a fallback for export when a checkpoint's names property is missing, None or malformed, resolving it via model.yaml() before falling back to default_class_names().

Changes

1. ultralytics/engine/exporter.py - Try to resolve names via model.yaml before falling back to default_class_names() and give a warning to the user in the process.

tests/test_onnx_legacy_names.py - Testing file to test missing, None type and malformed names property.

Further improvements

Infer number of classes from detection head of any YOLO variant, instead of assigning 999 generic class names to any type of exported model.
Add empty class name string check in check_class_names() and give a warning to the user, so that they know that certain classes might come as empty strings. Just a quality of life improvement.

UltralyticsAssistant · 2026-06-05T20:57:46Z

👋 Hello @venu-banaras, thank you for submitting a ultralytics/ultralytics 🚀 PR! This is an automated message to help with review readiness—an engineer will assist you shortly. Please review the checklist below to help ensure smooth integration. 😊

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UltralyticsAssistant

🔍 PR Review

_{Made with ❤️ by Ultralytics Actions}

The legacy names fallback logic and new ONNX regression coverage look solid overall, but there is one functional regression in exporter.py: the TensorRT <8.5.0 end-to-end safeguard was unintentionally removed when scoping the engine workaround to int8. The new tests should also skip cleanly when onnxruntime is unavailable.

💬 Posted 2 inline comments

venu-banaras · 2026-06-05T20:59:10Z

I have read the CLA Document and I sign the CLA

codecov · 2026-06-05T20:59:23Z

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ultralytics/nn/tasks.py	25.00%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

UltralyticsAssistant

🔍 PR Review 2

_{Made with ❤️ by Ultralytics Actions}

The names fallback change looks directionally good and the new ONNX coverage helps, but there are two issues to address before merging: the TensorRT end-to-end compatibility logic regresses for non-INT8 engine exports, and the added tests still miss the new exception-driven fallback path they are meant to protect.

💬 Posted 2 inline comments

venu-banaras · 2026-06-06T18:43:29Z

@glenn-jocher Kindly review. I was finally able to solve my original idea of legacy checkpoint fallback during ONNX export for names.

glenn-jocher · 2026-06-07T07:49:07Z

Thanks for the update — using Model.names as the legacy fallback for export looks like the right direction; please keep this PR scoped to that exporter fix plus the regression test, and move the broader check_class_names() or class-count inference ideas to a separate PR.

venu-banaras · 2026-06-07T08:50:44Z

Yes those ideas will be separate PRs. this one is only checking if names is missing or None type or malformed, and fixes them. These 2 further improvement ideas would be follow-ups to this PR, only when this PR is approved.

glenn-jocher · 2026-06-08T03:06:33Z

Thanks for confirming — keeping this PR limited to the exporter-side fallback for missing or invalid names plus the regression test is the right scope.

venu-banaras · 2026-06-08T03:36:41Z

yes. now just waiting for feedback on my code...

glenn-jocher · 2026-06-08T12:42:21Z

Thanks, noted — a maintainer will review the code when available; for now, please keep the PR unchanged unless you need to address CI or a clearly reproducible edge case.

Keep check_class_names() validation errors loud instead of catching them, guard non-dict model.yaml, and drop the default_class_names import.

github-actions · 2026-09-04T00:32:04Z

👋 Hello there! We wanted to let you know that we've decided to close this pull request due to inactivity. We appreciate the effort you put into contributing to our project, but unfortunately, not all contributions are suitable or aligned with our product roadmap.

We hope you understand our decision, and please don't let it discourage you from contributing to open source projects in the future. We value all of our community members and their contributions, and we encourage you to keep exploring new projects and ways to get involved.

For additional resources and information, please see the links below:

Docs: https://docs.ultralytics.com
Platform: https://platform.ultralytics.com/ultralytics/yolo26
Community: https://community.ultralytics.com

Thank you for your contributions to YOLO 🚀 and Vision AI ⭐

legacy names fallback for older checkpoints

d0a85ba

UltralyticsAssistant added bug Something isn't working as intended in the official Ultralytics package. exports Model exports (ONNX, TensorRT, TFLite, etc.) python Pull requests that update python code labels Jun 5, 2026

UltralyticsAssistant reviewed Jun 5, 2026

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Merge branch 'main' into idea/onnx_legacy_names_fallback

c3f7750

venu-banaras requested a review from UltralyticsAssistant June 6, 2026 15:28

UltralyticsAssistant reviewed Jun 6, 2026

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Comment thread ultralytics/engine/exporter.py Outdated

Comment thread tests/test_onnx_legacy_names.py Outdated

cover case for sparse keys and onnx not present in test env

3d4ff62

glenn-jocher changed the title ~~Legacy names fallback for older checkpoints~~ Add class names fallback for legacy checkpoints on export Jul 5, 2026

glenn-jocher and others added 3 commits July 26, 2026 21:05

Merge main into idea/onnx_legacy_names_fallback

1444ce2

Auto-format by https://ultralytics.com/actions

e97932a

Merge branch 'main' into idea/onnx_legacy_names_fallback

88bf14b

glenn-jocher closed this Jul 30, 2026

glenn-jocher reopened this Jul 30, 2026

glenn-jocher added 6 commits August 20, 2026 02:19

Merge branch 'main' into idea/onnx_legacy_names_fallback

718227d

Normalize legacy class names during checkpoint load

7070a5d

Merge remote-tracking branch 'origin/main' into HEAD

7522d48

Merge remote-tracking branch 'origin/main' into pr-24715

c0e6cbc

Warn when falling back to default class names on checkpoint load

174d446

Merge remote-tracking branch 'origin/main' into pr24715

7d2524b

Fall back to default class names only when checkpoint names are missing

837ba7e

Keep check_class_names() validation errors loud instead of catching them, guard non-dict model.yaml, and drop the default_class_names import.

github-actions Bot added the Stale Stale and schedule for closing soon label Sep 4, 2026

Merge branch 'main' into idea/onnx_legacy_names_fallback

8c5a502

cainiao33 mentioned this pull request Sep 13, 2026

Warn on empty class name strings in check_class_names() #26164

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