diff --git a/packages/opencode/src/session/message-v2.ts b/packages/opencode/src/session/message-v2.ts
index 68157f5f4d89..09bbe266bbc8 100644
--- a/packages/opencode/src/session/message-v2.ts
+++ b/packages/opencode/src/session/message-v2.ts
@@ -18,6 +18,7 @@ import * as ProviderError from "@/provider/error"
 import { iife } from "@/util/iife"
 import { errorMessage } from "@/util/error"
 import { isMedia } from "@/util/media"
+import { isRecord } from "@/util/record"
 import type { SystemError } from "bun"
 import type { Provider } from "@/provider/provider"
 import { ModelID, ProviderID } from "@/provider/schema"
@@ -577,12 +578,30 @@ export const cursor = {
   },
 }
 
-const info = (row: typeof MessageTable.$inferSelect) =>
-  ({
+function infoModel(input: unknown): User["model"] | undefined {
+  if (!isRecord(input) || typeof input.providerID !== "string") return
+  const modelID = typeof input.modelID === "string" ? input.modelID : typeof input.id === "string" ? input.id : undefined
+  if (!modelID) return
+  return {
+    providerID: ProviderID.make(input.providerID),
+    modelID: ModelID.make(modelID),
+    ...(typeof input.variant === "string" ? { variant: input.variant } : {}),
+  }
+}
+
+const legacyModel = (input: unknown, fallback?: User["model"]) =>
+  infoModel(input) ?? fallback ?? { providerID: ProviderID.make("unknown"), modelID: ModelID.make("unknown") }
+
+const info = (row: typeof MessageTable.$inferSelect, fallbackModel?: User["model"]) => {
+  const data = row.data as typeof row.data & { agent?: unknown; mode?: unknown; model?: unknown }
+  return {
     ...row.data,
     id: row.id,
     sessionID: row.session_id,
-  }) as Info
+    ...(typeof data.agent === "string" ? {} : { agent: typeof data.mode === "string" ? data.mode : "build" }),
+    ...(data.role === "user" ? { model: legacyModel(data.model, fallbackModel) } : {}),
+  } as Info
+}
 
 const part = (row: typeof PartTable.$inferSelect) =>
   ({
@@ -598,6 +617,20 @@ const older = (row: Cursor) =>
 function hydrate(rows: (typeof MessageTable.$inferSelect)[]) {
   const ids = rows.map((row) => row.id)
   const partByMessage = new Map<string, Part[]>()
+  const modelByParent = new Map<string, User["model"]>()
+  for (const row of rows) {
+    const data = row.data as typeof row.data & {
+      modelID?: unknown
+      parentID?: unknown
+      providerID?: unknown
+      variant?: unknown
+    }
+    if (data.role !== "assistant" || typeof data.parentID !== "string") continue
+    modelByParent.set(
+      data.parentID,
+      legacyModel({ providerID: data.providerID, modelID: data.modelID, variant: data.variant }),
+    )
+  }
   if (ids.length > 0) {
     const partRows = Database.use((db) =>
       db
@@ -616,7 +649,7 @@ function hydrate(rows: (typeof MessageTable.$inferSelect)[]) {
   }
 
   return rows.map((row) => ({
-    info: info(row),
+    info: info(row, modelByParent.get(row.id)),
     parts: partByMessage.get(row.id) ?? [],
   }))
 }
diff --git a/packages/opencode/test/server/httpapi-session.test.ts b/packages/opencode/test/server/httpapi-session.test.ts
index db06a7a77c73..cdaad7898517 100644
--- a/packages/opencode/test/server/httpapi-session.test.ts
+++ b/packages/opencode/test/server/httpapi-session.test.ts
@@ -20,7 +20,7 @@ import { Session } from "@/session/session"
 import { MessageID, PartID, SessionID, type SessionID as SessionIDType } from "../../src/session/schema"
 import { MessageV2 } from "../../src/session/message-v2"
 import { Database } from "@/storage/db"
-import { SessionMessageTable, SessionTable } from "@/session/session.sql"
+import { MessageTable, SessionMessageTable, SessionTable } from "@/session/session.sql"
 import { SessionMessage } from "@opencode-ai/core/session-message"
 import { ModelV2 } from "@opencode-ai/core/model"
 import { ProviderV2 } from "@opencode-ai/core/provider"
@@ -161,6 +161,59 @@ const insertCorruptV2Message = (sessionID: SessionIDType, time = 1) =>
     ),
   )
 
+const insertLegacyMessageV2Assistant = (sessionID: SessionIDType, parentID: MessageID) =>
+  Effect.sync(() => {
+    Database.use((db) =>
+      db
+        .insert(MessageTable)
+        .values({
+          id: MessageID.ascending(),
+          session_id: sessionID,
+          time_created: 1,
+          time_updated: 1,
+          data: {
+            role: "assistant",
+            time: { created: 1, completed: 1 },
+            parentID,
+            modelID: ModelID.make("test"),
+            providerID: ProviderID.make("test"),
+            mode: "build",
+            path: { cwd: "/tmp", root: "/tmp" },
+            cost: 0,
+            tokens: {
+              input: 0,
+              output: 0,
+              reasoning: 0,
+              cache: { read: 0, write: 0 },
+            },
+          } as NonNullable<(typeof MessageTable.$inferInsert)["data"]>,
+        })
+        .run(),
+    )
+  })
+
+const insertLegacyMessageV2User = (sessionID: SessionIDType) =>
+  Effect.sync(() => {
+    const id = MessageID.ascending()
+    Database.use((db) =>
+      db
+        .insert(MessageTable)
+        .values({
+          id,
+          session_id: sessionID,
+          time_created: 1,
+          time_updated: 1,
+          data: {
+            role: "user",
+            time: { created: 1 },
+            model: { providerID: ProviderID.make("test"), modelID: ModelID.make("test") },
+          } as NonNullable<(typeof MessageTable.$inferInsert)["data"]>,
+        })
+        .run(),
+    )
+    return id
+  })
+
 const setLegacySummaryDiff = (sessionID: SessionIDType) =>
   Effect.sync(() =>
     Database.use((db) =>
@@ -611,6 +664,35 @@ describe("session HttpApi", () => {
     { git: true, config: { formatter: false, lsp: false } },
   )
 
+  it.instance(
+    "serves legacy messages missing agent",
+    () =>
+      Effect.gen(function* () {
+        const test = yield* TestInstance
+        const session = yield* createSession({ title: "legacy messages" })
+        const userID = yield* insertLegacyMessageV2User(session.id)
+        yield* insertLegacyMessageV2Assistant(session.id, userID)
+
+        const headers = { "x-opencode-directory": test.directory }
+        const response = yield* request(`${pathFor(SessionPaths.messages, { sessionID: session.id })}?limit=80`, {
+          headers,
+        })
+        const messages = yield* json<MessageV2.WithParts[]>(response)
+
+        expect(response.status).toBe(200)
+        expect(messages.find((item) => item.info.role === "user")?.info).toMatchObject({
+          role: "user",
+          agent: "build",
+          model: { providerID: "test", modelID: "test" },
+        })
+        expect(messages.find((item) => item.info.role === "assistant")?.info).toMatchObject({
+          role: "assistant",
+          agent: "build",
+        })
+      }),
+    { git: true, config: { formatter: false, lsp: false } },
+  )
+
   it.instance(
     "serves lifecycle mutation routes",
     () =>