feat(session): add messageCount endpoint for efficient message counting

Author: sjawhar

packages/opencode/src/server/routes/session.ts

@@ -579,6 +579,36 @@ export const SessionRoutes = lazy(() =>
         return c.json(messages)
       },
     )
+    .get(
+      "/:sessionID/message/count",
+      describeRoute({
+        summary: "Get message count",
+        description: "Get the total number of messages in a session.",
+        operationId: "session.messageCount",
+        responses: {
+          200: {
+            description: "Message count",
+            content: {
+              "application/json": {
+                schema: resolver(z.object({ count: z.number() })),
+              },
+            },
+          },
+          ...errors(400, 404),
+        },
+      }),
+      validator(
+        "param",
+        z.object({
+          sessionID: z.string().meta({ description: "Session ID" }),
+        }),
+      ),
+      async (c) => {
+        const sessionID = c.req.valid("param").sessionID
+        const count = await Session.messageCount({ sessionID })
+        return c.json({ count })
+      },
+    )
     .get(
       "/:sessionID/message/:messageID",
       describeRoute({

packages/opencode/src/session/index.ts

@@ -10,7 +10,7 @@ import { Flag } from "../flag/flag"
 import { Identifier } from "../id/id"
 import { Installation } from "../installation"
 
-import { Database, NotFoundError, eq, and, or, gte, isNull, desc, like, inArray, lt } from "../storage/db"
+import { Database, NotFoundError, eq, and, or, gte, isNull, desc, like, inArray, lt, sql } from "../storage/db"
 import type { SQL } from "../storage/db"
 import { SessionTable, MessageTable, PartTable } from "./session.sql"
 import { ProjectTable } from "../project/project.sql"
@@ -525,6 +525,22 @@ export namespace Session {
     },
   )
 
+  export const messageCount = fn(
+    z.object({
+      sessionID: Identifier.schema("session"),
+    }),
+    async (input) => {
+      const result = Database.use((db) =>
+        db
+          .select({ count: sql<number>`COUNT(*)` })
+          .from(MessageTable)
+          .where(eq(MessageTable.session_id, input.sessionID))
+          .get(),
+      )
+      return result?.count ?? 0
+    },
+  )
+
   export function* list(input?: {
     directory?: string
     roots?: boolean

packages/sdk/js/src/v2/gen/sdk.gen.ts

@@ -115,6 +115,8 @@ import type {
   SessionInitErrors,
   SessionInitResponses,
   SessionListResponses,
+  SessionMessageCountErrors,
+  SessionMessageCountResponses,
   SessionMessageErrors,
   SessionMessageResponses,
   SessionMessagesErrors,
@@ -1561,6 +1563,36 @@ export class Session2 extends HeyApiClient {
     })
   }
 
+  /**
+   * Get message count
+   *
+   * Get the total number of messages in a session.
+   */
+  public messageCount<ThrowOnError extends boolean = false>(
+    parameters: {
+      sessionID: string
+      directory?: string
+    },
+    options?: Options<never, ThrowOnError>,
+  ) {
+    const params = buildClientParams(
+      [parameters],
+      [
+        {
+          args: [
+            { in: "path", key: "sessionID" },
+            { in: "query", key: "directory" },
+          ],
+        },
+      ],
+    )
+    return (options?.client ?? this.client).get<SessionMessageCountResponses, SessionMessageCountErrors, ThrowOnError>({
+      url: "/session/{sessionID}/message/count",
+      ...options,
+      ...params,
+    })
+  }
+
   /**
    * Get message
    *

packages/sdk/js/src/v2/gen/types.gen.ts

@@ -3564,6 +3564,44 @@ export type SessionPromptResponses = {
 
 export type SessionPromptResponse = SessionPromptResponses[keyof SessionPromptResponses]
 
+export type SessionMessageCountData = {
+  body?: never
+  path: {
+    /**
+     * Session ID
+     */
+    sessionID: string
+  }
+  query?: {
+    directory?: string
+  }
+  url: "/session/{sessionID}/message/count"
+}
+
+export type SessionMessageCountErrors = {
+  /**
+   * Bad request
+   */
+  400: BadRequestError
+  /**
+   * Not found
+   */
+  404: NotFoundError
+}
+
+export type SessionMessageCountError = SessionMessageCountErrors[keyof SessionMessageCountErrors]
+
+export type SessionMessageCountResponses = {
+  /**
+   * Message count
+   */
+  200: {
+    count: number
+  }
+}
+
+export type SessionMessageCountResponse = SessionMessageCountResponses[keyof SessionMessageCountResponses]
+
 export type SessionMessageData = {
   body?: never
   path: {