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5.3
LangSmith SDK: Unredacted streaming token events stored in LangSmith
Summary
The LangSmith SDK's output redaction feature doesn't work for streaming output, allowing sensitive information to be stored in LangSmith. This means that any data streamed from a Large Language Model (LLM) run, such as text or tokens, may not be properly hidden. To fix this issue, update to a version of the LangSmith SDK that addresses this bug.
What to do
- Update GitHub Actions langsmith to version 0.5.19.
- Update langsmith to version 0.7.31.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| npm | GitHub Actions | langsmith |
< 0.5.19 Fix: upgrade to 0.5.19
|
| PyPI | – | langsmith |
< 0.7.31 Fix: upgrade to 0.7.31
|
Original title
LangSmith SDK: Streaming token events bypass output redaction
Original description
## Summary
The LangSmith SDK's output redaction controls (hideOutputs in JS, hide_outputs in Python) do not apply to streaming token events. When an LLM run produces streaming output, each chunk is recorded as a new_token event containing the raw token value. These events bypass the redaction pipeline entirely — prepareRunCreateOrUpdateInputs (JS) and _hide_run_outputs (Python) only process the inputs and outputs fields on a run, never the events array. As a result, applications relying on output redaction to prevent sensitive LLM output from being stored in LangSmith will still leak the full streamed content via run events.
## Details
**Both JS and Python SDKs are affected.** The same pattern exists in both:
- **JS SDK**: `traceable.ts:997-1003` and `traceable.ts:1044-1050`
- **Python SDK**: `run_helpers.py:1924` and `run_helpers.py:1996`
In both SDKs, `new_token` events with raw `kwargs.token` values are added during streaming, and the redaction pipeline (`hideOutputs` in JS, `hide_outputs` in Python) only processes `inputs`/`outputs` — never `events`.
The LangSmith SDK's output redaction controls (hideOutputs in JS, hide_outputs in Python) do not apply to streaming token events. When an LLM run produces streaming output, each chunk is recorded as a new_token event containing the raw token value. These events bypass the redaction pipeline entirely — prepareRunCreateOrUpdateInputs (JS) and _hide_run_outputs (Python) only process the inputs and outputs fields on a run, never the events array. As a result, applications relying on output redaction to prevent sensitive LLM output from being stored in LangSmith will still leak the full streamed content via run events.
## Details
**Both JS and Python SDKs are affected.** The same pattern exists in both:
- **JS SDK**: `traceable.ts:997-1003` and `traceable.ts:1044-1050`
- **Python SDK**: `run_helpers.py:1924` and `run_helpers.py:1996`
In both SDKs, `new_token` events with raw `kwargs.token` values are added during streaming, and the redaction pipeline (`hideOutputs` in JS, `hide_outputs` in Python) only processes `inputs`/`outputs` — never `events`.
osv CVSS3.1
5.3
Vulnerability type
CWE-200
Information Exposure
CWE-359
CWE-532
Insertion of Sensitive Information into Log File
Published: 16 Apr 2026 · Updated: 16 Apr 2026 · First seen: 16 Apr 2026