test(confidence-engine): expose reconstruction experiment seam

lib/analysis.js

@@ -53,10 +53,15 @@ export async function analyseScenario(scenario, opts = {}) {
   const { OLLAMA_BASE_URL: _ignored, OLLAMA_MODEL } = configResult.config;
   const promptVersion = opts.promptVersion || DEFAULT_PROMPT_VERSION;
 
-  // ── Build prompt ───────────────────────────────────
+  // ── Build prompt (experiment seam via env var bridge) ──
   let promptObj;
   try {
-    promptObj = await buildPrompt(trimmed, promptVersion);
+    const experimentInstruction = process.env.RECONSTRUCTION_EXPERIMENT_INSTRUCTION;
+    const buildOpts = {};
+    if (experimentInstruction) {
+      buildOpts.experimentInstruction = experimentInstruction;
+    }
+    promptObj = await buildPrompt(trimmed, promptVersion, buildOpts);
   } catch (e) {
     return buildErrorResponse(
       `Failed to build prompt: ${e.message}`,

lib/reconstruction/prompt.js

@@ -79,10 +79,13 @@ async function buildV3Prompt(scenario) {
 
 /**
  * Build an analysis prompt for the given version.
- * @param {"v0.1" | "v0.2" | "v0.3"} [version="v0.3"]
+ * @param {string} scenario - The scenario text
+ * @param {"v0.1" | "v0.2" | "v0.3"} [version="v0.3"] - Prompt version
+ * @param {object} [opts] - Optional experimental parameters
+ * @param {string} [opts.experimentInstruction] - Bounded experimental instruction block appended to the base prompt (production prompt is never replaced)
  * @returns {Promise<{prompt: string, version: string}>}
  */
-export async function buildPrompt(scenario, version = "v0.3") {
+export async function buildPrompt(scenario, version = "v0.3", opts = {}) {
   let prompt;
   switch (version) {
     case "v0.1":
@@ -98,5 +101,15 @@ export async function buildPrompt(scenario, version = "v0.3") {
 
   const strongJsonHint =
     "\n\nReturn ONLY a valid JSON object starting with { and ending with }. Do NOT include any text before the opening brace or after the closing brace. Do NOT wrap in markdown backticks.";
-  return { prompt: prompt + strongJsonHint, version };
+
+  // ── Experiment seam: append optional instruction block ──
+  let finalPrompt = prompt;
+  if (opts.experimentInstruction) {
+    const delimiter = "\n\n--- EXPERIMENT INSTRUCTION ---\n";
+    finalPrompt = prompt + delimiter + opts.experimentInstruction + strongJsonHint;
+  } else {
+    finalPrompt = prompt + strongJsonHint;
+  }
+
+  return { prompt: finalPrompt, version };
 }