feat: add raw_json() to the event returned by webhook verification

from_dict reads only the properties it was generated for, so a field Seam adds
to an existing event between SDK releases is silently discarded. #651 made
parsing degrade instead of raise, but did not keep the payload, so there was no
way to reach a new field short of upgrading.

SeamWebhook.verify() now returns an event carrying raw_json():

    json.loads(event.raw_json())["a_field_this_version_predates"]

DeepAttrDict answers the same call, so the unrecognized-event branch and the
typed branch are handled the same way. This matters because the fallback is not
otherwise interchangeable with a generated event: reading a missing key raises
AttributeError where a dataclass returns None, so generic code written against
the declared union breaks on it.

Scoped to events. It is there for the verify return, not as a general accessor
on every model. A method rather than a property because the call is where the
serialization happens; the event retains the decoded payload and serializes on
demand. The retained payload is repr=False and compare=False, so it changes
neither the repr nor equality.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M2kJ4nGaM8imZCVMEKjmXA

Author: claude

codegen/layouts/partials/resource-dataclass.hbs

@@ -25,6 +25,15 @@
 {{#each properties}}
 {{../memberIndent}}{{pythonIdentifier name}}: {{type}}
 {{/each}}
+{{#if @root.hasRawJson}}
+{{#unless isNested}}
+{{memberIndent}}_raw: Optional[Dict[str, Any]] = field(default=None, repr=False, compare=False)
+
+{{memberIndent}}def raw_json(self) -> str:
+{{memberIndent}}    """Return the payload this was parsed from, as JSON."""
+{{memberIndent}}    return json.dumps(self._raw)
+{{/unless}}
+{{/if}}
 
 {{memberIndent}}@classmethod
 {{memberIndent}}def from_dict(cls, d: Any):
@@ -37,4 +46,9 @@
 {{#each properties}}
 {{../memberIndent}}        {{pythonIdentifier name}}={{#if isRequiredObject}}_required_object_from_dict(cls.{{nestedClassName}}, d.get("{{name}}")){{else}}{{#if isObject}}_object_from_dict(cls.{{nestedClassName}}, d.get("{{name}}")){{else}}{{#if isDiscriminatedObjectList}}_discriminated_list_from_dict(d.get("{{name}}"), cls._{{nestedClassName}}Variants, "{{discriminator}}"){{else}}{{#if isObjectList}}_object_list_from_dict(cls.{{nestedClassName}}, d.get("{{name}}")){{else}}{{#if isDictParam}}_record_from_dict({{/if}}d.get("{{name}}", None){{#if isDictParam}}){{/if}}{{/if}}{{/if}}{{/if}}{{/if}},
 {{/each}}
+{{#if @root.hasRawJson}}
+{{#unless isNested}}
+{{memberIndent}}        _raw=d,
+{{/unless}}
+{{/if}}
 {{memberIndent}}    )

codegen/layouts/resource.hbs

@@ -1,5 +1,8 @@
 from typing import Any, Dict, List, Literal, Optional, {{#if union.secondaryDiscriminator}}Tuple, {{/if}}Union{{#if union}}, cast{{/if}}
-from dataclasses import dataclass
+from dataclasses import dataclass{{#if hasRawJson}}, field{{/if}}
+{{#if hasRawJson}}
+import json
+{{/if}}
 from ..deep_attr_dict import DeepAttrDict
 from ..parse import (
     discriminated_list_from_dict as _discriminated_list_from_dict,

codegen/lib/layouts/resources.ts

@@ -18,6 +18,7 @@ import {
 
 export interface ResourceLayoutContext {
   className: string
+  hasRawJson?: boolean
   moduleName: string
   isDeprecated: boolean
   deprecationMessage: string
@@ -703,8 +704,10 @@ export const getResourceLayoutContexts = (
   const eventModel = blueprint.resources.find(
     ({ resourceType }) => resourceType === 'event',
   )
-  resources.push(
-    buildUnionResource(
+  resources.push({
+    // raw_json exists for the webhook verify return, so the events carry it and
+    // nothing else does.
+    ...buildUnionResource(
       'SeamEvent',
       'event_type',
       'seam_event_from_dict',
@@ -718,7 +721,8 @@ export const getResourceLayoutContexts = (
       eventModel?.isDeprecated ?? false,
       eventModel?.deprecationMessage ?? '',
     ),
-  )
+    hasRawJson: true,
+  })
 
   const actionAttemptModel = blueprint.resources.find(
     ({ resourceType }) => resourceType === 'action_attempt',

seam/deep_attr_dict.py

@@ -1,3 +1,6 @@
+import json
+
+
 class DeepAttrDict(dict):
     """A dict whose keys are also readable as attributes, nested dicts included.
 
@@ -15,6 +18,10 @@ def __init__(self, value=None):
         else:
             raise TypeError("expected dict")
 
+    def raw_json(self):
+        """Return the payload this was parsed from, as JSON."""
+        return json.dumps(self)
+
     def __setitem__(self, key, value):
         if isinstance(value, dict) and not isinstance(value, DeepAttrDict):
             value = DeepAttrDict(value)