v1.67.2.0 feat: gpt-5.6-sol bounded-scope profile for Codex installs (#2633)

* feat: model taxonomy gains gpt-5.6-sol + per-host generation defaults

Adds 'gpt-5.6-sol' to the model taxonomy with exact-match-only resolution
(Terra/Luna/suffixed IDs deliberately fall back to generic gpt) and replaces
the hardcoded 'claude' generation default with a validated
HostConfig.defaultModel: codex renders the gpt profile when --model is
absent, every other host keeps claude. Codex ship golden regenerated
accordingly; ADDING_A_HOST documents the new field.

* feat: gpt-5.6-sol bounded-scope overlay + scope-aware resolvers

The Sol profile pins the explicit task as the lake: adjacent work is
report-only, investigation is bounded, runs terminate on one clean
verification pass, and the AskUserQuestion decision-brief format is never
trimmed. The overlay wrapper grants scope-interpretation precedence while
concrete workflow steps, gates, and skill-mandated re-verification loops
still win. Sol-specific Completeness Principle and first-run intro copy.
New SETUP_COMMAND resolver renders './setup --host <host>' for every
non-claude host so generated upgrade skills reinstall their own host.

* feat: setup reads the Codex model from config.toml

New resolve-codex-generation-model.ts reads the top-level model from
${CODEX_HOME:-~/.codex}/config.toml, validates against the model allowlist,
strips control characters from every config-derived string it surfaces,
guards against non-absolute config locations, and warns on Sol near-misses.
setup runs it on EVERY invocation (read-only TOML lookup) so a plain
./setup can never clobber a Sol user's rendered profile with the hardcoded
fallback; --model <id> overrides for one run and prints the persistence
hint. Kiro installs render the claude profile before copying (Kiro fronts
Claude-family models), rewrite the baked setup command to --host kiro, and
restore the resolved Codex profile after; the codex skills path honors
CODEX_HOME. Static pins cover the resolver wiring, fail-closed exit,
quoted argv, and the Kiro sandwich.

* feat: hermetic Codex runner hardening + Sol scope-termination E2E

The Codex E2E runner copies auth.json only (operator plugins, MCP servers,
rules, and skills no longer leak into hermetic evals), pins CODEX_HOME to
the temp dir, and supports per-run model, TOML overrides, and
--ignore-user-config. New periodic E2E installs the FULL generated
investigate skill on gpt-5.6-sol against a planted one-line bug with decoy
TODOs: the fix must land inside the boundary (untracked files counted via
git status --porcelain), decoys stay byte-identical, the regression oracle
survives unweakened, nothing gets committed, all within 30 tool calls.
The shared .agents tree is snapshotted and restored exactly in beforeAll;
fixture commits disable gpg signing. Wired into the periodic CI matrix,
paid-shard globs, eval scripts, touchfiles/E2E_TIERS
(codex-sol-scope-termination), and diff-based selection. Real-file
periodic-tier classification pins both codex E2Es out of the gate tier.
Free-tier test proves an explicit --model overrides the host default
through the real generation CLI.

* chore: bump version and changelog (v1.67.2.0)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs: post-ship documentation sync for v1.67.2.0

- README: Codex skills path is CODEX_HOME-aware; state that
  --model overrides detection for one run only (persist via
  the Codex config.toml model key)
- CONTRIBUTING: add the model-overlay axis to the per-host
  config table (per-host defaultModel, override precedence)
- CLAUDE.md: eval results dir is ~/.gstack/projects/<slug>/evals/
  (legacy fallback ~/.gstack-dev/evals/), matching eval-store.ts
  and the eval:* CLI headers

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs: post-ship documentation sync (v1.67.2.0)

Sol exact-match and near-miss warning documented in README; CODEX_HOME-aware
uninstall and troubleshooting paths; hermetic auth.json-only detail and the
build-clobber gotcha in CLAUDE.md; eval-store location corrected in
ARCHITECTURE.md; defaultModel row in the ADDING_A_HOST field reference;
resolver test count corrected in the CHANGELOG entry.

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,53 @@
 # Changelog
 
+## [1.67.2.0] - 2026-08-18
+
+**Codex installs now match the model you actually run.**
+**gpt-5.6-sol gets a bounded-scope profile that finishes the job, then stops.**
+
+Every gstack skill carries a model-specific behavioral patch. This release makes that patch model-aware for Codex: `./setup --host codex` reads the top-level `model` from `${CODEX_HOME:-~/.codex}/config.toml` and renders the matching profile. The headline is `gpt-5.6-sol`. Sol reads completeness language like "exhaustive" and "Boil the Ocean" as authority to keep going, widening into adjacent cleanup and speculative hardening nobody asked for. Its new profile pins the boundary: the explicit task is the lake, adjacent findings are report-only, investigation stops once the cause is established, and the run terminates on one clean verification pass. Full coverage inside the boundary still applies, and the AskUserQuestion decision-brief format is never trimmed.
+
+Sol is exact-match only. Terra, Luna, dated snapshots, and any suffixed ID deliberately fall back to the generic GPT profile, and the resolver warns when a near-miss like `gpt-5.6-sol-2026-08-01` lands on generic gpt.
+
+### The numbers that matter
+
+Source: the new periodic scope-termination eval (`EVALS=1 EVALS_TIER=periodic bun test test/codex-e2e-sol-scope.test.ts`, result in `~/.gstack/projects/<slug>/evals/`) and the free suite (`bun run test`).
+
+| Metric | Before | After |
+|---|---|---|
+| Codex skill overlay | one fixed profile for every install | matched to `config.toml`, `--model` per-run override |
+| Sol on a planted one-line bug (live eval) | no measurement | fixed in 21 tool calls, 173s, both decoy TODOs byte-identical |
+| Scope check in that eval | not measured | untracked, staged, and unstaged files all counted |
+| Hermetic Codex E2E environment | whole operator `~/.codex` tree copied in | `auth.json` only, `CODEX_HOME` pinned |
+| Kiro skill profile | inherited whatever the shared render held | always the claude profile, rebuilt at install time |
+| Upgrade skill reinstall target | bare `./setup` (claude) for every host | the host it was generated for |
+
+The eval row is the one to internalize: the same investigate skill that tells Claude to boil the ocean drives Sol to fix exactly one function, run the one targeted test, and stop with two tempting decoy TODOs untouched.
+
+### What this means for Codex users
+
+If you run Codex on `gpt-5.6-sol`, rerun `./setup --host codex` once. Your skills keep the full gstack workflow (STOP points, review gates, decision briefs) but stop sprawling into work you did not ask for. Change your Codex model later, rerun setup, and the profile follows. `--model <id>` overrides detection for one run and tells you how to make it stick.
+
+### Itemized changes
+
+#### Added
+- `gpt-5.6-sol` model profile (`model-overlays/gpt-5.6-sol.md`): explicit task boundary, report-only adjacent work, bounded investigation, terminate on verified completion, AskUserQuestion format preserved in full.
+- Codex model detection at setup: new `scripts/resolve-codex-generation-model.ts` reads the top-level `model` from `${CODEX_HOME:-~/.codex}/config.toml`, validates against the model allowlist, treats config values as data (control characters stripped from every surfaced string, absolute-path guard on the config location), and falls back to the generic GPT profile with a warning on unreadable or unsupported configs. `./setup --host codex --model <id>` overrides for that run.
+- Per-host generation defaults: `HostConfig.defaultModel`, validated at generation time. Codex renders the GPT profile when no `--model` is passed; every other host keeps claude. `docs/ADDING_A_HOST.md` documents the new field.
+- Periodic scope-termination E2E (`test/codex-e2e-sol-scope.test.ts`): installs the FULL generated investigate skill, plants a one-line bug beside decoy security and migration TODOs, and asserts the fix lands inside the boundary within 30 tool calls, the decoys stay byte-identical, the regression oracle survives unweakened, and nothing gets committed. Wired into the periodic eval matrix, the paid-shard globs, and diff-based selection (`codex-sol-scope-termination`).
+- Sol-specific Completeness Principle and first-run intro copy: Boil the Ocean within the user's explicit task boundary.
+
+#### Changed
+- Generated upgrade skills reinstall their own host: `./setup --host codex` in Codex renders, `--host kiro` in Kiro copies (rewritten at copy time), bare `./setup` only for Claude.
+- Kiro installs render the claude profile before copying skills, then restore the resolved Codex profile, so Kiro never ships GPT-family behavioral text and live `~/.codex` symlinks stay correct. The Codex skills path honors `$CODEX_HOME`.
+- The hermetic Codex E2E runner copies `auth.json` only. Operator plugins, MCP servers, rules, and skills no longer leak into supposedly hermetic evals. Per-run `model`, TOML config overrides, and `--ignore-user-config` are supported.
+- `setup` resolves the Codex generation model on every run (a read-only TOML lookup), so any install path preserves a Sol user's rendered profile; the codex install summary prints the active profile and its source.
+
+#### For contributors
+- New free-tier coverage: every resolver branch including hostile-config shapes (10 tests), overlay content pins, the explicit `--model` override through the real generation CLI, real-file periodic-tier classification for both codex E2E files, and invalid `defaultModel` validation.
+- Static pins in `test/setup-codex-model.test.ts` hold the load-bearing setup properties: unconditional resolver, quoted `--explicit` argv, fail-closed empty-resolver exit, the Kiro claude-render sandwich, and the `--host kiro` rewrite.
+- The Sol E2E snapshots the exact prior `.agents` render and restores it in `beforeAll`, so the shared tree never stays Sol-flavored for goldens, parallel shards, or symlinked installs. Fixture commits disable gpg signing so the eval runs under any global git config.
+
 ## [1.67.1.0] - 2026-08-16
 
 **We read every line of external-contributor code from the last two months.**