Dv/cpu image bringup report

docs/upstream_cpu_image_report_draft.md

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+# CPU image generation now demonstrated end to end
+
+## Summary
+
+This note documents a successful CPU demonstration for `bonsai-image` on the unpacked transformer path.
+
+The headline result is straightforward: CPU image generation can produce coherent `128x128` outputs end to end.
+
+The two clearest examples are:
+
+- a coherent plain `ostrich`
+- a clean 4-quadrant multi-color layout
+
+Additional validated outputs include:
+
+- a coherent ostrich silhouette
+- a large centered red circle
+- the same plain `ostrich` result in repeated successful runs
+
+That establishes three concrete facts:
+
+1. the unpacked CPU path can converge on globally coherent images
+2. both geometric and object-level prompts can work on CPU
+3. `128x128` is a practical resolution for validating CPU image generation behavior
+
+This is not a full root-cause fix report for every failure mode. It is a status report showing that CPU image generation is real, reproducible, and already capable of meaningful outputs.
+
+## Demonstrated capability
+
+For this pipeline:
+
+- `64x64` corresponds to a `4x4` packed latent grid
+- `128x128` corresponds to an `8x8` packed latent grid
+
+On the unpacked transformer CPU path, `128x128` was sufficient to demonstrate:
+
+- global composition across many packed tokens
+- successful convergence on simple object prompts
+- successful convergence on large centered shapes
+- successful convergence on structured color layouts
+
+## Validated `128x128` outputs
+
+On the CPU path using the unpacked transformer, these `128x128`, `4-step` prompts converged coherently:
+
+- plain `ostrich`
+- `a large red circle centered on a pure white background, filling most of the image, flat solid color, hard clean edge, no other objects, minimalist`
+- `a large black silhouette of an ostrich centered on a pure white background, full body, hard clean edge, minimalist, no other objects`
+- a 4-quadrant color layout prompt
+
+## Suggested upstream guidance
+
+It may help to document the following as the current practical CPU guidance:
+
+1. Use `128x128+` for structure/composition validation.
+2. Treat final outputs as the primary correctness signal.
+3. Use the unpacked transformer CPU path as a reference-capable configuration for image bring-up.
+
+## Runner-side settings that matched successful runs
+
+Two runner-side settings were helpful in the successful CPU runs:
+
+1. Increasing default prompt context from `64` to `512`
+2. Using `128x128` instead of `64x64` for meaningful structure/composition validation
+
+## Reproduction shape
+
+Example command shape used for successful CPU runs:
+
+```bash
+python scripts/generate_cpu_experimental.py \
+  --prompt 'ostrich' \
+  --output outputs/cpu-ostrich.png \
+  --height 128 \
+  --width 128 \
+  --steps 4 \
+  --seed 7 \
+  --transformer-dir models/bonsai-image-4B-ternary-unpacked/transformer
+```
+
+## Example output categories
+
+- plain ostrich
+- ostrich silhouette
+- large centered red circle
+- 4-quadrant color layout
+
+## Notes
+
+- This note intentionally avoids host-specific details, private paths, tokens, and unrelated local setup details.
+- If a PR is not the right venue, the same content could be posted as an issue or discussion instead.

docs/upstream_issue_cpu_bringup.md

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+# CPU image generation works end to end on unpacked path at 128x128
+
+## Summary
+
+CPU image generation is working end to end on the unpacked transformer path at `128x128`.
+
+The clearest validated outputs were:
+
+- plain `ostrich`
+- a clean 4-quadrant multi-color layout
+- a large centered red circle
+- a coherent ostrich silhouette
+
+This is useful because it establishes that the CPU path can already do:
+
+- globally coherent composition
+- structured color layouts
+- simple object-level prompts
+
+## Key evidence
+
+Validated `128x128`, `4-step` outputs:
+
+- `ostrich`
+- `a large red circle centered on a pure white background, filling most of the image, flat solid color, hard clean edge, no other objects, minimalist`
+- `a large black silhouette of an ostrich centered on a pure white background, full body, hard clean edge, minimalist, no other objects`
+- a 4-quadrant color layout prompt
+
+## Practical CPU guidance
+
+Two practical constraints stood out during bring-up:
+
+1. `64x64` is a poor structure/composition validation target for this pipeline.
+2. Final outputs are much more reliable than intermediate-step VAE decodes when judging correctness.
+
+At this resolution regime:
+
+- `64x64` corresponds to a `4x4` packed latent grid
+- `128x128` corresponds to an `8x8` packed latent grid
+
+Using `128x128` made the difference between misleading geometry tests and meaningful validation.
+
+## Reproduction shape
+
+Example command shape used for successful CPU runs:
+
+```bash
+python scripts/generate_cpu_experimental.py \
+  --prompt 'ostrich' \
+  --output outputs/cpu-ostrich.png \
+  --height 128 \
+  --width 128 \
+  --steps 4 \
+  --seed 7 \
+  --transformer-dir models/bonsai-image-4B-ternary-unpacked/transformer
+```
+
+## Suggested takeaway
+
+The unpacked CPU path appears good enough to document as a real bring-up configuration for `bonsai-image`, at least for `128x128` validation and simple-to-moderate image composition.