https://nalar.dev/tags/model-diagnostics/ Recent content in Model Diagnostics on Nalar Hugo en-us Mon, 01 Jan 0001 00:00:00 +0000 https://nalar.dev/inspect-transformer-residual-streams-with-the-logit-lens/ Fri, 11 Sep 2026 00:00:00 +0700 https://nalar.dev/inspect-transformer-residual-streams-with-the-logit-lens/ <h1 id="inspect-transformer-residual-streams-with-the-logit-lens">Inspect Transformer Residual Streams with the Logit Lens</h1> <p>A language model returns token probabilities only after its final transformer block, but developers often need to inspect what happens before that point. A prompt may produce an unexpected completion, a fine-tuned checkpoint may behave differently from its base model, or a model modification may alter predictions several blocks before the final output.</p> <p>The <strong>logit lens</strong> is a simple diagnostic for these cases. It takes an intermediate residual-stream vector, maps it through the model&rsquo;s output machinery, and ranks vocabulary tokens as if that intermediate state were already ready for prediction.</p>