2026-09-06 22:47:45 +00:00 · 2026-09-06 22:47:45 +00:00 · 96c0da33c7
commit 96c0da33c7
parent e178ae406d
15 changed files with 5070 additions and 5 deletions
--- a/.devcontainer/docker-compose.yml
+++ b/.devcontainer/docker-compose.yml
@ -68,6 +68,8 @@ services:
    build:
      context: .
      dockerfile: Dockerfile.lfx
+    env_file:
+      - ../.env
    volumes:
      - lfx-data:/flows
    ports:
--- a/.env.example
+++ b/.env.example
@ -19,6 +19,10 @@ LANGFLOW_DATABASE_URL=postgresql://kirche:<password>@db:5432/langflow

 # --- lfx (flow runtime) ---
 LFX_URL=http://lfx:6004
+LFX_API_KEY=lfx-
+
+# --- API self-reference for flow callbacks (must be reachable FROM lfx) ---
+CALLBACK_BASE_URL=http://app:8000

 # --- LLM (optional; tests mock the provider without it) ---
 # LLM_API_KEY=
--- a/backend/app/flows/init.py
+++ b/backend/app/flows/init.py
--- a/backend/app/flows/api.py
+++ b/backend/app/flows/api.py
@ -0,0 +1,311 @@
+"""Flows + approvals HTTP API."""
+
+from __future__ import annotations
+
+import json
+from collections.abc import AsyncIterator, Iterator
+from uuid import UUID
+
+import httpx
+from fastapi import APIRouter, Depends, HTTPException, Query
+from fastapi.responses import StreamingResponse
+from sqlmodel import Session
+
+from app.db import get_engine, get_session
+from app.settings import settings
+
+from . import runner, store
+from .lfx_client import (
+    LfxClient,
+    LfxConflict,
+    LfxError,
+    LfxInvalidFlow,
+    LfxNotFound,
+    LfxRunFailed,
+    LfxUnavailable,
+)
+from .schemas import (
+    ApprovalCreate,
+    ApprovalRead,
+    FlowDefinitionCreate,
+    FlowDefinitionRead,
+    FlowVersionCreate,
+    FlowVersionRead,
+    RunRead,
+    RunRequest,
+)
+
+flows_router = APIRouter(prefix="/api/flows", tags=["flows"])
+approvals_router = APIRouter(prefix="/api/approvals", tags=["approvals"])
+
+
+def get_db() -> Iterator[Session]:
+    yield from get_session()
+
+
+def get_lfx() -> LfxClient:
+    return LfxClient(settings.lfx_url, api_key=settings.lfx_api_key or None)
+
+
+def _read_definition(d) -> FlowDefinitionRead:
+    return FlowDefinitionRead(
+        id=d.id,
+        name=d.name,
+        description=d.description,
+        status=d.status,
+        continuation_flow_id=d.continuation_flow_id,
+        created_at=d.created_at,
+    )
+
+
+def _read_version(v) -> FlowVersionRead:
+    return FlowVersionRead(
+        id=v.id,
+        flow_id=v.flow_id,
+        version_no=v.version_no,
+        langflow_json=v.langflow_json,
+        lfx_flow_id=v.lfx_flow_id,
+        deployed_at=v.deployed_at,
+        author=v.author,
+        created_at=v.created_at,
+    )
+
+
+def _read_run(r) -> RunRead:
+    return RunRead(
+        id=r.id,
+        version_id=r.version_id,
+        tenant_id=r.tenant_id,
+        status=r.status,
+        input=r.input,
+        output=r.output,
+        session_id=r.session_id,
+        created_at=r.created_at,
+        finished_at=r.finished_at,
+    )
+
+
+def _read_task(t) -> ApprovalRead:
+    return ApprovalRead(
+        id=t.id,
+        run_id=t.run_id,
+        version_id=t.version_id,
+        tenant_id=t.tenant_id,
+        title=t.title,
+        payload=t.payload,
+        continuation_flow_id=t.continuation_flow_id,
+        approver=t.approver,
+        status=t.status,
+        decision_note=t.decision_note,
+        created_at=t.created_at,
+        decided_at=t.decided_at,
+    )
+
+
+@flows_router.post("", response_model=FlowDefinitionRead, status_code=201)
+def create_flow(data: FlowDefinitionCreate, session: Session = Depends(get_db)):
+    try:
+        return _read_definition(store.create_definition(session, data))
+    except store.ConflictError as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
+    except store.InvalidError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+
+
+@flows_router.get("", response_model=list[FlowDefinitionRead])
+def list_flows(session: Session = Depends(get_db)):
+    return [_read_definition(d) for d in store.list_definitions(session)]
+
+
+@flows_router.get("/{flow_id}", response_model=FlowDefinitionRead)
+def get_flow(flow_id: UUID, session: Session = Depends(get_db)):
+    try:
+        return _read_definition(store.get_definition(session, flow_id))
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+
+
+@flows_router.post(
+    "/{flow_id}/versions", response_model=FlowVersionRead, status_code=201
+)
+def create_version(
+    flow_id: UUID, data: FlowVersionCreate, session: Session = Depends(get_db)
+):
+    try:
+        return _read_version(store.create_version(session, flow_id, data))
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+    except store.InvalidError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+
+
+@flows_router.get("/{flow_id}/versions", response_model=list[FlowVersionRead])
+def list_versions(flow_id: UUID, session: Session = Depends(get_db)):
+    try:
+        return [_read_version(v) for v in store.list_versions(session, flow_id)]
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+
+
+@flows_router.post(
+    "/{flow_id}/versions/{version_no}/deploy", response_model=FlowVersionRead
+)
+async def deploy_version(
+    flow_id: UUID,
+    version_no: int,
+    session: Session = Depends(get_db),
+    lfx: LfxClient = Depends(get_lfx),
+):
+    try:
+        version = store.get_version_by_no(session, flow_id, version_no)
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+    try:
+        uploaded = await lfx.upload_flow(
+            version.langflow_json, flow_id=str(version.id), replace=True
+        )
+    except LfxInvalidFlow as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+    except LfxConflict as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
+    except LfxUnavailable as exc:
+        raise HTTPException(status_code=503, detail=str(exc)) from exc
+    except LfxError as exc:
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
+    return _read_version(store.mark_deployed(session, version, uploaded.id))
+
+
+def _resolve_version(session: Session, flow_id: UUID, version_no: int | None):
+    if version_no is not None:
+        return store.get_version_by_no(session, flow_id, version_no)
+    return store.get_latest_deployed_version(session, flow_id)
+
+
+@flows_router.post("/{flow_id}/run", response_model=RunRead)
+async def run_flow(
+    flow_id: UUID,
+    data: RunRequest,
+    stream: bool = Query(default=False),
+    session: Session = Depends(get_db),
+    lfx: LfxClient = Depends(get_lfx),
+):
+    try:
+        version = _resolve_version(session, flow_id, data.version_no)
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+    except store.InvalidError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+    if stream:
+        return await _run_stream(session, lfx, version, data)
+    try:
+        run = await runner.execute_run(
+            session,
+            lfx,
+            version,
+            payload=data.input,
+            tenant_id=data.tenant_id,
+            session_id=data.session_id,
+            callback_base_url=data.callback_base_url or settings.callback_base_url,
+            continuation_flow_id=data.continuation_flow_id,
+        )
+    except LfxNotFound as exc:
+        raise HTTPException(status_code=502, detail=f"LFX drift: {exc}") from exc
+    except LfxUnavailable as exc:
+        raise HTTPException(status_code=503, detail=str(exc)) from exc
+    except LfxError as exc:
+        raise HTTPException(status_code=502, detail=str(exc)) from exc
+    return _read_run(run)
+
+
+async def _run_stream(session: Session, lfx: LfxClient, version, data: RunRequest):
+    if not version.lfx_flow_id:
+        raise HTTPException(
+            status_code=422, detail=f"version {version.id} is not deployed to LFX"
+        )
+    run = store.create_run(
+        session,
+        version,
+        input=data.input,
+        tenant_id=data.tenant_id,
+        session_id=data.session_id,
+    )
+    envelope = runner.build_envelope(
+        payload=data.input,
+        run_id=run.id,
+        callback_base_url=data.callback_base_url or settings.callback_base_url,
+        continuation_flow_id=data.continuation_flow_id,
+    )
+    run_id = run.id
+    lfx_flow_id = version.lfx_flow_id
+    session_id = data.session_id or str(run.id)
+
+    async def event_gen() -> AsyncIterator[str]:
+        yield f"event: run\ndata: {json.dumps({'run_id': str(run_id)})}\n\n"
+        try:
+            async with httpx.AsyncClient(
+                base_url=lfx.base_url, timeout=lfx.timeout, headers=lfx._headers()
+            ) as client:
+                async with client.stream(
+                    "POST",
+                    f"/flows/{lfx_flow_id}/stream",
+                    json={"input_value": envelope, "session_id": session_id},
+                ) as response:
+                    if response.status_code == 404:
+                        raise LfxNotFound(f"flow {lfx_flow_id} unknown to LFX")
+                    response.raise_for_status()
+                    async for chunk in response.aiter_text():
+                        yield chunk
+        except (LfxNotFound, httpx.HTTPError) as exc:
+            yield f"event: error\ndata: {json.dumps({'error': str(exc)})}\n\n"
+        # Finalize from a fresh session: the request session may be closed.
+        with Session(get_engine()) as fresh:
+            try:
+                fresh_run = store.get_run(fresh, run_id)
+                status = (
+                    "pending_approval"
+                    if runner._task_exists(fresh, run_id)
+                    else "completed"
+                )
+                store.set_run_result(fresh, fresh_run, status, {"streamed": True})
+            except store.NotFoundError:
+                status = "failed"
+        yield f"event: run_finished\ndata: {json.dumps({'run_id': str(run_id), 'status': status})}\n\n"
+
+    return StreamingResponse(event_gen(), media_type="text/event-stream")
+
+
+@flows_router.get("/{flow_id}/runs", response_model=list[RunRead])
+def list_runs(flow_id: UUID, session: Session = Depends(get_db)):
+    try:
+        return [_read_run(r) for r in store.list_runs(session, flow_id)]
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+
+
+@flows_router.get("/runs/{run_id}", response_model=RunRead)
+def get_run(run_id: UUID, session: Session = Depends(get_db)):
+    try:
+        return _read_run(store.get_run(session, run_id))
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+
+
+@approvals_router.post("", response_model=ApprovalRead, status_code=201)
+def create_approval(data: ApprovalCreate, session: Session = Depends(get_db)):
+    """Flow callback contract: report a terminal approval state for a run."""
+    try:
+        return _read_task(store.create_approval_task(session, data))
+    except store.NotFoundError as exc:
+        raise HTTPException(status_code=404, detail=str(exc)) from exc
+    except store.ConflictError as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
+    except store.InvalidError as exc:
+        raise HTTPException(status_code=422, detail=str(exc)) from exc
+
+
+@approvals_router.get("", response_model=list[ApprovalRead])
+def list_approvals(
+    tenant_id: str | None = Query(default=None),
+    session: Session = Depends(get_db),
+):
+    return [_read_task(t) for t in store.list_approval_tasks(session, tenant_id)]
--- a/backend/app/flows/lfx_client.py
+++ b/backend/app/flows/lfx_client.py
@ -0,0 +1,184 @@
+"""Async client for the LFX flow runtime (stateless `lfx serve` process)."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+import httpx
+
+
+class LfxError(Exception):
+    """Base error for LFX communication problems."""
+
+
+class LfxNotFound(LfxError):
+    """Flow id unknown to LFX (HTTP 404)."""
+
+
+class LfxInvalidFlow(LfxError):
+    """Flow JSON rejected by LFX (HTTP 422)."""
+
+
+class LfxConflict(LfxError):
+    """Flow id already registered without replace=true (HTTP 409)."""
+
+
+class LfxRunFailed(LfxError):
+    """Flow execution failed inside LFX (HTTP 500 or success=false)."""
+
+
+class LfxUnavailable(LfxError):
+    """LFX process unreachable."""
+
+
+@dataclass
+class LfxUploadResult:
+    id: str
+    name: str
+    description: str | None
+    run_url: str
+
+
+@dataclass
+class LfxRunResult:
+    result: str
+    success: bool
+    logs: str
+    type: str
+    component: str
+
+
+class LfxClient:
+    """Thin async wrapper around the LFX serve HTTP API."""
+
+    def __init__(
+        self, base_url: str, timeout: float = 120.0, api_key: str | None = None
+    ) -> None:
+        self.base_url = base_url.rstrip("/")
+        self.timeout = timeout
+        self.api_key = api_key
+
+    def _headers(self) -> dict[str, str]:
+        return {"x-api-key": self.api_key} if self.api_key else {}
+
+    def _client(self) -> httpx.AsyncClient:
+        return httpx.AsyncClient(
+            base_url=self.base_url, timeout=self.timeout, headers=self._headers()
+        )
+
+    async def health(self) -> dict:
+        try:
+            async with self._client() as client:
+                response = await client.get("/health")
+                response.raise_for_status()
+                return response.json()
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    async def list_flows(self) -> list[dict]:
+        try:
+            async with self._client() as client:
+                response = await client.get("/flows")
+                response.raise_for_status()
+                return response.json()
+        except httpx.HTTPStatusError as exc:
+            raise self._mapped(exc) from exc
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    async def upload_flow(
+        self, flow_json: dict, *, flow_id: str | None = None, replace: bool = False
+    ) -> LfxUploadResult:
+        """Register a Langflow-export-format flow JSON. Returns the LFX flow id."""
+        data = flow_json.get("data")
+        if not isinstance(data, dict):
+            raise LfxInvalidFlow("flow JSON must contain a 'data' object")
+        body = {
+            "name": flow_json.get("name", "flow"),
+            "description": flow_json.get("description"),
+            "data": data,
+            "replace": replace,
+        }
+        if flow_id is not None:
+            body["id"] = flow_id
+        try:
+            async with self._client() as client:
+                response = await client.post("/flows/upload/", json=body)
+                response.raise_for_status()
+                payload = response.json()
+                return LfxUploadResult(
+                    id=payload["id"],
+                    name=payload.get("name", ""),
+                    description=payload.get("description"),
+                    run_url=payload.get("run_url", ""),
+                )
+        except httpx.HTTPStatusError as exc:
+            raise self._mapped(exc) from exc
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    async def run_flow(
+        self,
+        lfx_flow_id: str,
+        *,
+        input_value: str,
+        session_id: str | None = None,
+        global_vars: dict[str, str] | None = None,
+    ) -> LfxRunResult:
+        """Execute a flow synchronously; raises on failure."""
+        body: dict = {"input_value": input_value}
+        if session_id is not None:
+            body["session_id"] = session_id
+        if global_vars is not None:
+            body["global_vars"] = global_vars
+        try:
+            async with self._client() as client:
+                response = await client.post(f"/flows/{lfx_flow_id}/run", json=body)
+                if response.status_code == 404:
+                    raise LfxNotFound(f"flow {lfx_flow_id} unknown to LFX")
+                data = response.json()
+                result = LfxRunResult(
+                    result=data.get("result", ""),
+                    success=bool(data.get("success", False)),
+                    logs=data.get("logs", ""),
+                    type=data.get("type", ""),
+                    component=data.get("component", ""),
+                )
+                if response.status_code >= 400 or not result.success:
+                    raise LfxRunFailed(f"LFX run failed: {result.result}")
+                return result
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    async def flow_info(self, lfx_flow_id: str) -> dict:
+        try:
+            async with self._client() as client:
+                response = await client.get(f"/flows/{lfx_flow_id}/info")
+                if response.status_code == 404:
+                    raise LfxNotFound(f"flow {lfx_flow_id} unknown to LFX")
+                response.raise_for_status()
+                return response.json()
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    async def delete_flow(self, lfx_flow_id: str) -> None:
+        try:
+            async with self._client() as client:
+                response = await client.delete(f"/flows/{lfx_flow_id}")
+                if response.status_code == 404:
+                    raise LfxNotFound(f"flow {lfx_flow_id} unknown to LFX")
+                response.raise_for_status()
+        except httpx.HTTPError as exc:
+            raise LfxUnavailable(f"LFX unreachable at {self.base_url}: {exc}") from exc
+
+    @staticmethod
+    def _mapped(exc: httpx.HTTPStatusError) -> LfxError:
+        status = exc.response.status_code
+        detail = exc.response.text[:500]
+        if status == 404:
+            return LfxNotFound(detail)
+        if status == 409:
+            return LfxConflict(detail)
+        if status == 422:
+            return LfxInvalidFlow(detail)
+        return LfxError(f"LFX error {status}: {detail}")
--- a/backend/app/flows/runner.py
+++ b/backend/app/flows/runner.py
@ -0,0 +1,93 @@
+"""Run orchestration: our DB rows + LFX execution + terminal-state mapping."""
+
+from __future__ import annotations
+
+import json
+from uuid import UUID
+
+from sqlmodel import Session, select
+
+from app.models import ApprovalTask, FlowRun, FlowVersion
+
+from . import store
+from .lfx_client import LfxClient, LfxRunFailed
+from .store import InvalidError
+
+
+def build_envelope(
+    *,
+    payload: dict,
+    run_id: UUID,
+    callback_base_url: str,
+    continuation_flow_id: UUID | None,
+) -> str:
+    return json.dumps(
+        {
+            "payload": payload,
+            "run_id": str(run_id),
+            "callback_url": callback_base_url.rstrip("/"),
+            "continuation_flow_id": (
+                str(continuation_flow_id) if continuation_flow_id else None
+            ),
+        }
+    )
+
+
+def _task_exists(session: Session, run_id: UUID) -> bool:
+    return (
+        session.exec(
+            select(ApprovalTask).where(
+                ApprovalTask.run_id == run_id, ApprovalTask.status == "open"
+            )
+        ).first()
+        is not None
+    )
+
+
+async def execute_run(
+    session: Session,
+    lfx: LfxClient,
+    version: FlowVersion,
+    *,
+    payload: dict,
+    tenant_id: str = "default",
+    session_id: str | None = None,
+    callback_base_url: str,
+    continuation_flow_id: UUID | None = None,
+) -> FlowRun:
+    """Run a deployed version to a terminal state (no interrupts).
+
+    The flow always terminates: either it completes, or its approval branch
+    POSTs back to /api/approvals (creating a task) and terminates with a
+    pending marker. Status is derived from that side effect, not from
+    result-text parsing.
+    """
+    if not version.lfx_flow_id:
+        raise InvalidError(f"version {version.id} is not deployed to LFX")
+    run = store.create_run(
+        session, version, input=payload, tenant_id=tenant_id, session_id=session_id
+    )
+    envelope = build_envelope(
+        payload=payload,
+        run_id=run.id,
+        callback_base_url=callback_base_url,
+        continuation_flow_id=continuation_flow_id,
+    )
+    try:
+        result = await lfx.run_flow(
+            version.lfx_flow_id,
+            input_value=envelope,
+            session_id=session_id or str(run.id),
+        )
+    except LfxRunFailed as exc:
+        return store.set_run_result(
+            session, run, "failed", {"error": str(exc)}
+        )
+    output = {
+        "result": result.result,
+        "component": result.component,
+        "type": result.type,
+    }
+    if _task_exists(session, run.id):
+        return store.set_run_result(session, run, "pending_approval", output)
+    return store.set_run_result(session, run, "completed", output)
--- a/backend/app/flows/schemas.py
+++ b/backend/app/flows/schemas.py
@ -0,0 +1,86 @@
+"""Pydantic contracts for the flows API."""
+
+from datetime import datetime
+from uuid import UUID
+
+from pydantic import BaseModel, Field
+
+
+class FlowDefinitionCreate(BaseModel):
+    name: str = Field(min_length=1, max_length=200)
+    description: str = Field(default="", max_length=2000)
+    continuation_flow_id: UUID | None = None
+
+
+class FlowDefinitionRead(BaseModel):
+    id: UUID
+    name: str
+    description: str
+    status: str
+    continuation_flow_id: UUID | None
+    created_at: datetime
+
+
+class FlowVersionCreate(BaseModel):
+    langflow_json: dict
+    author: str = Field(default="", max_length=200)
+
+
+class FlowVersionRead(BaseModel):
+    id: UUID
+    flow_id: UUID
+    version_no: int
+    langflow_json: dict
+    lfx_flow_id: str | None
+    deployed_at: datetime | None
+    author: str
+    created_at: datetime
+
+
+class RunRequest(BaseModel):
+    """Start a flow run. `input` is the domain payload handed to the flow."""
+
+    input: dict = Field(default_factory=dict)
+    version_no: int | None = None
+    tenant_id: str = Field(default="default", max_length=200)
+    session_id: str | None = None
+    # Base URL the flow uses for callbacks (e.g. approval tasks).
+    # Defaults to settings.callback_base_url; tests point it at a live server.
+    callback_base_url: str | None = None
+    continuation_flow_id: UUID | None = None
+
+
+class RunRead(BaseModel):
+    id: UUID
+    version_id: UUID
+    tenant_id: str
+    status: str
+    input: dict | None
+    output: dict | None
+    session_id: str | None
+    created_at: datetime
+    finished_at: datetime | None
+
+
+class ApprovalCreate(BaseModel):
+    """Callback contract: a flow reports a terminal approval state."""
+
+    run_id: UUID
+    title: str = Field(default="", max_length=500)
+    payload: dict = Field(default_factory=dict)
+    continuation_flow_id: UUID | None = None
+
+
+class ApprovalRead(BaseModel):
+    id: UUID
+    run_id: UUID
+    version_id: UUID
+    tenant_id: str
+    title: str
+    payload: dict
+    continuation_flow_id: UUID | None
+    approver: str | None
+    status: str
+    decision_note: str
+    created_at: datetime
+    decided_at: datetime | None
--- a/backend/app/flows/store.py
+++ b/backend/app/flows/store.py
@ -0,0 +1,225 @@
+"""Persistence operations for flow definitions, versions, runs, and tasks."""
+
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from uuid import UUID
+
+from sqlalchemy.exc import IntegrityError
+from sqlmodel import Session, func, select
+
+from app.models import ApprovalTask, FlowDefinition, FlowRun, FlowVersion
+
+from .schemas import ApprovalCreate, FlowDefinitionCreate, FlowVersionCreate
+
+
+class NotFoundError(Exception):
+    pass
+
+
+class ConflictError(Exception):
+    pass
+
+
+class InvalidError(Exception):
+    pass
+
+
+def create_definition(session: Session, data: FlowDefinitionCreate) -> FlowDefinition:
+    if data.continuation_flow_id is not None and session.get(
+        FlowDefinition, data.continuation_flow_id
+    ) is None:
+        raise InvalidError("continuation_flow_id unknown")
+    definition = FlowDefinition(
+        name=data.name,
+        description=data.description,
+        continuation_flow_id=data.continuation_flow_id,
+    )
+    session.add(definition)
+    try:
+        session.commit()
+    except IntegrityError as exc:
+        session.rollback()
+        raise ConflictError(f"flow {data.name!r} already exists") from exc
+    session.refresh(definition)
+    return definition
+
+
+def get_definition(session: Session, flow_id: UUID) -> FlowDefinition:
+    definition = session.get(FlowDefinition, flow_id)
+    if definition is None:
+        raise NotFoundError(f"flow {flow_id} not found")
+    return definition
+
+
+def list_definitions(session: Session) -> list[FlowDefinition]:
+    return list(session.exec(select(FlowDefinition).order_by(FlowDefinition.name)).all())
+
+
+def _validate_flow_json(flow_json: dict) -> None:
+    if not isinstance(flow_json, dict):
+        raise InvalidError("langflow_json must be an object")
+    data = flow_json.get("data")
+    if not isinstance(data, dict):
+        raise InvalidError("langflow_json must contain a 'data' object")
+    if not isinstance(data.get("nodes"), list) or not isinstance(data.get("edges"), list):
+        raise InvalidError("langflow_json.data must contain 'nodes' and 'edges' lists")
+
+
+def create_version(
+    session: Session, flow_id: UUID, data: FlowVersionCreate
+) -> FlowVersion:
+    get_definition(session, flow_id)
+    _validate_flow_json(data.langflow_json)
+    max_no = session.exec(
+        select(func.max(FlowVersion.version_no)).where(FlowVersion.flow_id == flow_id)
+    ).one()
+    version = FlowVersion(
+        flow_id=flow_id,
+        version_no=(max_no or 0) + 1,
+        langflow_json=data.langflow_json,
+        author=data.author,
+    )
+    session.add(version)
+    session.commit()
+    session.refresh(version)
+    return version
+
+
+def get_version(session: Session, version_id: UUID) -> FlowVersion:
+    version = session.get(FlowVersion, version_id)
+    if version is None:
+        raise NotFoundError(f"flow version {version_id} not found")
+    return version
+
+
+def list_versions(session: Session, flow_id: UUID) -> list[FlowVersion]:
+    get_definition(session, flow_id)
+    return list(
+        session.exec(
+            select(FlowVersion)
+            .where(FlowVersion.flow_id == flow_id)
+            .order_by(FlowVersion.version_no)
+        ).all()
+    )
+
+
+def get_version_by_no(session: Session, flow_id: UUID, version_no: int) -> FlowVersion:
+    version = session.exec(
+        select(FlowVersion).where(
+            FlowVersion.flow_id == flow_id, FlowVersion.version_no == version_no
+        )
+    ).first()
+    if version is None:
+        raise NotFoundError(f"flow {flow_id} has no version {version_no}")
+    return version
+
+
+def get_latest_deployed_version(session: Session, flow_id: UUID) -> FlowVersion:
+    version = session.exec(
+        select(FlowVersion)
+        .where(FlowVersion.flow_id == flow_id, FlowVersion.deployed_at.is_not(None))
+        .order_by(FlowVersion.version_no.desc())
+    ).first()
+    if version is None:
+        raise InvalidError(f"flow {flow_id} has no deployed version")
+    return version
+
+
+def mark_deployed(session: Session, version: FlowVersion, lfx_flow_id: str) -> FlowVersion:
+    version.lfx_flow_id = lfx_flow_id
+    version.deployed_at = datetime.now(timezone.utc)
+    session.add(version)
+    session.commit()
+    session.refresh(version)
+    return version
+
+
+def create_run(
+    session: Session,
+    version: FlowVersion,
+    *,
+    input: dict | None,
+    tenant_id: str = "default",
+    session_id: str | None = None,
+) -> FlowRun:
+    run = FlowRun(
+        version_id=version.id,
+        tenant_id=tenant_id,
+        input=input,
+        session_id=session_id or str(version.id),
+    )
+    session.add(run)
+    session.commit()
+    session.refresh(run)
+    return run
+
+
+def set_run_result(
+    session: Session, run: FlowRun, status: str, output: dict | None
+) -> FlowRun:
+    run.status = status
+    run.output = output
+    run.finished_at = datetime.now(timezone.utc)
+    session.add(run)
+    session.commit()
+    session.refresh(run)
+    return run
+
+
+def get_run(session: Session, run_id: UUID) -> FlowRun:
+    run = session.get(FlowRun, run_id)
+    if run is None:
+        raise NotFoundError(f"run {run_id} not found")
+    return run
+
+
+def list_runs(session: Session, flow_id: UUID) -> list[FlowRun]:
+    get_definition(session, flow_id)
+    return list(
+        session.exec(
+            select(FlowRun)
+            .join(FlowVersion, FlowVersion.id == FlowRun.version_id)
+            .where(FlowVersion.flow_id == flow_id)
+            .order_by(FlowRun.created_at.desc())
+        ).all()
+    )
+
+
+def create_approval_task(session: Session, data: ApprovalCreate) -> ApprovalTask:
+    run = session.get(FlowRun, data.run_id)
+    if run is None:
+        raise NotFoundError(f"run {data.run_id} not found")
+    if data.continuation_flow_id is not None and session.get(
+        FlowDefinition, data.continuation_flow_id
+    ) is None:
+        raise InvalidError("continuation_flow_id unknown")
+    existing = session.exec(
+        select(ApprovalTask).where(
+            ApprovalTask.run_id == data.run_id, ApprovalTask.status == "open"
+        )
+    ).first()
+    if existing is not None:
+        raise ConflictError(f"run {data.run_id} already has an open approval task")
+    task = ApprovalTask(
+        run_id=run.id,
+        version_id=run.version_id,
+        tenant_id=run.tenant_id,
+        title=data.title,
+        payload=data.payload,
+        continuation_flow_id=data.continuation_flow_id,
+    )
+    session.add(task)
+    run.status = "pending_approval"
+    run.finished_at = datetime.now(timezone.utc)
+    session.add(run)
+    session.commit()
+    session.refresh(task)
+    return task
+
+
+def list_approval_tasks(session: Session, tenant_id: str | None = None) -> list[ApprovalTask]:
+    query = select(ApprovalTask).order_by(ApprovalTask.created_at.desc())
+    if tenant_id is not None:
+        query = query.where(ApprovalTask.tenant_id == tenant_id)
+    return list(session.exec(query).all())
--- a/backend/app/main.py
+++ b/backend/app/main.py
@ -1,5 +1,6 @@
 from fastapi import FastAPI

+from .flows.api import approvals_router, flows_router
 from .settings import settings

 app = FastAPI(
@ -11,6 +12,9 @@ app = FastAPI(
    openapi_url="/api/openapi.json",
 )

+app.include_router(flows_router)
+app.include_router(approvals_router)
+

@app.get("/")
 async def root():
--- a/backend/app/settings.py
+++ b/backend/app/settings.py
@ -21,7 +21,11 @@ class Settings(BaseSettings):
    langflow_url: str = "http://localhost:7860"
    langflow_api_key: str = ""
    lfx_url: str = "http://localhost:6004"
+    lfx_api_key: str = ""
    llm_api_key: str = ""
+    # Base URL flows use for callbacks into this API. Must be reachable
+    # FROM the LFX process (compose: http://app:8000).
+    callback_base_url: str = "http://localhost:8000"


 settings = Settings()
--- a/backend/scripts/make_flow_fixtures.py
+++ b/backend/scripts/make_flow_fixtures.py
@ -0,0 +1,444 @@
+"""Generate Langflow-export-format flow JSON fixtures.
+
+Uses lfx's own serializers (Component.to_frontend_node /
+build_custom_component_template), so the output is byte-faithful to what the
+Langflow UI would export. Run with the backend venv (has the `lfx` dev dep)::
+
+    uv run python scripts/make_flow_fixtures.py
+
+Then verify::
+
+    uv run lfx validate --level 4 backend/tests/fixtures/flows/
+"""
+
+from __future__ import annotations
+
+import importlib
+import json
+import sys
+import uuid
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent.parent
+FIXTURE_DIR = REPO_ROOT / "backend" / "tests" / "fixtures" / "flows"
+
+HANDLE_QUOTE = "\u0153"  # ReactFlow handle-id quoting used by Langflow exports
+
+
+# --------------------------------------------------------------------------
+# node builders
+# --------------------------------------------------------------------------
+def _normalize(node_dict: dict, node_id: str, comp_name: str, x: int, y: int) -> dict:
+    # to_frontend_node() returns an envelope {"data": {...}, "id": ...};
+    # build_custom_component_template() returns the bare node dict.
+    if "data" not in node_dict:
+        node_dict = {
+            "data": {"node": node_dict, "type": comp_name, "id": node_id},
+            "id": node_id,
+        }
+    else:
+        node_dict["id"] = node_id
+        node_dict["data"]["id"] = node_id
+        node_dict["data"]["type"] = comp_name
+    node_dict["data"]["showNode"] = True
+    node_dict["measured"] = {"width": 320, "height": 200}
+    node_dict["position"] = {"x": x, "y": y}
+    node_dict["type"] = "genericNode"
+    return node_dict
+
+
+def builtin_node(
+    module_path: str,
+    class_name: str,
+    node_id: str,
+    values: dict | None = None,
+    position: tuple[int, int] = (0, 0),
+) -> dict:
+    mod = importlib.import_module(module_path)
+    cls = getattr(mod, class_name)
+    inst = cls()
+    node_dict = _normalize(inst.to_frontend_node(), node_id, cls.name, *position)
+    for field, value in (values or {}).items():
+        node_dict["data"]["node"]["template"][field]["value"] = value
+    return node_dict
+
+
+def custom_node(
+    code: str,
+    node_id: str,
+    values: dict | None = None,
+    position: tuple[int, int] = (0, 0),
+) -> dict:
+    from lfx.custom import validate as validate_mod
+    from lfx.custom.utils import build_custom_component_template
+
+    cls = validate_mod.create_class(code, validate_mod.extract_class_name(code))
+    inst = cls()
+    inst._code = code
+    bare, _ = build_custom_component_template(inst)
+    node_dict = _normalize(bare, node_id, "CustomComponent", *position)
+    for field, value in (values or {}).items():
+        node_dict["data"]["node"]["template"][field]["value"] = value
+    return node_dict
+
+
+# --------------------------------------------------------------------------
+# edges
+# --------------------------------------------------------------------------
+def _output_def(node: dict, output_name: str) -> dict:
+    for out in node["data"]["node"]["outputs"]:
+        if out["name"] == output_name:
+            return out
+    raise KeyError(f"output {output_name!r} not in {node['id']}")
+
+
+def _input_def(node: dict, input_name: str) -> dict:
+    field = node["data"]["node"]["template"][input_name]
+    return field
+
+
+def edge(src: dict, src_output: str, dst: dict, dst_input: str) -> dict:
+    out = _output_def(src, src_output)
+    inp = _input_def(dst, dst_input)
+    source_handle = {
+        "dataType": src["data"]["type"],
+        "id": src["id"],
+        "name": src_output,
+        "output_types": out.get("types", []),
+    }
+    target_handle = {
+        "fieldName": dst_input,
+        "id": dst["id"],
+        "inputTypes": inp.get("input_types", []),
+        "type": inp.get("type", "other"),
+    }
+    sh = json.dumps(source_handle).replace('"', HANDLE_QUOTE)
+    th = json.dumps(target_handle).replace('"', HANDLE_QUOTE)
+    return {
+        "animated": False,
+        "className": "",
+        "data": {"sourceHandle": source_handle, "targetHandle": target_handle},
+        "id": f"xy-edge__{sh}-{th}",
+        "selected": False,
+        "source": src["id"],
+        "sourceHandle": sh,
+        "target": dst["id"],
+        "targetHandle": th,
+    }
+
+
+# --------------------------------------------------------------------------
+# flow document
+# --------------------------------------------------------------------------
+def flow_doc(
+    name: str, description: str, nodes: list[dict], edges: list[dict]
+) -> dict:
+    return {
+        "data": {
+            "nodes": nodes,
+            "edges": edges,
+            "viewport": {"x": 0, "y": 0, "zoom": 1},
+        },
+        "description": description,
+        "endpoint_name": None,
+        "icon": None,
+        "icon_bg_color": None,
+        "id": str(uuid.uuid5(uuid.NAMESPACE_URL, f"kirche-einfach/{name}")),
+        "is_component": False,
+        "locked": False,
+        "mcp_enabled": False,
+        "name": name,
+        "tags": [],
+        "webhook": False,
+    }
+
+
+# --------------------------------------------------------------------------
+# custom component code
+# --------------------------------------------------------------------------
+RULE_CHECK_CODE = '''from lfx.custom import Component
+from lfx.io import MessageTextInput, Output
+from lfx.schema.message import Message
+import json
+
+
+class RuleCheckComponent(Component):
+    display_name = "Rule Check"
+    description = "Bewertet Betrag gegen Schwelle aus JSON-Eingabe."
+
+    inputs = [
+        MessageTextInput(name="payload", display_name="Payload"),
+    ]
+    outputs = [
+        Output(display_name="Verdict", name="verdict", method="check"),
+    ]
+
+    def _text(self, value) -> str:
+        if value is None:
+            return ""
+        if hasattr(value, "text"):
+            return value.text or ""
+        return str(value)
+
+    def check(self) -> Message:
+        try:
+            data = json.loads(self._text(self.payload) or "{}")
+        except Exception:
+            data = {}
+        if not isinstance(data, dict):
+            data = {}
+        # Die API ruft Flows immer mit Huelle auf
+        # {"payload": {...}, "run_id": ..., ...}; rohe Payloads gehen auch.
+        if isinstance(data.get("payload"), dict):
+            data = data["payload"]
+        try:
+            betrag = float(data.get("betrag", 0) or 0)
+        except (TypeError, ValueError):
+            betrag = 0.0
+        try:
+            schwelle = float(data.get("schwelle", 200000) or 200000)
+        except (TypeError, ValueError):
+            schwelle = 200000.0
+        return Message(text="PRUEFUNG" if betrag > schwelle else "OK")
+'''
+
+ENVELOPE_CODE = '''from lfx.custom import Component
+from lfx.io import MessageTextInput, Output
+from lfx.schema.message import Message
+import json
+
+
+class EnvelopeComponent(Component):
+    display_name = "Envelope"
+    description = "Zerlegt die Eingabe-Huelle in Payload und Laufzeit-Kontext."
+
+    inputs = [
+        MessageTextInput(name="raw", display_name="Raw Input"),
+    ]
+    outputs = [
+        Output(display_name="Payload", name="payload", method="get_payload"),
+        Output(display_name="Run ID", name="run_id", method="get_run_id"),
+        Output(
+            display_name="Callback URL",
+            name="callback_url",
+            method="get_callback_url",
+        ),
+        Output(
+            display_name="Continuation",
+            name="continuation",
+            method="get_continuation",
+        ),
+    ]
+
+    def _text(self, value) -> str:
+        if value is None:
+            return ""
+        if hasattr(value, "text"):
+            return value.text or ""
+        return str(value)
+
+    def _env(self) -> dict:
+        if not hasattr(self, "_env_cache"):
+            try:
+                self._env_cache = json.loads(self._text(self.raw) or "{}")
+            except Exception:
+                self._env_cache = {}
+            if not isinstance(self._env_cache, dict):
+                self._env_cache = {}
+        return self._env_cache
+
+    def get_payload(self) -> Message:
+        return Message(text=json.dumps(self._env().get("payload", {})))
+
+    def get_run_id(self) -> Message:
+        return Message(text=str(self._env().get("run_id", "")))
+
+    def get_callback_url(self) -> Message:
+        return Message(text=str(self._env().get("callback_url", "")))
+
+    def get_continuation(self) -> Message:
+        value = self._env().get("continuation_flow_id")
+        return Message(text=str(value) if value else "")
+'''
+
+APPROVAL_CALLBACK_CODE = '''from lfx.custom import Component
+from lfx.io import MessageTextInput, Output
+from lfx.schema.message import Message
+
+
+class ApprovalCallbackComponent(Component):
+    display_name = "Approval Callback"
+    description = "Meldet einen Sonderfall per HTTP an unsere API und terminiert."
+
+    inputs = [
+        MessageTextInput(name="trigger", display_name="Trigger"),
+        MessageTextInput(name="run_id", display_name="Run ID"),
+        MessageTextInput(name="callback_url", display_name="Callback URL"),
+        MessageTextInput(
+            name="continuation_flow_id",
+            display_name="Continuation Flow ID",
+        ),
+        MessageTextInput(name="facts", display_name="Facts"),
+    ]
+    outputs = [
+        Output(display_name="Result", name="result", method="notify"),
+    ]
+
+    def _text(self, value) -> str:
+        if value is None:
+            return ""
+        if hasattr(value, "text"):
+            return value.text or ""
+        return str(value)
+
+    def notify(self) -> Message:
+        import httpx
+        import json
+
+        trigger = self._text(self.trigger).strip()
+        if not trigger:
+            # Zweig wurde nicht genommen: kein Seiteneffekt.
+            return Message(text="")
+        try:
+            facts = json.loads(self._text(self.facts) or "{}")
+        except Exception:
+            facts = {}
+        url = self._text(self.callback_url).rstrip("/") + "/api/approvals"
+        body = {
+            "run_id": self._text(self.run_id),
+            "title": f"Freigabe erforderlich ({trigger})",
+            "payload": {"verdict": trigger, "facts": facts},
+            "continuation_flow_id": self._text(self.continuation_flow_id) or None,
+        }
+        try:
+            response = httpx.post(url, json=body, timeout=10.0)
+            response.raise_for_status()
+        except Exception as exc:
+            return Message(text=f"CALLBACK_FAILED: {exc}")
+        return Message(text="PENDING_HUMAN_APPROVAL")
+'''
+
+
+# --------------------------------------------------------------------------
+# flows
+# --------------------------------------------------------------------------
+ROUTER_VALUES = {
+    "operator": "equals",
+    "match_text": "PRUEFUNG",
+    "true_case_message": "Sonderfall: menschliche Pruefung erforderlich",
+    "false_case_message": "Standardfall: automatisch freigegeben",
+}
+
+
+def build_simple_rule() -> dict:
+    entry = builtin_node(
+        "lfx.components.input_output.chat",
+        "ChatInput",
+        "ChatInput-entry",
+        position=(0, 200),
+    )
+    rule = custom_node(RULE_CHECK_CODE, "CustomComponent-rule", position=(400, 200))
+    router = builtin_node(
+        "lfx.components.flow_controls.conditional_router",
+        "ConditionalRouterComponent",
+        "ConditionalRouter-router",
+        values=ROUTER_VALUES,
+        position=(800, 200),
+    )
+    out_ok = builtin_node(
+        "lfx.components.input_output.chat_output",
+        "ChatOutput",
+        "ChatOutput-ok",
+        position=(1200, 60),
+    )
+    out_sonder = builtin_node(
+        "lfx.components.input_output.chat_output",
+        "ChatOutput",
+        "ChatOutput-sonder",
+        position=(1200, 340),
+    )
+    nodes = [entry, rule, router, out_ok, out_sonder]
+    edges = [
+        edge(entry, "message", rule, "payload"),
+        edge(rule, "verdict", router, "input_text"),
+        edge(router, "false_result", out_ok, "input_value"),
+        edge(router, "true_result", out_sonder, "input_value"),
+    ]
+    return flow_doc(
+        "simple_rule",
+        "Regelpruefung ohne Seiteneffekt (Spike-Fixture, kein LLM).",
+        nodes,
+        edges,
+    )
+
+
+def build_approval_handoff() -> dict:
+    entry = builtin_node(
+        "lfx.components.input_output.chat",
+        "ChatInput",
+        "ChatInput-entry",
+        position=(0, 300),
+    )
+    envelope = custom_node(
+        ENVELOPE_CODE, "CustomComponent-envelope", position=(400, 300)
+    )
+    rule = custom_node(RULE_CHECK_CODE, "CustomComponent-rule", position=(800, 300))
+    router = builtin_node(
+        "lfx.components.flow_controls.conditional_router",
+        "ConditionalRouterComponent",
+        "ConditionalRouter-router",
+        values=ROUTER_VALUES,
+        position=(1200, 300),
+    )
+    callback = custom_node(
+        APPROVAL_CALLBACK_CODE,
+        "CustomComponent-callback",
+        position=(1600, 160),
+    )
+    out_pending = builtin_node(
+        "lfx.components.input_output.chat_output",
+        "ChatOutput",
+        "ChatOutput-pending",
+        position=(2000, 160),
+    )
+    out_ok = builtin_node(
+        "lfx.components.input_output.chat_output",
+        "ChatOutput",
+        "ChatOutput-ok",
+        position=(2000, 440),
+    )
+    nodes = [entry, envelope, rule, router, callback, out_pending, out_ok]
+    edges = [
+        edge(entry, "message", envelope, "raw"),
+        edge(envelope, "payload", rule, "payload"),
+        edge(rule, "verdict", router, "input_text"),
+        edge(router, "true_result", callback, "trigger"),
+        edge(envelope, "run_id", callback, "run_id"),
+        edge(envelope, "callback_url", callback, "callback_url"),
+        edge(envelope, "continuation", callback, "continuation_flow_id"),
+        edge(envelope, "payload", callback, "facts"),
+        edge(callback, "result", out_pending, "input_value"),
+        edge(router, "false_result", out_ok, "input_value"),
+    ]
+    return flow_doc(
+        "approval_handoff",
+        "Sonderfall meldet sich per HTTP an unsere API und terminiert (Spike).",
+        nodes,
+        edges,
+    )
+
+
+def main() -> None:
+    FIXTURE_DIR.mkdir(parents=True, exist_ok=True)
+    flows = {
+        "simple_rule.json": build_simple_rule(),
+        "approval_handoff.json": build_approval_handoff(),
+    }
+    for filename, doc in flows.items():
+        path = FIXTURE_DIR / filename
+        path.write_text(json.dumps(doc, indent=2, ensure_ascii=False) + "\n")
+        print(f"wrote {path}")
+
+
+if __name__ == "__main__":
+    sys.exit(main())
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@ -47,15 +47,27 @@ def db_engine():

@pytest.fixture()
 def session(db_engine):
-    """Function-scoped session; tables are truncated after each test."""
-    from sqlmodel import Session, SQLModel
+    """Function-scoped session for direct DB access in tests."""
+    from sqlmodel import Session

    with Session(db_engine) as s:
        yield s
+
+
+@pytest.fixture(autouse=True)
+def _clean_tables(db_engine):
+    """Truncate all domain tables before and after every test (isolation)."""
+    from sqlmodel import SQLModel
+
+    def _truncate() -> None:
        with db_engine.begin() as conn:
            for table in reversed(SQLModel.metadata.sorted_tables):
                conn.execute(table.delete())

+    _truncate()
+    yield
+    _truncate()
+

@pytest.fixture()
 async def client():
@ -67,3 +79,113 @@ async def client():
    transport = ASGITransport(app=app)
    async with AsyncClient(transport=transport, base_url="http://test") as c:
        yield c
+
+
+@pytest.fixture(scope="session")
+def lfx_server(tmp_path_factory):
+    """Real `lfx serve` subprocess on a free port; points settings at it.
+
+    Serves an (initially seeded) flow dir; tests upload fixture flows through
+    the same deploy path production uses.
+    """
+    import shutil
+    import socket
+    import subprocess
+    import sys
+    import time
+    import urllib.request
+    from pathlib import Path
+
+    from app.settings import settings
+
+    bindir = Path(sys.executable).parent
+    lfx_bin = shutil.which("lfx", path=str(bindir)) or "lfx"
+
+    sock = socket.socket()
+    sock.bind(("127.0.0.1", 0))
+    port = sock.getsockname()[1]
+    sock.close()
+
+    flow_dir = tmp_path_factory.mktemp("lfx-flows")
+    seed = (
+        Path(__file__).parent / "fixtures" / "flows" / "simple_rule.json"
+    ).read_text()
+    (flow_dir / "seed.json").write_text(seed)
+
+    env = {
+        **os.environ,
+        # lfx serve refuses to start without a serve key; requests need it too.
+        "LFX_API_KEY": "test-lfx-key",
+    }
+    proc = subprocess.Popen(
+        [
+            lfx_bin,
+            "serve",
+            "--host",
+            "127.0.0.1",
+            "--port",
+            str(port),
+            "--flow-dir",
+            str(flow_dir),
+            str(flow_dir),
+        ],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        text=True,
+        env=env,
+    )
+    url = f"http://127.0.0.1:{port}"
+    deadline = time.time() + 240
+    healthy = False
+    while time.time() < deadline:
+        if proc.poll() is not None:
+            out = proc.stdout.read() if proc.stdout else ""
+            raise RuntimeError(f"lfx serve exited early:\n{out[-4000:]}")
+        try:
+            with urllib.request.urlopen(url + "/health", timeout=3) as response:
+                if response.status == 200:
+                    healthy = True
+                    break
+        except OSError:
+            time.sleep(1)
+    if not healthy:
+        proc.terminate()
+        raise RuntimeError("lfx serve did not become healthy in time")
+
+    old_url = settings.lfx_url
+    old_key = settings.lfx_api_key
+    settings.lfx_url = url
+    settings.lfx_api_key = "test-lfx-key"
+    yield url
+    settings.lfx_url = old_url
+    settings.lfx_api_key = old_key
+    proc.terminate()
+    try:
+        proc.wait(timeout=20)
+    except subprocess.TimeoutExpired:
+        proc.kill()
+
+
+@pytest.fixture(scope="session")
+def live_server():
+    """Real uvicorn server (ephemeral port) so LFX flows can call back
+    into our API over HTTP, exactly like production."""
+    import threading
+    import time
+
+    import uvicorn
+
+    from app.main import app
+
+    config = uvicorn.Config(app, host="127.0.0.1", port=0, log_level="warning")
+    server = uvicorn.Server(config)
+    thread = threading.Thread(target=server.run, daemon=True)
+    thread.start()
+    deadline = time.time() + 30
+    while not server.started and time.time() < deadline:
+        time.sleep(0.05)
+    assert server.started, "uvicorn test server did not start"
+    port = server.servers[0].sockets[0].getsockname()[1]
+    yield f"http://127.0.0.1:{port}"
+    server.should_exit = True
+    thread.join(timeout=15)
--- a/backend/tests/fixtures/flows/approval_handoff.json
+++ b/backend/tests/fixtures/flows/approval_handoff.json
--- a/backend/tests/fixtures/flows/simple_rule.json
+++ b/backend/tests/fixtures/flows/simple_rule.json
--- a/backend/tests/test_flows_api.py
+++ b/backend/tests/test_flows_api.py
@ -0,0 +1,248 @@
+"""Step 3 tests: flows CRUD, versions, deploy, sync/stream runs, handoff E2E."""
+
+import json
+from pathlib import Path
+from uuid import uuid4
+
+FIXTURES = Path(__file__).parent / "fixtures" / "flows"
+
+
+def load_fixture(name: str) -> dict:
+    return json.loads((FIXTURES / name).read_text())
+
+
+async def _create_flow(client, name="regeltest"):
+    response = await client.post(
+        "/api/flows", json={"name": name, "description": "test flow"}
+    )
+    assert response.status_code == 201, response.text
+    return response.json()
+
+
+async def _create_version(client, flow_id, fixture="simple_rule.json"):
+    response = await client.post(
+        f"/api/flows/{flow_id}/versions",
+        json={"langflow_json": load_fixture(fixture), "author": "test"},
+    )
+    assert response.status_code == 201, response.text
+    return response.json()
+
+
+async def _deploy(client, flow_id, version_no=1):
+    response = await client.post(f"/api/flows/{flow_id}/versions/{version_no}/deploy")
+    assert response.status_code == 200, response.text
+    return response.json()
+
+
+async def test_flow_crud(client):
+    created = await _create_flow(client, "crud-flow")
+    assert created["status"] == "active"
+
+    response = await client.get(f"/api/flows/{created['id']}")
+    assert response.status_code == 200
+    assert response.json()["name"] == "crud-flow"
+
+    response = await client.get("/api/flows")
+    assert response.status_code == 200
+    assert any(f["id"] == created["id"] for f in response.json())
+
+    response = await client.post("/api/flows", json={"name": "crud-flow"})
+    assert response.status_code == 409
+
+    response = await client.get(f"/api/flows/{uuid4()}")
+    assert response.status_code == 404
+
+
+async def test_version_validation_and_numbering(client):
+    flow = await _create_flow(client, "versioned")
+
+    v1 = await _create_version(client, flow["id"])
+    assert v1["version_no"] == 1
+    v2 = await _create_version(client, flow["id"])
+    assert v2["version_no"] == 2
+    assert v1["deployed_at"] is None
+
+    response = await client.post(
+        f"/api/flows/{flow['id']}/versions", json={"langflow_json": {"nope": 1}}
+    )
+    assert response.status_code == 422
+
+    response = await client.post(
+        f"/api/flows/{uuid4()}/versions",
+        json={"langflow_json": load_fixture("simple_rule.json")},
+    )
+    assert response.status_code == 404
+
+    response = await client.get(f"/api/flows/{flow['id']}/versions")
+    assert [v["version_no"] for v in response.json()] == [1, 2]
+
+
+async def test_deploy_and_run_standard_and_sonderfall(client, lfx_server):
+    flow = await _create_flow(client, "dachsanierung")
+    await _create_version(client, flow["id"])
+    deployed = await _deploy(client, flow["id"])
+    assert deployed["lfx_flow_id"] == deployed["id"]
+    assert deployed["deployed_at"] is not None
+
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run",
+        json={"input": {"betrag": 120000, "schwelle": 200000}},
+    )
+    assert response.status_code == 200, response.text
+    run = response.json()
+    assert run["status"] == "completed"
+    assert "Standardfall" in run["output"]["result"]
+    assert run["finished_at"] is not None
+
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run",
+        json={"input": {"betrag": 250000, "schwelle": 200000}},
+    )
+    assert response.status_code == 200, response.text
+    run = response.json()
+    assert run["status"] == "completed"
+    assert "Sonderfall" in run["output"]["result"]
+
+    response = await client.get(f"/api/flows/runs/{run['id']}")
+    assert response.status_code == 200
+    assert response.json()["id"] == run["id"]
+
+
+async def test_run_undeployed_version_fails(client):
+    flow = await _create_flow(client, "undeployed")
+    await _create_version(client, flow["id"])
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run", json={"input": {"betrag": 1}}
+    )
+    assert response.status_code == 422
+
+
+async def test_run_explicit_version_no(client, lfx_server):
+    flow = await _create_flow(client, "explicit-version")
+    await _create_version(client, flow["id"])
+    await _create_version(client, flow["id"])
+    await _deploy(client, flow["id"], version_no=2)
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run",
+        json={"input": {"betrag": 1}, "version_no": 2},
+    )
+    assert response.status_code == 200, response.text
+    assert response.json()["status"] == "completed"
+
+
+async def test_run_stream_events(client, lfx_server):
+    flow = await _create_flow(client, "streamed")
+    await _create_version(client, flow["id"])
+    await _deploy(client, flow["id"])
+
+    events: list[tuple[str, str]] = []
+    async with client.stream(
+        "POST",
+        f"/api/flows/{flow['id']}/run?stream=true",
+        json={"input": {"betrag": 1}},
+    ) as response:
+        assert response.status_code == 200, await response.aread()
+        current_event = "message"
+        async for line in response.aiter_lines():
+            if line.startswith("event:"):
+                current_event = line.split(":", 1)[1].strip()
+            elif line.startswith("data:"):
+                events.append((current_event, line.split(":", 1)[1].strip()))
+                current_event = "message"
+
+    assert events, "expected SSE events"
+    assert events[0][0] == "run"
+    first_payload = json.loads(events[0][1])
+    assert "run_id" in first_payload
+    assert events[-1][0] == "run_finished"
+    last_payload = json.loads(events[-1][1])
+    assert last_payload["status"] == "completed"
+
+    response = await client.get(f"/api/flows/runs/{first_payload['run_id']}")
+    assert response.status_code == 200
+    assert response.json()["status"] == "completed"
+
+
+async def test_approval_handoff_end_to_end(client, lfx_server, live_server):
+    flow = await _create_flow(client, "freigabe")
+    await _create_version(client, flow["id"], fixture="approval_handoff.json")
+    await _deploy(client, flow["id"])
+
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run",
+        json={
+            "input": {"betrag": 250000, "schwelle": 200000},
+            "callback_base_url": live_server,
+        },
+    )
+    assert response.status_code == 200, response.text
+    run = response.json()
+    assert run["status"] == "pending_approval"
+    assert "PENDING_HUMAN_APPROVAL" in run["output"]["result"]
+
+    response = await client.get("/api/approvals")
+    assert response.status_code == 200
+    tasks = response.json()
+    assert len(tasks) == 1
+    task = tasks[0]
+    assert task["run_id"] == run["id"]
+    assert task["status"] == "open"
+    assert task["payload"]["facts"]["betrag"] == 250000
+
+
+async def test_approval_handoff_auto_creates_no_task(client, lfx_server, live_server):
+    flow = await _create_flow(client, "freigabe-auto")
+    await _create_version(client, flow["id"], fixture="approval_handoff.json")
+    await _deploy(client, flow["id"])
+
+    response = await client.post(
+        f"/api/flows/{flow['id']}/run",
+        json={
+            "input": {"betrag": 50000, "schwelle": 200000},
+            "callback_base_url": live_server,
+        },
+    )
+    assert response.status_code == 200, response.text
+    assert response.json()["status"] == "completed"
+
+    response = await client.get("/api/approvals")
+    assert response.status_code == 200
+    assert response.json() == []
+
+
+async def test_approval_callback_contract(client, session):
+    from uuid import UUID
+
+    from app.flows import store as flow_store
+
+    flow = await _create_flow(client, "callback-target")
+    version = await _create_version(client, flow["id"])
+    version_obj = flow_store.get_version(session, UUID(version["id"]))
+
+    run = flow_store.create_run(session, version_obj, input={}, tenant_id="default")
+
+    response = await client.post(
+        "/api/approvals",
+        json={"run_id": str(run.id), "title": "bitte pruefen", "payload": {"x": 1}},
+    )
+    assert response.status_code == 201, response.text
+    task = response.json()
+    assert task["status"] == "open"
+    assert task["tenant_id"] == "default"
+    assert task["version_id"] == version["id"]
+
+    response = await client.get(f"/api/flows/runs/{run.id}")
+    assert response.json()["status"] == "pending_approval"
+
+    response = await client.post("/api/approvals", json={"run_id": str(run.id)})
+    assert response.status_code == 409
+
+    run2 = flow_store.create_run(session, version_obj, input={}, tenant_id="default")
+    response = await client.post(
+        "/api/approvals",
+        json={"run_id": str(run2.id), "continuation_flow_id": str(uuid4())},
+    )
+    assert response.status_code == 422
+
+    response = await client.post("/api/approvals", json={"run_id": str(uuid4())})
+    assert response.status_code == 404