Fix: Flux.2 reference images presented in random order

[Copilot]

Summary

CollectInvocation items were sorted by (iteration_path, source_node_id) when building the collection. For non-iterated direct connections (the common case for Flux.2 reference images), all items share the same empty iteration path, making the secondary sort fall back to source_node_id — a random UUID — producing non-deterministic ordering on every run.

Fix: Replace source_node_id as the tiebreaker with the edge's insertion index in input_edges. Edges are appended in the order they're added to the graph, which reflects left-to-right visual order from the frontend.

# Before — random order when iteration paths are equal (source_node_id is a UUID)
item_edges.sort(key=lambda e: (self._get_iteration_path(e.source.node_id), e.source.node_id))

# After — ties broken by insertion order, preserving frontend visual order
item_edges_indexed = list(enumerate(e for e in input_edges if e.destination.field == ITEM_FIELD))
item_edges_indexed.sort(key=lambda t: (self._get_iteration_path(t[1].source.node_id), t[0]))
item_edges = [e for _, e in item_edges_indexed]

Related Issues / Discussions

QA Instructions

1. Set up a Flux.2 Klein generation with 3+ reference images arranged left-to-right (e.g. labeled A, B, C).
2. Use a prompt that refers to images by position (e.g. "image 1", "image 2").
3. Run multiple generations and confirm the reference images are consistently passed to the denoiser in the same left-to-right order.

Merge Plan

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

Original prompt

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This section details on the original issue you should resolve

<issue_title>[bug]: Flux.2 reference images are presented in random order</issue_title>
<issue_description>### Is there an existing issue for this problem?

• I have searched the existing issues

Install method

Invoke's Launcher

Operating system

Linux

GPU vendor

Nvidia (CUDA)

GPU model

No response

GPU VRAM

No response

Version number

main branch

Browser

No response

System Information

No response

What happened

When using the Flux.2 Klein models, which accept more than one reference image, the reference images seem to be presented to the denoiser in random order. That is, if I have images named A, B, C and they are ordered that way from left to right in the frontend's reference image list, the backend sometimes receives A, B, C, sometimes C, A, B, and so forth. This makes it impossible to refer to each image by its order in the way that's documented, such as "image 1"

What you expected to happen

I expect the images to be presented to the conditioning and denoising steps in exactly the order they appear in the frontend, ordered from left to right.

How to reproduce the problem

No response

Additional context

No response

Discord username

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [bug]: Flux.2 reference images are presented in random order #95

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