diff --git a/src/flow/next-step.ts b/src/flow/next-step.ts
index 602eadf..696d05f 100644
--- a/src/flow/next-step.ts
+++ b/src/flow/next-step.ts
@@ -1,6 +1,6 @@
 import type { RoundStepId, StudyStepId } from "../config/index.ts";
 import type { Content, LedgerRecord } from "../ledger/index.ts";
-import { Board, CELL_NOT_RUN, cellId, experimenterId, factorKey, FORWARD_NOT_RUN, ORIGINAL_BASELINE, researcherId, splitCell, verifierId } from "../materials/index.ts";
+import { Board, CELL_NOT_RUN, cellId, DECISION_KINDS, experimenterId, factorKey, FORWARD_NOT_RUN, ORIGINAL_BASELINE, researcherId, splitCell, verifierId } from "../materials/index.ts";
 import { compareIds, listCells, runBalance, sharedSettings } from "../rules/index.ts";
 import { ablationOutcome, verificationOutcome } from "../submissions/index.ts";
 import { SUBMISSION_KINDS, type Stage, type SubmissionKind } from "../vocab/index.ts";
@@ -113,7 +113,10 @@ function studyStepNext(step: Exclude<StudyStepId, "rounds">, view: View, frozen:
  */
 function roundsNext(view: View, frozen: Frozen): Next | null {
   for (let round = 1; ; round++) {
-    if (runBalance(frozen.config.runs, view.board.runStates()).balance === 0) return null;
+    // 余额为 0 不开【下一轮】；已经开始的轮次照常走完——最后一次正向用掉全部余额时，这一轮的采纳、
+    // 消融（各格记“没测：剩余次数不够”）、收尾与解封照样做（方法.md 第七部分“什么时候开下一轮”）。
+    // 一轮在账本里留下的第一处痕迹是阶段记录（或按配置跳过事件、决定记录），此前这一轮还不算开始。
+    if (!roundStarted(view, round) && runBalance(frozen.config.runs, view.board.runStates()).balance === 0) return null;
     for (const step of frozen.steps.round) {
       const next = step.status === "skip" ? skipNext(stageIdOf(round, step.id), step.reason, view) : roundStepNext(step.id, round, view, frozen);
       if (next !== null) return next;
@@ -121,6 +124,14 @@ function roundsNext(view: View, frozen: Frozen): Next | null {
   }
 }
 
+/** 第 round 轮开始了没有：看账本里有没有这一轮的阶段、跳过事件或决定。 */
+function roundStarted(view: View, round: number): boolean {
+  const prefix = `r${round}-`;
+  if ([...view.board.stages.keys()].some((id) => id.startsWith(prefix))) return true;
+  if (DECISION_KINDS.some((kind) => view.board.decision(kind, round) !== undefined)) return true;
+  return view.events(EVENTS.skipped).some((e) => typeof e.objects[0] === "string" && e.objects[0].startsWith(prefix));
+}
+
 /** 第 round 轮的一个要执行的步骤还要做什么；做完了交回 null。 */
 function roundStepNext(step: RoundStepId, round: number, view: View, frozen: Frozen): Next | null {
   switch (step) {
diff --git a/tests/flow-next-step.test.ts b/tests/flow-next-step.test.ts
index 4eebe8b..c1fb41a 100644
--- a/tests/flow-next-step.test.ts
+++ b/tests/flow-next-step.test.ts
@@ -652,6 +652,22 @@ test("结算和押的因子写完：开收尾；收尾关闭后解封本轮选
   assert.deepEqual(nextStep(book.records), { do: "openStage", stageId: "r2-proposal", stage: "proposal", round: 2, roster: R });
 });
 
+test("最后一次正向用掉全部余额：进行中的这一轮照常走完采纳与收尾，不开下一轮", () => {
+  // 复现 full17-b 第 5 轮的缺陷：两个正向运行把余额用到 0 后，采纳决定、收尾和解封被整轮跳过，
+  // 直接走到导出停下。余额为 0 只是不开【下一轮】（方法.md 第七部分“什么时候开下一轮”）。
+  const book = firstVerification(batchTwo(1), true, true);
+  for (const c of C) recordForward(book, c, 1, "valid");
+  // 已扣 3 次（基线 1、正向 2）：把冻结配置的运行次数改成 3，余额为 0。
+  const record = book.records.find((r) => r.kind === "config")!;
+  const study = record.content as unknown as StudyRecord;
+  study.config = { ...fullConfig(), runs: 3 } as unknown as Json;
+  // 这一轮已经开始（r1- 的阶段都在账上）：下一步是写采纳决定，不是停下。
+  assert.deepEqual(nextStep(book.records), { do: "adopt", round: 1 });
+  book.add("decision", { decision: "adopt", round: 1, rule: "adopt", ruleVersion: 1, params: null, seed: null, input: null, output: { adopted: null } });
+  // 没有采纳：不做消融，照样开收尾阶段。
+  assert.deepEqual(nextStep(book.records), { do: "openStage", stageId: "r1-wrapUp", stage: "wrapUp", round: 1, roster: R });
+});
+
 test("余额为 0：不开下一轮，走到导出停下，原因写明", () => {
   const book = afterWrapUp();
   book.add("unseal", { candidate: "r1-c1", seals: [1] });