diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/index.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/index.ts
index f1c7cb73d..556994ed7 100644
--- a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/index.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/index.ts
@@ -1,3 +1,5 @@
 export * from './io-host';
 export * from './io-message';
 export * from './toolkit-action';
+export * from './payloads';
+export * from './messages';
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/io-message.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/io-message.ts
index 6a6855118..19c896580 100644
--- a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/io-message.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/io-message.ts
@@ -62,7 +62,7 @@ export interface IoMessage<T> {
   /**
    * The data attached to the message.
    */
-  readonly data?: T;
+  readonly data: T;
 }
 
 /**
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/messages.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/messages.ts
similarity index 92%
rename from packages/@aws-cdk/toolkit-lib/lib/api/io/private/messages.ts
rename to packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/messages.ts
index caca8d5ea..ff52fa60c 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/messages.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/messages.ts
@@ -1,15 +1,15 @@
 import type * as cxapi from '@aws-cdk/cx-api';
-import type { SdkTrace } from '../';
-import type { BootstrapEnvironmentProgress } from '../../../actions/bootstrap';
-import type { DeployConfirmationRequest, StackDeployProgress } from '../../../actions/deploy';
-import type { StackDestroyProgress } from '../../../actions/destroy';
-import type { StackDetailsPayload } from '../../../actions/list';
-import type { StackRollbackProgress } from '../../../actions/rollback';
-import type { FileWatchEvent, WatchSettings } from '../../../actions/watch';
-import type { AssemblyData, ConfirmationRequest, Duration, ErrorPayload, StackAndAssemblyData, SuccessfulDeployStackResult } from '../../../toolkit/types';
-import type { StackActivity, StackMonitoringControlEvent } from '../../aws-cdk';
-import type { MissingContext, UpdatedContext } from '../../cloud-assembly/context';
-import * as make from '../../shared-private';
+import type { BootstrapEnvironmentProgress } from './payloads/bootstrap-environment-progress';
+import type { MissingContext, UpdatedContext } from './payloads/context';
+import type { DeployConfirmationRequest, StackDeployProgress, SuccessfulDeployStackResult } from './payloads/deploy';
+import type { StackDestroyProgress } from './payloads/destroy';
+import type { StackDetailsPayload } from './payloads/list';
+import type { StackRollbackProgress } from './payloads/rollback';
+import type { SdkTrace } from './payloads/sdk-trace';
+import type { StackActivity, StackMonitoringControlEvent } from './payloads/stack-activity';
+import type { AssemblyData, ConfirmationRequest, Duration, ErrorPayload, StackAndAssemblyData } from './payloads/types';
+import type { FileWatchEvent, WatchSettings } from './payloads/watch';
+import * as make from './private';
 
 /**
  * We have a rough system by which we assign message codes:
@@ -328,6 +328,10 @@ export const IO = {
   }),
 
   // SDK codes
+  CDK_SDK_I0000: make.trace({
+    code: 'CDK_SDK_I0000',
+    description: 'An SDK message.',
+  }),
   CDK_SDK_I0100: make.trace<SdkTrace>({
     code: 'CDK_SDK_I0100',
     description: 'An SDK trace. SDK traces are emitted as traces to the IoHost, but contain the original SDK logging level.',
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/bootstrap-environment-progress.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/bootstrap-environment-progress.ts
new file mode 100644
index 000000000..6f77c897d
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/bootstrap-environment-progress.ts
@@ -0,0 +1,18 @@
+import type * as cxapi from '@aws-cdk/cx-api';
+
+export interface BootstrapEnvironmentProgress {
+  /**
+   * The total number of environments being deployed
+   */
+  readonly total: number;
+  /**
+   * The count of the environment currently bootstrapped
+   *
+   * This is counting value, not an identifier.
+   */
+  readonly current: number;
+  /**
+   * The environment that's currently being bootstrapped
+   */
+  readonly environment: cxapi.Environment;
+}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/context.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/context.ts
similarity index 100%
rename from packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/context.ts
rename to packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/context.ts
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/deploy.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/deploy.ts
new file mode 100644
index 000000000..b3b7bf364
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/deploy.ts
@@ -0,0 +1,57 @@
+import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
+import type { PermissionChangeType } from './diff';
+import type { ConfirmationRequest } from './types';
+
+export interface StackDeployProgress {
+  /**
+   * The total number of stacks being deployed
+   */
+  readonly total: number;
+  /**
+   * The count of the stack currently attempted to be deployed
+   *
+   * This is counting value, not an identifier.
+   */
+  readonly current: number;
+  /**
+   * The stack that's currently being deployed
+   */
+  readonly stack: CloudFormationStackArtifact;
+}
+
+/**
+ * Payload for a yes/no confirmation in deploy. Includes information on
+ * what kind of change is being made.
+ */
+export interface DeployConfirmationRequest extends ConfirmationRequest {
+  /**
+   * The type of change being made to the IAM permissions.
+   */
+  readonly permissionChangeType: PermissionChangeType;
+}
+
+export type DeployStackResult =
+  | SuccessfulDeployStackResult
+  | NeedRollbackFirstDeployStackResult
+  | ReplacementRequiresRollbackStackResult
+  ;
+
+/** Successfully deployed a stack */
+export interface SuccessfulDeployStackResult {
+  readonly type: 'did-deploy-stack';
+  readonly noOp: boolean;
+  readonly outputs: { [name: string]: string };
+  readonly stackArn: string;
+}
+
+/** The stack is currently in a failpaused state, and needs to be rolled back before the deployment */
+export interface NeedRollbackFirstDeployStackResult {
+  readonly type: 'failpaused-need-rollback-first';
+  readonly reason: 'not-norollback' | 'replacement';
+  readonly status: string;
+}
+
+/** The upcoming change has a replacement, which requires deploying with --rollback */
+export interface ReplacementRequiresRollbackStackResult {
+  readonly type: 'replacement-requires-rollback';
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/destroy.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/destroy.ts
new file mode 100644
index 000000000..3aa0eb328
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/destroy.ts
@@ -0,0 +1,18 @@
+import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
+
+export interface StackDestroyProgress {
+  /**
+   * The total number of stacks being destroyed
+   */
+  readonly total: number;
+  /**
+   * The count of the stack currently attempted to be destroyed
+   *
+   * This is counting value, not an identifier.
+   */
+  readonly current: number;
+  /**
+   * The stack that's currently being destroyed
+   */
+  readonly stack: CloudFormationStackArtifact;
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/diff.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/diff.ts
new file mode 100644
index 000000000..82ab65432
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/diff.ts
@@ -0,0 +1,19 @@
+/**
+ * Different types of permission related changes in a diff
+ */
+export enum PermissionChangeType {
+  /**
+   * No permission changes
+   */
+  NONE = 'none',
+
+  /**
+   * Permissions are broadening
+   */
+  BROADENING = 'broadening',
+
+  /**
+   * Permissions are changed but not broadening
+   */
+  NON_BROADENING = 'non-broadening',
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/index.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/index.ts
new file mode 100644
index 000000000..ec206a970
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/index.ts
@@ -0,0 +1,13 @@
+export * from './bootstrap-environment-progress';
+export * from './deploy';
+export * from './destroy';
+export * from './list';
+export * from './sdk-trace';
+export * from './context';
+export * from './rollback';
+export * from './stack-activity';
+export * from './types';
+export * from './progress';
+export * from './watch';
+export * from './stack-details';
+export * from './diff';
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/list.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/list.ts
new file mode 100644
index 000000000..47cfbd200
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/list.ts
@@ -0,0 +1,5 @@
+import type { StackDetails } from './stack-details';
+
+export interface StackDetailsPayload {
+  stacks: StackDetails[];
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/progress.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/progress.ts
new file mode 100644
index 000000000..768d8754c
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/progress.ts
@@ -0,0 +1,17 @@
+export interface StackProgress {
+  /**
+   * The total number of progress monitored resources.
+   */
+  readonly total?: number;
+
+  /**
+   * The number of completed resources.
+   */
+  readonly completed: number;
+
+  /**
+   * The current progress as a [34/42] string, or just [34] if the total is unknown.
+   */
+  readonly formatted: string;
+}
+
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/rollback.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/rollback.ts
new file mode 100644
index 000000000..1a97bd1d7
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/rollback.ts
@@ -0,0 +1,18 @@
+import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
+
+export interface StackRollbackProgress {
+  /**
+   * The total number of stacks being rolled back
+   */
+  readonly total: number;
+  /**
+   * The count of the stack currently attempted to be rolled back
+   *
+   * This is counting value, not an identifier.
+   */
+  readonly current: number;
+  /**
+   * The stack that's currently being rolled back
+   */
+  readonly stack: CloudFormationStackArtifact;
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/sdk-trace.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/sdk-trace.ts
new file mode 100644
index 000000000..fa5bf15c6
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/sdk-trace.ts
@@ -0,0 +1,21 @@
+/**
+ * An SDK logging trace.
+ *
+ * Only info, warn and error level messages are emitted.
+ * SDK traces are emitted as traces to the IoHost, but contain the original SDK logging level.
+ */
+export interface SdkTrace {
+  /**
+   * The level the SDK has emitted the original message with
+   */
+  readonly sdkLevel: 'info' | 'warn' | 'error';
+
+  /**
+   * The content of the SDK trace
+   *
+   * This will include the request and response data for API calls, including potentially sensitive information.
+   *
+   * @see https://docs.aws.amazon.com/sdk-for-javascript/v3/developer-guide/logging-sdk-calls.html
+   */
+  readonly content: any;
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-activity.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-activity.ts
new file mode 100644
index 000000000..1740601ce
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-activity.ts
@@ -0,0 +1,63 @@
+import { type MetadataEntry } from '@aws-cdk/cloud-assembly-schema';
+import { type CloudFormationStackArtifact } from '@aws-cdk/cx-api';
+import type { StackEvent } from '@aws-sdk/client-cloudformation';
+import type { StackProgress } from './progress';
+
+/**
+ * Payload when stack monitoring is starting or stopping for a given stack deployment.
+ */
+export interface StackMonitoringControlEvent {
+  /**
+   * A unique identifier for a specific stack deployment.
+   *
+   * Use this value to attribute stack activities received for concurrent deployments.
+   */
+  readonly deployment: string;
+
+  /**
+   * The stack artifact that is getting deployed
+   */
+  readonly stack: CloudFormationStackArtifact;
+
+  /**
+   * The name of the Stack that is getting deployed
+   */
+  readonly stackName: string;
+
+  /**
+   * Total number of resources taking part in this deployment
+   *
+   * The number might not always be known or accurate.
+   * Only use for informational purposes and handle the case when it's unavailable.
+   */
+  readonly resourcesTotal?: number;
+}
+
+export interface StackActivity {
+  /**
+   * A unique identifier for a specific stack deployment.
+   *
+   * Use this value to attribute stack activities received for concurrent deployments.
+   */
+  readonly deployment: string;
+
+  /**
+   * The Stack Event as received from CloudFormation
+   */
+  readonly event: StackEvent;
+
+  /**
+   * Additional resource metadata
+   */
+  readonly metadata?: ResourceMetadata;
+
+  /**
+   * The stack progress
+   */
+  readonly progress: StackProgress;
+}
+
+export interface ResourceMetadata {
+  entry: MetadataEntry;
+  constructPath: string;
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-details.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-details.ts
new file mode 100644
index 000000000..31d995755
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/stack-details.ts
@@ -0,0 +1,20 @@
+import type * as cxapi from '@aws-cdk/cx-api';
+
+/**
+ * The dependencies of a stack.
+ */
+export interface StackDependency {
+  id: string;
+  dependencies: StackDependency[];
+}
+
+/**
+ * Details of a stack.
+ */
+export interface StackDetails {
+  id: string;
+  name: string;
+  environment: cxapi.Environment;
+  dependencies: StackDependency[];
+}
+
diff --git a/packages/@aws-cdk/toolkit-lib/lib/toolkit/types.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/types.ts
similarity index 86%
rename from packages/@aws-cdk/toolkit-lib/lib/toolkit/types.ts
rename to packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/types.ts
index 4c29336a4..909caef8a 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/toolkit/types.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/types.ts
@@ -1,5 +1,3 @@
-import type { SuccessfulDeployStackResult as _SuccessfulDeployStackResult } from '../api/aws-cdk';
-
 /**
  * Assembly data returned in the payload of an IO Message.
  */
@@ -20,13 +18,6 @@ export interface AssemblyData {
   readonly stackIds: string[];
 }
 
-/**
- * A successful deploy stack result. Intentionally exposed in toolkit-lib so documentation
- * can be generated from this interface.
- */
-export interface SuccessfulDeployStackResult extends _SuccessfulDeployStackResult {
-}
-
 /**
  * Stack data returned in the payload of an IO Message.
  */
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/watch.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/watch.ts
new file mode 100644
index 000000000..efcdab095
--- /dev/null
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/payloads/watch.ts
@@ -0,0 +1,29 @@
+
+/**
+ * The computed file watch settings
+ */
+export interface WatchSettings {
+  /**
+   * The directory observed for file changes
+   */
+  readonly watchDir: string;
+  /**
+   * List of include patterns for watching files
+   */
+  readonly includes: string[];
+  /**
+   * List of excludes patterns for watching files
+   */
+  readonly excludes: string[];
+}
+
+export interface FileWatchEvent {
+  /**
+   * The change to the path
+   */
+  readonly event: string;
+  /**
+   * The path that has an observed event
+   */
+  readonly path?: string;
+}
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/io-helper.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/io-helper.ts
index 2a1da3fe3..e1ded895f 100644
--- a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/io-helper.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/io-helper.ts
@@ -14,6 +14,7 @@ export type ActionLessRequest<T, U> = Omit<IoRequest<T, U>, 'action'>;
  */
 export interface IoHelper extends IIoHost {
   notify(msg: ActionLessMessage<unknown>): Promise<void>;
+  notify<T>(msg: ActionLessMessage<T>): Promise<void>;
   requestResponse<T, U>(msg: ActionLessRequest<T, U>): Promise<U>;
 }
 
diff --git a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/message-maker.ts b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/message-maker.ts
index 57994219d..ddf23d461 100644
--- a/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/message-maker.ts
+++ b/packages/@aws-cdk/tmp-toolkit-helpers/src/api/io/private/message-maker.ts
@@ -1,4 +1,4 @@
-import type { IoMessageCode, IoMessageLevel } from '../io-message';
+import type { IoMessage, IoMessageCode, IoMessageLevel } from '../io-message';
 import type { ActionLessMessage, ActionLessRequest } from './io-helper';
 
 /**
@@ -44,13 +44,18 @@ export interface IoMessageMaker<T> extends MessageInfo {
   /**
    * Create a message for this code, with or without payload.
    */
-  msg: [T] extends [never] ? (message: string) => ActionLessMessage<never> : (message: string, data: T) => ActionLessMessage<T>;
+  msg: [T] extends [AbsentData] ? (message: string) => ActionLessMessage<AbsentData> : (message: string, data: T) => ActionLessMessage<T>;
+
+  /**
+   * Returns whether the given `IoMessage` instance matches the current message definition
+   */
+  is(x: IoMessage<unknown>): x is IoMessage<T>;
 }
 
 /**
  * Produce an IoMessageMaker for the provided level and code info.
  */
-function message<T = never>(level: IoMessageLevel, details: CodeInfo): IoMessageMaker<T> {
+function message<T = AbsentData>(level: IoMessageLevel, details: CodeInfo): IoMessageMaker<T> {
   const maker = (text: string, data: T) => ({
     time: new Date(),
     level,
@@ -63,6 +68,7 @@ function message<T = never>(level: IoMessageLevel, details: CodeInfo): IoMessage
     ...details,
     level,
     msg: maker as any,
+    is: (m): m is IoMessage<T> => m.code === details.code,
   };
 }
 
@@ -76,14 +82,25 @@ export type ImpossibleType = {
 };
 
 // Create `IoMessageMaker`s for a given level and type check that calls with payload are using the correct interface
-type CodeInfoMaybeInterface<T> = [T] extends [never] ? Omit<CodeInfo, 'interface'> : Required<CodeInfo>;
+type CodeInfoMaybeInterface<T> = [T] extends [AbsentData] ? Omit<CodeInfo, 'interface'> : Required<CodeInfo>;
+
+/**
+ * The type we use to represent an absent data field
+ *
+ * This is here to make it easy to change between `undefined`, `void`
+ * and `never`.
+ *
+ * Not a lot of difference between `undefined` and `void`, but `void`
+ * reads better.
+ */
+type AbsentData = void;
 
-export const trace = <T = never>(details: CodeInfoMaybeInterface<T>) => message<T>('trace', details);
-export const debug = <T = never>(details: CodeInfoMaybeInterface<T>) => message<T>('debug', details);
-export const info = <T = never>(details: CodeInfoMaybeInterface<T>) => message<T>('info', details);
-export const warn = <T = never>(details: CodeInfoMaybeInterface<T>) => message<T>('warn', details);
-export const error = <T = never>(details: CodeInfoMaybeInterface<T>) => message<T>('error', details);
-export const result = <T extends object = ImpossibleType>(details: Required<CodeInfo>) => message<T extends object ? T : never>('result', details);
+export const trace = <T = AbsentData>(details: CodeInfoMaybeInterface<T>) => message<T>('trace', details);
+export const debug = <T = AbsentData>(details: CodeInfoMaybeInterface<T>) => message<T>('debug', details);
+export const info = <T = AbsentData>(details: CodeInfoMaybeInterface<T>) => message<T>('info', details);
+export const warn = <T = AbsentData>(details: CodeInfoMaybeInterface<T>) => message<T>('warn', details);
+export const error = <T = AbsentData>(details: CodeInfoMaybeInterface<T>) => message<T>('error', details);
+export const result = <T extends object = ImpossibleType>(details: Required<CodeInfo>) => message<T extends object ? T : undefined>('result', details);
 
 interface RequestInfo<U> extends CodeInfo {
   readonly defaultResponse: U;
@@ -96,13 +113,13 @@ export interface IoRequestMaker<T, U> extends MessageInfo {
   /**
    * Create a message for this code, with or without payload.
    */
-  req: [T] extends [never] ? (message: string) => ActionLessMessage<never> : (message: string, data: T) => ActionLessRequest<T, U>;
+  req: [T] extends [AbsentData] ? (message: string) => ActionLessMessage<AbsentData> : (message: string, data: T) => ActionLessRequest<T, U>;
 }
 
 /**
  * Produce an IoRequestMaker for the provided level and request info.
  */
-function request<T = never, U = ImpossibleType>(level: IoMessageLevel, details: RequestInfo<U>): IoRequestMaker<T, U> {
+function request<T = AbsentData, U = ImpossibleType>(level: IoMessageLevel, details: RequestInfo<U>): IoRequestMaker<T, U> {
   const maker = (text: string, data: T) => ({
     time: new Date(),
     level,
diff --git a/packages/@aws-cdk/toolkit-lib/docs/message-registry.md b/packages/@aws-cdk/toolkit-lib/docs/message-registry.md
index 51f118f49..90b756295 100644
--- a/packages/@aws-cdk/toolkit-lib/docs/message-registry.md
+++ b/packages/@aws-cdk/toolkit-lib/docs/message-registry.md
@@ -65,4 +65,5 @@ group: Documents
 | `CDK_ASSEMBLY_I9999` | Annotations emitted by the cloud assembly | `info` | [cxapi.SynthesisMessage](https://docs.aws.amazon.com/cdk/api/v2/docs/@aws-cdk_cx-api.SynthesisMessage.html) |
 | `CDK_ASSEMBLY_W9999` | Warnings emitted by the cloud assembly | `warn` | [cxapi.SynthesisMessage](https://docs.aws.amazon.com/cdk/api/v2/docs/@aws-cdk_cx-api.SynthesisMessage.html) |
 | `CDK_ASSEMBLY_E9999` | Errors emitted by the cloud assembly | `error` | [cxapi.SynthesisMessage](https://docs.aws.amazon.com/cdk/api/v2/docs/@aws-cdk_cx-api.SynthesisMessage.html) |
+| `CDK_SDK_I0000` | An SDK message. | `trace` | n/a |
 | `CDK_SDK_I0100` | An SDK trace. SDK traces are emitted as traces to the IoHost, but contain the original SDK logging level. | `trace` | {@link SdkTrace} |
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/bootstrap/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/bootstrap/index.ts
index 9ee31fc42..951eb95dd 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/bootstrap/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/bootstrap/index.ts
@@ -227,20 +227,3 @@ export class BootstrapSource {
     };
   }
 }
-
-export interface BootstrapEnvironmentProgress {
-  /**
-   * The total number of environments being deployed
-   */
-  readonly total: number;
-  /**
-   * The count of the environment currently bootstrapped
-   *
-   * This is counting value, not an identifier.
-   */
-  readonly current: number;
-  /**
-   * The environment that's currently being bootstrapped
-   */
-  readonly environment: cxapi.Environment;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/deploy/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/deploy/index.ts
index ad278d47f..cb909dc20 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/deploy/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/deploy/index.ts
@@ -1,10 +1,5 @@
-import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
 import type { BaseDeployOptions } from './private/deploy-options';
 import type { Tag } from '../../api/aws-cdk';
-import type { ConfirmationRequest } from '../../toolkit/types';
-import type { PermissionChangeType } from '../diff';
-
-export type { StackMonitoringControlEvent, StackActivity } from '../../api/aws-cdk';
 
 export type DeploymentMethod = DirectDeploymentMethod | ChangeSetDeploymentMethod;
 
@@ -217,31 +212,3 @@ export interface HotswapProperties {
    */
   readonly ecs: EcsHotswapProperties;
 }
-
-export interface StackDeployProgress {
-  /**
-   * The total number of stacks being deployed
-   */
-  readonly total: number;
-  /**
-   * The count of the stack currently attempted to be deployed
-   *
-   * This is counting value, not an identifier.
-   */
-  readonly current: number;
-  /**
-   * The stack that's currently being deployed
-   */
-  readonly stack: CloudFormationStackArtifact;
-}
-
-/**
- * Payload for a yes/no confirmation in deploy. Includes information on
- * what kind of change is being made.
- */
-export interface DeployConfirmationRequest extends ConfirmationRequest {
-  /**
-   * The type of change being made to the IAM permissions.
-   */
-  readonly permissionChangeType: PermissionChangeType;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/destroy/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/destroy/index.ts
index ce6f90226..3a9862048 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/destroy/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/destroy/index.ts
@@ -1,4 +1,3 @@
-import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
 import type { StackSelector } from '../../api/cloud-assembly';
 
 export interface DestroyOptions {
@@ -19,20 +18,3 @@ export interface DestroyOptions {
    */
   readonly ci?: boolean;
 }
-
-export interface StackDestroyProgress {
-  /**
-   * The total number of stacks being destroyed
-   */
-  readonly total: number;
-  /**
-   * The count of the stack currently attempted to be destroyed
-   *
-   * This is counting value, not an identifier.
-   */
-  readonly current: number;
-  /**
-   * The stack that's currently being destroyed
-   */
-  readonly stack: CloudFormationStackArtifact;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/diff/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/diff/index.ts
index bbe1e7261..327a200ec 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/diff/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/diff/index.ts
@@ -115,23 +115,3 @@ export interface DiffOptions {
    */
   readonly securityOnly?: boolean;
 }
-
-/**
- * Different types of permission related changes in a diff
- */
-export enum PermissionChangeType {
-  /**
-   * No permission changes
-   */
-  NONE = 'none',
-
-  /**
-   * Permissions are broadening
-   */
-  BROADENING = 'broadening',
-
-  /**
-   * Permissions are changed but not broadening
-   */
-  NON_BROADENING = 'non-broadening',
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/diff/private/helpers.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/diff/private/helpers.ts
index 790d9a171..4917ce1b2 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/diff/private/helpers.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/diff/private/helpers.ts
@@ -1,7 +1,7 @@
 import type { DescribeChangeSetOutput } from '@aws-cdk/cloudformation-diff';
 import { fullDiff } from '@aws-cdk/cloudformation-diff';
 import type * as cxapi from '@aws-cdk/cx-api';
-import { PermissionChangeType } from '..';
+import { PermissionChangeType } from '../../../api/shared-public';
 
 /**
  * Return whether the diff has security-impacting changes that need confirmation.
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/index.ts
index 1e86ec265..add78a1be 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/index.ts
@@ -1,7 +1,6 @@
 export * from './bootstrap';
 export * from './deploy';
 export * from './destroy';
-export { PermissionChangeType } from './diff';
 export * from './list';
 export * from './rollback';
 export * from './synth';
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/list/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/list/index.ts
index 6f96efe60..2882b9739 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/list/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/list/index.ts
@@ -1,4 +1,3 @@
-import type { StackDetails } from '../../api/aws-cdk';
 import type { StackSelector } from '../../api/cloud-assembly';
 
 export interface ListOptions {
@@ -7,7 +6,3 @@ export interface ListOptions {
    */
   readonly stacks?: StackSelector;
 }
-
-export interface StackDetailsPayload {
-  stacks: StackDetails[];
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/rollback/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/rollback/index.ts
index ef38edaf6..7f5f8e5ae 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/rollback/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/rollback/index.ts
@@ -1,4 +1,3 @@
-import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
 import type { StackSelector } from '../../api/cloud-assembly';
 
 export interface RollbackOptions {
@@ -43,20 +42,3 @@ export interface RollbackOptions {
    */
   readonly validateBootstrapStackVersion?: boolean;
 }
-
-export interface StackRollbackProgress {
-  /**
-   * The total number of stacks being rolled back
-   */
-  readonly total: number;
-  /**
-   * The count of the stack currently attempted to be rolled back
-   *
-   * This is counting value, not an identifier.
-   */
-  readonly current: number;
-  /**
-   * The stack that's currently being rolled back
-   */
-  readonly stack: CloudFormationStackArtifact;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/actions/watch/index.ts b/packages/@aws-cdk/toolkit-lib/lib/actions/watch/index.ts
index 8887b5647..25824c017 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/actions/watch/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/actions/watch/index.ts
@@ -38,32 +38,3 @@ export interface WatchOptions extends BaseDeployOptions {
    */
   readonly outdir?: string;
 }
-
-/**
- * The computed file watch settings
- */
-export interface WatchSettings {
-  /**
-   * The directory observed for file changes
-   */
-  readonly watchDir: string;
-  /**
-   * List of include patterns for watching files
-   */
-  readonly includes: string[];
-  /**
-   * List of excludes patterns for watching files
-   */
-  readonly excludes: string[];
-}
-
-export interface FileWatchEvent {
-  /**
-   * The change to the path
-   */
-  readonly event: string;
-  /**
-   * The path that has an observed event
-   */
-  readonly path?: string;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts b/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
index 7a1934796..4d987c5c7 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/aws-cdk.ts
@@ -11,7 +11,6 @@ export { ResourceMigrator } from '../../../../aws-cdk/lib/api/resource-import';
 export { CloudWatchLogEventMonitor, findCloudWatchLogGroups } from '../../../../aws-cdk/lib/api/logs';
 export { type WorkGraph, WorkGraphBuilder, AssetBuildNode, AssetPublishNode, StackNode, Concurrency } from '../../../../aws-cdk/lib/api/work-graph';
 export { Bootstrapper } from '../../../../aws-cdk/lib/api/bootstrap';
-export type { StackActivity, StackMonitoringControlEvent } from '../../../../aws-cdk/lib/api/stack-events';
 
 // Context Providers
 export * as contextproviders from '../../../../aws-cdk/lib/context-providers';
@@ -25,7 +24,7 @@ export { RWLock, type ILock } from '../../../../aws-cdk/lib/api/util/rwlock';
 export { loadTree, some } from '../../../../aws-cdk/lib/tree';
 
 // @todo Cloud Assembly and Executable - this is a messy API right now
-export { CloudAssembly, sanitizePatterns, type StackDetails, StackCollection, ExtendedStackSelection } from '../../../../aws-cdk/lib/api/cxapp/cloud-assembly';
+export { CloudAssembly, sanitizePatterns, StackCollection, ExtendedStackSelection } from '../../../../aws-cdk/lib/api/cxapp/cloud-assembly';
 export { prepareDefaultEnvironment, prepareContext, spaceAvailableForContext } from '../../../../aws-cdk/lib/api/cxapp/exec';
 export { guessExecutable } from '../../../../aws-cdk/lib/api/cxapp/exec';
 
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/index.ts b/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/index.ts
index 412137fd7..7ab0af5dc 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/cloud-assembly/index.ts
@@ -1,4 +1,4 @@
-export * from './context';
+export * from '../../api/shared-public';
 export * from './source-builder';
 export * from './stack-selector';
 export * from './types';
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/io/index.ts b/packages/@aws-cdk/toolkit-lib/lib/api/io/index.ts
index 78ea7527a..00239c196 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/io/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/io/index.ts
@@ -1,23 +1 @@
 export type { IoMessageLevel, IoMessageCode, IIoHost, IoMessage, IoRequest } from '../shared-public';
-
-/**
- * An SDK logging trace.
- *
- * Only info, warn and error level messages are emitted.
- * SDK traces are emitted as traces to the IoHost, but contain the original SDK logging level.
- */
-export interface SdkTrace {
-  /**
-   * The level the SDK has emitted the original message with
-   */
-  readonly sdkLevel: 'info' | 'warn' | 'error';
-
-  /**
-   * The content of the SDK trace
-   *
-   * This will include the request and response data for API calls, including potentially sensitive information.
-   *
-   * @see https://docs.aws.amazon.com/sdk-for-javascript/v3/developer-guide/logging-sdk-calls.html
-   */
-  readonly content: any;
-}
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/index.ts b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/index.ts
index bfc5d252f..811fb65da 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/index.ts
@@ -1,4 +1,4 @@
-export * from './messages';
+export * from '../../shared-public';
 export * from './io-host-wrappers';
 export * from './timer';
 export * from './sdk-logger';
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/sdk-logger.ts b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/sdk-logger.ts
index d96a81e99..c0d036fa8 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/sdk-logger.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/sdk-logger.ts
@@ -1,9 +1,9 @@
 
 import { inspect } from 'util';
 import type { Logger } from '@smithy/types';
-import { IO } from './messages';
 import { replacerBufferWithInfo } from '../../../private/util';
 import type { IoHelper } from '../../shared-private';
+import { IO } from '../../shared-public';
 
 export function asSdkLogger(ioHost: IoHelper): Logger {
   return new class implements Logger {
diff --git a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/timer.ts b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/timer.ts
index 2351e786a..28547a6cc 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/api/io/private/timer.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/api/io/private/timer.ts
@@ -1,7 +1,7 @@
 import { format } from 'util';
-import { IO } from './messages';
 import { formatTime } from '../../../private/util';
 import type { IoHelper } from '../../shared-private';
+import { IO } from '../../shared-public';
 
 /**
  * Helper class to measure the time of code.
diff --git a/packages/@aws-cdk/toolkit-lib/lib/toolkit/index.ts b/packages/@aws-cdk/toolkit-lib/lib/toolkit/index.ts
index 952bc9a3a..c28e88c5d 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/toolkit/index.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/toolkit/index.ts
@@ -1,2 +1,2 @@
 export * from './toolkit';
-export * from './types';
+export * from '../api/shared-public';
diff --git a/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts b/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
index 096fdc34b..eef1d0f56 100644
--- a/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
+++ b/packages/@aws-cdk/toolkit-lib/lib/toolkit/toolkit.ts
@@ -5,7 +5,6 @@ import * as chokidar from 'chokidar';
 import * as fs from 'fs-extra';
 import type { ToolkitServices } from './private';
 import { assemblyFromSource } from './private';
-import type { AssemblyData } from './types';
 import type { BootstrapEnvironments, BootstrapOptions } from '../actions/bootstrap';
 import { BootstrapSource } from '../actions/bootstrap';
 import { AssetBuildTime, type DeployOptions, RequireApproval } from '../actions/deploy';
@@ -18,7 +17,7 @@ import { type SynthOptions } from '../actions/synth';
 import type { WatchOptions } from '../actions/watch';
 import { patternsArrayForWatch } from '../actions/watch/private';
 import { type SdkConfig } from '../api/aws-auth';
-import type { SuccessfulDeployStackResult, StackCollection, Concurrency, AssetBuildNode, AssetPublishNode, StackNode, StackDetails } from '../api/aws-cdk';
+import type { SuccessfulDeployStackResult, StackCollection, Concurrency, AssetBuildNode, AssetPublishNode, StackNode } from '../api/aws-cdk';
 import { DEFAULT_TOOLKIT_STACK_NAME, Bootstrapper, SdkProvider, Deployments, HotswapMode, ResourceMigrator, tagsForStack, CliIoHost, WorkGraphBuilder, CloudWatchLogEventMonitor, findCloudWatchLogGroups } from '../api/aws-cdk';
 import type { ICloudAssemblySource } from '../api/cloud-assembly';
 import { StackSelectionStrategy } from '../api/cloud-assembly';
@@ -28,7 +27,7 @@ import type { IIoHost, IoMessageLevel } from '../api/io';
 import { Timer, IO, asSdkLogger, withoutColor, withoutEmojis, withTrimmedWhitespace } from '../api/io/private';
 import type { IoHelper } from '../api/shared-private';
 import { asIoHelper } from '../api/shared-private';
-import type { ToolkitAction } from '../api/shared-public';
+import type { AssemblyData, StackDetails, ToolkitAction } from '../api/shared-public';
 import { ToolkitError } from '../api/shared-public';
 import { obscureTemplate, serializeStructure, validateSnsTopicArn, formatTime, formatErrorMessage } from '../private/util';
 import { pLimit } from '../util/concurrency';
diff --git a/packages/@aws-cdk/toolkit-lib/scripts/gen-code-registry.ts b/packages/@aws-cdk/toolkit-lib/scripts/gen-code-registry.ts
index ed00fbbdb..950325d12 100644
--- a/packages/@aws-cdk/toolkit-lib/scripts/gen-code-registry.ts
+++ b/packages/@aws-cdk/toolkit-lib/scripts/gen-code-registry.ts
@@ -1,16 +1,16 @@
 import * as fs from 'fs';
 import * as util from 'util';
-import { IO } from '../lib/api/io/private/messages';
+import { IO } from '../lib/api/shared-public';
 
 function codesToMarkdownTable(codes: Record<string, {
   code: string;
   level: string;
   description: string;
-  interface?: string; 
+  interface?: string;
 }>, mdPrefix?: string, mdPostfix?: string) {
   let table = '| Code | Description | Level | Data Interface |\n';
   table += '|------|-------------|-------|----------------|\n';
-  
+
   Object.entries(codes).forEach(([key, code]) => {
     // we allow DEFAULT_* as special case here
     if (key !== code.code && !key.startsWith('DEFAULT_')) {
diff --git a/packages/@aws-cdk/toolkit-lib/test/toolkit/toolkit.test.ts b/packages/@aws-cdk/toolkit-lib/test/toolkit/toolkit.test.ts
index 156b428b8..6f5983c56 100644
--- a/packages/@aws-cdk/toolkit-lib/test/toolkit/toolkit.test.ts
+++ b/packages/@aws-cdk/toolkit-lib/test/toolkit/toolkit.test.ts
@@ -20,6 +20,7 @@ describe('message formatting', () => {
       level: 'info',
       code: 'CDK_TOOLKIT_I0000',
       time: new Date(),
+      data: undefined,
     });
 
     expect(ioHost.notifySpy).toHaveBeenCalledWith(expect.objectContaining({
@@ -40,6 +41,7 @@ describe('message formatting', () => {
       level: 'info',
       code: 'CDK_TOOLKIT_I0000',
       time: new Date(),
+      data: undefined,
     });
 
     expect(ioHost.notifySpy).toHaveBeenCalledWith(expect.objectContaining({
@@ -60,6 +62,7 @@ describe('message formatting', () => {
       level: 'info',
       code: 'CDK_TOOLKIT_I0000',
       time: new Date(),
+      data: undefined,
     });
 
     expect(ioHost.notifySpy).toHaveBeenCalledWith(expect.objectContaining({
diff --git a/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts b/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
index 5de89fa85..dcaf93ea8 100644
--- a/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
+++ b/packages/aws-cdk/lib/api/aws-auth/sdk-logger.ts
@@ -1,5 +1,6 @@
 import { inspect, format } from 'util';
 import { Logger } from '@smithy/types';
+import { IO } from '../../../../@aws-cdk/tmp-toolkit-helpers/src/api/io/messages';
 import { IoHelper } from '../../../../@aws-cdk/tmp-toolkit-helpers/src/api/io/private';
 import { replacerBufferWithInfo } from '../../util';
 
@@ -11,12 +12,7 @@ export class SdkToCliLogger implements Logger {
   }
 
   private notify(level: 'debug' | 'info' | 'warn' | 'error', ...content: any[]) {
-    void this.ioHelper.notify({
-      time: new Date(),
-      level: 'trace', // always log all SDK logs at trace level, no matter what level they are coming from the SDK
-      code: 'CDK_SDK_I0000',
-      message: format('[SDK %s] %s', level, formatSdkLoggerContent(content)),
-    });
+    void this.ioHelper.notify(IO.CDK_SDK_I0000.msg(format('[SDK %s] %s', level, formatSdkLoggerContent(content))));
   }
 
   public trace(..._content: any[]) {
diff --git a/packages/aws-cdk/lib/api/cxapp/cloud-assembly.ts b/packages/aws-cdk/lib/api/cxapp/cloud-assembly.ts
index c2c8aae65..0bf9eec44 100644
--- a/packages/aws-cdk/lib/api/cxapp/cloud-assembly.ts
+++ b/packages/aws-cdk/lib/api/cxapp/cloud-assembly.ts
@@ -1,5 +1,6 @@
 import type * as cxapi from '@aws-cdk/cx-api';
 import { SynthesisMessageLevel } from '@aws-cdk/cx-api';
+import { type StackDetails } from '@aws-cdk/tmp-toolkit-helpers';
 import * as chalk from 'chalk';
 import { minimatch } from 'minimatch';
 import * as semver from 'semver';
@@ -205,24 +206,6 @@ export class CloudAssembly {
   }
 }
 
-/**
- * The dependencies of a stack.
- */
-export type StackDependency = {
-  id: string;
-  dependencies: StackDependency[];
-};
-
-/**
- * Details of a stack.
- */
-export type StackDetails = {
-  id: string;
-  name: string;
-  environment: cxapi.Environment;
-  dependencies: StackDependency[];
-};
-
 /**
  * A collection of stacks and related artifacts
  *
diff --git a/packages/aws-cdk/lib/api/deployments/asset-publishing.ts b/packages/aws-cdk/lib/api/deployments/asset-publishing.ts
index 5579d4e14..43355ef65 100644
--- a/packages/aws-cdk/lib/api/deployments/asset-publishing.ts
+++ b/packages/aws-cdk/lib/api/deployments/asset-publishing.ts
@@ -199,6 +199,7 @@ export abstract class BasePublishProgressListener implements IPublishProgressLis
         formatMessage({
           level,
           message: this.getMessage(type, event),
+          data: undefined,
         }),
       );
     }
diff --git a/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts b/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
index b5064048a..b266cc9f3 100644
--- a/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
+++ b/packages/aws-cdk/lib/api/stack-events/stack-activity-monitor.ts
@@ -1,75 +1,16 @@
 
 import * as util from 'util';
-import { ArtifactMetadataEntryType, type MetadataEntry } from '@aws-cdk/cloud-assembly-schema';
+import { ArtifactMetadataEntryType } from '@aws-cdk/cloud-assembly-schema';
 import type { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
-import { StackEvent } from '@aws-sdk/client-cloudformation';
+import type { ResourceMetadata, StackActivity, StackMonitoringControlEvent } from '@aws-cdk/tmp-toolkit-helpers';
 import * as uuid from 'uuid';
 import { StackEventPoller } from './stack-event-poller';
 import { debug, error, info } from '../../cli/messages';
 import { stackEventHasErrorMessage } from '../../util';
 import type { ICloudFormationClient } from '../aws-auth';
-import { StackProgress, StackProgressMonitor } from './stack-progress-monitor';
+import { StackProgressMonitor } from './stack-progress-monitor';
 import { IoHelper } from '../../../../@aws-cdk/tmp-toolkit-helpers/src/api/io/private';
 
-/**
- * Payload when stack monitoring is starting or stopping for a given stack deployment.
- */
-export interface StackMonitoringControlEvent {
-  /**
-   * A unique identifier for a specific stack deployment.
-   *
-   * Use this value to attribute stack activities received for concurrent deployments.
-   */
-  readonly deployment: string;
-
-  /**
-   * The stack artifact that is getting deployed
-   */
-  readonly stack: CloudFormationStackArtifact;
-
-  /**
-   * The name of the Stack that is getting deployed
-   */
-  readonly stackName: string;
-
-  /**
-   * Total number of resources taking part in this deployment
-   *
-   * The number might not always be known or accurate.
-   * Only use for informational purposes and handle the case when it's unavailable.
-   */
-  readonly resourcesTotal?: number;
-}
-
-export interface StackActivity {
-  /**
-   * A unique identifier for a specific stack deployment.
-   *
-   * Use this value to attribute stack activities received for concurrent deployments.
-   */
-  readonly deployment: string;
-
-  /**
-   * The Stack Event as received from CloudFormation
-   */
-  readonly event: StackEvent;
-
-  /**
-   * Additional resource metadata
-   */
-  readonly metadata?: ResourceMetadata;
-
-  /**
-   * The stack progress
-   */
-  readonly progress: StackProgress;
-}
-
-export interface ResourceMetadata {
-  entry: MetadataEntry;
-  constructPath: string;
-}
-
 export interface StackActivityMonitorProps {
   /**
    * The CloudFormation client
diff --git a/packages/aws-cdk/lib/api/stack-events/stack-progress-monitor.ts b/packages/aws-cdk/lib/api/stack-events/stack-progress-monitor.ts
index ee8876172..92a0209b9 100644
--- a/packages/aws-cdk/lib/api/stack-events/stack-progress-monitor.ts
+++ b/packages/aws-cdk/lib/api/stack-events/stack-progress-monitor.ts
@@ -1,25 +1,9 @@
 
 import * as util from 'util';
+import type { StackProgress } from '@aws-cdk/tmp-toolkit-helpers';
 import { StackEvent } from '@aws-sdk/client-cloudformation';
 import { padLeft } from '../../util';
 
-export interface StackProgress {
-  /**
-   * The total number of progress monitored resources.
-   */
-  readonly total?: number;
-
-  /**
-   * The number of completed resources.
-   */
-  readonly completed: number;
-
-  /**
-   * The current progress as a [34/42] string, or just [34] if the total is unknown.
-   */
-  readonly formatted: string;
-}
-
 /**
  * Monitors stack progress.s
  */
diff --git a/packages/aws-cdk/lib/cli/activity-printer/base.ts b/packages/aws-cdk/lib/cli/activity-printer/base.ts
index 3e1534a7a..8eab609f2 100644
--- a/packages/aws-cdk/lib/cli/activity-printer/base.ts
+++ b/packages/aws-cdk/lib/cli/activity-printer/base.ts
@@ -1,6 +1,6 @@
 import { CloudFormationStackArtifact } from '@aws-cdk/cx-api';
-import type { StackActivity } from '../../api/stack-events';
-import { StackProgress } from '../../api/stack-events/stack-progress-monitor';
+import { type StackActivity, type StackProgress } from '@aws-cdk/tmp-toolkit-helpers';
+import { IO } from '../../../../@aws-cdk/tmp-toolkit-helpers/src/api/io/messages';
 import { IoMessage } from '../../toolkit/cli-io-host';
 import { maxResourceTypeLength, stackEventHasErrorMessage } from '../../util';
 
@@ -52,14 +52,14 @@ export abstract class ActivityPrinterBase implements IActivityPrinter {
    * Receive a stack activity message
    */
   public notify(msg: IoMessage<unknown>): void {
-    switch (msg.code) {
-      case 'CDK_TOOLKIT_I5501':
-        this.start(msg.data as { stack: CloudFormationStackArtifact });
+    switch (true) {
+      case IO.CDK_TOOLKIT_I5501.is(msg):
+        this.start(msg.data);
         break;
-      case 'CDK_TOOLKIT_I5502':
-        this.activity(msg.data as StackActivity);
+      case IO.CDK_TOOLKIT_I5502.is(msg):
+        this.activity(msg.data);
         break;
-      case 'CDK_TOOLKIT_I5503':
+      case IO.CDK_TOOLKIT_I5503.is(msg):
         this.stop();
         break;
       default:
diff --git a/packages/aws-cdk/lib/cli/activity-printer/current.ts b/packages/aws-cdk/lib/cli/activity-printer/current.ts
index e8e8d8aa0..a2c473dfc 100644
--- a/packages/aws-cdk/lib/cli/activity-printer/current.ts
+++ b/packages/aws-cdk/lib/cli/activity-printer/current.ts
@@ -1,8 +1,8 @@
 import * as util from 'util';
+import type { StackActivity } from '@aws-cdk/tmp-toolkit-helpers';
 import * as chalk from 'chalk';
 import { ActivityPrinterBase, ActivityPrinterProps } from './base';
 import { RewritableBlock } from './display';
-import type { StackActivity } from '../../api/stack-events';
 import { padLeft, padRight, stackEventHasErrorMessage } from '../../util';
 
 /**
diff --git a/packages/aws-cdk/lib/cli/activity-printer/history.ts b/packages/aws-cdk/lib/cli/activity-printer/history.ts
index c6cafb124..82b7651c5 100644
--- a/packages/aws-cdk/lib/cli/activity-printer/history.ts
+++ b/packages/aws-cdk/lib/cli/activity-printer/history.ts
@@ -1,7 +1,7 @@
 import * as util from 'util';
+import type { StackActivity } from '@aws-cdk/tmp-toolkit-helpers';
 import * as chalk from 'chalk';
 import { ActivityPrinterBase, ActivityPrinterProps } from './base';
-import type { StackActivity } from '../../api/stack-events';
 import { padRight } from '../../util';
 
 /**
diff --git a/packages/aws-cdk/lib/list-stacks.ts b/packages/aws-cdk/lib/list-stacks.ts
index f2d212520..dbe846a6a 100644
--- a/packages/aws-cdk/lib/list-stacks.ts
+++ b/packages/aws-cdk/lib/list-stacks.ts
@@ -1,4 +1,5 @@
-import { DefaultSelection, ExtendedStackSelection, type StackDetails } from './api/cxapp/cloud-assembly';
+import type { StackDetails } from '@aws-cdk/tmp-toolkit-helpers';
+import { DefaultSelection, ExtendedStackSelection } from './api/cxapp/cloud-assembly';
 import { CdkToolkit } from './cli/cdk-toolkit';
 
 /**
diff --git a/packages/aws-cdk/lib/logging.ts b/packages/aws-cdk/lib/logging.ts
index dd0aa12d3..03ea3fd3d 100644
--- a/packages/aws-cdk/lib/logging.ts
+++ b/packages/aws-cdk/lib/logging.ts
@@ -35,6 +35,7 @@ function formatMessageAndLog(
     level,
     message: finalMessage,
     code,
+    data: undefined,
   };
 
   void ioHost.notify(ioMessage);