Fix app stream/timeline ordering desync and init lifecycle race (#73)

* fix(app): enforce canonical stream sequencing and init resolution * refactor: extract timeline and stream reducers to pure functions
2026-02-23 19:30:48 +07:00
parent 9b6f5e028c
commit a134132418
12 changed files with 1732 additions and 109 deletions
@@ -0,0 +1,108 @@
+import { describe, expect, it } from "vitest";
+import { classifySessionTimelineSeq } from "./session-timeline-seq-gate";
+import {
+  deriveBootstrapTailTimelinePolicy,
+  shouldResolveTimelineInit,
+} from "./session-timeline-bootstrap-policy";
+
+describe("deriveBootstrapTailTimelinePolicy", () => {
+  it("always replaces on explicit reset without catch-up cursor", () => {
+    const policy = deriveBootstrapTailTimelinePolicy({
+      direction: "after",
+      reset: true,
+      epoch: "epoch-1",
+      endCursor: { seq: 200 },
+      isInitializing: false,
+      hasActiveInitDeferred: false,
+    });
+
+    expect(policy.replace).toBe(true);
+    expect(policy.catchUpCursor).toBeNull();
+  });
+
+  it("forces baseline replace and canonical catch-up for init tail race", () => {
+    const advancedCursor = { epoch: "epoch-1", endSeq: 205 };
+    const tailSeqStart = 101;
+    const tailSeqEnd = 200;
+
+    let acceptedWithoutBootstrap = 0;
+    for (let seq = tailSeqStart; seq <= tailSeqEnd; seq += 1) {
+      const decision = classifySessionTimelineSeq({
+        cursor: advancedCursor,
+        epoch: "epoch-1",
+        seq,
+      });
+      if (decision === "accept" || decision === "init") {
+        acceptedWithoutBootstrap += 1;
+      }
+    }
+    expect(acceptedWithoutBootstrap).toBe(0);
+
+    const policy = deriveBootstrapTailTimelinePolicy({
+      direction: "tail",
+      reset: false,
+      epoch: "epoch-1",
+      endCursor: { seq: 200 },
+      isInitializing: true,
+      hasActiveInitDeferred: true,
+    });
+
+    expect(policy.replace).toBe(true);
+    expect(policy.catchUpCursor).toEqual({
+      epoch: "epoch-1",
+      endSeq: 200,
+    });
+  });
+
+  it("does not replace non-bootstrap, non-reset responses", () => {
+    const policy = deriveBootstrapTailTimelinePolicy({
+      direction: "tail",
+      reset: false,
+      epoch: "epoch-1",
+      endCursor: { seq: 200 },
+      isInitializing: false,
+      hasActiveInitDeferred: false,
+    });
+
+    expect(policy.replace).toBe(false);
+    expect(policy.catchUpCursor).toBeNull();
+  });
+});
+
+describe("shouldResolveTimelineInit", () => {
+  it("resolves tail init when the tail response arrives", () => {
+    expect(
+      shouldResolveTimelineInit({
+        hasActiveInitDeferred: true,
+        isInitializing: true,
+        initRequestDirection: "tail",
+        responseDirection: "tail",
+        reset: false,
+      })
+    ).toBe(true);
+  });
+
+  it("does not resolve tail init when an after response arrives first", () => {
+    expect(
+      shouldResolveTimelineInit({
+        hasActiveInitDeferred: true,
+        isInitializing: true,
+        initRequestDirection: "tail",
+        responseDirection: "after",
+        reset: false,
+      })
+    ).toBe(false);
+  });
+
+  it("resolves after init when an after response arrives", () => {
+    expect(
+      shouldResolveTimelineInit({
+        hasActiveInitDeferred: true,
+        isInitializing: true,
+        initRequestDirection: "after",
+        responseDirection: "after",
+        reset: false,
+      })
+    ).toBe(true);
+  });
+});