# Adversarial Codex-agent TOML Fixtures (#3242)

Reusable hostile inputs for `gsd-core/bin/lib/agent-install-check.cjs`
`checkCodexModelPosture()`.

Per CONTRIBUTING's fixture-provenance rule (#2371), these files are
**hand-authored against the real Codex `.toml` shape** (the header-field /
`developer_instructions = '''...'''` layout `generateCodexAgentToml` in
`bin/install.js` emits) — none of them were produced by calling that
writer. A fixture generated by the gate's own emitter can only confirm
what the emitter already believes about its own output; it cannot surface
a shape the emitter's author didn't anticipate.

Tests load them by relative path from
`tests/agent-install-check.test.cjs` so the corpus can grow without
touching the writer.

Categories present:

- `model-in-developer-instructions.toml` — the headline trap. Contains a
  literal `model = "sonnet"` line *inside* the `developer_instructions`
  triple-quoted block, with no `model` key in the header. A whole-file
  line-oriented scan (`/^model\s*=/m` over the entire document) reports a
  false `ANTHROPIC_FLAVORED_MODEL` violation here; the correct
  header-slice scan reports none.
- `commented-model-pin.toml` — `# model = "sonnet"` in the header region.
  Must not be treated as a live pin.
- `model-verbosity-prefix-collision.toml` — only `model_verbosity = "low"`
  is present, no `model` key. A key-prefix probe (`/model/`) would
  misfire on this; a full-key-name anchor does not.
- `whitespace-indented-model-pin.toml` — `  model   =  "sonnet"` (leading
  indentation, spaced `=`). This one **is** a violation — whitespace
  around a real key must still be recognized.
- CRLF has no committed fixture: `.gitattributes` (`* text=auto eol=lf`,
  repo-wide) normalizes any `\r\n` file back to LF on commit and on every
  checkout, so a committed CRLF fixture would silently prove nothing. The
  CRLF case (row 18a in `tests/agent-install-check.test.cjs`) instead
  authors LF content inline and converts it with `.replace(/\n/g, '\r\n')`
  at test runtime, keeping the CRLF-ness under the test's control.
- `bom-pinned-model.toml` — UTF-8 BOM (`EF BB BF`) prefix, then a header
  pinning `model = "sonnet"`. Must be flagged identically to a
  BOM-free file.