## Outcome
Replace writer #2 `pi-qwen3-coder-plus-openrouter` with `pi-qwen3-coder-next-openrouter` (model `openrouter/qwen/qwen3-coder-next`, vendor alibaba, permission edit, harness pi). Writer #1 and #3–#6 stay in their current order. The old route is retired, not deleted.

**Why qwen3-coder-next:**
- It is a Qwen model, so the OpenRouter route is allowed. Qwen has no native harness.
- It is the closest successor to a coder-specialised model.
- At 0.12 / 0.80 it is the cheapest candidate.
- It has a flat price, so there is no long-context premium like qwen3.7-plus's 0.96 / 3.84 tier at 256000 tokens and above.
- Its 262144 context is smaller than the alternatives. That is acceptable for edit-sized writer prompts.

**Tool-support assumption (labeled):** the packet does not show `supported_parameters`. I assume `qwen3-coder-next` supports tools because it is a coder model. The writer must verify this against the live OpenRouter models API before admitting the route (see Risks and guards).

**Fallback if tool support is not shown:** `qwen/qwen3.7-plus` is the second choice. It would need the same check, and the premium tier must be recorded.

## Files
- `.kxm/models/pi-qwen3-coder-next-openrouter.yaml`: schema `kxm.model.v2`, harness pi, vendor alibaba, permissions include edit. Add alias `qwen-next-openrouter-pi`.
- Model inventory file: add the new id. This must come before the routes change.
- Routes file: add the new route as admitted. Mark `pi-qwen3-coder-plus-openrouter` retired in a comment, remove it from the admitted list, and remove it from the writer roster so #2 is the new route. Keep the old alias out of the active lists.
- Inventory: keep the old id with a retired comment. Do not reuse its alias.
- `.kxm/prices.yaml`: add the `qwen/qwen3-coder-next` row at 0.12 / 0.80. Keep the `qwen/qwen3-coder-plus` row at its last list price. Update the date and sha256 together.
- Writer roster definition (assignment runner): swap #2 only.
- `plans/evidence/<date>-writer-2-qwen3-coder-next.md`: evidence note.

## Tests
- Roster-policy tests: update the hardcoded #2 id. Assert that #1 and #3–#6 are unchanged and in order (Argon high, Argon medium, Flash medium, Flash high).
- Add a test that the retired route is not admitted and not on the roster.
- Add a test that the new id exists in inventory before routes admit it. This should fail if the order is wrong.
- Prices loader test: the sha256 and date match, and the old row is still present.
- Brake test: no `moonshotai/*` route through Pi/OpenRouter.
- Model file schema test: `kxm.model.v2`, vendor alibaba, edit permission.
- Run `npm run verify`.

## Docs
Update every place that names writer #2 or `qwen3-coder-plus`:
- harness-routing
- config reference
- CLI reference
- assignment runner doc
- glossary, only if it names the route
- changelog
- `plans/implementation-plan.md` Tracking (Decided and the relevant slice)
- generated `dist`, only if a grep shows the string embedded. If it is, regenerate rather than hand-edit.

Do not rewrite historical evidence or changelog entries that describe the old route as it was.

## Risks and guards
- **Tool support is unproven in the packet.** Before admission, the writer must check `supported_parameters` for tools in the live models API. If it is absent, do not admit. Fall back to the next candidate that shows tools, or leave #2 vacant with the gap recorded. Never admit on assumption alone.
- **Moonshot `kimi-k2.7-code` is refused.** Moonshot has a native kimi harness, and billing a native vendor through Pi/OpenRouter is the brake case. It is the only candidate that falls under the brake.
- **Meta `muse-spark-open` is not auto-admitted.** It is an admission question, and it is also the most expensive per token.
- **Price pin:** the loader refuses a date or sha256 mismatch. Update both in the same commit and recompute the hash after the final edit.
- **Order dependency:** inventory must contain the id before routes admit it.
- **404 risk repeats:** record the verification date, 2026-10-17, in the evidence note.
- **No dual names or alias for the retired route.** Old names fail closed.

## Sequence
1. Verify `qwen3-coder-next` live and tool-capable. Record the result in the evidence note.
2. Add the model file.
3. Add the inventory entry, with the retired comment on the old id.
4. Add the prices row, then update the date and recompute the sha256.
5. Update routes: admit the new route, retire the old one, update the roster.
6. Update the tests.
7. Update the docs, changelog and Tracking.
8. Regenerate `dist` if needed.
9. Run `npm run verify`.

## Non-goals
- Do not change writer #1, the planner, `reviewer-cli`, or `reviewer-arch`.
- Do not reorder Argon or Flash.
- Do not add a harness preferences overlay.
- Do not delete the old price row.
- Do not add a compatibility alias.
- Do not run a side-by-side model comparison.

## Open questions
- Does `qwen/qwen3-coder-next` list tool support? The packet does not show `supported_parameters` for any candidate.
- What is the exact evidence-note filename convention, and where do the inventory and routes files live?
- What is the last list price of `qwen3-coder-plus`? It is not in the packet, so keep the row as it is.
- Does effort stay medium for the new route? I assume yes.
- Is a 262144 context enough for assignment prompts? This is unmeasured.