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* docs: add design spec for lfx serve multi-flow startup and dynamic upload
* docs: add implementation plan for lfx serve multi-flow startup and dynamic upload
* feat(serve): add FlowRegistry for mutable in-process flow management
* feat(serve): add flow_id_from_content for content-based flow ID generation
* fix(test): update streaming tests to use FlowRegistry API
* test(serve): add upload endpoint tests
* feat(serve): add build_registry_from_directory and build_registry_from_paths helpers
* refactor(serve): remove dead _analyze_graph_structure and _generate_dynamic_run_description helpers
* feat(serve): accept directory and multiple file paths at startup; wire registry to serve_command
* [autofix.ci] apply automated fixes
* fix(serve): move traceback import to module level; remove planning docs from branch
* [autofix.ci] apply automated fixes
* fix(serve): deepcopy graph in stream_flow; use json.dumps for error stream payload
* test(serve): verify stream setup error payload is valid JSON with special characters
* [autofix.ci] apply automated fixes
* fix(serve): use load_flow_from_json directly in _load_graph_and_meta for clear error messages
* docs(serve): document multi-worker and persistence limitations on FlowRegistry
* feat(serve): allow starting server with no flows; accept full Langflow flow JSON on upload
- Remove the requirement for a flow path/JSON/stdin at startup; lfx serve
now starts with an empty FlowRegistry when no input is provided, ready
to accept flows via POST /flows/upload/
- UploadFlowRequest now accepts the full Langflow export JSON directly
(extra="allow", id field added) so callers can do -d @flow.json without
wrapping; load_flow_from_json receives the full dict and the flow's own
stable id is used when present
* fix(serve): harden upload endpoint and remove unused verbose_print param
- Pass body.model_dump(exclude={"replace"}) to load_flow_from_json instead of
body.model_dump(); keeps the top-level "data" key the function expects while
excluding the internal replace flag
- Set graph.flow_id after upload so it matches the registry key
- Return 409 Conflict on duplicate flow ID; add replace=true field to allow
explicit overwrite
- Remove unused verbose_print param from _load_graph_and_meta and update callers
- Clarify directory scan is top-level only (non-recursive) in CLI help text
- Add test_upload_full_export_as_body regression test: sends a complete Langflow
export JSON as the request body (curl -d @flow.json pattern) where body.data
has no nested "data" key — would have caught the KeyError('data') regression
* fix(serve): address PR review comments
- Restore .py script support: _load_graph_and_meta now dispatches to
load_graph_from_script for .py paths; CLI validation accepts .json and .py;
help text updated in both _running_commands.py and commands.py
- Fix flow ID collision in build_registry_from_paths: compute a shared common
root from all supplied paths so same-named files in different directories
get distinct UUIDv5 IDs instead of silently overwriting each other
- Harden FlowRegistry.add(): add overwrite=False parameter that raises
ValueError on duplicate IDs; startup paths keep default (collision = error),
upload endpoint passes overwrite=body.replace
- Add regression test: test_same_filename_in_different_dirs_gets_distinct_ids
- Update test_duplicate_add_replaces_graph to reflect new overwrite semantics
* test(serve): add unit tests for .py script path in serve command
- test_load_graph_and_meta_dispatches_to_script_loader_for_py: verifies
_load_graph_and_meta calls load_graph_from_script (not load_flow_from_json)
for .py paths, and that meta.title and relative_path are set correctly
- test_serve_command_accepts_py_file: end-to-end check that lfx serve my.py
reaches the server (exit_code == 0)
- test_serve_command_rejects_unsupported_extension: .txt and other unknown
extensions must exit non-zero with a helpful message
* [autofix.ci] apply automated fixes
* Add --no-env-fallback option to support scoped request_vars
* [autofix.ci] apply automated fixes
* feat(serve): filesystem-backed flow registry for multi-worker sharing
Adds a FlowStore abstraction with two implementations:
- NullFlowStore (default): in-memory only, existing behavior unchanged
- FilesystemFlowStore: persists each flow as {id}.json; writes are
atomic (tmp→rename); reads and deletes are TOCTOU-safe; path
traversal guard rejects unsafe flow IDs
FlowRegistry now delegates persistence to FlowStore:
- add(raw_json=...) writes to store when raw JSON is available
- get() falls through to store on cache miss, reconstructs + caches
- list_metas() merges in-memory and store-side entries
- remove() propagates deletion to store
- warm_from_store() pre-warms the in-memory cache at startup
New --flow-dir option on lfx serve activates the filesystem store.
All uvicorn workers pointing at the same directory serve the same
flows — use /tmp/lfx-flows for single-pod sharing or a PVC mount
for cross-pod sharing. Raw JSON is plumbed through _load_graph_and_meta
and both builder functions so startup-loaded .json flows are persisted
automatically; .py flows remain in-memory only.
* feat(serve): add --workers option for multi-worker uvicorn support
Adds --workers N to lfx serve, enabling multiple uvicorn processes to
share flows via --flow-dir.
serve_command is restructured from @syncify async to plain sync: all
async registry-building is extracted into _build_serve_registry() and
called via asyncio.run(), then uvicorn.run() handles the server.
For workers > 1, uvicorn requires an import string rather than an app
object. The factory create_serve_app() in serve_app.py reads
LFX_SERVE_FLOW_DIR and LFX_SERVE_NO_ENV_FALLBACK from env, pre-warms
from the shared FilesystemFlowStore, and returns a ready FastAPI app.
The parent sets those env vars unconditionally before dispatching.
For workers == 1, the pre-built app object is used directly (no change
to existing single-worker behavior). A warning is emitted when
--workers > 1 is used without --flow-dir since each worker would have
an isolated in-memory registry.
The startup panel flow count is now accurate for single-worker +
--flow-dir by calling warm_from_store() before printing.
* [autofix.ci] apply automated fixes
* [autofix.ci] apply automated fixes (attempt 2/3)
* [autofix.ci] apply automated fixes (attempt 3/3)
* fix(serve): remove no_args_is_help, drop verbose_print param, harden _safe_path
- Remove no_args_is_help=True from serve command so lfx serve with no
arguments starts with an empty registry instead of showing help
- Remove unused verbose_print parameter from create_multi_serve_app and
update all callers (14 call sites across tests)
- Wrap _safe_path's relative_to() check in try/except for a clear error
message; restructure delete() to use try/except/else (TRY300)
- Add TYPE_CHECKING guard for FlowStore annotation in commands.py; wrap
long --workers help string; restore FBT003 noqa on no_env_fallback
- Fix test_env_fallback_skipped_when_flag_true to allow logger's getenv
calls while still asserting the credential variable is never looked up
- Fix ARG002/D205/RUF059 lint issues in test files
* [autofix.ci] apply automated fixes
* fix(serve): resolve merge conflicts and clean up test section comments
* ruff - test updates
* fix(serve): cross-worker delete propagation and HTTP 500 for execution failures
Cross-worker stale cache (multi-worker DELETE bug):
- Add FlowStore.is_persistent to distinguish real stores from NullFlowStore
- Track _store_sourced in FlowRegistry for flows written to a persistent store
- get() re-reads the store for store-sourced flows to detect cross-worker deletes;
evicts and returns None if the file is gone
- list_metas() skips store-sourced flows whose store key is no longer present
- Add _evict() helper to clean up _flows, _store_meta_cache, _store_keys, _store_sourced
HTTP status for execution failures:
- POST /flows/{id}/run now returns HTTP 500 (not 200) when execution raises or
when the flow returns success=false; body is still RunResponse for debug detail
- Updated OpenAPI responses declaration: 500 now maps to RunResponse model
* fix(serve): harden multi-worker registry correctness and safety
- Add FlowAlreadyRegisteredError (ValueError subclass) so upload_flow
catches only the specific race-condition exception rather than any
ValueError from unrelated internals.
- Add _SERVE_ENV_PREFIX constant; rebuild LFX_SERVE_* env var names from
it and add try/finally cleanup so those vars are always deleted after
uvicorn.run() returns in multi-worker mode.
- Reject .py startup files when --workers > 1: Python graphs cannot be
serialized to the filesystem store so workers would silently start with
empty registries for those flows.
- Remove warm_from_store() from build_registry_from_paths/directory; the
builders no longer pre-warm to avoid double-loading when the startup dir
and flow-dir overlap. serve_command still warms for single-worker mode.
- Fix FlowRegistry.__len__ to delegate to list_metas() so store-only
flows (not yet cache-loaded) are counted; this makes the startup panel
and /health flow_count accurate for multi-worker + pre-placed files.
- Fix FlowRegistry.remove() to delete both the primary store key file and
any alternate-keyed file (UUID or stem), ensuring cross-worker DELETE
propagation: after a delete, every worker's next request to that flow
triggers the per-request stale check, reads None from the store, and
returns 404 regardless of which key its cache entry uses.
- Document the per-request stale check in FlowRegistry docstring with
latency guidance for network volumes vs. local tmpfs.
- Add tests for all of the above, including a cross-worker DELETE
propagation scenario validated by a live 2-worker integration test.
* fix(serve): load startup flows in every uvicorn worker via LFX_SERVE_STARTUP_PATHS
Previously, lfx serve flow.json --workers 4 silently dropped startup flows:
the parent loaded them into a NullFlowStore registry that workers never
inherited. Each worker called create_serve_app() fresh and started empty,
returning flow_count: 0 from /health and 404 for the startup flow.
Fix: before calling uvicorn.run() in multi-worker mode, set
LFX_SERVE_STARTUP_PATHS to the JSON-encoded list of resolved startup file
paths (or the inline-JSON temp file path). create_serve_app() reads this env
var and re-loads the startup flows independently in each worker process using
a ThreadPoolExecutor to avoid RuntimeError from asyncio.run() being called
inside uvicorn's already-running event loop.
Startup flows loaded this way live in each worker's in-memory registry.
Uploaded flows still require --flow-dir for cross-worker sharing (existing
warning preserved). The LFX_SERVE_* env vars are cleaned up after
uvicorn.run() returns via the existing prefix-sweep finally block.
Tests added:
- test_serve_command_sets_startup_paths_env_for_multi_worker: verifies
LFX_SERVE_STARTUP_PATHS is set before uvicorn.run() and cleaned up after
- TestCreateServeAppFactory: unit tests for create_serve_app() in all three
modes (empty start, with startup paths, empty paths list)
* fix(serve): fix 3 worker/store consistency issues
Issue 1 — redundant store writes with --flow-dir + startup files + workers > 1:
When flow_dir is set the parent already persisted startup flows to the store.
create_serve_app() was re-loading and re-writing them in every worker.
Fix: create_serve_app() now skips LFX_SERVE_STARTUP_PATHS when flow_dir is
set and relies solely on warm_from_store(). Similarly, serve_command now only
populates LFX_SERVE_STARTUP_PATHS when flow_dir is NOT set.
Issue 2 — .py restriction was too broad:
The error blocked .py + --workers > 1 even without --flow-dir, where each
worker can safely re-execute the .py via LFX_SERVE_STARTUP_PATHS. The error
now only fires when --flow-dir is also set (workers would skip startup paths
and warm_from_store, missing the .py flow entirely since it can't be stored).
Issue 3 — parent built FastAPI app for multi-worker then discarded it:
create_multi_serve_app() was called before the workers > 1 / else branch,
building a full FastAPI app that was never served in multi-worker mode.
Moved into the else branch so it's only built for single-worker.
Tests:
- test_create_serve_app_with_flow_dir_skips_startup_paths_uses_store:
asserts build_registry_from_paths NOT called when flow_dir is set;
flow comes from store via warm_from_store instead.
- test_create_serve_app_without_flow_dir_loads_startup_paths_from_files:
asserts flow IS loaded when no flow_dir.
- test_serve_command_does_not_set_startup_paths_when_flow_dir_set:
asserts LFX_SERVE_STARTUP_PATHS is [] when flow_dir is set.
- test_serve_command_allows_py_with_multiple_workers_no_flow_dir:
asserts .py + workers>1 + no flow_dir is allowed and path appears in env.
* test(serve): remove duplicate test and fix mislabeled test name
- Remove test_create_serve_app_loads_startup_paths: functionally identical
to test_create_serve_app_without_flow_dir_loads_startup_paths_from_files
(same setup, same assertions, added in a prior session).
- Rename test_verify_api_key_header_takes_precedence to
test_verify_api_key_query_param_takes_precedence: the test passes the
correct key as the query_param argument and the wrong key as header_param,
then asserts the query param value is returned — query param has precedence,
not header. The old name was the opposite of what the test actually checks.
* [autofix.ci] apply automated fixes
* fix(serve): fix concurrent request isolation and startup UX
Three bug fixes discovered via live QA:
1. Component.__deepcopy__ produced shallow copies of _outputs_map,
_edges, and _components, causing concurrent requests to share the
same Output objects across graph copies. Output.cache=True by
default: the first request's output.value was served to all
subsequent concurrent requests, producing identical responses for
different inputs. Fixed by deep-copying all three fields with memo.
2. POST /flows/upload/ without an explicit id used uuid5(content),
which is deterministic — two uploads of any flow with the same
nodes/edges structure always generated the same UUID and the second
always returned 409. Fixed by using uuid4() (random).
3. Startup CLI emitted emoji and exclamation-point decoration in the
serve banner and verbose output. Replaced with plain text.
* [autofix.ci] apply automated fixes
* fix(serve): address PR review comments
- Move 409 conflict check before load_flow_from_json+prepare so callers
with an explicit id don't pay the parse cost for a flow that will be
rejected anyway
- Remove unreachable FlowAlreadyRegisteredError catch: no await exists
between registry.get() and registry.add(), so asyncio cannot
interleave another request in that window
- Update FlowMeta.id and UploadFlowResponse.id field descriptions from
stale "Deterministic UUIDv5" to plain "Flow identifier (UUID)"
* test(serve): fix upload duplicate/replace tests after uuid4 change
Both tests relied on uuid5(content) determinism to generate the same
flow ID from identical data. With uuid4, each upload gets a fresh ID,
so duplicate detection was never triggered. Tests now supply an
explicit id field to exercise the 409/replace paths directly.
* fix(serve): address code review suggestions
- Fix test_write_is_atomic to glob for any *.tmp files rather than
checking a hardcoded filename that could never exist
- Remove incorrect noqa: B904 from validate_id_is_uuid (not in an
except block); use `from None` instead
- Add TTL cache (1 s) for FlowStore.list_ids() in FlowRegistry to
avoid one filesystem glob per /health request; mutations invalidate
immediately, warm_from_store and delete-scan bypass it
- Document the UUID/stem dual-key alias invariant on _flows
- Add test verifying create_serve_app() propagates load errors from
the ThreadPoolExecutor startup path (fail fast, not silent empty registry)
* [autofix.ci] apply automated fixes
* fix: lfx serve no_env_fallback, deepcopy cycle, cross-worker delete (#13297)
fix: address concurrency and isolation issues in lfx serve
- Re-apply no_env_fallback to the per-request graph copy in the run and
stream endpoints; deepcopy() drops graph.context so the flag was lost.
- Register the copy in memo before recursive deepcopy calls in
Component.__deepcopy__ so reference cycles are preserved.
- Check the store directly in list_metas() so cross-worker deletes are
reflected immediately instead of after the TTL cache window.
- Remove the redundant upload-conflict test (already covered by
test_upload_duplicate_without_replace_returns_409).
Also mark test secrets with allowlist pragmas and fix two docstring
lint warnings in the touched test file.
* [autofix.ci] apply automated fixes
* feat(lfx): WXO/TRM request-scoped variables for lfx serve (child of #13121) (#13327)
* feat(lfx): WXO/TRM request-scoped variables for lfx serve global_vars
Align lfx serve with the TRM/WXO credential contract on top of #13121:
- Parse LANGFLOW_REQUEST_VARIABLES from global_vars payloads
- ContextVar-backed lookup in VariableService (no os.environ mutation)
- Activate request scope during execute_graph_with_capture
Child of add-workers-and-upload-lfx (PR #13121).
* [autofix.ci] apply automated fixes
* fix(lfx): harden request-scoped variable resolution + add isolation t… (#13347)
fix(lfx): harden request-scoped variable resolution + add isolation tests
Addresses PR review of WXO/TRM request-scoped variables for lfx serve:
- service: honor no_env_fallback in VariableService so model/KB credential
resolution no longer falls back to os.environ under --no-env-fallback;
correct the get_variable precedence docstring (5-step interleaved order)
- request_scope: add a per-request no_env_fallback ContextVar; use precise
Token type; document the None-vs-empty scope contract
- common: activate/reset the no_env_fallback scope from graph.context
- runtime_variables: log (instead of silently swallowing) a malformed or
non-object LANGFLOW_REQUEST_VARIABLES blob; anchor the override comment to
the TRM contract
Tests:
- add request-scope concurrency isolation + no-env-fallback suite
- add execute_graph_with_capture wiring test (graph.context -> ContextVars)
- give TestGraphExecution mock graphs a real context, fixing 11 tests that
broke once the helper began reading graph.context
* [autofix.ci] apply automated fixes
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jordan Frazier <122494242+jordanrfrazier@users.noreply.github.com>
* Update use of stem alias tracking to ensure proper deletes
* fix(lfx): enforce no_env_fallback across all credential resolution paths
Closes credential-isolation gaps in lfx serve and hardens request-scoped
variable handling:
- VariableService: skip the process-wide LANGFLOW_REQUEST_VARIABLES env read
when env fallback is disabled (previously leaked process credentials for an
empty-global_vars request despite --no-env-fallback).
- Unified models: gate os.environ reads in get_api_key_for_provider and the
connection-config fallbacks in instantiation.py (WatsonX URL/project-id,
Ollama base-url, OpenRouter headers) on the no-env-fallback flag.
- run_until_complete: propagate the caller's contextvars into the worker
thread so request-scoped vars and the flag survive the thread hop.
- Request variables: serialize structured (dict/list) values as valid JSON and
drop nulls instead of producing lossy Python reprs or a truthy "None".
- FlowRegistry: extract the duplicated store-alias scan shared by add/remove.
Adds tests for request-scope isolation, credential/env gating, and contextvar
propagation.
* fix(lfx): close no_env_fallback credential leaks and harden serve isolation
- credentials: honor no_env_fallback in get_all_variables_for_provider so served
flows no longer leak process env (was defeating the _env_if_allowed guards in
instantiation.py via pre-filled provider_vars)
- loading: apply the no_env_fallback contract to table load_from_db column
resolution (sibling of load_from_env_vars, previously still read os.getenv)
- variable service: resolve request-scoped vars (exact name + x-langflow-global-var
alias) before env fallback so a caller's per-request credential is never shadowed
by a same-named process env var
- runtime_variables: flatten the LANGFLOW_REQUEST_VARIABLES blob into graph context
for parity between the ContextVar and load_from_db resolution paths
- flow_store: clean up the partial temp file when an atomic write fails
- commands: on multi-worker shutdown remove only the serve env vars we set, not the
whole LFX_SERVE_* namespace
- components: add check_component_env_writes lint banning os.environ writes; stop the
mem0 component from writing the OpenAI key into the process environment
* fix(lfx): contain corrupt flow-store files so one bad file can't crash worker startup
FilesystemFlowStore.read() only caught FileNotFoundError, so a corrupted/partial
{id}.json in a shared store (PVC corruption, an external writer killed mid-write)
raised JSONDecodeError. warm_from_store() calls get() for every store id at startup
with no per-file guard, so a single bad file would crash every worker's startup and
500 GET /flows.
- read(): catch JSONDecodeError/OSError/UnicodeDecodeError, log, return None (treat
as absent) so warm_from_store/list_metas/get skip it and other flows keep serving.
- warm_from_store(): skip+log a flow that fails to reconstruct (corrupt JSON, or valid
JSON referencing a component not available in this build) instead of aborting startup.
- tests: corrupt-JSON read returns None; warm_from_store skips unloadable flows.
* fix test -- request wins over env now
* fix test. mock graph context correctly
---------
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@logspace.ai>
Co-authored-by: Himavarsha <40851462+HimavarshaVS@users.noreply.github.com>
Langflow is a powerful platform for building and deploying AI-powered agents and workflows. It provides developers with both a visual authoring experience and built-in API and MCP servers that turn every workflow into a tool that can be integrated into applications built on any framework or stack. Langflow comes with batteries included and supports all major LLMs, vector databases and a growing library of AI tools.
✨ Highlight features
- Visual builder interface to quickly get started and iterate.
- Source code access lets you customize any component using Python.
- Interactive playground to immediately test and refine your flows with step-by-step control.
- Multi-agent orchestration with conversation management and retrieval.
- Deploy as an API or export as JSON for Python apps.
- Deploy as an MCP server and turn your flows into tools for MCP clients.
- Observability with LangSmith, LangFuse and other integrations.
- Enterprise-ready security and scalability.
🖥️ Langflow Desktop
Langflow Desktop is the easiest way to get started with Langflow. All dependencies are included, so you don't need to manage Python environments or install packages manually. Available for Windows and macOS.
⚡️ Quickstart
Install locally (recommended)
Requires Python 3.10–3.14 and uv (recommended package manager).
Install
From a fresh directory, run:
uv pip install langflow -U
The latest Langflow package is installed. For more information, see Install and run the Langflow OSS Python package.
Run
To start Langflow, run:
uv run langflow run
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That's it! You're ready to build with Langflow! 🎉
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Run from source
If you've cloned this repository and want to contribute, run this command from the repository root:
make run_cli
For more information, see DEVELOPMENT.md.
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Start a Langflow container with default settings:
docker run -p 7860:7860 langflowai/langflow:latest
Langflow is available at http://localhost:7860/. For configuration options, see the Docker deployment guide.
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