Plan: vCon LangChain tool set

[howethomas]

Summary

Adds a design/implementation plan (docs/design/langchain-toolset-plan.md) for exposing vCons to LangChain agents as a first-class tool set. No code changes yet — this PR is the plan for review before implementation.

The proposal:

• A standalone, installable vcon_langchain package (kept dep-light and separate from server-only deps).
• REST-backed by default via a small VconBackend protocol (VconApiBackend over the existing api/api.py), so agents don't need to share a process/Redis with the conserver. An in-process VconRedis backend can be added later without touching the tool layer.
• A set of langchain_core StructuredTools with typed Pydantic args schemas and LLM-facing descriptions — read tools (get_vcon, search_vcons, list_recent_vcons, convenience get_vcon_transcript / get_vcon_analysis / get_vcon_parties / get_vcon_tags) plus opt-in write tools (add_vcon_tag, create_vcon, submit_vcon_to_chain). Destructive delete_vcon excluded by default.
• A VconToolkit(BaseToolkit) assembling the tools; sync + async execution.
• Optional langchain dependency group in pyproject.toml (langchain-core, httpx), with a guarded import mirroring the Milvus backend pattern.
• Unit tests using a fake backend (no live conserver), and docs under docs/extending/ + mkdocs nav.

Why this is a new surface (not a "link")

Links are pushed work by the conserver worker (run(vcon_uuid, link_name, opts)); LangChain tools are pulled by an LLM agent on demand (BaseTool + args schema). They're complementary — existing links are unchanged.

Design decisions grounded in the codebase

• Convenience extract tools return only the salient slice of a vCon (transcript/analysis/parties) to save tokens, reusing the server's encoding: json body-decode semantics (Vcon.decoded_body) as a pure function with no server dependency.
• Mutations are read-modify-write against the API (no PATCH endpoint) — documented as last-write-wins.
• create_vcon uses the canonical vcon>=0.9.2 library already in core deps rather than re-implementing UUID8 generation.

Open questions for reviewers

Captured in §11 of the doc: REST-first vs in-process backend default, package home, whether v1 should be read-only, and keeping delete_vcon opt-in.

🤖 Generated with Claude Code

---

Generated by Claude Code