diff --git a/README.md b/README.md
index 5c165a3..152f5b9 100644
--- a/README.md
+++ b/README.md
@@ -73,46 +73,57 @@ cd /home/worker/projects/prisma_platform
 - `http://127.0.0.1:7777/docs`
 - `http://127.0.0.1:7777/redoc`
 
-## Запуск сценария через HTTP
+## HTTP API
 
-- `POST http://127.0.0.1:7777/api/runs`
+### Запуск сценария (async)
 
-Тело запроса:
-
-```json
-{
-  "scenario_id": "news_source_discovery_v1",
-  "input": {
-    "url": "https://example.com/news"
-  }
-}
-```
-
-Пример:
+`POST /api/runs` — планирует выполнение сценария и **сразу** возвращает `run_id`. Само выполнение идёт в фоне.
 
 ```bash
 curl -s -X POST "http://127.0.0.1:7777/api/runs" \
   -H "Content-Type: application/json" \
   -d '{
     "scenario_id": "news_source_discovery_v1",
-    "input": {
-      "url": "https://example.com/news"
-    }
+    "input": { "url": "https://example.com/news" }
   }'
 ```
 
-Успешный ответ содержит:
+Ответ (`202 Accepted`):
 
-- `status=success`
-- `message=""`
-- список `steps` со статусами и временем шагов
-- `output_summary`
-- `result` итогового шага
+```json
+{
+  "run_id": "f3d9…",
+  "scenario_id": "news_source_discovery_v1",
+  "status": "queued",
+  "input": { "url": "..." },
+  "started_at": "2026-04-24T..."
+}
+```
 
-При ошибке:
+### Снапшот состояния
 
-- `status=failed`
-- `message` содержит текст ошибки
+`GET /api/runs/{run_id}` — текущее состояние: `status` (`queued|running|success|failed`), список `steps` со статусами (`success|failed|skipped|queued`), `result` и `output_summary` при завершении.
+
+### Live-прогресс (SSE)
+
+`GET /api/runs/{run_id}/events` — Server-Sent Events. Поздние подписчики получают replay уже накопленных событий, затем tail до завершения.
+
+```bash
+curl -N http://127.0.0.1:7777/api/runs/$RUN_ID/events
+```
+
+Типы событий:
+
+- `run_started` — `{run_id, scenario_id, started_at}`
+- `step_started` — `{run_id, step_name, index, started_at}`
+- `step_finished` — `{run_id, step_name, index, status, started_at, finished_at, message}`
+- `run_finished` — `{run_id, status, finished_at, message}` (терминальное, поток закрывается)
+
+### Каталоги
+
+- `GET /api/scenarios` — список сценариев с метаданными (`scenario_id`, `name`, `description`, `input_schema`).
+- `GET /api/scenarios/{scenario_id}` — полное определение сценария (для визуализации графа в UI).
+- `GET /api/tools` — MCP tool catalog: `[{name, description, input_schema}]` (проксируется на `MCP_BASE_URL`).
 
 ## Переменные окружения
 
@@ -148,6 +159,11 @@ MCP:
 - `MCP_BASE_URL` (default: `http://127.0.0.1:8081/mcp`)
 - `MCP_TIMEOUT_SECONDS` (default: `10`)
 
+Runtime caches:
+
+- `WORKFLOW_CACHE_MAX_SIZE` (default: `64`) — лимит LRU кэша построенных workflow.
+- `RUN_REGISTRY_MAX_SIZE` (default: `200`) — лимит LRU истории run'ов в памяти.
+
 Phoenix tracing:
 
 - `PHOENIX_TRACING_ENABLED` (default: `false`)
diff --git a/src/agent_os.py b/src/agent_os.py
index 3840953..4b37f49 100644
--- a/src/agent_os.py
+++ b/src/agent_os.py
@@ -18,6 +18,7 @@ from agno.os import AgentOS
 from src.agent_runner import get_agent
 from src.api_routes import router as api_router
 from src.observability import init_phoenix_tracing, is_phoenix_tracing_enabled
+from src.run_registry import get_registry
 
 load_dotenv()
 
@@ -29,6 +30,12 @@ async def _lifespan(_app: FastAPI):
     try:
         yield
     finally:
+        active = get_registry().list_active()
+        if active:
+            logger.info("Cancelling {} active run(s) on shutdown", len(active))
+            for record in active:
+                if record.task is not None and not record.task.done():
+                    record.task.cancel()
         logger.info("Prisma Platform API shutting down")
 
 
diff --git a/src/api_routes.py b/src/api_routes.py
index 505281b..2d1c65d 100644
--- a/src/api_routes.py
+++ b/src/api_routes.py
@@ -1,22 +1,279 @@
-"""REST routes for scenario execution.
+"""REST routes for scenario execution, catalogs and live run events.
 
-These endpoints live on the FastAPI ``base_app`` that AgentOS composes with
-its own routes, so the prefix ``/api`` does not collide with AgentOS paths.
+Runs are executed asynchronously: ``POST /api/runs`` schedules a background
+task and returns immediately with a ``run_id``. Clients consume progress
+via ``GET /api/runs/{run_id}/events`` (SSE) or poll
+``GET /api/runs/{run_id}`` for a snapshot.
 """
 
 from __future__ import annotations
 
-from fastapi import APIRouter
+import asyncio
+import json
+from typing import Any, AsyncIterator
 
-from src.mcp_workflow_runner import run_scenario
-from src.schemas import ScenarioRunRequest, ScenarioRunResponse
+from fastapi import APIRouter, HTTPException
+from fastapi.responses import StreamingResponse
+from loguru import logger
+
+from src.mcp_client import list_mcp_tools
+from src.mcp_workflow_runner import run_scenario_async
+from src.run_registry import RunRecord, get_registry
+from src.scenario_store import (
+    ScenarioStoreError,
+    list_scenario_summaries,
+    load_scenario_definition,
+)
+from src.schemas import (
+    RunSubmitResponse,
+    ScenarioRunRequest,
+    ScenarioRunResponse,
+    ScenarioSummary,
+    StepState,
+    ToolSummary,
+)
 
 router = APIRouter(prefix="/api", tags=["workflow"])
 
 
-@router.post("/runs", response_model=ScenarioRunResponse)
-async def post_run(request: ScenarioRunRequest) -> ScenarioRunResponse:
-    return await run_scenario(
+# ---------------------------------------------------------------------------
+# Runs
+# ---------------------------------------------------------------------------
+
+
+@router.post(
+    "/runs",
+    response_model=RunSubmitResponse,
+    status_code=202,
+    summary="Schedule a scenario run",
+    description=(
+        "Creates a run record and schedules execution in the background. "
+        "Returns immediately with a `run_id`; poll `GET /api/runs/{run_id}` "
+        "or subscribe to `GET /api/runs/{run_id}/events` for progress."
+    ),
+)
+async def post_run(request: ScenarioRunRequest) -> RunSubmitResponse:
+    registry = get_registry()
+    record = registry.create(
         scenario_id=request.scenario_id,
         input_data=request.input,
     )
+    record.task = asyncio.create_task(run_scenario_async(record))
+    return RunSubmitResponse(
+        run_id=record.run_id,
+        scenario_id=record.scenario_id,
+        status=record.status,
+        input=record.input,
+        started_at=record.started_at,
+    )
+
+
+@router.get(
+    "/runs/{run_id}",
+    response_model=ScenarioRunResponse,
+    summary="Get run snapshot",
+    description=(
+        "Returns the current state of a run. For running runs the `steps` "
+        "list reflects progress so far; for terminal runs it is complete."
+    ),
+    responses={404: {"description": "Unknown run_id"}},
+)
+async def get_run(run_id: str) -> ScenarioRunResponse:
+    record = _require_run(run_id)
+    if record.response is not None:
+        return record.response
+    return _snapshot_from_record(record)
+
+
+@router.get(
+    "/runs/{run_id}/events",
+    summary="Live run progress (SSE)",
+    description=(
+        "Server-Sent Events stream. Late subscribers receive a replay of "
+        "buffered events first, then tail new events until `run_finished`.\n\n"
+        "Event types: `run_started`, `step_started`, `step_finished`, "
+        "`run_finished`. Each event is JSON in the SSE `data:` field."
+    ),
+    responses={
+        200: {
+            "description": "SSE stream of run events",
+            "content": {
+                "text/event-stream": {
+                    "example": (
+                        "event: run_started\n"
+                        'data: {"type":"run_started","run_id":"76d6903c-f520-4a40-b0fc-8fed3f7955d2",'
+                        '"scenario_id":"news_source_discovery_v1","started_at":"2026-04-24T09:27:59.873+00:00"}\n\n'
+                        "event: step_started\n"
+                        'data: {"type":"step_started","run_id":"76d6903c-...","step_name":"search_news_sources",'
+                        '"index":0,"started_at":"2026-04-24T09:27:59.875+00:00"}\n\n'
+                        "event: step_finished\n"
+                        'data: {"type":"step_finished","run_id":"76d6903c-...","step_name":"search_news_sources",'
+                        '"index":0,"status":"success","started_at":"2026-04-24T09:27:59.875+00:00",'
+                        '"finished_at":"2026-04-24T09:28:00.028+00:00","message":""}\n\n'
+                        "event: run_finished\n"
+                        'data: {"type":"run_finished","run_id":"76d6903c-...","status":"success",'
+                        '"finished_at":"2026-04-24T09:28:01.750+00:00","message":""}\n\n'
+                    )
+                }
+            },
+        },
+        404: {"description": "Unknown run_id"},
+    },
+)
+async def get_run_events(run_id: str) -> StreamingResponse:
+    record = _require_run(run_id)
+    return StreamingResponse(
+        _event_stream(record),
+        media_type="text/event-stream",
+        headers={
+            "Cache-Control": "no-cache",
+            "X-Accel-Buffering": "no",
+        },
+    )
+
+
+# ---------------------------------------------------------------------------
+# Scenario catalog
+# ---------------------------------------------------------------------------
+
+
+@router.get(
+    "/scenarios",
+    response_model=list[ScenarioSummary],
+    summary="List available scenarios",
+    description="Returns metadata (id, name, description, input schema) for every scenario in the index.",
+)
+async def get_scenarios() -> list[ScenarioSummary]:
+    return [ScenarioSummary(**s) for s in list_scenario_summaries()]
+
+
+_SCENARIO_DEFINITION_EXAMPLE: dict[str, Any] = {
+    "schema_version": "1",
+    "scenario_id": "news_source_discovery_v1",
+    "name": "News Source Discovery V1",
+    "description": "Find earliest news source using sequential MCP tools.",
+    "input_schema": {
+        "type": "object",
+        "required": ["url"],
+        "properties": {
+            "url": {"type": "string", "description": "URL of source news article"}
+        },
+    },
+    "steps": [
+        {
+            "name": "search_news_sources",
+            "type": "tool",
+            "tool": "search_news_sources",
+            "input": {"url": {"from": "input.url"}},
+            "required_input_fields": ["url"],
+        }
+    ],
+}
+
+
+@router.get(
+    "/scenarios/{scenario_id}",
+    summary="Get full scenario definition",
+    description="Returns the raw scenario JSON (including the `steps` graph) for UI visualization.",
+    responses={
+        200: {
+            "description": "Scenario definition",
+            "content": {"application/json": {"example": _SCENARIO_DEFINITION_EXAMPLE}},
+        },
+        404: {"description": "Unknown scenario_id"},
+    },
+)
+async def get_scenario(scenario_id: str) -> dict[str, Any]:
+    try:
+        return load_scenario_definition(scenario_id)
+    except ScenarioStoreError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+
+
+# ---------------------------------------------------------------------------
+# Tool catalog
+# ---------------------------------------------------------------------------
+
+
+@router.get(
+    "/tools",
+    response_model=list[ToolSummary],
+    summary="List MCP tools",
+    description="Proxies MCP `list_tools()` and returns name, description, and input schema for each tool.",
+    responses={502: {"description": "MCP transport error"}},
+)
+async def get_tools() -> list[ToolSummary]:
+    try:
+        tools = await list_mcp_tools()
+    except RuntimeError as exc:
+        logger.warning("Failed to fetch MCP tools: {}", exc)
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
+    return [ToolSummary(**t) for t in tools]
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _require_run(run_id: str) -> RunRecord:
+    record = get_registry().get(run_id)
+    if record is None:
+        raise HTTPException(status_code=404, detail=f"Unknown run_id: {run_id}")
+    return record
+
+
+def _snapshot_from_record(record: RunRecord) -> ScenarioRunResponse:
+    """Build a partial ScenarioRunResponse for a still-running or pre-start run."""
+    steps: list[StepState] = []
+    for event in record.events:
+        if event.get("type") != "step_finished":
+            continue
+        steps.append(
+            StepState(
+                node_id=str(event.get("step_name", "")),
+                status=event.get("status", "failed"),
+                started_at=event.get("started_at"),
+                finished_at=event.get("finished_at"),
+                message=str(event.get("message", "")),
+            )
+        )
+    return ScenarioRunResponse(
+        scenario_id=record.scenario_id,
+        status=record.status,
+        message=record.message,
+        input=record.input,
+        steps=steps,
+        run_id=record.run_id,
+    )
+
+
+async def _event_stream(record: RunRecord) -> AsyncIterator[bytes]:
+    """Replay buffered events, then tail a fresh subscriber queue.
+
+    The snapshot/subscribe pair runs without any intervening ``await``, so no
+    emitted event can slip between the replay cutoff and the subscription.
+    Events emitted during replay land in the queue and are drained afterwards.
+    """
+    queue: asyncio.Queue = asyncio.Queue()
+    buffered = list(record.events)
+    record.subscribers.append(queue)
+    try:
+        for event in buffered:
+            yield _format_sse(event)
+        if record.is_terminal():
+            return
+        while True:
+            event = await queue.get()
+            if event is None:
+                return
+            yield _format_sse(event)
+    finally:
+        if queue in record.subscribers:
+            record.subscribers.remove(queue)
+
+
+def _format_sse(event: dict[str, Any]) -> bytes:
+    event_type = str(event.get("type", "message"))
+    payload = json.dumps(event, ensure_ascii=False)
+    return f"event: {event_type}\ndata: {payload}\n\n".encode("utf-8")
diff --git a/src/mcp_client.py b/src/mcp_client.py
index 26cccd3..2172715 100644
--- a/src/mcp_client.py
+++ b/src/mcp_client.py
@@ -63,3 +63,34 @@ async def call_mcp_tool(tool_name: str, arguments: dict[str, Any]) -> dict[str,
             return parsed
 
     raise RuntimeError(f"MCP tool returned invalid payload: {tool_name}")
+
+
+async def list_mcp_tools() -> list[dict[str, Any]]:
+    """Fetch the MCP tool catalog as plain dicts for API serialization."""
+    try:
+        async with streamablehttp_client(url=_mcp_url()) as session_params:
+            read, write = session_params[0:2]
+            async with ClientSession(
+                read,
+                write,
+                read_timeout_seconds=timedelta(seconds=_timeout_seconds()),
+            ) as session:
+                await session.initialize()
+                result = await session.list_tools()
+    except TimeoutError as exc:
+        logger.warning("MCP list_tools timeout")
+        raise RuntimeError("MCP list_tools timeout") from exc
+    except Exception as exc:
+        logger.exception("MCP list_tools transport error")
+        raise RuntimeError("MCP list_tools transport error") from exc
+
+    tools: list[dict[str, Any]] = []
+    for tool in result.tools:
+        tools.append(
+            {
+                "name": tool.name,
+                "description": tool.description,
+                "input_schema": tool.inputSchema,
+            }
+        )
+    return tools
diff --git a/src/mcp_workflow_runner.py b/src/mcp_workflow_runner.py
index d9868bd..e921a9c 100644
--- a/src/mcp_workflow_runner.py
+++ b/src/mcp_workflow_runner.py
@@ -8,6 +8,7 @@ missing fields, invokes the tool, and collects per-step results back into
 
 from __future__ import annotations
 
+import asyncio
 from collections import OrderedDict
 from copy import deepcopy
 from datetime import datetime, timezone
@@ -20,7 +21,15 @@ from agno.workflow.workflow import Workflow
 from loguru import logger
 
 from src.mcp_client import call_mcp_tool
-from src.schemas import ScenarioRunResponse, StepState
+from src.run_registry import EventEmitter, RunRecord
+from src.schemas import (
+    RunFinishedEvent,
+    RunStartedEvent,
+    ScenarioRunResponse,
+    StepFinishedEvent,
+    StepStartedEvent,
+    StepState,
+)
 from src.scenario_store import ScenarioStoreError, load_scenario_definition
 from src.step_planner import plan_arguments, planner_enabled
 from src.template import (
@@ -99,6 +108,7 @@ async def _execute_one_call(
 
 def _build_tool_executor(
     step_spec: dict[str, Any],
+    step_index: int = 0,
 ) -> Callable[[StepInput, dict[str, Any]], Awaitable[StepOutput]]:
     step_name = str(step_spec["name"])
     tool_name = str(step_spec["tool"])
@@ -120,6 +130,18 @@ def _build_tool_executor(
     async def executor(_step_input: StepInput, session_state: dict[str, Any]) -> StepOutput:
         started_at = _utc_now_iso()
         scope = _build_scope(session_state)
+        emitter: EventEmitter | None = session_state.get("_emitter")
+        run_id: str = session_state.get("_run_id", "")
+
+        if emitter is not None:
+            await emitter.emit(
+                StepStartedEvent(
+                    run_id=run_id,
+                    step_name=step_name,
+                    index=step_index,
+                    started_at=started_at,
+                ).model_dump()
+            )
 
         try:
             if foreach_from:
@@ -189,6 +211,17 @@ def _build_tool_executor(
                 }
 
             session_state.setdefault("steps", {})[step_name] = step_payload
+            if emitter is not None:
+                await emitter.emit(
+                    StepFinishedEvent(
+                        run_id=run_id,
+                        step_name=step_name,
+                        index=step_index,
+                        status="success",
+                        started_at=started_at,
+                        finished_at=step_payload["finished_at"],
+                    ).model_dump()
+                )
             return StepOutput(
                 content=json.dumps(step_payload, ensure_ascii=False),
                 success=True,
@@ -204,6 +237,18 @@ def _build_tool_executor(
             }
             session_state.setdefault("steps", {})[step_name] = error_payload
             logger.exception("Step {} failed (tool={})", step_name, tool_name)
+            if emitter is not None:
+                await emitter.emit(
+                    StepFinishedEvent(
+                        run_id=run_id,
+                        step_name=step_name,
+                        index=step_index,
+                        status="failed",
+                        started_at=started_at,
+                        finished_at=finished_at,
+                        message=str(exc),
+                    ).model_dump()
+                )
             raise RuntimeError(f"{step_name} failed: {exc}") from exc
 
     return executor
@@ -215,7 +260,7 @@ def _build_workflow(scenario_id: str, scenario: dict[str, Any]) -> Workflow:
         raise ScenarioStoreError("Scenario must contain non-empty steps list")
 
     workflow_steps: list[Step] = []
-    for raw_step in raw_steps:
+    for step_index, raw_step in enumerate(raw_steps):
         if not isinstance(raw_step, dict):
             raise ScenarioStoreError("Each scenario step must be object")
         if raw_step.get("type") != "tool":
@@ -233,7 +278,7 @@ def _build_workflow(scenario_id: str, scenario: dict[str, Any]) -> Workflow:
             Step(
                 name=step_name,
                 description=str(raw_step.get("description", step_name)),
-                executor=_build_tool_executor(raw_step),
+                executor=_build_tool_executor(raw_step, step_index=step_index),
                 max_retries=0,
                 on_error="fail",
             )
@@ -320,6 +365,8 @@ async def run_scenario(
     *,
     scenario_id: str,
     input_data: dict[str, Any],
+    emitter: EventEmitter | None = None,
+    run_id: str = "",
 ) -> ScenarioRunResponse:
     try:
         scenario = load_scenario_definition(scenario_id)
@@ -329,6 +376,7 @@ async def run_scenario(
             status="failed",
             message=str(exc),
             input=input_data,
+            run_id=run_id or None,
         )
 
     scenario_name = str(scenario.get("name", scenario_id))
@@ -341,12 +389,15 @@ async def run_scenario(
             message=str(exc),
             input=input_data,
             scenario_name=scenario_name,
+            run_id=run_id or None,
         )
 
     # Fresh per-run state that Agno owns during arun(..., session_state=...).
     session_state: dict[str, Any] = {
         "input": deepcopy(input_data),
         "steps": {},
+        "_emitter": emitter,
+        "_run_id": run_id,
     }
 
     workflow_error: str | None = None
@@ -404,6 +455,75 @@ async def run_scenario(
         scenario_name=scenario_name,
         workflow_name=workflow.name,
         result=result,
-        run_id=str(getattr(run_output, "run_id", "")) or None,
+        run_id=run_id or str(getattr(run_output, "run_id", "")) or None,
         session_id=str(getattr(run_output, "session_id", "")) or None,
     )
+
+
+async def run_scenario_async(record: RunRecord) -> None:
+    """Execute a scenario inside a background task, emitting SSE events.
+
+    Lifecycle:
+      queued → running (run_started) → success|failed (run_finished) → sentinel
+    """
+    emitter = EventEmitter(record)
+    record.status = "running"
+    record.started_at = _utc_now_iso()
+
+    try:
+        await emitter.emit(
+            RunStartedEvent(
+                run_id=record.run_id,
+                scenario_id=record.scenario_id,
+                started_at=record.started_at,
+            ).model_dump()
+        )
+
+        response = await run_scenario(
+            scenario_id=record.scenario_id,
+            input_data=record.input,
+            emitter=emitter,
+            run_id=record.run_id,
+        )
+
+        record.response = response
+        record.status = response.status
+        record.message = response.message
+        record.finished_at = _utc_now_iso()
+
+        await emitter.emit(
+            RunFinishedEvent(
+                run_id=record.run_id,
+                status=response.status,
+                finished_at=record.finished_at,
+                message=response.message,
+            ).model_dump()
+        )
+    except asyncio.CancelledError:
+        record.status = "failed"
+        record.message = "cancelled"
+        record.finished_at = _utc_now_iso()
+        await emitter.emit(
+            RunFinishedEvent(
+                run_id=record.run_id,
+                status="failed",
+                finished_at=record.finished_at,
+                message="cancelled",
+            ).model_dump()
+        )
+        raise
+    except Exception as exc:
+        logger.exception("Run {} crashed", record.run_id)
+        record.status = "failed"
+        record.message = str(exc)
+        record.finished_at = _utc_now_iso()
+        await emitter.emit(
+            RunFinishedEvent(
+                run_id=record.run_id,
+                status="failed",
+                finished_at=record.finished_at,
+                message=str(exc),
+            ).model_dump()
+        )
+    finally:
+        await emitter.close()
diff --git a/src/run_registry.py b/src/run_registry.py
new file mode 100644
index 0000000..c45f57c
--- /dev/null
+++ b/src/run_registry.py
@@ -0,0 +1,126 @@
+"""In-memory registry of scenario runs and their event streams.
+
+Each submitted run gets a ``RunRecord`` holding:
+
+- mutable status / partial step state updated by the workflow runner;
+- an append-only event log (used to replay history to late SSE subscribers);
+- a live asyncio queue that SSE endpoints tail until a terminal ``None``
+  sentinel is delivered.
+
+The registry is an LRU with ``RUN_REGISTRY_MAX_SIZE`` bound so long-running
+processes do not leak run history.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import os
+import uuid
+from collections import OrderedDict
+from dataclasses import dataclass, field
+from datetime import datetime, timezone
+from typing import Any
+
+from loguru import logger
+
+from src.schemas import ScenarioRunResponse
+
+
+_TERMINAL_STATUSES = {"success", "failed"}
+
+
+def _utc_now_iso() -> str:
+    return datetime.now(timezone.utc).isoformat()
+
+
+def _env_int(name: str, default: int) -> int:
+    value = os.getenv(name)
+    return int(value) if value is not None else default
+
+
+@dataclass
+class RunRecord:
+    run_id: str
+    scenario_id: str
+    input: dict[str, Any]
+    status: str = "queued"
+    started_at: str = field(default_factory=_utc_now_iso)
+    finished_at: str | None = None
+    message: str = ""
+    response: ScenarioRunResponse | None = None
+    events: list[dict[str, Any]] = field(default_factory=list)
+    subscribers: list[asyncio.Queue] = field(default_factory=list)
+    task: asyncio.Task | None = None
+
+    def is_terminal(self) -> bool:
+        return self.status in _TERMINAL_STATUSES
+
+
+class EventEmitter:
+    """Fans events out to every live SSE subscriber plus the replay buffer.
+
+    Subscribers are ``asyncio.Queue`` instances registered by SSE endpoints;
+    ``None`` is used as a terminal sentinel so consumers can exit cleanly.
+    """
+
+    def __init__(self, record: RunRecord) -> None:
+        self._record = record
+
+    async def emit(self, event: dict[str, Any]) -> None:
+        self._record.events.append(event)
+        for queue in list(self._record.subscribers):
+            queue.put_nowait(event)
+
+    async def close(self) -> None:
+        for queue in list(self._record.subscribers):
+            queue.put_nowait(None)
+
+
+class RunRegistry:
+    def __init__(self, max_size: int | None = None) -> None:
+        self._records: "OrderedDict[str, RunRecord]" = OrderedDict()
+        self._max_size = max_size or _env_int("RUN_REGISTRY_MAX_SIZE", 200)
+
+    def create(self, *, scenario_id: str, input_data: dict[str, Any]) -> RunRecord:
+        run_id = str(uuid.uuid4())
+        record = RunRecord(
+            run_id=run_id,
+            scenario_id=scenario_id,
+            input=input_data,
+        )
+        self._records[run_id] = record
+        self._evict_if_needed()
+        logger.info("Run {} created for scenario={}", run_id, scenario_id)
+        return record
+
+    def get(self, run_id: str) -> RunRecord | None:
+        record = self._records.get(run_id)
+        if record is not None:
+            self._records.move_to_end(run_id)
+        return record
+
+    def list_active(self) -> list[RunRecord]:
+        return [r for r in self._records.values() if not r.is_terminal()]
+
+    def _evict_if_needed(self) -> None:
+        while len(self._records) > self._max_size:
+            evicted_id, evicted = self._records.popitem(last=False)
+            if evicted.task is not None and not evicted.task.done():
+                # Refuse to silently drop an in-flight run — re-insert and stop.
+                self._records[evicted_id] = evicted
+                self._records.move_to_end(evicted_id, last=False)
+                logger.warning(
+                    "Run registry at capacity {} but oldest run is still active; "
+                    "not evicting {}",
+                    self._max_size,
+                    evicted_id,
+                )
+                return
+            logger.debug("Evicted run {} from registry", evicted_id)
+
+
+_registry = RunRegistry()
+
+
+def get_registry() -> RunRegistry:
+    return _registry
diff --git a/src/scenario_store.py b/src/scenario_store.py
index 6f9c8d5..5342a0b 100644
--- a/src/scenario_store.py
+++ b/src/scenario_store.py
@@ -65,3 +65,23 @@ def load_scenario_definition(scenario_id: str) -> dict[str, Any]:
             "Scenario file scenario_id does not match requested scenario_id"
         )
     return scenario
+
+
+def list_scenario_summaries() -> list[dict[str, Any]]:
+    """Return metadata for every scenario in the index (no steps)."""
+    summaries: list[dict[str, Any]] = []
+    for scenario_id in load_scenario_index().keys():
+        try:
+            scenario = load_scenario_definition(scenario_id)
+        except ScenarioStoreError:
+            # Broken entry in the index should not take the whole catalog down.
+            continue
+        summaries.append(
+            {
+                "scenario_id": scenario_id,
+                "name": scenario.get("name"),
+                "description": scenario.get("description"),
+                "input_schema": scenario.get("input_schema"),
+            }
+        )
+    return summaries
diff --git a/src/schemas.py b/src/schemas.py
index a04bcfe..d3083c9 100644
--- a/src/schemas.py
+++ b/src/schemas.py
@@ -8,12 +8,24 @@ from pydantic import BaseModel, Field
 
 RunStatus = Literal["queued", "running", "success", "failed", "waiting_human"]
 StepStatus = Literal["queued", "running", "success", "failed", "skipped", "waiting_human"]
+EventType = Literal["run_started", "step_started", "step_finished", "run_finished"]
 
 
 class ScenarioRunRequest(BaseModel):
     scenario_id: str = "news_source_discovery_v1"
     input: dict[str, Any] = Field(default_factory=dict)
 
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "scenario_id": "news_source_discovery_v1",
+                    "input": {"url": "https://example.com/news/article"},
+                }
+            ]
+        }
+    }
+
 
 class StepState(BaseModel):
     node_id: str
@@ -22,6 +34,20 @@ class StepState(BaseModel):
     finished_at: str | None = None
     message: str = ""
 
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "node_id": "search_news_sources",
+                    "status": "success",
+                    "started_at": "2026-04-24T09:27:59.875680+00:00",
+                    "finished_at": "2026-04-24T09:28:00.028730+00:00",
+                    "message": "",
+                }
+            ]
+        }
+    }
+
 
 class ScenarioRunResponse(BaseModel):
     scenario_id: str
@@ -35,3 +61,218 @@ class ScenarioRunResponse(BaseModel):
     result: dict[str, Any] | None = None
     run_id: str | None = None
     session_id: str | None = None
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "scenario_id": "news_source_discovery_v1",
+                    "status": "success",
+                    "message": "",
+                    "input": {"url": "https://example.com/news/article"},
+                    "steps": [
+                        {
+                            "node_id": "search_news_sources",
+                            "status": "success",
+                            "started_at": "2026-04-24T09:27:59.875680+00:00",
+                            "finished_at": "2026-04-24T09:28:00.028730+00:00",
+                            "message": "",
+                        },
+                        {
+                            "node_id": "generate_summary",
+                            "status": "success",
+                            "started_at": "2026-04-24T09:28:00.781744+00:00",
+                            "finished_at": "2026-04-24T09:28:00.879028+00:00",
+                            "message": "",
+                        },
+                    ],
+                    "output_summary": "Самым ранним источником считается https://news-a.example/article-1",
+                    "scenario_name": "News Source Discovery V1",
+                    "workflow_name": "news_source_discovery_v1",
+                    "result": {
+                        "ok": True,
+                        "tool_name": "generate_summary",
+                        "payload": {
+                            "input_count": 3,
+                            "summary": "Самым ранним источником считается https://news-a.example/article-1",
+                        },
+                    },
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "session_id": None,
+                }
+            ]
+        }
+    }
+
+
+class RunSubmitResponse(BaseModel):
+    run_id: str
+    scenario_id: str
+    status: RunStatus
+    input: dict[str, Any]
+    started_at: str
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "scenario_id": "news_source_discovery_v1",
+                    "status": "queued",
+                    "input": {"url": "https://example.com/news/article"},
+                    "started_at": "2026-04-24T09:27:59.873049+00:00",
+                }
+            ]
+        }
+    }
+
+
+class ScenarioSummary(BaseModel):
+    scenario_id: str
+    name: str | None = None
+    description: str | None = None
+    input_schema: dict[str, Any] | None = None
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "scenario_id": "news_source_discovery_v1",
+                    "name": "News Source Discovery V1",
+                    "description": "Find earliest news source using sequential MCP tools.",
+                    "input_schema": {
+                        "type": "object",
+                        "required": ["url"],
+                        "properties": {
+                            "url": {
+                                "type": "string",
+                                "description": "URL of source news article",
+                            }
+                        },
+                    },
+                }
+            ]
+        }
+    }
+
+
+class ToolSummary(BaseModel):
+    name: str
+    description: str | None = None
+    input_schema: dict[str, Any] | None = None
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "name": "search_news_sources",
+                    "description": "Search for candidate news source URLs for a given article.",
+                    "input_schema": {
+                        "type": "object",
+                        "required": ["url"],
+                        "properties": {
+                            "url": {"type": "string", "title": "Url"}
+                        },
+                        "title": "search_news_sourcesArguments",
+                    },
+                }
+            ]
+        }
+    }
+
+
+# ---------------------------------------------------------------------------
+# SSE event models. Client parses by the `type` field.
+# ---------------------------------------------------------------------------
+
+
+class RunStartedEvent(BaseModel):
+    type: Literal["run_started"] = "run_started"
+    run_id: str
+    scenario_id: str
+    started_at: str
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "type": "run_started",
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "scenario_id": "news_source_discovery_v1",
+                    "started_at": "2026-04-24T09:27:59.873397+00:00",
+                }
+            ]
+        }
+    }
+
+
+class StepStartedEvent(BaseModel):
+    type: Literal["step_started"] = "step_started"
+    run_id: str
+    step_name: str
+    index: int
+    started_at: str
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "type": "step_started",
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "step_name": "search_news_sources",
+                    "index": 0,
+                    "started_at": "2026-04-24T09:27:59.875680+00:00",
+                }
+            ]
+        }
+    }
+
+
+class StepFinishedEvent(BaseModel):
+    type: Literal["step_finished"] = "step_finished"
+    run_id: str
+    step_name: str
+    index: int
+    status: StepStatus
+    started_at: str | None = None
+    finished_at: str | None = None
+    message: str = ""
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "type": "step_finished",
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "step_name": "search_news_sources",
+                    "index": 0,
+                    "status": "success",
+                    "started_at": "2026-04-24T09:27:59.875680+00:00",
+                    "finished_at": "2026-04-24T09:28:00.028730+00:00",
+                    "message": "",
+                }
+            ]
+        }
+    }
+
+
+class RunFinishedEvent(BaseModel):
+    type: Literal["run_finished"] = "run_finished"
+    run_id: str
+    status: RunStatus
+    finished_at: str
+    message: str = ""
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "type": "run_finished",
+                    "run_id": "76d6903c-f520-4a40-b0fc-8fed3f7955d2",
+                    "status": "success",
+                    "finished_at": "2026-04-24T09:28:01.750206+00:00",
+                    "message": "",
+                }
+            ]
+        }
+    }