Tutorials

Field notes on RAG, evals, agents, and LLM cost.

Your Index Is a Stale Copy: Incremental Sync, Deletes, and Reindexing for Production RAG

September 21, 2026

Most RAG projects tune retrieval and never revisit the pipeline that fills the index. How to do incremental sync with content hashes, propagate deletes, and reindex behind a shadow index without a quality cliff.

Latency Budgets for LLM Apps: Where the Seconds Actually Go

September 21, 2026 · TokenTailors

Time to first token, stage-level timing, prefix caching, parallel retrieval, and streaming: how to find and cut the seconds in a production LLM app without trading away quality.

Permission-Aware RAG: Enforcing Document Access Control in Retrieval

September 18, 2026

The moment your corpus spans more than one customer or one security group, retrieval becomes an authorization surface. How to filter at the index, keep recall honest, and test for leaks.

Migrating to LangChain 1.0: create_agent, Middleware, and the Code You Get to Delete

September 17, 2026

A staged migration off AgentExecutor and legacy chains: what create_agent and agent middleware actually change, what to delete instead of port, and how to guard the refactor with evals.

Swapping Embedding Models Without a Retrieval Regression

September 16, 2026 · TokenTailors

A new embedding model tops the leaderboard and someone proposes a re-index. Here is how to decide whether it helps your corpus, and how to run the migration behind a shadow index without a quality cliff.