## Outcome
- `codex-gpt-6-1-sol` (harness `codex`, model `gpt-6.1-sol`, vendor `openai`, effort `low`, read-only) becomes the reviewer-cli primary.
- `codex-gpt-5-6-sol` stays admitted as the last fallback. It is not deleted.
- The Pi different-vendor fallback stays in the middle. It must remain a non-OpenAI vendor.
- Final reviewer-cli roster:
  1. `codex-gpt-6-1-sol`, low
  2. `pi-qwen3-8-flash-openrouter`, low
  3. `codex-gpt-5-6-sol`, low
- The architecture reviewer, writer and planner rosters do not change.
- GPT-6.1 Sol does not go onto `reviewer-arch`.

## Files
- Model inventory entry for `gpt-6.1-sol` (schema `kxm.model.v2`). It must exist before admission, and the selector is `openai/gpt-6.1-sol`.
- `.kxm/routes.yaml` (schema `kxm.routes.v2`): admit the `codex-gpt-6-1-sol` route using `kxm routes admit`. Don't hand-edit if the command can do it.
- `.kxm/prices.yaml`:
  - Add the price row for `gpt-6.1-sol`.
  - Use the list prices from the packet: $2 input and $10 output per 1M tokens through 272000 prompt tokens, then $4 and $15. Cache read is $0.10 and cache write is $2.50 on both tiers.
  - Alias the pro id on the same row. Do not add a second model.
  - Update the date and the sha256 pin together.
- Reviewer-cli role definition (roster order and the "required CLI critic" comment).
- Any harness-run script that hardcodes the critic model. Find it with a search for `gpt-5.6-sol` and `codex-gpt-5-6-sol`, then read the role roster instead of a literal if the script allows it.
- Roster policy tests.

## Tests
- Roster policy test:
  - Primary is `codex-gpt-6-1-sol`.
  - The read-only permission is unchanged.
  - Effort is `low`.
  - Roster order is as above.
  - A different-vendor Pi fallback is still present.
  - `codex-gpt-5-6-sol` is still admitted as the last fallback.
- Test that `reviewer-arch` contains no `gpt-6.1-sol` route, and that `claude-fable` is still its primary.
- Admission brakes:
  - `kxm routes admit` is refused when the model is absent from inventory.
  - `openai-codex` Pi provider routes and `openrouter/openai/gpt-6.1-sol` are refused by the native-vendor brake.
  - The pro mode is not accepted as a role effort value.
- Prices:
  - A hash mismatch is refused.
  - The pro alias resolves to the same row.
  - The tier boundary at 272000 prompt tokens prices correctly.
- Cost basis:
  - ChatGPT auth records `unmetered` with `priceRef` `subscription:codex`.
  - API-key auth records `unknown`.
- Codex one-shot command shape: `codex exec --json` with a mandatory effort, rejecting an empty or invalid value.
- Docs lint and the version check. Finish with `npm run verify`.

## Docs
Update these in the same change:
- `AGENTS.md` role table
- `docs/reference/harness-routing.md`
- `docs/reference/config-reference.md`
- `docs/reference/cli-reference.md`
- `docs/contributing/assignment-runner.md`
- `docs/contributing/harness-routing-internals.md`
- `CHANGELOG.md`
- The `plans/implementation-plan.md` Tracking section (Decided entry for the admission, and the new primary)

Wording must keep the rule that both critics are required for acceptance and a single critic is triage only.

## Risks and guards
- Billing through Pi or OpenRouter is refused. Keep the native-vendor brake and add the tests above.
- A stale price hash must fail the loader. Never edit the row without re-pinning.
- Pro is a reasoning mode, not a model and not a role effort. Refuse `pro` as an effort and refuse a separate pro route in the codex ceiling.
- The codex ceiling is reviewer-cli only. Do not widen it.
- An API-key login must not be recorded as unmetered.
- Don't leave stale `gpt-5.6-sol` literals in scripts or docs that call it the primary.
- Don't create dual naming or compatibility aliases for the old route.
- Refuse to add a harness preferences overlay.
- Refuse to drop or weaken the architecture critic.

## Sequence
1. Confirm `gpt-6.1-sol` is in inventory. If it isn't, refresh the inventory through the supported updater.
2. Add the price row and alias, then re-pin the hash.
3. Run `kxm routes admit` for the new route.
4. Reorder the reviewer-cli roster.
5. Update scripts that hardcode the critic.
6. Write the tests first or alongside, and confirm they fail against the old roster.
7. Update the docs, CHANGELOG and Tracking.
8. Run `npm run verify`.
9. Run the fixed witness, then get both critic PASS records before acceptance.

## Non-goals
- No change to the writer, planner or `reviewer-arch` rosters.
- No pro architecture-review route.
- No Pi or OpenRouter OpenAI route.
- No effort change above `low` for this role.
- No overlay, and no new schema fields.
- No hosting or provider migration.

## Open questions
- Is the `gpt-6.1-sol` inventory entry already present, and which updater supplies it?
- Does the Pi fallback stay second in the roster, or should the order between the Pi fallback and `codex-gpt-5-6-sol` be flipped? I assumed the Pi fallback stays second.
- Are the packet's list prices complete enough to pin, or does the price feed need a dated source?
- Which harness-run scripts hardcode the critic? The packet doesn't name them.
- Is the model's comment text ("required CLI critic") carried over verbatim to the new primary?