test(ui): explore branch as workspace context

components/reasoning-workspace.jsx

@@ -521,6 +521,7 @@ export default function ReasoningWorkspace({
   onAnswerSubmit,
   lastSubmittedAnswer,
   onRestart,
+  branchContext,
 }) {
   const [investigationHistory, setInvestigationHistory] = useState([]);
   const turnCounter = useRef(0);
@@ -823,6 +824,21 @@ export default function ReasoningWorkspace({
             <div className="grid grid-cols-1 gap-6 lg:grid-cols-3">
               {/* ── Left lane: active conversation & notebook ───────── */}
               <div className="space-y-6 lg:col-span-2">
+                {/* Active branch context (experiment RTO.25D) */}
+                {branchContext && hasGraph && (
+                  <div className="rounded-lg border border-blue-200/60 bg-blue-50/40 px-5 py-4">
+                    <h2 className="mb-1 text-[11px] font-semibold tracking-widest uppercase text-gray-500">
+                      Current branch
+                    </h2>
+                    <p className="text-base font-medium leading-tight text-gray-900">{branchContext.label}</p>
+                    {branchContext.origin && (
+                      <p className="mt-2 text-sm leading-relaxed text-gray-600">
+                        Trying to understand: {branchContext.origin}
+                      </p>
+                    )}
+                  </div>
+                )}
+
                 {/* ── Open questions (case workspace) — no ranking bias ── */}
                 {(() => {
                   const openNodes = graph.nodes.filter(
@@ -1104,9 +1120,9 @@ export default function ReasoningWorkspace({
                 {hasCurrentSummaryCondition && (
                   <>
                     <CurrentUnderstandingCard currentSummary={graph?.currentSummary || result?.updatedSituationGraph?.currentSummary} plainLanguage={propUnderstanding || null} />
-                    {/* ── Experiment 12: progress panel A / B / C toggle (temporary experimental UI) ── */}
+                    {/* ── Experiment 12: progress panel A / B / C toggle (temporary experimental UI) — de-emphasised by branch-as-context experiment RTO.25D */}
                     {hasGraph && (
-                      <div className="space-y-2">
+                      <div className="hidden space-y-2">
                         <div className="flex items-center gap-2" role="radiogroup" aria-label="Progress panel variant">
                           <button
                             role="radio"

components/scenario-form.jsx

@@ -543,24 +543,30 @@ export default function ScenarioForm() {
           <div className="grid grid-cols-1 gap-6 lg:grid-cols-4">
             {/* Workspace (3/4) */}
             <div className="lg:col-span-3">
-              <ReasoningWorkspace
+              {/* Build branch context for the active branch */}
-                scenario={scenario}
+              {(() => {
-                status={status}
+                const activeBranch = BRANCHES.find(b => b.id === activeBranchId);
-                updateStatus={updateStatus}
+                const branchContext = activeBranch ? { label: activeBranch.label, origin: activeBranch.origin } : null;
-                currentUnderstanding={currentUnderstanding}
+                return (
-                result={{
+                  <ReasoningWorkspace
-                  ...(result || {}),
+                    scenario={scenario}
-                  situationGraph: updateResult?.updatedSituationGraph ?? result?.situationGraph,
+                    status={status}
-                  selectedQuestion: updateResult?.selectedQuestion ?? result?.selectedQuestion,
+                    updateStatus={updateStatus}
-                  newlySurfacedNodeIds: result?.newlySurfacedNodeIds || [],
+                    currentUnderstanding={currentUnderstanding}
-                  diagnostics: result?.diagnostics || null,
+                    result={{
-                  updateError,
+                      ...(result || {}),
-                }}
+                      situationGraph: updateResult?.updatedSituationGraph ?? result?.situationGraph,
-                answer={answer}
+                      selectedQuestion: updateResult?.selectedQuestion ?? result?.selectedQuestion,
-                setAnswer={setAnswer}
+                      newlySurfacedNodeIds: result?.newlySurfacedNodeIds || [],
-                onAnswerSubmit={handleUpdate}
+                      diagnostics: result?.diagnostics || null,
-                lastSubmittedAnswer={lastSubmittedAnswer}
+                      updateError,
-                onRestart={() => {
+                    }}
+                    answer={answer}
+                    setAnswer={setAnswer}
+                    onAnswerSubmit={handleUpdate}
+                    lastSubmittedAnswer={lastSubmittedAnswer}
+                    branchContext={branchContext}
+                    onRestart={() => {
                   clearSession();
                   setStatus("idle");
                   setResult(null);
@@ -572,7 +578,9 @@ export default function ScenarioForm() {
                   setUpdateError(null);
                 }}
               />
-            </div>
+            );
+          })()}
+        </div>
 
             {/* Branch switcher (1/4 sidebar) */}
             <div className="lg:col-span-1">