fastmcp-slim 4.1.3

Source: https://github.com/PrefectHQ/fastmcp
Tag scanned: v4.1.3
Directory: fastmcp_slim (only this part of the repository was scanned)
Compared with: v4.1.2 (0 signals introduced since)
Files: 276 scanned, 3 skipped (binary, oversized, or unrecognised)
Signals: 0 critical · 0 warn · 1 info
Scan time: 3.2 s
LLM review: Reviewed by claude-haiku-5-5 (Anthropic): 1 of 1 warn and critical signal; 1 demoted to info.
Disclude version: 4.0.0
Scanned (UTC): 2026-10-21 10:40

Signals

Ordered by severity, then signals introduced in this release. Hidden characters are shown as ⟨U+…⟩.

info ~~warn~~ → info by review frame-introspection fastmcp_slim/fastmcp/client/transports/inference.py:41:13

`sys._getframe` — call-stack frame introspection (ast pass, confidence 0.70)
```
    level = 1
    frame = sys._getframe(1)
    while frame is not None:
        if not frame.f_code.co_filename.startswith(_PACKAGE_ROOT):
```
likely benign LLM, confidence 0.90 Walks the call stack via sys._getframe to find the first frame outside the fastmcp package, likely to infer the caller's context.
Reasoning
sys._getframe(1) combined with walking frames and comparing co_filename against the package root is a standard pattern for locating the first caller outside the package, used for inferring the calling module in a transport. No evidence of evasion, exfiltration, or dynamic execution of obtained data. The finding is an AST signal on a common introspection call, which is legitimate here.

Reproduce This Scan

Run disclude locally to verify. Add --format sarif for SARIF output. Add --llm (with an API key in the environment) to include the LLM review.

cargo install disclude --version 4.0.0
git clone https://github.com/PrefectHQ/fastmcp fastmcp && cd fastmcp
git checkout v4.1.3
disclude scan --severity info --diff v4.1.2 fastmcp_slim