diff --git a/main/acle.md b/main/acle.md
index 34b1283d..08a5c1c8 100644
--- a/main/acle.md
+++ b/main/acle.md
@@ -400,6 +400,7 @@ Armv8.4-A [[ARMARMv84]](#ARMARMv84). Support is added for the Dot Product intrin
 * Added a requirement for function version declaration in Function Multi Versioning.
 * Fixed some rendering issues in the online Markdown documentation and fixed
   a misplaced anchor.
+* Added [`__arm_agnostic`](#arm_agnostic) keyword attribute
 
 ### References
 
@@ -826,6 +827,7 @@ predefine the associated macro to a nonzero value.
 
 | **Name**                                                    | **Target**            | **Predefined macro**              |
 | ----------------------------------------------------------- | --------------------- | --------------------------------- |
+| [`__arm_agnostic`](#arm_agnostic)                           | function type         | `__ARM_FEATURE_SME`               |
 | [`__arm_locally_streaming`](#arm_locally_streaming)         | function declaration  | `__ARM_FEATURE_LOCALLY_STREAMING` |
 | [`__arm_in`](#ways-of-sharing-state)                        | function type         | Argument-dependent                |
 | [`__arm_inout`](#ways-of-sharing-state)                     | function type         | Argument-dependent                |
@@ -4836,6 +4838,30 @@ if such a restoration is necessary. For example:
    }
 ```
 
+## `__arm_agnostic`
+
+A function with the `__arm_agnostic` [keyword attribute](#keyword-attributes)
+must preserve the architectural state that is specified by its arguments when
+such state exists at runtime. The function is otherwise unconcerned with this
+state.
+
+The `__arm_agnostic` [keyword attribute](#keyword-attributes) applies to
+**function types** and accepts the following arguments:
+
+```"sme_za_state"```
+
+*   This attribute affects the ABI of a function, which must implement an
+    [agnostic-ZA interface](#agnostic-za). It is the compiler's responsibility
+    to ensure that the function's object code honors the ABI requirements.
+
+*   The use of `__arm_agnostic("sme_za_state")` allows writing functions that
+    are compatible with ZA state without having to share ZA state with the
+    caller, as required by `__arm_preserves`.
+
+*   It is not valid for a function declaration with
+    `__arm_agnostic("sme_za_state")` to [share](#shares-state) PSTATE.ZA state
+    with its caller.
+
 ## Mapping to the Procedure Call Standard
 
 [[AAPCS64]](#AAPCS64) classifies functions as having one of the following
@@ -4847,6 +4873,10 @@ interfaces:
 
 *   a “shared-ZA” interface
 
+<span id="agnostic-za"></span>
+
+*   a "agnostic-ZA" interface
+
 If a C or C++ function F forms part of the object code's ABI, that
 object code function has a shared-ZA interface if and only if at least
 one of the following is true:
@@ -4855,7 +4885,17 @@ one of the following is true:
 
 *   F shares ZT0 with its caller
 
-All other functions have a private-ZA interface.
+All other functions have either a private-ZA or an agnostic-ZA interface.
+
+If F implements an agnostic-ZA interface and PSTATE.ZA is available at runtime,
+then a call to F must return with its ZA state unchanged in accordance
+to the [[AAPCS64]](#AAPCS64). In practice this means that calls to F don't have
+to emit code to set up a lazy-save for ZA or to preserve other state like ZT0
+when such state is live at the call site.
+
+The implementation of F must not make any assumptions on the availability of
+PSTATE.ZA or any architectural state associated with it.
+
 
 ## Function definitions