ProvelyAdd two lines and nothing else. Provely finds LangChain by itself and loads its plugin when the agent starts. You write no guard call and import no adapter.
import { Provely } from '@provely/sdk';
new Provely();
from provely import Provely
Provely()
Provely attaches to the model calls and the tool calls of every LangChain agent. The API key is required, and the SDK reads it from PROVELY_API_KEY. Get your API key: sign in at app.provely.sh/account/api-keys, open API keys, and create a key. The dashboard shows the key once. Keep it in an environment variable, never in code.
Which LangChain packages does Provely find?
Provely finds langchain (TypeScript) and langchain (Python). The plugin loads only when the package is present, so the core holds no framework code.
What did the grid measure for LangChain?
The grid runs each failure case against a real app with the two lines, and again with no Provely line. The table states the column that holds the LangChain paths.
| Column | Paths | Pass | Fail | Not counted | Not applicable | Head |
|---|---|---|---|---|---|---|
| TypeScript frameworks | LangChain (and 6 paths in all) | 27 of 27 (1 passes under guard_mode: enforce; observe records only; rules cases not yet measured) | 0 | 0 | 0 | 82acaae6 |
| Python frameworks | LangChain (and 4 paths in all) | 26 of 27 (1 passes under guard_mode: enforce; observe records only; rules cases counted apart) | 1 | 0 | 0 | 9f9131ba |
A fail is a case that did not pass on at least one path. "Not counted" is a case where the framework coped alone and Provely made no fix, so it is not a pass. An inapplicable case is left out of the total.
The invented-value case passes under guard_mode: enforce; observe records only. Under observe, the default, Provely records the value and the write runs.
Measured on 2026-10-17 at commit 82acaae6. Measured on 2026-10-17 at commit 9f9131ba.
Source: tests/zero-code grid · retrieved 2026-10-17
What does Provely do when a call fails?
One deterministic check answers each failure, and it makes one of five actions.
| Action | Code | What happens |
|---|---|---|
| Repair in place | repair_in_place | A lossless syntax fix, for example single quotes or a code fence around the JSON. The tool gets the arguments that the model meant. |
| Return the exact error | return_error_to_model | The model gets one exact sentence about what is wrong, and it tries again. The tool does not run. |
| Retry | retry | Only where the frozen retry table permits it, and always with the key of the first attempt. |
| Refuse | refuse | The call never reaches the tool. Examples: a duplicate call, or a write that repeats a completed write in the same agent call. |
| Record | record | The call runs, and the line states what the check found. |
Every fix writes one decision-log line. The line holds ids and codes only, never a value. No language model takes part in any decision.
Your own defences stay. Read how Provely works beside them.