Two honest questions replace one ambiguous dropdown

Counsel first records whether the matter is adversarial. Only then, when needed, counsel chooses the represented party label supplied by the selected matter type.

Interaction states

Is there an opposing side?

AdversarialThere is a single opposing side.

AdvisoryNo single opponent.

Lock · Permanent orientation

→

Is there an opposing side?

Adversarial

Who we represent

Claimant

Respondent

Behavior and contract

Choice	UI behavior	Create payload
Unanswered	Q2 is absent; Create explains that Q1 is required.	No request is sent.
Adversarial	Q2 reveals labels from `GET /app/matter-types/{id}/participant-labels`.	`representingSide: adversarial` plus the selected label id and name on the `us` party.
Advisory	Q2 stays absent.	`representingSide: advisory`; participant-label fields are omitted.
Labels unavailable	Q2 shows an honest loading, empty, no-type, or retryable error state instead of an empty radio group.	Create remains blocked until a configured label can be selected.

Storybook proof

AddMatter/RepresentingSideField / Unanswered
AddMatter/RepresentingSideField / Adversarial
AddMatter/RepresentingSideField / Advisory
AddMatter/RepresentingSideField / Loading
AddMatter/RepresentingSideField / Empty
AddMatter/RepresentingSideField / Participant Label Required
AddMatter/RepresentingSideField / Interactive

Deliberate follow-up boundary

Story-2795 owns the richer matter-type-change refetch experience. This story includes explicit loading, empty, error, and no-type states at the participant-label boundary.

Files changed

54 file(s), +1723 / -622 lines

Path	Role	+	-
messages/en.json	Config	+12	-13
messages/hi.json	Config	+12	-13
openapi/app-api.json	Config	+160	-0
openapi/permission-map.json	Config	+9	-0
src/app/[locale]/(workspace)/clients/client-related-matters-presentation.test.ts	App route	+0	-2
src/app/api/internal/matter-types/[matterTypeId]/participant-labels/route.ts	App route	+20	-0
src/components/add-matter/AGENTS.md	Component	+8	-4
src/components/add-matter/add-matter-drawer-types.ts	Component	+20	-20
src/components/add-matter/add-matter-drawer.stories.tsx	Component	+6	-53
src/components/add-matter/add-matter-drawer.tsx	Component	+7	-10
src/components/add-matter/representing-side-field.stories.tsx	Component	+62	-73
src/components/add-matter/representing-side-field.tsx	Component	+249	-295
src/components/add-matter/use-add-matter-drawer-form.ts	Component	+24	-5
src/components/agents/agent-chat-panel.render.test.tsx	Component	+0	-2
src/components/agents/agent-dock-mount.render.test.tsx	Component	+0	-2
src/components/agents/render-catalog/render-catalog.fixtures.ts	Component	+0	-2
src/components/clients/client-related-matters-fixtures.ts	Component	+0	-2
src/components/matter-detail/brief/matter-brief-page.stories.tsx	Component	+0	-2
src/components/matters/add-matter-launcher.tsx	Component	+56	-24
src/components/matters/live-matters-wizard-payload.ts	Component	+28	-14
src/components/matters/matters-live-register-row.stories.tsx	Component	+0	-2
src/components/route-loading.stories.tsx	Component	+29	-0
src/components/route-loading.tsx	Component	+15	-3
src/gen/client/appListMatterTypeParticipantLabels.ts	Generated contract	+65	-0
src/gen/client/index.ts	Generated contract	+1	-0
src/gen/hooks/index.ts	Generated contract	+8	-0
src/gen/hooks/useAppListMatterTypeParticipantLabels.ts	Generated contract	+141	-0
src/gen/hooks/useAppListMatterTypeParticipantLabelsSuspense.ts	Generated contract	+141	-0
src/gen/index.ts	Generated contract	+36	-0
src/gen/schemas/matterTypeParticipantLabelListItem.json	Generated contract	+43	-0
src/gen/schemas/matterTypeParticipantLabelListResponse.json	Generated contract	+56	-0
src/gen/types/AppListMatterTypeParticipantLabels.ts	Generated contract	+71	-0
src/gen/types/MatterTypeParticipantLabelListItem.ts	Generated contract	+39	-0
src/gen/types/MatterTypeParticipantLabelListResponse.ts	Generated contract	+18	-0
src/gen/types/index.ts	Generated contract	+14	-0
src/gen/zod/appListMatterTypeParticipantLabelsSchema.ts	Generated contract	+86	-0
src/gen/zod/index.ts	Generated contract	+13	-0
src/gen/zod/matterTypeParticipantLabelListItemSchema.ts	Generated contract	+29	-0
src/gen/zod/matterTypeParticipantLabelListResponseSchema.ts	Generated contract	+17	-0
src/lib/agents/__tests__/atlas-rail-store.test.ts	Library	+0	-2
src/lib/agents/atlas-rail.test.ts	Library	+0	-2
src/lib/agents/dock-render-bridge.test.ts	Library	+0	-2
src/lib/matter-types/gateway.ts	Library	+29	-0
src/lib/matter-types/types.ts	Library	+1	-0
src/lib/matters/format.test.ts	Library	+0	-27
src/lib/matters/format.ts	Library	+0	-31
src/lib/matters/optimistic.test.ts	Library	+0	-2
tests/unit/live-matters-wizard-payload.test.ts	Test	+19	-5
tests/unit/matter-shell-chrome.test.tsx	Test	+0	-2
tests/unit/matter-type-participant-label-contract.test.ts	Test	+23	-0
tests/unit/matters-contract.test.ts	Test	+0	-2
tests/unit/record-bootstrap-contract.test.ts	Test	+0	-2
tests/unit/representing-side-field.test.tsx	Test	+95	-0
tests/unit/use-add-matter-drawer-form.test.tsx	Test	+61	-4