fix: Stop LTXVCropGuides leaving stray latent frames when guides share a start position (CORE-206)

[drozbay]

When two LTXVAddGuide nodes target the same starting frame, LTXVCropGuides undercounts the guide frames it added and leaves one stray latent frame behind. That frame decodes as a visible artifact at the end of the generated video.

Here is an example workflow to show this. The input latent has 17 frames and 2 LTXVAddGuide nodes, both adding a single image to index 0.
droz_CORE206_guide_frame_miscount_example2.json

Before fix - Output has extra latent after incorrect CropGuide, resulting in 8 extra frames:

After fix - Properly trimmed latent, correct number of frames

The CropGuides cleanup step was counting guide frames by looking at distinct starting positions in the conditioning. That works as long as no two guides share a start, but undercounts as soon as they do. The fix uses token data instead, which doesn't have that ambiguity, and threads the count to the three places that consume it.

I think that the bug has been around since LTXV 0.9.5 in March 2025. It just doesn't surface unless guides overlap on a starting frame.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR enhances keyframe index and count computation by making it shape-aware. The utility function get_keyframe_idxs now accepts optional latent shape information and uses it to derive accurate token-per-frame counts. When shape is unavailable, it falls back to metadata from guide attention entries. All call sites in LTXVAddGuide.execute and LTXVCropGuides.execute now pass the latent image shape to enable this shape-aware behavior throughout the keyframe resolution system.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix: preventing LTXVCropGuides from leaving stray latent frames when guides share a start position.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description clearly describes the bug fix for LTXVCropGuides undercounting guide frames when multiple guides share a starting frame, with concrete examples and before/after images.

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@comfy_extras/nodes_lt.py`:
- Around line 195-198: The current code assumes every item in
conditioning_get_any_value(cond, "guide_attention_entries", None) has a
"latent_shape" key which can raise KeyError and skip the fallback; update the
parsing to only include entries that have a valid "latent_shape" (e.g.,
"latent_shape" in e and e["latent_shape"] and isinstance(e["latent_shape"][0],
int)) when computing num_keyframes, compute num_keyframes =
sum(e["latent_shape"][0] for e in entries_filtered), and only return
keyframe_idxs, num_keyframes if that sum is > 0 (otherwise do not return so the
original fallback behavior continues). Ensure you reference
conditioning_get_any_value, guide_attention_entries, latent_shape, keyframe_idxs
and num_keyframes in your change.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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📒 Files selected for processing (1)

• comfy_extras/nodes_lt.py