feat(core): port v2 command invocation (#34849)

packages/protocol/src/errors.ts

@@ -89,6 +89,24 @@ export class SkillNotFoundError extends Schema.TaggedErrorClass<SkillNotFoundErr
   { httpApiStatus: 404 },
 ) {}
 
+export class CommandNotFoundError extends Schema.TaggedErrorClass<CommandNotFoundError>()(
+  "CommandNotFoundError",
+  {
+    command: Schema.String,
+    message: Schema.String,
+  },
+  { httpApiStatus: 404 },
+) {}
+
+export class CommandEvaluationError extends Schema.TaggedErrorClass<CommandEvaluationError>()(
+  "CommandEvaluationError",
+  {
+    command: Schema.String,
+    message: Schema.String,
+  },
+  { httpApiStatus: 500 },
+) {}
+
 export class InvalidCursorError extends Schema.TaggedErrorClass<InvalidCursorError>()(
   "InvalidCursorError",
   { message: Schema.String },

packages/protocol/src/groups/session.ts

@@ -10,6 +10,8 @@ import { Context, Effect, Encoding, Result, Schema, Struct } from "effect"
 import { HttpApiEndpoint, HttpApiGroup, HttpApiMiddleware, HttpApiSchema, OpenApi } from "effect/unstable/httpapi"
 import {
   ConflictError,
+  CommandEvaluationError,
+  CommandNotFoundError,
   InvalidCursorError,
   InvalidRequestError,
   MessageNotFoundError,
@@ -258,6 +260,32 @@ export const makeSessionGroup = <I extends HttpApiMiddleware.AnyId, S>(sessionLo
           }),
         ),
     )
+    .add(
+      HttpApiEndpoint.post("session.command", "/api/session/:sessionID/command", {
+        params: { sessionID: Session.ID },
+        payload: Schema.Struct({
+          id: SessionMessage.ID.pipe(Schema.optional),
+          command: Schema.String,
+          arguments: Schema.String.pipe(Schema.optional),
+          agent: Schema.String.pipe(Schema.optional),
+          model: Model.Ref.pipe(Schema.optional),
+          files: PromptInput.Prompt.fields.files,
+          agents: PromptInput.Prompt.fields.agents,
+          delivery: SessionInput.Delivery.pipe(Schema.optional),
+          resume: Schema.Boolean.pipe(Schema.optional),
+        }),
+        success: Schema.Struct({ data: SessionInput.Admitted }),
+        error: [ConflictError, SessionNotFoundError, CommandNotFoundError, CommandEvaluationError],
+      })
+        .middleware(sessionLocationMiddleware)
+        .annotateMerge(
+          OpenApi.annotations({
+            identifier: "v2.session.command",
+            summary: "Run command",
+            description: "Resolve a slash command into prompt input, admit it durably, and schedule execution unless resume is false.",
+          }),
+        ),
+    )
     .add(
       HttpApiEndpoint.post("session.skill", "/api/session/:sessionID/skill", {
         params: { sessionID: Session.ID },