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perf(langgraph): avoid calling maxChannelMapVersion twice #1622

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Merged
merged 2 commits into from
Sep 9, 2025
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perf(langgraph): avoid calling maxChannelMapVersion twice #1622

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perf(langgraph): avoid calling `maxChannelMapVersion` twice
dqbd Sep 9, 2025
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dqbd Sep 9, 2025
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5 changes: 5 additions & 0 deletions .changeset/odd-paws-destroy.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@langchain/langgraph": patch
---

Improve tick performance by calling `maxChannelMapVersion` only once
6 changes: 5 additions & 1 deletion libs/langgraph/src/pregel/algo.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -272,10 +272,12 @@ export function _applyWrites<Cc extends Record<string, BaseChannel>>(
.filter((chan) => !RESERVED.includes(chan))
);

let usedNewVersion = false;
for (const chan of channelsToConsume) {
if (chan in onlyChannels && onlyChannels[chan].consume()) {
if (getNextVersion !== undefined) {
checkpoint.channel_versions[chan] = getNextVersion(maxVersion);
usedNewVersion = true;
}
}
}
Expand All @@ -294,7 +296,9 @@ export function _applyWrites<Cc extends Record<string, BaseChannel>>(
}

// Find the highest version of all channels
maxVersion = maxChannelMapVersion(checkpoint.channel_versions);
if (maxVersion != null && getNextVersion != null) {
maxVersion = usedNewVersion ? getNextVersion(maxVersion) : maxVersion;
}

const updatedChannels: Set<string> = new Set();
// Apply writes to channels
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