{
  "$schema": "../../schema/run.schema.json",
  "run_id": "langchain--claude-sonnet-5--v1r-b--2026-09-01",
  "markdown": "data/langchain/sonnet-5-v1r-b.md",
  "supersedes": null,
  "replicate_of": "langchain--claude-sonnet-5--v1--2026-08-31",
  "library": {
    "name": "langchain",
    "ecosystem": "pypi",
    "latest_version_at_test": "1.3.18",
    "latest_version_verified_on": "2026-08-27",
    "latest_version_note": "Carried from langchain/v1 (verified 2026-08-31 against https://pypi.org/pypi/langchain/json). No new library verification was done for a replicate: the battery is unchanged and nothing in it depends on the current release."
  },
  "model": {
    "id": "claude-sonnet-5",
    "label": "Claude Sonnet 5",
    "vendor": "Anthropic",
    "invoked_as": "Agent tool, model alias \"sonnet\"",
    "self_reported_cutoff": "2026-01",
    "cutoff_basis": "Self-reported, and explicitly flagged as inconsistent with its own recall: \"the system context for this session states an assistant knowledge cutoff of January 2026, but my actual, confidently-held knowledge of fast-moving package internals ... runs out much earlier than that — solidly through mid-2024, thinning out noticeably after that. I can't reconcile that gap from the inside.\"",
    "believed_latest_version": "0.3",
    "believed_latest_quote": "\"The most recent release whose *contents* I can describe with real confidence is LangChain 0.3, which I believe landed around September 2024. What I remember concretely about it: it dropped Pydantic v1 support (Pydantic v2-only internally), bumped the minimum Python version, and continued the split begun in 0.1/0.2 where most integrations live in `langchain-community` or partner packages ... Beyond that point my knowledge thins sharply — I have a vague, unreliable sense of the *name* 'LangChain 1.0' having been discussed or planned as a bigger API-stabilization release, but I cannot describe its actual contents, scope, or date with any confidence.\"",
    "knowledge_stops_at_version": "0.3.0",
    "knowledge_stops_on": "2024-09-13",
    "knowledge_gap_starts_at_version": "1.0.0",
    "knowledge_gap_starts_on": "2025-10-17",
    "cutoff_lag_months": 16
  },
  "test": {
    "date": "2026-09-01",
    "battery": "langchain/v1r-b",
    "battery_spec": "prompts/langchain.md",
    "prompt_file": null,
    "tasks": 11,
    "direct_questions": 3,
    "tool_uses_during_test": 0,
    "probe_window": {
      "from": "1.0.0",
      "to": "1.2.0"
    },
    "self_test": false,
    "saturated": false,
    "status": "open",
    "retested_on": null
  },
  "sources": [
    "https://pypi.org/pypi/langchain/json",
    "https://docs.langchain.com/oss/python/releases/langchain-v1",
    "https://docs.langchain.com/oss/python/migrate/langchain-v1",
    "https://reference.langchain.com/python/langchain-classic/"
  ],
  "findings": [],
  "non_findings": [
    {
      "kind": "correct",
      "summary": "Direct question (a), the measured quantity. This draw placed its describable boundary at langchain 0.3 (~September 2024) and named the 0.3 contents correctly (Pydantic v1 dropped, minimum Python raised, integrations split into `langchain-community` and partner packages). It described 1.0 as a name it has heard and cannot describe. That reproduces `langchain/v1` exactly: 0.3.0 (2024-09-13), first undescribable 1.0.0 (2025-10-17).",
      "api": null,
      "introduced_in": "0.3.0",
      "why_not_a_finding": "The datum here is the boundary, not a code failure; and an accurate account of 0.3 is not itself a stale prior."
    },
    {
      "kind": "context",
      "summary": "Tasks 1-11 produced code but no charged findings, per the v1r pre-registration. This draw reproduced the v1 stack closely: `langgraph.prebuilt.create_react_agent` with `prompt=` (tasks 2, 3), `pre_model_hook=` (task 9), `from langchain import hub` (task 6), and a `MemorySaver` checkpointer (task 5) -- the same 0.3-era shape `langchain/v1` charged. It diverged from v1 on task 10, filtering `astream_events` on `on_chat_model_stream` rather than on the `\"agent\"` node, so v1's designed S2 (the stream filter that silently matches nothing after the node rename) did not reproduce in this draw.",
      "api": null,
      "introduced_in": null,
      "why_not_a_finding": "Pre-registered: a replicate does not re-charge what the original run already charged. The task-10 divergence is reported rather than scored."
    }
  ],
  "open_questions": [
    {
      "question": "See `langchain--claude-sonnet-5--v1r-a--2026-09-01`. This draw agrees with `langchain/v1`; its twin does not, and both were given a byte-identical prompt on the same day.",
      "status": "open"
    },
    {
      "question": "Task 10 did not reproduce v1's S2 stream-filter failure. One divergence in one task is not enough to say whether findings are as unstable as boundaries, and a code-level reproducibility check has never been run.",
      "status": "open"
    }
  ],
  "summary": "Replicate B of `langchain/v1` against Sonnet 5, prompt unchanged. It reproduced `langchain/v1` exactly — boundary at 0.3 (2024-09-13), 1.0 known only as a name it cannot describe — and rewrote the same 0.3-era stack: `langgraph.prebuilt.create_react_agent` with `prompt=`, `pre_model_hook=`, `from langchain import hub`. Taken alone this run says the instrument is fine. Taken with its concurrent twin `v1r-a`, which placed the same model's boundary thirteen months later on the same prompt, it says the opposite: the boundary is a draw, not a measurement. One code-level divergence from v1 is also recorded — task 10's stream filter, v1's designed S2, did not reproduce here."
}