experiment: stabilise conversation and reference lanes

docs/design-evolution-log.md

@@ -393,6 +393,31 @@ Proceed to investigate consistency between the landing experience and investigat
 
 ---
 
+### Experiment 09 — Investigation Rhythm
+
+#### Result
+
+Partially confirmed.
+
+#### What did we learn?
+
+- Moving History directly beneath Response improves the sense of conversational continuity.
+- The sequence Question → Response → History is cognitively coherent.
+- History behaves like the growing notebook of the investigation, not general reference material.
+- Allowing History to span the full workspace breaks the wider spatial model.
+- Situation and Investigation Map should remain stable supporting artefacts rather than moving down as the notebook grows.
+- The conversation needs a dedicated vertical lane.
+
+#### Decision
+
+Keep History directly connected to Response.
+
+Refine the desktop workspace into a stable conversation lane and a stable supporting lane.
+
+Do not rewrite previous experiments.
+
+---
+
 ### Experiment 08 — Consistent Investigation Responses
 
 #### Hypothesis
@@ -429,6 +454,30 @@ Retain consistent input sizing across both contexts.
 
 ---
 
+### Experiment 10 — Stable Conversation Column
+
+#### Hypothesis
+
+A persistent two-thirds conversation column beside a one-third supporting column will allow the investigation notebook to grow without moving the shared reference artefacts.
+
+#### Questions
+
+- Does the left column feel like one continuous investigation?
+- Does History grow naturally beneath Response?
+- Do Situation and Investigation Map remain easy to reference?
+- Does the interface feel spatially stable as turns accumulate?
+- Does showing full question text improve readability now that sufficient width exists?
+
+#### Evaluation
+
+Pending visual review.
+
+#### Status
+
+Experimental.
+
+---
+
 ## Emerging Direction
 
 The first UX experiments focused on workspace structure.