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[PR #4163] docs: add custom checkpointer implementation guide with delta channel support #4157

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opened 2026-06-05 19:12:58 -04:00 by yindo · 0 comments
yindo commented 2026-06-05 19:12:58 -04:00
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📋 Pull Request Information

Original PR: https://github.com/langchain-ai/docs/pull/4163
Author: @sydney-runkle
Created: 5/26/2026
Status: 🔄 Open

Base: main ← Head: sr/custom-checkpointer-delta

📝 Commits (1)

  • 219104c docs: add custom checkpointer implementation guide with delta channel support

📊 Changes

4 files changed (+454 additions, -1 deletions)

View changed files

📝 src/docs.json (+7 -1)
📝 src/langsmith/custom-checkpointer.mdx (+1 -0)
➕ src/oss/python/integrations/checkpointers/build-custom.mdx (+444 -0)
📝 src/oss/python/integrations/checkpointers/index.mdx (+2 -0)

📄 Description

Summary

  • Adds src/oss/python/integrations/checkpointers/build-custom.mdx — a new implementation guide covering the full BaseCheckpointSaver contract, row key / index design, serialization requirements, and a dedicated delta channel support section
  • The delta channel section covers: the get_delta_channel_history default walk (and why get_tuple(by-id) must be correct), a performance-override pattern, and pruning / copy-thread caveats
  • Updates checkpointers/index.mdx and langsmith/custom-checkpointer.mdx to link to the new guide
  • Expands the checkpointers nav entry in docs.json to a sub-group with both the index and the new build page

Motivation

Surfaced from a customer support case: a custom Bigtable checkpointer was silently producing empty delta channel state. Root cause was a pre-existing get_tuple(by-id) bug that delta channels promoted from "only hit during time travel" to "hit on every graph load." No docs existed explaining what the get_tuple specific-id path is required for, or what delta channels need from a checkpointer.

Test plan

  • Review prose for accuracy against langgraph.checkpoint.base.BaseCheckpointSaver
  • Verify nav renders correctly in Mintlify preview
  • Confirm links to /oss/python/integrations/checkpointers/build-custom, /langsmith/custom-checkpointer, and /oss/langgraph/persistence resolve

🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.

## 📋 Pull Request Information **Original PR:** https://github.com/langchain-ai/docs/pull/4163 **Author:** [@sydney-runkle](https://github.com/sydney-runkle) **Created:** 5/26/2026 **Status:** 🔄 Open **Base:** `main` ← **Head:** `sr/custom-checkpointer-delta` --- ### 📝 Commits (1) - [`219104c`](https://github.com/langchain-ai/docs/commit/219104c950752274fb0ac23d1c96130a89b65183) docs: add custom checkpointer implementation guide with delta channel support ### 📊 Changes **4 files changed** (+454 additions, -1 deletions) <details> <summary>View changed files</summary> 📝 `src/docs.json` (+7 -1) 📝 `src/langsmith/custom-checkpointer.mdx` (+1 -0) ➕ `src/oss/python/integrations/checkpointers/build-custom.mdx` (+444 -0) 📝 `src/oss/python/integrations/checkpointers/index.mdx` (+2 -0) </details> ### 📄 Description ## Summary - Adds `src/oss/python/integrations/checkpointers/build-custom.mdx` — a new implementation guide covering the full `BaseCheckpointSaver` contract, row key / index design, serialization requirements, and a dedicated delta channel support section - The delta channel section covers: the `get_delta_channel_history` default walk (and why `get_tuple(by-id)` must be correct), a performance-override pattern, and pruning / copy-thread caveats - Updates `checkpointers/index.mdx` and `langsmith/custom-checkpointer.mdx` to link to the new guide - Expands the checkpointers nav entry in `docs.json` to a sub-group with both the index and the new build page ## Motivation Surfaced from a customer support case: a custom Bigtable checkpointer was silently producing empty delta channel state. Root cause was a pre-existing `get_tuple(by-id)` bug that delta channels promoted from "only hit during time travel" to "hit on every graph load." No docs existed explaining what the `get_tuple` specific-id path is required for, or what delta channels need from a checkpointer. ## Test plan - [ ] Review prose for accuracy against `langgraph.checkpoint.base.BaseCheckpointSaver` - [ ] Verify nav renders correctly in Mintlify preview - [ ] Confirm links to `/oss/python/integrations/checkpointers/build-custom`, `/langsmith/custom-checkpointer`, and `/oss/langgraph/persistence` resolve --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>
yindo added the pull-request label 2026-06-05 19:12:58 -04:00
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Reference: langchain-ai/docs#4157
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