Jean-Pierre

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Define deny-preserving access.env matching on case-insensitive platforms ​

  • Status: Todo
  • Kind: Chore
  • Authors: jp
  • Date: 2026-09-05
  • Implements: 076
  • Label: package=jp_tool
  • Label: type=question

EnvRule::matches is case-sensitive on every platform. That keeps a rule set meaning the same thing wherever it is read, but it does not preserve a deny where the OS resolves variable names case-insensitively.

Given this policy:

toml
[[conversation.tools.my_tool.access.env]]
name = "*"
read = true

[[conversation.tools.my_tool.access.env]]
name = "GITHUB_TOKEN"
read = false

a request for github_token misses the exact deny ("github_token" != "GITHUB_TOKEN"), selects the * grant, and then resolves through std::env::var to the same OS variable on Windows. On Unix the same request usually finds nothing. Same config, same request, different outcome per platform — the opposite of what case-sensitive matching is supposed to buy.

Windows is a supported target: .github/workflows/rust.yml runs the suite on windows-latest.

Why it isn't fixed yet ​

There is no in-tree env consumer, so there is no caller to design the rule against, and the obvious half-measures do not work:

  • Canonicalizing only the requested name leaves an exact rule written in another case unmatched.
  • Matching case-insensitively everywhere widens grants on Unix, where foo and FOO are genuinely different variables.

Candidates ​

  • Canonicalize the requested name and every rule name to one form, on platforms where the OS is case-insensitive.
  • Match denies case-insensitively while keeping grants exact, so the strict direction always wins.

Recorded as an open question in RFD 076's env-rules section. Settle it alongside the first consumer, and pin it with a case-variant test then.