feat(examples): add a self-modifying harness by mattzcarey · Pull Request #2207 · cloudflare/agents

mattzcarey · 2026-09-03T11:40:17Z

Summary

Adds an example-only SelfModifyingHarness under examples/next/harnesses/self-modifying. No package export, no changeset.

The example composes a plain DurableObject with Lifecycle, Tasks, Streams, WebSockets, a durable Shell Workspace, Worker Bundler, and Worker Loader. The editable TypeScript harness is versioned in the Workspace and loaded into a fresh Dynamic Worker for every chat turn.

How it works

SelfModifyingHarness accepts an AI SDK LanguageModelV4; the example passes the workers-ai-provider@4 model directly.
System tools are fixed trusted capabilities for source access, activation, restore, and journaling. They execute in the Durable Object over a turn-scoped RPC target.
Custom tools are editable CustomTool exports under /harness/src/tools/ and execute inside the Dynamic Worker. Activation discovers them; a Custom tool cannot shadow a System tool.
Activation snapshots the Workspace source, bundles it, checks it in an isolated Worker, and atomically advances the active revision.
Turns run as one Tasks step, pin their revision, journal model and tool effects by stable key, and publish events through Streams.
The UI is served over the WebSockets capability. The client connects with useAgent from agents/react; a useHarnessSession hook replays-then-tails each turn's Streams log. The Kumo chat shows tool calls per turn, and an inspector shows the active revision's code, the revision history with a restore action, and the journal.

Review

Start with the README, then src/self-modifying-harness.ts, src/harness-runtime.ts, and src/transport.ts.

Worker Loader access is required to run or deploy this example. The example's Workers-runtime tests drive a deterministic LanguageModelV4 through the real Durable Object over RPC.

changeset-bot · 2026-09-03T11:40:21Z

⚠️ No Changeset found

Latest commit: 8930378

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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

agent-think · 2026-09-03T11:43:37Z

⚪ agents import sizes

Measured 287 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
0	0	0	287	0	0

Compared 6da4c44b with 27004a09. Open workflow run.

No import sizes changed.

All 287 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`	2.6 KiB	9.5 KiB
⚪	`agents/chat#AgentToolStreamProgressThrottle`	2.3 KiB	8.3 KiB
⚪	`agents/chat#aiSdkRecoveryCodec`	2.3 KiB	8.2 KiB
⚪	`agents/chat#applyAgentToolEvent`	3.2 KiB	10.9 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`	3.1 KiB	11.4 KiB
⚪	`agents/chat#buildChatRecoveringFrame`	2.4 KiB	8.3 KiB
⚪	`agents/chat#buildInClauseStrings`	2.4 KiB	8.4 KiB
⚪	`agents/chat#bumpChatRecoveryProgress`	2.3 KiB	8.3 KiB
⚪	`agents/chat#byteLength`	2.3 KiB	8.2 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	15.2 KiB
⚪	`agents/chat#chatRecoveryTaskRunOptions`	2.4 KiB	8.5 KiB
⚪	`agents/chat#ChatStreamStalledError`	2.3 KiB	8.3 KiB
⚪	`agents/chat#classifyAgentToolChildRecovery`	2.4 KiB	8.5 KiB
⚪	`agents/chat#cleanupStreamBuffers`	2.3 KiB	8.2 KiB
⚪	`agents/chat#clearChatTerminal`	2.3 KiB	8.2 KiB
⚪	`agents/chat#clientResolvableToolNames`	2.3 KiB	8.3 KiB
⚪	`agents/chat#ContinuationState`	2.6 KiB	9.8 KiB
⚪	`agents/chat#createAgentToolEventState`	2.3 KiB	8.2 KiB
⚪	`agents/chat#createChatFiberSnapshot`	2.4 KiB	8.6 KiB
⚪	`agents/chat#createChatRecoveryTaskDefinition`	2.6 KiB	9.0 KiB
⚪	`agents/chat#createChatStreams`	5.5 KiB	19.3 KiB
⚪	`agents/chat#createChatTurnTaskDefinition`	2.6 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`	2.3 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`	3.4 KiB	11.0 KiB
⚪	`agents/chat#hasIncompleteToolBatch`	2.4 KiB	8.6 KiB
⚪	`agents/chat#interceptAgentToolBroadcast`	2.5 KiB	8.6 KiB
⚪	`agents/chat#isPlatformFailure`	2.6 KiB	8.9 KiB
⚪	`agents/chat#isReplayChunk`	2.4 KiB	8.6 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	8.5 KiB
⚪	`agents/chat#pausedExecutionUpdate`	2.4 KiB	8.4 KiB
⚪	`agents/chat#pendingChatTerminal`	2.3 KiB	8.3 KiB
⚪	`agents/chat#persistReconstructedOrphan`	3.0 KiB	11.0 KiB
⚪	`agents/chat#PreStreamTurns`	2.6 KiB	9.2 KiB
⚪	`agents/chat#readChatRecoveryProgress`	2.3 KiB	8.3 KiB
⚪	`agents/chat#reconcileMessages`	2.8 KiB	9.5 KiB
⚪	`agents/chat#reconcileOrphanPartial`	2.4 KiB	8.4 KiB
⚪	`agents/chat#recordChatTerminal`	2.3 KiB	8.3 KiB
⚪	`agents/chat#repairInterruptedToolParts`	2.6 KiB	9.1 KiB
⚪	`agents/chat#resolveChatRecoveryConfig`	2.5 KiB	8.9 KiB
⚪	`agents/chat#resolveToolMergeId`	2.4 KiB	8.5 KiB
⚪	`agents/chat#ResumableStream`	4.6 KiB	15.3 KiB
⚪	`agents/chat#ResumeHandshake`	2.9 KiB	10.4 KiB
⚪	`agents/chat#ROW_MAX_BYTES`	2.3 KiB	8.2 KiB
⚪	`agents/chat#runChatRecoveryExhaustion`	2.5 KiB	8.9 KiB
⚪	`agents/chat#sanitizeMessage`	2.5 KiB	9.0 KiB
⚪	`agents/chat#sendIfOpen`	2.4 KiB	8.3 KiB
⚪	`agents/chat#setChatRecovering`	2.4 KiB	8.5 KiB
⚪	`agents/chat#shouldCreditStreamProgress`	2.3 KiB	8.3 KiB
⚪	`agents/chat#STREAM_CLEANUP_DELAY_SECONDS`	2.3 KiB	8.2 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`	2.3 KiB	8.3 KiB
⚪	`agents/chat#SubmitConcurrencyController`	2.9 KiB	10.2 KiB
⚪	`agents/chat#sweepStaleChatRecoveryIncidents`	2.4 KiB	8.4 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	8.3 KiB
⚪	`agents/chat#toolResultUpdate`	2.4 KiB	8.4 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/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/memory/session#AgentContextProvider`	425 B	810 B
⚪	`agents/experimental/memory/session#AgentSearchProvider`	821 B	2.0 KiB
⚪	`agents/experimental/memory/session#AgentSessionProvider`	2.5 KiB	8.8 KiB
⚪	`agents/experimental/memory/session#isSearchProvider`	128 B	134 B
⚪	`agents/experimental/memory/session#isSkillProvider`	127 B	130 B
⚪	`agents/experimental/memory/session#isWritableProvider`	126 B	128 B
⚪	`agents/experimental/memory/session#PostgresContextProvider`	422 B	671 B
⚪	`agents/experimental/memory/session#PostgresSearchProvider`	630 B	1.1 KiB
⚪	`agents/experimental/memory/session#PostgresSessionProvider`	1.7 KiB	5.3 KiB
⚪	`agents/experimental/memory/session#R2SkillProvider`	436 B	791 B
⚪	`agents/experimental/memory/session#Session`	93.4 KiB	454.0 KiB
⚪	`agents/experimental/memory/session#SessionManager`	94.5 KiB	460.1 KiB
⚪	`agents/experimental/memory/utils#alignBoundaryBackward`	291 B	584 B
⚪	`agents/experimental/memory/utils#alignBoundaryForward`	275 B	539 B
⚪	`agents/experimental/memory/utils#buildSummaryPrompt`	867 B	2.0 KiB
⚪	`agents/experimental/memory/utils#CHARS_PER_TOKEN`	51 B	31 B
⚪	`agents/experimental/memory/utils#COMPACTION_PREFIX`	63 B	43 B
⚪	`agents/experimental/memory/utils#computeSummaryBudget`	363 B	634 B
⚪	`agents/experimental/memory/utils#createCompactFunction`	1.8 KiB	4.2 KiB
⚪	`agents/experimental/memory/utils#estimateMessageTokens`	336 B	567 B
⚪	`agents/experimental/memory/utils#estimateStringTokens`	142 B	145 B
⚪	`agents/experimental/memory/utils#findTailCutByTokens`	597 B	1.3 KiB
⚪	`agents/experimental/memory/utils#isCompactionMessage`	98 B	83 B
⚪	`agents/experimental/memory/utils#sanitizeToolPairs`	537 B	1.1 KiB
⚪	`agents/experimental/memory/utils#TOKENS_PER_MESSAGE`	51 B	31 B
⚪	`agents/experimental/memory/utils#truncateOlderMessages`	1022 B	2.2 KiB
⚪	`agents/experimental/memory/utils#WORDS_TOKEN_MULTIPLIER`	53 B	33 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/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`	397.5 KiB	1513.3 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`	83 B	81 B
⚪	`agents/streams#sseResponse`	843 B	1.6 KiB
⚪	`agents/streams#StreamClosedError`	161 B	197 B
⚪	`agents/streams#StreamNotFoundError`	201 B	261 B
⚪	`agents/streams#Streams`	3.4 KiB	11.1 KiB
⚪	`agents/streams#StreamSerializationError`	158 B	186 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].

pkg-pr-new · 2026-09-03T11:53:56Z

Open in StackBlitz

agents

npm i https://pkg.pr.new/agents@2207

@cloudflare/ai-chat

npm i https://pkg.pr.new/@cloudflare/ai-chat@2207

@cloudflare/codemode

npm i https://pkg.pr.new/@cloudflare/codemode@2207

hono-agents

npm i https://pkg.pr.new/hono-agents@2207

@cloudflare/shell

npm i https://pkg.pr.new/@cloudflare/shell@2207

@cloudflare/think

npm i https://pkg.pr.new/@cloudflare/think@2207

@cloudflare/voice

npm i https://pkg.pr.new/@cloudflare/voice@2207

@cloudflare/worker-bundler

npm i https://pkg.pr.new/@cloudflare/worker-bundler@2207

commit: 27004a0

…lity Replace the HTTP operator API with a WebSocket protocol on the WebSockets capability: an object snapshot on connect, subscribe to replay-then-tail a turn's Streams log, and submit, write_source, activate, and restore commands. Turn and revision changes broadcast to every connection. The client connects with useAgent from agents/react through a useHarnessSession hook and uses the same Kumo chat layout as the other harness examples, with tool cards per turn and an inspector for the active revision's code, revision history with restore, and the journal. The worker routes with routeAgentRequest. Tests drive the test object over RPC instead of the removed HTTP adapter. Drop the dev-time journal column migration and the duplicated file list from the snapshot. Claude-Session: https://claude.ai/code/session_01KEFnjoMnZBMewsuD9qxGrL

devin-ai-integration

Devin Review found 7 potential issues.

3 flags not posted on this PR by your GitHub settings — view them in Devin Review. (Configure)

devin-ai-integration · 2026-09-03T13:30:43Z

+    } catch (error) {
+      outcome = taskOutcome({ ok: false, error: errorMessage(error) });
+    }


🟡 Task retries become terminal failures

When step.do schedules a retry, this catch converts its suspension into a completed failure outcome. The task settles immediately, so retries never run.

Prompt for agents

Allow Tasks control-flow exceptions from step.do to propagate so ReplayStep can park or retry the run. Only convert a genuinely terminal editable-harness outcome into TurnTaskOutcome. The current catch also swallows TaskSuspension, defeating the configured retry policy and settling the step with ok:false.

Was this helpful? React with 👍 or 👎 to provide feedback.

devin-ai-integration · 2026-09-03T13:30:44Z

+const ENTRY_SOURCE = `import { WorkerEntrypoint } from "cloudflare:workers";
+import harness from "./src/index";


🟡 Custom-tool validation can be bypassed

If edited src/index.ts omits the virtual registry, compileHarness never evaluates tool modules. Activation accepts invalid tools, while valid tools disappear.

Prompt for agents

Make the immutable generated entrypoint import the generated custom-tools registry unconditionally, then expose its definitions and dispatcher to editable code through a contract that does not depend on src/index.ts retaining a particular import. Activation must evaluate every src/tools/*.ts module even after the editable entrypoint is reorganized, so malformed, duplicate, and System-shadowing tools still reject the candidate.

Was this helpful? React with 👍 or 👎 to provide feedback.

devin-ai-integration · 2026-09-03T13:30:45Z

+    if (prompt.trim() === "") throw new Error("Turn prompt must not be empty");
+    const active = this.#store.activeBuild();
+    if (!active) throw new Error("Harness genesis has not been activated");
+    const existing = this.#store.turn(turnId);


🟡 Concurrent turns corrupt conversation order

#admit accepts turns while earlier ones remain active. Their prompts and replies interleave, so later model history no longer represents a valid conversation.

Prompt for agents

Serialize turn admission at the server, not only in each browser's busy state. Before accepting a new turn, reject it or queue it behind every queued/running turn. Ensure history for a turn is assembled only after all preceding turns have terminal assistant output, including submissions racing from multiple WebSocket connections.

Was this helpful? React with 👍 or 👎 to provide feedback.

devin-ai-integration · 2026-09-03T13:30:46Z

+        case "write_source":
+          await this.#host.writeSource(message.path, message.content);


🟥 Unauthenticated clients replace executable code

Any client can send write_source, activate, or restore without authorization. Attackers can replace the shared harness code executed by later turns.

Was this helpful? React with 👍 or 👎 to provide feedback.

devin-ai-integration · 2026-09-03T13:30:48Z

+function absoluteHarnessPath(path: string): string {
+  const absolute = path.startsWith("/") ? path : `${HARNESS_ROOT}${path}`;
+  if (
+    !absolute.startsWith(HARNESS_ROOT) ||
+    absolute.includes("/../") ||
+    absolute.endsWith("/..")
+  ) {
+    throw new HarnessPathError(
+      `Harness source path must remain under ${HARNESS_ROOT}: ${JSON.stringify(path)}`
+    );
+  }
+  if (absolute === HARNESS_ROOT) {
+    throw new HarnessPathError("Harness source path must name a file");
+  }
+  return absolute;


🟥 Symlinks escape the harness directory

absoluteHarnessPath validates only the written path before Workspace follows symlinks. A harness symlink can read or overwrite files outside /harness.

Was this helpful? React with 👍 or 👎 to provide feedback.

devin-ai-integration · 2026-09-03T13:30:49Z

+function isClientMessage(value: unknown): value is HarnessClientMessage {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    "type" in value &&
+    typeof value.type === "string"
+  );


🟨 WebSocket payloads bypass validation

isClientMessage accepts any object with a string type. Malformed or oversized fields reach source writes, builds, subscriptions, and model turns unchecked.

Was this helpful? React with 👍 or 👎 to provide feedback.

…tor port Deploy as self-modifying-harness-example, give the Vite dev server its own inspector port so it can run beside the other harness examples, and note CLOUDFLARE_ACCOUNT_ID for logins with several accounts.

agents/react resolved a second React copy from the agents package, which broke every hook call in the browser.

…the client A closed stream ends as soon as it is replayed, and every stream end asked for a snapshot that resubscribed to every turn, so the page kept re-rendering and scrolling to the bottom. Subscribe to each turn once per connection, refresh only after a live tail ends, and scroll only when content is added.

…at header

feat(examples): add self-modifying harness

e8ee781

mattzcarey marked this pull request as ready for review September 3, 2026 13:22

devin-ai-integration Bot reviewed Sep 3, 2026

View reviewed changes

mattzcarey added 5 commits September 3, 2026 15:20

fix(self-modifying-harness): dedupe React so the client renders

27004a0

agents/react resolved a second React copy from the agents package, which broke every hook call in the browser.

chore(self-modifying-harness): shorten the UI copy

01373a5

chore(self-modifying-harness): align the inspector header with the ch…

8930378

…at header

Navigation Menu

Uh oh!

feat(examples): add a self-modifying harness - #2207

feat(examples): add a self-modifying harness#2207
mattzcarey wants to merge 7 commits into
cloudflare:mainfrom
mattzcarey:feat/self-modifying-harness

mattzcarey commented Sep 3, 2026 •

edited

Loading

Uh oh!

changeset-bot Bot commented Sep 3, 2026 •

edited

Loading

Uh oh!

agent-think Bot commented Sep 3, 2026 •

edited

Loading

Uh oh!

pkg-pr-new Bot commented Sep 3, 2026 •

edited

Loading

Uh oh!

devin-ai-integration Bot left a comment

Uh oh!

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

		const ENTRY_SOURCE = `import { WorkerEntrypoint } from "cloudflare:workers";
		import harness from "./src/index";

		case "write_source":
		await this.#host.writeSource(message.path, message.content);

Uh oh!

Conversation

mattzcarey commented Sep 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

How it works

Review

Uh oh!

changeset-bot Bot commented Sep 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

⚠️ No Changeset found

Uh oh!

agent-think Bot commented Sep 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

⚪ agents import sizes

Uh oh!

pkg-pr-new Bot commented Sep 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

devin-ai-integration Bot left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

devin-ai-integration Bot Sep 3, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

mattzcarey commented Sep 3, 2026 •

edited

Loading

changeset-bot Bot commented Sep 3, 2026 •

edited

Loading

agent-think Bot commented Sep 3, 2026 •

edited

Loading

pkg-pr-new Bot commented Sep 3, 2026 •

edited

Loading