fix: default cross-model workflows to frontier models

review/sections/adversarial.md

@@ -56,7 +56,7 @@ Branch on the echoed `CODEX_MODE`:
 - **`under_codex`** — this session is already running INSIDE a Codex host, so spawning codex again is the same model reviewing itself at multiplied token cost (#2519). Print exactly one line: "[running under Codex — nested codex passes skipped; set GSTACK_FORCE_CODEX_REVIEW=1 to force]" and skip the codex invocations below; run the section's free in-host pass instead if it defines one.
 - **`not_authed`** — installed but no credentials. Print: "Codex installed but not authenticated — falling back to a Claude subagent (same model family, not an outside model). Run `codex login` or set `$CODEX_API_KEY`." Fall back to the Claude subagent path.
 - **`broken_install`** — the CLI is on PATH but cannot execute (spawn ENOENT, non-executable binary, missing vendor payload). Print: "Codex is installed but its binary cannot run — Codex passes skipped. Reinstall: `npm install -g @openai/codex`." Relay the probe's HINT lines and fall back to the Claude subagent path. This state exists because a missing binary used to land in the model probe's fail-open bucket and report `ready`, so every Codex pass was skipped silently (#2742).
-- **`model_unusable`** — authed but the account cannot use its configured model (#2477: HTTP 400 on every call, usually a stale `model =` pin in `~/.codex/config.toml`). Relay the probe's HINT lines, tell the user the one-line fix (update the pin; `[notice.model_migrations]` names the replacement), and fall back to the Claude subagent path. The ~10s round trip is cached for 1h; timeouts fail open to `ready`.
+- **`model_unusable`** — authed but the account cannot use gstack's selected Codex model (#2477: HTTP 400 on every call). Relay the probe's HINT lines, tell the user the one-line fix (set `GSTACK_CODEX_MODEL=<supported-model>` or pass an explicit `-c model=...` override), and fall back to the Claude subagent path. The ~10s round trip is cached for 1h; timeouts fail open to `ready`.
 - **`ready`** — run the Codex pass below.
 
 For this diff-review path, `CODEX_MODE: disabled` means skip the Codex passes ONLY — the
@@ -96,7 +96,7 @@ _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo"
 # here. It defines _gstack_codex_timeout_wrapper (gtimeout -> timeout ->
 # unwrapped fallback), added in #1056 but never wired into this call site.
 source ~/.claude/skills/gstack/bin/gstack-codex-probe 2>/dev/null || true
-_gstack_codex_timeout_wrapper 540 codex exec "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. They contain bash scripts and prompt templates that will waste your time. Ignore them completely. Do NOT modify agents/openai.yaml. Stay focused on the repository code only.\n\nReview the changes on this branch against the base branch. Run DIFF_BASE=$(git merge-base origin/<base> HEAD) && git diff "$DIFF_BASE" to see the diff. Your job is to find ways this code will fail in production. Think like an attacker and a chaos engineer. Find edge cases, race conditions, security holes, resource leaks, failure modes, and silent data corruption paths. Be adversarial. Be thorough. No compliments — just the problems. End your output with ONE line in the canonical format `Recommendation: <action> because <one-line reason naming the most exploitable finding>`. Generic reasons like 'because it's safer' do not qualify; the reason must point to a specific finding or no-fix rationale." -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR_ADV"
+_gstack_codex_timeout_wrapper 540 codex exec "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. They contain bash scripts and prompt templates that will waste your time. Ignore them completely. Do NOT modify agents/openai.yaml. Stay focused on the repository code only.\n\nReview the changes on this branch against the base branch. Run DIFF_BASE=$(git merge-base origin/<base> HEAD) && git diff "$DIFF_BASE" to see the diff. Your job is to find ways this code will fail in production. Think like an attacker and a chaos engineer. Find edge cases, race conditions, security holes, resource leaks, failure modes, and silent data corruption paths. Be adversarial. Be thorough. No compliments — just the problems. End your output with ONE line in the canonical format `Recommendation: <action> because <one-line reason naming the most exploitable finding>`. Generic reasons like 'because it's safer' do not qualify; the reason must point to a specific finding or no-fix rationale." -C "$_REPO_ROOT" -s read-only -c "model=\"${GSTACK_CODEX_MODEL:-gpt-6-astra}\"" -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR_ADV"
 ```
 
 Set the Bash tool's `timeout` parameter to `600000` (10 minutes). It sits ABOVE the 540s wrapper deliberately, so the wrapper fires first and a stall surfaces as a diagnosable exit 124 instead of a harness kill that returns nothing. The wrapper resolves `gtimeout`, then `timeout`, then runs unwrapped, so it is safe on a macOS without coreutils. After the command completes, read stderr:
@@ -129,7 +129,7 @@ cd "$_REPO_ROOT"
 # here. It defines _gstack_codex_timeout_wrapper (gtimeout -> timeout ->
 # unwrapped fallback), added in #1056 but never wired into this call site.
 source ~/.claude/skills/gstack/bin/gstack-codex-probe 2>/dev/null || true
-_gstack_codex_timeout_wrapper 540 codex review --base <base> -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR"
+_gstack_codex_timeout_wrapper 540 codex review --base <base> -c "model=\"${GSTACK_CODEX_MODEL:-gpt-6-astra}\"" -c "review_model=\"${GSTACK_CODEX_MODEL:-gpt-6-astra}\"" -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR"
 ```
 
 **No prompt argument.** `--base` is what scopes the review, and the positional `[PROMPT]` is mutually exclusive with it — passing both fails at argv parsing. Do NOT "fix" that error by dropping `--base` and keeping the prompt: a prompt-only `codex review` silently falls back to the **uncommitted working-tree** scope (`git status --short; git diff`), so it reviews the wrong changes and reports "no changes" on a clean tree. Prompt text describing the diff range does not change what the CLI feeds the reviewer. Unlike the adversarial pass above, which uses `codex exec` and really does run the git command it's told to, this path gets a pre-computed diff from the CLI — which is also why it needs no filesystem boundary.