Fix acknowledgment tweet link

README.md

@@ -13,7 +13,7 @@ datasets:
 
 # Qwen3-0.6B Fine-tuned on Codeforces-CoTS (Python)
 
-Reproduction of [Ben Burtenshaw's HuggingFace fine-tuning challenge](https://x.com/ben_burtenshaw/status/1871606555461214584) (Claude Code vs Codex). Fine-tuned using SFT on the **solutions_py** subset of `open-r1/codeforces-cots`.
+Reproduction of [Ben Burtenshaw's HuggingFace fine-tuning challenge](https://x.com/ben_burtenshaw/status/1999502002251006449) (Claude Code vs Codex). Fine-tuned using SFT on the **solutions_py** subset of `open-r1/codeforces-cots`.
 
 ## Results on HumanEval
 
@@ -93,4 +93,4 @@ Most time was spent on infrastructure debugging, not ML.
 
 ## Acknowledgments
 
-Based on [Ben Burtenshaw's challenge](https://x.com/ben_burtenshaw/status/1871606555461214584) comparing Claude Code vs Codex for fine-tuning tasks.
+Based on [Ben Burtenshaw's challenge](https://x.com/ben_burtenshaw/status/1999502002251006449) comparing Claude Code vs Codex for fine-tuning tasks.