fix(beta): omit compaction encrypted_content on request round-trip

src/anthropic/_utils/_transform.py

@@ -30,6 +30,7 @@
     is_annotated_type,
     strip_annotated_type,
 )
+from ..lib._compaction import omit_compaction_encrypted_content
 
 _T = TypeVar("_T")
 
@@ -109,7 +110,7 @@ class Params(TypedDict, total=False):
     It should be noted that the transformations that this function does are not represented in the type system.
     """
     transformed = _transform_recursive(data, annotation=cast(type, expected_type))
-    return cast(_T, transformed)
+    return cast(_T, omit_compaction_encrypted_content(transformed))
 
 
 @lru_cache(maxsize=8096)
@@ -316,7 +317,7 @@ class Params(TypedDict, total=False):
     It should be noted that the transformations that this function does are not represented in the type system.
     """
     transformed = await _async_transform_recursive(data, annotation=cast(type, expected_type))
-    return cast(_T, transformed)
+    return cast(_T, omit_compaction_encrypted_content(transformed))
 
 
 async def _async_transform_recursive(

src/anthropic/lib/_compaction.py

@@ -0,0 +1,56 @@
+"""Request-side handling of compaction content blocks.
+
+Response compaction blocks include ``encrypted_content``, but the Messages API
+rejects that field on request blocks (``Extra inputs are not permitted``). The
+documented round-trip is ``messages.append(response.content)``, so the SDK
+omits ``encrypted_content`` from compaction blocks while serializing requests.
+
+This module is not Stainless-generated; keep request-only behavior here so it
+survives OpenAPI regenerations of the TypedDicts.
+"""
+
+from __future__ import annotations
+
+from typing import Any, TypeVar, cast
+
+_T = TypeVar("_T")
+
+
+def omit_compaction_encrypted_content(data: _T) -> _T:
+    """Drop ``encrypted_content`` from compaction blocks in a request payload.
+
+    Other block types that legitimately send ``encrypted_content`` (web search
+    results, advisor redacted results) are left unchanged. Objects that do not
+    contain a compaction block are returned unchanged so request transform
+    identity optimizations keep working.
+    """
+    return cast(_T, _omit_compaction_encrypted_content(data))
+
+
+def _omit_compaction_encrypted_content(data: object) -> Any:
+    if isinstance(data, list):
+        items = cast("list[object]", data)
+        new_items: list[object] = [_omit_compaction_encrypted_content(item) for item in items]
+        if all(new is old for new, old in zip(new_items, items)):
+            return cast(Any, data)
+        return cast(Any, new_items)
+    if isinstance(data, tuple):
+        tuple_items = cast("tuple[object, ...]", data)
+        new_tuple = tuple(_omit_compaction_encrypted_content(item) for item in tuple_items)
+        if all(new is old for new, old in zip(new_tuple, tuple_items)):
+            return cast(Any, data)
+        return cast(Any, new_tuple)
+    if not isinstance(data, dict):
+        return data
+
+    mapping = cast("dict[str, object]", data)
+    nested: dict[str, object] = {key: _omit_compaction_encrypted_content(value) for key, value in mapping.items()}
+    changed = any(nested[key] is not value for key, value in mapping.items())
+    if mapping.get("type") == "compaction" and "encrypted_content" in mapping:
+        if not changed:
+            nested = dict(mapping)
+        nested.pop("encrypted_content", None)
+        return cast(Any, nested)
+    if changed:
+        return cast(Any, nested)
+    return cast(Any, data)

src/anthropic/types/beta/beta_compaction_block.py

@@ -20,6 +20,11 @@ class BetaCompactionBlock(BaseModel):
     """Summary of compacted content, or null if compaction failed"""
 
     encrypted_content: Optional[str] = None
-    """Opaque metadata from prior compaction, to be round-tripped verbatim"""
+    """Opaque metadata returned on compaction response blocks.
+
+    The Messages API rejects this field on request compaction blocks, so the SDK
+    omits it when serializing requests. Clients can still append ``response.content``
+    verbatim; the field is dropped on the wire, not on the response object.
+    """
 
     type: Literal["compaction"]

src/anthropic/types/beta/beta_compaction_block_param.py

@@ -29,4 +29,9 @@ class BetaCompactionBlockParam(TypedDict, total=False):
     """Summary of previously compacted content, or null if compaction failed"""
 
     encrypted_content: Optional[str]
-    """Opaque metadata from prior compaction, to be round-tripped verbatim"""
+    """Opaque metadata returned on compaction response blocks.
+
+    The Messages API rejects this field on request compaction blocks, so the SDK
+    omits it when serializing requests. Prefer appending ``response.content``
+    unmodified; do not rely on this field being sent.
+    """