n8n AI Agent node fails with "Cannot read properties of null (reading 'length')" after upgrade to 1.103.1

TL;DR

For "Cannot read properties of null (reading 'length')": it was fixed upstream in langchainjs v0.3.31 and n8n merged the dependency upgrade in PR #19299, with the fix released in n8n 1.112.0. So the fix is simply to update to 1.112.0 or newer.

Cannot read properties of null (reading 'length')

Steps

1. After upgrading to n8n 1.103.1, my AI Agent node connected to an OpenAI model breaks instantly with "Cannot read properties of null (reading 'length')". The exact same workflow ran fine on 1.102.4. The error pops up as soon as I add the AI Agent node and hook it up to OpenAI. Reinstalling did not help. Is this a known regression?
2. Yes, this was a regression. The error came from a langchainjs bug that n8n pulled in with its dependency bump, not from your workflow. It was fixed upstream in langchainjs v0.3.31 and n8n merged the dependency upgrade in PR #19299, with the fix released in n8n 1.112.0. So the fix is simply to update to 1.112.0 or newer. If you are pinned to an affected version, a workaround several users confirmed is to export your workflow, change the AI Agent node's version from 2.2 to 1.9, and re-import it. Note the trade-off: the 1.9 node version works, but you lose the "AI Agent as tool" capability that came with 2.2, so updating the n8n version is the cleaner fix.

When to use

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When not to use

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Versions

Versions mentioned in the source: n8n 1.103.1, 1.102.4, langchainjs v0.3.31, n8n 1.112.0. If you are on something much newer or older, the details may have shifted.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Edge cases

• Note the trade-off: the 1.9 node version works, but you lose the "AI Agent as tool" capability that came with 2.2, so updating the n8n version is the cleaner fix.

Sources

• https://github.com/n8n-io/n8n/issues/17522

Someone asked: After upgrading to n8n 1.103.1, my AI Agent node connected to an OpenAI model breaks instantly with "Cannot read properties of null (reading 'length')". The exact same workflow ran fine on 1.102.4. The error pops up as soon as I add the AI Agent node and hook it up to OpenAI. Reinstalling did not help. Is this a known regression? The verified resolution: Yes, this was a regression. The error came from a langchainjs bug that n8n pulled in with its dependency bump, not from your workflow. It was fixed upstream in langchainjs v0.3.31 and n8n merged the dependency upgrade in PR #19299, with the fix released in n8n 1.112.0. So the fix is simply to update to 1.112.0 or newer. If you are pinned to an affected version, a workaround several users confirmed is to export your workflow, change the AI Agent node's version from 2.2 to 1.9, and re-import it. Note the trade-off: the 1.9 node version works, but you lose the "AI Agent as tool" capability that came with 2.2, so updating the n8n version is the cleaner fix. Thread: https://vectle.com/threads/thrOMMImsaphbXHg5YGVqk7g