feat(plugin): expose session selection methods (#43718)

packages/core/src/plugin/host.ts

@@ -401,6 +401,8 @@ export const make = Effect.fn("PluginHost.make")(function* (
             input?.location ?? Location.Ref.make({ directory: location.directory, workspaceID: location.workspaceID }),
         }),
       get: (input) => runtime.session.get(input.sessionID),
+      switchAgent: runtime.session.switchAgent,
+      switchModel: runtime.session.switchModel,
       prompt: runtime.session.prompt,
       generate: (input) => runtime.session.generate(input).pipe(Effect.map((text) => ({ text }))),
       command: runtime.session.command,

packages/core/test/plugin/host.ts

@@ -117,6 +117,8 @@ export function host(overrides: Overrides = {}): Plugin.Context {
       hook: overrides.session?.hook ?? (() => Effect.die("unused session.hook")),
       create: overrides.session?.create ?? (() => Effect.die("unused session.create")),
       get: overrides.session?.get ?? (() => Effect.die("unused session.get")),
+      switchAgent: overrides.session?.switchAgent ?? (() => Effect.die("unused session.switchAgent")),
+      switchModel: overrides.session?.switchModel ?? (() => Effect.die("unused session.switchModel")),
       prompt: overrides.session?.prompt ?? (() => Effect.die("unused session.prompt")),
       generate: overrides.session?.generate ?? (() => Effect.die("unused session.generate")),
       command: overrides.session?.command ?? (() => Effect.die("unused session.command")),

packages/core/test/plugin/promise.test.ts

@@ -133,6 +133,8 @@ describe("fromPromise", () => {
             expect(input.continue).toBe(true)
             return Effect.void
           },
+          switchAgent: (input) => Effect.sync(() => seen.push(input)),
+          switchModel: (input) => Effect.sync(() => seen.push(input)),
           rename: (input) => Effect.sync(() => seen.push(input)),
           wait: (input) => Effect.sync(() => seen.push(input)),
         },
@@ -144,6 +146,13 @@ describe("fromPromise", () => {
           setup: async (ctx) => {
             expect(await ctx.session.interrupt({ sessionID: "ses_success", continue: true })).toBeUndefined()
             await expect(ctx.session.interrupt({ sessionID: "ses_failure" })).rejects.toThrow("interrupt failed")
+            expect(await ctx.session.switchAgent({ sessionID: "ses_success", agent: "build" })).toBeUndefined()
+            expect(
+              await ctx.session.switchModel({
+                sessionID: "ses_success",
+                model: { providerID: "openai", id: "gpt-5" },
+              }),
+            ).toBeUndefined()
             expect(await ctx.session.rename({ sessionID: "ses_success", title: "Renamed" })).toBeUndefined()
             expect(await ctx.session.wait({ sessionID: "ses_success" })).toBeUndefined()
           },
@@ -151,6 +160,11 @@ describe("fromPromise", () => {
       ).effect(host)
 
       expect(seen).toEqual([
+        { sessionID: Session.ID.make("ses_success"), agent: Agent.ID.make("build") },
+        {
+          sessionID: Session.ID.make("ses_success"),
+          model: { providerID: Provider.ID.make("openai"), id: Model.ID.make("gpt-5") },
+        },
         { sessionID: Session.ID.make("ses_success"), title: "Renamed" },
         { sessionID: Session.ID.make("ses_success") },
       ])

packages/plugin/src/effect/session.ts

@@ -47,7 +47,17 @@ export interface SessionHooks {
 
 export type SessionDomain = Pick<
   SessionApi<unknown>,
-  "create" | "get" | "prompt" | "generate" | "command" | "synthetic" | "interrupt" | "rename" | "wait"
+  | "create"
+  | "get"
+  | "switchAgent"
+  | "switchModel"
+  | "prompt"
+  | "generate"
+  | "command"
+  | "synthetic"
+  | "interrupt"
+  | "rename"
+  | "wait"
 > & {
   readonly hook: ModelHooks<SessionHooks>
 }

packages/plugin/src/promise/adapter.ts

@@ -309,6 +309,8 @@ export function fromPromise(plugin: Plugin) {
               ),
             create: adaptApiMethod(SessionEndpoints["session.create"], host.session.create),
             get: adaptApiMethod(SessionEndpoints["session.get"], host.session.get),
+            switchAgent: adaptApiMethod(SessionEndpoints["session.switchAgent"], host.session.switchAgent),
+            switchModel: adaptApiMethod(SessionEndpoints["session.switchModel"], host.session.switchModel),
             prompt: adaptApiMethod(SessionEndpoints["session.prompt"], host.session.prompt),
             generate: adaptApiMethod(SessionEndpoints["session.generate"], host.session.generate),
             command: adaptApiMethod(SessionEndpoints["session.command"], host.session.command),

packages/plugin/src/promise/session.ts

@@ -47,7 +47,17 @@ export interface SessionHooks {
 
 export type SessionDomain = Pick<
   SessionApi,
-  "create" | "get" | "prompt" | "generate" | "command" | "synthetic" | "interrupt" | "rename" | "wait"
+  | "create"
+  | "get"
+  | "switchAgent"
+  | "switchModel"
+  | "prompt"
+  | "generate"
+  | "command"
+  | "synthetic"
+  | "interrupt"
+  | "rename"
+  | "wait"
 > & {
   readonly hook: ModelHooks<SessionHooks>
 }