LangChain upgrades break working setups

Outages and change3 posts from 3 people3d active+22 posts in the last 7 days, 1 the 7 days before (steady)

Posts per day3 posts, Sep 24 to Oct 4

The posts behind it

3, newest first

Post	Where	Date
v3 streaming: tool-call `block-delta` events are snapshots, so their size grows quadratically with the tool-call arguments### Submission checklist - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than...langchain-ai/langchainNicolas-Ding	langchain-ai/langchainNicolas-Ding1 replies	Oct 22 days ago
`with_fallbacks(exception_key=...)` writes the exception into the caller's own input mapping Package：langchain-core### Submission checklist - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than...langchain-ai/langchainIris070308	langchain-ai/langchainIris0703082 replies	Sep 286 days ago
CriteriaResultOutputParser takes the last or first letter of a word as the Y/N verdict (`match_last`/`match_first` have no `\b`)...word boundary, and none of the cuts contains a verdict line: - A 6-sentence reply for a failing submission has 49 cuts. 3 score 1 (for example `...The submission states that the capital of Germany`, value `y`), 4 score 0 and 42 score None. - A reply for a passing submission has...langchain-ai/langchainshaurya416	langchain-ai/langchainshaurya4161 replies	Sep 2410 days ago

Companies and products named

Company or product	Posts naming it
LangChain	3
Anthropic	1
OpenAI	1
Perplexity	1
DeepSeek	1
Ollama	1

About this problem

Evidence

3 posts from 3 people in 1 place, about 2 a week over 9 days. Mostly on langchain-ai/langchain. Tools named alongside: Anthropic, OpenAI, Perplexity, DeepSeek.

Frustration Frustration 0 of 3· Seen on GitHub issues

How it was grouped

Posts that state a pain and match the "breaking-changes" rule about LangChain. First post Sep 24, 2026, latest Oct 2, 2026. Corroborated: 3 or more posts from 2 or more people or places. Method

The same problem elsewhere

Posts per day

The posts behind it

Companies and products named

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