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fix(mobile): handle message.part.delta for reasoning/text parts #102

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Merged
snhsish merged 1 commit into from
Sep 7, 2026
Merged

fix(mobile): handle message.part.delta for reasoning/text parts #102

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98 changes: 87 additions & 11 deletions apps/mobile/components/hooks/event-stream.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -300,12 +300,53 @@ export function useEventStream(url?: string, sessionId?: string, token?: string,

case "message.part.updated":
case "message.part.delta": {
const isDelta = event.type === "message.part.delta"
if (isDelta) {
const sessionID = props.sessionID as string | undefined
const messageID = (props.messageID as string | undefined) ?? (props.part as MessagePart | undefined)?.messageID
const partID = (props.partID as string | undefined) ?? (props.part as MessagePart | undefined)?.id
const field = (props.field as string | undefined) ?? "text"
const delta = props.delta as string | undefined
if (!messageID || !partID || sessionID !== currentSessionId) return
if (!delta) return

const existing = getOrCreatePending()
const msgIdx = existing.findIndex(m => m.id === messageID)
if (msgIdx < 0) {
existing.push({
id: messageID,
sessionID: currentSessionId,
role: "assistant",
time: { created: Date.now() },
agent: "build",
model: { providerID: "...", modelID: "..." },
parts: [{ id: partID, type: "text", text: delta } as Part],
} as unknown as Message)
scheduleFlush()
break
}

const msg = existing[msgIdx]
const parts = msg.parts ?? []
const partIdx = parts.findIndex(p => p.id === partID)
if (partIdx >= 0) {
const existingPart = parts[partIdx] as Record<string, unknown> & { type: string }
if (field === "text" && typeof (existingPart as { text?: unknown }).text === "string") {
const newParts = [...parts]
newParts[partIdx] = { ...existingPart, text: ((existingPart as unknown as { text: string }).text + delta) } as Part
existing[msgIdx] = { ...msg, parts: newParts } as Message
scheduleFlush()
}
} else {
existing[msgIdx] = { ...msg, parts: [...parts, { id: partID, type: "text", text: delta } as Part] } as Message
scheduleFlush()
}
break
}

const part = props.part as MessagePart | undefined
if (!part || !part.messageID || part.sessionID !== currentSessionId) return

const isDelta = event.type === "message.part.delta"
const delta = props.delta as string | undefined

const existing = getOrCreatePending()
let msgIdx = existing.findIndex(m => m.id === part.messageID)

Expand Down Expand Up @@ -341,19 +382,54 @@ export function useEventStream(url?: string, sessionId?: string, token?: string,
let newParts: Part[]
if (partIdx >= 0) {
newParts = [...parts]
const existingPart = newParts[partIdx]

if (isDelta && delta) {
if (effectivePart.type === "text" && existingPart.type === "text") {
newParts[partIdx] = { ...existingPart, text: existingPart.text + delta }
} else if (effectivePart.type === "reasoning" && existingPart.type === "reasoning") {
newParts[partIdx] = { ...existingPart, text: existingPart.text + delta }
const existingPart = newParts[partIdx] as Part & { text?: unknown }

if (
(effectivePart.type === "text" || effectivePart.type === "reasoning") &&
(existingPart.type === "text" || existingPart.type === "reasoning" || !existingPart.type) &&
typeof (effectivePart as { text?: unknown }).text === "string" &&
typeof existingPart.text === "string"
) {
const incomingText = (effectivePart as unknown as { text: string }).text
const currentText = existingPart.text as string
if (incomingText !== currentText) {
if (incomingText.length === 0 && currentText.length > 0) {
newParts[partIdx] = { ...(effectivePart as Part), text: currentText } as Part
} else if (incomingText.startsWith(currentText)) {
newParts[partIdx] = effectivePart as Part
} else if (currentText.startsWith(incomingText)) {
newParts[partIdx] = { ...(effectivePart as Part), text: currentText } as Part
} else if (incomingText.length >= currentText.length) {
newParts[partIdx] = effectivePart as Part
} else {
newParts[partIdx] = { ...(effectivePart as Part), text: currentText } as Part
}
} else {
newParts[partIdx] = effectivePart as Part
}
} else {
newParts[partIdx] = effectivePart as Part
}
} else {
newParts = [...parts, effectivePart as Part]
const placeholder = parts.find(
(p) => p.id === effectivePart.id && (p.type === "text" || (p as { type: string }).type !== effectivePart.type)
)
if (
placeholder &&
(effectivePart.type === "text" || effectivePart.type === "reasoning") &&
typeof (placeholder as { text?: unknown }).text === "string" &&
typeof (effectivePart as { text?: unknown }).text === "string"
) {
const placeholderText = (placeholder as unknown as { text: string }).text
const incomingText = (effectivePart as unknown as { text: string }).text
if (placeholderText.length > 0 && !incomingText.startsWith(placeholderText)) {
newParts = [...parts.filter((p) => p.id !== effectivePart.id), { ...(effectivePart as Part), text: incomingText + placeholderText } as Part]
} else {
newParts = [...parts, effectivePart as Part]
}
} else {
newParts = [...parts, effectivePart as Part]
}
}

existing[msgIdx] = { ...msg, parts: newParts } as Message
Expand Down
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