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1# Copyright (c) 2017-2022 Cloudflare, Inc.
2# Licensed under the Apache 2.0 license found in the LICENSE file or at:
3#     https://opensource.org/licenses/Apache-2.0
4 
5@0x8b3d4aaa36221ec8;
6 
7using Cxx = import "/capnp/c++.capnp";
8$Cxx.namespace("workerd");
9$Cxx.allowCancellation;
10 
11struct ImpliedByAfterDate @0x8f8c1b68151b6cff {
12  # Annotates a compatibility flag to indicate that it is implied by the enablement
13  # of the named flag(s) after the specified date.
14  union {
15    name @0 :Text;
16    names @2 :List(Text);
17  }
18  date @1 :Text;
19}
20 
21struct CompatibilityFlags @0x8f8c1b68151b6cef {
22  # Flags that change the basic behavior of the runtime API, especially for
23  # backwards-compatibility with old bugs.
24  #
25  # Note: At one time, this was called "FeatureFlags", and many places in the codebase still call
26  #   it that. We could do a mass-rename but there's some tricky spots involving JSON
27  #   communications with other systems... I'm leaving it for now.
28 
29  annotation compatEnableFlag @0xb6dabbc87cd1b03e (field) :Text;
30  annotation compatDisableFlag @0xd145cf1adc42577c (field) :Text;
31  # Compatibility flag names which enable or disable this feature, overriding what the worker's
32  # compatibility date would otherwise set.
33  #
34  # An enable-flag is used to enable the feature before it becomes the default, probably for
35  # testing purposes. All features probably should have an enable-flag defined first, then get
36  # a date assigned once testing is done.
37  #
38  # A disable-flag is used when a worker needs to keep long-term backwards compatibility with one
39  # bug but doesn't want to hold back everything else. This is hopefully rare! Most features
40  # should have a disable-flag defined.
41 
42  annotation compatEnableDate @0x91a5d5d7244cf6d0 (field) :Text;
43  # The compatibility date (date string, like "2021-05-17") after which this flag should always
44  # be enabled.
45 
46  annotation compatEnableAllDates @0x9a1d37c8030d9418 (field) :Void;
47  # All compatibility dates should start using the flag as enabled.
48  # NOTE: This is almost NEVER what you actually want because you're most likely breaking back
49  # compat. Note that workers uploaded with the flag will fail validation, so this will break
50  # uploads for anyone still using the flag.
51  #
52  # However, this is useful in some cases where the back compat you're breaking is for
53  # pre-release users who you've communicated this in advance to. Turning this on for a field
54  # will also cause test failures in compatibility-date-test.c++ and validation-test.ekam-rule
55  # because the default set of flags that are enabled changes from being the empty set to including
56  # this flag (at some point presumably it also means you're removing the compat flags at some point
57  # and you'll have to repeat this exercise).
58 
59  annotation neededByFl @0xbd23aff9deefc308 (field) :Void;
60  # A tag to tell us which fields we'll need to propagate to FL on subrequests and responses.
61  #
62  # ("FL" refers to Cloudflare's HTTP proxy stack which is used for all outbound requests. Except
63  # for `brotliContentEncoding`, flags with this annotation have no effect when `workerd` is used
64  # outside of Cloudflare.)
65 
66  annotation experimental @0xe3e5a63e76284d88 (field):Void;
67  # Flags with this annotation can only be used when workerd is run with the --experimental flag.
68  # These flags may be subject to change or even removal in the future with no warning -- they are
69  # not covered by Workers' usual backwards-compatibility promise. Experimental flags cannot be
70  # used in Workers deployed on Cloudflare except by test accounts belonging to Cloudflare team
71  # members.
72 
73  annotation impliedByAfterDate @0xe3e5a63e76284d89 (field) :ImpliedByAfterDate;
74 
75  annotation pythonSnapshotRelease @0xef74c0cc5d18cc0c (field) :Void;
76  # This annotation marks a compat flag as introducing a potentially breaking change to Python
77  # memory snapshots. See the doc comment for the `PythonSnapshotRelease` struct above for more
78  # details.
79 
80  formDataParserSupportsFiles @0 :Bool
81      $compatEnableFlag("formdata_parser_supports_files")
82      $compatEnableDate("2021-11-03")
83      $compatDisableFlag("formdata_parser_converts_files_to_strings");
84  # Our original implementations of FormData made the mistake of turning files into strings.
85  # We hadn't implemented `File` yet, and we forgot.
86 
87  fetchRefusesUnknownProtocols @1 :Bool
88      $compatEnableFlag("fetch_refuses_unknown_protocols")
89      $compatEnableDate("2021-11-10")
90      $compatDisableFlag("fetch_treats_unknown_protocols_as_http");
91  # Our original implementation of fetch() incorrectly accepted URLs with any scheme (protocol).
92  # It happily sent any scheme to FL in the `X-Forwarded-Proto` header. FL would ignore any
93  # scheme it didn't recgonize, which effectively meant it treated all schemes other than `https`
94  # as `http`.
95 
96  esiIncludeIsVoidTag @2 :Bool
97      $compatEnableFlag("html_rewriter_treats_esi_include_as_void_tag");
98  # Our original implementation of `esi:include` treated it as needing an end tag.
99  # We're worried that fixing this could break existing workers.
100 
101  obsolete3 @3 :Bool;
102 
103  durableObjectFetchRequiresSchemeAuthority @4 :Bool
104      $compatEnableFlag("durable_object_fetch_requires_full_url")
105      $compatEnableDate("2021-11-10")
106      $compatDisableFlag("durable_object_fetch_allows_relative_url");
107  # Our original implementation allowed URLs without schema and/or authority components and
108  # interpreted them relative to "https://fake-host/".
109 
110  streamsByobReaderDetachesBuffer @5 :Bool
111      $compatEnableFlag("streams_byob_reader_detaches_buffer")
112      $compatEnableDate("2021-11-10")
113      $compatDisableFlag("streams_byob_reader_does_not_detach_buffer");
114  # The streams specification dictates that ArrayBufferViews that are passed in to the
115  # read() operation of a ReadableStreamBYOBReader are detached, making it impossible
116  # for user code to modify or observe the data as it is being read. Our original
117  # implementation did not do that.
118 
119  streamsJavaScriptControllers @6 :Bool
120      $compatEnableFlag("streams_enable_constructors")
121      $compatEnableDate("2022-11-30")
122      $compatDisableFlag("streams_disable_constructors");
123  # Controls the availability of the work in progress new ReadableStream() and
124  # new WritableStream() constructors backed by JavaScript underlying sources
125  # and sinks.
126 
127  jsgPropertyOnPrototypeTemplate @7 :Bool
128      $compatEnableFlag("workers_api_getters_setters_on_prototype")
129      $compatEnableDate("2022-01-31")
130      $compatDisableFlag("workers_api_getters_setters_on_instance");
131  # Originally, JSG_PROPERTY registered getter/setters on an objects *instance*
132  # template as opposed to its prototype template. This broke subclassing at
133  # the JavaScript layer, preventing a subclass from correctly overriding the
134  # superclasses getters/setters. This flag controls the breaking change made
135  # to set those getters/setters on the prototype template instead.
136 
137  minimalSubrequests @8 :Bool
138      $compatEnableFlag("minimal_subrequests")
139      $compatEnableDate("2022-04-05")
140      $compatDisableFlag("no_minimal_subrequests")
141      $neededByFl;
142  # Turns off a bunch of redundant features for outgoing subrequests from Cloudflare. Historically,
143  # a number of standard Cloudflare CDN features unrelated to Workers would sometimes run on
144  # Workers subrequests despite not making sense there. For example, Cloudflare might automatically
145  # apply gzip compression when the origin server responds without it but the client supports it.
146  # This doesn't make sense to do when the response is going to be consumed by Workers, since the
147  # Workers Runtime is typically running on the same machine. When Workers itself returns a
148  # response to the client, Cloudflare's stack will have another chance to apply gzip, and it
149  # makes much more sense to do there.
150 
151  noCotsOnExternalFetch @9 :Bool
152      $compatEnableFlag("no_cots_on_external_fetch")
153      $compatEnableDate("2022-03-08")
154      $compatDisableFlag("cots_on_external_fetch")
155      $neededByFl;
156  # Tells FL not to use the Custom Origin Trust Store for grey-cloud / external subrequests. Fixes
157  # EW-5299.
158 
159  specCompliantUrl @10 :Bool
160      $compatEnableFlag("url_standard")
161      $compatEnableDate("2022-10-31")
162      $compatDisableFlag("url_original");
163  # The original URL implementation based on kj::Url is not compliant with the
164  # WHATWG URL Standard, leading to a number of issues reported by users. Unfortunately,
165  # making it spec compliant is a breaking change. This flag controls the availability
166  # of the new spec-compliant URL implementation.
167 
168  globalNavigator @11 :Bool
169      $compatEnableFlag("global_navigator")
170      $compatEnableDate("2022-03-21")
171      $compatDisableFlag("no_global_navigator");
172 
173  captureThrowsAsRejections @12 :Bool
174      $compatEnableFlag("capture_async_api_throws")
175      $compatEnableDate("2022-10-31")
176      $compatDisableFlag("do_not_capture_async_api_throws");
177  # Many worker APIs that return JavaScript promises currently throw synchronous errors
178  # when exceptions occur. Per the Web Platform API specs, async functions should never
179  # throw synchronously. This flag changes the behavior so that async functions return
180  # rejections instead of throwing.
181 
182  r2PublicBetaApi @13 :Bool
183      $compatEnableFlag("r2_public_beta_bindings")
184      $compatDisableFlag("r2_internal_beta_bindings")
185      $compatEnableAllDates;
186  # R2 public beta bindings are the default.
187  # R2 internal beta bindings is back-compat.
188 
189  obsolete14 @14 :Bool
190      $compatEnableFlag("durable_object_alarms");
191  # Used to gate access to durable object alarms to authorized workers, no longer used (alarms
192  # are now enabled for everyone).
193 
194  noSubstituteNull @15 :Bool
195      $compatEnableFlag("dont_substitute_null_on_type_error")
196      $compatEnableDate("2022-06-01")
197      $compatDisableFlag("substitute_null_on_type_error");
198  # There is a bug in the original implementation of the kj::Maybe<T> type wrapper
199  # that had it inappropriately interpret a nullptr result as acceptable as opposed
200  # to it being a type error. Enabling this flag switches on the correct behavior.
201  # Disabling the flag switches back to the original broken behavior.
202 
203  transformStreamJavaScriptControllers @16 :Bool
204      $compatEnableFlag("transformstream_enable_standard_constructor")
205      $compatEnableDate("2022-11-30")
206      $compatDisableFlag("transformstream_disable_standard_constructor");
207  # Controls whether the TransformStream constructor conforms to the stream standard or not.
208  # Must be used in combination with the streamsJavaScriptControllers flag.
209 
210  r2ListHonorIncludeFields @17 :Bool
211      $compatEnableFlag("r2_list_honor_include")
212      $compatEnableDate("2022-08-04");
213  # Controls if R2 bucket.list honors the `include` field as intended. It previously didn't
214  # and by default would result in http & custom metadata for an object always being returned
215  # in the list.
216 
217  exportCommonJsDefaultNamespace @18 :Bool
218      $compatEnableFlag("export_commonjs_default")
219      $compatEnableDate("2022-10-31")
220      $compatDisableFlag("export_commonjs_namespace");
221  # Unfortunately, when the CommonJsModule type was implemented, it mistakenly exported the
222  # module namespace (an object like `{default: module.exports}`) rather than exporting only
223  # the module.exports. When this flag is enabled, the export is fixed.
224 
225  obsolete19 @19 :Bool
226      $compatEnableFlag("durable_object_rename")
227      $experimental;
228  # Obsolete flag. Has no effect.
229 
230  webSocketCompression @20 :Bool
231      $compatEnableFlag("web_socket_compression")
232      $compatEnableDate("2023-08-15")
233      $compatDisableFlag("no_web_socket_compression");
234  # Enables WebSocket compression. Without this flag, all attempts to negotiate compression will
235  # be refused for scripts prior to the compat date, so WebSockets will never use compression.
236  # With this flag, the system will automatically negotiate the use of the permessage-deflate
237  # extension where appropriate. The Worker can also request specific compression settings by
238  # specifying a valid Sec-WebSocket-Extensions header, or setting the header to the empty string
239  # to explicitly request that no compression be used.
240 
241  nodeJsCompat @21 :Bool
242      $compatEnableFlag("nodejs_compat")
243      $compatDisableFlag("no_nodejs_compat");
244  # Enables nodejs compat imports in the application.
245 
246  obsolete22 @22 :Bool
247      $compatEnableFlag("tcp_sockets_support");
248  # Used to enables TCP sockets in workerd.
249 
250  specCompliantResponseRedirect @23 :Bool
251      $compatEnableDate("2023-03-14")
252      $compatEnableFlag("response_redirect_url_standard")
253      $compatDisableFlag("response_redirect_url_original");
254  # The original URL implementation based on kj::Url is not compliant with the
255  # WHATWG URL Standard, leading to a number of issues reported by users. Unfortunately,
256  # the specCompliantUrl flag did not contemplate the redirect usage. This flag is
257  # specifically about the usage in a redirect().
258 
259  workerdExperimental @24 :Bool
260      $compatEnableFlag("experimental")
261      $experimental;
262  # Experimental, do not use.
263  # This is a catch-all compatibility flag for experimental development within workerd
264  # that is not covered by another more-specific compatibility flag. It is the intention
265  # of this flag to always have the $experimental attribute.
266  # This is intended to guard new features that do not introduce any backwards-compatibility
267  # concerns (e.g. they only add a new API), and therefore do not need a compat flag of their own
268  # in the long term, but where we still want to guard access to the feature while it is in
269  # development. Don't use this for backwards-incompatible changes; give them their own flag.
270  # WARNING: Any feature blocked by this flag is subject to change at any time, including
271  # removal. Do not ignore this warning.
272 
273  durableObjectGetExisting @25 :Bool
274      $compatEnableFlag("durable_object_get_existing")
275      $experimental;
276  # Experimental, allows getting a durable object stub that ensures the object already exists.
277  # This is currently a work in progress mechanism that is not yet available for use in workerd.
278 
279  httpHeadersGetSetCookie @26 :Bool
280      $compatEnableFlag("http_headers_getsetcookie")
281      $compatDisableFlag("no_http_headers_getsetcookie")
282      $compatEnableDate("2023-03-01");
283  # Enables the new headers.getSetCookie() API and the corresponding changes in behavior for
284  # the Header objects keys() and entries() iterators.
285 
286  dispatchExceptionTunneling @27 :Bool
287      $compatEnableDate("2023-03-01")
288      $compatEnableFlag("dynamic_dispatch_tunnel_exceptions")
289      $compatDisableFlag("dynamic_dispatch_treat_exceptions_as_500");
290  # Enables the tunneling of exceptions from a dynamic dispatch callee back into the caller.
291  # Previously any uncaught exception in the callee would be returned to the caller as an empty
292  # HTTP 500 response.
293 
294  serviceBindingExtraHandlers @28 :Bool
295      $compatEnableFlag("service_binding_extra_handlers")
296      $experimental;
297  # Allows service bindings to call additional event handler methods on the target Worker.
298  # Initially only includes support for calling the queue() handler.
299  # WARNING: this flag exposes the V8 deserialiser to users via `Fetcher#queue()` `serializedBody`.
300  # Historically, this has required a trusted environment to be safe. If we decide to make this
301  # flag non-experimental, we must ensure we take appropriate precuations.
302 
303  noCfBotManagementDefault @29 :Bool
304      $compatEnableFlag("no_cf_botmanagement_default")
305      $compatDisableFlag("cf_botmanagement_default")
306      $compatEnableDate("2023-08-01");
307  # This one operates a bit backwards. With the flag *enabled* no default cfBotManagement
308  # data will be included. The the flag *disable*, default cfBotManagement data will be
309  # included in the request.cf if the field is not present.
310 
311  urlSearchParamsDeleteHasValueArg @30 :Bool
312      $compatEnableFlag("urlsearchparams_delete_has_value_arg")
313      $compatDisableFlag("no_urlsearchparams_delete_has_value_arg")
314      $compatEnableDate("2023-07-01");
315  # When enabled, the delete() and has() methods of the standard URLSearchParams object
316  # (see url-standard.h) will have the recently added second value argument enabled.
317 
318  strictCompression @31 :Bool
319      $compatEnableFlag("strict_compression_checks")
320      $compatDisableFlag("no_strict_compression_checks")
321      $compatEnableDate("2023-08-01");
322  # Perform additional error checking in the Web Compression API and throw an error if a
323  # DecompressionStream has trailing data or gets closed before the full compressed data has been
324  # provided.
325 
326  brotliContentEncoding @32 :Bool
327      $compatEnableFlag("brotli_content_encoding")
328      $compatEnableDate("2024-04-29")
329      $compatDisableFlag("no_brotli_content_encoding")
330      $neededByFl;
331  # Enables compression/decompression support for the brotli compression algorithm.
332  # With the flag enabled workerd will support the "br" content encoding in the Request and
333  # Response APIs and compress or decompress data accordingly as with gzip.
334 
335  strictCrypto @33 :Bool
336      $compatEnableFlag("strict_crypto_checks")
337      $compatDisableFlag("no_strict_crypto_checks")
338      $compatEnableDate("2023-08-01");
339  # Perform additional error checking in the Web Crypto API to conform with the specification as
340  # well as reject key parameters that may be unsafe based on key length or public exponent.
341 
342  rttiApi @34 :Bool
343      $compatEnableFlag("rtti_api")
344      $experimental;
345  # Enables the `workerd:rtti` module for querying runtime-type-information from JavaScript.
346 
347  obsolete35 @35 :Bool
348      $compatEnableFlag("webgpu")
349      $experimental;
350  # The experimental webgpu API was removed.
351 
352  cryptoPreservePublicExponent @36 :Bool
353      $compatEnableFlag("crypto_preserve_public_exponent")
354      $compatDisableFlag("no_crypto_preserve_public_exponent")
355      $compatEnableDate("2023-12-01");
356  # In the WebCrypto API, the `publicExponent` field of the algorithm of RSA keys would previously
357  # be an ArrayBuffer. Using this flag, publicExponent is a Uint8Array as mandated by the
358  # specification.
359 
360  vectorizeQueryMetadataOptional @37 :Bool
361      $compatEnableFlag("vectorize_query_metadata_optional")
362      $compatEnableDate("2023-11-08")
363      $compatDisableFlag("vectorize_query_original");
364  # Vectorize query option change to allow returning of metadata to be optional. Accompanying this:
365  # a return format change to move away from a nested object with the VectorizeVector.
366 
367  unsafeModule @38 :Bool
368      $compatEnableFlag("unsafe_module")
369      $experimental;
370  # Enables the `workerd:unsafe` module for performing dangerous operations from JavaScript.
371  # Intended for local development and testing use cases. Currently just supports aborting all
372  # Durable Objects running in a `workerd` process.
373 
374  jsRpc @39 :Bool
375      $compatEnableFlag("js_rpc")
376      $experimental;
377  # Enables JS RPC on the server side for Durable Object classes that do not explicitly extend
378  # `DurableObjects`.
379  #
380  # This flag is obsolete but supported temporarily to avoid breaking people who used it. All code
381  # should switch to using `extends DurableObject` as the way to enable RPC.
382  #
383  # As of this writing, it is still necessary to enable the general `experimental` flag to use RPC
384  # on both the client and server sides.
385 
386  noImportScripts @40 :Bool
387      $compatEnableFlag("no_global_importscripts")
388      $compatDisableFlag("global_importscripts")
389      $compatEnableDate("2024-03-04");
390  # Removes the non-implemented importScripts() function from the global scope.
391 
392  nodeJsAls @41 :Bool
393      $compatEnableFlag("nodejs_als")
394      $compatDisableFlag("no_nodejs_als");
395  # Enables the availability of the Node.js AsyncLocalStorage API independently of the full
396  # node.js compatibility option.
397 
398  queuesJsonMessages @42 :Bool
399      $compatEnableFlag("queues_json_messages")
400      $compatDisableFlag("no_queues_json_messages")
401      $compatEnableDate("2024-03-18");
402  # Queues bindings serialize messages to JSON format by default (the previous default was v8 format)
403 
404  pythonWorkers @43 :Bool
405      $compatEnableFlag("python_workers")
406      $pythonSnapshotRelease
407      $impliedByAfterDate(name = "pythonWorkersDevPyodide", date = "2000-01-01");
408  # Enables Python Workers. Access to this flag is not restricted, instead bundles containing
409  # Python modules are restricted in EWC.
410  #
411  # WARNING: Python Workers are still an experimental feature and thus subject to change.
412 
413  fetcherNoGetPutDelete @44 :Bool
414      $compatEnableFlag("fetcher_no_get_put_delete")
415      $compatDisableFlag("fetcher_has_get_put_delete")
416      $compatEnableDate("2024-03-26");
417  # Historically, the `Fetcher` type -- which is the type of Service Bindings, and also the parent
418  # type of Durable Object stubs -- had special methods `get()`, `put()`, and `delete()`, which
419  # were shortcuts for calling `fetch()` with the corresponding HTTP method. These methods were
420  # never documented.
421  #
422  # To make room for people to define their own RPC methods with these names, this compat flag
423  # makes them no longer defined.
424 
425  unwrapCustomThenables @45 :Bool
426      $compatEnableFlag("unwrap_custom_thenables")
427      $compatDisableFlag("no_unwrap_custom_thenables")
428      $compatEnableDate("2024-04-01");
429 
430  fetcherRpc @46 :Bool
431      $compatEnableFlag("rpc")
432      $compatDisableFlag("no_rpc")
433      $compatEnableDate("2024-04-03");
434  # Whether the type `Fetcher` type -- which is the type of Service Bindings, and also the parent
435  # type of Durable Object stubs -- support RPC. If so, this type will have a wildcard method, so
436  # it will appear that all possible property names are present on any fetcher instance. This could
437  # break code that tries to infer types based on the presence or absence of methods.
438 
439  internalStreamByobReturn @47 :Bool
440      $compatEnableFlag("internal_stream_byob_return_view")
441      $compatDisableFlag("internal_stream_byob_return_undefined")
442      $compatEnableDate("2024-05-13");
443  # Sadly, the original implementation of ReadableStream (now called "internal" streams), did not
444  # properly implement the result of ReadableStreamBYOBReader's read method. When done = true,
445  # per the spec, the result `value` must be an empty ArrayBufferView whose underlying ArrayBuffer
446  # is the same as the one passed to the read method. Our original implementation returned
447  # undefined instead. This flag changes the behavior to match the spec and to match the behavior
448  # implemented by the JS-backed ReadableStream implementation.
449 
450  blobStandardMimeType @48 :Bool
451      $compatEnableFlag("blob_standard_mime_type")
452      $compatDisableFlag("blob_legacy_mime_type")
453      $compatEnableDate("2024-06-03");
454  # The original implementation of the Blob mime type normalization when extracting a blob
455  # from the Request or Response body is not compliant with the standard. Unfortunately,
456  # making it compliant is a breaking change. This flag controls the availability of the
457  # new spec-compliant Blob mime type normalization.
458 
459  fetchStandardUrl @49 :Bool
460    $compatEnableFlag("fetch_standard_url")
461    $compatDisableFlag("fetch_legacy_url")
462    $compatEnableDate("2024-06-03");
463  # Ensures that WHATWG standard URL parsing is used in the fetch API implementation.
464 
465  nodeJsCompatV2 @50 :Bool
466      $compatEnableFlag("nodejs_compat_v2")
467      $compatDisableFlag("no_nodejs_compat_v2")
468      $impliedByAfterDate(name = "nodeJsCompat", date = "2024-09-23");
469  # Implies nodeJSCompat with the following additional modifications:
470  # * Node.js Compat built-ins may be imported/required with or without the node: prefix
471  # * Node.js Compat the globals Buffer and process are available everywhere
472 
473  globalFetchStrictlyPublic @51 :Bool
474      $compatEnableFlag("global_fetch_strictly_public")
475      $compatDisableFlag("global_fetch_private_origin");
476  # Controls what happens when a Worker hosted on Cloudflare uses the global `fetch()` function to
477  # request a hostname that is within the Worker's own Cloudflare zone (domain).
478  #
479  # Historically, such requests would be routed to the zone's origin server, ignoring any Workers
480  # mapped to the URL and also bypassing Cloudflare security settings. This behavior made sense
481  # when Workers was first introduced as a way to rewrite requests before passing them along to
482  # the origin, and bindings didn't exist: the only way to forward the request to origin was to
483  # use global fetch(), and if it didn't bypass Workers, you'd end up looping back to the same
484  # Worker.
485  #
486  # However, this behavior has a problem: it opens the door for SSRF attacks. Imagine a Worker is
487  # designed to fetch a resource from a user-provided URL. An attacker could provide a URL that
488  # points back to the Worker's own zone, and possibly cause the Worker to fetch a resource from
489  # origin that isn't meant to be reachable by the public.
490  #
491  # Traditionally, this kind of attack is considered a bug in the application: an application that
492  # fetches untrusted URLs must verify that the URL doesn't refer to a private resource that only
493  # the application itself is meant to access. However, applications can easily get this wrong.
494  # Meanwhile, by using bindings, we can make this class of problem go away.
495  #
496  # When global_fetch_strictly_public is enabled, the global `fetch()` function (when invoked on
497  # Cloudflare Workers) will strictly route requests as if they were made on the public internet.
498  # Thus, requests to a Worker's own zone will loop back to the "front door" of Cloudflare and
499  # will be treated like a request from the internet, possibly even looping back to the same Worker
500  # again. If an application wishes to send requests to its origin, it must configure an "origin
501  # binding". An origin binding behaves like a service binding (it has a `fetch()` method) but
502  # sends requests to the zone's origin servers, bypassing Cloudflare. E.g. the Worker would write
503  # `env.ORIGIN.fetch(req)` to send a request to its origin.
504  #
505  # Note: This flag only impacts behavior on Cloudflare. It has no effect when using workerd.
506  # Under workerd, the config file can control where global `fetch()` goes by configuring the
507  # worker's `globalOutbound` implicit binding. By default, under workerd, global `fetch()` has
508  # always been configured to accept publicly-routable internet hosts only; hostnames which map
509  # to private IP addresses (as defined in e.g. RFC 1918) will be rejected. Thus, workerd has
510  # always been SSRF-safe by default.
511 
512  newModuleRegistry @52 :Bool
513      $compatEnableFlag("new_module_registry")
514      $compatDisableFlag("legacy_module_registry")
515      $experimental;
516  # Enables of the new module registry implementation.
517 
518  cacheOptionEnabled @53 :Bool
519    $compatEnableFlag("cache_option_enabled")
520    $compatDisableFlag("cache_option_disabled")
521    $compatEnableDate("2024-11-11");
522  # Enables the use of no-store headers from requests
523 
524  kvDirectBinding @54 :Bool
525      $compatEnableFlag("kv_direct_binding")
526      $experimental;
527  # Enables bypassing FL by translating pipeline tunnel configuration to subpipeline.
528  # This flag is used only by the internal repo and not directly by workerd.
529 
530  allowCustomPorts @55 :Bool
531      $compatEnableFlag("allow_custom_ports")
532      $compatDisableFlag("ignore_custom_ports")
533      $compatEnableDate("2024-09-02")
534      $neededByFl;
535  # Enables fetching hosts with a custom port from workers.
536  # For orange clouded sites only standard ports are allowed (https://developers.cloudflare.com/fundamentals/reference/network-ports/#network-ports-compatible-with-cloudflares-proxy).
537  # For grey clouded sites all ports are allowed.
538 
539  increaseWebsocketMessageSize @56 :Bool
540      $compatEnableFlag("increase_websocket_message_size")
541      $experimental;
542  # For local development purposes only, increase the message size limit to 128MB.
543  # This is not expected ever to be made available in production, as large messages are inefficient.
544 
545  internalWritableStreamAbortClearsQueue @57 :Bool
546      $compatEnableFlag("internal_writable_stream_abort_clears_queue")
547      $compatDisableFlag("internal_writable_stream_abort_does_not_clear_queue")
548      $compatEnableDate("2024-09-02");
549  # When using the original WritableStream implementation ("internal" streams), the
550  # abort() operation would be handled lazily, meaning that the queue of pending writes
551  # would not be cleared until the next time the queue was processed. This behavior leads
552  # to a situtation where the stream can hang if the consumer stops consuming. When set,
553  # this flag changes the behavior to clear the queue immediately upon abort.
554 
555  pythonWorkersDevPyodide @58 :Bool
556    $compatEnableFlag("python_workers_development")
557    $pythonSnapshotRelease
558    $experimental;
559  # Enables Python Workers and uses the bundle from the Pyodide source directory directly. For testing only.
560  #
561  # Note that the baseline snapshot hash here refers to the one used in
562  # `baseline-from-gcs.ew-test-bin.c++`. We don't intend to ever load it in production.
563 
564  nodeJsZlib @59 :Bool
565      $compatEnableFlag("nodejs_zlib")
566      $compatDisableFlag("no_nodejs_zlib")
567      $impliedByAfterDate(names = ["nodeJsCompat", "nodeJsCompatV2"], date = "2024-09-23");
568  # Enables node:zlib implementation while it is in-development.
569  # Once the node:zlib implementation is complete, this will be automatically enabled when
570  # nodejs_compat or nodejs_compat_v2 are enabled.
571 
572  replicaRouting @60 :Bool
573      $compatEnableFlag("replica_routing")
574      $experimental;
575  # Enables routing to a replica on the client-side.
576  # Doesn't mean requests *will* be routed to a replica, only that they can be.
577 
578  obsolete61 @61 :Bool
579      $compatEnableFlag("enable_d1_with_sessions_api")
580      $experimental;
581  # Was used to enable the withSession(bookmarkOrConstraint) method that allows users
582  # to use read-replication Sessions API for D1. This is now enabled for everyone.
583 
584  handleCrossRequestPromiseResolution @62 :Bool
585      $compatEnableFlag("handle_cross_request_promise_resolution")
586      $compatDisableFlag("no_handle_cross_request_promise_resolution")
587      $compatEnableDate("2024-10-14");
588  # Historically, it has been possible to resolve a promise from an incorrect request
589  # IoContext. This leads to issues with promise continuations being scheduled to run
590  # in the wrong IoContext leading to errors and difficult to diagnose bugs. With this
591  # compatibility flag we arrange to have such promise continuations scheduled to run
592  # in the correct IoContext if it is still alive, or dropped on the floor with a warning
593  # if the correct IoContext is not still alive.
594  obsolete63 @63 :Bool
595      $experimental;
596 
597  setToStringTag @64 :Bool
598      $compatEnableFlag("set_tostring_tag")
599      $compatDisableFlag("do_not_set_tostring_tag")
600      $compatEnableDate("2024-09-26");
601  # A change was made that set the Symbol.toStringTag on all jsg::Objects in order to
602  # fix several spec compliance bugs. Unfortunately it turns out that was more breaking
603  # than expected. This flag restores the original behavior for compat dates before
604  # 2024-09-26
605 
606  upperCaseAllHttpMethods @65 :Bool
607      $compatEnableFlag("upper_case_all_http_methods")
608      $compatDisableFlag("no_upper_case_all_http_methods")
609      $compatEnableDate("2024-10-14");
610  # HTTP methods are expected to be upper-cased. Per the fetch spec, if the methods
611  # is specified as `get`, `post`, `put`, `delete`, `head`, or `options`, implementations
612  # are expected to uppercase the method. All other method names would generally be
613  # expected to throw as unrecognized (e.g. `patch` would be an error while `PATCH` is
614  # accepted). This is a bit restrictive, even if it is in the spec. This flag modifies
615  # the behavior to uppercase all methods prior to parsing to that the method is always
616  # recognized if it is a known method.
617 
618  obsolete66 @66 :Bool
619      $compatEnableFlag("python_external_packages");
620 
621  noTopLevelAwaitInRequire @67 :Bool
622      $compatEnableFlag("disable_top_level_await_in_require")
623      $compatDisableFlag("enable_top_level_await_in_require")
624      $compatEnableDate("2024-12-02");
625  # When enabled, use of top-level await syntax in require() calls will be disallowed.
626  # The ecosystem and runtimes are moving to a state where top level await in modules
627  # is being strongly discouraged.
628 
629  fixupTransformStreamBackpressure @68 :Bool
630      $compatEnableFlag("fixup-transform-stream-backpressure")
631      $compatDisableFlag("original-transform-stream-backpressure")
632      $compatEnableDate("2024-12-16");
633  # A bug in the original implementation of TransformStream failed to apply backpressure
634  # correctly. The fix, however, can break existing implementations that don't account
635  # for the bug so we need to put the fix behind a compat flag.
636 
637  obsolete69 @69 :Bool
638      $compatEnableFlag("tail_worker_user_spans")
639      $experimental;
640 
641  cacheNoCache @70 :Bool
642      $compatEnableFlag("cache_no_cache_enabled")
643      $compatDisableFlag("cache_no_cache_disabled")
644      $impliedByAfterDate(name = "cacheOptionEnabled", date = "2025-08-07");
645  # Enables the use of cache: no-cache in the fetch api.
646 
647  pythonWorkers20250116 @71 :Bool
648      $compatEnableFlag("python_workers_20250116")
649      $compatDisableFlag("no_python_workers_20250116")
650      $impliedByAfterDate(name = "pythonWorkers", date = "2025-09-29")
651      $pythonSnapshotRelease;
652 
653  requestCfOverridesCacheRules @72 :Bool
654      $compatEnableFlag("request_cf_overrides_cache_rules")
655      $compatDisableFlag("no_request_cf_overrides_cache_rules")
656      $compatEnableDate("2025-04-02")
657      $neededByFl;
658  # Enables cache settings specified request in fetch api cf object to override cache rules. (only for user owned or grey-clouded sites)
659 
660  memoryCacheDelete @73 :Bool
661      $compatEnableFlag("memory_cache_delete")
662      $experimental;
663  # Enables delete operations on memory cache if enabled.
664 
665  obsolete74 @74: Bool
666      $compatEnableFlag("unique_ctx_per_invocation")
667      $compatEnableDate("2025-03-10");
668  # Creates a unique ExportedHandler for each call to `export default` thus allowing a unique ctx
669  # per invocation.
670  #
671  # OBSOLETE: We decided to apply this change even to old workers as we've found some old workers
672  #   that assumed this behavior all along, and so this change actually fixes bugs for them.
673  #   It seems unlikely to break anyone because there's no way a Worker could depend on any two
674  #   requests hitting the same isolate, so how could they depend on any two requests having the
675  #   same `ctx` object? At worst they might store some sort of cache on it which becomes
676  #   ineffective, but their Worker would still work, and anyway this would be a very weird thing
677  #   for someone to do.
678 
679  reuseCtxAcrossNonclassEvents @92: Bool
680      $compatEnableFlag("nonclass_entrypoint_reuses_ctx_across_invocations");
681  # Just in case someone somewhere somehow actually relied on every event receiving the same `ctx`
682  # object, this restores the original behavior. We do not recommend this.
683 
684  queueConsumerNoWaitForWaitUntil @75 :Bool
685      $compatEnableFlag("queue_consumer_no_wait_for_wait_until")
686      $compatDisableFlag("queue_consumer_wait_for_wait_until");
687  # If enabled, does not require all waitUntil'ed promises to resolve successfully before reporting
688  # succeeded/failed messages/batches back from a queue consumer to the Queues service. This
689  # prevents a slow waitUntil'ed promise from slowing down consumption of messages from a queue,
690  # which has been a recurring problem for the prior behavior (which did wait for all waitUntil'ed
691  # tasks to complete.
692  # This intentionally doesn't have a compatEnableDate yet until so we can let some users opt-in to
693  # try it before enabling it for all new scripts, but will eventually need one.
694 
695  populateProcessEnv @76 :Bool
696      $compatEnableFlag("nodejs_compat_populate_process_env")
697      $compatDisableFlag("nodejs_compat_do_not_populate_process_env")
698      $impliedByAfterDate(name = "nodeJsCompat", date = "2025-04-01");
699  # Automatically populate process.env from text bindings only
700  # when nodejs_compat is being used.
701 
702  cacheApiRequestCfOverridesCacheRules @77 :Bool
703      $compatEnableFlag("cache_api_request_cf_overrides_cache_rules")
704      $compatDisableFlag("no_cache_api_request_cf_overrides_cache_rules")
705      $compatEnableDate("2025-05-19")
706      $neededByFl;
707  # Enables cache settings specified request in cache api cf object to override cache rules. (only for user owned or grey-clouded sites)
708 
709  disableImportableEnv @78 :Bool
710      $compatEnableFlag("disallow_importable_env")
711      $compatDisableFlag("allow_importable_env");
712  # When allowed, `import { env, exports } from 'cloudflare:workers'` will provide access
713  # to the per-request environment/bindings. This flag also disables importable exports
714  # (the exports proxy) since both features are conceptually related.
715 
716  assetsSecFetchModeNavigateHeaderPrefersAssetServing @79 :Bool
717      $compatEnableFlag("assets_navigation_prefers_asset_serving")
718      $compatDisableFlag("assets_navigation_has_no_effect")
719      $compatEnableDate("2025-04-01");
720  # Enables routing to asset-worker over a user worker when an appropriate
721  # `assets.not_found_handling` configuration option is set and `Sec-Fetch-Mode: navigate` header
722  # is present. This flag is used only by @cloudflare/workers-shared (within workers-sdk) and not
723  #  directly by workerd.
724 
725  cacheApiCompatFlags @80 :Bool
726      $compatEnableFlag("cache_api_compat_flags")
727      $compatDisableFlag("no_cache_api_compat_flags")
728      $compatEnableDate("2025-04-19");
729  # when enabled, exports compability flags for FL to Cache API requests.
730 
731  obsolete81 @81 :Bool
732      $compatEnableFlag("python_workers_durable_objects")
733      $experimental;
734  # when enabled, enables Durable Object support for Python Workers.
735 
736  obsolete82 @82 :Bool
737      $compatEnableFlag("streaming_tail_worker")
738      $experimental;
739  # Obsolete flag. Has no effect.
740 
741  specCompliantUrlpattern @83 :Bool
742    $compatEnableFlag("urlpattern_standard")
743    $compatEnableDate("2025-05-01")
744    $compatDisableFlag("urlpattern_original");
745  # The original URLPattern implementation is not compliant with the
746  # WHATWG URLPattern Standard, leading to a number of issues reported by users. Unfortunately,
747  # making it spec compliant is a breaking change. This flag controls the availability
748  # of the new spec-compliant URLPattern implementation.
749 
750  jsWeakRef @84 :Bool
751      $compatEnableFlag("enable_weak_ref")
752      $compatEnableDate("2025-05-05")
753      $compatDisableFlag("disable_weak_ref");
754  # Enables WeakRefs and FinalizationRegistry API.
755  # WebAssembly based projects often rely on this API for wasm memory cleanup
756 
757  requestSignalPassthrough @85 :Bool
758      $compatEnableFlag("request_signal_passthrough")
759      $compatDisableFlag("no_request_signal_passthrough");
760  # When enabled, the AbortSignal of the incoming request is not passed through to subrequests.
761  # As a result, outgoing subrequests will not be cancelled when the incoming request is.
762 
763  enableNavigatorLanguage @86 :Bool
764      $compatEnableFlag("enable_navigator_language")
765      $compatEnableDate("2025-05-19")
766      $compatDisableFlag("disable_navigator_language");
767  # Enables Navigator.language API.
768 
769  webFileSystem @87 :Bool
770      $compatEnableFlag("enable_web_file_system")
771      $experimental;
772  # Enables the experimental Web File System API.
773  # WARNING: This API is still in development and may change or be removed in the future.
774 
775  abortSignalRpc @88 :Bool
776      $compatEnableFlag("enable_abortsignal_rpc")
777      $experimental;
778  # Enables experimental support for passing AbortSignal over RPC.
779 
780  allowEvalDuringStartup @89 :Bool
781      $compatEnableFlag("allow_eval_during_startup")
782      $compatEnableDate("2025-06-01")
783      $compatDisableFlag("disallow_eval_during_startup");
784  # Enables eval() and new Function() during startup.
785 
786  enableRequestSignal @90 :Bool
787    $compatEnableFlag("enable_request_signal")
788    $compatDisableFlag("disable_request_signal");
789  # Enables Request.signal for incoming requests.
790  # This feature is still experimental and the compat flag has no default enable date.
791 
792  connectPassThrough @91 :Bool
793    $compatEnableFlag("connect_pass_through")
794    $experimental;
795  # Causes the Worker to handle incoming connect events by simply passing them through to the
796  # Worker's globalOutbound (typically, the internet).
797  #
798  # As of this writing, Workers cannot yet receive raw socket connections, because no API has been
799  # defined for doing so. But a Worker can be configured to be the `globalOutbound` for another
800  # Worker, causing the first Worker to intercept all outbound network requests that the second
801  # Worker makes by calling `fetch()` or `connect()`. Since there's no way for the first Worker
802  # to actually handle the `connect()` requests, this implies the second Worker cannot make any
803  # raw TCP connections in this configuration. This is intended: often, the first Worker
804  # implements some sort of security rules governing what kinds of requests the second Worker can
805  # send to the internet, and if `connect()` requests were allowed to go directly to the internet,
806  # that could be used to bypass said security checks.
807  #
808  # However, sometimes outbound workers are used for reasons other than security, and in fact the
809  # outbound Worker does not really care to block `connect()` requests. Until such a time as we
810  # create an actual API for proxying connections, such outbound workers can set this compat flag
811  # to opt into allowing connect requests to pass through.
812 
813  # NOTE: `reuseCtxAcrossNonclassEvents @92` was declared earlier in the file. Next ordinal is
814  #   @93.
815 
816  bindAsyncLocalStorageSnapshot @93 :Bool
817      $compatEnableFlag("bind_asynclocalstorage_snapshot_to_request")
818      $compatDisableFlag("do_not_bind_asynclocalstorage_snapshot_to-request")
819      $compatEnableDate("2025-06-16");
820  # The AsyncLocalStorage frame can capture values that are bound to the
821  # current IoContext. This is not always in the users control since we use
822  # the ALS storage frame to propagate internal trace spans as well as
823  # user-provided values. This flag, when set, binds the snapshot / bound
824  # functions to the current IoContext and will throw an error if the bound
825  # functions are called outside of the IoContext in which they were created.
826 
827  throwOnUnrecognizedImportAssertion @94 :Bool
828      $compatEnableFlag("throw_on_unrecognized_import_assertion")
829      $compatDisableFlag("ignore_unrecognized_import_assertion")
830      $compatEnableDate("2025-06-16");
831  # In the original module registry implementation, import attributes that are not recognized
832  # would be ignored. This is not compliant with the spec which strongly recommends that runtimes
833  # throw an error when unknown import attributes are encountered. In the new module registry
834  # implementation the recommended behavior is what is implemented. With this compat flag
835  # enabled, the original module registry implementation will follow the recommended behavior.
836 
837  pythonWorkflows @95 :Bool
838    $compatEnableFlag("python_workflows")
839    $compatDisableFlag("disable_python_workflows")
840    $impliedByAfterDate(name = "pythonWorkers", date = "2025-09-20");
841  # Enables support for Python workflows.
842  # This is still in development and may change in the future.
843 
844  unsupportedProcessActualPlatform @96 :Bool
845      $compatEnableFlag("unsupported_process_actual_platform")
846      $experimental;
847  # By default, Workerd will always expose "linux" as the process.platform.
848  # This flag enables support for process.platform to expose the actual system platform.
849  # This is unsupported, as this feature will never ever be supported as non-experimental and is a
850  # temporary WPT test path only.
851 
852  enableNodeJsProcessV2 @97 :Bool
853      $compatEnableFlag("enable_nodejs_process_v2")
854      $compatDisableFlag("disable_nodejs_process_v2")
855      $impliedByAfterDate(name = "nodeJsCompat", date="2025-09-15");
856  # Switches from the partial process implementation with only "nextTick", "env", "exit",
857  # "getBuiltinModule", "platform" and "features" property implementations, to the full-featured
858  # Node.js-compatibile process implementation with all process properties either stubbed or
859  # implemented. It is required to use this flag with nodejs_compat (or nodejs_compat_v2).
860 
861  setEventTargetThis @98 :Bool
862      $compatEnableFlag("set_event_target_this")
863      $compatDisableFlag("no_set_event_target_this")
864      $compatEnableDate("2025-08-01");
865  # The original implementation of EventTarget was not correctly setting the `this` value
866  # for event handlers. This flag enables the correct behavior, which is compliant with the spec.
867 
868  enableForwardableEmailFullHeaders @99 :Bool
869      $compatEnableFlag("set_forwardable_email_full_headers")
870      $compatDisableFlag("set_forwardable_email_single_headers")
871      $compatEnableDate("2025-08-01");
872  # The original version of the headers sent to edgeworker were truncated to a single
873  # value for specific header names, such as To and Cc. With this compat flag we will send
874  # the full header values to the worker script.
875 
876  enableNodejsHttpModules @100 :Bool
877      $compatEnableFlag("enable_nodejs_http_modules")
878      $compatDisableFlag("disable_nodejs_http_modules")
879      $impliedByAfterDate(name = "nodeJsCompat", date = "2025-08-15");
880  # Enables Node.js http related modules such as node:http and node:https
881 
882  pedanticWpt @101 :Bool
883      $compatEnableFlag("pedantic_wpt")
884      $compatDisableFlag("non_pedantic_wpt");
885  # Enables a "pedantic mode" for WPT compliance. Multiple changes are grouped under
886  # this flag that are known to be required to pass more web platform tests but which
887  # otherwise are likely not to be strictly necessary for most users.
888 
889  exposeGlobalMessageChannel @102 :Bool
890      $compatEnableFlag("expose_global_message_channel")
891      $compatDisableFlag("no_expose_global_message_channel")
892      $compatEnableDate("2025-08-15");
893  # Enables exposure of the MessagePort and MessageChannel classes on the global scope.
894 
895  enableNodejsHttpServerModules @103 :Bool
896      $compatEnableFlag("enable_nodejs_http_server_modules")
897      $compatDisableFlag("disable_nodejs_http_server_modules")
898      $impliedByAfterDate(name = "enableNodejsHttpModules", date = "2025-09-01");
899  # Enables Node.js http server related modules such as node:_http_server
900  # It is required to use this flag with `enable_nodejs_http_modules` since
901  # it enables the usage of http related node.js modules, and this flag enables
902  # the methods exposed by the node.js http modules.
903  # Regarding the recommendation for using import { env, waitUntil } from 'cloudflare:workers';
904  # `disallow_importable_env` compat flag should not be set if you are using this
905  # and need access to the env since that will prevent access.
906 
907  pythonNoGlobalHandlers @104 :Bool
908      $compatEnableFlag("python_no_global_handlers")
909      $compatDisableFlag("disable_python_no_global_handlers")
910      $compatEnableDate("2025-08-14");
911  # Disables the global handlers for Python workers and enforces their use via default entrypoint
912  # classes.
913 
914  enableNodeJsFsModule @105 :Bool
915    $compatEnableFlag("enable_nodejs_fs_module")
916    $compatDisableFlag("disable_nodejs_fs_module")
917    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-09-15");
918  # Enables the Node.js fs module. It is required to use this flag with
919  # nodejs_compat (or nodejs_compat_v2).
920 
921  enableNodeJsOsModule @106 :Bool
922    $compatEnableFlag("enable_nodejs_os_module")
923    $compatDisableFlag("disable_nodejs_os_module")
924    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-09-15");
925  # Enables the Node.js os module. It is required to use this flag with
926  # nodejs_compat (or nodejs_compat_v2).
927 
928  pythonWorkersForceNewVendorPath @107 :Bool
929      $compatEnableFlag("python_workers_force_new_vendor_path")
930      $compatEnableDate("2025-08-11");
931  # Disables adding `/session/metadata/vendor` to the Python Worker's sys.path. So Workers using
932  # this flag will have to place their vendored modules in a `python_modules` directory.
933 
934  removeNodejsCompatEOL @108 :Bool
935    $compatEnableFlag("remove_nodejs_compat_eol")
936    $compatDisableFlag("add_nodejs_compat_eol")
937    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-09-01");
938  # Removes the Node.js compatibility layer for EOL versions of Node.js.
939  # When the flag is enabled, APIs that have reached End-of-Life in Node.js
940  # will be removed for workers. When disabled, the APIs are present (but
941  # might still be non-functional stubs)
942  # This flag is intended to be a roll-up flag. That is, as additional APIs
943  # reach EOL, new compat flags will be added for those that will have
944  # `impliedByAfterDate(name = "removeNodeJsCompatEOL", ...` annotations.
945 
946  enableWorkflowScriptValidation @109 :Bool
947      $compatEnableFlag("enable_validate_workflow_entrypoint")
948      $compatDisableFlag("disable_validate_workflow_entrypoint")
949      $compatEnableDate("2025-09-20");
950  # This flag enables additional checks in the control plane to validate that workflows are
951  # defined and used correctly
952 
953  pythonDedicatedSnapshot @110 :Bool
954      $compatEnableFlag("python_dedicated_snapshot")
955      $compatDisableFlag("disable_python_dedicated_snapshot")
956      $impliedByAfterDate(name = "pythonWorkers20250116", date = "2025-10-16");
957  # Enables the generation of dedicated snapshots on Python Worker upload. The snapshot will be
958  # stored inside the resulting WorkerBundle of the Worker. The snapshot will be taken after the
959  # top-level execution of the Worker.
960 
961  typescriptStripTypes @111 :Bool
962    $compatEnableFlag("typescript_strip_types")
963    $experimental;
964  # Strips all Typescript types from loaded files.
965  # If loaded files contain unsupported typescript construct beyond type annotations (e.g. enums),
966  # or is not a syntactically valid Typescript, the worker will fail to load.
967 
968  enableNodeJsHttp2Module @112 :Bool
969    $compatEnableFlag("enable_nodejs_http2_module")
970    $compatDisableFlag("disable_nodejs_http2_module")
971    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-09-01");
972  # Enables the Node.js http2 module stubs.
973 
974  experimentalAllowEvalAlways @113 :Bool
975      $compatEnableFlag("allow_insecure_inefficient_logged_eval")
976      $experimental;
977  # Enables eval() and new Function() always, even during request handling.
978  # ***This flag should *never* be enabled by default.***
979  # The name of the enable flag is intentionally long and scary-sounding to
980  # discourage casual use.
981  #  * "insecure" because code-gen during request handling can lead to security issues.
982  #  * "inefficient" because repeated code-gen during request handling can be slow.
983  #  * "logged" because each use would likely be logged in production for security
984  #    auditing so users should avoid including PII and other sensitive data in dynamically
985  #    generated and evaluated code.
986  # This flag is experimental and may be removed in the future. It is added for
987  # testing purposes.
988 
989  stripAuthorizationOnCrossOriginRedirect @114 :Bool
990      $compatEnableFlag("strip_authorization_on_cross_origin_redirect")
991      $compatDisableFlag("retain_authorization_on_cross_origin_redirect")
992      $compatEnableDate("2025-09-01");
993  # This flag specifies that when automatic redirects are enabled, and a redirect points to a URL
994  # at a different origin, if the original request contained an Authorization header, that header
995  # is removed before following the redirect. This behavior is required by the current version of
996  # the Fetch API specification.
997  #
998  # This requirement was added to the Fetch spec in 2022, well after Cloudflare Workers
999  # originally implemented it. Hence, Workers did not originally implement this requirement. This
1000  # requirement is backwards-incompatible, and so the new behavior is guarded by a compatibility
1001  # flag.
1002  #
1003  # Note that the old behavior was not inherently insecure, and indeed could be desirable in many
1004  # circumstances. For example, if an API that requires authorization wishes to change its
1005  # hostname, it might wish to redirect to the new hostname while having the client send along
1006  # their credentials. Under the new fetch behavior, such a redirect will break clients, and this
1007  # has legitimately broken real use cases. However, it's true that the old behavior could be a
1008  # "gotcha" leading to security problems when combined with other mistakes. Hence, the spec was
1009  # changed, and Workers must follow the spec.
1010 
1011  enhancedErrorSerialization @115 :Bool
1012      $compatEnableFlag("enhanced_error_serialization")
1013      $compatDisableFlag("legacy_error_serialization")
1014      $compatEnableDate("2026-04-21");
1015  # Enables enhanced error serialization for errors serialized using structuredClone /
1016  # v8 serialization. More error types are supported, and own properties are included.
1017  # Note that when enabled, deserialization of the errors will not preserve the original
1018  # stack by default.
1019 
1020  emailSendingQueuing @116 :Bool
1021      $compatEnableFlag("enable_email_sending_queuing")
1022      $compatDisableFlag("disable_email_sending_queuing");
1023  # Enables Queuing on the `.send(message: EmailMessage)` function on send_email binding if there's
1024  # a temporary error on email delivery.
1025  # Note that by enabling this, user-provided Message-IDs are stripped and
1026  # Email Workers will generate and use its own.
1027 
1028  removeNodejsCompatEOLv22 @117 :Bool
1029      $compatEnableFlag("remove_nodejs_compat_eol_v22")
1030      $compatDisableFlag("add_nodejs_compat_eol_v22")
1031      $impliedByAfterDate(name = "removeNodejsCompatEOL", date = "2027-04-30");
1032  # Removes APIs that reached end-of-life in Node.js 22.x. When using the
1033  # removeNodejsCompatEOL flag, this will default enable on/after 2027-04-30.
1034 
1035  removeNodejsCompatEOLv23 @118 :Bool
1036      $compatEnableFlag("remove_nodejs_compat_eol_v23")
1037      $compatDisableFlag("add_nodejs_compat_eol_v23")
1038      $impliedByAfterDate(name = "removeNodejsCompatEOLv24", date = "2025-09-01");
1039  # Removes APIs that reached end-of-life in Node.js 23.x. This will default
1040  # enable when the removeNodejsCompatEOLv24 flag is enabled after 2025-09-01.
1041  # Went EOL on 2025-06-01
1042 
1043  removeNodejsCompatEOLv24 @119 :Bool
1044      $compatEnableFlag("remove_nodejs_compat_eol_v24")
1045      $compatDisableFlag("add_nodejs_compat_eol_v24")
1046      $impliedByAfterDate(name = "removeNodejsCompatEOL", date = "2028-04-30");
1047  # Removes APIs that reached end-of-life in Node.js 24.x. When using the
1048	# removeNodejsCompatEOL flag, this will default enable on/after 2028-04-30.
1049 
1050  enableNodeJsConsoleModule @120 :Bool
1051    $compatEnableFlag("enable_nodejs_console_module")
1052    $compatDisableFlag("disable_nodejs_console_module")
1053    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-09-21");
1054  # Enables the Node.js console module. It is required to use this flag with
1055  # nodejs_compat (or nodejs_compat_v2).
1056 
1057  enableNodeJsVmModule @121 :Bool
1058    $compatEnableFlag("enable_nodejs_vm_module")
1059    $compatDisableFlag("disable_nodejs_vm_module")
1060    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-10-01");
1061  # Enables the Node.js non-functional stub vm module. It is required to use this flag with
1062  # nodejs_compat (or nodejs_compat_v2).
1063 
1064  enableNodeJsPerfHooksModule @122 :Bool
1065     $compatEnableFlag("enable_nodejs_perf_hooks_module")
1066     $compatDisableFlag("disable_nodejs_perf_hooks_module")
1067     $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1068   # Enables the Node.js perf_hooks module. It is required to use this flag with
1069   # nodejs_compat (or nodejs_compat_v2). This flag also implicitly enables the
1070   # global Performance classes (PerformanceEntry, PerformanceMark, etc.).
1071 
1072  enableGlobalPerformanceClasses @123 :Bool
1073     $compatEnableFlag("enable_global_performance_classes")
1074     $compatDisableFlag("disable_global_performance_classes")
1075     $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1076   # Enables PerformanceEntry, PerformanceMark, PerformanceMeasure, PerformanceResourceTiming,
1077   # PerformanceObserver and PerformanceObserverEntryList global classes.
1078   # These are also implicitly enabled by enableNodeJsPerfHooksModule.
1079 
1080  enableNodeJsDomainModule @124 :Bool
1081    $compatEnableFlag("enable_nodejs_domain_module")
1082    $compatDisableFlag("disable_nodejs_domain_module")
1083    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-12-04");
1084  # Enables the Node.js non-functional stub domain module. It is required to use this flag with
1085  # nodejs_compat (or nodejs_compat_v2).
1086 
1087  enableNodeJsV8Module @125 :Bool
1088    $compatEnableFlag("enable_nodejs_v8_module")
1089    $compatDisableFlag("disable_nodejs_v8_module")
1090    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1091  # Enables the Node.js non-functional stub v8 module. It is required to use this flag with
1092  # nodejs_compat (or nodejs_compat_v2).
1093 
1094  enableNodeJsTtyModule @126 :Bool
1095    $compatEnableFlag("enable_nodejs_tty_module")
1096    $compatDisableFlag("disable_nodejs_tty_module")
1097    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1098  # Enables the Node.js non-functional stub tty module. It is required to use this flag with
1099  # nodejs_compat (or nodejs_compat_v2).
1100 
1101  enableNodeJsPunycodeModule @127 :Bool
1102    $compatEnableFlag("enable_nodejs_punycode_module")
1103    $compatDisableFlag("disable_nodejs_punycode_module")
1104    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-12-04");
1105  # Enables the Node.js deprecated punycode module. It is required to use this flag with
1106  # nodejs_compat (or nodejs_compat_v2).
1107 
1108  enableNodeJsClusterModule @128 :Bool
1109    $compatEnableFlag("enable_nodejs_cluster_module")
1110    $compatDisableFlag("disable_nodejs_cluster_module")
1111    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-12-04");
1112  # Enables the Node.js non-functional stub cluster module. It is required to use this flag with
1113  # nodejs_compat (or nodejs_compat_v2).
1114 
1115  enableNodeJsChildProcessModule @129 :Bool
1116    $compatEnableFlag("enable_nodejs_child_process_module")
1117    $compatDisableFlag("disable_nodejs_child_process_module")
1118    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1119  # Enables the Node.js non-functional stub child_process module. It is required to use this
1120  # flag with nodejs_compat (or nodejs_compat_v2).
1121 
1122  enableNodeJsWorkerThreadsModule @130 :Bool
1123    $compatEnableFlag("enable_nodejs_worker_threads_module")
1124    $compatDisableFlag("disable_nodejs_worker_threads_module")
1125    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1126  # Enables the Node.js non-functional stub worker_threads module. It is required to use this
1127  # flag with nodejs_compat (or nodejs_compat_v2).
1128 
1129  enableNodeJsStreamWrapModule @131 :Bool
1130    $compatEnableFlag("enable_nodejs_stream_wrap_module")
1131    $compatDisableFlag("disable_nodejs_stream_wrap_module")
1132    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-01-29");
1133  # Enables the Node.js non-functional stub _stream_wrap module. It is required to use this
1134  # flag with nodejs_compat (or nodejs_compat_v2).
1135 
1136  enableNodeJsWasiModule @132 :Bool
1137    $compatEnableFlag("enable_nodejs_wasi_module")
1138    $compatDisableFlag("disable_nodejs_wasi_module")
1139    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-12-04");
1140  # Enables the Node.js non-functional stub wasi module. It is required to use this
1141  # flag with nodejs_compat (or nodejs_compat_v2).
1142 
1143  enableNodeJsDgramModule @133 :Bool
1144    $compatEnableFlag("enable_nodejs_dgram_module")
1145    $compatDisableFlag("disable_nodejs_dgram_module")
1146    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-01-29");
1147  # Enables the Node.js non-functional stub dgram module. It is required to use this
1148  # flag with nodejs_compat (or nodejs_compat_v2).
1149 
1150  enableNodeJsInspectorModule @134 :Bool
1151    $compatEnableFlag("enable_nodejs_inspector_module")
1152    $compatDisableFlag("disable_nodejs_inspector_module")
1153    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-01-29");
1154  # Enables the Node.js non-functional stub inspector module. It is required to use this
1155  # flag with nodejs_compat (or nodejs_compat_v2).
1156 
1157  enableNodeJsTraceEventsModule @135 :Bool
1158    $compatEnableFlag("enable_nodejs_trace_events_module")
1159    $compatDisableFlag("disable_nodejs_trace_events_module")
1160    $impliedByAfterDate(name = "nodeJsCompat", date = "2025-12-04");
1161  # Enables the Node.js non-functional stub trace_events module. It is required to use this
1162  # flag with nodejs_compat (or nodejs_compat_v2).
1163 
1164  enableNodeJsReadlineModule @136 :Bool
1165    $compatEnableFlag("enable_nodejs_readline_module")
1166    $compatDisableFlag("disable_nodejs_readline_module")
1167    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1168  # Enables the Node.js non-functional stub readline module. It is required to use this
1169  # flag with nodejs_compat (or nodejs_compat_v2).
1170 
1171  enableNodeJsReplModule @137 :Bool
1172    $compatEnableFlag("enable_nodejs_repl_module")
1173    $compatDisableFlag("disable_nodejs_repl_module")
1174    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-03-17");
1175  # Enables the Node.js non-functional stub repl module. It is required to use this
1176  # flag with nodejs_compat (or nodejs_compat_v2).
1177 
1178  enableNodeJsSqliteModule @138 :Bool
1179    $compatEnableFlag("enable_nodejs_sqlite_module")
1180    $compatDisableFlag("disable_nodejs_sqlite_module")
1181    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-01-29");
1182  # Enables the Node.js non-functional stub sqlite module. It is required to use this
1183  # flag with nodejs_compat (or nodejs_compat_v2).
1184 
1185  enableCtxExports @139 :Bool
1186    $compatEnableFlag("enable_ctx_exports")
1187    $compatDisableFlag("disable_ctx_exports")
1188    $compatEnableDate("2025-11-17");
1189  # Enable the ctx.exports API.
1190 
1191  pythonExternalSDK @140 :Bool
1192    $compatEnableFlag("enable_python_external_sdk")
1193    $compatDisableFlag("disable_python_external_sdk")
1194    $compatEnableDate("2026-04-21");
1195  # Don't include the Python sdk from the runtime, use a vendored copy.
1196 
1197  fastJsgStruct @141 :Bool
1198    $compatEnableFlag("enable_fast_jsg_struct")
1199    $compatDisableFlag("disable_fast_jsg_struct")
1200    $compatEnableDate("2025-12-03");
1201  # Enables the fast jsg::Struct optimization. With this enabled, JSG_STRUCTS
1202  # will use a more efficient creation pattern that reduces construction time.
1203  # However, optional fields will be explicitly set to undefined rather than
1204  # being omitted, which is an observable behavior change.
1205 
1206  cacheReload @142 :Bool
1207      $compatEnableFlag("cache_reload_enabled")
1208      $compatDisableFlag("cache_reload_disabled")
1209      $experimental;
1210  # Enables the use of cache: reload in the fetch api.
1211 
1212  streamsNodejsV24Compat @143 :Bool
1213    $compatEnableFlag("enable_streams_nodejs_v24_compat")
1214    $compatDisableFlag("disable_streams_nodejs_v24_compat");
1215  # Enables breaking changes to Node.js streams done with the release of Node.js v24.
1216 
1217  pythonCheckRngState @144 : Bool
1218    $compatEnableFlag("python_check_rng_state")
1219    $compatDisableFlag("disable_python_check_rng_state")
1220    $impliedByAfterDate(name = "pythonWorkers", date = "2025-12-16");
1221 
1222  shouldSetImmutablePrototype @145 :Bool
1223    $compatEnableFlag("immutable_api_prototypes")
1224    $compatDisableFlag("mutable_api_prototypes");
1225  # When set, tells JSG to make the prototype of all jsg::Objects immutable.
1226  # TODO(soon): Add the default on date once the flag is verified to be
1227  # generally safe.
1228 
1229  fetchIterableTypeSupport @146 :Bool
1230    $compatEnableFlag("fetch_iterable_type_support")
1231    $compatDisableFlag("no_fetch_iterable_type_support")
1232    $compatEnableDate("2026-02-19");
1233  # Enables passing sync and async iterables as the body of fetch Request or Response.
1234  # Previously, sync iterables like Arrays would be accepted but stringified, and async
1235  # iterables would be treated as regular objects and not iterated over at all. With this
1236  # flag enabled, sync and async iterables will be properly iterated over and their values
1237  # used as the body of the request or response.
1238  # The actual compat flag enables the specific AsyncGeneratorIgnoringStrings type wrapper
1239  # that allows this behavior and allows sync Generator and AsyncGenerator objects to be
1240  # included in kj::OneOf declarations safely with strings and other types. When enabled,
1241  # strings are ignored but Arrays will be treated as iterables and not stringified as before.
1242  # Also see fetchIterableTypeSupportOverrideAdjustment.
1243 
1244  envModuleNullableSupport @147 :Bool
1245    $compatEnableFlag("env_module_nullable_support")
1246    $compatDisableFlag("no_env_module_nullable_support");
1247  # Enables support for null and undefined values in EnvModule's getCurrentEnv() and
1248  # getCurrentExports() methods. When enabled, if the async context contains null or
1249  # undefined values, they will be returned instead of falling through to the worker
1250  # env/exports. This allows more explicit control over env and exports values in async
1251  # contexts.
1252 
1253  preciseTimers @148 :Bool
1254    $compatEnableFlag("precise_timers")
1255    $compatDisableFlag("no_precise_timers")
1256    $experimental;
1257  # Enables precise timers with 3ms granularity. This provides more accurate timing for performance
1258  # measurements and time-sensitive operations.
1259 
1260  fetchIterableTypeSupportOverrideAdjustment @149 :Bool
1261    $compatEnableFlag("fetch_iterable_type_support_override_adjustment")
1262    $compatDisableFlag("no_fetch_iterable_type_support_override_adjustment")
1263    $impliedByAfterDate(name = "fetchIterableTypeSupport", date = "2026-01-15");
1264  # Further adapts the fetch iterable type support to adjust for toString/toPrimitive
1265  # overrides on sync iterable objects. Specifically, if an object passed as the body
1266  # of a fetch Request or Response is sync iterable but has a custom toString or
1267  # toPrimitive method, we will skip treating it as a sync iterable and instead allow
1268  # it to fall through to being handled as a stringified object.
1269 
1270  stripBomInReadAllText @150 :Bool
1271    $compatEnableFlag("strip_bom_in_read_all_text")
1272    $compatDisableFlag("do_not_strip_bom_in_read_all_text")
1273    $compatEnableDate("2026-01-13")
1274    $impliedByAfterDate(name = "pedanticWpt", date = "2026-01-13");
1275  # Instructs the readAllText method in streams to strip the leading UTF8 BOM if present.
1276 
1277  allowIrrevocableStubStorage @151 :Bool
1278    $compatEnableFlag("allow_irrevocable_stub_storage")
1279    $experimental;
1280  # Permits various stub types (e.g. ServiceStub aka Fetcher, DurableObjectClass) to be stored in
1281  # long-term Durable Object storage without any mechanism for the stub target to audit or revoke
1282  # incoming connections.
1283  #
1284  # This feature exists for experimental use only, and will be removed once we have a properly
1285  # auditable and revocable storage mechanism.
1286 
1287  rpcParamsDupStubs @152 :Bool
1288    $compatEnableFlag("rpc_params_dup_stubs")
1289    $compatDisableFlag("rpc_params_transfer_stubs")
1290    $compatEnableDate("2026-01-20");
1291  # Changes the ownership semantics of RPC stubs embedded in the parameters of an RPC call.
1292  #
1293  # When the RPC system was first introduced, RPC stubs that were embedded in the params or return
1294  # value of some other call had their ownership transferred. That is, the original stub was
1295  # implicitly disposed, with a duplicate stub being delivered to the destination.
1296  #
1297  # This turns out to compose poorly with another rule: in the callee, any stubs received in the
1298  # params of a call are automatically disposed when the call returns. These two rules combine to
1299  # mean that if you proxy a call -- i.e. the implementation of an RPC just makes another RPC call
1300  # passing along the same params -- then any stubs in the params get disposed twice. Worse, if
1301  # the eventual recipient of the stub wants to keep a duplicate past the end of the call, this
1302  # may not work because the copy of the stub in the proxy layer gets disposed anyway, breaking the
1303  # connection.
1304  #
1305  # For this reason, the pure-JS implementation of Cap'n Web switched to saying that stubs in params
1306  # do NOT transfer ownership -- they are simply duplicated. This compat flag fixes the Workers
1307  # Runtime built-in RPC to match Cap'n Web behavior.
1308  #
1309  # In particular, this fixes: https://github.com/cloudflare/capnweb/issues/110
1310 
1311  enableNodejsGlobalTimers @153 :Bool
1312    $compatEnableFlag("enable_nodejs_global_timers")
1313    $compatDisableFlag("no_nodejs_global_timers")
1314    $impliedByAfterDate(name = "nodeJsCompat", date = "2026-02-10");
1315  # When enabled, setTimeout, setInterval, clearTimeout, and clearInterval
1316  # are available on globalThis as Node.js-compatible versions from node:timers.
1317  # setTimeout and setInterval return Timeout objects with methods like
1318  # refresh(), ref(), unref(), and hasRef().
1319  # This flag requires nodejs_compat or nodejs_compat_v2 to be enabled.
1320 
1321  noAutoAllocateChunkSize @154 :Bool
1322    $compatEnableFlag("streams_no_default_auto_allocate_chunk_size")
1323    $compatDisableFlag("streams_auto_allocate_chunk_size_default")
1324    $experimental;
1325  # Per the WHATWG Streams spec, byte streams should only have autoAllocateChunkSize
1326  # set when the user explicitly provides it. When not set, non-BYOB reads on byte
1327  # streams won't have a byobRequest available in the pull() callback, and the
1328  # underlying source must use controller.enqueue() to provide data instead.
1329  #
1330  # Our original implementation always defaulted autoAllocateChunkSize to 4096,
1331  # which meant all byte stream reads behaved as BYOB reads. This flag enables
1332  # the spec-compliant behavior where autoAllocateChunkSize is only set when
1333  # explicitly provided by the user.
1334  #
1335  # Code relying on the old behavior that accesses controller.byobRequest without
1336  # checking for null will break. To migrate, either:
1337  # 1. Add a null check: if (controller.byobRequest) { ... }
1338  # 2. Explicitly set autoAllocateChunkSize when creating the stream
1339 
1340  pythonWorkflowsImplicitDeps @155 :Bool
1341    $compatEnableFlag("python_workflows_implicit_dependencies")
1342    $compatDisableFlag("no_python_workflows_implicit_dependencies")
1343    $impliedByAfterDate(name = "pythonWorkers", date = "2026-02-25");
1344  # replaces depends param on steps to an implicit approach with step callables passed as params
1345  # these steps are called internally and act as dependencies
1346 
1347  requireReturnsDefaultExport @156 :Bool
1348    $compatEnableFlag("require_returns_default_export")
1349    $compatDisableFlag("require_returns_namespace")
1350    $compatEnableDate("2026-01-22");
1351  # When enabled, require() will return the default export of a module if it exists.
1352  # If the default export does not exist, it falls back to returning a mutable
1353  # copy of the module namespace object. This matches the behavior that Node.js
1354  # uses for require(esm) where the default export is returned when available.
1355  # This flag is useful for frameworks like Next.js that expect to patch module exports.
1356  #
1357  # TODO(later): Once this is no longer experimental, this flag should be implied by
1358  # exportCommonJsDefaultNamespace (or vice versa) for consistency.
1359 
1360  pythonRequestHeadersPreserveCommas @157 :Bool
1361    $compatEnableFlag("python_request_headers_preserve_commas")
1362    $compatDisableFlag("disable_python_request_headers_preserve_commas")
1363    $compatEnableDate("2026-02-17");
1364  # Preserve commas in Python Request headers rather than treating them as separators,
1365  # while still exposing multiple Set-Cookie headers as distinct values.
1366 
1367  queueExposeErrorCodes @158 :Bool
1368    $compatEnableFlag("queue_expose_error_codes")
1369    $compatDisableFlag("no_queue_expose_error_codes")
1370    $compatEnableDate("2026-03-12");
1371  # When enabled, queue operations will include detailed error information (error code and cause)
1372 
1373  textDecoderReplaceSurrogates @159 :Bool
1374    $compatEnableFlag("text_decoder_replace_surrogates")
1375    $compatDisableFlag("disable_text_decoder_replace_surrogates")
1376    $compatEnableDate("2026-02-24")
1377    $impliedByAfterDate(name = "pedanticWpt", date = "2026-02-24");
1378  # When enabled, the UTF-16le TextDecoder will replace lone surrogates with U+FFFD
1379  # (the Unicode replacement character) as required by the spec. Previously, lone
1380  # surrogates were passed through unchanged, producing non-well-formed strings.
1381 
1382  containersPidNamespace @160 :Bool
1383    $compatEnableFlag("containers_pid_namespace")
1384    $compatDisableFlag("no_containers_pid_namespace")
1385    $compatEnableDate("2026-04-01");
1386  # When enabled, containers attached to Durable Objects do NOT share the host PID namespace
1387  # (they get their own isolated PID namespace). When disabled (the default), containers share
1388  # the host PID namespace.
1389 
1390  deleteAllDeletesAlarm @161 :Bool
1391    $compatEnableFlag("delete_all_deletes_alarm")
1392    $compatDisableFlag("delete_all_preserves_alarm")
1393    $compatEnableDate("2026-02-24");
1394  # When enabled, calling storage.deleteAll() on a Durable Object also deletes
1395  # any scheduled alarm, in addition to deleting all stored key-value data.
1396  #
1397  # Previously, deleteAll() preserved the alarm state. This was surprising
1398  # behavior since the intent of deleteAll() is to clear all state.
1399 
1400  unhandledRejectionAfterMicrotaskCheckpoint @162 :Bool
1401    $compatEnableFlag("unhandled_rejection_after_microtask_checkpoint")
1402    $compatDisableFlag("no_unhandled_rejection_after_microtask_checkpoint")
1403    $compatEnableDate("2026-03-03");
1404  # When enabled, unhandledrejection processing is deferred until the microtask
1405  # checkpoint completes, avoiding misfires on multi-tick promise chains.
1406 
1407  textDecoderCjkDecoder @163 :Bool
1408    $compatEnableFlag("text_decoder_cjk_decoder")
1409    $compatDisableFlag("disable_text_decoder_cjk_decoder")
1410    $compatEnableDate("2026-03-03");
1411  # Enables the dedicated CJK TextDecoder implementation for overrides and
1412  # Big5 lead-byte handling instead of the legacy ICU-only path.
1413 
1414  websocketCloseReasonByteLimit @164 :Bool
1415      $compatEnableFlag("websocket_close_reason_byte_limit")
1416      $compatDisableFlag("no_websocket_close_reason_byte_limit")
1417      $compatEnableDate("2026-03-03");
1418  # When enabled, WebSocket close() throws a SyntaxError DOMException if the
1419  # reason string exceeds 123 bytes when UTF-8 encoded, as required by the
1420  # WHATWG WebSocket spec and RFC 6455 Section 5.5. Previously, workerd allowed
1421  # arbitrarily long close reasons without validation.
1422 
1423  enableVersionApi @165 :Bool
1424    $compatEnableFlag("enable_version_api")
1425    $experimental;
1426  # Enables version-related APIs. This currently only enables the `version` option in loopback
1427  # bindings to specify a requested version and exposes `ctx.version`. The behaviour of this flag
1428  # will change in the future.
1429 
1430  websocketBinaryTypeDefault @166 :Bool
1431      $compatEnableFlag("websocket_standard_binary_type")
1432      $compatDisableFlag("no_websocket_standard_binary_type")
1433      $compatEnableDate("2026-03-17");
1434  # Per the WHATWG WebSocket spec, the binaryType attribute defaults to "blob"
1435  # and binary messages are delivered as Blob objects. Previously, workerd did
1436  # not expose the binaryType property at all and always delivered binary
1437  # messages as ArrayBuffer. When this flag is enabled, binaryType defaults to
1438  # "blob" and binary messages are delivered as Blob. Workers that set
1439  # binaryType to "arraybuffer" will continue to receive ArrayBuffer regardless
1440  # of this flag.
1441  #
1442  # Note: This flag has no effect on the Durable Object hibernatable WebSocket
1443  # message handler (webSocketMessage). That handler always receives binary data
1444  # as ArrayBuffer, since it operates outside the normal WebSocket read loop.
1445 
1446  writableStreamSpecCompliantWriter @167 :Bool
1447      $compatEnableFlag("writable_stream_spec_compliant_writer")
1448      $compatDisableFlag("no_writable_stream_spec_compliant_writer")
1449      $compatEnableDate("2026-03-24");
1450  # Fixes several WritableStream spec compliance issues around writer
1451  # lock/release behavior.
1452 
1453  encoderStreamSpecCompliantBackpressure @168 :Bool
1454      $compatEnableFlag("encoder_stream_spec_compliant_backpressure")
1455      $compatDisableFlag("no_encoder_stream_spec_compliant_backpressure")
1456      $compatEnableDate("2026-03-24");
1457  # Fixes TextEncoderStream and TextDecoderStream to use the correct readable
1458  # side high water mark of 0 (per the WHATWG Encoding spec), instead of 1.
1459  # With HWM=0 the readable side starts with backpressure, so writes correctly
1460  # block until a reader pulls. Previously HWM defaulted to 1, which caused
1461  # pull() to fire at startup, clearing backpressure before any write.
1462 
1463  specCompliantPropertyAttributes @169 :Bool
1464      $compatEnableFlag("spec_compliant_property_attributes")
1465      $compatDisableFlag("no_spec_compliant_property_attributes")
1466      $experimental;
1467  # Fixes several Web IDL compliance issues on property attributes:
1468  #  - Constructor .length reflects the number of required arguments instead
1469  #    of always being 0.
1470  #  - Method and static method .length reflects the number of required
1471  #    arguments instead of always being 0.
1472  #  - Getter .length is explicitly 0 and setter .length is 1.
1473  #  - Getter .name is "get <name>" and setter .name is "set <name>" per the
1474  #    Web IDL spec, instead of empty strings.
1475  #  - Constants gain DontDelete (non-configurable) on both the constructor
1476  #    and prototype, matching { writable: false, enumerable: true,
1477  #    configurable: false } per Web IDL.
1478  #  - Interface objects (nested types) become own properties of globalThis
1479  #    with { writable: true, enumerable: false, configurable: true }, instead
1480  #    of being inherited from the prototype chain.
1481 
1482  workflowsPreserveNonRetryableErrorMessage @170 :Bool
1483      $compatEnableFlag("workflows_preserve_non_retryable_error_message")
1484      $compatDisableFlag("workflows_replace_non_retryable_error_message")
1485      $compatEnableDate("2026-05-14");
1486  # When enabled, if a Workflow step throws a NonRetryableError, the error message
1487  # and name are preserved on the thrown exception instead of being replaced with
1488  # a generic "NonRetryableError" string.
1489 
1490  webSocketAutoReplyToClose @171 :Bool
1491    $compatEnableFlag("web_socket_auto_reply_to_close")
1492    $compatDisableFlag("web_socket_manual_reply_to_close")
1493    $compatEnableDate("2026-04-07");
1494  # When enabled, a reciprocal Close frame is automatically sent through the
1495  # outgoing message pump when a server-initiated close is received, and the
1496  # WebSocket readyState is CLOSED (3) when the close event fires. Previously,
1497  # no close reply was sent and readyState was CLOSING (2). The WebSocket spec
1498  # requires readyState to be CLOSED when the close event is dispatched.
1499 
1500  enableCtxVersionMetadata @172 :Bool
1501    $compatEnableFlag("enable_ctx_version_metadata")
1502    $experimental;
1503  # When paired with `enable_version_api`, also exposes `ctx.version.metadata`. This is a separate
1504  # flag as we haven't decided on the exact behaviour of `ctx.version.metadata`, but the rest of
1505  # `ctx.version` is much more well defined. The behaviour of this flag will change in the future.
1506 
1507  noResizableArrayBufferInBlob @173 :Bool
1508      $compatEnableFlag("no_resizable_array_buffer_in_blob")
1509      $compatDisableFlag("resizable_array_buffer_in_blob");
1510  # When enabled, creating a Blob with a resizable ArrayBuffer will throw a TypeError, matching
1511  # expected spec behavior.
1512 
1513  diagnosticsChannelHasSubscribersGetter @174 :Bool
1514      $compatEnableFlag("diagnostics_channel_has_subscribers_getter")
1515      $compatDisableFlag("no_diagnostics_channel_has_subscribers_getter")
1516      $compatEnableDate("2026-05-19");
1517  # Node.js' `diagnostics_channel.Channel.hasSubscribers` and
1518  # `TracingChannel.hasSubscribers` are boolean getter properties, not methods.
1519  # Originally, workerd registered `Channel.hasSubscribers` as a method (so users
1520  # had to call `ch.hasSubscribers()` with parentheses). When this flag is
1521  # enabled, `hasSubscribers` becomes a read-only getter that evaluates directly
1522  # to a boolean, matching Node.js behavior.
1523  # See: https://nodejs.org/dist/latest-v20.x/docs/api/diagnostics_channel.html#channelhassubscribers
1524 
1525  workflowsStepRollback @175 :Bool
1526    $compatEnableFlag("workflows_step_rollback")
1527    $experimental;
1528  # When enabled, WorkflowEntrypoint wraps the step object so that step.do()
1529  # and step.waitForEvent() return a StepPromise with a .rollback() method.
1530  # The rollback function is bundled into the RPC call for the engine to invoke
1531  # as a compensation action on failure. Without this flag, the step object is
1532  # passed through unwrapped and .rollback() is not available.
1533 
1534  pythonProcessPthFiles @176 :Bool
1535      $compatEnableFlag("python_process_pth_files")
1536      $compatDisableFlag("disable_python_process_pth_files")
1537      $compatEnableDate("2026-05-26");
1538  # When enabled, Python Workers process `.pth` files placed in the
1539  # `python_modules/` directory by calling `site.addsitedir()` on it during
1540  # startup. This allows packages to extend `sys.path` declaratively (e.g. to
1541  # add subdirectories or register import hooks). Without this flag, `.pth`
1542  # files in `python_modules/` are ignored.
1543}