What xAI Grok Build CLI actually sends to xAI - a wire-level analysis (grok 0.2.93) · GitHub

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cereblab/grok-build-cli-wire-analysis.md

Created<br>July 10, 2026 02:13

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What xAI Grok Build CLI actually sends to xAI - a wire-level analysis (grok 0.2.93)

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grok-build-cli-wire-analysis.md

What xAI's Grok Build CLI Actually Sends to xAI: A Wire-Level Analysis

A measured, reproducible teardown. Findings are backed by captured artifacts (endpoint, HTTP method, status code, byte size, host) and repro commands; where an observation was seen live but not retained as a file, §7 says so explicitly. Section 8 is an evidence appendix with SHA-256s and a "what we did not prove" list. All captures are of my own traffic on my own machine, using a throwaway repository containing fake "canary" secrets — no real credentials were exposed.

0. Summary

xAI's official Grok Build coding CLI (grok), on a normal consumer login, does three things worth documenting precisely:

It transmits the contents of files it reads — including a .env secrets file — to xAI, verbatim and unredacted. The secret appears in two channels: the live model turn (POST /v1/responses) and a session_state archive uploaded and accepted (HTTP 200) via POST /v1/storage — the endpoint the binary routes to the grok-code-session-traces GCS bucket (see §5).

It uploads the whole repository — every tracked file's content plus git history — independent of what the agent reads. Grok packages the workspace and uploads it via POST /v1/storage. Proven directly: on a real codebase, with the prompt "reply OK, do not read any files", Grok uploaded the entire repo as a git bundle (POST /v1/storage → 200); git clone-ing the captured bundle recovers a file the agent was told not to open — src/_probe/never_read_canary.txt — with its unique marker verbatim , plus the full git history (appendix uploaded_repo.bundle). And it scales: on a 12 GB repo of never-read random files, /v1/storage moved 5.10 GiB, all HTTP 200 (truncated mid-stream), while the model-turn channel moved just 192 KB — a ~27,800× ratio that pins the upload to the codebase, not to what was read. No storage upload failed; the only non-200s were a model-usage quota (402/429) on /v1/responses and one unrelated 404 — not a storage size cap.

The storage destination is a Google Cloud Storage bucket, grok-code-session-traces (not AWS S3) — named verbatim in the binary and in a captured metadata.json (gs://grok-code-session-traces/…). I did not find this mechanism surfaced in the CLI's install/quickstart materials (not an exhaustive docs audit — §7), it is active by default, and disabling "Improve the model" does not turn it off (/v1/settings still returned trace_upload_enabled: true; §6).

None of this proves xAI trains on the data — that is a policy question addressed in §6. What is proven is transmission, acceptance, and storage.

1. Subject under test (provenance)

Install: curl...