fix(gsd): preserve auto start model through discuss (#2837)

src/resources/extensions/gsd/auto-start.ts

@@ -131,6 +131,15 @@ export async function bootstrapAutoSession(
     return false;
   }
 
+  // Capture the user's session model before guided-flow dispatch can apply a
+  // phase-specific planning model for a discuss turn (#2829).
+  const startModelSnapshot = ctx.model
+    ? {
+        provider: ctx.model.provider,
+        id: ctx.model.id,
+      }
+    : null;
+
   try {
     // Validate GSD_PROJECT_ID early so the user gets immediate feedback
     const customProjectId = process.env.GSD_PROJECT_ID;
@@ -576,12 +585,11 @@ export async function bootstrapAutoSession(
     // Initialize routing history
     initRoutingHistory(s.basePath);
 
-    // Capture session's model at auto-mode start (#650)
-    const currentModel = ctx.model;
-    if (currentModel) {
+    // Restore the model that was active when auto bootstrap began (#650, #2829).
+    if (startModelSnapshot) {
       s.autoModeStartModel = {
-        provider: currentModel.provider,
-        id: currentModel.id,
+        provider: startModelSnapshot.provider,
+        id: startModelSnapshot.id,
       };
     }
 

src/resources/extensions/gsd/tests/auto-start-model-capture.test.ts

@@ -0,0 +1,28 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+const sourcePath = join(import.meta.dirname, "..", "auto-start.ts");
+const source = readFileSync(sourcePath, "utf-8");
+
+test("bootstrapAutoSession snapshots ctx.model before guided-flow entry (#2829)", () => {
+  const snapshotIdx = source.indexOf("const startModelSnapshot = ctx.model");
+  assert.ok(snapshotIdx > -1, "auto-start.ts should snapshot ctx.model at bootstrap start");
+
+  const firstDiscussIdx = source.indexOf('await showSmartEntry(ctx, pi, base, { step: requestedStepMode });');
+  assert.ok(firstDiscussIdx > -1, "auto-start.ts should route through showSmartEntry during guided flow");
+
+  assert.ok(
+    snapshotIdx < firstDiscussIdx,
+    "auto-start.ts must capture the start model before guided-flow can mutate ctx.model",
+  );
+});
+
+test("bootstrapAutoSession restores autoModeStartModel from the early snapshot (#2829)", () => {
+  const assignmentIdx = source.indexOf("s.autoModeStartModel = {");
+  assert.ok(assignmentIdx > -1, "auto-start.ts should assign autoModeStartModel");
+
+  const snapshotRefIdx = source.indexOf("provider: startModelSnapshot.provider", assignmentIdx);
+  assert.ok(snapshotRefIdx > -1, "autoModeStartModel should be restored from startModelSnapshot");
+});