Codex Exec Contract

examples/contract-codex-exec.toml delegates the inner solve to codex exec. Truss clears API-key environment variables from the child and verifies the result at the same contract boundary as API-backed runs.

truss --contract examples/contract-codex-exec.toml

# OpenAI subscription via the DELEGATED path (ADR 0003, Tier 2) — uses the `codex`
# CLI's own ChatGPT login. No API key, no token replay by Truss; `codex` owns the
# inner loop and Truss verifies the result at the contract boundary.
#
#   truss --contract contract-codex-exec.toml
#
# Compare with `--provider openai-codex` (Tier 1, in-process), which drives Truss's
# OWN loop on the same subscription — better for dev/testing. This delegated path is
# the safer production answer for OpenAI subscriptions.
#
# Prereq: `codex` on PATH and signed in with ChatGPT (`codex` → Sign in).

reviewers = 3

[contract]
id = "demo-greeting-codex-exec-0001"
title = "Write a greeting file (via codex on a ChatGPT subscription)"
intent = """
Create a file named greeting.txt in the working directory whose contents are
exactly the line: hello from the harness
"""

[executor]
kind = "delegated-cli"
command = "codex"
# `codex exec` is the non-interactive, one-shot mode; prompt arrives on stdin.
args = ["exec", "--skip-git-repo-check"]
# Stripped so the CLI uses its stored ChatGPT login, not a key Truss is holding.
clear_env = ["OPENAI_API_KEY", "OPENAI_BASE_URL"]
prompt_via = "stdin"

[[done]]
kind = "check"
desc = "greeting.txt exists and contains the exact line"
run = "cat greeting.txt"
expect_exit = 0
expect_contains = ["hello from the harness"]

[[done]]
kind = "review"
desc = "the greeting reads naturally and matches the intent"

[budget]
max_cost_usd = 1.00
max_steps = 12