Update session notes with completion status

Author: jeremymanning

notes/2026-02-12-week7-diffusion-rewrite.md

@@ -1,23 +1,34 @@
 # Week 7 Diffusion Rewrite — Session Notes (2026-02-12)
 
-## Status
-Replacing Week 7 from "GPT/Decoder Models" to "Diffusion Models".
+## Status: COMPLETE
+Replaced Week 7 from "GPT/Decoder Models" to "Diffusion Models".
+Commit: `721d55a` — pushed to main.
 
-## Completed (committed)
-- Cross-reference updates: lecture20.md, lecture27.md, README.md, syllabus.md (uncommitted changes from prior session)
-- Animation infrastructure: render_gifs.py, postprocess_gifs.py, requirements.txt, README.md (uncommitted new files)
+## What was done
+1. **Three new lectures** written from scratch:
+   - lecture21.md (446 lines, ~27 slides): Diffusion architecture deep-dive
+   - lecture22.md (357 lines, ~19 slides): Extensions (latent diffusion, CFG, DiT, flow matching)
+   - lecture23.md (393 lines, ~20 slides): Applications & ethics (DALL-E 2, Sora, MDLM, deepfakes)
 
-## In Progress (background tasks)
-All 4 content files are being generated by background agents:
+2. **10 Manim animation GIFs** rendered (diffusion_scenes.py, 1113 lines):
+   - forwarddiffusion.gif, noiseschedule.gif, reverseprocess.gif, unetarchitecture.gif
+   - timestepembedding.gif, trainingobjective.gif, simplifiedloss.gif
+   - scorematching.gif, samplingprocess.gif, diffusionvstransformer.gif
 
-| Task ID | File | Agent | Session ID |
-|---------|------|-------|------------|
-| bg_55690b17 | lecture21.md (diffusion architecture) | deep | ses_3abe4e6ccffeIxuC41mJgn0fb9 |
-| bg_66ef8d46 | lecture22.md (extensions) | deep | ses_3abe480feffeANUy7UfoxJ9QLd |
-| bg_4ba2b2b4 | lecture23.md (applications/ethics) | deep | ses_3abe4148affeNSF9u0KPz5qPvA |
-| bg_45dcd847 | diffusion_scenes.py (10 Manim scenes) | ultrabrain | ses_3abe320d3ffepDE9jAj9uyQEh8 |
+3. **Companion notebook**: diffusion_demo.ipynb (5 parts: forward process, toy denoiser, HuggingFace Diffusers, guidance, discussion)
 
-## Remaining after content creation
+4. **Cross-reference updates**:
+   - slides/week6/lecture20.md: "Up next" box updated
+   - slides/week10/lecture27.md: Review table row updated
+   - slides/README.md: Week 7 section replaced
+   - admin/syllabus.md: Overview table + detailed schedule updated
+
+5. **All 3 lectures compiled** to HTML + PDF
+6. **All 1500+ existing tests pass**
+
+## Files changed (288 files, 7343 insertions, 2192 deletions)
+
+## Previous commits in this effort
 1. Create diffusion_demo.ipynb companion notebook
 2. Render Manim GIFs (requires manim venv)
 3. Compile all 3 lectures with compile.sh