feat(streams): rollover block log and atomic stream → session cutover by mattzcarey · Pull Request #2216 · cloudflare/agents

mattzcarey · 2026-09-04T12:16:24Z

What

The stream data and the final session message live in the same Durable Object storage, and the handoff between them is one transaction:

temporary stream blocks
        ↓
session message
        ↓
delete temporary blocks

Three changes make that cheap and crash-safe:

Rollover block log. cf_agents_stream_chunks (one row per append) becomes cf_agents_stream_blocks: an append grows the open block row with an UPDATE until it reaches 256 KB, then opens the next. Still one billed row per append, but a stream of thousands of chunks is a handful of rows, so deleting it is a handful of writes instead of thousands. Schema v2 folds existing chunk rows into blocks on startup.
Atomic cutover. writer.close({ commit, discard }) (and error(reason, { … })) settles the stream, runs the caller's synchronous writes and deletes the stream's rows in one transactionSync. Session.__DO_NOT_USE_WILL_BREAK__sync().upsert() is the matching synchronous message write; it returns a notify() to dispatch the change feed after the commit.
Hosts persist inside the cutover, and the sweep is gone. When the producer finishes, ResumableStream.finish() leaves the row live; the host's final persist then runs cutover(): message write, settlement and row deletion in one transaction (persistMessages { _cutover } in AIChatAgent, _persistAssistantMessageWithCutover in Think). A turn with nothing to persist is settled by finalizePending(). start() reclaims whatever a crash left behind: finished streams immediately, abandoned in-flight rows after an hour without a chunk. No cleanup alarm is armed any more; cleanupStreamBuffers and STREAM_CLEANUP_DELAY_SECONDS are removed from agents/chat, and the hosts' _cleanupStreamBuffers callback stays as a no-op so alarms persisted by earlier versions still resolve. Agent-tool child turns cut over without discarding (the parent tails their stored chunks after completion); those rows go at the next start.

Why

Measured on a real DO (src/tests/streams/sqlite-strategies-bench.test.ts, kept in the PR): a 400-chunk chat turn packed 10 per write.

Log shape	Write phase	Cutover / cleanup	Lifetime rows
Immutable packed rows (before)	42	42 deleted by a sweep later	84
Reusable generational slots	42	2	44
Mutable rollover blocks	42	3	45

Rollover was chosen over slots because it has no shared state: every row belongs to one stream, is addressed by its primary key, and dies with the stream. Slots need a pool that never shrinks (5.6 MB left behind at 20k chunks), an index that doubles the per-flush write, and a free list rebuilt on every restart.

Crash matrix (`ctx.abort()` at each point; in-repo as `src/e2e-tests/stream-cutover-crash.test.ts` against `wrangler dev`, and reproduced on a deployed DO)

Crash point	Restart finds
Before a block append commits	exact prefix (10 chunks), the uncommitted append absent
Immediately after it commits	exact prefix (11 chunks)
During rollover, before commit	block 0 only, cursor 1
During rollover, after commit	blocks 0 and 1, cursor 2, contiguous
After session persist, before discard, with I/O between (the non-atomic path hosts use today)	message present once, stream `completed` with its exact prefix; the next `start()` reclaims it
After session persist, before discard, no I/O between	stream live with its prefix, no message (the runtime commits at I/O boundaries, so both rolled back together)
Inside the atomic cutover's `commit`	stream live with its prefix, no message
Right after the atomic cutover	message present once, stream gone

Never neither, never both.

Tests

src/tests/streams/cutover.test.ts: cutover commits message + settle + discard together; a throwing commit rolls the settle back and the stream stays live; blocks roll over and replay across the boundary; delete() removes every block.
Write-accounting probe pins block open, block append and block delete at 1 row each; the storage-ops bench pins the hot path unchanged and the inline reclaim at 2 rows per turn.
agents streams/sessions/chat suites (107), agents chat unit project (545), ai-chat workers suite (637), Think stream/session/recovery suites (224), the ai-chat e2e stream-buffer test (a turn leaves no rows and arms no alarm) all green. Test workers that seeded the old chunk table now seed blocks; getStreamChunkRowCount reports appended segments from the block tail; the alarm-driven cleanup tests became reclaim tests.
Real-R2 spike and the R2 backend (feat(streams): R2 chunk log — segment write-ahead log behind new Streams({ r2 }) #2215) are superseded by this PR.

…ge cutover Compares immutable packed rows, reusable generational slots and mutable rollover blocks on billed rows, write time, page growth, replay, and the cursor a restarted isolate recovers, with an atomic transactionSync cutover to the message row. Numbers logged, invariants asserted.

- The Streams chunk log is mutable rollover blocks: an append grows the open block row (UPDATE) until 256 KB, then opens the next. Same one billed row per append; a stream of thousands of chunks is a handful of rows to delete. Schema v2 folds existing cf_agents_stream_chunks rows into blocks. - writer.close({ commit, discard }) / error(reason, { ... }) settle, run the caller's synchronous writes and delete the stream's rows in one SQLite transaction. Session.__DO_NOT_USE_WILL_BREAK__sync().upsert() is the matching synchronous message write. - ResumableStream.complete(id, { persist }) exposes the cutover; discardCompleted() drops a completed stream's rows once its message is persisted; start() reclaims completed streams a crash left behind. - AIChatAgent and Think discard right after persisting (agent-tool child turns excepted: the parent tails their stored chunks), so the retention sweep no longer finds completed streams.

changeset-bot · 2026-09-04T12:16:29Z

🦋 Changeset detected

Latest commit: 42d73a0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
agents	Minor
@cloudflare/ai-chat	Minor
@cloudflare/think	Minor
@cloudflare/agent-think	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

agent-think · 2026-09-04T12:18:37Z

🔴 agents import sizes

Measured 267 runtime imports as minified bundles. The primary size is gzip; raw minified size is included for diagnosis. An existing import growing by more than 10% is marked red. This report is informational.

Red	Yellow	Green	Unchanged	New	Removed
3	34	29	199	0	2

Compared ec93caf6 with 73eca75b. Open workflow run.

Changed imports (68)

Status	Import	Base gzip	Head gzip	Delta
🔴	`agents/streams#Streams`	3.4 KiB	4.1 KiB	+797 B (+23.2%)
🔴	`agents/chat#createChatStreams`	5.5 KiB	6.3 KiB	+781 B (+13.85%)
🔴	`agents/streams#DEFAULT_MAX_CHUNK_BYTES`	83 B	94 B	+11 B (+13.25%)
🟡	`agents/streams#StreamClosedError`	161 B	175 B	+14 B (+8.7%)
🟡	`agents/streams#StreamSerializationError`	158 B	171 B	+13 B (+8.23%)
🟡	`agents/streams#StreamNotFoundError`	201 B	215 B	+14 B (+6.97%)
🟡	`agents/sessions#Session`	1.9 KiB	2.0 KiB	+126 B (+6.53%)
🟡	`agents/streams#sseResponse`	843 B	855 B	+12 B (+1.42%)
🟡	`agents/sessions#Sessions`	8.8 KiB	9.0 KiB	+122 B (+1.35%)
🟡	`agents/chat#ResumableStream`	4.6 KiB	4.6 KiB	+55 B (+1.18%)
🟡	`agents/chat#truncateOlderMessages`	3.2 KiB	3.2 KiB	+3 B (+0.09%)
🟡	`agents/chat#toolPartHasSettledResult`	2.3 KiB	2.3 KiB	+2 B (+0.08%)
🟡	`agents/chat#STREAM_RESUME_NONE_REASONS`	2.3 KiB	2.3 KiB	+2 B (+0.08%)
🟡	`agents/chat#awaitWithDeadline`	2.4 KiB	2.4 KiB	+2 B (+0.08%)
🟡	`agents/chat#listActiveChatRecoveryIncidents`	2.4 KiB	2.4 KiB	+2 B (+0.08%)
🟡	`agents/chat#classifyAgentToolChildRecovery`	2.4 KiB	2.4 KiB	+2 B (+0.08%)
🟡	`agents/chat#sanitizeMessage`	2.5 KiB	2.5 KiB	+2 B (+0.08%)
🟡	`agents/chat#StreamAccumulator`	2.9 KiB	2.9 KiB	+2 B (+0.07%)
🟡	`agents/chat#persistReconstructedOrphan`	3.1 KiB	3.1 KiB	+2 B (+0.06%)
🟡	`agents/chat#broadcastTransition`	3.1 KiB	3.2 KiB	+2 B (+0.06%)
🟡	`agents/chat#enforceRowSizeLimit`	3.5 KiB	3.5 KiB	+2 B (+0.06%)
🟡	`agents/chat#CHAT_RECOVERY_TASK_NAME`	2.3 KiB	2.3 KiB	+1 B (+0.04%)
🟡	`agents/chat#TIMED_OUT`	2.3 KiB	2.3 KiB	+1 B (+0.04%)
🟡	`agents/chat#clientResolvableToolNames`	2.3 KiB	2.3 KiB	+1 B (+0.04%)
🟡	`agents/chat#createAgentToolEventState`	2.3 KiB	2.3 KiB	+1 B (+0.04%)
🟡	`agents/chat#applyToolUpdate`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#pausedExecutionUpdate`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#toolResultUpdate`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#partAwaitsClientInteraction`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#MessageType`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#sweepStaleChatRecoveryIncidents`	2.4 KiB	2.4 KiB	+1 B (+0.04%)
🟡	`agents/chat#setChatRecovering`	2.5 KiB	2.5 KiB	+1 B (+0.04%)
🟡	`agents/chat#parseProtocolMessage`	2.5 KiB	2.5 KiB	+1 B (+0.04%)
🟡	`agents/chat#AbortRegistry`	2.5 KiB	2.5 KiB	+1 B (+0.04%)
🟡	`agents/chat#TurnQueue`	2.6 KiB	2.6 KiB	+1 B (+0.04%)
🟡	`agents/chat#SubmitConcurrencyController`	2.9 KiB	2.9 KiB	+1 B (+0.03%)
🟡	`agents/chat#createToolsFromClientSchemas`	114.3 KiB	114.3 KiB	+1 B (+0%)
🟢	`agents/chat#CHAT_RECOVERY_STABLE_RETRY_DELAY_SECONDS`	2.3 KiB	2.3 KiB	-2 B (-0.08%)
🟢	`agents/chat#CHAT_LAST_TERMINAL_KEY`	2.3 KiB	2.3 KiB	-2 B (-0.08%)
🟢	`agents/chat#CHAT_RECOVERY_INCIDENT_KEY_PREFIX`	2.3 KiB	2.3 KiB	-2 B (-0.08%)
🟢	`agents/chat#repairInterruptedToolParts`	2.6 KiB	2.6 KiB	-2 B (-0.07%)
🟢	`agents/chat#ContinuationState`	2.7 KiB	2.7 KiB	-2 B (-0.07%)
🟢	`agents/chat#dispatchChatRecoveryToHandoff`	3.0 KiB	3.0 KiB	-2 B (-0.06%)
🟢	`agents/chat#CHAT_RECOVERING_FLAG_TTL_MS`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#CHAT_RECOVERY_INCIDENT_TTL_MS`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#applyChunkToParts`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#AutoContinuationController`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#CHAT_MESSAGE_TYPES`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_ATTEMPTS`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_OOM_RETRIES`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#KV_DELETE_MAX_KEYS`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_WORK`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_STABLE_TIMEOUT_MS`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#CHAT_RECOVERING_KEY`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#CHAT_RECOVERY_PROGRESS_KEY`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#wrapChatFiberSnapshot`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#pendingChatTerminal`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#clearChatTerminal`	2.3 KiB	2.3 KiB	-1 B (-0.04%)
🟢	`agents/chat#recordChatTerminal`	2.4 KiB	2.4 KiB	-1 B (-0.04%)
🟢	`agents/chat#ChatStreamStalledError`	2.4 KiB	2.4 KiB	-1 B (-0.04%)
🟢	`agents/chat#shouldCreditStreamProgress`	2.4 KiB	2.4 KiB	-1 B (-0.04%)
🟢	`agents/chat#sendIfOpen`	2.4 KiB	2.4 KiB	-1 B (-0.04%)
🟢	`agents/chat#resolveToolMergeId`	2.4 KiB	2.4 KiB	-1 B (-0.04%)
🟢	`agents/chat#PreStreamTurns`	2.6 KiB	2.6 KiB	-1 B (-0.04%)
🟢	`agents/chat#isPlatformFailure`	2.6 KiB	2.6 KiB	-1 B (-0.04%)
🟢	`agents/chat#ResumeHandshake`	3.0 KiB	3.0 KiB	-1 B (-0.03%)
🟢	`agents/chat#cleanupStreamBuffers`	2.3 KiB	—	—
🟢	`agents/chat#STREAM_CLEANUP_DELAY_SECONDS`	2.3 KiB	—	—

All 265 current runtime imports

Status	Import	Gzip	Raw minified
⚪	`agents#__DO_NOT_USE_WILL_BREAK__agentContext`	258.6 KiB	1130.0 KiB
⚪	`agents#__DO_NOT_USE_WILL_BREAK__withInvocationScope`	258.6 KiB	1130.0 KiB
⚪	`agents#Agent`	258.6 KiB	1130.0 KiB
⚪	`agents#AGENT_TOOL_MILESTONE_PART`	258.6 KiB	1130.0 KiB
⚪	`agents#AGENT_TOOL_PROGRESS_PART`	258.6 KiB	1130.0 KiB
⚪	`agents#buildAgentPath`	259.1 KiB	1132.3 KiB
⚪	`agents#buildAgentUrl`	259.3 KiB	1132.7 KiB
⚪	`agents#callable`	258.6 KiB	1130.1 KiB
⚪	`agents#camelCaseToKebabCase`	258.6 KiB	1130.0 KiB
⚪	`agents#createHeaderBasedEmailResolver`	258.8 KiB	1130.4 KiB
⚪	`agents#DEFAULT_AGENT_STATIC_OPTIONS`	258.6 KiB	1130.0 KiB
⚪	`agents#DurableObjectOAuthClientProvider`	258.6 KiB	1130.0 KiB
⚪	`agents#getAgentByName`	258.6 KiB	1130.0 KiB
⚪	`agents#getCurrentAgent`	258.6 KiB	1130.0 KiB
⚪	`agents#getSubAgentByName`	258.9 KiB	1130.7 KiB
⚪	`agents#isDurableObjectCodeUpdateReset`	258.6 KiB	1130.0 KiB
⚪	`agents#isDurableObjectMemoryLimitReset`	258.6 KiB	1130.0 KiB
⚪	`agents#isDurableObjectStorageReset`	258.6 KiB	1130.1 KiB
⚪	`agents#isPlatformTransientError`	258.6 KiB	1130.0 KiB
⚪	`agents#MCP_SERVER_ID_MAX_LENGTH`	258.6 KiB	1130.0 KiB
⚪	`agents#MessageType`	258.8 KiB	1130.3 KiB
⚪	`agents#normalizeServerId`	258.6 KiB	1130.0 KiB
⚪	`agents#parseSubAgentPath`	258.6 KiB	1130.0 KiB
⚪	`agents#routeAgentEmail`	258.9 KiB	1130.7 KiB
⚪	`agents#routeAgentRequest`	259.2 KiB	1131.9 KiB
⚪	`agents#routeSubAgentRequest`	258.8 KiB	1130.6 KiB
⚪	`agents#SqlError`	258.6 KiB	1130.0 KiB
⚪	`agents#StreamingResponse`	258.6 KiB	1130.0 KiB
⚪	`agents#SUB_PREFIX`	258.6 KiB	1130.0 KiB
⚪	`agents#unstable_callable`	258.7 KiB	1130.2 KiB
⚪	`agents/agent-tools#agentTool`	112.5 KiB	538.2 KiB
⚪	`agents/browser#BrowserConnector`	50.5 KiB	176.6 KiB
⚪	`agents/browser#browserContent`	36.3 KiB	127.4 KiB
⚪	`agents/browser#browserExtract`	36.3 KiB	127.4 KiB
⚪	`agents/browser#browserLinks`	36.3 KiB	127.4 KiB
⚪	`agents/browser#browserMarkdown`	36.3 KiB	127.4 KiB
⚪	`agents/browser#browserPdf`	36.3 KiB	127.3 KiB
⚪	`agents/browser#BrowserRenderingError`	36.0 KiB	126.7 KiB
⚪	`agents/browser#browserScrape`	36.3 KiB	127.4 KiB
⚪	`agents/browser#browserScreenshot`	36.3 KiB	127.3 KiB
⚪	`agents/browser#browserSnapshot`	36.3 KiB	127.4 KiB
⚪	`agents/browser#CdpSession`	37.2 KiB	129.8 KiB
⚪	`agents/browser#CodemodeRuntime`	39.6 KiB	139.0 KiB
⚪	`agents/browser#connectBrowser`	37.8 KiB	131.4 KiB
⚪	`agents/browser#connectBrowserSession`	37.5 KiB	130.4 KiB
⚪	`agents/browser#connectUrl`	37.6 KiB	130.5 KiB
⚪	`agents/browser#createBrowserSession`	36.3 KiB	127.5 KiB
⚪	`agents/browser#DEFAULT_EXEC_SWEEP_IDLE_MS`	36.0 KiB	126.6 KiB
⚪	`agents/browser#DEFAULT_SWEEP_IDLE_MS`	36.0 KiB	126.6 KiB
⚪	`agents/browser#deleteBrowserSession`	36.1 KiB	126.9 KiB
⚪	`agents/browser#DurableBrowserSessionStore`	36.4 KiB	127.6 KiB
⚪	`agents/browser#getBrowserRecording`	36.2 KiB	127.1 KiB
⚪	`agents/browser#listBrowserTargets`	36.1 KiB	126.9 KiB
⚪	`agents/browser#loadCdpSpec`	36.6 KiB	128.3 KiB
⚪	`agents/browser#runQuickAction`	36.0 KiB	126.6 KiB
⚪	`agents/browser/ai#createBrowserRuntime`	146.0 KiB	630.3 KiB
⚪	`agents/browser/ai#createBrowserTools`	146.0 KiB	630.3 KiB
⚪	`agents/browser/ai#createQuickActionTools`	122.5 KiB	554.3 KiB
⚪	`agents/browser/tanstack-ai#createBrowserTools`	161.7 KiB	699.2 KiB
🟡	`agents/chat#AbortRegistry`	2.5 KiB	8.9 KiB
⚪	`agents/chat#AGENT_TOOL_STREAM_PROGRESS_BUMP_THROTTLE_MS`	2.3 KiB	8.2 KiB
⚪	`agents/chat#AgentToolProgressEmitter`	2.7 KiB	9.5 KiB
⚪	`agents/chat#AgentToolStreamProgressThrottle`	2.4 KiB	8.3 KiB
⚪	`agents/chat#aiSdkRecoveryCodec`	2.3 KiB	8.2 KiB
⚪	`agents/chat#applyAgentToolEvent`	3.2 KiB	11.0 KiB
🟢	`agents/chat#applyChunkToParts`	2.3 KiB	8.2 KiB
🟡	`agents/chat#applyToolUpdate`	2.4 KiB	8.4 KiB
🟢	`agents/chat#AutoContinuationController`	2.3 KiB	8.2 KiB
🟡	`agents/chat#awaitWithDeadline`	2.4 KiB	8.4 KiB
🟡	`agents/chat#broadcastTransition`	3.2 KiB	11.4 KiB
⚪	`agents/chat#buildChatRecoveringFrame`	2.4 KiB	8.4 KiB
⚪	`agents/chat#buildInClauseStrings`	2.4 KiB	8.4 KiB
⚪	`agents/chat#bumpChatRecoveryProgress`	2.4 KiB	8.3 KiB
⚪	`agents/chat#byteLength`	2.5 KiB	8.4 KiB
🟢	`agents/chat#CHAT_LAST_TERMINAL_KEY`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_MESSAGE_TYPES`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERING_FLAG_TTL_MS`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERING_KEY`	2.3 KiB	8.2 KiB
⚪	`agents/chat#CHAT_RECOVERY_ALARM_DEBOUNCE_MS`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERY_INCIDENT_KEY_PREFIX`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERY_INCIDENT_TTL_MS`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERY_PROGRESS_KEY`	2.3 KiB	8.2 KiB
🟢	`agents/chat#CHAT_RECOVERY_STABLE_RETRY_DELAY_SECONDS`	2.3 KiB	8.2 KiB
🟡	`agents/chat#CHAT_RECOVERY_TASK_NAME`	2.3 KiB	8.2 KiB
⚪	`agents/chat#CHAT_STREAM_PROGRESS_CREDIT_THROTTLE_MS`	2.3 KiB	8.2 KiB
⚪	`agents/chat#ChatRecoveryEngine`	4.4 KiB	15.3 KiB
⚪	`agents/chat#chatRecoveryTaskRunOptions`	2.4 KiB	8.6 KiB
🟢	`agents/chat#ChatStreamStalledError`	2.4 KiB	8.3 KiB
🟡	`agents/chat#classifyAgentToolChildRecovery`	2.4 KiB	8.5 KiB
🟢	`agents/chat#clearChatTerminal`	2.3 KiB	8.3 KiB
🟡	`agents/chat#clientResolvableToolNames`	2.3 KiB	8.3 KiB
🟢	`agents/chat#ContinuationState`	2.7 KiB	9.8 KiB
🟡	`agents/chat#createAgentToolEventState`	2.3 KiB	8.3 KiB
⚪	`agents/chat#createChatFiberSnapshot`	2.5 KiB	8.6 KiB
⚪	`agents/chat#createChatRecoveryTaskDefinition`	2.6 KiB	9.0 KiB
🔴	`agents/chat#createChatStreams`	6.3 KiB	21.7 KiB
⚪	`agents/chat#createChatTurnTaskDefinition`	2.7 KiB	8.9 KiB
🟡	`agents/chat#createToolsFromClientSchemas`	114.3 KiB	545.4 KiB
⚪	`agents/chat#crossMessageToolResultUpdate`	2.4 KiB	8.6 KiB
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_ATTEMPTS`	2.3 KiB	8.2 KiB
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_OOM_RETRIES`	2.3 KiB	8.2 KiB
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_MAX_WORK`	2.3 KiB	8.2 KiB
⚪	`agents/chat#DEFAULT_CHAT_RECOVERY_NO_PROGRESS_TIMEOUT_MS`	2.3 KiB	8.2 KiB
🟢	`agents/chat#DEFAULT_CHAT_RECOVERY_STABLE_TIMEOUT_MS`	2.3 KiB	8.2 KiB
⚪	`agents/chat#DEFAULT_CHAT_RECOVERY_TERMINAL_MESSAGE`	2.4 KiB	8.3 KiB
🟢	`agents/chat#dispatchChatRecoveryToHandoff`	3.0 KiB	9.9 KiB
⚪	`agents/chat#drainInteractionApplies`	2.3 KiB	8.3 KiB
🟡	`agents/chat#enforceRowSizeLimit`	3.5 KiB	11.2 KiB
⚪	`agents/chat#hasIncompleteToolBatch`	2.4 KiB	8.6 KiB
⚪	`agents/chat#interceptAgentToolBroadcast`	2.5 KiB	8.7 KiB
🟢	`agents/chat#isPlatformFailure`	2.6 KiB	8.9 KiB
⚪	`agents/chat#isReplayChunk`	2.4 KiB	8.7 KiB
⚪	`agents/chat#iterateWithStallWatchdog`	2.6 KiB	8.8 KiB
🟢	`agents/chat#KV_DELETE_MAX_KEYS`	2.3 KiB	8.2 KiB
🟡	`agents/chat#listActiveChatRecoveryIncidents`	2.4 KiB	8.4 KiB
⚪	`agents/chat#MAX_BOUND_PARAMS`	2.3 KiB	8.2 KiB
🟡	`agents/chat#MessageType`	2.4 KiB	9.0 KiB
⚪	`agents/chat#normalizeToolInput`	2.3 KiB	8.2 KiB
🟡	`agents/chat#parseProtocolMessage`	2.5 KiB	9.0 KiB
🟡	`agents/chat#partAwaitsClientInteraction`	2.4 KiB	8.6 KiB
🟡	`agents/chat#pausedExecutionUpdate`	2.4 KiB	8.4 KiB
🟢	`agents/chat#pendingChatTerminal`	2.3 KiB	8.3 KiB
🟡	`agents/chat#persistReconstructedOrphan`	3.1 KiB	11.0 KiB
🟢	`agents/chat#PreStreamTurns`	2.6 KiB	9.3 KiB
⚪	`agents/chat#readChatRecoveryProgress`	2.3 KiB	8.3 KiB
⚪	`agents/chat#reconcileMessages`	2.8 KiB	9.6 KiB
⚪	`agents/chat#reconcileOrphanPartial`	2.4 KiB	8.5 KiB
🟢	`agents/chat#recordChatTerminal`	2.4 KiB	8.3 KiB
🟢	`agents/chat#repairInterruptedToolParts`	2.6 KiB	9.1 KiB
⚪	`agents/chat#resolveChatRecoveryConfig`	2.6 KiB	8.9 KiB
🟢	`agents/chat#resolveToolMergeId`	2.4 KiB	8.5 KiB
🟡	`agents/chat#ResumableStream`	4.6 KiB	15.6 KiB
🟢	`agents/chat#ResumeHandshake`	3.0 KiB	10.4 KiB
⚪	`agents/chat#ROW_MAX_BYTES`	2.3 KiB	8.2 KiB
⚪	`agents/chat#runChatRecoveryExhaustion`	2.6 KiB	8.9 KiB
🟡	`agents/chat#sanitizeMessage`	2.5 KiB	8.8 KiB
🟢	`agents/chat#sendIfOpen`	2.4 KiB	8.4 KiB
🟡	`agents/chat#setChatRecovering`	2.5 KiB	8.5 KiB
🟢	`agents/chat#shouldCreditStreamProgress`	2.4 KiB	8.3 KiB
🟡	`agents/chat#STREAM_RESUME_NONE_REASONS`	2.3 KiB	8.2 KiB
🟡	`agents/chat#StreamAccumulator`	2.9 KiB	10.7 KiB
⚪	`agents/chat#StreamProgressCreditThrottle`	2.4 KiB	8.3 KiB
🟡	`agents/chat#SubmitConcurrencyController`	2.9 KiB	10.3 KiB
🟡	`agents/chat#sweepStaleChatRecoveryIncidents`	2.4 KiB	8.5 KiB
⚪	`agents/chat#TextSegmentJoiner`	2.7 KiB	9.2 KiB
🟡	`agents/chat#TIMED_OUT`	2.3 KiB	8.2 KiB
⚪	`agents/chat#toolApprovalUpdate`	2.4 KiB	8.5 KiB
🟡	`agents/chat#toolPartHasSettledResult`	2.3 KiB	8.4 KiB
🟡	`agents/chat#toolResultUpdate`	2.4 KiB	8.5 KiB
🟡	`agents/chat#truncateOlderMessages`	3.2 KiB	10.4 KiB
🟡	`agents/chat#TurnQueue`	2.6 KiB	9.2 KiB
⚪	`agents/chat#unwrapChatFiberSnapshot`	2.4 KiB	8.5 KiB
🟢	`agents/chat#wrapChatFiberSnapshot`	2.3 KiB	8.2 KiB
⚪	`agents/chat-sdk#ChatSdkStateAdapter`	261.0 KiB	1141.6 KiB
⚪	`agents/chat-sdk#ChatSdkStateAgent`	260.4 KiB	1139.1 KiB
⚪	`agents/chat-sdk#createChatSdkState`	261.0 KiB	1141.6 KiB
⚪	`agents/chat-sdk#defaultKeyShard`	258.8 KiB	1130.2 KiB
⚪	`agents/chat-sdk#defaultThreadShard`	258.7 KiB	1130.1 KiB
⚪	`agents/chat/react#detectToolsRequiringConfirmation`	3.3 KiB	8.3 KiB
⚪	`agents/chat/react#extractClientToolSchemas`	3.2 KiB	8.3 KiB
⚪	`agents/chat/react#getAgentMessages`	3.4 KiB	8.6 KiB
⚪	`agents/chat/react#getToolApproval`	3.1 KiB	8.0 KiB
⚪	`agents/chat/react#getToolCallId`	3.1 KiB	8.0 KiB
⚪	`agents/chat/react#getToolInput`	3.1 KiB	8.0 KiB
⚪	`agents/chat/react#getToolOutput`	3.1 KiB	8.0 KiB
⚪	`agents/chat/react#getToolPartState`	3.2 KiB	8.2 KiB
⚪	`agents/chat/react#useAgentChat`	132.9 KiB	609.7 KiB
⚪	`agents/chat/react#WebSocketChatTransport`	5.7 KiB	17.1 KiB
⚪	`agents/chat/transport#WebSocketChatTransport`	2.8 KiB	9.2 KiB
⚪	`agents/client#AgentClient`	5.7 KiB	16.6 KiB
⚪	`agents/client#AgentConnectionError`	582 B	993 B
⚪	`agents/client#agentFetch`	4.2 KiB	12.3 KiB
⚪	`agents/client#createStubProxy`	638 B	1.0 KiB
⚪	`agents/client#DEFAULT_CALL_TIMEOUT_MS`	473 B	770 B
⚪	`agents/client#isTerminalCloseEvent`	509 B	822 B
⚪	`agents/context#AgentContextProvider`	412 B	792 B
⚪	`agents/context#AgentSearchProvider`	640 B	1.3 KiB
⚪	`agents/context#ContextBlocks`	87.4 KiB	429.7 KiB
⚪	`agents/email#createAddressBasedEmailResolver`	193 B	227 B
⚪	`agents/email#createCatchAllEmailResolver`	110 B	97 B
⚪	`agents/email#createHeaderBasedEmailResolver`	334 B	492 B
⚪	`agents/email#createSecureReplyEmailResolver`	718 B	1.3 KiB
⚪	`agents/email#DEFAULT_MAX_AGE_SECONDS`	56 B	39 B
⚪	`agents/email#isAutoReplyEmail`	201 B	249 B
⚪	`agents/email#signAgentHeaders`	424 B	812 B
⚪	`agents/experimental/webmcp#registerWebMcp`	85.2 KiB	295.8 KiB
⚪	`agents/lifecycle#getCurrentAgent`	376 B	798 B
⚪	`agents/lifecycle#Lifecycle`	8.3 KiB	25.8 KiB
⚪	`agents/lifecycle#LifecycleCapability`	484 B	975 B
⚪	`agents/mcp#createLegacyMcpHandler`	375.9 KiB	1572.2 KiB
⚪	`agents/mcp#createMcpHandler`	388.2 KiB	1617.4 KiB
⚪	`agents/mcp#DurableObjectEventStore`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#ElicitRequestSchema`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#experimental_createMcpHandler`	376.1 KiB	1572.5 KiB
⚪	`agents/mcp#getMcpAuthContext`	342.5 KiB	1430.8 KiB
⚪	`agents/mcp#MCP_SERVER_ID_MAX_LENGTH`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#McpAgent`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#normalizeServerId`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#RPC_DO_PREFIX`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#RPCClientTransport`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#RPCServerTransport`	342.5 KiB	1430.7 KiB
⚪	`agents/mcp#SSEEdgeClientTransport`	342.6 KiB	1431.0 KiB
⚪	`agents/mcp#StreamableHTTPEdgeClientTransport`	342.6 KiB	1431.0 KiB
⚪	`agents/mcp#WorkerTransport`	345.8 KiB	1447.6 KiB
⚪	`agents/mcp/client#getNamespacedData`	62.9 KiB	240.0 KiB
⚪	`agents/mcp/client#MCP_SERVER_ID_MAX_LENGTH`	62.9 KiB	239.9 KiB
⚪	`agents/mcp/client#MCPClientManager`	158.6 KiB	702.6 KiB
⚪	`agents/mcp/client#normalizeServerId`	63.0 KiB	240.2 KiB
⚪	`agents/mcp/do-oauth-client-provider#DurableObjectOAuthClientProvider`	2.1 KiB	6.6 KiB
⚪	`agents/mcp/server#createMcpHandler`	80.5 KiB	307.2 KiB
⚪	`agents/mcp/server#getMcpAuthContext`	64.0 KiB	245.5 KiB
⚪	`agents/observability#channels`	259 B	549 B
⚪	`agents/observability#genericObservability`	470 B	1.2 KiB
⚪	`agents/observability#subscribe`	324 B	668 B
⚪	`agents/observability/ai#wrapAISDK`	8.8 KiB	30.5 KiB
⚪	`agents/react#_testUtils`	3.8 KiB	9.5 KiB
⚪	`agents/react#useAgent`	10.8 KiB	31.1 KiB
⚪	`agents/react#useAgentToolEvents`	5.6 KiB	16.8 KiB
⚪	`agents/routing#getAgentByName`	795 B	1.7 KiB
⚪	`agents/routing#routeAgentRequest`	1.6 KiB	3.6 KiB
⚪	`agents/routing#RoutedAgents`	2.4 KiB	6.2 KiB
⚪	`agents/schedule#getSchedulePrompt`	85.8 KiB	424.7 KiB
⚪	`agents/schedule#scheduleSchema`	85.3 KiB	423.6 KiB
⚪	`agents/schedule#unstable_getSchedulePrompt`	85.9 KiB	424.9 KiB
⚪	`agents/schedule#unstable_scheduleSchema`	85.3 KiB	423.6 KiB
⚪	`agents/schedules#Scheduler`	6.8 KiB	22.0 KiB
⚪	`agents/schedules/parser#getSchedulePrompt`	85.8 KiB	424.7 KiB
⚪	`agents/schedules/parser#scheduleSchema`	85.3 KiB	423.6 KiB
⚪	`agents/sessions#createCompactFunction`	1.7 KiB	4.0 KiB
🟡	`agents/sessions#Session`	2.0 KiB	6.0 KiB
🟡	`agents/sessions#Sessions`	9.0 KiB	31.8 KiB
⚪	`agents/skills#fromManifest`	309.8 KiB	1084.0 KiB
⚪	`agents/skills#parseSkillFrontmatter`	328.4 KiB	1146.2 KiB
⚪	`agents/skills#parseSkillMarkdown`	328.6 KiB	1146.5 KiB
⚪	`agents/skills#r2`	330.2 KiB	1150.4 KiB
⚪	`agents/skills#runner`	369.0 KiB	1297.8 KiB
⚪	`agents/skills#SkillRegistry`	416.4 KiB	1581.7 KiB
⚪	`agents/skills/compile#compileSkillScript`	15.4 KiB	43.4 KiB
⚪	`agents/skills/compile#isCompilableSkillScript`	15.4 KiB	43.3 KiB
🔴	`agents/streams#DEFAULT_MAX_CHUNK_BYTES`	94 B	96 B
🟡	`agents/streams#sseResponse`	855 B	1.6 KiB
🟡	`agents/streams#StreamClosedError`	175 B	212 B
🟡	`agents/streams#StreamNotFoundError`	215 B	276 B
🔴	`agents/streams#Streams`	4.1 KiB	13.5 KiB
🟡	`agents/streams#StreamSerializationError`	171 B	201 B
⚪	`agents/tasks#DuplicateTaskStepError`	328 B	463 B
⚪	`agents/tasks#MAX_SERIALIZED_BYTES`	190 B	232 B
⚪	`agents/tasks#MissingTaskDefinitionError`	358 B	536 B
⚪	`agents/tasks#NonRetryableError`	238 B	308 B
⚪	`agents/tasks#TaskReplayDivergedError`	341 B	483 B
⚪	`agents/tasks#Tasks`	8.9 KiB	31.8 KiB
⚪	`agents/tasks#TaskSerializationError`	258 B	339 B
⚪	`agents/types#MessageType`	211 B	365 B
⚪	`agents/vite#default`	353.8 KiB	1356.1 KiB
⚪	`agents/websockets#CALLABLES_RPC_QUERY`	12.4 KiB	43.3 KiB
⚪	`agents/websockets#CALLABLES_RPC_VALUE`	12.4 KiB	43.3 KiB
⚪	`agents/websockets#callablesFromDecorated`	12.7 KiB	44.3 KiB
⚪	`agents/websockets#callablesRpcUrl`	12.5 KiB	43.5 KiB
⚪	`agents/websockets#isCallablesRpcUpgrade`	12.4 KiB	43.4 KiB
⚪	`agents/websockets#WebSockets`	17.7 KiB	62.2 KiB
⚪	`agents/workflows#AgentWorkflow`	260.0 KiB	1134.8 KiB
⚪	`agents/workflows#WorkflowRejectedError`	258.7 KiB	1130.2 KiB
⚪	`agents/x402#normalizeNetwork`	14.7 KiB	61.1 KiB
⚪	`agents/x402#withX402`	23.0 KiB	89.2 KiB
⚪	`agents/x402#withX402Client`	104.1 KiB	346.5 KiB

Reported by agent-think[bot].

ctx.abort() at each point that matters — before an append commits, right after, during rollover (before/after commit), after persist before discard, and inside/after the atomic cutover — then inspect the fresh instance. Each restart finds either the exact committed prefix or the finished message.

- ResumableStream.finish() leaves a finished stream live until cutover(); cutover() settles it, runs the message write and deletes its rows in one transaction; finalizePending() settles when nothing is persisted; reclaim() on every start() replaces the alarm-driven sweep. - AIChatAgent persists the turn's messages inside the cutover (persistMessages { _cutover }); Think does the same through _persistAssistantMessageWithCutover. The session change feed and auto-compaction run once the transaction commits. - cleanupStreamBuffers / STREAM_CLEANUP_DELAY_SECONDS removed; the host _cleanupStreamBuffers callbacks stay as no-ops for persisted alarms.

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devin-ai-integration · 2026-09-04T12:47:18Z

Think

          });
          return streamResult;
        } finally {
+          this._resumableStream.finalizePending();


🔴 Failed persistence discards recovery evidence

When message persistence throws, finalizePending() settles the still-live stream in AIChatAgent and Think. Recovery then ignores its only durable response copy.

Prompt for agents

Preserve a pending stream when the cutover's message write fails. AIChatAgent in packages/ai-chat/src/index.ts and Think in packages/think/src/think.ts currently call ResumableStream.finalizePending() after catching or propagating a failed cutover. That changes the transaction's rolled-back live stream to completed without persisting its message, preventing orphan recovery. Only finalize when there was intentionally no message to persist. Leave the stream live when cutover persistence throws, and add failure-path tests for both hosts.

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pkg-pr-new · 2026-09-04T16:17:47Z

Open in StackBlitz

agents

npm i https://pkg.pr.new/agents@2216

@cloudflare/ai-chat

npm i https://pkg.pr.new/@cloudflare/ai-chat@2216

@cloudflare/codemode

npm i https://pkg.pr.new/@cloudflare/codemode@2216

hono-agents

npm i https://pkg.pr.new/hono-agents@2216

@cloudflare/shell

npm i https://pkg.pr.new/@cloudflare/shell@2216

@cloudflare/think

npm i https://pkg.pr.new/@cloudflare/think@2216

@cloudflare/voice

npm i https://pkg.pr.new/@cloudflare/voice@2216

@cloudflare/worker-bundler

npm i https://pkg.pr.new/@cloudflare/worker-bundler@2216

commit: 42d73a0

…er commit - Fold cf_agents_stream_chunks rows into blocks one stream at a time on first touch (paged reads, whole-block inserts) instead of the whole log at startup; drop the table once empty. - A settle with commit/discard is a no-op on a stream already terminal or deleted: commit does not run, nothing is discarded. ResumableStream's cutover falls back to a plain persist in that case. - Terminal, deleted events and reader wakeups fire after the cutover transaction returns, never for a rolled-back commit.

A subclass that overrides persistMessages and calls super with only the messages dropped the internal _cutover option, so the message write and the stream settlement fell back to two commits. The pending cutover now lives on the instance keyed by the turn's message id: the first persist that carries that message runs the cutover, a persist of other messages takes the plain path, and the turn's end clears it. persistMessages' public signature is unchanged.

devin-ai-integration

Devin Review found 1 new potential issue.

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devin-ai-integration · 2026-09-08T16:22:01Z

+    this.#sqlWrite("DROP TABLE cf_agents_stream_chunks", []);
+    this.#legacyChunkTable = false;


🔴 Rolled-back migration hides old chunks

When a v1 stream's first cutover rolls back, #legacyChunkTable stays false although SQLite restores the legacy table. Later reads and appends ignore every old chunk and restart the cursor at zero.

Prompt for agents

Make lazy legacy-table state consistent with transaction rollback in packages/agents/src/streams/streams.ts. foldLegacyChunks can run inside the outer cutover transaction. dropLegacyChunkTableIfEmpty currently mutates #legacyChunkTable before that outer transaction is known to commit. If the caller's commit callback throws, SQLite restores the legacy table but the instance flag remains false. Avoid retaining transaction-dependent schema state in memory, or refresh it after rollback. Add a test that seeds a v1 live stream, runs close({ commit: throwing, discard: true }), then verifies the old cursor and chunks remain visible and a new append continues at the old cursor.

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mattzcarey added 2 commits September 4, 2026 12:56

mattzcarey mentioned this pull request Sep 4, 2026

feat(streams): R2 chunk log — segment write-ahead log behind new Streams({ r2 }) #2215

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devin-ai-integration Bot reviewed Sep 4, 2026

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fix(ci): drop cleanupStreamBuffers from experimental agents; test typing

d9bf4e0

mattzcarey added 2 commits September 8, 2026 17:03

devin-ai-integration Bot reviewed Sep 8, 2026

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mattzcarey merged commit dd09d44 into main Sep 8, 2026
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mattzcarey deleted the feat/streams-block-log-atomic-cutover branch September 8, 2026 16:37

github-actions Bot mentioned this pull request Sep 8, 2026

Version Packages #2174

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feat(streams): rollover block log and atomic stream → session cutover - #2216

feat(streams): rollover block log and atomic stream → session cutover#2216
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		this.#sqlWrite("DROP TABLE cf_agents_stream_chunks", []);
		this.#legacyChunkTable = false;

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Crash matrix (ctx.abort() at each point; in-repo as src/e2e-tests/stream-cutover-crash.test.ts against wrangler dev, and reproduced on a deployed DO)

Tests

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🔴 agents import sizes

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mattzcarey commented Sep 4, 2026 •

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Crash matrix (`ctx.abort()` at each point; in-repo as `src/e2e-tests/stream-cutover-crash.test.ts` against `wrangler dev`, and reproduced on a deployed DO)

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