agents: remove the hive-level /model control; the swarm editor sets the model

The per-agent web UI no longer sets the model: the `/model` slash
command, the model picker, `POST /api/model`, `Bus::set_model` and the
`hyperhive-model` writer are gone. The model chip is display-only and
shows where the model comes from (`model_source` in `/api/state`). The
model is set on the swarm (swarm UI agents page, `swarmctl agent
inference set`).

The read side is unchanged: with no swarm value an agent runs its
agent.nix model, else an existing `hyperhive-model` file, else haiku.
Existing files are not touched.

With the picker gone, its model list goes too: `available_models` in
`/api/state`, the ACP model-list filter, and the harness's global
`HIVE_AVAILABLE_MODELS`. The subagent daemon keeps its own
`HIVE_AVAILABLE_MODELS` from mcp.nix, and the `availableModels`
assertion stays.

`/effort` (command, picker, route, file) is unchanged.

Refs #5034

frontend/packages/agent/src/Root.tsx

@@ -26,7 +26,7 @@ import { useTodos } from "./hooks/useTodos.js";
 import { fmtAge, fmtTokens } from "./lib/format.js";
 import { resolveDashboardBase } from "./lib/dashboardBase.js";
 import { submitPauseResume } from "./lib/pauseAction.js";
-import { postModel, postEffort } from "./lib/modelEffort.js";
+import { postEffort } from "./lib/modelEffort.js";
 import {
   postCancelTurn,
   postLogout,
@@ -220,8 +220,6 @@ export function Root() {
               statusLabel="… connecting"
               statusTone="neutral"
               model=""
-              availableModels={[]}
-              onSelectModel={() => {}}
               effort=""
               availableEfforts={[]}
               onSelectEffort={() => {}}
@@ -308,10 +306,7 @@ export function Root() {
             statusTooltip={primaryStatus.tooltip}
             model={state.model}
             resolvedModel={state.resolved_model ?? undefined}
-            availableModels={state.available_models}
-            onSelectModel={(name) => {
-              postModel(name).then(() => refresh());
-            }}
+            modelSource={state.model_source}
             effort={state.effort}
             availableEfforts={state.available_efforts}
             onSelectEffort={(level) => {

frontend/packages/agent/src/components/StatusChips.css

@@ -13,8 +13,8 @@
 /* mara, live, on a screenshot of this row: "badges and interactive
    elements on same row have inconsistent size." Real cause: Badge.css's
    `.ui-badge-interactive` grows to a 2.75em WCAG touch-target floor
-   (model/effort pickers, pause) while a plain display `<span>` badge
-   (alive, state, ctx, cost — no `onClick`) stays compact, so the row
+   (effort picker, pause) while a plain display `<span>` badge
+   (model, alive, state, ctx, cost — no `onClick`) stays compact, so the row
    reads as two different pill sizes even though every badge here is
    the same `<Badge>` component. Scoped to this row rather than
    Badge.css itself — display-only badges elsewhere (e.g. the dashboard)

frontend/packages/agent/src/components/StatusChips.tsx

@@ -1,6 +1,7 @@
 // <StatusChips> — the agent page's status row: the consolidated status
 // badge (alive/thinking/paused/etc., with pause/resume + cancel-turn in
-// its dropdown), the model + effort pickers, and context/cost usage.
+// its dropdown), the model (display-only: the swarm sets it), the effort
+// picker, and context/cost usage.
 // This is the concrete fix for the design guide's own named anti-example
 // (the old page's model/effort *pickers* lived in the `⋯` overflow menu
 // while the current model/effort only showed as a disconnected chip) —
@@ -13,6 +14,7 @@
 import { useRef, useState } from "preact/hooks";
 import { Badge, type BadgeTone } from "@hive/shared/badge.js";
 import { Dropdown, type DropdownOption } from "@hive/shared/dropdown.js";
+import type { ModelSource } from "../types.js";
 import "./StatusChips.css";
 
 export interface StatusChipsProps {
@@ -25,8 +27,8 @@ export interface StatusChipsProps {
    * operator can tell what an alias resolved to. `undefined` before any
    * turn has completed. */
   resolvedModel?: string;
-  availableModels: string[];
-  onSelectModel: (name: string) => void;
+  /** Where `model` comes from (`/api/state` `model_source`). */
+  modelSource?: ModelSource;
   effort: string;
   availableEfforts: string[];
   onSelectEffort: (level: string) => void;
@@ -50,10 +52,11 @@ export interface StatusChipsProps {
   onLogout: () => Promise<void>;
 }
 
-const MODEL_DESCRIPTIONS: Record<string, string> = {
-  haiku: "fast",
-  sonnet: "balanced",
-  opus: "powerful",
+const SOURCE_LABEL: Record<ModelSource, string> = {
+  swarm: "set on the swarm",
+  agent_nix: "from agent.nix",
+  local_file: "from its own earlier pick",
+  default: "the built-in default",
 };
 const EFFORT_DESCRIPTIONS: Record<string, string> = {
   low: "",
@@ -235,8 +238,7 @@ export function StatusChips({
   statusTooltip,
   model,
   resolvedModel,
-  availableModels,
-  onSelectModel,
+  modelSource,
   effort,
   availableEfforts,
   onSelectEffort,
@@ -263,13 +265,17 @@ export function StatusChips({
         onNewSession={onNewSession}
         onLogout={onLogout}
       />
-      <Picker
+      <Badge
         label="model"
         value={model}
-        options={availableModels}
-        descriptions={MODEL_DESCRIPTIONS}
-        onSelect={onSelectModel}
-        title={resolvedModel ? `resolved to ${resolvedModel}` : undefined}
+        title={
+          [
+            modelSource ? SOURCE_LABEL[modelSource] : null,
+            resolvedModel ? `resolved to ${resolvedModel}` : null,
+          ]
+            .filter(Boolean)
+            .join(" · ") || undefined
+        }
       />
       {availableEfforts.length ? (
         <Picker

frontend/packages/agent/src/components/TermInput.tsx

@@ -11,7 +11,7 @@
 // (a local note explains what confirming does), typing it again within
 // the same "armed" state fires it — a keyboard-native two-step confirm.
 import { useRef, useState } from "preact/hooks";
-import { postModel, postEffort } from "../lib/modelEffort.js";
+import { postEffort } from "../lib/modelEffort.js";
 import {
   postCancelTurn,
   postCompact,
@@ -32,10 +32,6 @@ const SLASH_COMMANDS: { name: string; desc: string }[] = [
   { name: "/clear", desc: "wipe the terminal panel (local-only)" },
   { name: "/cancel", desc: "SIGINT the in-flight claude turn" },
   { name: "/compact", desc: "compact the persistent claude session" },
-  {
-    name: "/model",
-    desc: "/model <name>  — switch claude model for future turns",
-  },
   {
     name: "/effort",
     desc: "/effort <level>  — set claude effort (medium/high/xhigh) for future turns",
@@ -131,16 +127,6 @@ export function TermInput({
           );
         }
         return true;
-      case "/model":
-        if (!arg)
-          onLocalNote(
-            "✗ /model needs a name (e.g. /model haiku, /model sonnet, /model opus)",
-          );
-        else
-          postModel(arg).then(
-            (r) => !r.ok && reportFailure("/model", r.detail),
-          );
-        return true;
       case "/effort":
         if (!arg)
           onLocalNote(

frontend/packages/agent/src/lib/modelEffort.ts

@@ -1,4 +1,4 @@
-// POST `/api/model` / `/api/effort` — same-origin (this agent's own
+// POST `/api/effort` — same-origin (this agent's own
 // backend), so a plain `fetch` is safe unlike pause/resume (see
 // pauseAction.ts). `redirect: 'manual'` + the broad "ok" check below is
 // ported from app.js unchanged — the endpoints don't actually redirect
@@ -34,6 +34,5 @@ async function post(
   }
 }
 
-export const postModel = (name: string) => post("api/model", "model", name);
 export const postEffort = (level: string) =>
   post("api/effort", "effort", level);

frontend/packages/agent/src/lib/pauseAction.ts

@@ -6,7 +6,7 @@
 // hive-c0re doesn't need to grow CORS headers for it — the tradeoff is
 // an opaque, unreadable response, which is fine here since the caller
 // doesn't need to read it, only trigger a state refresh afterward (same
-// shape as `postModel`/`postEffort` in modelEffort.ts). `credentials:
+// shape as `postEffort` in modelEffort.ts). `credentials:
 // 'include'` matches the cookie-sending behavior of the plain <form>
 // submit this replaces.
 //

frontend/packages/agent/src/types.ts

@@ -4,6 +4,9 @@
 // today, and the frontend only ever reads a handful of these fields.
 // Extend as more of the page gets rebuilt against real data.
 
+// Mirrors `swarm_queue_client::agent_inference::Source`.
+export type ModelSource = "swarm" | "agent_nix" | "local_file" | "default";
+
 export interface AgentState {
   seq: number;
   label: string;
@@ -24,7 +27,7 @@ export interface AgentState {
   cost_usage: TokenUsage | null;
   hive_name: string | null;
   swarm_name: string | null;
-  available_models: string[];
+  model_source: ModelSource;
   effort: string;
   available_efforts: string[];
   paused: boolean;