fix(task-graph): cap bridgeSubGraphTaskEvents depth to prevent event amplification#601
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fix(task-graph): cap bridgeSubGraphTaskEvents depth to prevent event amplification#601sroussey wants to merge 1 commit into
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…amplification bridgeSubGraphTaskEvents installs one re-emit listener per event type per nesting level. A deeply nested compound task (e.g., a MapTask containing GraphAsTask containing MapTask) turns one inner task_progress into N parent emits before reaching any wire subscriber. Downstream consumers with a bounded event log (the sec/builder ExecutionEventLog is capped at 10k events) can evict legitimate events under sustained nested fan-out. Add a default depth cap of 16 with a logged drop once exceeded, and let callers override via the new maxDepth parameter. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01V3e3m8cMRy5stFhDzGmZrF
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Summary
bridgeSubGraphTaskEventsinstalls one re-emit listener per event type per nesting level. A deeply nested compound task (e.g. aMapTaskcontaining aGraphAsTaskcontaining aMapTask…) bridges every level independently, so a single innertask_progressbecomes N parent emits before reaching any wire subscriber. Combined with downstream consumers that keep a bounded event log (the sec/builderExecutionEventLogis capped at 10k events), sustained nested fan-out can silently evict legitimate events.This PR adds a defense-in-depth depth cap with a default of 16 levels. Once exceeded, the bridge installs no listeners and emits a single
warnlog noting the cap hit. The cap is overridable via a newmaxDepthparameter; depth is auto-derived from a symbol-keyed marker on the parent graph so existing call sites (GraphAsTaskRunner,WhileTask,IteratorTaskRunner,FallbackTaskRunner,GraphAsTaskstreaming path) compile unchanged.Approach
Depth tracking lives on the graph instance via a
Symbol.for("@workglow/task-graph/SubGraphEventBridge.depth")keyed property — chosen over threading a counter through every caller because it keeps the diff to one file of fix code plus one re-export. The teardown restores the previous marker so an independently-rooted later bridge of the same subgraph instance does not inherit a stale counter.Files
packages/task-graph/src/task-graph/SubGraphEventBridge.ts— depth cap + warn logpackages/task-graph/src/common.ts— re-exportbridgeSubGraphTaskEventsso the test can drive it directlypackages/test/src/test/task-graph/TaskCompleteEvent.test.ts— three new testsBackwards compatibility
Patch-bump compatible: both new parameters have defaults; every existing caller still compiles. No behavior change for graphs nesting fewer than 16 bridges deep.
Test plan
bun scripts/test.ts graph vitest— 74 files, 728 tests passing (including 3 new)bun run build:types— 36 successful, 36 total{ depth, maxDepth }fields;maxDepthoverride is honoredGenerated with Claude Code
https://claude.ai/code/session_01V3e3m8cMRy5stFhDzGmZrF
Generated by Claude Code