Dash Version 4.5.0

Added

• #4099 Streaming callbacks over HTTP now require shared storage and fail at server setup without it, instead of falling back to one connection per stream; WebSocket streaming callbacks do not need it.
• #4095 Make shared storage and the multiplexed streaming downlink opt-in (shared_storage= or DASH_SHARED_STORAGE), and move msgspec to a new dash[shared_storage] extra for the persistent LocalSharedStorage modes (dash[diskcache] and dash[redis] include it).
• #4026 Add DASH_SECRET_KEY so a hosting platform can give every worker and pod the same signing secret for page, background and stream tokens without editing the app (server.secret_key still wins and is not changed).
• #4026 Add DASH_SHARED_STORAGE to pick the shared-storage backend when the app does not pass shared_storage=: local, none, diskcache:///abs/path, or a redis:// / rediss:// URL.
• #4024 Add support for social media meta tags in regular Dash apps using app.title, app.description, and app.image.
• #3976 Add a new scrollToTop prop to dcc.Link to control whether the page scrolls to the top after client-side navigation. It defaults to True to preserve the existing behavior. Fixes #3974.
• #3947 Make plotly-cloud a default install dependency of Dash instead of an optional extra, so the plotly CLI and Dash's cloud integration work out of the box. The dash[cloud] extra is kept for backward compatibility.
• #3930 Add shared storage: a backend-agnostic cross-process state manager (key/value with optional TTL, plus ordered replayable pub/sub) via dash.ctx.shared_storage, started lazily. Ships LocalSharedStorage (in-memory with optional disk persistence), DiskcacheSharedStorage, and RedisSharedStorage for horizontally-scaled deployments; see .ai/ARCHITECTURE.md.
• #3931 Add streaming callbacks: an async def generator callback streams its yields to the browser as they are produced (dash.Patch yields apply incrementally). A browser's streams share one SharedWorker-hosted connection so they do not count against the per-host connection limit; closing a tab cancels its streams.
• #3977 Add partial WebSocket prop reads with get_prop(..., path=...). Closes #3975.
• #3765 Add opt-in partial pattern matching for callback Input, Output, and State via partial_pattern=True, so dictionary ID patterns can match component IDs with extra keys and combine with ALL/MATCH wildcards. Fixes #3764.
• #3880 Add experimental support for React 19 (default stays React 18.3.1); opt in with REACT_VERSION=19.2.4 or dash._dash_renderer._set_react_version("19.2.4"). Dash serves the umd-react package with a compatibility shim so component libraries built against React <=18 keep working; see .ai/ARCHITECTURE.md.
• #3925 Add optional callback request payload compression via compress_payload and compress_threshold callback parameters (default threshold 5,000 bytes), sending gzip payloads that Dash decompresses on Flask, FastAPI, and Quart. Fixes #3924.
• #3961 Added cursor position data (xPixel, yPixel) to dcc.Graph hoverData and clickData when hoveranywhere or clickanywhere is enabled in the figure.
• #3960 Rewrite dcc.Markdown and dcc.Link as Typescript components
• #3881 Added dash.remount, a wrapper for a callback-returned component that forces the renderer to remount it (resetting its internal state) instead of reconciling in place: the explicit way to reset a stateful component from a callback without changing its id.

Removed

• #3880 Remove React 16 support (16.14.0 is no longer an accepted value for REACT_VERSION / _set_react_version).
• #4039 Remove unnecessary Python version checks (pre 3.9).

Changed

• #4073 Move plotly-cloud back to the optional dash[cloud] extra (it was a default dependency in 4.5.0rc0/rc1), since it is not available on conda-forge.
• #4026 Log a warning, once per process, when a streaming request is refused because its stream token failed verification, which on multi-worker deployments usually means the workers do not share a signing secret.
• #3987 Forward FastAPI reload scope options (reload_dirs, reload_excludes, and reload_includes) to Uvicorn when reloading.
• #3986 Adjust _run_before_hooks in the fastapi backend to honor a response returned by a before_request function, matching the flask backend's behavior.

Fixed

• #4075 fastapi backend: run before_request hooks on every route of the Dash app (assets, hook routes, api_endpoint, pages, when mounted) and send a non-None hook result as the response, as on Flask. fastapi and quart also run them on the WebSocket handshake.
• #4075 Background callbacks without cache_by no longer share a result between requests with equal inputs (unread Diskcache results now expire after a day, or after expire when set, even with cache_by), and callbacks with the same source no longer share a cache key. build_cache_key takes a new callback_key argument.
• #4075 dcc.Location(refresh=True).href, html.Area.href and html.Base.href now block javascript: URLs like html.A.
• #4075 Pages path_template matching no longer errors or backtracks badly on paths with a newline.
• #4075 Add configure_mcp_server(cache_by=..., cache_maxsize=...) so apps whose layout or callbacks depend on the user can keep the MCP server's cached tool descriptions and initial values per user (128 users by default, None for no limit).
• #4052 Fix callbacks of removed components still firing after a callback returns None for children: the renderer now clears their paths. Fixes #4033.
• #4027 Support async def hook routes (dash.hooks.route) on all backends, stop hook routes from leaking the app context to the caller, and let hook routes and MCP read the request on the fastapi backend.
• #4053 Fix callbacks being registered twice under a reloader (e.g. uvicorn --reload) when Dash() is given an explicit name or is built by an app factory called from the main module. Fixes #3912.
• #3980 Fix the three before_request hooks (Dash._setup_server and the pages router_sync / router_async) publishing their "already done" guard flag before the setup work behind it had run. Under a multi-threaded WSGI worker such as gunicorn -k gthread (or under an ASGI worker for the async router), a second request arriving mid-setup could observe the flag already set, skip setup, then read registered_paths / callback_map / the pages router callback while they were still being registered - causing the first burst of component bundle requests after a restart to 500 with Error loading dependency. "<lib>" is not a registered library, or the pages router to hit DuplicateCallback when two workers raced past the guard. Each hook body now runs under a lock (threading.Lock for the two sync hooks, an asyncio.Lock bound to the running loop for the async router) and only publishes the flag after all work completes. Fixes #3971.
• #3944 Fix dash.testing runner backend detection for wrapped FastAPI/Quart servers so threaded Flask-only options are not passed to ASGI runners.
• #3955 Unpin selenium in the testing requirements (was capped at <=4.2.0 from 2022) and require >=4.11.0, so it can drive current stable Chrome via Selenium Manager and stop the widespread CI flakiness.
• #3881 Speed up the renderer layout crawl (crawlLayout and its callers) by replacing curried-ramda path/pathOr lookups with direct property access on the hot path: ~16% faster Patch().append() into a large container, with no behavior change.
• #3881 Fix pattern-matching (MATCH/ALL/ALLSMALLER) callbacks getting quadratically slower as matching components grow; a new O(1) id->path index cuts an ALL update over 400 components from ~580ms to ~140ms (~4x), with no app changes.
• #3941 Fix the FastAPI and Quart backends opening a WebSocket connection on every page load even for apps with no WebSocket callbacks; the socket now ope...

Dash Version 4.5.0rc2

Removed

• #4039 Remove unnecessary Python version checks (pre 3.9).

Changed

• #4073 Move plotly-cloud back to the optional dash[cloud] extra (it was a default dependency in 4.5.0rc0/rc1), since it is not available on conda-forge.

Fixed

• #4075 fastapi backend: run before_request hooks on every route of the Dash app (assets, hook routes, api_endpoint, pages, when mounted) and send a non-None hook result as the response, as on Flask. fastapi and quart also run them on the WebSocket handshake.
• #4075 Background callbacks without cache_by no longer share a result between requests with equal inputs (unread Diskcache results now expire after a day, or after expire when set, even with cache_by), and callbacks with the same source no longer share a cache key. build_cache_key takes a new callback_key argument.
• #4075 dcc.Location(refresh=True).href, html.Area.href and html.Base.href now block javascript: URLs like html.A.
• #4075 Pages path_template matching no longer errors or backtracks badly on paths with a newline.
• #4075 Add configure_mcp_server(cache_by=..., cache_maxsize=...) so apps whose layout or callbacks depend on the user can keep the MCP server's cached tool descriptions and initial values per user (128 users by default, None for no limit).
• #4052 Fix callbacks of removed components still firing after a callback returns None for children: the renderer now clears their paths. Fixes #4033.

Updated

• npm packages: dash-renderer 3.5.2, dash-core-components / dash-html-components 4.5.2, dash-table 7.5.2.
• Dependency and CI updates (#4072, #4079).

Dash Version 4.5.0rc1

Added

• #4026 Add DASH_SECRET_KEY so a hosting platform can give every worker and pod the same signing secret for page, background and stream tokens without editing the app (server.secret_key still wins and is not changed).
• #4026 Add DASH_SHARED_STORAGE to pick the shared-storage backend when the app does not pass shared_storage=: local, none, diskcache:///abs/path, or a redis:// / rediss:// URL.
• #4024 Add support for social media meta tags in regular Dash apps using app.title, app.description, and app.image.
• #3976 Add a new scrollToTop prop to dcc.Link to control whether the page scrolls to the top after client-side navigation. It defaults to True to preserve the existing behavior. Fixes #3974.

Changed

• #4026 Log a warning, once per process, when a streaming request is refused because its stream token failed verification, which on multi-worker deployments usually means the workers do not share a signing secret.
• #3987 Forward FastAPI reload scope options (reload_dirs, reload_excludes, and reload_includes) to Uvicorn when reloading.

Fixed

• #4027 Support async def hook routes (dash.hooks.route) on all backends, stop hook routes from leaking the app context to the caller, and let hook routes and MCP read the request on the fastapi backend.
• #4053 Fix callbacks being registered twice under a reloader (e.g. uvicorn --reload) when Dash() is given an explicit name or is built by an app factory called from the main module. Fixes #3912.
• #4023 Fix extra callback registrations when an app runs from the parent directory: python app/app.py, where the script shares its folder's name, registered its callbacks twice, and python app/main.py imported a sibling app/app.py as the parent package and registered its callbacks too (regression introduced in 4.4.1 by #3883). Fixes #4011.
• #3980 Fix the three before_request hooks (Dash._setup_server and the pages router_sync / router_async) publishing their "already done" guard flag before the setup work behind it had run. Under a multi-threaded WSGI worker such as gunicorn -k gthread (or under an ASGI worker for the async router), a second request arriving mid-setup could observe the flag already set, skip setup, then read registered_paths / callback_map / the pages router callback while they were still being registered - causing the first burst of component bundle requests after a restart to 500 with Error loading dependency. "<lib>" is not a registered library, or the pages router to hit DuplicateCallback when two workers raced past the guard. Each hook body now runs under a lock (threading.Lock for the two sync hooks, an asyncio.Lock bound to the running loop for the async router) and only publishes the flag after all work completes. Fixes #3971.
• #4057 Fixed background callbacks to update set_props instead of replacing. Fixes #3104.
• #3923 Fix a blank page and SyntaxError in the browser when a dict component ID has a dot in one of its values. Fixes #3480.
• #4014 Disable autocomplete in DatePickerSingle and DatePickerRange inputs. Fixes #4009.
• #4007 Fix page loads failing with a 500 error on Windows when Dash is imported from an extended-length (\\?\) path, as in JupyterLab Desktop. Package resource paths are now joined with the OS separator instead of /. Fixes #3002.

Dash Version 4.5.0rc0

Added

• #3947 Make plotly-cloud a default install dependency of Dash instead of an optional extra, so the plotly CLI and Dash's cloud integration work out of the box. The dash[cloud] extra is kept for backward compatibility.
• #3930 Add shared storage: a backend-agnostic cross-process state manager (key/value with optional TTL, plus ordered replayable pub/sub) on every app via dash.ctx.shared_storage, started lazily and disabled with shared_storage=None. Ships LocalSharedStorage (default, in-memory with optional disk persistence), DiskcacheSharedStorage, and RedisSharedStorage for horizontally-scaled deployments; see .ai/ARCHITECTURE.md.
• #3931 Add streaming callbacks: an async def generator callback streams its yields to the browser as they are produced (dash.Patch yields apply incrementally). A browser's streams share one SharedWorker-hosted connection so they do not count against the per-host connection limit; closing a tab cancels its streams.
• #3977 Add partial WebSocket prop reads with get_prop(..., path=...). Closes #3975.
• #3765 Add opt-in partial pattern matching for callback Input, Output, and State via partial_pattern=True, so dictionary ID patterns can match component IDs with extra keys and combine with ALL/MATCH wildcards. Fixes #3764.
• #3646 Add experimental support for React 19 (default stays React 18.3.1); opt in with REACT_VERSION=19.2.4 or dash._dash_renderer._set_react_version("19.2.4"). Dash serves the umd-react package with a compatibility shim so component libraries built against React <=18 keep working; see .ai/ARCHITECTURE.md.
• #3925 Add optional callback request payload compression via compress_payload and compress_threshold callback parameters (default threshold 5,000 bytes), sending gzip payloads that Dash decompresses on Flask, FastAPI, and Quart. Fixes #3924.
• #3961 Added cursor position data (xPixel, yPixel) to dcc.Graph hoverData and clickData when hoveranywhere or clickanywhere is enabled in the figure.
• #3960 Rewrite dcc.Markdown and dcc.Link as Typescript components
• #3881 Added dash.remount, a wrapper for a callback-returned component that forces the renderer to remount it (resetting its internal state) instead of reconciling in place: the explicit way to reset a stateful component from a callback without changing its id.

Removed

• #3646 Remove React 16 support (16.14.0 is no longer an accepted value for REACT_VERSION / _set_react_version).

Changed

• #3986 Adjust _run_before_hooks in the fastapi backend to honor a response returned by a before_request function, matching the flask backend's behavior.

Fixed

• #3944 Fix dash.testing runner backend detection for wrapped FastAPI/Quart servers so threaded Flask-only options are not passed to ASGI runners.
• #3955 Unpin selenium in the testing requirements (was capped at <=4.2.0 from 2022) and require >=4.11.0, so it can drive current stable Chrome via Selenium Manager and stop the widespread CI flakiness.
• #3881 Speed up the renderer layout crawl (crawlLayout and its callers) by replacing curried-ramda path/pathOr lookups with direct property access on the hot path: ~16% faster Patch().append() into a large container, with no behavior change.
• #3881 Fix pattern-matching (MATCH/ALL/ALLSMALLER) callbacks getting quadratically slower as matching components grow; a new O(1) id->path index cuts an ALL update over 400 components from ~580ms to ~140ms (~4x), with no app changes.
• #3941 Fix the FastAPI and Quart backends opening a WebSocket connection on every page load even for apps with no WebSocket callbacks; the socket now opens only when actually needed. Fixes #3939.
• #3916 Fixed a regression where dragging multiple files into dcc.Upload would upload only the first file when multiple=True
• #3922 Fix dcc.Input(type="number") stepper behavior when only min is set.
• #3925 Use the proxied url as the Jupyter server url so DASH_PROXY is honored by the external url and inline iframe in notebooks.
• #3938 Fix dcc.Patch() re-running the initial callbacks of components already on the page (including every MATCH/ALL element) and wiping their user-edited persisted values. Fixes #3681 and #3937
• #3960 Fix dcc.Markdown not rendering <dccLink /> by using newer dependencies
• #3846 Fix callback-returned children being unmounted and remounted on every update instead of reconciled in place, which reset component state and slowed large subtrees 3-4x (regression introduced in 4.2.0 by #3570); use dash.remount to force a remount.
• #3881 Fix components rendered as props (eg. dcc.Dropdown option labels, dcc.Tab labels) crashing or failing to update when the host subtree was replaced by a callback; out-of-tree ExternalWrapper components now re-insert themselves and update in place.
• #3929 Fix components that set their own initial state on mount (eg. dash-bootstrap-components Tabs) not applying it on first render, because descendant layout hashes were reset on the first fresh render (regression introduced in 4.2.0 by #3570).
• #3948 Fix page getting progressively slower as callbacks append children

v4.4.1

Fixed

• #3902 Fix background callbacks trusting the client-supplied job/oldJob/cancelJob and cacheKey query parameters verbatim, which let an unauthenticated client terminate an arbitrary process (with DiskcacheManager, by sending its PID) or read and delete arbitrary result-cache entries. The cacheKey/job handles are now HMAC-signed by the server and bound to a per-page-load token, so forged or replayed values are rejected. Handles stay opaque to the renderer, so no app or callback code changes are required.
• 3883 Fix callbacks being registered twice when running the app file as a script with a server that loads it by import string, e.g. uvicorn.run("app:server", reload=True) with backend="fastapi". The spawned worker re-executes the main module as __mp_main__ and the import string then executed the same file a second time, duplicating every callback in _dash-dependencies and triggering Duplicate callback outputs errors in the renderer. Dash() now pre-registers the running main module in sys.modules under its canonical import name so the second import reuses it instead of re-executing the file. Fixes #3818.
• 3885 Fix Flask-WTF CSRFProtect (and Quart-WTF) exemptions breaking after the backend refactor. The callback dispatch view is now exposed with the fully-qualified name dash.dash.dispatch again, so csrf._exempt_views.add("dash.dash.dispatch") works as it did in Dash 4.1.0. Fixes #3827.
• #3882 Fix dcc.Graph user interactions (pan, zoom, edited shapes & annotations, ...) being reverted by a subsequent Patch update, by syncing all relayout changes back to the figure prop instead of only shapes. Fixes #3810.
• #3903 Fix missing comm dependency, fix #3657.
• Updated radix-ui to fix #3786

v4.4.0

Added

• #3826 WebSocket callback dispatch no longer lets long-lived callbacks limit the number of concurrent users. Async callbacks (including session-persistent ones) run directly on the connection event loop instead of occupying a worker thread, and synchronous callbacks run on a shared ThreadPoolExecutor whose size is configurable via the new websocket_max_workers argument to Dash (default 4). A synchronous persistent (no-output) callback now warns at registration since it would tie up a worker thread.

Fixed

• #3861 Fix synchronous WebSocket callbacks not inheriting ContextVar values bound by ASGI middleware. copy_context() is now captured on the event-loop thread before the callback is submitted to the thread pool, instead of inside the worker thread where only default values were visible.
• #3779 Fix dash.testing Browser.get_logs() returning None on non-Chrome webdrivers, which broke assertions like assert dash_duo.get_logs() == []. It now returns [], matching the Chrome code path.
• #3822 Fix UnboundLocalError for user_callback_output in async background callbacks (Celery and Diskcache managers) when the callback raises PreventUpdate or another exception before the variable is assigned.
• #3819 Fix RuntimeError: No active request in context when a non-Dash path falls through to the FastAPI catch-all route. Fixes #3812.
• #3838 Replace mcp dependency with inline types.
• #3824 Fix dash.testing ThreadedRunner.stop() hanging at teardown for Quart apps. Fixes #3823.
• #3425 dcc.DatePicker: Fix updatemode="bothdates" not always respected

Changed

• Drop support for Python 3.8 (end-of-life since October 2024). The minimum supported version is now Python 3.9.

v4.3.0

Added

• #3796 MCP: Add configure_mcp_server() to toggle which content the MCP server exposes (include_layout, include_callbacks, include_clientside_callbacks, include_pages, expose_callback_docstrings). Only the parameters explicitly passed are updated; omitted parameters retain their current value.
• #3710 MCP: Framework utilities, types for interacting with layout
• #3711 MCP: CallbackAdapter for representing callback-related data in MCP-friendly format
• #3712 MCP: Resources for exposing app layout, components, and pages
• #3731 MCP: Expose callbacks as Tools
• #3747 MCP: Support pattern-matching callbacks in Tools
• #3748 MCP: Format callback results for LLM consumption (rendered graphs, markdown tables)
• #3749 MCP: get_dash_component Tool and callback execution
• #3750 MCP: Server routes, mcp_enabled function decorator, and Streamable HTTP transport
• #3766 MCP: Support background callbacks in Tools

Changed

• #3796 MCP: Remove the mcp_expose_docstrings Dash() constructor argument; callback docstring exposure is now controlled via configure_mcp_server(expose_callback_docstrings=...).

Fixed

• #3817 Fix background callback context serialisation for non-dict request args on the FastAPI and Quart backends. Fixes #3816.
• #3805 Fix FastAPI POST routes deadlock caused by middleware consuming request body. Fixes #3801.
• #3813 Fix websockets using incorrect path when deployed behind a proxy
• #3830 MCP: Respond to the Streamable HTTP GET (SSE) request with an empty event stream instead of 405 Method Not Allowed

v4.2.0

[4.2.0] - 2026-06-01 - The Freedom Update

This release marks a major milestone for Dash, bringing unprecedented flexibility to how you build and deploy your applications.

🚀 Multiple Backend Support

Dash is no longer tied to Flask. You can now run your Dash apps on FastAPI or Quart, or even bring your own backend implementation:

# FastAPI backend
app = Dash(__name__, backend="fastapi")

# Quart backend (async-native)
app = Dash(__name__, backend="quart")

# Or use an existing server
from fastapi import FastAPI
server = FastAPI()
app = Dash(__name__, server=server)

Install with pip install dash[fastapi] or pip install dash[quart].

⚡ Websocket Callbacks

Real-time, bidirectional communication is here. Websocket callbacks enable persistent connections for live updates without polling:

@callback(
    Output("live-output", "children"),
    Input("trigger", "n_clicks"),
    websocket=True,
    persistent=True
)
def live_updates(n_clicks):
    ws = ctx.websocket
    while True:
        data = fetch_live_data()
        ws.send(Output("live-output", "children", data))
        time.sleep(1)

🔓 Relaxed Pattern Matching Rules

MATCH wildcards are now allowed in Input and State even when your Output has no wildcards, making dynamic UIs simpler to build:

@callback(
    Output("summary", "children"),  # Fixed ID output
    Input({"type": "item", "index": MATCH}, "value")  # MATCH input - now allowed!
)
def update_summary(value):
    return f"Selected: {value}"

---

Added

• #3783 Add batching/debouncing for websocket set_props messages to reduce lag when updating multiple components in a loop. Configurable via websocket_batch_delay (default 5ms, set to 0 to disable).
• #3669 Selection for DataTable cleared with custom action settings.
• #3680 Added search_order prop to Dropdown to allow users to preserve original option order during search.
• #3745 Added csrf_token_name and csrf_header_name config options to allow configuring the CSRF cookie and header names. Fixes #729.
• #3797 Improved websocket callback management with heartbeat configuration and proper reconnection handling.
• #3523 Fall back to background callback function names if source cannot be found.
• #3771 Add persistent callbacks and no inputs/no outputs callback support.
• #3742 Add websocket callbacks to fastapi and quart backends.
• #3737 Add displayNotifier to dcc.Graph config props.

Changed

• #3746 Improve static typing for dash.callback by preserving wrapped callback signatures, and add callback typing coverage in compliance plus new callback decorator unit and integration tests. Fixes #3691.
• Rename ctx.get_websocket to ctx.websocket.
• Add threadpool for running websocket callbacks.

Fixed

• #3690 Fix dcc.Input when min or max is set to None.
• #3723 Fix misaligned dcc.Slider marks when some labels are empty strings.
• #3738 Add missing stacklevel=2 to warnings.warn() calls so warnings report the caller's location instead of internal Dash source lines.
• #3740 Fix cannot tab into dropdowns in Safari.
• #3756 Allow MATCH in Input/State when the callback's Output has no wildcards (fixed-id Output, no Output, or ALL-only wildcard Output). ALLSMALLER still requires a corresponding MATCH in an Output. Fixes #2462.
• #3768 Improved Dropdown search performance for large options lists.
• #3759 Fix the issue where Patch objects cannot be updated via set_props() in websocket callback. Fix #3742.
• #3789 Fixed extra wrapper in DatePickerRange and DatePickerSingle causing styling and layout issues.
• #3799 Fixed dropdown crash when filtering large datasets with component-based labels by using stable item keys for virtualized rows.
• #3785 Fix patch with dcc.Graph figure. Fix dcc.Graph not sending duplicate clicks because it had the same payload by adding a timestamp in the click event object.
• #3798 Fix blueprint registering and double init when using flask run command. Fixes #3787.
• #3734 Fix websocket used in the same FastAPI server. Fixes #3636.
• #3668 Fix FastAPI url paths order. Fixes #3667.
• #3641 Fix dcc.Loading spinner not triggering when callback Output uses the ALL wildcard. Fixes #3619.
• #3570 Fix components not remounting when passed from a parent object. Fixes #3330.

v4.3.0rc0

Added

• #3710 MCP: Framework utilities, types for interacting with layout
• #3711 MCP: CallbackAdapter for representing callback-related data in MCP-friendly format
• #3712 MCP: Resources for exposing app layout, components, and pages
• #3731 MCP: Expose callbacks as Tools
• #3747 MCP: Support pattern-matching callbacks in Tools
• #3748 MCP: Format callback results for LLM consumption (rendered graphs, markdown tables)
• #3749 MCP: get_dash_component Tool and callback execution
• #3750 MCP: Server routes, mcp_enabled function decorator, and Streamable HTTP transport
• #3766 MCP: Support background callbacks in Tools

v4.2.0rc3

• #3771 Add persistent callbacks and no inputs/no outputs callback support.
• Rename ctx.get_websocket to ctx.websocket