diff --git a/conformance/runner/go/main.go b/conformance/runner/go/main.go
index d06d35fa9..8439f9077 100644
--- a/conformance/runner/go/main.go
+++ b/conformance/runner/go/main.go
@@ -538,6 +538,22 @@ func executeOperation(ctx context.Context, account *basecamp.AccountClient, tc T
 		_, err := account.Todos().Update(ctx, todoID, req)
 		return operationResult{err: err}
 
+	case "UpdateScheduleEntry":
+		// Participants are presence-bearing: absent means "leave them alone"
+		// (BC3 preserves only because the key is missing), an empty non-nil
+		// slice means "remove everyone".
+		entryID := getInt64Param(tc.PathParams, "entryId")
+		req := &basecamp.UpdateScheduleEntryRequest{
+			Summary:  getStringParam(tc.RequestBody, "summary"),
+			StartsAt: getStringParam(tc.RequestBody, "starts_at"),
+			EndsAt:   getStringParam(tc.RequestBody, "ends_at"),
+		}
+		if ids, ok := getInt64SliceParam(tc.RequestBody, "participant_ids"); ok {
+			req.ParticipantIDs = ids
+		}
+		_, err := account.Schedules().UpdateEntry(ctx, entryID, req)
+		return operationResult{err: err}
+
 	case "UpdateCard":
 		// Merge-safe composite: GET then PUT, resending the fetched due_on.
 		_, err := account.Cards().Update(ctx, getInt64Param(tc.PathParams, "cardId"), cardUpdateRequest(tc.RequestBody))
diff --git a/conformance/runner/python/runner.py b/conformance/runner/python/runner.py
index 7a98cd503..73e3259f1 100644
--- a/conformance/runner/python/runner.py
+++ b/conformance/runner/python/runner.py
@@ -26,6 +26,7 @@
 # Wire keys for todo write operations; identical to the Python kwarg /
 # edit-attribute names, so fixtures map onto the SDK surface directly.
 _TODO_WRITE_FIELDS = ("content", "description", "assignee_ids", "completion_subscriber_ids", "due_on", "starts_on", "notify")
+_SCHEDULE_ENTRY_WRITE_FIELDS = ("summary", "starts_at", "ends_at", "description", "participant_ids", "all_day", "notify")
 _CARD_WRITE_FIELDS = ("title", "content", "due_on", "assignee_ids")
 
 # Sentinel distinguishing "key absent from the JSON body" from a present None.
@@ -102,6 +103,13 @@ def __call__(self, operation: str, *, path_params: dict, query_params: dict, bod
                     todo_id=path_params["todoId"],
                     **{k: body[k] for k in _TODO_WRITE_FIELDS if k in body},
                 )
+            case "UpdateScheduleEntry":
+                # Only pass keys the fixture carries: _compact strips None, so
+                # an absent participant_ids stays off the wire while [] survives.
+                return self._account.schedules.update_entry(
+                    entry_id=path_params["entryId"],
+                    **{k: body[k] for k in _SCHEDULE_ENTRY_WRITE_FIELDS if k in body},
+                )
             case "UpdateCard":
                 # Merge-safe composite: GET then PUT, resending the fetched due_on.
                 return self._account.cards.update(
diff --git a/conformance/runner/ruby/runner.rb b/conformance/runner/ruby/runner.rb
index 1385821d4..94ba320cb 100644
--- a/conformance/runner/ruby/runner.rb
+++ b/conformance/runner/ruby/runner.rb
@@ -156,6 +156,10 @@ def call(operation, path_params: {}, query_params: {}, body: nil, path: "")
         todo_id: path_params["todoId"],
         **todo_write_kwargs(body)
       )
+    when "UpdateScheduleEntry"
+      # Only pass keys the fixture carries: compact_params strips nil, so an
+      # absent participant_ids stays off the wire while [] survives.
+      @account.schedules.update_entry(entry_id: path_params["entryId"], **schedule_entry_write_kwargs(body))
     when "UpdateCard"
       # Merge-safe composite: GET then PUT, resending the fetched due_on.
       @account.cards.update(card_id: path_params["cardId"], **card_write_kwargs(body))
@@ -217,6 +221,13 @@ def call(operation, path_params: {}, query_params: {}, body: nil, path: "")
     content description assignee_ids completion_subscriber_ids due_on starts_on notify
   ].freeze
 
+  SCHEDULE_ENTRY_WRITE_KEYS = %w[summary starts_at ends_at description participant_ids all_day notify].freeze
+
+  def schedule_entry_write_kwargs(body)
+    SCHEDULE_ENTRY_WRITE_KEYS.select { |key| (body || {}).key?(key) } \
+      .to_h { |key| [key.to_sym, body[key]] }
+  end
+
   CARD_WRITE_KEYS = %w[title content due_on assignee_ids].freeze
 
   def card_write_kwargs(body)
diff --git a/conformance/runner/typescript/runner.test.ts b/conformance/runner/typescript/runner.test.ts
index 4f19df9fc..6e87dcccd 100644
--- a/conformance/runner/typescript/runner.test.ts
+++ b/conformance/runner/typescript/runner.test.ts
@@ -234,6 +234,17 @@ async function executeOperation(
         await client.todos.update(Number(params.todoId), mapTodoWireFields(body));
         break;
 
+      case "UpdateScheduleEntry":
+        // Only spread participantIds when the fixture carries the key: an
+        // absent key must not become [] or null on the wire.
+        await client.schedules.updateEntry(Number(params.entryId), {
+          ...(body.summary !== undefined ? { summary: String(body.summary) } : {}),
+          ...(body.participant_ids !== undefined
+            ? { participantIds: body.participant_ids as number[] }
+            : {}),
+        });
+        break;
+
       case "UpdateCard":
         // Merge-safe composite: GET then PUT, resending the fetched due_on.
         await client.cards.update(Number(params.cardId), {
diff --git a/conformance/tests/schedule_entries_write.json b/conformance/tests/schedule_entries_write.json
new file mode 100644
index 000000000..3e66ba708
--- /dev/null
+++ b/conformance/tests/schedule_entries_write.json
@@ -0,0 +1,192 @@
+[
+  {
+    "name": "update-omits-participant-ids: an unaddressed participant list stays off the wire",
+    "description": "BC3 preserves the entry's participants only because the key is absent \u2014 until basecamp/bc3#12425 the controller called replace_participants unconditionally, so an omitted key wiped every participant and notified them. The SDK's job is narrow but load-bearing: when the caller says nothing about participants, participant_ids must not appear in the body at all. A compactor that emitted null, or a default that emitted [], would clear the list on the server.",
+    "operation": "UpdateScheduleEntry",
+    "method": "PUT",
+    "path": "/schedule_entries/{entryId}",
+    "pathParams": {
+      "entryId": 1069479523
+    },
+    "requestBody": {
+      "summary": "Team Meeting"
+    },
+    "mockResponses": [
+      {
+        "status": 200,
+        "headers": {
+          "Content-Type": "application/json"
+        },
+        "body": {
+          "id": 1069479523,
+          "status": "active",
+          "visible_to_clients": false,
+          "created_at": "2026-01-01T00:00:00Z",
+          "updated_at": "2026-01-01T00:00:00Z",
+          "title": "Team Meeting",
+          "inherits_status": true,
+          "type": "Schedule::Entry",
+          "url": "https://3.basecampapi.com/999/buckets/1/schedule_entries/1069479523.json",
+          "app_url": "https://3.basecamp.com/999/buckets/1/schedule_entries/1069479523",
+          "summary": "Team Meeting",
+          "all_day": false,
+          "starts_at": "2026-06-05T06:00:00Z",
+          "ends_at": "2026-06-05T08:30:00Z",
+          "participants": [
+            {
+              "id": 1049715914,
+              "name": "Victor Cooper"
+            },
+            {
+              "id": 1049715915,
+              "name": "Annie Bryan"
+            }
+          ],
+          "description_attachments": [],
+          "parent": {
+            "id": 1069479521,
+            "title": "Schedule",
+            "type": "Schedule",
+            "url": "https://3.basecampapi.com/999/buckets/1/schedules/1069479521.json",
+            "app_url": "https://3.basecamp.com/999/buckets/1/schedules/1069479521"
+          },
+          "bucket": {
+            "id": 1,
+            "name": "The Leto Laptop",
+            "type": "Project"
+          },
+          "creator": {
+            "id": 1049715914,
+            "name": "Victor Cooper",
+            "email_address": "victor@honchodesign.com",
+            "created_at": "2026-01-01T00:00:00Z",
+            "updated_at": "2026-01-01T00:00:00Z"
+          }
+        }
+      }
+    ],
+    "assertions": [
+      {
+        "type": "requestCount",
+        "expected": 1
+      },
+      {
+        "type": "requestMethod",
+        "expected": "PUT",
+        "index": 0
+      },
+      {
+        "type": "requestBody",
+        "path": "summary",
+        "expected": "Team Meeting",
+        "index": 0
+      },
+      {
+        "type": "requestBodyAbsent",
+        "path": "participant_ids",
+        "index": 0
+      },
+      {
+        "type": "noError"
+      }
+    ],
+    "tags": [
+      "schedule-entries",
+      "participants",
+      "omission"
+    ]
+  },
+  {
+    "name": "update-empty-participant-ids: an explicit empty list reaches the wire",
+    "description": "The counterpart to omission: passing an explicitly empty list means \"remove everyone\" and must be sent as participant_ids: []. Ruby's compact_params and Python's _compact strip nil/None but not empty collections, so this distinguishes \"not addressed\" from \"addressed and cleared\" \u2014 the whole point of the BC3 guard.",
+    "operation": "UpdateScheduleEntry",
+    "method": "PUT",
+    "path": "/schedule_entries/{entryId}",
+    "pathParams": {
+      "entryId": 1069479523
+    },
+    "requestBody": {
+      "summary": "Team Meeting",
+      "participant_ids": []
+    },
+    "mockResponses": [
+      {
+        "status": 200,
+        "headers": {
+          "Content-Type": "application/json"
+        },
+        "body": {
+          "id": 1069479523,
+          "status": "active",
+          "visible_to_clients": false,
+          "created_at": "2026-01-01T00:00:00Z",
+          "updated_at": "2026-01-01T00:00:00Z",
+          "title": "Team Meeting",
+          "inherits_status": true,
+          "type": "Schedule::Entry",
+          "url": "https://3.basecampapi.com/999/buckets/1/schedule_entries/1069479523.json",
+          "app_url": "https://3.basecamp.com/999/buckets/1/schedule_entries/1069479523",
+          "summary": "Team Meeting",
+          "all_day": false,
+          "starts_at": "2026-06-05T06:00:00Z",
+          "ends_at": "2026-06-05T08:30:00Z",
+          "participants": [
+            {
+              "id": 1049715914,
+              "name": "Victor Cooper"
+            },
+            {
+              "id": 1049715915,
+              "name": "Annie Bryan"
+            }
+          ],
+          "description_attachments": [],
+          "parent": {
+            "id": 1069479521,
+            "title": "Schedule",
+            "type": "Schedule",
+            "url": "https://3.basecampapi.com/999/buckets/1/schedules/1069479521.json",
+            "app_url": "https://3.basecamp.com/999/buckets/1/schedules/1069479521"
+          },
+          "bucket": {
+            "id": 1,
+            "name": "The Leto Laptop",
+            "type": "Project"
+          },
+          "creator": {
+            "id": 1049715914,
+            "name": "Victor Cooper",
+            "email_address": "victor@honchodesign.com",
+            "created_at": "2026-01-01T00:00:00Z",
+            "updated_at": "2026-01-01T00:00:00Z"
+          }
+        }
+      }
+    ],
+    "assertions": [
+      {
+        "type": "requestCount",
+        "expected": 1
+      },
+      {
+        "type": "requestMethod",
+        "expected": "PUT",
+        "index": 0
+      },
+      {
+        "type": "requestBody",
+        "path": "participant_ids",
+        "expected": [],
+        "index": 0
+      },
+      {
+        "type": "noError"
+      }
+    ],
+    "tags": [
+      "schedule-entries",
+      "participants",
+      "clear"
+    ]
+  }
+]
diff --git a/go/pkg/basecamp/api-provenance.json b/go/pkg/basecamp/api-provenance.json
index 83295cf85..b6ce27f98 100644
--- a/go/pkg/basecamp/api-provenance.json
+++ b/go/pkg/basecamp/api-provenance.json
@@ -1,8 +1,8 @@
 {
   "bc3": {
     "branch": "master",
-    "revision": "c308693171680e8ec9d3ae9e68181ef2ea80f077",
-    "date": "2026-07-26"
+    "revision": "dffa7e11b3337b17454d9a82301be3e94226a858",
+    "date": "2026-07-28"
   },
   "compatibility": {
     "bc3-four": {
diff --git a/go/pkg/basecamp/version.go b/go/pkg/basecamp/version.go
index 2aa6e4af6..7d6cd140a 100644
--- a/go/pkg/basecamp/version.go
+++ b/go/pkg/basecamp/version.go
@@ -4,4 +4,4 @@ package basecamp
 const Version = "0.9.0"
 
 // APIVersion is the Basecamp API version this SDK targets.
-const APIVersion = "2026-07-26"
+const APIVersion = "2026-07-28"
diff --git a/go/pkg/generated/client.gen.go b/go/pkg/generated/client.gen.go
index b596c64d3..1144f1072 100644
--- a/go/pkg/generated/client.gen.go
+++ b/go/pkg/generated/client.gen.go
@@ -2953,10 +2953,20 @@ type UpdateQuestionResponseContent = Question
 
 // UpdateScheduleEntryRequestContent defines model for UpdateScheduleEntryRequestContent.
 type UpdateScheduleEntryRequestContent struct {
-	AllDay         *bool     `json:"all_day,omitempty"`
-	Description    string    `json:"description,omitempty"`
-	EndsAt         time.Time `json:"ends_at,omitempty"`
-	Notify         *bool     `json:"notify,omitempty"`
+	AllDay      *bool     `json:"all_day,omitempty"`
+	Description string    `json:"description,omitempty"`
+	EndsAt      time.Time `json:"ends_at,omitempty"`
+	Notify      *bool     `json:"notify,omitempty"`
+
+	// ParticipantIds Replaces the entry's participants.
+	//
+	// Omitting this member preserves the current participants; sending an empty
+	// array clears them. That guarantee is BC3-side and recent: until
+	// basecamp/bc3#12425, `Schedules::EntriesController#update` called
+	// `replace_participants` unconditionally, so any update omitting the key —
+	// including the shape in BC3's own "Update a schedule entry" doc example —
+	// silently removed every participant and notified each one. The controller
+	// now guards on the request actually addressing participants.
 	ParticipantIds []int64   `json:"participant_ids,omitempty"`
 	StartsAt       time.Time `json:"starts_at,omitempty"`
 	Summary        string    `json:"summary,omitempty"`
diff --git a/kotlin/conformance/src/main/kotlin/com/basecamp/sdk/conformance/Main.kt b/kotlin/conformance/src/main/kotlin/com/basecamp/sdk/conformance/Main.kt
index 675b0f3d3..c1da394e7 100644
--- a/kotlin/conformance/src/main/kotlin/com/basecamp/sdk/conformance/Main.kt
+++ b/kotlin/conformance/src/main/kotlin/com/basecamp/sdk/conformance/Main.kt
@@ -690,6 +690,20 @@ private suspend fun dispatchOperation(tc: TestCase, account: AccountClient): Dis
             DispatchResult()
         }
 
+        // Participants are presence-bearing: an absent key must not become an
+        // empty list on the wire, or BC3 clears the participants.
+        "UpdateScheduleEntry" -> {
+            val entryId = tc.pathParams.longParam("entryId")
+            val rb = tc.requestBody
+            account.schedules.updateEntry(entryId, UpdateScheduleEntryBody(
+                summary = rb?.get("summary")?.jsonPrimitive?.contentOrNull,
+                startsAt = rb?.get("starts_at")?.jsonPrimitive?.contentOrNull,
+                endsAt = rb?.get("ends_at")?.jsonPrimitive?.contentOrNull,
+                participantIds = rb?.get("participant_ids")?.jsonArray?.map { it.jsonPrimitive.long },
+            ))
+            DispatchResult()
+        }
+
         // Merge-safe composite: GET then PUT, resending the fetched due_on.
         "UpdateCard" -> {
             val cardId = tc.pathParams.longParam("cardId")
diff --git a/kotlin/sdk/src/commonMain/kotlin/com/basecamp/sdk/BasecampConfig.kt b/kotlin/sdk/src/commonMain/kotlin/com/basecamp/sdk/BasecampConfig.kt
index f1d1bfc01..f6198abf9 100644
--- a/kotlin/sdk/src/commonMain/kotlin/com/basecamp/sdk/BasecampConfig.kt
+++ b/kotlin/sdk/src/commonMain/kotlin/com/basecamp/sdk/BasecampConfig.kt
@@ -29,7 +29,7 @@ data class BasecampConfig(
 ) {
     companion object {
         const val VERSION = "0.9.0"
-        const val API_VERSION = "2026-07-26"
+        const val API_VERSION = "2026-07-28"
         const val DEFAULT_BASE_URL = "https://3.basecampapi.com"
         const val DEFAULT_USER_AGENT = "basecamp-sdk-kotlin/$VERSION (api:$API_VERSION)"
         const val DEFAULT_MAX_RETRIES = 3
diff --git a/openapi.json b/openapi.json
index 37f71dc66..c779765cd 100644
--- a/openapi.json
+++ b/openapi.json
@@ -2,7 +2,7 @@
   "openapi": "3.1.0",
   "info": {
     "title": "Basecamp",
-    "version": "2026-07-26",
+    "version": "2026-07-28",
     "description": "Basecamp API",
     "contact": {
       "name": "Basecamp",
@@ -31069,7 +31069,8 @@
             "items": {
               "type": "integer",
               "format": "int64"
-            }
+            },
+            "description": "Replaces the entry's participants.\n\nOmitting this member preserves the current participants; sending an empty\narray clears them. That guarantee is BC3-side and recent: until\nbasecamp/bc3#12425, `Schedules::EntriesController#update` called\n`replace_participants` unconditionally, so any update omitting the key —\nincluding the shape in BC3's own \"Update a schedule entry\" doc example —\nsilently removed every participant and notified each one. The controller\nnow guards on the request actually addressing participants."
           },
           "all_day": {
             "type": "boolean",
diff --git a/python/src/basecamp/_version.py b/python/src/basecamp/_version.py
index f0db63589..5985be1b4 100644
--- a/python/src/basecamp/_version.py
+++ b/python/src/basecamp/_version.py
@@ -1,2 +1,2 @@
 VERSION = "0.9.0"
-API_VERSION = "2026-07-26"
+API_VERSION = "2026-07-28"
diff --git a/ruby/lib/basecamp/generated/metadata.json b/ruby/lib/basecamp/generated/metadata.json
index 470b54131..e4b92c8cc 100644
--- a/ruby/lib/basecamp/generated/metadata.json
+++ b/ruby/lib/basecamp/generated/metadata.json
@@ -1,7 +1,7 @@
 {
   "$schema": "https://basecamp.com/schemas/sdk-metadata.json",
   "version": "1.0.0",
-  "generated": "2026-07-28T07:10:09Z",
+  "generated": "2026-07-28T21:34:14Z",
   "operations": {
     "GetAccount": {
       "retry": {
diff --git a/ruby/lib/basecamp/generated/services/schedules_service.rb b/ruby/lib/basecamp/generated/services/schedules_service.rb
index c9e77a000..6d81442bf 100644
--- a/ruby/lib/basecamp/generated/services/schedules_service.rb
+++ b/ruby/lib/basecamp/generated/services/schedules_service.rb
@@ -22,7 +22,15 @@ def get_entry(entry_id:)
       # @param starts_at [String, nil] starts at (RFC3339 (e.g., 2024-12-15T09:00:00Z))
       # @param ends_at [String, nil] ends at (RFC3339 (e.g., 2024-12-15T09:00:00Z))
       # @param description [String, nil] description
-      # @param participant_ids [Array, nil] participant ids
+      # @param participant_ids [Array, nil] Replaces the entry's participants.
+      #   
+      #   Omitting this member preserves the current participants; sending an empty
+      #   array clears them. That guarantee is BC3-side and recent: until
+      #   basecamp/bc3#12425, `Schedules::EntriesController#update` called
+      #   `replace_participants` unconditionally, so any update omitting the key —
+      #   including the shape in BC3's own "Update a schedule entry" doc example —
+      #   silently removed every participant and notified each one. The controller
+      #   now guards on the request actually addressing participants.
       # @param all_day [Boolean, nil] all day
       # @param notify [Boolean, nil] notify
       # @return [Hash] response data
diff --git a/ruby/lib/basecamp/generated/types.rb b/ruby/lib/basecamp/generated/types.rb
index 03757bc3b..ebea1db13 100644
--- a/ruby/lib/basecamp/generated/types.rb
+++ b/ruby/lib/basecamp/generated/types.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # Auto-generated from OpenAPI spec. Do not edit manually.
-# Generated: 2026-07-28T07:10:09Z
+# Generated: 2026-07-28T21:34:14Z
 
 require "json"
 require "time"
diff --git a/ruby/lib/basecamp/version.rb b/ruby/lib/basecamp/version.rb
index 72f4347de..a96aa3ee3 100644
--- a/ruby/lib/basecamp/version.rb
+++ b/ruby/lib/basecamp/version.rb
@@ -2,5 +2,5 @@
 
 module Basecamp
   VERSION = "0.9.0"
-  API_VERSION = "2026-07-26"
+  API_VERSION = "2026-07-28"
 end
diff --git a/spec/api-gaps/everything-tasks-aggregate.md b/spec/api-gaps/everything-tasks-aggregate.md
new file mode 100644
index 000000000..5a9f9bda8
--- /dev/null
+++ b/spec/api-gaps/everything-tasks-aggregate.md
@@ -0,0 +1,100 @@
+---
+gap: everything-tasks-aggregate
+status: confirmed-not-api-resource
+detected: 2026-07-28
+sdk_demand: none
+bc3_refs:
+  introduced_in: five
+  bc3_plan_section: "Not in API scope — web-only 'All tasks' page (bc3 e4bf93c3c2 + f697d8604d @ dffa7e11b3); HTML/Turbo Frame controllers, no respond_to :json, no jbuilder, no doc/api section"
+  routes:
+    - "GET /:account_id/tasks → everything/assignments#index (HTML only)"
+    - "GET /:account_id/tasks/results → everything/assignments/results#index (Turbo Frame, HTML only)"
+  controllers:
+    - "Everything::AssignmentsController"
+    - "Everything::Assignments::ResultsController"
+  related_existing_api:
+    - "GetEverythingOpenTodos / GetEverythingOverdueTodos / … (the modeled Everything JSON aggregates)"
+    - "GetMyAssignments / GetMyDueAssignments / GetMyCompletedAssignments (my/assignments.json — unchanged)"
+---
+
+# Everything "tasks" — a web view, not an API resource
+
+## What's missing
+
+Nothing. This entry exists to record a **negative** result, so the same routes
+don't get re-flagged at the next provenance sync.
+
+BC3 gained routes under the `scope module: :everything` block — the same block
+that produces the modeled `/todos/open.json` and `/cards/completed.json`:
+
+```ruby
+get "tasks" => "assignments#index", as: :assignments
+namespace :assignments, path: "tasks" do
+  get "results" => "results#index"
+end
+```
+
+Sitting in that block makes them *look* like siblings of the JSON aggregates.
+They are not. At the pinned `dffa7e11b3` both controllers are HTML-only:
+
+```ruby
+class Everything::AssignmentsController < ApplicationController
+  include Everything::Assignments::Filters
+  def index
+  end
+end
+
+class Everything::Assignments::ResultsController < ApplicationController
+  include Assignments::SlicedBuckets, Everything::Assignments::Filters
+  layout "turbo_rails/frame"
+  def index
+    @assignments = Everything::Assignments.new(Current.person, **assignment_filter_params)
+    @page = sliced_buckets @assignments.recordings, buckets: @assignments.sorted_buckets, viewer: Current.person
+  end
+end
+```
+
+- no `respond_to`, no JSON branch;
+- every view under `app/views/everything/assignments/` is `.html.erb`;
+- no `.json.jbuilder` template anywhere;
+- `results` declares `layout "turbo_rails/frame"` — it exists to serve a Turbo
+  Frame for the filter UI;
+- nothing in `doc/api/`.
+
+**A Rails route that tolerates a `.json` suffix does not create a JSON
+representation.** Requesting these with `.json` gets the HTML template or a
+missing-template error, not a payload.
+
+## Why it matters
+
+Only as a guard against a false positive. The provenance-drift triage from
+`c308693171` to `dffa7e11b3` surfaced two commits — `e4bf93c3c2` added
+`everything/assignments`, `f697d8604d` renamed it to `everything/tasks` — and
+the naming makes them read as an unmodeled API aggregate. They are the
+web-only "All tasks" page.
+
+**This is also not a break of `my/assignments`.** The commit subject "Move
+/assignments to /tasks" reads alarming against an SDK that ships
+`GetMyAssignments`, but the moved routes are the Everything ones. The SDK's
+assignment operations use `/:account_id/my/assignments.json` and its
+`completed`/`due` variants, which live under a different scope and are
+untouched across the whole drift range — `git diff c308693171..dffa7e11b3 --
+config/routes.rb` contains only the two `tasks` additions.
+
+## Suggested API shape
+
+None. Deliberately not proposed: there is no captured response to model, and
+sketching one would invite modeling a payload that does not exist. If an
+account-wide assignments JSON aggregate is ever wanted, it needs a BC3-side
+JSON representation first — at which point this entry should be reopened as a
+real gap with a shape read off an actual response.
+
+## Implementation notes for BC3
+
+None required. The routes serve the web UI as intended.
+
+## SDK absorption plan when this lands
+
+Not applicable — there is nothing to absorb. Reopen this entry only if BC3 adds
+a JSON representation for these controllers; until then the correct SDK action
+is to do nothing.
diff --git a/spec/api-provenance.json b/spec/api-provenance.json
index 83295cf85..b6ce27f98 100644
--- a/spec/api-provenance.json
+++ b/spec/api-provenance.json
@@ -1,8 +1,8 @@
 {
   "bc3": {
     "branch": "master",
-    "revision": "c308693171680e8ec9d3ae9e68181ef2ea80f077",
-    "date": "2026-07-26"
+    "revision": "dffa7e11b3337b17454d9a82301be3e94226a858",
+    "date": "2026-07-28"
   },
   "compatibility": {
     "bc3-four": {
diff --git a/spec/basecamp.smithy b/spec/basecamp.smithy
index c55a68634..70f39cc35 100644
--- a/spec/basecamp.smithy
+++ b/spec/basecamp.smithy
@@ -51,7 +51,7 @@ use basecamp.traits#basecampAuthRoutableUrl
 /// Basecamp API
 @restJson1
 service Basecamp {
-  version: "2026-07-26"
+  version: "2026-07-28"
   rename: {
     "smithy.api#Document": "JsonDocument"
   }
@@ -2718,6 +2718,15 @@ structure UpdateScheduleEntryInput {
   starts_at: ISO8601Timestamp
   ends_at: ISO8601Timestamp
   description: ScheduleEntryDescription
+  /// Replaces the entry's participants.
+  ///
+  /// Omitting this member preserves the current participants; sending an empty
+  /// array clears them. That guarantee is BC3-side and recent: until
+  /// basecamp/bc3#12425, `Schedules::EntriesController#update` called
+  /// `replace_participants` unconditionally, so any update omitting the key —
+  /// including the shape in BC3's own "Update a schedule entry" doc example —
+  /// silently removed every participant and notified each one. The controller
+  /// now guards on the request actually addressing participants.
   participant_ids: PersonIdList
   all_day: Boolean
   notify: Boolean
diff --git a/swift/Sources/Basecamp/BasecampConfig.swift b/swift/Sources/Basecamp/BasecampConfig.swift
index 48ffe464e..7ce0d3897 100644
--- a/swift/Sources/Basecamp/BasecampConfig.swift
+++ b/swift/Sources/Basecamp/BasecampConfig.swift
@@ -27,7 +27,7 @@ public struct BasecampConfig: Sendable {
     public static let version = "0.9.0"
 
     /// Basecamp API version this SDK targets.
-    public static let apiVersion = "2026-07-26"
+    public static let apiVersion = "2026-07-28"
 
     /// Default User-Agent header value.
     public static let defaultUserAgent = "basecamp-sdk-swift/\(version) (api:\(apiVersion))"
diff --git a/swift/Tests/BasecampTests/ScheduleEntryParticipantsTests.swift b/swift/Tests/BasecampTests/ScheduleEntryParticipantsTests.swift
new file mode 100644
index 000000000..017f380bc
--- /dev/null
+++ b/swift/Tests/BasecampTests/ScheduleEntryParticipantsTests.swift
@@ -0,0 +1,141 @@
+import XCTest
+@testable import Basecamp
+
+/// Swift mirror of `conformance/tests/schedule_entries_write.json`.
+///
+/// Swift is not part of `make conformance`, so these carry the same two
+/// assertions the five executable runners make.
+///
+/// The contract is BC3-side and recent. Until basecamp/bc3#12425,
+/// `Schedules::EntriesController#update` called `replace_participants`
+/// unconditionally, so an update omitting `participant_ids` removed every
+/// participant and notified each one — including the shape in BC3's own
+/// "Update a schedule entry" doc example. The controller now guards on the
+/// request actually addressing participants, which makes the SDK's job narrow
+/// but load-bearing: an unaddressed list must stay *off the wire entirely*.
+/// Emitting `null`, or defaulting to `[]`, would clear it on the server.
+private final class ScheduleRequestLog: @unchecked Sendable {
+    private let lock = NSLock()
+    private var _putBody: [String: Any]?
+
+    var putBody: [String: Any]? { lock.withLock { _putBody } }
+
+    func record(_ request: URLRequest) {
+        guard request.httpMethod == "PUT" else { return }
+        lock.withLock {
+            if let data = request.httpBody ?? request.scheduleBodyStreamData() {
+                _putBody = (try? JSONSerialization.jsonObject(with: data)) as? [String: Any]
+            }
+        }
+    }
+}
+
+extension URLRequest {
+    fileprivate func scheduleBodyStreamData() -> Data? {
+        guard let stream = httpBodyStream else { return nil }
+        stream.open()
+        defer { stream.close() }
+        var data = Data()
+        let bufferSize = 4096
+        let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
+        defer { buffer.deallocate() }
+        while stream.hasBytesAvailable {
+            let read = stream.read(buffer, maxLength: bufferSize)
+            if read <= 0 { break }
+            data.append(buffer, count: read)
+        }
+        return data
+    }
+}
+
+private func scheduleEntryJSON(id: Int = 1069479523) -> [String: Any] {
+    [
+        "id": id,
+        "status": "active",
+        "visible_to_clients": false,
+        "created_at": "2026-01-01T00:00:00Z",
+        "updated_at": "2026-01-01T00:00:00Z",
+        "title": "Team Meeting",
+        "inherits_status": true,
+        "type": "Schedule::Entry",
+        "url": "https://3.basecampapi.com/999/buckets/1/schedule_entries/\(id).json",
+        "app_url": "https://3.basecamp.com/999/buckets/1/schedule_entries/\(id)",
+        "summary": "Team Meeting",
+        "all_day": false,
+        "starts_at": "2026-06-05T06:00:00Z",
+        "ends_at": "2026-06-05T08:30:00Z",
+        "description_attachments": [] as [Any],
+        "participants": [
+            ["id": 1049715914, "name": "Victor Cooper"],
+            ["id": 1049715915, "name": "Annie Bryan"],
+        ],
+        "parent": [
+            "id": 1069479521,
+            "title": "Schedule",
+            "type": "Schedule",
+            "url": "https://3.basecampapi.com/999/buckets/1/schedules/1069479521.json",
+            "app_url": "https://3.basecamp.com/999/buckets/1/schedules/1069479521",
+        ],
+        "bucket": ["id": 1, "name": "The Leto Laptop", "type": "Project"],
+        "creator": [
+            "id": 1049715914,
+            "name": "Victor Cooper",
+            "email_address": "victor@honchodesign.com",
+            "created_at": "2026-01-01T00:00:00Z",
+            "updated_at": "2026-01-01T00:00:00Z",
+        ],
+    ]
+}
+
+final class ScheduleEntryParticipantsTests: XCTestCase {
+    private func makeClient(log: ScheduleRequestLog) throws -> AccountClient {
+        let data = try JSONSerialization.data(withJSONObject: scheduleEntryJSON())
+        let transport = MockTransport { request in
+            log.record(request)
+            return (
+                data,
+                makeHTTPResponse(
+                    url: request.url!.absoluteString,
+                    statusCode: 200,
+                    headers: ["Content-Type": "application/json"]
+                )
+            )
+        }
+        return makeTestAccountClient(transport: transport)
+    }
+
+    func testOmittedParticipantIdsStayOffTheWire() async throws {
+        let log = ScheduleRequestLog()
+        let account = try makeClient(log: log)
+
+        _ = try await account.schedules.updateEntry(
+            entryId: 1069479523,
+            req: UpdateScheduleEntryRequest(summary: "Team Meeting")
+        )
+
+        let body = try XCTUnwrap(log.putBody)
+        XCTAssertEqual(body["summary"] as? String, "Team Meeting")
+        XCTAssertNil(
+            body["participant_ids"],
+            "an unaddressed participant list must not reach the wire — BC3 preserves participants only because the key is absent"
+        )
+        XCTAssertFalse(body.keys.contains("participant_ids"))
+    }
+
+    func testExplicitEmptyParticipantIdsReachTheWire() async throws {
+        let log = ScheduleRequestLog()
+        let account = try makeClient(log: log)
+
+        _ = try await account.schedules.updateEntry(
+            entryId: 1069479523,
+            req: UpdateScheduleEntryRequest(participantIds: [], summary: "Team Meeting")
+        )
+
+        let body = try XCTUnwrap(log.putBody)
+        let ids = try XCTUnwrap(
+            body["participant_ids"] as? [Any],
+            "an explicitly empty list means 'remove everyone' and must be sent"
+        )
+        XCTAssertTrue(ids.isEmpty)
+    }
+}
diff --git a/typescript/src/client.ts b/typescript/src/client.ts
index d44965d05..676afd8f5 100644
--- a/typescript/src/client.ts
+++ b/typescript/src/client.ts
@@ -233,7 +233,7 @@ export interface BasecampClientOptions {
 }
 
 export const VERSION = "0.9.0";
-export const API_VERSION = "2026-07-26";
+export const API_VERSION = "2026-07-28";
 const DEFAULT_USER_AGENT = `basecamp-sdk-ts/${VERSION} (api:${API_VERSION})`;
 
 /**
diff --git a/typescript/src/generated/metadata.ts b/typescript/src/generated/metadata.ts
index 682354f42..819575b7e 100644
--- a/typescript/src/generated/metadata.ts
+++ b/typescript/src/generated/metadata.ts
@@ -37,7 +37,7 @@ export interface MetadataOutput {
 const metadata: MetadataOutput = {
   "$schema": "https://basecamp.com/schemas/sdk-metadata.json",
   "version": "1.0.0",
-  "generated": "2026-07-28T07:10:08.052Z",
+  "generated": "2026-07-28T21:34:13.284Z",
   "operations": {
     "GetAccount": {
       "retry": {
diff --git a/typescript/src/generated/openapi-stripped.json b/typescript/src/generated/openapi-stripped.json
index 13d9cf347..502d0d67f 100644
--- a/typescript/src/generated/openapi-stripped.json
+++ b/typescript/src/generated/openapi-stripped.json
@@ -2,7 +2,7 @@
   "openapi": "3.1.0",
   "info": {
     "title": "Basecamp",
-    "version": "2026-07-26",
+    "version": "2026-07-28",
     "description": "Basecamp API",
     "contact": {
       "name": "Basecamp",
@@ -28493,7 +28493,8 @@
             "items": {
               "type": "integer",
               "format": "int64"
-            }
+            },
+            "description": "Replaces the entry's participants.\n\nOmitting this member preserves the current participants; sending an empty\narray clears them. That guarantee is BC3-side and recent: until\nbasecamp/bc3#12425, `Schedules::EntriesController#update` called\n`replace_participants` unconditionally, so any update omitting the key —\nincluding the shape in BC3's own \"Update a schedule entry\" doc example —\nsilently removed every participant and notified each one. The controller\nnow guards on the request actually addressing participants."
           },
           "all_day": {
             "type": "boolean",
diff --git a/typescript/src/generated/schema.d.ts b/typescript/src/generated/schema.d.ts
index 731eca8fd..2ed943328 100644
--- a/typescript/src/generated/schema.d.ts
+++ b/typescript/src/generated/schema.d.ts
@@ -5382,6 +5382,17 @@ export interface components {
             starts_at?: string;
             ends_at?: string;
             description?: string;
+            /**
+             * @description Replaces the entry's participants.
+             *
+             *     Omitting this member preserves the current participants; sending an empty
+             *     array clears them. That guarantee is BC3-side and recent: until
+             *     basecamp/bc3#12425, `Schedules::EntriesController#update` called
+             *     `replace_participants` unconditionally, so any update omitting the key —
+             *     including the shape in BC3's own "Update a schedule entry" doc example —
+             *     silently removed every participant and notified each one. The controller
+             *     now guards on the request actually addressing participants.
+             */
             participant_ids?: number[];
             all_day?: boolean;
             notify?: boolean;
diff --git a/typescript/src/generated/services/schedules.ts b/typescript/src/generated/services/schedules.ts
index 3b464cff2..a4c293b6d 100644
--- a/typescript/src/generated/services/schedules.ts
+++ b/typescript/src/generated/services/schedules.ts
@@ -31,7 +31,15 @@ export interface UpdateEntryScheduleRequest {
   endsAt?: string;
   /** Rich text description (HTML) */
   description?: string;
-  /** Participant ids */
+  /** Replaces the entry's participants.
+
+Omitting this member preserves the current participants; sending an empty
+array clears them. That guarantee is BC3-side and recent: until
+basecamp/bc3#12425, `Schedules::EntriesController#update` called
+`replace_participants` unconditionally, so any update omitting the key —
+including the shape in BC3's own "Update a schedule entry" doc example —
+silently removed every participant and notified each one. The controller
+now guards on the request actually addressing participants. */
   participantIds?: number[];
   /** All day */
   allDay?: boolean;