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fix(agent-proxy): events.list uses opaque page cursor, not after_id

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The Managed Agents events endpoint (`GET /v1/sessions/{id}/events`)
does NOT support filtering by event id. It returns an opaque
`next_page` cursor on each response and accepts it back via the
`page` query parameter; an `after_id=` filter returns 400 Bad
Request, which caused every segment resume to fail backfill (visible
as `{"type":"status","kind":"session_error","message":"Backfill
failed: events.list returned 400 Bad Request"}`).

Caught during testing of commit 8e44de5: resuming from a segment
boundary always returned 400 and the brief silently lost events from
the previous segment.

Changes:
- `listAllEvents` now paginates via `page` / `next_page` and pulls
  the full session history (limit=1000). The Anthropic API has no
  per-id filter, so the caller is responsible for skipping events
  already delivered.
- New `pastInitialId` flag at the top of the body loop: on resume,
  mute every event up to and including `initialLastEventId`
  (still adding them to `seenEventIds` so the live stream doesn't
  re-emit them), then start delivering. On a brand-new session the
  flag starts true and is a no-op.
- Safety fallback: if backfill completes without ever seeing
  `initialLastEventId` (stale cursor / truncated history), flip
  the flag to true so we don't get stuck muting forever — the live
  stream will start delivering whatever shows up next.

Co-Authored-By: alex <alex@semipublic.co>
This commit is contained in:
Devin AI
2026-05-13 13:08:54 +00:00
parent 8e44de5271
commit df3c8e7d1c
1 changed files with 44 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
netlify/edge-functions/agent-proxy.ts
+44 -19
View File
@@ -93,8 +93,7 @@ type AgentEvent = {
type EventsListPage = {
data?: AgentEvent[]
has_more?: boolean
last_id?: string
next_page?: string
}
type NewSessionPayload = {
@@ -221,17 +220,20 @@ async function* parseSse(
}
// Page through `GET /v1/sessions/{id}/events` to backfill anything
// we missed. Accepts an `after` id so we only fetch new events.
// we missed. The Managed Agents endpoint uses an opaque `page` cursor
// returned as `next_page` on each response; there is no `after_id`
// filter, so we always pull the full history and the caller is
// responsible for skipping events it has already handled (via
// `seenEventIds` and the resume-payload `lastEventId`).
async function* listAllEvents(
sessionId: string,
apiKey: string,
after: string | undefined,
signal?: AbortSignal,
): AsyncGenerator<AgentEvent> {
let cursor = after
let pageCursor: string | undefined
for (;;) {
const params = new URLSearchParams({ order: 'asc', limit: '100' })
if (cursor) params.set('after_id', cursor)
const params = new URLSearchParams({ order: 'asc', limit: '1000' })
if (pageCursor) params.set('page', pageCursor)
const res = await anthropicFetch(
`/v1/sessions/${sessionId}/events?${params.toString()}`,
apiKey,
@@ -245,10 +247,8 @@ async function* listAllEvents(
const page = (await res.json()) as EventsListPage
const items = page.data || []
for (const ev of items) yield ev
if (!page.has_more) break
const lastId = page.last_id ?? items[items.length - 1]?.id
if (!lastId) break
cursor = lastId
if (!page.next_page) break
pageCursor = page.next_page
}
}
@@ -419,6 +419,12 @@ Please follow your instructions to produce the funding outlook brief.`
async start(controller) {
let lastSendAt = Date.now()
let lastEventIdSeen = initialLastEventId
// For resumes we replay the full session history via
// `listAllEvents` but mute every event up to and including
// `initialLastEventId` (the user has already seen those). Once
// we've cleared that cursor (or on a brand-new session where it
// is undefined), we start actually delivering events.
let pastInitialId = !initialLastEventId
const writeJson = (obj: unknown) => {
try {
@@ -596,29 +602,40 @@ Please follow your instructions to produce the funding outlook brief.`
break
}
// Backfill anything we missed since `lastEventIdSeen`.
// Dedupes happen by event id; terminal events still flip
// `done` even if we've seen the id before.
// Backfill anything we missed. The events endpoint does
// NOT support `after_id`, so we always pull the full session
// history and skip everything up to and including
// `initialLastEventId` (the cursor handed to us by the
// previous segment via the resume payload). Within this
// segment, `seenEventIds` dedupes against the live stream.
try {
for await (const event of listAllEvents(
sessionId,
apiKey,
lastEventIdSeen,
segmentAbort.signal,
)) {
if (segmenting) break
if (event.id) {
if (!seenEventIds.has(event.id)) {
if (!pastInitialId) {
// Already delivered to the user in a previous
// segment — mark seen so the live stream doesn't
// re-emit it, but do NOT call handle().
seenEventIds.add(event.id)
lastEventIdSeen = event.id
if (event.id === initialLastEventId) {
pastInitialId = true
}
} else if (!seenEventIds.has(event.id)) {
seenEventIds.add(event.id)
lastEventIdSeen = event.id
handle(event)
} else {
// Already handled in a previous iteration — but
// keep the cursor moving forward.
// Already handled earlier in this segment — keep
// the cursor moving forward.
lastEventIdSeen = event.id
}
}
if (isTerminal(event)) {
if (isTerminal(event) && pastInitialId) {
done = true
break
}
@@ -634,6 +651,14 @@ Please follow your instructions to produce the funding outlook brief.`
}
}
// If the cursor handed to us by the previous segment didn't
// appear in the session's history (stale / corrupted /
// history truncated), don't get stuck muting events forever
// — start delivering whatever shows up next.
if (!pastInitialId) {
pastInitialId = true
}
if (done || segmenting) {
// Drain the live-stream body we opened above so we don't
// leak the connection.