fix: harden dynamic rectification protocol

frontend/src/lib/birth-time-dynamic-stop-policy.ts

@@ -1,19 +1,20 @@
 import type { CandidateResult } from "./birth-time-evidence.ts";
 
 export type DynamicStopInput = {
-  readonly result: CandidateResult;
+  readonly result: CandidateResult | null;
   readonly effectiveAnswer: boolean;
   readonly previousResult: CandidateResult | null;
   readonly priorPlateauCount: number;
   readonly usefulOpportunityCount: number;
   readonly repeatedOnly: boolean;
   readonly effectiveAnswerCount: number;
+  readonly forcedReason: "user_finished" | "generation_unavailable" | null;
 };
 
 export type DynamicStopDecision =
   | {
     readonly kind: "finish";
-    readonly reason: "high_confidence" | "safety_cap" | "plateau" | "no_information_gain" | "repeated_partition";
+    readonly reason: "user_finished" | "generation_unavailable" | "high_confidence" | "safety_cap" | "plateau" | "no_information_gain" | "repeated_partition";
     readonly plateauCount: number;
   }
   | { readonly kind: "continue"; readonly plateauCount: number };
@@ -34,10 +35,11 @@ export function materiallyChanged(
 }
 
 export function decideDynamicStop(input: DynamicStopInput): DynamicStopDecision {
-  const plateauCount = input.effectiveAnswer
+  const plateauCount = input.effectiveAnswer && input.result !== null
     ? materiallyChanged(input.previousResult, input.result) ? 0 : input.priorPlateauCount + 1
     : input.priorPlateauCount;
-  if (input.result.confidence === "high") return { kind: "finish", reason: "high_confidence", plateauCount };
+  if (input.forcedReason !== null) return { kind: "finish", reason: input.forcedReason, plateauCount };
+  if (input.result?.confidence === "high") return { kind: "finish", reason: "high_confidence", plateauCount };
   if (input.effectiveAnswerCount >= 10) return { kind: "finish", reason: "safety_cap", plateauCount };
   if (plateauCount >= 2) return { kind: "finish", reason: "plateau", plateauCount };
   if (input.usefulOpportunityCount === 0) return { kind: "finish", reason: "no_information_gain", plateauCount };

frontend/src/lib/birth-time-journey-turn-protocol.ts

@@ -81,6 +81,16 @@ export type DynamicJourneyProgress = z.infer<typeof dynamicJourneyProgressSchema
 
 export type { PublicDynamicChoiceQuestion, TimeRange };
 
+export const dynamicJourneyTurnStateSchema = z.object({
+  journeyProtocol: z.literal("dynamic-choice-v2"),
+  turnVersion: z.number().int().nonnegative(),
+  nextAction: dynamicNextActionSchema,
+  progress: dynamicJourneyProgressSchema,
+  permissions: journeyPermissionsSchema,
+}).strict().readonly();
+
+export type DynamicJourneyTurnState = z.infer<typeof dynamicJourneyTurnStateSchema>;
+
 export const journeyTurnStateSchema = z.object({
   turnVersion: z.number().int().nonnegative(),
   nextAction: nextActionSchema,

frontend/src/lib/birth-time-journey-turn.ts

@@ -18,10 +18,12 @@ export {
   questionSpecSchema,
   dynamicJourneyProgressSchema,
   dynamicNextActionSchema,
+  dynamicJourneyTurnStateSchema,
 } from "./birth-time-journey-turn-protocol.ts";
 export type {
   DynamicJourneyProgress,
   DynamicNextAction,
+  DynamicJourneyTurnState,
   EvidenceDraft,
   JourneyPermissions,
   JourneyProgress,

frontend/tests/birth-time-dynamic-choice.test.ts

@@ -4,6 +4,7 @@ import { join } from "node:path";
 import test from "node:test";
 import { publicDynamicChoiceQuestionSchema } from "../src/lib/birth-time-dynamic-choice.ts";
 import { persistedDynamicChoiceQuestionSchema } from "../src/lib/birth-time-dynamic-choice-internal.ts";
+import { dynamicJourneyTurnStateSchema, journeyTurnStateSchema } from "../src/lib/birth-time-journey-turn-protocol.ts";
 
 const internalQuestion = {
   questionId: "11111111-1111-4111-8111-111111111111",
@@ -133,3 +134,42 @@ test("public code never imports the internal dynamic choice contract", () => {
     assert.equal(readFileSync(path, "utf8").includes("birth-time-dynamic-choice-internal"), false, path);
   }
 });
+
+test("dynamic turn state is explicitly discriminated from the legacy protocol", () => {
+  const dynamicTurn = {
+    journeyProtocol: "dynamic-choice-v2",
+    turnVersion: 0,
+    nextAction: { kind: "generate_dynamic_question" },
+    progress: {
+      phase: "question",
+      answeredCount: 0,
+      effectiveAnswerCount: 0,
+      currentRange: { startTime: "09:00", endTime: "10:00" },
+      previousRange: null,
+      plateauCount: 0,
+    },
+    permissions: { canConfirmCandidate: false },
+  };
+
+  assert.equal(dynamicJourneyTurnStateSchema.safeParse(dynamicTurn).success, true);
+  assert.equal(journeyTurnStateSchema.safeParse(dynamicTurn).success, false);
+  assert.equal(dynamicJourneyTurnStateSchema.safeParse({
+    ...dynamicTurn,
+    journeyProtocol: "legacy-guided-v1",
+  }).success, false);
+  assert.equal(dynamicJourneyTurnStateSchema.safeParse({
+    ...dynamicTurn,
+    nextAction: {
+      kind: "ask_baseline_evidence",
+      question: {
+        questionId: "legacy",
+        phase: "baseline",
+        domain: "career",
+        requestedPrecision: ["year"],
+        allowUnknown: true,
+        purposeCode: "candidate_difference_career",
+        plannerVersion: "candidate-difference-v1",
+      },
+    },
+  }).success, false);
+});

frontend/tests/birth-time-dynamic-stop-policy.test.ts

@@ -34,6 +34,7 @@ function decisionFor(overrides: Partial<Parameters<typeof decideDynamicStop>[0]>
     usefulOpportunityCount: 1,
     repeatedOnly: false,
     effectiveAnswerCount: 1,
+    forcedReason: null,
     ...overrides,
   });
 }
@@ -53,6 +54,7 @@ test("two effective unchanged scores stop without starting another question", ()
     usefulOpportunityCount: 3,
     repeatedOnly: false,
     effectiveAnswerCount: 6,
+    forcedReason: null,
   });
 
   assert.deepEqual(decision, { kind: "finish", reason: "plateau", plateauCount: 2 });
@@ -67,12 +69,15 @@ test("unknown answers do not advance plateau or the effective safety count", ()
     usefulOpportunityCount: 2,
     repeatedOnly: false,
     effectiveAnswerCount: 4,
+    forcedReason: null,
   });
 
   assert.deepEqual(decision, { kind: "continue", plateauCount: 1 });
 });
 
 test("terminal conditions are deterministic", () => {
+  assert.equal(finishReason({ result: null, forcedReason: "user_finished" }), "user_finished");
+  assert.equal(finishReason({ result: null, forcedReason: "generation_unavailable" }), "generation_unavailable");
   assert.equal(finishReason({ result: { ...lowCandidate, confidence: "high", canApply: true, winningSegment: {
     startTime: "09:00", endTime: "09:05", representativeTime: "09:03", widthMinutes: 5,
   }, eventCount: 4, domainCount: 3, marginPercent: 20 } }), "high_confidence");
@@ -81,6 +86,15 @@ test("terminal conditions are deterministic", () => {
   assert.equal(finishReason({ effectiveAnswerCount: 10 }), "safety_cap");
 });
 
+test("forced terminal reasons win over a high-confidence score", () => {
+  assert.equal(finishReason({
+    result: { ...lowCandidate, confidence: "high", canApply: true, winningSegment: {
+      startTime: "09:00", endTime: "09:05", representativeTime: "09:03", widthMinutes: 5,
+    }, eventCount: 4, domainCount: 3, marginPercent: 20 },
+    forcedReason: "user_finished",
+  }), "user_finished");
+});
+
 test("a two point margin change resets the plateau", () => {
   const decision = decisionFor({
     result: { ...mediumCandidate, marginPercent: 17 },