perf(server): paginate session history (#17134)

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

@@ -569,17 +569,65 @@ export const SessionRoutes = lazy(() =>
       ),
       validator(
         "query",
-        z.object({
-          limit: z.coerce.number().optional(),
-        }),
+        z
+          .object({
+            limit: z.coerce
+              .number()
+              .int()
+              .min(0)
+              .optional()
+              .meta({ description: "Maximum number of messages to return" }),
+            before: z
+              .string()
+              .optional()
+              .meta({ description: "Opaque cursor for loading older messages" })
+              .refine(
+                (value) => {
+                  if (!value) return true
+                  try {
+                    MessageV2.cursor.decode(value)
+                    return true
+                  } catch {
+                    return false
+                  }
+                },
+                { message: "Invalid cursor" },
+              ),
+          })
+          .refine((value) => !value.before || value.limit !== undefined, {
+            message: "before requires limit",
+            path: ["before"],
+          }),
       ),
       async (c) => {
         const query = c.req.valid("query")
-        const messages = await Session.messages({
-          sessionID: c.req.valid("param").sessionID,
+        const sessionID = c.req.valid("param").sessionID
+        if (query.limit === undefined) {
+          await Session.get(sessionID)
+          const messages = await Session.messages({ sessionID })
+          return c.json(messages)
+        }
+
+        if (query.limit === 0) {
+          await Session.get(sessionID)
+          const messages = await Session.messages({ sessionID })
+          return c.json(messages)
+        }
+
+        const page = await MessageV2.page({
+          sessionID,
           limit: query.limit,
+          before: query.before,
         })
-        return c.json(messages)
+        if (page.cursor) {
+          const url = new URL(c.req.url)
+          url.searchParams.set("limit", query.limit.toString())
+          url.searchParams.set("before", page.cursor)
+          c.header("Access-Control-Expose-Headers", "Link, X-Next-Cursor")
+          c.header("Link", `<${url.toString()}>; rel=\"next\"`)
+          c.header("X-Next-Cursor", page.cursor)
+        }
+        return c.json(page.items)
       },
     )
     .get(