fix(app): stabilize session timeline layout continuity (#34533)

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# Timeline Layout Continuity
Run from `packages/app`:
```sh
bun run test:stability
```
The suite runs a production build in one Chromium worker. Selected scenarios use deterministic 4x CPU stress after application readiness. This is a stress profile, not emulation of a specific device.
## What It Proves
The continuity probe samples DOM-derived layout and visibility state across browser render opportunities. Tests declare explicit contracts such as:
- Preserve a visible semantic anchor while the user is away from the bottom.
- Preserve end anchoring while active content grows or new content appears.
- Keep adjacent visible rows ordered without material overlap.
- Keep user-selected disclosure state through updates and virtualization.
- Avoid a sampled blank interval while one visible surface replaces another.
- Preserve logical row and control identity where local state or focus depends on it.
- Keep keyboard, wheel, and nested-scroll ownership consistent during remeasurement.
The suite exercises real browser reducer, projection, component, virtualizer, layout, focus, and interaction code. The backend and event producer are controlled fixtures.
## What It Does Not Prove
The pass/fail oracle does not inspect every compositor-presented pixel. A sample taken after `requestAnimationFrame` is a DOM/layout observation, not proof that every sampled state was displayed or that every displayed frame was sampled.
The suite does not provide complete coverage for:
- Compositor-only or raster-only glitches.
- Color, contrast, canvas, WebGL, masks, irregular clips, or arbitrary occlusion.
- Physical display refresh rates, native OS scaling, or a named low-end device.
- TCP packetization, proxy buffering, or the complete real server/provider pipeline.
Playwright video, trace, screenshots, and observation JSON are diagnostic evidence. They are not pixel baselines and do not participate in normal pass/fail decisions.
For optional before/violation/after screenshots, set `OPENCODE_STABILITY_CAPTURE=1`. Capture is opt-in because compositor readback can perturb timing.
## Test Layers
- **Projection:** admitted rows, grouping, labels, and final visible states.
- **Local state:** disclosure state, identity, duplicate delivery, and virtualization restoration.
- **Interaction:** wheel, keyboard, nested scrolling, actionability, and focus behavior.
- **Layout continuity:** anchoring, adjacency, responsive reflow, and visible surface handoffs.
- **Reducer hardening:** validly shaped but intentionally reordered, duplicated, removed, or replaced events.
- **Oracle contract:** pure analyzer and browser sampler calibration tests.
Production-lifecycle fixtures should model states emitted by the current producer. Impossible or reordered sequences belong in reducer-hardening tests and must not be described as normal provider behavior.
## Diagnostics
Failures retain:
- `video.webm`
- `trace.zip`
- failure screenshot
- sampled DOM/layout trace JSON
- event markers and summarized violations
The analyzer records both unclipped layout bounds and ancestor-clipped visible intersections. Scrollbar and raw `scrollTop` changes alone do not fail continuity checks; user-visible semantic anchor movement does.

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
shell,
textPart,
toolPart,
userMessage,
waitForVisualSettle,
type TimelineMessage,
} from "./fixture"
test.describe("timeline adverse visual stability", () => {
test("does not pull a scrolled-away user while an active shell grows", async ({ page }, testInfo) => {
const activeShellID = "prt_adverse_01_shell"
const messages = [
...history(24),
userMessage(),
assistantMessage([shell(activeShellID, "running")], { completed: false }),
]
const timeline = await setupTimeline(page, {
messages,
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
eventRetry: 30,
})
const scroller = page.locator(".scroll-view__viewport", {
has: page.locator('[data-timeline-row="AssistantPart"]'),
})
await scroller.evaluate((element) => {
element.dispatchEvent(new WheelEvent("wheel", { bubbles: true, cancelable: true, deltaY: -450 }))
element.scrollTop = Math.max(0, element.scrollHeight - element.clientHeight - 450)
})
await page.waitForTimeout(150)
await expect
.poll(() => scroller.evaluate((element) => element.scrollHeight - element.clientHeight - element.scrollTop))
.toBeGreaterThan(100)
const anchor = await scroller.evaluate((element) => {
const view = element.getBoundingClientRect()
return [...element.querySelectorAll<HTMLElement>("[data-timeline-key]")].find((row) => {
const rect = row.getBoundingClientRect()
return rect.top >= view.top + 40 && rect.bottom <= view.bottom - 40
})?.dataset.timelineKey
})
expect(anchor).toBeTruthy()
await waitForVisualSettle(page, [`[data-timeline-key="${anchor}"]`])
const regions = defineVisualRegions({
anchor: { selector: `[data-timeline-key="${anchor}"]` },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(activeShellID, "running", lines(1))), 180)
await timeline.send(partUpdated(shell(activeShellID, "running", lines(10))), 90)
await timeline.send(partUpdated(shell(activeShellID, "running", lines(50))), 350)
await timeline.send(partUpdated(shell(activeShellID, "completed", lines(50))), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"scrolled-away-shell",
trace,
visualPlan(regions, [
{ type: "required", regions: ["anchor"] },
{ type: "unique", regions: ["anchor"] },
{ type: "stable", regions: ["anchor"] },
{ type: "fixed", regions: ["anchor"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
]),
)
})
test("preserves an explicit shell state across virtualization", async ({ page }) => {
const targetID = "prt_virtual_shell"
const messages = [
userMessage(undefined, { id: "msg_0000_virtual_user", created: 1700000000000 }),
assistantMessage([shell(targetID, "completed", lines(20))], {
id: "msg_0001_virtual_assistant",
parentID: "msg_0000_virtual_user",
created: 1700000001000,
}),
...history(35, 10),
]
await setupTimeline(page, { messages, settings: { shellToolPartsExpanded: false } })
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
await scroller.evaluate((element) => {
element.dispatchEvent(new WheelEvent("wheel", { bubbles: true, cancelable: true, deltaY: -1_000 }))
element.scrollTop = 0
})
await page.waitForTimeout(300)
const trigger = page.locator(`[data-timeline-part-id="${targetID}"] [data-slot="collapsible-trigger"]`)
await expect(trigger).toBeVisible()
await trigger.click()
await expect(trigger).toHaveAttribute("aria-expanded", "true")
await scroller.evaluate((element) => (element.scrollTop = element.scrollHeight))
await expect(page.locator(`[data-timeline-part-id="${targetID}"]`)).toHaveCount(0)
await scroller.evaluate((element) => (element.scrollTop = 0))
await expect(trigger).toBeVisible()
await expect(trigger).toHaveAttribute("aria-expanded", "true")
})
test("keeps narrow viewport rows ordered during long shell growth", async ({ page }, testInfo) => {
const shellID = "prt_narrow_01_shell"
const followingID = "prt_narrow_02_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage(
[shell(shellID, "running"), textPart(followingID, "A narrow following row that wraps across lines.")],
{
completed: false,
},
),
],
settings: { shellToolPartsExpanded: true },
viewport: { width: 430, height: 800 },
cpuRate: 4,
})
await waitForVisualSettle(page, [
`[data-timeline-part-id="${shellID}"]`,
`[data-timeline-part-id="${followingID}"]`,
])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "running", wideLines(10))), 100)
await timeline.send(partUpdated(shell(shellID, "running", wideLines(50))), 300)
await timeline.send(partUpdated(shell(shellID, "completed", wideLines(50))), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"narrow-shell",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
),
)
})
test("keeps visible rows ordered while resizing desktop to narrow and back", async ({ page }, testInfo) => {
const shellID = "prt_resize_01_shell"
const contextIDs = ["prt_resize_02_read", "prt_resize_03_glob"]
const followingID = "prt_resize_04_following"
await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([
shell(shellID, "completed", wideLines(15)),
toolPart(contextIDs[0]!, "read", "completed", { filePath: "src/a.ts" }),
toolPart(contextIDs[1]!, "glob", "completed", { path: ".", pattern: "**/*.ts" }),
textPart(followingID, "Following responsive timeline content that wraps on narrow screens."),
]),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
seedHistory: true,
})
const group = `[data-timeline-part-ids="${contextIDs.join(",")}"]`
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
context: { selector: group, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await page.setViewportSize({ width: 430, height: 800 })
await page.waitForTimeout(500)
await page.setViewportSize({ width: 900, height: 800 })
await page.waitForTimeout(500)
await page.setViewportSize({ width: 1400, height: 900 })
await page.waitForTimeout(500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"responsive-resize",
trace,
visualPlan(regions, [
{ type: "required", regions: ["shell", "context", "following"] },
{ type: "unique", regions: ["shell", "context", "following"] },
{ type: "stable", regions: ["shell", "context", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 4, maxReversals: 4 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["shell", "context", "following"] },
]),
)
})
})
function history(count: number, offset = 0): TimelineMessage[] {
return Array.from({ length: count }, (_, index) => {
const value = index + offset
const prefix = `msg_0${String(value).padStart(3, "0")}_history`
const userID = `${prefix}_a_user`
return [
userMessage(undefined, { id: userID, created: 1699990000000 + value * 10_000 }),
assistantMessage(
[
textPart(
`prt_history_${String(value).padStart(3, "0")}`,
`Historical response ${value}. ${"Stable history content. ".repeat(8)}`,
),
],
{
id: `${prefix}_b_assistant`,
parentID: userID,
created: 1699990001000 + value * 10_000,
},
),
]
}).flat()
}
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}
function wideLines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1} ${"wide-output-".repeat(20)}`).join("\n")
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantID,
assistantMessage,
event,
partUpdated,
setupTimeline,
textPart,
toolPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
const inputs = {
read: { filePath: "src/a.ts", offset: 0, limit: 120 },
glob: { path: ".", pattern: "**/*.ts" },
grep: { path: ".", pattern: "stable", include: "*.ts" },
list: { path: "src" },
}
test("appends context operations while the group is expanded", async ({ page }, testInfo) => {
const firstID = "prt_append_01_read"
const followingID = "prt_append_99_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([toolPart(firstID, "read", "running", inputs.read), textPart(followingID, "Following append")], {
completed: false,
}),
],
cpuRate: 4,
})
const initialGroup = `[data-timeline-part-ids="${firstID}"]`
await page.locator(`${initialGroup} [data-slot="collapsible-trigger"]`).click()
await waitForVisualSettle(page, [initialGroup, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
context: {
selector: '[data-timeline-part-ids^="prt_append_01_read"]',
closest: '[data-timeline-row="AssistantPart"]',
},
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(toolPart("prt_append_02_glob", "glob", "running", inputs.glob)), 180)
await timeline.send(partUpdated(toolPart("prt_append_03_grep", "grep", "completed", inputs.grep)), 240)
await timeline.send(partUpdated(toolPart("prt_append_04_list", "list", "completed", inputs.list)), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"context-append",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["context", "following"] },
{ type: "unique", regions: ["context", "following"] },
{ type: "stable", regions: ["context", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: ["following"], maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["context", "following"] },
],
{ perMarker: true },
),
)
await expect(
page.locator(
'[data-timeline-part-ids="prt_append_01_read,prt_append_02_glob,prt_append_03_grep,prt_append_04_list"]',
),
).toBeVisible()
await expect(
page.locator('[data-timeline-part-ids^="prt_append_01_read"] [data-slot="collapsible-trigger"]'),
).toHaveAttribute("aria-expanded", "true")
})
test("splits and merges context groups when a middle text part changes", async ({ page }, testInfo) => {
const textID = "prt_split_02_text"
const followingID = "prt_split_99_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([
toolPart("prt_split_01_read", "read", "completed", inputs.read),
textPart(textID, "Boundary"),
toolPart("prt_split_03_glob", "glob", "completed", inputs.glob),
textPart(followingID, "Following split groups"),
]),
],
cpuRate: 4,
})
const regions = defineVisualRegions({
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
event("message.part.removed", { sessionID: "ses_timeline_stability", messageID: assistantID, partID: textID }),
500,
)
await expect(page.locator('[data-timeline-part-ids="prt_split_01_read,prt_split_03_glob"]')).toBeVisible()
await timeline.send(partUpdated(textPart(textID, "Boundary restored")), 500)
await expect(page.locator('[data-timeline-part-ids="prt_split_01_read"]')).toBeVisible()
await expect(page.locator('[data-timeline-part-ids="prt_split_03_glob"]')).toBeVisible()
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"context-split-merge",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["following"] },
{ type: "unique", regions: ["following"] },
{ type: "stable", regions: ["following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 1 },
{ type: "label-stability", regions: "all" },
],
{ perMarker: true },
),
)
})
test("removing the first context member replaces the group once without overlapping following content", async ({
page,
}, testInfo) => {
const ids = ["prt_key_01_read", "prt_key_02_glob", "prt_key_03_grep"]
const followingID = "prt_key_99_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([
toolPart(ids[0]!, "read", "completed", inputs.read),
toolPart(ids[1]!, "glob", "completed", inputs.glob),
toolPart(ids[2]!, "grep", "completed", inputs.grep),
textPart(followingID, "Following replaced group"),
]),
],
cpuRate: 4,
})
const original = page.locator(`[data-timeline-part-ids="${ids.join(",")}"]`)
const originalRowKey = await original.evaluate((element) =>
element.closest("[data-timeline-key]")?.getAttribute("data-timeline-key"),
)
await original.locator('[data-slot="collapsible-trigger"]').click()
await expect(original.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "true")
const regions = defineVisualRegions({
context: {
selector: '[data-timeline-part-ids*="prt_key_02_glob"]',
closest: '[data-timeline-row="AssistantPart"]',
},
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
event("message.part.removed", { sessionID: "ses_timeline_stability", messageID: assistantID, partID: ids[0] }),
500,
)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"context-first-remove",
trace,
visualPlan(regions, [
{ type: "required", regions: ["context", "following"] },
{ type: "unique", regions: ["context", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["context", "following"] },
]),
)
await expect(page.locator(`[data-timeline-part-ids="${ids.slice(1).join(",")}"]`)).toBeVisible()
expect(
await page
.locator(`[data-timeline-part-ids="${ids.slice(1).join(",")}"]`)
.evaluate((element) => element.closest("[data-timeline-key]")?.getAttribute("data-timeline-key")),
).toBe(originalRowKey)
await expect(
page.locator(`[data-timeline-part-ids="${ids.slice(1).join(",")}"] [data-slot="collapsible-trigger"]`),
).toHaveAttribute("aria-expanded", "true")
})

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import { test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
shell,
textPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
// Fractional scaling exercises different browser rounding than the baseline.
for (const deviceScaleFactor of [1, 1.25]) {
test(`keeps shell growth ordered at device scale ${deviceScaleFactor}`, async ({ page }, testInfo) => {
const shellID = `prt_dpr_${String(deviceScaleFactor).replace(".", "_")}_01_shell`
const followingID = `prt_dpr_${String(deviceScaleFactor).replace(".", "_")}_02_following`
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following scaled shell")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
deviceScaleFactor,
seedHistory: true,
})
await waitForVisualSettle(page, [
`[data-timeline-part-id="${shellID}"]`,
`[data-timeline-part-id="${followingID}"]`,
])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "running", lines(20))), 180)
await timeline.send(partUpdated(shell(shellID, "completed", lines(20))), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, `dpr-${deviceScaleFactor}`, trace, shellPlan(regions))
})
}
for (const reducedMotion of [true]) {
test(`keeps shell and status transitions ordered with reduced motion ${reducedMotion}`, async ({
page,
}, testInfo) => {
const shellID = `prt_motion_${reducedMotion}_01_shell`
const followingID = `prt_motion_${reducedMotion}_02_following`
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following motion profile")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
reducedMotion,
cpuRate: 4,
seedHistory: true,
})
await waitForVisualSettle(page, [
`[data-timeline-part-id="${shellID}"]`,
`[data-timeline-part-id="${followingID}"]`,
])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "completed", lines(10))), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, `reduced-motion-${reducedMotion}`, trace, shellPlan(regions))
})
}
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}
function shellPlan<Regions extends ReturnType<typeof defineVisualRegions>>(
regions: Regions & Record<"shell" | "following", { selector: string }>,
) {
return visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
)
}

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import { test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
textPart,
toolPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
const profiles = [
{ name: "edit", tool: "edit", input: { filePath: "src/edit.ts" } },
{
name: "multi patch",
tool: "apply_patch",
input: { files: ["src/a.ts", "src/b.ts", "src/old.ts", "src/moved.ts"] },
},
] as const
for (const profile of profiles) {
test(`stabilizes ${profile.name} pending to completed`, async ({ page }, testInfo) => {
const partID = `prt_file_matrix_${profiles.indexOf(profile)}`
const followingID = `prt_file_matrix_following_${profiles.indexOf(profile)}`
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage(
[
toolPart(partID, profile.tool, "pending", profile.input),
textPart(followingID, `Following ${profile.name}`),
],
{ completed: false },
),
],
settings: { editToolPartsExpanded: true },
cpuRate: 4,
})
await waitForVisualSettle(page, [`[data-timeline-part-id="${partID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
tool: { selector: `[data-timeline-part-id="${partID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(toolPart(partID, profile.tool, "running", profile.input)), 180)
await timeline.send(partUpdated(completedPart(partID, profile)), 900)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
`file-${profile.name}`,
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["tool", "following"] },
{ type: "unique", regions: ["tool", "following"] },
{ type: "stable", regions: ["tool", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0, maxReversals: 1 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["tool", "following"] },
],
{ perMarker: true },
),
)
})
}
function completedPart(partID: string, profile: (typeof profiles)[number]) {
if (profile.tool === "edit") {
return toolPart(partID, profile.tool, "completed", profile.input, {
metadata: {
filediff: {
file: "src/edit.ts",
additions: 50,
deletions: 50,
before: source(50, false),
after: source(50, true),
},
},
})
}
const files = [
patchFile("src/a.ts", "update"),
patchFile("src/b.ts", "add"),
patchFile("src/old.ts", "delete"),
{ ...patchFile("src/moved.ts", "move"), move: "src/new-place.ts" },
]
return toolPart(partID, profile.tool, "completed", profile.input, { metadata: { files } })
}
function patchFile(filePath: string, type: "add" | "update" | "delete" | "move") {
return {
filePath,
relativePath: filePath,
type,
additions: type === "delete" ? 0 : 20,
deletions: type === "add" ? 0 : 20,
before: type === "add" ? undefined : source(20, false),
after: type === "delete" ? undefined : source(20, true),
}
}
function source(count: number, changed: boolean) {
return Array.from(
{ length: count },
(_, index) => `export const value${index} = ${changed ? index + 1 : index}\n`,
).join("")
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
textPart,
toolPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
test("adds patch files incrementally without resetting outer expansion", async ({ page }, testInfo) => {
const patchID = "prt_incremental_01_patch"
const followingID = "prt_incremental_02_following"
const first = patchFile("src/a.ts", "update")
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage(
[
toolPart(patchID, "apply_patch", "running", { files: [first.filePath] }, { metadata: { files: [first] } }),
textPart(followingID, "Following incremental patch"),
],
{ completed: false },
),
],
settings: { editToolPartsExpanded: true },
cpuRate: 4,
seedHistory: true,
})
const trigger = page.locator(`[data-timeline-part-id="${patchID}"] [data-slot="collapsible-trigger"]`).first()
await expect(trigger).toHaveAttribute("aria-expanded", "true")
await waitForVisualSettle(page, [`[data-timeline-part-id="${patchID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
patch: { selector: `[data-timeline-part-id="${patchID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
const second = patchFile("src/b.ts", "add")
const third = patchFile("src/old.ts", "delete")
await timeline.send(
partUpdated(
toolPart(
patchID,
"apply_patch",
"running",
{ files: [first.filePath, second.filePath] },
{ metadata: { files: [first, second] } },
),
),
240,
)
await timeline.send(
partUpdated(
toolPart(
patchID,
"apply_patch",
"completed",
{ files: [first.filePath, second.filePath, third.filePath] },
{ metadata: { files: [first, second, third] } },
),
),
800,
)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"incremental-patch",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["patch", "following"] },
{ type: "unique", regions: ["patch", "following"] },
{ type: "stable", regions: ["patch", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: ["following"], maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["patch", "following"] },
],
{ perMarker: true },
),
)
await expect(trigger).toHaveAttribute("aria-expanded", "true")
await expect(page.locator('[data-scope="apply-patch"] [data-type="delete"]')).toBeVisible()
})
function patchFile(filePath: string, type: "add" | "update" | "delete") {
return {
filePath,
relativePath: filePath,
type,
additions: type === "delete" ? 0 : 4,
deletions: type === "add" ? 0 : 3,
before: type === "add" ? undefined : source(false),
after: type === "delete" ? undefined : source(true),
}
}
function source(changed: boolean) {
return Array.from({ length: 12 }, (_, index) => `export const value${index} = ${changed ? index + 1 : index}\n`).join(
"",
)
}

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import { describe, expect, test } from "bun:test"
import {
assistantMessage,
event,
toolPart,
userMessage,
validateTimelineEvent,
validateTimelineMessages,
type PartSeed,
} from "./fixture"
describe("timeline fixture validation", () => {
test("accepts a valid timeline", () => {
expect(validateTimelineMessages([userMessage(), assistantMessage()])).toHaveLength(2)
})
test("rejects malformed SDK values at runtime", () => {
expect(() =>
assistantMessage([], {
error: { name: "APIError", data: { message: "failed" } } as never,
}),
).toThrow()
expect(() =>
validateTimelineEvent({
directory: "C:/OpenCode/TimelineStability",
payload: {
id: "evt_invalid_status",
type: "session.status",
properties: { sessionID: "ses_timeline_stability", status: { type: "retry", attempt: 1 } },
},
}),
).toThrow()
})
test("rejects duplicate IDs and orphan assistants", () => {
expect(() => validateTimelineMessages([userMessage(), userMessage()])).toThrow(/duplicate message ID/)
expect(() =>
validateTimelineMessages([userMessage(), assistantMessage([], { parentID: "msg_missing_parent" })]),
).toThrow(/parent user/)
})
test("assigns deterministic event IDs", () => {
const first = event("session.status", { sessionID: "ses_timeline_stability", status: { type: "busy" } })
const second = event("session.status", { sessionID: "ses_timeline_stability", status: { type: "idle" } })
expect(first.payload.id).toMatch(/^evt_timeline_\d{4}$/)
expect(Number(second.payload.id.slice(-4))).toBe(Number(first.payload.id.slice(-4)) + 1)
})
})
if (false) {
const userSeed = { id: "prt_type_user", type: "text", text: "typed" } satisfies PartSeed<"user">
userMessage([userSeed])
// @ts-expect-error Tool completion fields are not valid while pending.
toolPart("prt_invalid_pending", "bash", "pending", {}, { output: "impossible" })
// @ts-expect-error Tool completion fields are not valid while running.
toolPart("prt_invalid_running", "bash", "running", {}, { output: "impossible" })
// @ts-expect-error Tool error fields are not valid after completion.
toolPart("prt_invalid_completed", "bash", "completed", {}, { error: "impossible" })
assistantMessage([
// @ts-expect-error Agent references belong to user messages, not assistant messages.
{ id: "prt_invalid_owner", type: "agent", name: "explore", source: { value: "@explore", start: 0, end: 8 } },
])
// @ts-expect-error Retry status events require message and next.
event("session.status", { sessionID: "ses_timeline_stability", status: { type: "retry", attempt: 1 } })
}

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import { base64Encode } from "@opencode-ai/core/util/encode"
import { Event } from "@opencode-ai/schema/event"
import { SessionStatusEvent } from "@opencode-ai/schema/session-status-event"
import { SessionV1 } from "@opencode-ai/schema/session-v1"
import type {
AssistantMessage,
GlobalEvent,
Message,
Part,
Session,
SessionStatus,
ToolPart,
ToolState,
UserMessage,
} from "@opencode-ai/sdk/v2/client"
import { expect, type Page } from "@playwright/test"
import { Schema } from "effect"
import { mockOpenCodeServer } from "../../utils/mock-server"
import { installSseTransport } from "../../utils/sse-transport"
import { expectSessionTitle } from "../../utils/waits"
export const directory = "C:/OpenCode/TimelineStability"
export const projectID = "proj_timeline_stability"
export const sessionID = "ses_timeline_stability"
export const userID = "msg_1000_timeline_user"
export const assistantID = "msg_1001_timeline_assistant"
export const title = "Timeline visual stability"
export const model = { providerID: "opencode", modelID: "claude-opus-4-6", variant: "max" }
type TimelinePayload = Extract<
GlobalEvent["payload"],
{
type:
| "message.updated"
| "message.removed"
| "message.part.updated"
| "message.part.removed"
| "message.part.delta"
| "session.status"
}
>
type DeepReadonly<Value> = Value extends readonly unknown[]
? { readonly [Key in keyof Value]: DeepReadonly<Value[Key]> }
: Value extends object
? { readonly [Key in keyof Value]: DeepReadonly<Value[Key]> }
: Value
export type TimelineEvent = DeepReadonly<Omit<GlobalEvent, "payload"> & { payload: TimelinePayload }>
export type EventPayload = TimelineEvent
export type ToolStatus = ToolState["status"]
export type TimelineMessage = { info: UserMessage; parts: Part[] } | { info: AssistantMessage; parts: Part[] }
type UserPart = Extract<Part, { type: "text" | "file" | "agent" | "subtask" }>
type AssistantPart = Exclude<Part, { type: "agent" | "subtask" }>
type OwnedPart<Owner extends Message["role"]> = Owner extends "user" ? UserPart : AssistantPart
export type PartSeed<Owner extends Message["role"]> =
OwnedPart<Owner> extends infer Candidate
? Candidate extends Part
? Omit<Candidate, "sessionID" | "messageID">
: never
: never
type ToolOptions<State extends ToolStatus> = State extends "pending"
? { output?: never; title?: never; metadata?: never; error?: never }
: State extends "running"
? { title?: string; metadata?: Record<string, unknown>; output?: never; error?: never }
: State extends "error"
? { error?: string; metadata?: Record<string, unknown>; output?: never; title?: never }
: { output?: string; title?: string; metadata?: Record<string, unknown>; error?: never }
const decodeOptions = { errors: "all", onExcessProperty: "error" } as const
const decodeMessage = Schema.decodeUnknownSync(SessionV1.WithParts)
const decodePart = Schema.decodeUnknownSync(SessionV1.Part)
const decodeStatus = Schema.decodeUnknownSync(SessionStatusEvent.Info)
const timelineEventSchema = Schema.Union([
eventSchema("message.updated", SessionV1.Event.MessageUpdated.data),
eventSchema("message.removed", SessionV1.Event.MessageRemoved.data),
eventSchema("message.part.updated", SessionV1.Event.PartUpdated.data),
eventSchema("message.part.removed", SessionV1.Event.PartRemoved.data),
eventSchema("message.part.delta", SessionV1.Event.PartDelta.data),
eventSchema("session.status", SessionStatusEvent.Status.data),
])
const decodeEvent = Schema.decodeUnknownSync(timelineEventSchema)
let eventSequence = 0
export async function setupTimeline(
page: Page,
input: {
messages?: TimelineMessage[]
settings?: Record<string, boolean>
sessions?: Session[]
cpuRate?: number
viewport?: { width: number; height: number }
eventRetry?: number
reducedMotion?: boolean
locale?: string
deviceScaleFactor?: number
seedHistory?: boolean
} = {},
) {
const sessions = input.sessions ?? [session()]
const messages = validateTimelineMessages([
...(input.seedHistory ? historyMessages(18) : []),
...(input.messages ?? [userMessage(), assistantMessage()]),
])
const active = messages.findLast((message) => message.info.role === "assistant")
const initialStatus = decodeStatus(
active?.info.role === "assistant" && active.info.time.completed === undefined ? { type: "busy" } : { type: "idle" },
decodeOptions,
)
const transport = await installSseTransport<EventPayload>(page, {
server: `http://${process.env.PLAYWRIGHT_SERVER_HOST ?? "127.0.0.1"}:${process.env.PLAYWRIGHT_SERVER_PORT ?? "4096"}`,
retry: input.eventRetry ?? 20,
})
await mockOpenCodeServer(page, {
directory,
project: project(),
provider: provider(),
sessions,
sessionStatus: { [sessionID]: initialStatus },
pageMessages: () => ({
items: messages,
}),
})
await page.addInitScript((settings) => {
localStorage.setItem(
"settings.v3",
JSON.stringify({
general: {
editToolPartsExpanded: false,
shellToolPartsExpanded: false,
showReasoningSummaries: false,
showSessionProgressBar: true,
...settings,
},
}),
)
}, input.settings ?? {})
if (input.locale) {
await page.addInitScript((locale) => {
localStorage.setItem("opencode.global.dat:language", JSON.stringify({ locale }))
}, input.locale)
}
if (input.reducedMotion) await page.emulateMedia({ reducedMotion: "reduce" })
await page.setViewportSize(input.viewport ?? { width: 1400, height: 900 })
if (input.deviceScaleFactor) {
const devtools = await page.context().newCDPSession(page)
const viewport = input.viewport ?? { width: 1400, height: 900 }
await devtools.send("Emulation.setDeviceMetricsOverride", {
width: viewport.width,
height: viewport.height,
deviceScaleFactor: input.deviceScaleFactor,
mobile: false,
})
}
await page.goto(`/${base64Encode(directory)}/session/${sessionID}`)
await transport.waitForConnection()
await expectSessionTitle(page, title)
if (input.cpuRate && input.cpuRate > 1) {
const devtools = await page.context().newCDPSession(page)
await devtools.send("Emulation.setCPUThrottlingRate", { rate: input.cpuRate })
}
return {
transport,
async send(event: TimelineEvent, delay = 0) {
const valid = validateTimelineEvent(event)
await transport.send(valid, { marker: describeEvent(valid) })
if (delay) await page.waitForTimeout(delay)
},
async sendAll(sequence: { event: TimelineEvent; delay: number }[]) {
for (const item of sequence) {
const valid = validateTimelineEvent(item.event)
await transport.send(valid, { marker: describeEvent(valid) })
await page.waitForTimeout(item.delay)
}
},
async settle(frames = 3) {
await page.evaluate(
(frames) =>
new Promise<void>((resolve) => {
let remaining = frames
const tick = () => {
remaining--
if (remaining <= 0) return resolve()
requestAnimationFrame(tick)
}
requestAnimationFrame(tick)
}),
frames,
)
},
async waitForPart(partID: string) {
await expect(page.locator(`[data-timeline-part-id="${partID}"]`).first()).toBeVisible()
},
}
}
function describeEvent(event: EventPayload) {
if (event.payload.type === "message.part.updated") {
const part = event.payload.properties.part
return [
event.payload.type,
part.id,
part.type === "tool" ? part.tool : part.type,
part.type === "tool" ? part.state.status : undefined,
]
.filter(Boolean)
.join(":")
}
if (event.payload.type === "session.status") {
const status = event.payload.properties.status
return [event.payload.type, status.type, status.type === "retry" ? status.attempt : undefined]
.filter((value) => value !== undefined)
.join(":")
}
return event.payload.type
}
export function event<const Type extends TimelinePayload["type"]>(
type: Type,
properties: Extract<TimelinePayload, { type: Type }>["properties"],
): TimelineEvent
export function event(type: TimelinePayload["type"], properties: TimelinePayload["properties"]): TimelineEvent {
return validateTimelineEvent({
directory,
payload: { id: `evt_timeline_${String(++eventSequence).padStart(4, "0")}`, type, properties },
})
}
export function validateTimelineEvent(input: unknown): TimelineEvent {
return decodeEvent(input, decodeOptions)
}
export function validateTimelineMessages(input: readonly TimelineMessage[]): TimelineMessage[] {
input.forEach((message) => decodeMessage(message, decodeOptions))
const messages = [...input]
const messageIDs = new Set<string>()
const partIDs = new Set<string>()
const users = new Set(messages.filter((message) => message.info.role === "user").map((message) => message.info.id))
messages.forEach((message) => {
if (messageIDs.has(message.info.id))
throw new Error(`Timeline fixture has duplicate message ID: ${message.info.id}`)
messageIDs.add(message.info.id)
if (message.info.role === "assistant" && !users.has(message.info.parentID))
throw new Error(`Timeline assistant ${message.info.id} must reference a parent user in the fixture`)
message.parts.forEach((part) => {
if (part.sessionID !== message.info.sessionID || part.messageID !== message.info.id)
throw new Error(`Timeline part ${part.id} ownership does not match message ${message.info.id}`)
if (message.info.role === "user" && !["text", "file", "agent", "subtask"].includes(part.type))
throw new Error(`Timeline user message ${message.info.id} cannot own ${part.type} part ${part.id}`)
if (message.info.role === "assistant" && ["agent", "subtask"].includes(part.type))
throw new Error(`Timeline assistant message ${message.info.id} cannot own ${part.type} part ${part.id}`)
if (partIDs.has(part.id)) throw new Error(`Timeline fixture has duplicate part ID: ${part.id}`)
partIDs.add(part.id)
})
})
return messages
}
export async function waitForVisualSettle(page: Page, selectors: string[], stableFrames = 3) {
await page.waitForFunction(
({ selectors, stableFrames }) => {
const elements = selectors.map((selector) => document.querySelector<HTMLElement>(selector))
if (elements.some((element) => !element)) return false
return new Promise<boolean>((resolve) => {
let stable = 0
let previous = ""
const sample = () => {
const signature = JSON.stringify(
elements.map((element) => {
const rect = element!.getBoundingClientRect()
return [Math.round(rect.top * 10), Math.round(rect.bottom * 10), Math.round(rect.height * 10)]
}),
)
stable = signature === previous ? stable + 1 : 0
previous = signature
const ordered = elements
.slice(1)
.every(
(element, index) =>
elements[index]!.getBoundingClientRect().bottom <= element!.getBoundingClientRect().top + 0.5,
)
if (stable >= stableFrames && ordered) return resolve(true)
requestAnimationFrame(sample)
}
requestAnimationFrame(sample)
})
},
{ selectors, stableFrames },
)
}
export function historyMessages(count: number): TimelineMessage[] {
return Array.from({ length: count }, (_, index) => {
const value = String(index).padStart(4, "0")
const historyUserID = `msg_0${value}_history_a_user`
return [
userMessage(undefined, { id: historyUserID, created: 1690000000000 + index * 10_000 }),
assistantMessage(
[
{
id: `prt_0${value}_history_text`,
type: "text",
text: `Historical response ${index}. ${"Existing session content keeps the virtual timeline realistic. ".repeat(5)}`,
},
],
{
id: `msg_0${value}_history_b_assistant`,
parentID: historyUserID,
created: 1690000001000 + index * 10_000,
},
),
]
}).flat()
}
export function partUpdated(part: Part | PartSeed<"assistant">) {
const owned = "messageID" in part ? part : { ...part, sessionID, messageID: assistantID }
decodePart(owned, decodeOptions)
return event("message.part.updated", {
sessionID,
part: owned,
time: 1700000002000,
})
}
export function partDelta(partID: string, delta: string, messageID = assistantID) {
return event("message.part.delta", { sessionID, messageID, partID, field: "text", delta })
}
export function messageUpdated(info: Message) {
return event("message.updated", { sessionID, info })
}
export function status(type: SessionStatus["type"], attempt = 1) {
return event("session.status", {
sessionID,
status: type === "retry" ? { type, attempt, message: "Rate limited", next: 1700000010000 } : { type },
})
}
export function userMessage(
parts?: PartSeed<"user">[],
input: { id?: string; summary?: UserMessage["summary"]; created?: number } = {},
): Extract<TimelineMessage, { info: { role: "user" } }> {
const id = input.id ?? userID
const seeds = parts ?? [userText("Build the timeline stability matrix.", { id: `prt_${id}_text` })]
const message = {
info: {
id,
sessionID,
role: "user",
time: { created: input.created ?? 1700000000000 },
summary: input.summary ?? { diffs: [] },
agent: "build",
model,
},
parts: seeds.map((part) => ({
...part,
sessionID,
messageID: id,
})),
} satisfies Extract<TimelineMessage, { info: { role: "user" } }>
decodeMessage(message, decodeOptions)
return message
}
export function assistantMessage(
parts: PartSeed<"assistant">[] = [],
input: {
id?: string
parentID?: string
completed?: boolean
error?: AssistantMessage["error"]
created?: number
} = {},
): Extract<TimelineMessage, { info: { role: "assistant" } }> {
const id = input.id ?? assistantID
const message = {
info: {
id,
sessionID,
role: "assistant",
time: {
created: input.created ?? 1700000001000,
...(input.completed === false ? {} : { completed: (input.created ?? 1700000001000) + 1_000 }),
},
parentID: input.parentID ?? userID,
modelID: model.modelID,
providerID: model.providerID,
mode: "build",
agent: "build",
path: { cwd: directory, root: directory },
cost: 0.01,
tokens: { input: 100, output: 200, reasoning: 0, cache: { read: 0, write: 0 } },
variant: "max",
...(input.error ? { error: input.error } : {}),
},
parts: parts.map((part) => ({ ...part, sessionID, messageID: id })),
} satisfies Extract<TimelineMessage, { info: { role: "assistant" } }>
decodeMessage(message, decodeOptions)
return message
}
export function userText(
text: string,
input: Partial<Omit<Extract<PartSeed<"user">, { type: "text" }>, "type" | "text">> = {},
): Extract<PartSeed<"user">, { type: "text" }> {
return { id: "prt_user_text", type: "text", text, ...input }
}
export function textPart(id: string, text: string): Extract<PartSeed<"assistant">, { type: "text" }> {
return { id, type: "text", text }
}
export function reasoningPart(id: string, text: string): Extract<PartSeed<"assistant">, { type: "reasoning" }> {
return { id, type: "reasoning", text, time: { start: 1700000001000 } }
}
export function toolPart(
id: string,
tool: string,
state: "pending",
input: Record<string, unknown>,
options?: ToolOptions<"pending">,
): Omit<ToolPart, "sessionID" | "messageID">
export function toolPart(
id: string,
tool: string,
state: "running",
input: Record<string, unknown>,
options?: ToolOptions<"running">,
): Omit<ToolPart, "sessionID" | "messageID">
export function toolPart(
id: string,
tool: string,
state: "completed",
input: Record<string, unknown>,
options?: ToolOptions<"completed">,
): Omit<ToolPart, "sessionID" | "messageID">
export function toolPart(
id: string,
tool: string,
state: "error",
input: Record<string, unknown>,
options?: ToolOptions<"error">,
): Omit<ToolPart, "sessionID" | "messageID">
export function toolPart(
id: string,
tool: string,
state: ToolStatus,
input: Record<string, unknown>,
options: ToolOptions<ToolStatus> = {},
): Omit<ToolPart, "sessionID" | "messageID"> {
const base = { id, type: "tool" as const, callID: `call_${id}`, tool }
if (state === "pending") return { ...base, state: { status: state, input, raw: "" } }
if (state === "running")
return {
...base,
state: {
status: state,
input,
title: options.title,
metadata: options.metadata ?? {},
time: { start: 1700000001000 },
},
}
if (state === "error")
return {
...base,
state: {
status: state,
input,
error: options.error ?? "Tool failed",
metadata: options.metadata ?? {},
time: { start: 1700000001000, end: 1700000002000 },
},
}
return {
...base,
state: {
status: state,
input,
output: options.output ?? "Completed",
title: options.title ?? tool,
metadata: options.metadata ?? {},
time: { start: 1700000001000, end: 1700000002000 },
},
}
}
export function shell(
id: string,
state: ToolStatus,
output = "",
command = `echo ${id}`,
): Omit<ToolPart, "sessionID" | "messageID"> {
if (state === "pending") return toolPart(id, "bash", state, { command })
if (state === "running")
return toolPart(id, "bash", state, { command }, { title: command, metadata: { command, output } })
if (state === "error")
return toolPart(id, "bash", state, { command }, { error: output || undefined, metadata: { command, output } })
return toolPart(id, "bash", state, { command }, { title: command, output, metadata: { command, output } })
}
export function completedAssistantInfo(info: AssistantMessage): AssistantMessage {
return { ...info, time: { ...info.time, completed: 1700000003000 } }
}
export function project() {
return {
id: projectID,
worktree: directory,
vcs: "git",
name: "timeline-stability",
time: { created: 1700000000000, updated: 1700000000000 },
sandboxes: [],
}
}
export function session(input: Partial<Session> = {}): Session {
return {
id: sessionID,
slug: "timeline-stability",
projectID,
directory,
title,
version: "dev",
time: { created: 1700000000000, updated: 1700000000000 },
...input,
}
}
function eventSchema<
const Type extends TimelinePayload["type"],
const Properties extends Schema.Codec<unknown, unknown>,
>(type: Type, properties: Properties) {
return Schema.Struct({
directory: Schema.String,
project: Schema.optional(Schema.String),
workspace: Schema.optional(Schema.String),
payload: Schema.Struct({ id: Event.ID, type: Schema.Literal(type), properties }),
})
}
function provider() {
return {
all: [
{
id: "opencode",
name: "OpenCode",
models: { "claude-opus-4-6": { id: "claude-opus-4-6", name: "Claude Opus 4.6", limit: { context: 200_000 } } },
},
],
connected: ["opencode"],
default: { providerID: "opencode", modelID: "claude-opus-4-6" },
}
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import { assistantMessage, setupTimeline, shell, textPart, toolPart, userMessage, waitForVisualSettle } from "./fixture"
test("expands and collapses a long completed shell without overlap", async ({ page }, testInfo) => {
const shellID = "prt_interaction_01_shell"
const followingID = "prt_interaction_02_following"
await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "completed", lines(50)), textPart(followingID, "Following shell expansion")]),
],
settings: { shellToolPartsExpanded: false },
cpuRate: 4,
seedHistory: true,
})
const trigger = page.locator(`[data-timeline-part-id="${shellID}"] [data-slot="collapsible-trigger"]`)
await waitForVisualSettle(page, [`[data-timeline-part-id="${shellID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
const plan = visualPlan(regions, [
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
])
await startVisualProbe(page, regions)
await trigger.click()
await expect(trigger).toHaveAttribute("aria-expanded", "true")
await page.waitForTimeout(500)
const expanded = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "shell-expand", expanded, plan)
await startVisualProbe(page, regions)
await trigger.click()
await expect(trigger).toHaveAttribute("aria-expanded", "false")
await page.waitForTimeout(500)
const collapsed = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "shell-collapse", collapsed, plan)
})
test("expands and collapses a completed context group without overlap", async ({ page }, testInfo) => {
const ids = [
"prt_interaction_01_read",
"prt_interaction_02_glob",
"prt_interaction_03_grep",
"prt_interaction_04_list",
]
const group = `[data-timeline-part-ids="${ids.join(",")}"]`
const followingID = "prt_interaction_context_following"
await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([
toolPart(ids[0]!, "read", "completed", { filePath: "src/a.ts" }),
toolPart(ids[1]!, "glob", "completed", { path: ".", pattern: "**/*.ts" }),
toolPart(ids[2]!, "grep", "completed", { path: ".", pattern: "stable" }),
toolPart(ids[3]!, "list", "completed", { path: "src" }),
textPart(followingID, "Following context expansion"),
]),
],
cpuRate: 4,
seedHistory: true,
})
const trigger = page.locator(`${group} [data-slot="collapsible-trigger"]`)
await waitForVisualSettle(page, [group, `[data-timeline-part-id="${followingID}"]`])
for (const [name, expanded] of [
["context-expand", true],
["context-collapse", false],
["context-reexpand", true],
] as const) {
const regions = defineVisualRegions({
context: { selector: group, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await trigger.click()
await expect(trigger).toHaveAttribute("aria-expanded", String(expanded))
await page.waitForTimeout(500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
name,
trace,
visualPlan(regions, [
{ type: "required", regions: ["context", "following"] },
{ type: "unique", regions: ["context", "following"] },
{ type: "stable", regions: ["context", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["context", "following"] },
]),
)
}
})
test("expands and collapses an edit diff without moving twice", async ({ page }, testInfo) => {
const editID = "prt_interaction_edit"
const followingID = "prt_interaction_edit_following"
await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([
toolPart(
editID,
"edit",
"completed",
{ filePath: "src/edit.ts" },
{
metadata: {
filediff: {
file: "src/edit.ts",
additions: 40,
deletions: 40,
before: source(40, false),
after: source(40, true),
},
},
},
),
textPart(followingID, "Following edit expansion"),
]),
],
settings: { editToolPartsExpanded: false },
cpuRate: 4,
seedHistory: true,
})
const trigger = page.locator(`[data-timeline-part-id="${editID}"] [data-slot="collapsible-trigger"]`).first()
await waitForVisualSettle(page, [`[data-timeline-part-id="${editID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
edit: { selector: `[data-timeline-part-id="${editID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await trigger.click()
await expect(trigger).toHaveAttribute("aria-expanded", "true")
await page.waitForTimeout(900)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"edit-expand",
trace,
visualPlan(regions, [
{ type: "required", regions: ["edit", "following"] },
{ type: "unique", regions: ["edit", "following"] },
{ type: "stable", regions: ["edit", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0, maxReversals: 1 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["edit", "following"] },
]),
)
})
test("shows all and expands historical diff summary without overlap", async ({ page }, testInfo) => {
const firstUser = userMessage(undefined, {
summary: {
diffs: Array.from({ length: 12 }, (_, index) => ({
file: `src/diff-${index}.ts`,
additions: 1,
deletions: 1,
patch: `@@ -1 +1 @@\n-export const value = ${index}\n+export const value = ${index + 1}`,
})),
},
})
const nextUserID = "msg_2000_diff_interaction_user"
await setupTimeline(page, {
messages: [
firstUser,
assistantMessage(),
userMessage(undefined, { id: nextUserID, created: 1700000010000 }),
assistantMessage([], {
id: "msg_2001_diff_interaction_assistant",
parentID: nextUserID,
created: 1700000011000,
}),
],
cpuRate: 4,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
await scroller.evaluate((element) => (element.scrollTop = 0))
const diff = page.locator('[data-timeline-row="DiffSummary"]')
const following = page.locator(`[data-message-id="${nextUserID}"]`).first()
await expect(diff).toBeVisible()
const regions = defineVisualRegions({
diff: { selector: '[data-timeline-row="DiffSummary"]' },
following: { selector: `[data-message-id="${nextUserID}"]` },
})
await startVisualProbe(page, regions)
await page.getByText(/show all/i).click()
await page.waitForTimeout(500)
await diff.locator('[data-slot="session-turn-diff-trigger"]').first().click()
await page.waitForTimeout(900)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"diff-summary-expand",
trace,
visualPlan(regions, [
{ type: "required", regions: ["diff", "following"] },
{ type: "unique", regions: ["diff", "following"] },
{ type: "stable", regions: ["diff", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 1, maxReversals: 2 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["diff", "following"] },
]),
)
})
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}
function source(count: number, changed: boolean) {
return Array.from(
{ length: count },
(_, index) => `export const value${index} = ${changed ? index + 1 : index}\n`,
).join("")
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
mapVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
completedAssistantInfo,
messageUpdated,
partDelta,
partUpdated,
reasoningPart,
setupTimeline,
shell,
status,
textPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
test.describe("timeline visual lifecycle stability", () => {
test("streams empty, short, and long parallel shells to staggered completion", async ({ page }, testInfo) => {
test.setTimeout(180_000)
const ids = ["prt_parallel_01_empty", "prt_parallel_02_short", "prt_parallel_03_long"] as const
const initial = ids.map((id) => shell(id, "running"))
const followingID = "prt_parallel_04_following"
const assistant = assistantMessage([...initial, textPart(followingID, "Following all parallel shells.")], {
completed: false,
})
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistant],
settings: { shellToolPartsExpanded: true, showReasoningSummaries: true },
cpuRate: 4,
eventRetry: 24,
seedHistory: true,
})
await timeline.send(status("busy"), 150)
for (const id of ids) await timeline.waitForPart(id)
const scroller = page.locator(".scroll-view__viewport", {
has: page.locator('[data-timeline-row="AssistantPart"]'),
})
await scroller.evaluate((element) => (element.scrollTop = element.scrollHeight))
const regions = defineVisualRegions({
prt_shell_empty: shellRegion(ids[0]),
prt_shell_short: shellRegion(ids[1]),
prt_shell_long: shellRegion(ids[2]),
following: shellRegion(followingID),
})
await waitForVisualSettle(page, [`[data-timeline-part-id="${followingID}"]`])
await startVisualProbe(page, regions)
await timeline.sendAll([
{ event: partUpdated(shell(ids[0]!, "completed", "")), delay: 180 },
{ event: partUpdated(shell(ids[2]!, "running", lines(10))), delay: 70 },
{ event: partUpdated(shell(ids[1]!, "running", lines(2))), delay: 110 },
{ event: partUpdated(shell(ids[2]!, "running", lines(25))), delay: 80 },
{ event: partUpdated(shell(ids[1]!, "completed", lines(2))), delay: 260 },
{ event: partUpdated(shell(ids[2]!, "running", lines(50))), delay: 100 },
{ event: partUpdated(shell(ids[2]!, "completed", lines(50))), delay: 450 },
{ event: messageUpdated(completedAssistantInfo(assistant.info)), delay: 100 },
{ event: status("idle"), delay: 700 },
])
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"parallel-shells",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["prt_shell_empty", "prt_shell_short", "prt_shell_long", "following"] },
{ type: "unique", regions: ["prt_shell_empty", "prt_shell_short", "prt_shell_long"] },
{ type: "stable", regions: ["prt_shell_empty", "prt_shell_short", "prt_shell_long", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0, maxReversals: 4 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["prt_shell_empty", "prt_shell_short", "prt_shell_long", "following"] },
],
{ perMarker: true },
),
)
await expect(page.locator(`[data-timeline-part-id="${ids[2]}"] [data-slot="bash-pre"]`)).toContainText("line 50")
const short = page.locator(`[data-timeline-part-id="${ids[1]}"]`)
await short.locator('[data-slot="collapsible-trigger"]').click()
await expect(short.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "false")
await timeline.send(partUpdated(textPart("prt_late_sibling", "A later sibling rerender.")), 250)
await expect(short.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "false")
})
test("replaces thinking with streamed reasoning and text without a blank visible turn", async ({
page,
}, testInfo) => {
const reasoningID = "prt_reasoning_visible"
const textID = "prt_streamed_text"
const assistant = assistantMessage([], { completed: false })
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistant],
settings: { showReasoningSummaries: true },
cpuRate: 4,
})
await timeline.send(status("busy"), 120)
await expect(page.locator('[data-timeline-row="Thinking"]')).toBeVisible()
const regions = defineVisualRegions({
thinking: { selector: '[data-timeline-row="Thinking"]' },
reasoning: {
selector: `[data-timeline-part-id="${reasoningID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
text: { selector: `[data-timeline-part-id="${textID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(reasoningPart(reasoningID, "")), 100)
await expect(page.locator(`[data-timeline-part-id="${reasoningID}"]`)).toHaveCount(0)
await timeline.send(partUpdated(reasoningPart(reasoningID, "## Planning\n\nChecking the visible timeline.")), 160)
await timeline.waitForPart(reasoningID)
await expect(page.locator('[data-timeline-row="Thinking"]')).toHaveCount(0)
await timeline.send(partUpdated(textPart(textID, "Starting")), 100)
await timeline.send(partDelta(textID, " **stable"), 90)
await timeline.send(partDelta(textID, " output** with `code` and [a link"), 130)
await timeline.send(partDelta(textID, "](https://example.com)."), 220)
await timeline.send(messageUpdated(completedAssistantInfo(assistant.info)), 120)
await timeline.send(status("idle"), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"reasoning-text-handoff",
trace,
visualPlan(regions, [
{ type: "required", regions: ["reasoning", "text"] },
{ type: "continuous-any", regions: ["thinking", "reasoning", "text"] },
{ type: "unique", regions: ["reasoning", "text"] },
{ type: "stable", regions: ["reasoning", "text"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxReversals: 4 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["reasoning", "text"] },
]),
)
await expect(page.locator(`[data-timeline-part-id="${textID}"]`)).toContainText("stable output")
})
})
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}
function shellRegion(id: string) {
return { selector: `[data-timeline-part-id="${id}"]`, closest: '[data-timeline-row="AssistantPart"]' }
}

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import { expect, test } from "@playwright/test"
import {
analyzeVisualObservations,
defineVisualRegions,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import { assistantMessage, setupTimeline, textPart, userMessage } from "./fixture"
test("detects blanking caused by ancestor opacity", async ({ page }) => {
const partID = "prt_oracle_ancestor_opacity"
await setupTimeline(page, { messages: [userMessage(), assistantMessage([textPart(partID, "Visible content")])] })
const row = page.locator(`[data-timeline-part-id="${partID}"]`).first()
const regions = defineVisualRegions({
content: { selector: `[data-timeline-part-id="${partID}"]` },
})
await startVisualProbe(page, regions)
await row.evaluate((element) => {
element.parentElement!.style.opacity = "0"
})
await page.waitForTimeout(50)
await row.evaluate((element) => {
element.parentElement!.style.opacity = "1"
})
await page.waitForTimeout(50)
const trace = await stopVisualProbe<keyof typeof regions>(page)
const issues = analyzeVisualObservations(
trace.samples,
visualPlan(regions, [
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all" },
{ type: "label-stability", regions: "all" },
]),
)
expect(issues.some((issue) => issue.includes("blanked between visible frames"))).toBe(true)
})
test("detects root opacity when probing descendant opacity", async ({ page }) => {
const partID = "prt_oracle_descendant_opacity"
await setupTimeline(page, { messages: [userMessage(), assistantMessage([textPart(partID, "Visible content")])] })
const row = page.locator(`[data-timeline-part-id="${partID}"]`).first()
await row.evaluate((element) => {
element.innerHTML = '<span data-probe-opacity="true">Visible content</span>'
})
const regions = defineVisualRegions({
content: {
selector: `[data-timeline-part-id="${partID}"]`,
opacitySelectors: ['[data-probe-opacity="true"]'],
},
})
await startVisualProbe(page, regions)
await row.evaluate((element) => {
;(element as HTMLElement).style.opacity = "0"
})
await page.waitForTimeout(50)
await row.evaluate((element) => {
;(element as HTMLElement).style.opacity = "1"
})
await page.waitForTimeout(50)
const trace = await stopVisualProbe<keyof typeof regions>(page)
const issues = analyzeVisualObservations(
trace.samples,
visualPlan(regions, [
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all" },
{ type: "label-stability", regions: "all" },
]),
)
expect(issues.some((issue) => issue.includes("blanked between visible frames"))).toBe(true)
})

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import config from "../playwright.config"
export default {
...config,
testDir: ".",
testMatch: "**/*.spec.ts",
outputDir: "../../test-results/timeline-stability",
reporter: [["html", { outputFolder: "../../playwright-report/timeline-stability", open: "never" }], ["line"]],
retries: 0,
workers: 1,
use: {
...config.use,
trace: "retain-on-failure",
screenshot: "only-on-failure",
video: "retain-on-failure",
},
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
shell,
textPart,
userMessage,
type TimelineMessage,
} from "./fixture"
test("does not reverse visible rows when the user wheels during shell remeasurement", async ({ page }, testInfo) => {
const shellID = "prt_wheel_01_shell"
const followingID = "prt_wheel_02_following"
const timeline = await setupTimeline(page, {
messages: [
...history(12),
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following wheel interaction")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
reducedMotion: true,
seedHistory: true,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "running", lines(30))), 80)
await scroller.evaluate((element) =>
element.dispatchEvent(new WheelEvent("wheel", { bubbles: true, cancelable: true, deltaY: -180 })),
)
await scroller.evaluate((element) => (element.scrollTop -= 180))
await timeline.send(partUpdated(shell(shellID, "running", lines(50))), 250)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "wheel-during-resize", trace, rowPairPlan(regions, 1))
})
test("does not pull a keyboard-scrolled user during shell remeasurement", async ({ page }, testInfo) => {
const shellID = "prt_keyboard_01_shell"
const followingID = "prt_keyboard_02_following"
const timeline = await setupTimeline(page, {
messages: [
...history(12),
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following keyboard interaction")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
await scroller.focus()
for (let index = 0; index < 3; index++) {
await scroller.press("PageUp")
await page.waitForTimeout(250)
}
await expect
.poll(() => scroller.evaluate((element) => element.scrollHeight - element.clientHeight - element.scrollTop), {
timeout: 20_000,
})
.toBeGreaterThan(80)
await page.waitForFunction(() => {
const root = [...document.querySelectorAll<HTMLElement>(".scroll-view__viewport")].find((element) =>
element.querySelector("[data-timeline-row]"),
)
if (!root) return false
return new Promise<boolean>((resolve) => {
const top = root.scrollTop
requestAnimationFrame(() => requestAnimationFrame(() => resolve(Math.abs(root.scrollTop - top) <= 0.5)))
})
})
const anchor = await scroller.evaluate((element) => {
const view = element.getBoundingClientRect()
return [...element.querySelectorAll<HTMLElement>("[data-timeline-key]")].find((row) => {
const rect = row.getBoundingClientRect()
return rect.top >= view.top + 40 && rect.bottom <= view.bottom - 40
})?.dataset.timelineKey
})
expect(anchor).toBeTruthy()
const regions = defineVisualRegions({
anchor: { selector: `[data-timeline-key="${anchor}"]` },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "running", lines(50))), 400)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "keyboard-during-resize", trace, anchorPlan(regions))
})
test("tracks keyboard scrolling from a focused timeline descendant", async ({ page }, testInfo) => {
const shellID = "prt_descendant_keyboard_01_shell"
const timeline = await setupTimeline(page, {
messages: [...history(12), userMessage(), assistantMessage([shell(shellID, "completed", lines(5))])],
settings: { shellToolPartsExpanded: false },
cpuRate: 4,
reducedMotion: true,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
const row = page.locator(`[data-timeline-part-id="${shellID}"]`).first()
const trigger = page.locator(`[data-timeline-part-id="${shellID}"] [data-slot="collapsible-trigger"]`)
await row.evaluate((element) => element.setAttribute("tabindex", "0"))
await row.focus()
for (let index = 0; index < 3; index++) {
await row.press("PageUp")
await page.waitForTimeout(250)
}
await expect
.poll(() => scroller.evaluate((element) => element.scrollHeight - element.clientHeight - element.scrollTop))
.toBeGreaterThan(5)
const anchor = await scroller.evaluate((element) => {
const view = element.getBoundingClientRect()
return [...element.querySelectorAll<HTMLElement>("[data-timeline-key]")].find((row) => {
const rect = row.getBoundingClientRect()
return rect.top >= view.top + 40 && rect.bottom <= view.bottom - 40
})?.dataset.timelineKey
})
expect(anchor).toBeTruthy()
const regions = defineVisualRegions({
anchor: { selector: `[data-timeline-key="${anchor}"]` },
})
await startVisualProbe(page, regions)
await trigger.click()
await page.waitForTimeout(300)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "descendant-keyboard-resize", trace, anchorPlan(regions))
})
test("does not claim keyboard scrolling owned by a nested scrollable", async ({ page }) => {
const shellID = "prt_nested_keyboard_shell"
await setupTimeline(page, {
messages: [userMessage(), assistantMessage([shell(shellID, "completed", lines(50))])],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
reducedMotion: true,
seedHistory: true,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
const nested = page.locator(`[data-timeline-part-id="${shellID}"] [data-scrollable]`)
await nested.evaluate((element) => (element.scrollTop = element.scrollHeight))
await nested.focus()
await page.waitForFunction(() => {
const root = [...document.querySelectorAll<HTMLElement>(".scroll-view__viewport")].find((element) =>
element.querySelector("[data-timeline-row]"),
)
if (!root) return false
return new Promise<boolean>((resolve) => {
const top = root.scrollTop
requestAnimationFrame(() => requestAnimationFrame(() => resolve(Math.abs(root.scrollTop - top) <= 0.5)))
})
})
const before = await scroller.evaluate((element) => element.scrollTop)
const nestedBefore = await nested.evaluate((element) => element.scrollTop)
await nested.press("PageUp")
await page.waitForTimeout(300)
expect(await scroller.evaluate((element) => element.scrollTop)).toBe(before)
expect(await nested.evaluate((element) => element.scrollTop)).toBeLessThan(nestedBefore)
await nested.evaluate((element) => (element.scrollTop = 0))
await scroller.evaluate((element) => (element.scrollTop = Math.min(300, element.scrollHeight - element.clientHeight)))
const boundaryBefore = await scroller.evaluate((element) => element.scrollTop)
expect(boundaryBefore).toBeGreaterThan(0)
await nested.press("PageUp")
await expect.poll(() => scroller.evaluate((element) => element.scrollTop)).toBeLessThan(boundaryBefore)
const nonOverflowing = page.locator(`[data-timeline-part-id="${shellID}"]`).first()
await nonOverflowing.evaluate((element) => {
element.setAttribute("data-scrollable", "")
element.setAttribute("tabindex", "0")
})
await nonOverflowing.focus()
const nonOverflowBefore = await scroller.evaluate((element) => element.scrollTop)
await nonOverflowing.press("PageUp")
await expect.poll(() => scroller.evaluate((element) => element.scrollTop)).toBeLessThan(nonOverflowBefore)
})
test("jump to latest lands on stable final rows after offscreen growth", async ({ page }, testInfo) => {
const shellID = "prt_jump_01_shell"
const followingID = "prt_jump_02_following"
const timeline = await setupTimeline(page, {
messages: [
...history(20),
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Latest visible row")], { completed: false }),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
await scroller.evaluate(
(element) => (element.scrollTop = Math.max(0, element.scrollHeight - element.clientHeight - 600)),
)
await timeline.send(partUpdated(shell(shellID, "running", lines(50))), 300)
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await page.getByRole("button", { name: /Jump to latest/i }).click()
await expect(page.locator(`[data-timeline-part-id="${followingID}"]`)).toBeVisible()
await page.waitForTimeout(600)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"jump-latest",
trace,
visualPlan(regions, [
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 1 },
{ type: "label-stability", regions: "all" },
{ type: "acquire-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
]),
)
})
test("handles a single row taller than the viewport", async ({ page }, testInfo) => {
const shellID = "prt_tall_01_shell"
const followingID = "prt_tall_02_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "After tall row")], { completed: false }),
],
settings: { shellToolPartsExpanded: true },
viewport: { width: 900, height: 360 },
cpuRate: 4,
seedHistory: true,
})
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "completed", lines(100))), 700)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"taller-than-viewport",
trace,
visualPlan(regions, [
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
]),
)
})
function history(count: number): TimelineMessage[] {
return Array.from({ length: count }, (_, index) => {
const prefix = `msg_${String(index).padStart(4, "0")}_scroll`
const userID = `${prefix}_a_user`
return [
userMessage(undefined, { id: userID, created: 1690000000000 + index * 10_000 }),
assistantMessage(
[textPart(`prt_${String(index).padStart(4, "0")}_scroll`, `History ${index}. ${"content ".repeat(30)}`)],
{
id: `${prefix}_b_assistant`,
parentID: userID,
created: 1690000001000 + index * 10_000,
},
),
]
}).flat()
}
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}
function rowPairPlan(
regions: Record<"shell" | "following", { selector: string; closest?: string }>,
maxPositionReversals: number,
) {
return visualPlan(regions, [
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["shell", "following"] },
])
}
function anchorPlan(regions: Record<"anchor", { selector: string; closest?: string }>) {
return visualPlan(regions, [
{ type: "required", regions: ["anchor"] },
{ type: "unique", regions: ["anchor"] },
{ type: "stable", regions: ["anchor"] },
{ type: "fixed", regions: ["anchor"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
])
}

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import { test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
setupTimeline,
shell,
textPart,
userMessage,
waitForVisualSettle,
} from "./fixture"
const profiles = [
{
name: "empty running to completed",
updates: [{ state: "completed" as const, output: "", delay: 350 }],
},
{
name: "50 lines arriving incrementally",
updates: [
{ state: "running" as const, output: lines(1), delay: 100 },
{ state: "running" as const, output: lines(10), delay: 160 },
{ state: "running" as const, output: lines(25), delay: 90 },
{ state: "running" as const, output: lines(50), delay: 220 },
{ state: "completed" as const, output: lines(50), delay: 500 },
],
},
{
name: "wide ANSI and CRLF output",
updates: [
{
state: "running" as const,
output: Array.from({ length: 20 }, (_, index) => `\u001b[32mline ${index}\u001b[0m ${"wide-".repeat(30)}`).join(
"\r\n",
),
delay: 240,
},
{
state: "completed" as const,
output: Array.from({ length: 20 }, (_, index) => `line ${index} ${"wide-".repeat(30)}`).join("\n"),
delay: 500,
},
],
},
] as const
for (const profile of profiles) {
test(`keeps rows stable for shell ${profile.name}`, async ({ page }, testInfo) => {
const shellID = `prt_matrix_${profiles.indexOf(profile)}_01_shell`
const followingID = `prt_matrix_${profiles.indexOf(profile)}_02_following`
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following shell row")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
seedHistory: true,
})
const scroller = page.locator(".scroll-view__viewport", { has: page.locator("[data-timeline-row]") })
await scroller.evaluate((element) => (element.scrollTop = element.scrollHeight))
await waitForVisualSettle(page, [
`[data-timeline-part-id="${shellID}"]`,
`[data-timeline-part-id="${followingID}"]`,
])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
for (const update of profile.updates) {
await timeline.send(partUpdated(shell(shellID, update.state, update.output)), update.delay)
}
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
`shell-${profiles.indexOf(profile)}`,
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0, maxReversals: 1 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
),
)
})
}
test("keeps following row stable when a collapsed shell receives 50 lines", async ({ page }, testInfo) => {
const shellID = "prt_matrix_collapsed_01_shell"
const followingID = "prt_matrix_collapsed_02_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running"), textPart(followingID, "Following collapsed shell")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: false },
cpuRate: 4,
seedHistory: true,
})
await waitForVisualSettle(page, [`[data-timeline-part-id="${shellID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(shell(shellID, "running", lines(50))), 240)
await timeline.send(partUpdated(shell(shellID, "completed", lines(50))), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"collapsed-shell",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: ["following"], maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
),
)
})
test("keeps rows stable when a running shell becomes an error", async ({ page }, testInfo) => {
const shellID = "prt_matrix_error_01_shell"
const followingID = "prt_matrix_error_02_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([shell(shellID, "running", lines(10)), textPart(followingID, "Following failed shell")], {
completed: false,
}),
],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
seedHistory: true,
})
await waitForVisualSettle(page, [`[data-timeline-part-id="${shellID}"]`, `[data-timeline-part-id="${followingID}"]`])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
partUpdated({
...shell(shellID, "error"),
state: {
status: "error",
input: { command: `echo ${shellID}` },
error: "Command failed after output",
metadata: {},
time: { start: 1700000001000, end: 1700000002000 },
},
}),
500,
)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"shell-error",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: ["following"], maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
),
)
})
test("keeps rows stable when later text arrives before shell output", async ({ page }, testInfo) => {
const shellID = "prt_late_text_01_shell"
const followingID = "prt_late_text_02_following"
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistantMessage([shell(shellID, "running")], { completed: false })],
settings: { shellToolPartsExpanded: true },
cpuRate: 4,
seedHistory: true,
})
await waitForVisualSettle(page, [`[data-timeline-part-id="${shellID}"]`])
const regions = defineVisualRegions({
shell: { selector: `[data-timeline-part-id="${shellID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: `[data-timeline-part-id="${followingID}"]`,
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(textPart(followingID, "Later assistant content arrived before shell output.")), 240)
await timeline.send(partUpdated(shell(shellID, "running", lines(20))), 300)
await timeline.send(partUpdated(shell(shellID, "completed", lines(20))), 600)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"late-text-before-shell-output",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["shell", "following"] },
{ type: "unique", regions: ["shell", "following"] },
{ type: "stable", regions: ["shell"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["shell", "following"] },
],
{ perMarker: true },
),
)
})
function lines(count: number) {
return Array.from({ length: count }, (_, index) => `line ${index + 1}`).join("\n")
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
partUpdated,
session,
sessionID,
setupTimeline,
textPart,
toolPart,
userMessage,
} from "./fixture"
test("adds a task child-session link without replacing the task row", async ({ page }, testInfo) => {
const taskID = "prt_task_link"
const childID = "ses_task_child"
const input = { description: "Inspect child", subagent_type: "explore" }
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistantMessage([toolPart(taskID, "task", "running", input)], { completed: false })],
sessions: [session(), session({ id: childID, parentID: sessionID, title: "Inspect child" })],
cpuRate: 4,
})
const regions = defineVisualRegions({
task: { selector: `[data-timeline-part-id="${taskID}"] [data-slot="collapsible-trigger"]` },
})
await startVisualProbe(page, regions)
await timeline.send(
partUpdated(toolPart(taskID, "task", "completed", input, { metadata: { sessionId: childID } })),
500,
)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"task-link",
trace,
visualPlan(regions, [
{ type: "required", regions: ["task"] },
{ type: "unique", regions: ["task"] },
{ type: "stable", regions: ["task"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
]),
)
await expect(
page.locator(`a[href$="/session/${childID}"]`, { has: page.locator('[data-component="task-tool-card"]') }),
).toBeVisible()
})
test("changes generic tool arguments without replacing the row", async ({ page }, testInfo) => {
const toolID = "prt_generic_mutation"
const followingID = "prt_generic_mutation_following"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage(
[
toolPart(toolID, "mcp_probe", "running", { target: "one", count: 1 }),
textPart(followingID, "Following generic tool"),
],
{ completed: false },
),
],
cpuRate: 4,
})
const regions = defineVisualRegions({
tool: { selector: `[data-timeline-part-id="${toolID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
partUpdated(toolPart(toolID, "mcp_probe", "running", { target: "two", count: 2, mode: "deep" })),
200,
)
await timeline.send(
partUpdated(toolPart(toolID, "mcp_probe", "completed", { target: "two", count: 2, mode: "deep" })),
400,
)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"generic-mutation",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["tool", "following"] },
{ type: "unique", regions: ["tool", "following"] },
{ type: "stable", regions: ["tool", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["tool", "following"] },
],
{ perMarker: true },
),
)
})

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantMessage,
directory,
partUpdated,
session,
sessionID,
setupTimeline,
status,
textPart,
toolPart,
userMessage,
} from "./fixture"
test.describe("timeline tool state stability", () => {
test("moves lightweight tools through pending, running, and completed without replacing rows", async ({
page,
}, testInfo) => {
const ids = ["webfetch", "websearch", "task", "skill", "custom"] as const
const inputs = {
webfetch: { url: "https://example.com/docs" },
websearch: { query: "timeline stability" },
task: { description: "Inspect timeline", subagent_type: "explore" },
skill: { name: "stability" },
custom: { target: "timeline", depth: 2 },
}
const names = { webfetch: "webfetch", websearch: "websearch", task: "task", skill: "skill", custom: "mcp_probe" }
const questionID = "prt_state_question"
const todoID = "prt_state_todo"
const initial = [
...ids.map((id) => toolPart(`prt_state_${id}`, names[id], "pending", inputs[id])),
toolPart(questionID, "question", "pending", questionInput()),
toolPart(todoID, "todowrite", "pending", { todos: [{ content: "Hidden", status: "pending" }] }),
textPart("prt_state_following", "Following lightweight tools"),
]
const childID = "ses_timeline_child"
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistantMessage(initial, { completed: false })],
sessions: [session(), session({ id: childID, parentID: sessionID, title: "Inspect timeline" })],
cpuRate: 4,
})
await timeline.send(status("busy"), 120)
for (const id of ids) await timeline.waitForPart(`prt_state_${id}`)
await expect(page.locator(`[data-timeline-part-id="${questionID}"]`)).toHaveCount(0)
await expect(page.locator(`[data-timeline-part-id="${todoID}"]`)).toHaveCount(0)
const regionIDs = [
"prt_state_webfetch",
"prt_state_websearch",
"prt_state_task",
"prt_state_skill",
"prt_state_custom",
] as const
const regions = defineVisualRegions({
prt_state_webfetch: toolRegion(regionIDs[0]),
prt_state_websearch: toolRegion(regionIDs[1]),
prt_state_task: toolRegion(regionIDs[2]),
prt_state_skill: toolRegion(regionIDs[3]),
prt_state_custom: toolRegion(regionIDs[4]),
})
await startVisualProbe(page, regions)
for (const [index, id] of ids.entries()) {
await timeline.send(
partUpdated(toolPart(`prt_state_${id}`, names[id], "running", inputs[id])),
[80, 240, 100, 360, 140][index],
)
}
for (const [index, id] of ["skill", "webfetch", "custom", "task", "websearch"].entries()) {
const key = id as (typeof ids)[number]
const metadata = key === "task" ? { sessionId: childID } : key === "websearch" ? { provider: "exa" } : {}
const output = key === "websearch" ? "Result https://example.com/result" : "Completed"
await timeline.send(
partUpdated(toolPart(`prt_state_${key}`, names[key], "completed", inputs[key], { metadata, output })),
[110, 70, 280, 130, 420][index],
)
}
await timeline.send(
partUpdated(
toolPart(questionID, "question", "completed", questionInput(), { metadata: { answers: [["Keep it stable"]] } }),
),
350,
)
await timeline.waitForPart(questionID)
await timeline.send(status("idle"), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"lightweight-tools",
trace,
visualPlan(regions, [
{ type: "required", regions: regionIDs },
{ type: "unique", regions: regionIDs },
{ type: "stable", regions: regionIDs },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxReversals: 4 },
{ type: "label-stability", regions: "all" },
]),
)
await expect(page.locator(`[data-timeline-part-id="${questionID}"]`)).toContainText("Keep it stable")
await expect(page.locator(`[data-timeline-part-id="${todoID}"]`)).toHaveCount(0)
await expect(
page.locator(`a[href$="/session/${childID}"]`, { has: page.locator('[data-component="task-tool-card"]') }),
).toBeVisible()
await expect(page.getByRole("button", { name: /Exa Web Search/ })).toBeVisible()
})
test("keeps an expanded mixed context group stable through staggered completion and error", async ({
page,
}, testInfo) => {
const ids = ["prt_ctx_01_read", "prt_ctx_02_glob", "prt_ctx_03_grep", "prt_ctx_04_list"]
const tools = ["read", "glob", "grep", "list"]
const inputs = [
{ filePath: "src/a.ts", offset: 0, limit: 120 },
{ path: directory, pattern: "**/*.ts" },
{ path: directory, pattern: "stability", include: "*.ts" },
{ path: "src" },
]
const context = ids.map((id, index) => toolPart(id, tools[index]!, "pending", inputs[index]!))
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([...context, textPart("prt_ctx_following", "Following context")], { completed: false }),
],
cpuRate: 4,
})
await timeline.send(status("busy"), 100)
const groupSelector = `[data-timeline-part-ids="${ids.join(",")}"]`
const group = page.locator(groupSelector)
await expect(group).toBeVisible()
await group.locator('[data-slot="collapsible-trigger"]').click()
await expect(group.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "true")
const regions = defineVisualRegions({
status: {
selector: `${groupSelector} [data-component="tool-status-title"]`,
opacitySelectors: ['[data-slot="tool-status-active"]', '[data-slot="tool-status-done"]'],
},
context: { selector: groupSelector, closest: '[data-timeline-row="AssistantPart"]' },
following: {
selector: '[data-timeline-part-id="prt_ctx_following"]',
closest: '[data-timeline-row="AssistantPart"]',
},
})
await startVisualProbe(page, regions)
for (const [index, delay] of [90, 260, 70, 380].entries()) {
await timeline.send(partUpdated(toolPart(ids[index]!, tools[index]!, "running", inputs[index]!)), delay)
}
await timeline.send(partUpdated(toolPart(ids[1]!, tools[1]!, "completed", inputs[1]!)), 130)
await timeline.send(partUpdated(toolPart(ids[3]!, tools[3]!, "completed", inputs[3]!)), 210)
await timeline.send(
partUpdated(toolPart(ids[0]!, tools[0]!, "error", inputs[0]!, { error: "Read interrupted" })),
110,
)
await timeline.send(partUpdated(toolPart(ids[2]!, tools[2]!, "completed", inputs[2]!)), 250)
await expect(group.locator('[data-component="tool-status-title"]')).toHaveAttribute("aria-label", "Explored")
await timeline.send(status("idle"), 700)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"mixed-context",
trace,
visualPlan(regions, [
{ type: "required", regions: ["context", "following"] },
{ type: "unique", regions: ["context"] },
{ type: "stable", regions: ["context"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxReversals: 4 },
{ type: "label-stability", regions: "all" },
{ type: "flow", regions: ["context", "following"] },
]),
)
await expect(group.locator('[data-component="tool-status-title"]')).toHaveAttribute("aria-label", "Explored")
await expect(group.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "true")
await group.locator('[data-slot="collapsible-trigger"]').click()
await expect(group.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "false")
await timeline.send(partUpdated(textPart("prt_ctx_late_sibling", "Later sibling content")), 200)
await expect(group.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "false")
await group.locator('[data-slot="collapsible-trigger"]').click()
await expect(group.locator('[data-slot="collapsible-trigger"]')).toHaveAttribute("aria-expanded", "true")
})
})
function questionInput() {
return { questions: [{ header: "Stability", question: "Keep it stable?", options: [] }] }
}
function toolRegion(id: string) {
return { selector: `[data-timeline-part-id="${id}"]`, closest: '[data-timeline-row="AssistantPart"]' }
}

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import { expect, test } from "@playwright/test"
import {
defineVisualRegions,
reportVisualStability,
startVisualProbe,
stopVisualProbe,
visualPlan,
} from "../../utils/visual-stability"
import {
assistantID,
assistantMessage,
completedAssistantInfo,
event,
messageUpdated,
partDelta,
partUpdated,
setupTimeline,
shell,
status,
textPart,
toolPart,
userMessage,
} from "./fixture"
test("keeps unchanged siblings stable while a middle part is inserted and removed", async ({ page }, testInfo) => {
const firstID = "prt_mutation_01_first"
const middleID = "prt_mutation_02_middle"
const lastID = "prt_mutation_03_last"
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage([textPart(firstID, "First stable row"), textPart(lastID, "Last stable row")], {
completed: false,
}),
],
cpuRate: 4,
})
const regions = defineVisualRegions({
first: { selector: `[data-timeline-part-id="${firstID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
last: { selector: `[data-timeline-part-id="${lastID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partUpdated(textPart(middleID, "Inserted middle row. ".repeat(12))), 350)
await expect(page.locator(`[data-timeline-part-id="${middleID}"]`)).toBeVisible()
await timeline.send(
event("message.part.removed", { sessionID: "ses_timeline_stability", messageID: assistantID, partID: middleID }),
500,
)
await expect(page.locator(`[data-timeline-part-id="${middleID}"]`)).toHaveCount(0)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "middle-insert-remove", trace, stablePairPlan(regions, 1))
})
test("streams text through growth, canonical replacement, and completion", async ({ page }, testInfo) => {
const textID = "prt_text_reconcile"
const followingID = "prt_text_reconcile_following"
const assistant = assistantMessage([textPart(textID, "Starting"), textPart(followingID, "Following text row")], {
completed: false,
})
const timeline = await setupTimeline(page, { messages: [userMessage(), assistant], cpuRate: 4 })
const regions = defineVisualRegions({
text: { selector: `[data-timeline-part-id="${textID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
following: { selector: `[data-timeline-part-id="${followingID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(partDelta(textID, " streamed content"), 100)
await timeline.send(partDelta(textID, "\n\n- item one\n- item two\n- item three"), 180)
await timeline.send(partUpdated(textPart(textID, "Canonical replacement with a shorter final paragraph.")), 200)
await timeline.send(messageUpdated(completedAssistantInfo(assistant.info)), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"text-reconcile",
trace,
visualPlan(regions, [
{ type: "required", regions: ["text", "following"] },
{ type: "unique", regions: ["text", "following"] },
{ type: "stable", regions: ["text", "following"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 1, maxReversals: 2 },
{ type: "label-stability", regions: "all" },
{ type: "preserve-bottom-anchor" },
{ type: "flow", regions: ["text", "following"] },
]),
)
})
test("inserts a completed question between stable rows", async ({ page }, testInfo) => {
const firstID = "prt_question_01_first"
const questionID = "prt_question_02_hidden"
const lastID = "prt_question_03_last"
const input = { questions: [{ header: "Choice", question: "Keep stable?", options: [] }] }
const timeline = await setupTimeline(page, {
messages: [
userMessage(),
assistantMessage(
[
textPart(firstID, "Before question"),
toolPart(questionID, "question", "running", input),
textPart(lastID, "After question"),
],
{ completed: false },
),
],
cpuRate: 4,
})
await expect(page.locator(`[data-timeline-part-id="${questionID}"]`)).toHaveCount(0)
const regions = defineVisualRegions({
first: { selector: `[data-timeline-part-id="${firstID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
last: { selector: `[data-timeline-part-id="${lastID}"]`, closest: '[data-timeline-row="AssistantPart"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
partUpdated(toolPart(questionID, "question", "completed", input, { metadata: { answers: [["Yes"]] } })),
600,
)
await expect(page.locator(`[data-timeline-part-id="${questionID}"]`)).toBeVisible()
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(testInfo, "question-insert", trace, stablePairPlan(regions, 0))
})
test("replaces thinking with an assistant error without a blank turn", async ({ page }, testInfo) => {
const assistant = assistantMessage([], { completed: false })
const timeline = await setupTimeline(page, { messages: [userMessage(), assistant], cpuRate: 4 })
await timeline.send(status("busy"), 150)
await expect(page.locator('[data-timeline-row="Thinking"]')).toBeVisible()
const regions = defineVisualRegions({
thinking: { selector: '[data-timeline-row="Thinking"]' },
error: { selector: '[data-timeline-row="Error"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
messageUpdated({
...assistant.info,
error: { name: "APIError", data: { message: "Provider failed visibly", isRetryable: false } },
}),
500,
)
await expect(page.locator('[data-timeline-row="Thinking"]')).toHaveCount(0)
await expect(page.locator('[data-timeline-row="Error"]')).toContainText("Provider failed visibly")
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"thinking-error",
trace,
visualPlan(regions, [
{ type: "required", regions: ["thinking", "error"] },
{ type: "continuous-any", regions: ["thinking", "error"] },
{ type: "unique", regions: ["thinking", "error"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all" },
{ type: "label-stability", regions: "all" },
]),
)
})
test("updates retry attempts and long provider messages without remounting the retry row", async ({
page,
}, testInfo) => {
const timeline = await setupTimeline(page, {
messages: [userMessage(), assistantMessage([], { completed: false })],
cpuRate: 4,
})
await timeline.send(status("retry", 1), 120)
await expect(page.locator('[data-timeline-row="Retry"]')).toBeVisible()
const regions = defineVisualRegions({
retry: { selector: '[data-timeline-row="Retry"]' },
})
await startVisualProbe(page, regions)
await timeline.send(
event("session.status", {
sessionID: "ses_timeline_stability",
status: {
type: "retry",
attempt: 2,
message: "A very long provider retry message ".repeat(8),
next: Date.now() + 10_000,
},
}),
300,
)
await timeline.send(status("retry", 3), 300)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"retry-evolution",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["retry"] },
{ type: "unique", regions: ["retry"] },
{ type: "stable", regions: ["retry"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
],
{ perMarker: true },
),
)
})
test("reducer-hardening: removes a historical turn one message at a time without moving a visible lower anchor twice", async ({
page,
}, testInfo) => {
const removeUserID = "msg_0500_remove_user"
const removeAssistantID = "msg_0501_remove_assistant"
const anchorUserID = "msg_2000_anchor_user"
const timeline = await setupTimeline(page, {
messages: [
userMessage(undefined, { id: removeUserID, created: 1690000000000 }),
assistantMessage([textPart("prt_remove_text", "Removed historical content. ".repeat(15))], {
id: removeAssistantID,
parentID: removeUserID,
created: 1690000001000,
}),
userMessage(undefined, { id: anchorUserID, created: 1700000000000 }),
assistantMessage([textPart("prt_anchor_text", "Visible anchor response")], {
id: "msg_2001_anchor_assistant",
parentID: anchorUserID,
created: 1700000001000,
}),
],
cpuRate: 4,
})
const regions = defineVisualRegions({
anchor: { selector: `[data-timeline-row="UserMessage"][data-message-id="${anchorUserID}"]` },
})
await startVisualProbe(page, regions)
await timeline.send(
event("message.removed", { sessionID: "ses_timeline_stability", messageID: removeAssistantID }),
200,
)
await timeline.send(event("message.removed", { sessionID: "ses_timeline_stability", messageID: removeUserID }), 500)
const trace = await stopVisualProbe<keyof typeof regions>(page)
await reportVisualStability(
testInfo,
"historical-turn-remove",
trace,
visualPlan(
regions,
[
{ type: "required", regions: ["anchor"] },
{ type: "unique", regions: ["anchor"] },
{ type: "stable", regions: ["anchor"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals: 0 },
{ type: "label-stability", regions: "all" },
],
{ perMarker: true },
),
)
})
function stablePairPlan(
regions: Record<"first" | "last", { selector: string; closest?: string }>,
maxPositionReversals: number,
) {
return visualPlan(regions, [
{ type: "required", regions: ["first", "last"] },
{ type: "unique", regions: ["first", "last"] },
{ type: "stable", regions: ["first", "last"] },
{ type: "opacity", regions: "all" },
{ type: "continuity", regions: "all" },
{ type: "motion", regions: "all", maxPositionReversals },
{ type: "label-stability", regions: "all" },
])
}

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import { expect, test } from "bun:test"
import {
analyzeVisualStability,
analyzeVisualStabilityByMarker,
type VisualStabilityTrace,
} from "../../utils/visual-stability"
import { analyzeVisualObservations } from "../../utils/visual-stability/analyzer"
import { legacyVisualPlan, visualPlan, type VisualInvariant } from "../../utils/visual-stability/invariant"
import { defineVisualRegions, mapVisualRegions } from "../../utils/visual-stability/regions"
function trace(samples: VisualStabilityTrace["samples"]): VisualStabilityTrace {
return { markers: [], samples }
}
test("accepts continuous visible motion", () => {
expect(
analyzeVisualStability(
trace([
frame(0, region({ width: 80, bottom: 40 }), region({ top: 40, bottom: 60 })),
frame(16, region({ width: 75, bottom: 45 }), region({ top: 45, bottom: 65 })),
frame(32, region({ width: 70, bottom: 50 }), region({ top: 50, bottom: 70 })),
]),
{ flow: ["changing", "following"] },
),
).toEqual([])
})
test("reports repeated geometry reversals", () => {
const issues = analyzeVisualStability(
trace([
frame(0, region({ width: 80 })),
frame(16, region({ width: 60 })),
frame(32, region({ width: 78 })),
frame(48, region({ width: 62 })),
]),
)
expect(issues.some((issue) => issue.includes("changing width reversed 2 times"))).toBe(true)
})
test("reports visible blanking, label reversal, and overlap", () => {
const issues = analyzeVisualStability(
trace([
frame(0, region({ label: "Exploring", opacity: 1, bottom: 40 }), region({ top: 40, bottom: 60 })),
frame(16, region({ label: "Explored", opacity: 0.2, bottom: 50 }), region({ top: 49, bottom: 69 })),
frame(32, region({ label: "Exploring", opacity: 1, bottom: 50 }), region({ top: 50, bottom: 70 })),
]),
{ flow: ["changing", "following"] },
)
expect(issues.some((issue) => issue.includes("opacity fell to 0.2"))).toBe(true)
expect(issues.some((issue) => issue.includes("label reverted"))).toBe(true)
expect(issues.some((issue) => issue.includes("overlapped following by 1px"))).toBe(true)
})
test("reports duplicate regions and unexpected remounts", () => {
const issues = analyzeVisualStability(
trace([frame(0, region({ node: 1 })), frame(16, region({ node: 2, count: 2 })), frame(32, region({ node: 2 }))]),
{ stable: ["changing"], unique: ["changing"] },
)
expect(issues.some((issue) => issue.includes("changing appeared 2 times"))).toBe(true)
expect(issues.some((issue) => issue.includes("changing remounted"))).toBe(true)
})
test("reports bottom anchor loss but permits movement while scrolled away", () => {
const anchored = analyzeVisualStability(
trace([
{ at: 0, regions: { changing: region() }, viewport: viewport(0) },
{ at: 16, regions: { changing: region() }, viewport: viewport(24) },
]),
{ preserveBottomAnchor: true },
)
const away = analyzeVisualStability(
trace([
{ at: 0, regions: { changing: region() }, viewport: viewport(80) },
{ at: 16, regions: { changing: region() }, viewport: viewport(104) },
]),
{ preserveBottomAnchor: true },
)
expect(anchored.some((issue) => issue.includes("bottom anchor moved to 24px"))).toBe(true)
expect(away).toEqual([])
})
test("reports up down up movement while preserving a bottom anchor", () => {
const issues = analyzeVisualStability(
trace([
{ at: 0, regions: { changing: region({ top: 200, bottom: 240 }) }, viewport: viewport(0) },
{ at: 16, regions: { changing: region({ top: 180, bottom: 220 }) }, viewport: viewport(0) },
{ at: 32, regions: { changing: region({ top: 196, bottom: 236 }) }, viewport: viewport(0) },
{ at: 48, regions: { changing: region({ top: 176, bottom: 216 }) }, viewport: viewport(0) },
]),
{ preserveBottomAnchor: true, maxPositionReversals: 0 },
)
expect(issues.some((issue) => issue.includes("changing top reversed 2 times"))).toBe(true)
expect(issues.some((issue) => issue.includes("changing bottom reversed 2 times"))).toBe(true)
})
test("accepts monotonic upward movement while preserving a bottom anchor", () => {
expect(
analyzeVisualStability(
trace([
{ at: 0, regions: { changing: region({ top: 200, bottom: 240 }) }, viewport: viewport(0) },
{ at: 16, regions: { changing: region({ top: 190, bottom: 230 }) }, viewport: viewport(0) },
{ at: 32, regions: { changing: region({ top: 180, bottom: 220 }) }, viewport: viewport(0) },
]),
{ preserveBottomAnchor: true, maxPositionReversals: 0 },
),
).toEqual([])
})
test("ignores overlap entirely outside the clipped timeline viewport", () => {
expect(
analyzeVisualStability(
trace([
{
at: 0,
regions: {
changing: region({ top: -200, bottom: -100 }),
following: region({ top: -150, bottom: -50 }),
},
viewport: viewport(0),
},
]),
{ flow: ["changing", "following"] },
),
).toEqual([])
})
test("reports visible anchor movement while allowing virtual scrollbar movement", () => {
const issues = analyzeVisualStability(
trace([
{ at: 0, regions: { anchor: region({ top: 100, bottom: 120 }) }, viewport: { ...viewport(100), scrollTop: 40 } },
{ at: 16, regions: { anchor: region({ top: 100, bottom: 120 }) }, viewport: { ...viewport(120), scrollTop: 60 } },
]),
{ fixed: ["anchor"] },
)
expect(issues).toEqual([])
const moved = analyzeVisualStability(
trace([
{ at: 0, regions: { anchor: region({ top: 100, bottom: 120 }) }, viewport: viewport(100) },
{ at: 16, regions: { anchor: region({ top: 112, bottom: 132 }) }, viewport: viewport(100) },
]),
{ fixed: ["anchor"] },
)
expect(moved.some((issue) => issue.includes("anchor moved 12px in the viewport"))).toBe(true)
})
test("analyzes each marked event independently", () => {
const input: VisualStabilityTrace = {
markers: [
{ at: 10, label: "grow" },
{ at: 40, label: "shrink" },
],
samples: [
frame(0, region({ top: 100 })),
frame(16, region({ top: 90 })),
frame(32, region({ top: 80 })),
frame(48, region({ top: 90 })),
frame(64, region({ top: 100 })),
],
}
expect(analyzeVisualStability(input, { maxPositionReversals: 0 })).toContain("changing top reversed 1 times")
expect(
analyzeVisualStabilityByMarker(input, {
maxPositionReversals: 0,
motion: ["changing"],
aggregateMotion: false,
}),
).toEqual([])
})
test("reports cross-event motion reversals by default", () => {
const input: VisualStabilityTrace = {
markers: [
{ at: 10, label: "up" },
{ at: 40, label: "down" },
],
samples: [
frame(0, region({ top: 100 })),
frame(16, region({ top: 90 })),
frame(32, region({ top: 80 })),
frame(48, region({ top: 90 })),
frame(64, region({ top: 100 })),
],
}
expect(analyzeVisualStabilityByMarker(input, { maxPositionReversals: 0 })).toContain("changing top reversed 1 times")
})
test("reports regions rendered in the wrong flow order", () => {
const issues = analyzeVisualStability(
trace([frame(0, region({ top: 100, bottom: 120 }), region({ top: 60, bottom: 80 }))]),
{ flow: ["changing", "following"] },
)
expect(issues.some((issue) => issue.includes("changing rendered after following"))).toBe(true)
})
test("uses painted bounds instead of clipped layout overflow", () => {
expect(
analyzeVisualStability(
trace([
frame(
0,
region({ top: 100, bottom: 140, height: 40, layoutTop: 100, layoutBottom: 300 }),
region({ top: 140, bottom: 180 }),
),
]),
{ flow: ["changing", "following"] },
),
).toEqual([])
})
test("does not report disappearance when a present row moves outside the viewport", () => {
expect(
analyzeVisualStability(
trace([
frame(0, region({ visible: true })),
frame(16, region({ visible: false, inViewport: false, top: -100, bottom: -80 })),
frame(32, region({ visible: true })),
]),
),
).toEqual([])
})
test("reports an in-viewport transparent frame between visible frames", () => {
const issues = analyzeVisualStability(
trace([
frame(0, region()),
frame(16, region({ visible: false, opacity: 0, inViewport: true })),
frame(32, region()),
]),
)
expect(issues.some((issue) => issue.includes("blanked between visible frames"))).toBe(true)
})
test("reports an in-viewport display-none frame between visible frames", () => {
const issues = analyzeVisualStability(
trace([
frame(0, region()),
frame(16, region({ visible: false, width: 0, height: 0, inViewport: true, cssHidden: true })),
frame(32, region()),
]),
)
expect(issues.some((issue) => issue.includes("blanked between visible frames"))).toBe(true)
})
test("can limit motion analysis to unaffected regions", () => {
expect(
analyzeVisualStability(
trace([
frame(0, region({ height: 20 }), region()),
frame(16, region({ height: 40 }), region()),
frame(32, region({ height: 30 }), region()),
]),
{ motion: ["following"] },
),
).toEqual([])
})
test("reports a blank frame across replacement surfaces", () => {
const issues = analyzeVisualStability(
{
markers: [],
samples: [
{ at: 0, regions: { thinking: region(), error: region({ present: false, visible: false }) } },
{
at: 16,
regions: {
thinking: region({ present: false, visible: false }),
error: region({ present: false, visible: false }),
},
},
{ at: 32, regions: { thinking: region({ present: false, visible: false }), error: region() } },
],
},
{ continuousAny: [["thinking", "error"]] },
)
expect(issues.some((issue) => issue.includes("thinking | error blanked"))).toBe(true)
})
test("reports failure to acquire the bottom anchor", () => {
const issues = analyzeVisualStability(
trace([
{ at: 0, regions: { changing: region() }, viewport: viewport(600) },
{ at: 16, regions: { changing: region() }, viewport: viewport(120) },
]),
{ acquireBottomAnchor: true },
)
expect(issues.some((issue) => issue.includes("did not acquire bottom anchor"))).toBe(true)
})
test("reports a required region that never renders", () => {
const issues = analyzeVisualStability(
trace([
{
at: 0,
regions: { changing: region({ present: false, visible: false }) },
},
]),
{ required: ["changing"] },
)
expect(issues).toContain("changing never rendered")
})
test("preserves typed region names while mapping definitions", () => {
const regions = defineVisualRegions({
changing: { selector: "[data-changing]" },
following: { selector: "[data-following]", closest: "[data-row]" },
})
const selectors = mapVisualRegions(regions, (region) => region.selector)
expect(selectors).toEqual({ changing: "[data-changing]", following: "[data-following]" })
const name: keyof typeof selectors = "changing"
expect(name).toBe("changing")
})
test("evaluates the typed invariant algebra over explicit observations", () => {
const regions = defineVisualRegions({
changing: { selector: "[data-changing]" },
following: { selector: "[data-following]" },
})
const invariants = [
{ type: "required", regions: ["changing"] },
{ type: "flow", regions: ["changing", "following"] },
] satisfies VisualInvariant<keyof typeof regions>[]
// @ts-expect-error Plans reject names that are not in the region definition.
const invalid = { type: "required", regions: ["missing"] } satisfies VisualInvariant<keyof typeof regions>
const plan = visualPlan(regions, invariants, { perMarker: true })
expect(invalid.regions).toEqual(["missing"])
expect(plan.perMarker).toBe(true)
expect(analyzeVisualObservations([frame(0, region({ bottom: 50 }), region({ top: 49, bottom: 69 }))], plan)).toEqual([
"changing overlapped following by 1px at 0ms",
])
})
test("legacy plan adapter preserves analyzer messages and order", () => {
const input = trace([
frame(0, region({ label: "Exploring", opacity: 1, bottom: 40 }), region({ top: 40, bottom: 60 })),
frame(16, region({ label: "Explored", opacity: 0.2, bottom: 50 }), region({ top: 49, bottom: 69 })),
frame(32, region({ label: "Exploring", opacity: 1, bottom: 50 }), region({ top: 50, bottom: 70 })),
])
const options = { flow: ["changing", "following"], stable: ["changing"] }
expect(analyzeVisualObservations(input.samples, legacyVisualPlan(options))).toEqual(
analyzeVisualStability(input, options),
)
})
function frame(
at: number,
changing: VisualStabilityTrace["samples"][number]["regions"][string],
following?: VisualStabilityTrace["samples"][number]["regions"][string],
) {
return { at, regions: { changing, ...(following ? { following } : {}) } }
}
function region(input: Partial<VisualStabilityTrace["samples"][number]["regions"][string]> = {}) {
return {
present: true,
visible: true,
inViewport: true,
top: 0,
bottom: 20,
width: 100,
height: 20,
opacity: 1,
count: 1,
node: 1,
label: "",
text: "",
layoutTop: input.top ?? 0,
layoutBottom: input.bottom ?? 20,
...input,
}
}
function viewport(distanceFromBottom: number) {
return { top: 0, bottom: 400, scrollTop: 100, scrollHeight: 500, clientHeight: 400, distanceFromBottom }
}