diff --git a/packages/app/src/components/prompt-input/submit.ts b/packages/app/src/components/prompt-input/submit.ts
index 4a40281567..8d404114b7 100644
--- a/packages/app/src/components/prompt-input/submit.ts
+++ b/packages/app/src/components/prompt-input/submit.ts
@@ -76,6 +76,27 @@ export async function sendFollowupDraft(input: FollowupSendInput) {
     return true
   }
 
+  const select = async () => {
+    const session = input.session()
+    if (session?.agent !== input.draft.agent) {
+      await input.api.switchAgent({ sessionID: input.draft.sessionID, agent: input.draft.agent })
+    }
+    if (
+      session?.model?.providerID === input.draft.model.providerID &&
+      session.model.id === input.draft.model.modelID &&
+      (session.model.variant ?? "default") === (input.draft.variant ?? "default")
+    )
+      return
+    await input.api.switchModel({
+      sessionID: input.draft.sessionID,
+      model: {
+        id: input.draft.model.modelID,
+        providerID: input.draft.model.providerID,
+        variant: input.draft.variant,
+      },
+    })
+  }
+
   const [head, ...tail] = text.split(" ")
   const cmd = head?.startsWith("/") ? head.slice(1) : undefined
   if (cmd && input.sync.data.command.find((item) => item.name === cmd)) {
@@ -86,18 +107,13 @@ export async function sendFollowupDraft(input: FollowupSendInput) {
         return false
       }
 
+      await select()
       const messageID = Identifier.ascending("message")
       await input.api.command({
         sessionID: input.draft.sessionID,
         id: messageID,
         command: cmd,
         arguments: tail.join(" "),
-        agent: input.draft.agent,
-        model: {
-          id: input.draft.model.modelID,
-          providerID: input.draft.model.providerID,
-          variant: input.draft.variant,
-        },
         files: await Promise.all(
           images.map(async (attachment) => ({
             uri: await blobDataUrl(attachment.blob, attachment.mime),
@@ -167,24 +183,7 @@ export async function sendFollowupDraft(input: FollowupSendInput) {
       return false
     }
 
-    const session = input.session()
-    if (session?.agent !== input.draft.agent) {
-      await input.api.switchAgent({ sessionID: input.draft.sessionID, agent: input.draft.agent })
-    }
-    if (
-      session?.model?.providerID !== input.draft.model.providerID ||
-      session.model.id !== input.draft.model.modelID ||
-      (session.model.variant ?? "default") !== (input.draft.variant ?? "default")
-    ) {
-      await input.api.switchModel({
-        sessionID: input.draft.sessionID,
-        model: {
-          id: input.draft.model.modelID,
-          providerID: input.draft.model.providerID,
-          variant: input.draft.variant,
-        },
-      })
-    }
+    await select()
 
     await input.api.prompt({
       sessionID: input.draft.sessionID,
@@ -524,14 +523,22 @@ export function createPromptSubmit(input: PromptSubmitInput) {
         clearInput()
         const messageID = Identifier.ascending("message")
         serverSync().session.set("session_status", session.id, { type: "busy" })
-        sdk()
-          .api.session.command({
+        void (async () => {
+          if (session.agent !== agent) await sdk().api.session.switchAgent({ sessionID: session.id, agent })
+          if (
+            session.model?.providerID !== model.providerID ||
+            session.model.id !== model.modelID ||
+            (session.model.variant ?? "default") !== (variant ?? "default")
+          )
+            await sdk().api.session.switchModel({
+              sessionID: session.id,
+              model: { id: model.modelID, providerID: model.providerID, variant },
+            })
+          await sdk().api.session.command({
             sessionID: session.id,
             id: messageID,
             command: commandName,
             arguments: args.join(" "),
-            agent,
-            model: { id: model.modelID, providerID: model.providerID, variant },
             files: await Promise.all(
               images.map(async (attachment) => ({
                 uri: await blobDataUrl(attachment.blob, attachment.mime),
@@ -539,14 +546,14 @@ export function createPromptSubmit(input: PromptSubmitInput) {
               })),
             ),
           })
-          .catch((err) => {
-            serverSync().session.set("session_status", session.id, { type: "idle" })
-            showToast({
-              title: language.t("prompt.toast.commandSendFailed.title"),
-              description: formatServerError(err, language.t, language.t("common.requestFailed")),
-            })
-            restoreInput()
+        })().catch((err) => {
+          serverSync().session.set("session_status", session.id, { type: "idle" })
+          showToast({
+            title: language.t("prompt.toast.commandSendFailed.title"),
+            description: formatServerError(err, language.t, language.t("common.requestFailed")),
           })
+          restoreInput()
+        })
         return
       }
     }
diff --git a/packages/client/src/effect/api/api.ts b/packages/client/src/effect/api/api.ts
index 52b848b2ea..733e516b00 100644
--- a/packages/client/src/effect/api/api.ts
+++ b/packages/client/src/effect/api/api.ts
@@ -193,8 +193,6 @@ export type Endpoint5_13Input = {
   readonly id?: SessionMessage.ID | undefined
   readonly command: string
   readonly arguments?: string | undefined
-  readonly agent?: Agent.ID | undefined
-  readonly model?: Model.Ref | undefined
   readonly files?: ReadonlyArray<PromptInput.FileAttachment> | undefined
   readonly agents?: ReadonlyArray<AgentAttachment> | undefined
   readonly skills?: ReadonlyArray<PromptInput.SkillAttachment> | undefined
diff --git a/packages/client/src/effect/generated/client.ts b/packages/client/src/effect/generated/client.ts
index cc334c9709..cad50d36b0 100644
--- a/packages/client/src/effect/generated/client.ts
+++ b/packages/client/src/effect/generated/client.ts
@@ -431,8 +431,6 @@ const Endpoint5_13 = (raw: RawClient["server.session"]) => (input: Endpoint5_13I
         id: input["id"],
         command: input["command"],
         arguments: input["arguments"],
-        agent: input["agent"],
-        model: input["model"],
         files: input["files"],
         agents: input["agents"],
         skills: input["skills"],
diff --git a/packages/client/src/promise/generated/client.ts b/packages/client/src/promise/generated/client.ts
index 8dbcd8c966..52b2749ceb 100644
--- a/packages/client/src/promise/generated/client.ts
+++ b/packages/client/src/promise/generated/client.ts
@@ -635,8 +635,6 @@ export function make(options: ClientOptions) {
               id: input["id"],
               command: input["command"],
               arguments: input["arguments"],
-              agent: input["agent"],
-              model: input["model"],
               files: input["files"],
               agents: input["agents"],
               skills: input["skills"],
diff --git a/packages/client/src/promise/generated/types.ts b/packages/client/src/promise/generated/types.ts
index 747f0492e0..186a80eb2b 100644
--- a/packages/client/src/promise/generated/types.ts
+++ b/packages/client/src/promise/generated/types.ts
@@ -3485,8 +3485,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3508,8 +3506,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3531,8 +3527,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3550,58 +3544,10 @@ export type SessionCommandInput = {
     readonly delivery?: "steer" | "queue" | null
     readonly resume?: boolean | null
   }["arguments"]
-  readonly agent?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: "steer" | "queue" | null
-    readonly resume?: boolean | null
-  }["agent"]
-  readonly model?: {
-    readonly id?: string | null
-    readonly command: string
-    readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
-    readonly files?: ReadonlyArray<{
-      readonly uri: string
-      readonly name?: string
-      readonly description?: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly agents?: ReadonlyArray<{
-      readonly name: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly skills?: ReadonlyArray<{
-      readonly id: string
-      readonly mention?: { readonly start: number; readonly end: number; readonly text: string }
-    }>
-    readonly delivery?: "steer" | "queue" | null
-    readonly resume?: boolean | null
-  }["model"]
   readonly files?: {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3623,8 +3569,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3646,8 +3590,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3669,8 +3611,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
@@ -3692,8 +3632,6 @@ export type SessionCommandInput = {
     readonly id?: string | null
     readonly command: string
     readonly arguments?: string | null
-    readonly agent?: string | null
-    readonly model?: { readonly id: string; readonly providerID: string; readonly variant?: string } | null
     readonly files?: ReadonlyArray<{
       readonly uri: string
       readonly name?: string
diff --git a/packages/core/src/plugin/promise.ts b/packages/core/src/plugin/promise.ts
index d256fb8964..beedb00a12 100644
--- a/packages/core/src/plugin/promise.ts
+++ b/packages/core/src/plugin/promise.ts
@@ -310,8 +310,6 @@ export function fromPromise(plugin: Plugin) {
                   ...input,
                   sessionID: Session.ID.make(input.sessionID),
                   id: input.id == null ? undefined : SessionMessage.ID.make(input.id),
-                  agent: input.agent == null ? undefined : Agent.ID.make(input.agent),
-                  model: input.model == null ? undefined : model(input.model),
                   skills: input.skills?.map((skill) => ({ ...skill, id: Skill.ID.make(skill.id) })),
                   arguments: input.arguments ?? undefined,
                   delivery: input.delivery ?? undefined,
diff --git a/packages/core/src/session.ts b/packages/core/src/session.ts
index fb49b19cb8..3d7ab84111 100644
--- a/packages/core/src/session.ts
+++ b/packages/core/src/session.ts
@@ -233,8 +233,6 @@ export interface Interface {
     sessionID: SessionSchema.ID
     command: string
     arguments?: string
-    agent?: Agent.ID
-    model?: Model.Ref
     files?: PromptInput.Prompt["files"]
     agents?: PromptInput.Prompt["agents"]
     skills?: PromptInput.Prompt["skills"]
@@ -625,13 +623,13 @@ const layer = Layer.effect(
         const evaluated = yield* commands.evaluate({ name: input.command, arguments: input.arguments })
 
         // TODO(v2 commands): decide whether command-level subtask/background execution belongs in v2 commands.
-        const agent = command.agent ?? input.agent
+        const agent = command.agent
         const commandAgent = yield* Effect.gen(function* () {
           if (!command.agent) return undefined
           const agents = yield* Agent.Service.pipe(Effect.provide(locations.get(session.location)))
           return yield* agents.get(Agent.ID.make(command.agent))
         })
-        const model = command.model ?? commandAgent?.model ?? input.model
+        const model = command.model ?? commandAgent?.model
         if (agent !== undefined && session.agent !== Agent.ID.make(agent))
           yield* result.switchAgent({ sessionID: input.sessionID, agent: Agent.ID.make(agent) })
         if (model !== undefined) yield* result.switchModel({ sessionID: input.sessionID, model })
diff --git a/packages/protocol/src/groups/session.ts b/packages/protocol/src/groups/session.ts
index 543442039f..8799e06fb4 100644
--- a/packages/protocol/src/groups/session.ts
+++ b/packages/protocol/src/groups/session.ts
@@ -341,8 +341,6 @@ export const makeSessionGroup = <I extends HttpApiMiddleware.AnyId, S>(sessionLo
           id: SessionMessage.ID.pipe(Schema.optional),
           command: Schema.String,
           arguments: Schema.String.pipe(Schema.optional),
-          agent: Agent.ID.pipe(Schema.optional),
-          model: Model.Ref.pipe(Schema.optional),
           files: PromptInput.Prompt.fields.files,
           agents: PromptInput.Prompt.fields.agents,
           skills: PromptInput.Prompt.fields.skills,
diff --git a/packages/server/src/handlers/session.ts b/packages/server/src/handlers/session.ts
index 8691e480c1..bc7f654f02 100644
--- a/packages/server/src/handlers/session.ts
+++ b/packages/server/src/handlers/session.ts
@@ -355,8 +355,6 @@ export const SessionHandler = HttpApiBuilder.group(Api, "server.session", (handl
                 id: ctx.payload.id,
                 command: ctx.payload.command,
                 arguments: ctx.payload.arguments,
-                agent: ctx.payload.agent,
-                model: ctx.payload.model,
                 files: ctx.payload.files,
                 agents: ctx.payload.agents,
                 skills: ctx.payload.skills,
diff --git a/packages/tui/src/component/prompt/index.tsx b/packages/tui/src/component/prompt/index.tsx
index 4303432db1..b58c25d250 100644
--- a/packages/tui/src/component/prompt/index.tsx
+++ b/packages/tui/src/component/prompt/index.tsx
@@ -1149,15 +1149,23 @@ export function Prompt(props: PromptProps) {
     } else if (slashHead && isCommand) {
       move.startSubmit()
       const model = { providerID: selection.providerID, id: selection.modelID, variant }
+      if (session?.agent !== agent.id) await client.api.session.switchAgent({ sessionID, agent: agent.id })
       const cancelCommit = local.model.trackSessionCommit(sessionID, model)
+      if (
+        session?.model?.providerID !== model.providerID ||
+        session.model.id !== model.id ||
+        (session.model.variant ?? "default") !== (model.variant ?? "default")
+      )
+        await client.api.session.switchModel({ sessionID, model }).catch((error) => {
+          cancelCommit()
+          throw error
+        })
 
       void client.api.session
         .command({
           sessionID,
           command: slashHead.name,
           arguments: slashHead.arguments,
-          agent: agent.id,
-          model,
           files: store.prompt.files,
           agents: store.prompt.agents,
           skills: store.prompt.skills?.length ? store.prompt.skills : undefined,
diff --git a/packages/tui/src/mini/stream-v2.transport.ts b/packages/tui/src/mini/stream-v2.transport.ts
index 438993cf54..b8d4f2602e 100644
--- a/packages/tui/src/mini/stream-v2.transport.ts
+++ b/packages/tui/src/mini/stream-v2.transport.ts
@@ -1653,8 +1653,6 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
       )
     }
 
-    const selected = await resolveSelectedModel(input, client, next)
-    if (next.variant && !selected) throw new Error("Cannot select a variant before selecting a model")
     input.trace?.write("send.command", { sessionID: input.sessionID, messageID, command: command.name, delivery })
     return client.session.command(
       {
@@ -1662,8 +1660,6 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
         id: messageID,
         command: command.name,
         arguments: command.arguments,
-        agent: next.agent,
-        model: selected,
         files: attachments.files.length ? attachments.files : undefined,
         agents: agents.length ? agents : undefined,
         skills: skills.length ? skills : undefined,
@@ -1706,12 +1702,10 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
       const client = sdk
       if (next.agent)
         await client.session.switchAgent({ sessionID: input.sessionID, agent: next.agent }, { signal: next.signal })
-      if (!next.prompt.command) {
-        const selected = await resolveSelectedModel(input, client, next)
-        if (next.variant && !selected) throw new Error("Cannot select a variant before selecting a model")
-        if (selected)
-          await client.session.switchModel({ sessionID: input.sessionID, model: selected }, { signal: next.signal })
-      }
+      const selected = await resolveSelectedModel(input, client, next)
+      if (next.variant && !selected) throw new Error("Cannot select a variant before selecting a model")
+      if (selected)
+        await client.session.switchModel({ sessionID: input.sessionID, model: selected }, { signal: next.signal })
       mergePending(await admitPrompt(next, client, delivery))
       settlementClient = client
     },
@@ -1750,6 +1744,12 @@ export async function createSessionTransport(input: StreamInput): Promise<Sessio
         return
       }
       if (command) {
+        if (next.agent)
+          await client.session.switchAgent({ sessionID: input.sessionID, agent: next.agent }, { signal: next.signal })
+        const selected = await resolveSelectedModel(input, client, next)
+        if (next.variant && !selected) throw new Error("Cannot select a variant before selecting a model")
+        if (selected)
+          await client.session.switchModel({ sessionID: input.sessionID, model: selected }, { signal: next.signal })
         await runTurnWait(
           next,
           messageID,
diff --git a/packages/tui/test/mini/stream-v2.transport.test.ts b/packages/tui/test/mini/stream-v2.transport.test.ts
index 03f8b1322d..7cb0fdcd04 100644
--- a/packages/tui/test/mini/stream-v2.transport.test.ts
+++ b/packages/tui/test/mini/stream-v2.transport.test.ts
@@ -2855,8 +2855,6 @@ describe("V2 mini transport", () => {
       id: "msg_cmd",
       command: "deploy",
       arguments: "prod",
-      agent: "build",
-      model: { providerID: "test", id: "model" },
       files: [
         { uri: "file:///tmp/context.txt", name: "context.txt" },
         {
@@ -2868,9 +2866,11 @@ describe("V2 mini transport", () => {
       skills: [{ id: "api-design", mention: { start: 13, end: 24, text: "/api-design" } }],
       delivery: "steer",
     })
-    // Selection rides the command payload; no separate client-side switch.
-    expect(client.session.switchAgent).not.toHaveBeenCalled()
-    expect(client.session.switchModel).not.toHaveBeenCalled()
+    expect(client.session.switchAgent).toHaveBeenCalledWith({ sessionID: "ses_1", agent: "build" }, expect.anything())
+    expect(client.session.switchModel).toHaveBeenCalledWith(
+      { sessionID: "ses_1", model: { providerID: "test", id: "model" } },
+      expect.anything(),
+    )
     await transport.close()
   })