DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.
CLAUDE_CODE_SKILL_PROPOSALS and CLAUDE_CODE_EVAL_INTERVIEW_SESSION joined the list of Claude-owned variables handled when Claude Code builds the environment for a subprocess, with the former also added to the shorter second list next to CLAUDE_CODE_COWORK_FRAME_ARTIFACTS.
Evidence
CLAUDE_CODE_EVAL_INTERVIEW_SESSION
Strings lifted out of the shipped bundle, so the claim above can be checked against them.