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paseo/packages/app/src/timeline/session-stream-reducers.test.ts
T

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TypeScript

import { describe, expect, it } from "vitest";
import type { AgentStreamEventPayload } from "@server/shared/messages";
import type { StreamItem } from "@/types/stream";
import {
createAgentStreamReducerQueue,
processTimelineResponse,
processAgentStreamEvent,
processAgentStreamEvents,
type ProcessTimelineResponseInput,
type ProcessAgentStreamEventInput,
type AgentStreamReducerEvent,
type TimelineCursor,
} from "./session-stream-reducers";
// ---------------------------------------------------------------------------
// Test helpers
// ---------------------------------------------------------------------------
function makeTimelineEntry(
seq: number,
text: string,
type: string = "assistant_message",
seqEnd = seq,
) {
return {
seqStart: seq,
seqEnd,
provider: "claude",
item: { type, text },
timestamp: new Date(1000 + seq).toISOString(),
};
}
function makeTimelineEvent(
text: string,
type: string = "assistant_message",
): AgentStreamEventPayload {
return {
type: "timeline",
provider: "claude",
item: { type, text },
} as AgentStreamEventPayload;
}
function makeToolCallTimelineEvent(callId: string): AgentStreamEventPayload {
return {
type: "timeline",
provider: "claude",
item: {
type: "tool_call",
callId,
name: "Read",
status: "running",
detail: {
type: "read",
filePath: "/tmp/example.ts",
},
error: null,
},
} as AgentStreamEventPayload;
}
function makeStreamReducerEvent(
event: AgentStreamEventPayload,
seq: number,
): AgentStreamReducerEvent {
return {
event,
seq,
epoch: "epoch-1",
timestamp: new Date(1000 + seq),
};
}
function makeAssistantItem(text: string, id = `assistant-${text.length}`): StreamItem {
return {
kind: "assistant_message",
id,
text,
timestamp: new Date(1000),
};
}
function getAssistantTexts(items: StreamItem[]): string[] {
return items
.filter((item): item is Extract<StreamItem, { kind: "assistant_message" }> => {
return item.kind === "assistant_message";
})
.map((item) => item.text);
}
function getUserTexts(items: StreamItem[]): string[] {
return items
.filter((item): item is Extract<StreamItem, { kind: "user_message" }> => {
return item.kind === "user_message";
})
.map((item) => item.text);
}
const baseTimelineInput: ProcessTimelineResponseInput = {
payload: {
agentId: "agent-1",
direction: "after",
reset: false,
epoch: "epoch-1",
startCursor: null,
endCursor: null,
entries: [],
error: null,
hasNewer: false,
hasOlder: false,
},
currentTail: [],
currentHead: [],
currentCursor: undefined,
isInitializing: false,
hasActiveInitDeferred: false,
initRequestDirection: "tail",
};
const baseStreamInput: ProcessAgentStreamEventInput = {
event: makeTimelineEvent("hello"),
seq: undefined,
epoch: undefined,
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
timestamp: new Date(2000),
};
// ---------------------------------------------------------------------------
// processTimelineResponse
// ---------------------------------------------------------------------------
describe("processTimelineResponse", () => {
it("returns error path when payload.error is set", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: true,
payload: {
...baseTimelineInput.payload,
error: "something broke",
},
});
expect(result.error).toBe("something broke");
expect(result.initResolution).toBe("reject");
expect(result.clearInitializing).toBe(true);
expect(result.tail).toBe(baseTimelineInput.currentTail);
expect(result.head).toBe(baseTimelineInput.currentHead);
expect(result.cursorChanged).toBe(false);
expect(result.sideEffects).toEqual([]);
});
it("returns error with no init resolution when no deferred exists", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: false,
payload: {
...baseTimelineInput.payload,
error: "timeout",
},
});
expect(result.error).toBe("timeout");
expect(result.initResolution).toBe(null);
expect(result.clearInitializing).toBe(true);
});
it("replaces tail and clears head when reset=true", () => {
const existingTail: StreamItem[] = [
{
kind: "user_message",
id: "old",
text: "old message",
timestamp: new Date(500),
},
];
const existingHead: StreamItem[] = [
{
kind: "assistant_message",
id: "head-1",
text: "streaming",
timestamp: new Date(600),
},
];
const result = processTimelineResponse({
...baseTimelineInput,
currentTail: existingTail,
currentHead: existingHead,
payload: {
...baseTimelineInput.payload,
reset: true,
startCursor: { seq: 1 },
endCursor: { seq: 3 },
entries: [
makeTimelineEntry(1, "first"),
makeTimelineEntry(2, "second"),
makeTimelineEntry(3, "third"),
],
},
});
expect(result.tail).not.toBe(existingTail);
expect(result.tail.length).toBeGreaterThan(0);
expect(result.head).toEqual([]);
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 3,
});
expect(result.error).toBe(null);
expect(result.sideEffects.some((e) => e.type === "flush_pending_updates")).toBe(true);
});
it("sets cursor to null when reset=true but no cursors in payload", () => {
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: { epoch: "epoch-1", startSeq: 1, endSeq: 5 },
payload: {
...baseTimelineInput.payload,
reset: true,
entries: [],
},
});
expect(result.cursor).toBe(null);
expect(result.cursorChanged).toBe(true);
});
it("performs bootstrap tail init with catch-up side effect", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: true,
initRequestDirection: "tail",
payload: {
...baseTimelineInput.payload,
direction: "tail",
epoch: "epoch-1",
startCursor: { seq: 1 },
endCursor: { seq: 5 },
entries: [makeTimelineEntry(1, "first"), makeTimelineEntry(5, "last")],
},
});
// Bootstrap tail replaces
expect(result.tail.length).toBeGreaterThan(0);
expect(result.head).toEqual([]);
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
});
// Should have catch-up side effect
const catchUp = result.sideEffects.find((e) => e.type === "catch_up");
expect(catchUp).toBeDefined();
expect(catchUp!.type === "catch_up" && catchUp!.cursor).toEqual({
epoch: "epoch-1",
endSeq: 5,
});
});
it("appends incrementally for contiguous seqs", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 3,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(4, "next-1"), makeTimelineEntry(5, "next-2")],
},
});
expect(result.tail.length).toBeGreaterThan(0);
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
});
expect(result.error).toBe(null);
});
it("keeps an active assistant head live when an incremental fetch accepts same-turn assistant text", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 2,
};
const currentHead = [makeAssistantItem("This is a par")];
const result = processTimelineResponse({
...baseTimelineInput,
currentHead,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(3, "agraph")],
},
});
expect(getAssistantTexts(result.tail)).toEqual([]);
expect(getAssistantTexts(result.head)).toEqual(["This is a paragraph"]);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 3,
});
});
it("detects gap and emits catch-up side effect", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 3,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(10, "far ahead")],
},
});
// Gap should trigger catch-up
const catchUp = result.sideEffects.find((e) => e.type === "catch_up");
expect(catchUp).toBeDefined();
expect(catchUp!.type === "catch_up" && catchUp!.cursor).toEqual({
epoch: "epoch-1",
endSeq: 3,
});
});
it("drops stale entries silently", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 8,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(5, "old"), makeTimelineEntry(7, "also old")],
},
});
// No new items appended (all dropped as stale)
expect(result.tail).toBe(baseTimelineInput.currentTail);
expect(result.cursorChanged).toBe(false);
});
it("prepends older before-cursor entries and only expands the start cursor", () => {
const currentTail: StreamItem[] = [
{
kind: "user_message",
id: "current-3",
text: "current-3",
timestamp: new Date(3000),
},
];
const currentHead = [makeAssistantItem("live head")];
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 3,
endSeq: 5,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentTail,
currentHead,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
direction: "before",
epoch: "epoch-1",
startCursor: { seq: 1 },
endCursor: { seq: 2 },
entries: [
makeTimelineEntry(1, "older-1", "user_message"),
makeTimelineEntry(2, "older-2", "user_message"),
],
},
});
expect(getUserTexts(result.tail)).toEqual(["older-1", "older-2", "current-3"]);
expect(result.head).toBe(currentHead);
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
});
});
it("leaves the cursor alone when a before page makes no progress", () => {
const currentTail: StreamItem[] = [
{
kind: "user_message",
id: "current-3",
text: "current-3",
timestamp: new Date(3000),
},
];
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 3,
endSeq: 5,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentTail,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
direction: "before",
epoch: "epoch-1",
startCursor: { seq: 3 },
endCursor: { seq: 4 },
entries: [
makeTimelineEntry(3, "overlap-3", "user_message"),
makeTimelineEntry(4, "overlap-4", "user_message"),
],
},
});
expect(result.tail).toBe(currentTail);
expect(result.cursorChanged).toBe(false);
expect(result.cursor).toBe(existingCursor);
});
it("merges assistant chunks across the older-page prepend boundary", () => {
const currentTail = [makeAssistantItem("newer chunk", "assistant-newer")];
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 3,
endSeq: 5,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentTail,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
direction: "before",
epoch: "epoch-1",
startCursor: { seq: 1 },
endCursor: { seq: 2 },
entries: [makeTimelineEntry(1, "older chunk ")],
},
});
expect(getAssistantTexts(result.tail)).toEqual(["older chunk newer chunk"]);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
});
});
it("requests canonical catch-up when a projected entry overlaps unseen seqs", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [
{
...makeTimelineEntry(4, "merged assistant message"),
seqEnd: 8,
},
],
},
});
expect(result.tail).toBe(baseTimelineInput.currentTail);
expect(result.cursorChanged).toBe(false);
expect(result.sideEffects).toContainEqual({
type: "catch_up",
cursor: {
epoch: "epoch-1",
endSeq: 5,
},
});
});
it("drops entries with epoch mismatch", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
};
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: existingCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-2",
entries: [makeTimelineEntry(6, "different epoch")],
},
});
expect(result.tail).toBe(baseTimelineInput.currentTail);
expect(result.cursorChanged).toBe(false);
});
it("resolves init when deferred matches direction", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: true,
initRequestDirection: "after",
payload: {
...baseTimelineInput.payload,
direction: "after",
entries: [],
},
});
expect(result.initResolution).toBe("resolve");
expect(result.clearInitializing).toBe(true);
});
it("does not resolve init when directions differ (before vs after)", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: true,
initRequestDirection: "after",
payload: {
...baseTimelineInput.payload,
direction: "before",
entries: [],
},
});
// "before" direction doesn't match "after" initRequestDirection,
// and "before" is not a bootstrap tail path, so init should NOT resolve
expect(result.initResolution).toBe(null);
expect(result.clearInitializing).toBe(false);
});
it("clears initializing even without deferred", () => {
const result = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: false,
payload: {
...baseTimelineInput.payload,
direction: "after",
entries: [],
},
});
expect(result.clearInitializing).toBe(true);
expect(result.initResolution).toBe(null);
});
it("always includes flush_pending_updates side effect on success", () => {
const result = processTimelineResponse({
...baseTimelineInput,
payload: {
...baseTimelineInput.payload,
entries: [],
},
});
expect(result.sideEffects.some((e) => e.type === "flush_pending_updates")).toBe(true);
});
it("initializes cursor when no existing cursor on first entries", () => {
const result = processTimelineResponse({
...baseTimelineInput,
currentCursor: undefined,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(1, "first"), makeTimelineEntry(2, "second")],
},
});
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 2,
});
});
});
// ---------------------------------------------------------------------------
// processAgentStreamEvent
// ---------------------------------------------------------------------------
describe("processAgentStreamEvent", () => {
it("passes through non-timeline events without cursor changes", () => {
const turnEvent: AgentStreamEventPayload = {
type: "turn_completed",
provider: "claude",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnEvent,
seq: undefined,
epoch: undefined,
});
expect(result.cursorChanged).toBe(false);
expect(result.cursor).toBe(null);
expect(result.sideEffects).toEqual([]);
});
it("accepts timeline event with cursor advance", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 4,
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("new chunk"),
seq: 5,
epoch: "epoch-1",
currentCursor: existingCursor,
});
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
});
expect(result.sideEffects).toEqual([]);
});
it("detects gap and emits catch-up side effect", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 4,
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("far ahead"),
seq: 10,
epoch: "epoch-1",
currentCursor: existingCursor,
});
expect(result.cursorChanged).toBe(false);
expect(result.changedTail).toBe(false);
expect(result.changedHead).toBe(false);
const catchUp = result.sideEffects.find((e) => e.type === "catch_up");
expect(catchUp).toBeDefined();
expect(catchUp!.cursor).toEqual({
epoch: "epoch-1",
endSeq: 4,
});
});
it("drops stale timeline event", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 8,
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("old"),
seq: 5,
epoch: "epoch-1",
currentCursor: existingCursor,
});
expect(result.cursorChanged).toBe(false);
expect(result.changedTail).toBe(false);
expect(result.changedHead).toBe(false);
expect(result.sideEffects).toEqual([]);
});
it("drops timeline event with epoch mismatch", () => {
const existingCursor: TimelineCursor = {
epoch: "epoch-1",
startSeq: 1,
endSeq: 5,
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("wrong epoch"),
seq: 6,
epoch: "epoch-2",
currentCursor: existingCursor,
});
expect(result.cursorChanged).toBe(false);
expect(result.changedTail).toBe(false);
expect(result.changedHead).toBe(false);
expect(result.sideEffects).toEqual([]);
});
it("initializes cursor when none exists", () => {
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("first"),
seq: 1,
epoch: "epoch-1",
currentCursor: undefined,
});
expect(result.cursorChanged).toBe(true);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 1,
});
});
it("derives optimistic idle status on turn_completed for running agent", () => {
const turnCompletedEvent: AgentStreamEventPayload = {
type: "turn_completed",
provider: "claude",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnCompletedEvent,
currentAgent: {
status: "running",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(true);
expect(result.agent).not.toBe(null);
expect(result.agent!.status).toBe("idle");
expect(result.agent!.updatedAt.getTime()).toBe(2000);
expect(result.agent!.lastActivityAt.getTime()).toBe(2000);
});
it("derives optimistic error status on turn_failed for running agent", () => {
const turnFailedEvent: AgentStreamEventPayload = {
type: "turn_failed",
provider: "claude",
error: "something broke",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnFailedEvent,
currentAgent: {
status: "running",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(true);
expect(result.agent!.status).toBe("error");
});
it("does not derive optimistic idle status on turn_canceled for running agent", () => {
const turnCanceledEvent: AgentStreamEventPayload = {
type: "turn_canceled",
provider: "codex",
reason: "interrupted",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnCanceledEvent,
currentAgent: {
status: "running",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(false);
expect(result.agent).toBe(null);
});
it("does not change agent when status is not running", () => {
const turnCompletedEvent: AgentStreamEventPayload = {
type: "turn_completed",
provider: "claude",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnCompletedEvent,
currentAgent: {
status: "idle",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(false);
expect(result.agent).toBe(null);
});
it("does not change agent when no agent is provided", () => {
const turnCompletedEvent: AgentStreamEventPayload = {
type: "turn_completed",
provider: "claude",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnCompletedEvent,
currentAgent: null,
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(false);
expect(result.agent).toBe(null);
});
it("preserves updatedAt when agent timestamp is newer than event", () => {
const turnCompletedEvent: AgentStreamEventPayload = {
type: "turn_completed",
provider: "claude",
};
const result = processAgentStreamEvent({
...baseStreamInput,
event: turnCompletedEvent,
currentAgent: {
status: "running",
updatedAt: new Date(5000),
lastActivityAt: new Date(5000),
},
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(true);
expect(result.agent!.updatedAt.getTime()).toBe(5000);
expect(result.agent!.lastActivityAt.getTime()).toBe(5000);
});
it("does not produce agent patch for non-terminal events", () => {
const result = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent("just text"),
currentAgent: {
status: "running",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
seq: 1,
epoch: "epoch-1",
timestamp: new Date(2000),
});
expect(result.agentChanged).toBe(false);
expect(result.agent).toBe(null);
});
});
describe("processAgentStreamEvents", () => {
it("coalesces contiguous assistant stream events into one head update and final cursor", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(makeTimelineEvent("Hello"), 1),
makeStreamReducerEvent(makeTimelineEvent(" world"), 2),
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
});
expect(result.changedTail).toBe(false);
expect(result.changedHead).toBe(true);
expect(result.tail).toEqual([]);
expect(result.head).toHaveLength(1);
expect(result.head[0]).toMatchObject({
kind: "assistant_message",
text: "Hello world",
});
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 2,
} satisfies TimelineCursor);
expect(result.sideEffects).toEqual([]);
});
it("promotes completed assistant markdown blocks to tail while keeping the live block in head", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(makeTimelineEvent("First paragraph"), 1),
makeStreamReducerEvent(makeTimelineEvent("\n\nSecond paragraph"), 2),
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
});
expect(result.changedTail).toBe(true);
expect(result.changedHead).toBe(true);
expect(result.tail).toHaveLength(1);
expect(result.tail[0]).toMatchObject({
kind: "assistant_message",
text: "First paragraph",
});
expect(result.head).toHaveLength(1);
expect(result.head[0]).toMatchObject({
kind: "assistant_message",
text: "Second paragraph",
});
});
it("preserves a live block trailing newline after promoting completed markdown blocks", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(
makeTimelineEvent(
"Done. I added `[TimelineMerge] ...` logging around the suspicious merge",
),
238,
),
makeStreamReducerEvent(makeTimelineEvent("/reconcile paths.\n\nChanged:\n"), 239),
makeStreamReducerEvent(makeTimelineEvent("- [timeline-debug.ts]"), 240),
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
});
expect(result.changedTail).toBe(true);
expect(result.changedHead).toBe(true);
expect(result.tail).toHaveLength(1);
expect(result.tail[0]).toMatchObject({
kind: "assistant_message",
text: "Done. I added `[TimelineMerge] ...` logging around the suspicious merge/reconcile paths.",
});
expect(result.head).toHaveLength(1);
expect(result.head[0]).toMatchObject({
kind: "assistant_message",
text: "Changed:\n- [timeline-debug.ts]",
});
});
it("does not promote a markdown block that is still inside an open code fence", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(makeTimelineEvent("Before fence\n\n```ts\nconst a = 1;"), 1),
makeStreamReducerEvent(makeTimelineEvent("\n\nconst b = 2;"), 2),
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
});
expect(result.changedTail).toBe(true);
expect(result.tail).toHaveLength(1);
expect(result.tail[0]).toMatchObject({
kind: "assistant_message",
text: "Before fence",
});
expect(result.head).toHaveLength(1);
expect(result.head[0]).toMatchObject({
kind: "assistant_message",
text: "```ts\nconst a = 1;\n\nconst b = 2;",
});
});
it("flushes the live assistant block before applying a tool call in the same reducer pass", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(makeTimelineEvent("Before tool"), 1),
makeStreamReducerEvent(makeToolCallTimelineEvent("call-1"), 2),
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
});
expect(result.changedTail).toBe(true);
expect(result.changedHead).toBe(true);
expect(result.head).toEqual([]);
expect(result.tail.map((item: StreamItem) => item.kind)).toEqual([
"assistant_message",
"tool_call",
]);
expect(result.cursor).toEqual({
epoch: "epoch-1",
startSeq: 1,
endSeq: 2,
} satisfies TimelineCursor);
});
it("returns the final optimistic lifecycle patch across a batch", () => {
const result = processAgentStreamEvents({
events: [
makeStreamReducerEvent(makeTimelineEvent("Done"), 1),
{
event: { type: "turn_completed", provider: "claude" } as AgentStreamEventPayload,
seq: undefined,
epoch: undefined,
timestamp: new Date(3000),
},
],
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: {
status: "running",
updatedAt: new Date(1000),
lastActivityAt: new Date(1000),
},
});
expect(result.head).toEqual([]);
expect(result.tail).toHaveLength(1);
expect(result.agentChanged).toBe(true);
expect(result.agent).toMatchObject({
status: "idle",
updatedAt: new Date(3000),
lastActivityAt: new Date(3000),
});
});
it("keeps a live Claude assistant paragraph contiguous when init tail hydration lands mid-stream", () => {
const seq186Text = "Now let me write the updated tool-call-detail-parser.ts with all the sub";
const seq187Text = "agent additions.";
const liveSeq186 = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent(seq186Text),
seq: 186,
epoch: "epoch-1",
currentTail: [],
currentHead: [],
currentCursor: undefined,
timestamp: new Date("2026-05-02T10:00:00.186Z"),
});
expect(getAssistantTexts(liveSeq186.head)).toEqual([seq186Text]);
expect(getAssistantTexts(liveSeq186.tail)).toEqual([]);
const initTailHydration = processTimelineResponse({
...baseTimelineInput,
currentTail: liveSeq186.tail,
currentHead: liveSeq186.head,
currentCursor: liveSeq186.cursor ?? undefined,
isInitializing: true,
hasActiveInitDeferred: true,
initRequestDirection: "tail",
payload: {
agentId: "agent-1",
direction: "tail",
reset: false,
epoch: "epoch-1",
startCursor: { seq: 186 },
endCursor: { seq: 186 },
entries: [makeTimelineEntry(186, seq186Text)],
error: null,
hasNewer: false,
hasOlder: false,
},
});
expect(getAssistantTexts(initTailHydration.tail)).toEqual([]);
expect(getAssistantTexts(initTailHydration.head)).toEqual([seq186Text]);
const liveSeq187 = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent(seq187Text),
seq: 187,
epoch: "epoch-1",
currentTail: initTailHydration.tail,
currentHead: initTailHydration.head,
currentCursor: initTailHydration.cursor ?? undefined,
timestamp: new Date("2026-05-02T10:00:00.187Z"),
});
const finalAssistantItems = [...liveSeq187.tail, ...liveSeq187.head].filter(
(item): item is Extract<StreamItem, { kind: "assistant_message" }> =>
item.kind === "assistant_message",
);
expect(finalAssistantItems).toHaveLength(1);
expect(finalAssistantItems[0]?.text).toBe(`${seq186Text}${seq187Text}`);
});
it("does not split an assistant sentence between hydrated tail and live head", () => {
const hydrated = processTimelineResponse({
...baseTimelineInput,
isInitializing: true,
hasActiveInitDeferred: true,
initRequestDirection: "tail",
payload: {
agentId: "agent-1",
direction: "tail",
reset: false,
epoch: "epoch-1",
startCursor: { seq: 10 },
endCursor: { seq: 10 },
entries: [makeTimelineEntry(10, "Call-site API — exactly one primitive. Not")],
error: null,
hasNewer: false,
hasOlder: false,
},
});
const liveContinuation = processAgentStreamEvent({
...baseStreamInput,
event: makeTimelineEvent(" gateValue, not filterEnum."),
seq: 11,
epoch: "epoch-1",
currentTail: hydrated.tail,
currentHead: hydrated.head,
currentCursor: hydrated.cursor ?? undefined,
timestamp: new Date("2026-05-02T10:00:00.011Z"),
});
const finalAssistantItems = [...liveContinuation.tail, ...liveContinuation.head].filter(
(item): item is Extract<StreamItem, { kind: "assistant_message" }> =>
item.kind === "assistant_message",
);
expect(finalAssistantItems).toHaveLength(1);
expect(finalAssistantItems[0]?.text).toBe(
"Call-site API — exactly one primitive. Not gateValue, not filterEnum.",
);
});
});
describe("createAgentStreamReducerQueue", () => {
function createManualScheduler() {
let nextId = 1;
const callbacks = new Map<number, () => void>();
return {
schedule(callback: () => void) {
const id = nextId;
nextId += 1;
callbacks.set(id, callback);
return id;
},
cancel(id: number) {
callbacks.delete(id);
},
flushOne() {
const entry = callbacks.entries().next().value;
if (!entry) {
throw new Error("Expected a scheduled callback");
}
const [id, callback] = entry;
callbacks.delete(id);
callback();
},
get size() {
return callbacks.size;
},
};
}
it("coalesces multiple events for one agent into one scheduled commit", () => {
const scheduler = createManualScheduler();
const commits: Array<{ agentId: string; headText: string; cursorEndSeq: number | null }> = [];
let currentTail: StreamItem[] = [];
let currentHead: StreamItem[] = [];
const queue = createAgentStreamReducerQueue({
getSnapshot: () => ({
currentTail,
currentHead,
currentCursor: undefined,
currentAgent: null,
}),
commit: (agentId, result) => {
currentTail = result.tail;
currentHead = result.head;
commits.push({
agentId,
headText: result.head[0]?.kind === "assistant_message" ? result.head[0].text : "",
cursorEndSeq: result.cursor?.endSeq ?? null,
});
},
handleSideEffects: () => {},
scheduleFlush: scheduler.schedule,
cancelFlush: scheduler.cancel,
});
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent("Hello"), 1));
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent(" world"), 2));
expect(scheduler.size).toBe(1);
expect(commits).toEqual([]);
scheduler.flushOne();
expect(commits).toEqual([
{
agentId: "agent-1",
headText: "Hello world",
cursorEndSeq: 2,
},
]);
expect(scheduler.size).toBe(0);
});
it("flushes queued events synchronously for one agent before canonical history is applied", () => {
const scheduler = createManualScheduler();
const commits: string[] = [];
const queue = createAgentStreamReducerQueue({
getSnapshot: () => ({
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
}),
commit: (agentId, result) => {
commits.push(
`${agentId}:${result.head[0]?.kind === "assistant_message" ? result.head[0].text : ""}`,
);
},
handleSideEffects: () => {},
scheduleFlush: scheduler.schedule,
cancelFlush: scheduler.cancel,
});
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent("queued"), 1));
queue.flushAgent("agent-1");
expect(commits).toEqual(["agent-1:queued"]);
expect(scheduler.size).toBe(0);
});
it("keeps a live paragraph in one assistant item when canonical fetch interleaves with queued stream chunks", () => {
const scheduler = createManualScheduler();
let currentTail: StreamItem[] = [];
let currentHead: StreamItem[] = [];
let currentCursor: TimelineCursor | undefined;
const queue = createAgentStreamReducerQueue({
getSnapshot: () => ({
currentTail,
currentHead,
currentCursor,
currentAgent: null,
}),
commit: (_agentId, result) => {
currentTail = result.tail;
currentHead = result.head;
currentCursor = result.cursor ?? undefined;
},
handleSideEffects: () => {},
scheduleFlush: scheduler.schedule,
cancelFlush: scheduler.cancel,
});
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent("This is a par"), 2));
queue.flushAgent("agent-1");
const timelineResult = processTimelineResponse({
...baseTimelineInput,
currentTail,
currentHead,
currentCursor,
payload: {
...baseTimelineInput.payload,
epoch: "epoch-1",
entries: [makeTimelineEntry(3, "agraph")],
},
});
currentTail = timelineResult.tail;
currentHead = timelineResult.head;
currentCursor = timelineResult.cursor ?? undefined;
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent(" continues."), 4));
queue.flushAgent("agent-1");
expect(getAssistantTexts(currentTail)).toEqual([]);
expect(getAssistantTexts(currentHead)).toEqual(["This is a paragraph continues."]);
expect(currentCursor).toEqual({
epoch: "epoch-1",
startSeq: 2,
endSeq: 4,
});
});
it("flushes queued events synchronously before disposal", () => {
const scheduler = createManualScheduler();
const commits: string[] = [];
const queue = createAgentStreamReducerQueue({
getSnapshot: () => ({
currentTail: [],
currentHead: [],
currentCursor: undefined,
currentAgent: null,
}),
commit: (agentId, result) => {
commits.push(
`${agentId}:${result.head[0]?.kind === "assistant_message" ? result.head[0].text : ""}`,
);
},
handleSideEffects: () => {},
scheduleFlush: scheduler.schedule,
cancelFlush: scheduler.cancel,
});
queue.enqueue("agent-1", makeStreamReducerEvent(makeTimelineEvent("queued"), 1));
queue.dispose({ flush: true });
expect(commits).toEqual(["agent-1:queued"]);
expect(scheduler.size).toBe(0);
});
});