diff --git a/litellm/managed_agents/endpoints/messages.py b/litellm/managed_agents/endpoints/messages.py
new file mode 100644
index 00000000000..1a12d5ee034
--- /dev/null
+++ b/litellm/managed_agents/endpoints/messages.py
@@ -0,0 +1,298 @@
+"""Messaging endpoints for managed agents v2.
+
+Implements `POST /v2/sessions/:id/messages` (LIT-2920) and
+`GET /v2/sessions/:id/messages` (LIT-2920) per contract §6.4 / §6.5.
+
+Both endpoints share the same pre-forward checks (contract §7):
+  1. Auth (handled by Depends).
+  2. Session row exists for caller → 404 if missing.
+  3. session.status == "ready" → else 503 (provisioning) or 404
+     (terminated/error).
+  4. Resolve sandbox_url + opencode_session_id from row.
+
+The user message is NOT persisted in our DB for v2 — opencode is the
+source of truth. The returned `msg_*` id is a local handle; subsequent
+GETs reflect opencode's state.
+
+The SSE `/events` endpoint is owned by a separate module — do not add it
+here.
+"""
+
+from datetime import datetime, timezone
+from typing import Any, Dict, Optional
+
+from fastapi import APIRouter, Depends, HTTPException, Query
+
+from litellm.managed_agents.adapters.base import (
+    SandboxBadGatewayError,
+    SandboxUnreachableError,
+)
+from litellm.managed_agents.adapters.registry import get_adapter
+from litellm.managed_agents.db import get_agent, get_session
+from litellm.managed_agents.id_utils import new_message_id
+from litellm.managed_agents.types import (
+    CreateMessageRequest,
+    MessageList,
+    MessageRow,
+)
+from litellm.proxy._types import CommonProxyErrors, UserAPIKeyAuth
+from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
+
+router = APIRouter()
+
+
+# ---------------------------------------------------------------------------
+# Shared helpers
+# ---------------------------------------------------------------------------
+
+
+async def _load_ready_session(
+    session_id: str,
+    created_by: Optional[str],
+) -> Dict[str, Any]:
+    """Load the session row for a caller, validating it is `ready`.
+
+    Returns the session row as a plain dict. Raises HTTPException with the
+    correct status code per contract §7:
+      - 500 if the prisma client is not connected.
+      - 404 if the session does not exist for this caller.
+      - 503 if the session is still provisioning (Retry-After: 5).
+      - 404 if the session is terminated or in an error state.
+
+    The 503 case carries a `Retry-After: 5` header per contract §7
+    "Failure modes — Session still provisioning".
+    """
+    from litellm.proxy.proxy_server import prisma_client
+
+    if prisma_client is None:
+        raise HTTPException(
+            status_code=500,
+            detail={"error": CommonProxyErrors.db_not_connected_error.value},
+        )
+
+    session = await get_session(
+        prisma_client=prisma_client,
+        session_id=session_id,
+        created_by=created_by,
+    )
+    if not session:
+        raise HTTPException(
+            status_code=404,
+            detail=f"Session {session_id} not found",
+        )
+
+    status = session.get("status")
+    if status == "provisioning":
+        raise HTTPException(
+            status_code=503,
+            detail="Session not ready",
+            headers={"Retry-After": "5"},
+        )
+    if status != "ready":
+        # terminated, error, or unknown → present as 404 to the caller
+        # (contract §7: "Session terminated → 404").
+        raise HTTPException(
+            status_code=404,
+            detail=f"Session {session_id} not found",
+        )
+
+    return session
+
+
+def _resolve_sandbox(session: Dict[str, Any]) -> Dict[str, Any]:
+    """Extract the `sandbox_url` and `opencode_session_id` from the row.
+
+    Raises 502 if the row is in `ready` state but missing required
+    sandbox routing fields — that indicates a bad-gateway condition where
+    the session row is internally inconsistent.
+    """
+    sandbox_url = session.get("sandbox_url")
+    metadata = session.get("sandbox_metadata") or {}
+    if not isinstance(metadata, dict):
+        metadata = {}
+    opencode_session_id = metadata.get("opencode_session_id")
+
+    if not sandbox_url or not opencode_session_id:
+        raise HTTPException(
+            status_code=502,
+            detail={"error": "Bad gateway"},
+        )
+
+    return {
+        "sandbox_url": sandbox_url,
+        "opencode_session_id": opencode_session_id,
+        "sandbox_type": session.get("sandbox_type", "opencode"),
+    }
+
+
+async def _resolve_model(
+    session: Dict[str, Any],
+    request_model: Optional[str],
+    created_by: Optional[str],
+) -> Optional[str]:
+    """Pick the model to use: request override, else agent default.
+
+    Returns None only if neither side provides a model — opencode tolerates
+    a None model by falling back to its own default, so we don't enforce
+    presence here.
+    """
+    if request_model:
+        return request_model
+
+    from litellm.proxy.proxy_server import prisma_client
+
+    if prisma_client is None:
+        return None
+
+    agent_id = session.get("agent_id")
+    if not agent_id:
+        return None
+
+    agent = await get_agent(
+        prisma_client=prisma_client,
+        agent_id=agent_id,
+        created_by=created_by,
+    )
+    if not agent:
+        return None
+
+    config = agent.get("config") or {}
+    if not isinstance(config, dict):
+        return None
+    model = config.get("model")
+    return model if isinstance(model, str) and model else None
+
+
+# ---------------------------------------------------------------------------
+# POST /v2/sessions/:id/messages
+# ---------------------------------------------------------------------------
+
+
+@router.post(
+    "/v2/sessions/{session_id}/messages",
+    response_model=MessageRow,
+    status_code=202,
+    tags=["managed-agents"],
+)
+async def send_message(
+    session_id: str,
+    request: CreateMessageRequest,
+    user_api_key_dict: UserAPIKeyAuth = Depends(user_api_key_auth),
+) -> MessageRow:
+    """Forward a user message to the sandbox. Returns 202 with a
+    synthesized user `MessageRow` whose `status` is `in_progress`.
+
+    The actual assistant response streams via the SSE
+    `/v2/sessions/:id/events` endpoint (owned by a separate module).
+    """
+    session = await _load_ready_session(
+        session_id=session_id,
+        created_by=user_api_key_dict.user_id,
+    )
+    sandbox = _resolve_sandbox(session)
+
+    try:
+        adapter = get_adapter(sandbox["sandbox_type"])
+    except ValueError as e:
+        raise HTTPException(status_code=422, detail=str(e)) from e
+
+    model_to_use = await _resolve_model(
+        session=session,
+        request_model=request.model,
+        created_by=user_api_key_dict.user_id,
+    )
+
+    try:
+        await adapter.send_message(
+            sandbox["sandbox_url"],
+            sandbox["opencode_session_id"],
+            request.content,
+            model_to_use,
+        )
+    except SandboxUnreachableError as e:
+        raise HTTPException(
+            status_code=504,
+            detail={"error": "Sandbox unreachable"},
+        ) from e
+    except SandboxBadGatewayError as e:
+        raise HTTPException(
+            status_code=502,
+            detail={"error": "Bad gateway"},
+        ) from e
+
+    now = datetime.now(timezone.utc)
+    return MessageRow(
+        id=new_message_id(),
+        session_id=session_id,
+        role="user",
+        content=request.content,
+        model=model_to_use,
+        status="in_progress",
+        created_at=now,
+        completed_at=None,
+    )
+
+
+# ---------------------------------------------------------------------------
+# GET /v2/sessions/:id/messages
+# ---------------------------------------------------------------------------
+
+
+@router.get(
+    "/v2/sessions/{session_id}/messages",
+    response_model=MessageList,
+    tags=["managed-agents"],
+)
+async def list_messages(
+    session_id: str,
+    limit: int = Query(default=50, ge=1, le=500),
+    cursor: Optional[str] = Query(default=None),
+    role: Optional[str] = Query(default=None, pattern="^(user|assistant)$"),
+    user_api_key_dict: UserAPIKeyAuth = Depends(user_api_key_auth),
+) -> MessageList:
+    """Return the message history for a session.
+
+    Forwards to the sandbox adapter, normalizes the result, and applies
+    the optional `role` filter in-memory. Pagination is a future
+    enhancement — for MVP `next_cursor` is None and `has_more` is False
+    (contract §6.5 explicitly defers opencode pagination).
+    """
+    _ = cursor  # MVP: opencode pagination is deferred.
+
+    session = await _load_ready_session(
+        session_id=session_id,
+        created_by=user_api_key_dict.user_id,
+    )
+    sandbox = _resolve_sandbox(session)
+
+    try:
+        adapter = get_adapter(sandbox["sandbox_type"])
+    except ValueError as e:
+        raise HTTPException(status_code=422, detail=str(e)) from e
+
+    try:
+        messages = await adapter.list_messages(
+            sandbox["sandbox_url"],
+            sandbox["opencode_session_id"],
+            session_id,
+            limit,
+        )
+    except SandboxUnreachableError as e:
+        raise HTTPException(
+            status_code=504,
+            detail={"error": "Sandbox unreachable"},
+        ) from e
+    except SandboxBadGatewayError as e:
+        raise HTTPException(
+            status_code=502,
+            detail={"error": "Bad gateway"},
+        ) from e
+
+    if role:
+        messages = [m for m in messages if m.role == role]
+
+    return MessageList(
+        data=messages,
+        next_cursor=None,
+        has_more=False,
+    )