AHP Swift Package v0.5.2

[0.5.2] — 2026-07-09

Implements AHP 0.5.2.

Added

• Typed resource* convenience methods on AHPClient: send wrappers (resourceRead, resourceWrite, resourceList, resourceCopy, resourceDelete, resourceMove, resourceResolve, resourceMkdir, resourceRequest, createResourceWatch) and inbound server-request handling via setServerRequestHandler(_:) / setResourceRequestHandlers(_:) (new ServerRequestHandler typealias and ResourceRequestHandlers type). Inbound server-initiated requests are answered by the installed handler (still MethodNotFound when none is set).
• ToolResultTerminalCompleteContent for terminal-style completion metadata in tool
  results.
• Optional enabled field on the child customization types
  (AgentCustomization, SkillCustomization, PromptCustomization,
  RuleCustomization, HookCustomization).
• disableUserInvocation on SkillCustomization, plus disableModelInvocation
  and disableUserInvocation on AgentCustomization.
• Optional reviewed field on ChangesetFile. Omitting it (or setting it to
  nil) signals that the server does not support the file "review"
  functionality.
• changeset/filesReviewedChanged action for servers to update the reviewed
  flag of one or more changeset files.
• Optional meta (wire _meta) provider-metadata field on every customization
  type, moved from AgentCustomization up to the shared customization base so
  PluginCustomization, ClientPluginCustomization, DirectoryCustomization,
  SkillCustomization, PromptCustomization, RuleCustomization,
  HookCustomization, and McpServerCustomization all carry it.
• Optional serverInfo on InitializeResult and clientInfo on
  InitializeParams, each an Implementation (name, optional version,
  optional title), identifying the implementation and build behind either side
  of the handshake. Informational only — MUST NOT be used for feature detection.
• Optional terminalCommandPrefix on InitializeResult for hosts that support
  interpreting !-prefixed user messages as terminal commands.
• Optional version field on PluginCustomization (inherited by
  ClientPluginCustomization), carrying the plugin's semver sourced from the
  Open Plugins manifest. Provenance / display only.
• session/mcpServerStartRequested and session/mcpServerStopRequested
  actions for clients to ask the host to start or stop MCP servers; stopping
  moves an authRequired server to stopped so it no longer waits on
  authentication.
• InputRequestResponsePart and the ResponsePart.inputRequest case. The
  reducer now records a resolved input request in the active turn's
  responseParts on chatInputCompleted — embedding the resolved
  ChatInputRequest (final answers) and the response (accept, decline,
  or cancel) — so the outcome persists after the live request is removed.
  Abandoned requests still record nothing (#324).

Changed

• The session/customizationToggled reducer now toggles any top-level
  customization (plugin, directory, or top-level mcpServer) or an
  individual child by id, setting that entry's enabled.

AHP Spec v0.5.2

[0.5.2] — 2026-07-09

Spec version: 0.5.2

Added

• ToolResultTerminalCompleteContent for terminal-style completion metadata in tool
  results.
• Optional enabled flag on the child customizations (AgentCustomization,
  SkillCustomization, PromptCustomization, RuleCustomization,
  HookCustomization) so an individual child can be turned off independently of
  its container; absent means enabled.
• disableUserInvocation on SkillCustomization, plus disableModelInvocation
  and disableUserInvocation on AgentCustomization, giving custom agents and
  skills a symmetric user/model invocation matrix.
• Optional reviewed field on ChangesetFile. Omitting it (or setting it to
  undefined) signals that the server does not support the file "review"
  functionality.
• changeset/filesReviewedChanged action for servers to update the reviewed
  flag of one or more changeset files.
• Hoisted the optional _meta provider-metadata slot from AgentCustomization
  up to the shared CustomizationBase, so every customization type
  (PluginCustomization, ClientPluginCustomization, DirectoryCustomization,
  SkillCustomization, PromptCustomization, RuleCustomization,
  HookCustomization, and McpServerCustomization) now carries the same
  provider-specific escape hatch. Wire-compatible: AgentCustomization still
  exposes _meta, now by inheritance.
• Optional serverInfo on InitializeResult and clientInfo on
  InitializeParams, each an Implementation (name, optional version,
  optional title), so either side of the handshake can identify its
  implementation and build. Informational only — mirrors LSP/MCP and MUST NOT
  be used for feature detection.
• InputRequestResponsePart (kind: 'inputRequest') — a new ResponsePart
  variant that records a resolved input request in a turn's transcript. On
  chat/inputCompleted, the reducer now appends this part (embedding the
  resolved ChatInputRequest with its final answers and the response:
  accept, decline, or cancel) to the active turn's responseParts, so an
  elicitation's outcome persists durably, mirroring how a resolved tool-call
  confirmation is retained. Requests abandoned by turn end, cancel, error, or
  truncation still record nothing (#324).
• Optional terminalCommandPrefix marker on InitializeResult for hosts that
  support interpreting !-prefixed user messages as terminal commands.
• Optional version field on PluginCustomization (inherited by
  ClientPluginCustomization), carrying the plugin's semver sourced from the
  Open Plugins manifest's optional version. Provenance / display only; absent
  when the manifest declares no version or the source has no version concept.
• session/mcpServerStartRequested and session/mcpServerStopRequested
  actions for clients to ask the host to start or stop MCP servers; stopping
  moves an authRequired server to stopped so it no longer waits on
  authentication.

Changed

• session/customizationToggled now targets any top-level customization
  (plugin, directory, or top-level mcpServer) or an individual child by
  id and sets that entry's enabled; the effective state of a child is
  container.enabled && (child.enabled ?? true).

Fixed

• The generated JSON Schema artifacts (schema/*.json) are now self-contained
  and strict-oneOf-safe. The generator no longer emits an empty {} branch in
  a union type alias's oneOf (which matched any value and defeated strict
  oneOf validation), backfills the enum, enum-member, and type-alias $refs
  that were previously dangling across all five schema files, and renders null
  members as { "type": "null" } (#302).

Go module v0.5.2

[0.5.2] — 2026-07-09

Implements AHP 0.5.2.

Added

• Typed resource* convenience methods on ahp.Client: send wrappers (ResourceRead, ResourceWrite, ResourceList, ResourceCopy, ResourceDelete, ResourceMove, ResourceResolve, ResourceMkdir, ResourceRequest, CreateResourceWatch) and inbound server-request handling via SetServerRequestHandler / SetResourceRequestHandlers (new ServerRequestHandler and ResourceRequestHandlers types). Inbound server-initiated requests are now answered (previously dropped) — via the installed handler, or MethodNotFound when none is set.
• ToolResultTerminalCompleteContent for terminal-style completion metadata in tool
  results.
• Optional Enabled field on the child customization types
  (AgentCustomization, SkillCustomization, PromptCustomization,
  RuleCustomization, HookCustomization).
• DisableUserInvocation on SkillCustomization, plus DisableModelInvocation
  and DisableUserInvocation on AgentCustomization.
• Optional Reviewed field on ChangesetFile. Omitting it (or setting it to
  nil) signals that the server does not support the file "review"
  functionality.
• changeset/filesReviewedChanged action for servers to update the Reviewed
  flag of one or more changeset files.
• Optional Meta (wire _meta) provider-metadata field on every customization
  type, moved from AgentCustomization up to the shared customization base so
  PluginCustomization, ClientPluginCustomization, DirectoryCustomization,
  SkillCustomization, PromptCustomization, RuleCustomization,
  HookCustomization, and McpServerCustomization all carry it.
• Optional ServerInfo on InitializeResult and ClientInfo on
  InitializeParams, each an Implementation struct (Name, optional
  Version, optional Title), identifying the implementation and build behind
  either side of the handshake. Informational only — MUST NOT be used for
  feature detection.
• Optional TerminalCommandPrefix on InitializeResult for hosts that support
  interpreting !-prefixed user messages as terminal commands.
• Optional Version field on PluginCustomization (inherited by
  ClientPluginCustomization), carrying the plugin's semver sourced from the
  Open Plugins manifest. Provenance / display only.
• session/mcpServerStartRequested and session/mcpServerStopRequested
  actions for clients to ask the host to start or stop MCP servers; stopping
  moves an authRequired server to stopped so it no longer waits on
  authentication.
• InputRequestResponsePart and the ResponsePartKindInputRequest discriminant.
  The reducer now records a resolved input request in the active turn's
  ResponseParts on ChatInputCompletedAction — embedding the resolved
  ChatInputRequest (final Answers) and the Response (accept, decline,
  or cancel) — so the outcome persists after the live request is removed.
  Abandoned requests still record nothing (#324).

Changed

• The session/customizationToggled reducer now toggles any top-level
  customization (plugin, directory, or top-level mcpServer) or an
  individual child by id, setting that entry's Enabled.

AHP Swift Package v0.5.1

[0.5.1] — 2026-07-02

Implements AHP 0.5.1.

Added

• Optional nonce field on ContentRef.
• SubscribeParams.delivery.maxLatencyMs and
  AHPClient.subscribe(_:delivery:) for clients to request a maximum
  subscription delivery latency, including 0 for no intentional coalescing.
• Optional capabilities field on AgentInfo (AgentCapabilities with a
  nested multipleChats capability carrying fork) so clients gate multi-chat
  and fork via advertised capabilities instead of provider-id switches.
• Cursor-based pagination for listSessions, via new shared PaginatedParams
  (limit + cursor) and PaginatedResult (nextCursor) types:
  ListSessionsParams and ListSessionsResult now carry these fields, letting
  clients page through a large session catalogue. Fully additive — omitting the
  fields preserves prior behaviour.
• SubscribeParams.view.turns, ChatState.turnsNextCursor, and the
  chat/turnsLoaded action so clients can subscribe to a bounded tail of chat
  history and page older turns into the reduced chat state on demand.
• SessionState.inputNeeded — a session-level aggregate of outstanding input
  requests across all chats (SessionInputRequest enum with
  SessionChatInputRequest, SessionToolConfirmationRequest, and
  SessionToolClientExecutionRequest cases), plus the
  StateAction.sessionInputNeededSet / StateAction.sessionInputNeededRemoved
  actions and the ToolCallConfirmationState union. The session reducer
  maintains the SessionStatus.inputNeeded activity bit from the queue,
  clearing it (falling back to .inProgress) when the last entry is removed.
• Optional intention field on ChatToolCallStartAction and every tool-call
  lifecycle state.
• Optional model and tools fields on AgentCustomization for a custom
  agent's pinned model and tool allowlist.

Changed

• fetchTurns now accepts cursor from ChatState.turnsNextCursor and returns
  an empty result after the host has loaded older turns into chat state, instead
  of returning a detached { turns, hasMore } page.
• Generated clients now advertise only protocol 0.5.1, since the fetchTurns
  contract is not wire-compatible with 0.5.0.

Removed

• filter field from ListSessionsParams. It was an untyped placeholder with
  no defined semantics; it will return with a concrete shape once session
  filtering/sorting is specified.

Fixed

• SnapshotState now decodes the chat variant. Its decoder previously never
  attempted ChatState, so chat snapshots failed to decode. Variant
  disambiguation also no longer relies on the removed summary field (a leftover
  from before SessionState was flattened).

AHP Spec v0.5.1

[0.5.1] — 2026-07-02

Spec version: 0.5.1

Added

• SubscribeParams.delivery.maxLatencyMs for clients to request a maximum
  subscription delivery latency, including 0 for no intentional coalescing.
• SessionState.inputNeeded — a session-level aggregate of outstanding input
  requests across all chats, so a client can discover and answer elicitations,
  tool confirmations, and client-tool execution requests from the session
  channel without subscribing to individual chats. Each entry
  (SessionChatInputRequest, SessionToolConfirmationRequest,
  SessionToolClientExecutionRequest, unioned as SessionInputRequest) carries
  the owning chat URI plus the identifiers needed to respond.
• session/inputNeededSet and session/inputNeededRemoved actions for the host
  to upsert and remove SessionState.inputNeeded entries. The session reducer
  sets SessionStatus.InputNeeded while the queue is non-empty and clears it
  (falling back to InProgress) once it empties, preserving orthogonal flags.
• ToolCallConfirmationState union (ToolCallPendingConfirmationState | ToolCallPendingResultConfirmationState) for the tool call carried by
  SessionToolConfirmationRequest.
• Optional nonce field on ContentRef.
• Optional intention field on chat/toolCallStart and every ToolCallState
  variant, providing a human-readable description of what the invocation intends
  to do.
• Optional model and tools fields on AgentCustomization, giving a custom
  agent's pinned model and tool allowlist a first-class home instead of _meta.
• Optional capabilities field on AgentInfo (AgentCapabilities with a
  nested multipleChats capability carrying fork) so clients gate multi-chat
  and fork via advertised capabilities instead of provider-id switches.
• Cursor-based pagination for listSessions, via new shared PaginatedParams
  (limit + cursor) and PaginatedResult (nextCursor) types:
  ListSessionsParams now extends PaginatedParams and ListSessionsResult
  extends PaginatedResult, letting clients fetch a large session catalogue
  incrementally. Fully additive — omitting the fields preserves today's
  behaviour.
• SubscribeParams.view.turns, ChatState.turnsNextCursor, and the
  chat/turnsLoaded action so clients can subscribe to a bounded tail of chat
  history and page older turns into the reduced chat state on demand.

Changed

• fetchTurns now accepts cursor from ChatState.turnsNextCursor and returns
  an empty result after the host has loaded older turns into chat state, instead
  of returning a detached { turns, hasMore } page.
• Generated clients now advertise only protocol 0.5.1, since the fetchTurns
  contract is not wire-compatible with 0.5.0.

Removed

• filter field from ListSessionsParams. It was an untyped object
  placeholder with no defined semantics; it will be reintroduced with a concrete
  shape once session filtering/sorting is specified.

Go module v0.5.1

[0.5.1] — 2026-07-02

Implements AHP 0.5.1.

Added

• Optional Nonce field on ContentRef.
• SubscribeParams.Delivery.MaxLatencyMs and Client.SubscribeWithDelivery
  for clients to request a maximum subscription delivery latency, including
  0 for no intentional coalescing.
• Optional capabilities field on AgentInfo (AgentCapabilities with a
  nested multipleChats capability carrying fork) so clients gate multi-chat
  and fork via advertised capabilities instead of provider-id switches.
• Cursor-based pagination for listSessions, via new shared PaginatedParams
  (Limit + Cursor) and PaginatedResult (NextCursor) types:
  ListSessionsParams and ListSessionsResult now carry these fields, letting
  clients page through a large session catalogue. Fully additive — omitting the
  fields preserves prior behaviour.
• SubscribeParams.View.Turns, ChatState.TurnsNextCursor, and the
  chat/turnsLoaded action so clients can subscribe to a bounded tail of chat
  history and page older turns into the reduced chat state on demand.
• SessionState.InputNeeded — a session-level aggregate of outstanding input
  requests across all chats (SessionInputRequest union with
  SessionChatInputRequest, SessionToolConfirmationRequest, and
  SessionToolClientExecutionRequest), plus the SessionInputNeededSetAction
  (wire session/inputNeededSet) and SessionInputNeededRemovedAction (wire
  session/inputNeededRemoved) actions and the ToolCallConfirmationState
  union. The session reducer maintains the SessionStatusInputNeeded activity
  bit from the queue, clearing it (falling back to SessionStatusInProgress)
  when the last entry is removed.
• Optional Intention field on ChatToolCallStartAction and every tool-call
  lifecycle state.
• Optional Model and Tools fields on AgentCustomization for a custom
  agent's pinned model and tool allowlist.

Changed

• fetchTurns now accepts Cursor from ChatState.TurnsNextCursor and returns
  an empty result after the host has loaded older turns into chat state, instead
  of returning a detached { turns, hasMore } page.
• Generated clients now advertise only protocol 0.5.1, since the fetchTurns
  contract is not wire-compatible with 0.5.0.

Removed

• Filter field from ListSessionsParams. It was an untyped placeholder with
  no defined semantics; it will return with a concrete shape once session
  filtering/sorting is specified.

Fixed

• SnapshotState.UnmarshalJSON now decodes the Chat variant. Variant
  disambiguation previously probed for the removed summary field (a leftover
  from before SessionState was flattened), so chat and session snapshots both
  fell through to the Root catch-all. Sessions are now matched on lifecycle
  and chats on turns.

AHP Swift Package v0.5.0

[0.5.0] — 2026-06-26

Implements AHP 0.5.0.

Added

• ChatActivityChangedAction (StateAction.chatActivityChanged, wire
  chat/activityChanged) for updating a chat's current activity description
  independently of the session summary.
• ProgressParams struct (wire root/progress) — a generic progress notification
  correlated by a progressToken (added on CreateSessionParams).
  Used today for the lazy first-use download of an agent's native SDK.
• SessionModelInfo.maxOutputTokens and SessionModelInfo.maxPromptTokens
  optional fields for communicating model token limits.
• SessionSummary.meta (_meta on the wire) optional provider metadata field
  for lightweight session-list presentation hints.
• SessionActiveClientRemovedAction (StateAction.sessionActiveClientRemoved,
  wire session/activeClientRemoved) to release a single active client by
  clientId.
• ChatDraftChangedAction (StateAction.chatDraftChanged, wire
  chat/draftChanged) and ChatState.draft (Message?) to set or clear the
  user's in-progress draft input for a chat. The chat reducer applies it
  without stamping modifiedAt.
• Message.model and Message.agent optional fields carrying the selection a
  message was composed with.

Changed

• SessionState.activeClients ([SessionActiveClient], required) replaces the
  single optional SessionState.activeClient; the session reducer upserts and
  removes entries keyed by clientId.
• StateAction.sessionActiveClientChanged is renamed to
  StateAction.sessionActiveClientSet (wire session/activeClientSet) with
  upsert-by-clientId semantics; it no longer unsets the active client
  (dispatch session/activeClientRemoved instead).
• ConfigPropertySchema.enum field is now [AnyCodable]? instead of
  [String]?, allowing numeric, boolean, and null enum values.
• ModelSelection.config values are now AnyCodable instead of String,
  allowing numeric, boolean, and null configuration values.
• SessionState now inlines the session metadata fields (provider, title,
  status, activity, project, workingDirectory, annotations) directly
  instead of embedding a summary: SessionSummary. The session reducer mutates
  these fields directly and no longer stamps a modifiedAt. SessionSummary
  remains a root-only catalog struct whose createdAt/modifiedAt are now
  ISO-8601 Strings and which no longer carries model/agent.
• ChatState and ChatSummary no longer carry model/agent.

Removed

• SessionActiveClientToolsChangedAction. An active client now updates its
  published tools by re-dispatching StateAction.sessionActiveClientSet with its
  full, updated entry.
• SessionModelChangedAction (StateAction.sessionModelChanged,
  session/modelChanged) and SessionAgentChangedAction
  (StateAction.sessionAgentChanged, session/agentChanged), along with their
  session-reducer handling.

AHP Spec v0.5.0

[0.5.0] — 2026-06-26

Spec version: 0.5.0

Added

• chat/activityChanged action for updating a chat's current activity
  description independently of the session summary.
• root/progress (ProgressParams) generic host→client progress notification,
  correlated by a progressToken the client supplies on the originating
  request (today createSession.progressToken) rather than a domain object. Lets
  the host report long-running work — e.g. the lazy first-use download of an
  agent's native SDK — so clients can show an indicator instead of a silent
  multi-second hang. Carries monotonic progress and optional total; complete
  when progress === total.
• createSession.progressToken optional opt-in token for receiving root/progress
  notifications about a session's bring-up.
• SessionModelInfo.maxOutputTokens and SessionModelInfo.maxPromptTokens
  optional fields for communicating model token limits.
• SessionSummary._meta optional provider metadata field for lightweight
  session-list presentation hints.
• JsonPrimitive type alias (string | number | boolean | null) in types/common/state.ts.
• session/activeClientRemoved action to release a single active client from a
  session by clientId.

Changed

• ConfigPropertySchema.enum now accepts JsonPrimitive[] instead of string[], allowing numeric, boolean, and null enum values.
• ModelSelection.config values are now JsonPrimitive (string | number | boolean | null) instead of string, allowing numeric, boolean, and null configuration values.
• SessionState.activeClients (a required array, keyed by clientId) replaces
  the single optional SessionState.activeClient. A session may now have
  multiple concurrent active clients.
• session/activeClientChanged is renamed to session/activeClientSet with
  upsert-by-clientId semantics. It no longer accepts null to unset the
  active client — dispatch session/activeClientRemoved instead.

Removed

• session/activeClientToolsChanged. An active client now updates its published
  tools by re-dispatching session/activeClientSet with its full, updated entry.

Fixed

• Corrected the ACTION_INTRODUCED_IN entries for annotations/set,
  annotations/removed, annotations/entrySet, and annotations/entryRemoved
  from 0.3.0 to 0.4.0. The annotations channel first shipped in the
  0.4.0 spec release (it is absent from spec/v0.3.0), so version
  negotiation must not advertise it to peers speaking 0.3.0.

Go module v0.5.0

[0.5.0] — 2026-06-26

Implements AHP 0.5.0.

Added

• ChatDraftChangedAction (wire chat/draftChanged) and ChatState.Draft
  (*Message) for syncing a chat's in-progress input draft; ApplyActionToChat
  sets or clears state.Draft without stamping ModifiedAt.
• Message.Model and Message.Agent optional fields recording the model /
  agent selection a message was composed with.
• ChatActivityChangedAction (wire chat/activityChanged) for updating a chat's
  current activity description independently of the session summary.
• ProgressParams struct (wire root/progress) — a generic progress notification
  correlated by a ProgressToken (added on CreateSessionParams).
  Used today for the lazy first-use download of an agent's native SDK.
• SessionModelInfo.MaxOutputTokens and SessionModelInfo.MaxPromptTokens
  optional fields for communicating model token limits.
• SessionSummary.Meta (wire _meta) optional provider metadata field for
  lightweight session-list presentation hints.
• SessionActiveClientRemovedAction (wire session/activeClientRemoved) to
  release a single active client by ClientId.

Changed

• SessionState no longer embeds a Summary sub-struct; its metadata fields
  (Provider, Title, Status, Activity, Project, WorkingDirectory,
  Annotations) are now inlined directly on SessionState, which no longer
  carries Model, Agent, CreatedAt, or ModifiedAt. ApplyActionToSession
  reads and writes these flat fields and no longer stamps a session
  ModifiedAt.
• SessionSummary is now a root-only catalog struct; its CreatedAt /
  ModifiedAt are ISO-8601 strings (previously numeric) and it no longer
  carries Model / Agent.
• ChatState and ChatSummary no longer carry Model / Agent.
• SessionState.ActiveClients ([]SessionActiveClient, required) replaces the
  single pointer SessionState.ActiveClient; ApplyActionToSession upserts and
  removes entries keyed by ClientId.
• SessionActiveClientChangedAction is renamed to SessionActiveClientSetAction
  (wire session/activeClientSet) with upsert-by-ClientId semantics; it no
  longer unsets the active client (dispatch session/activeClientRemoved
  instead).
• ConfigPropertySchema.Enum field is now []json.RawMessage instead of []string,
  allowing numeric, boolean, and null enum values.
• ModelSelection.Config values are now json.RawMessage instead of string,
  allowing numeric, boolean, and null configuration values.

Removed

• SessionModelChangedAction (wire session/modelChanged) and
  SessionAgentChangedAction (wire session/agentChanged); session model /
  agent are no longer part of the protocol surface.
• SessionActiveClientToolsChangedAction. An active client now updates its
  published tools by re-dispatching SessionActiveClientSetAction with its
  full, updated entry.

AHP Swift Package v0.4.0

[0.4.0] — 2026-06-19

Implements AHP 0.4.0.

Added

• MessageOrigin struct and MessageKind enum now type Message.origin
  (previously an untyped AnyCodable); MessageKind covers user, agent,
  tool, and systemNotification, adding faithful agent- and tool-initiated
  origins.
• ConfigPropertySchema.additionalProperties — optional field describing the
  schema for object-typed config properties beyond those in properties.
• ChangesetContentChangedAction for full-replacement changeset file
  snapshots with optional operations and error details.
• ChangesetOperationStatus.disabled — new case for changeset operations
  that are currently unavailable and cannot be invoked.
• ChangesetOperation.group — optional identifier for grouping related
  changeset operations together in the UI.
• _meta (meta) field on the per-turn chat actions (chat/turnStarted,
  chat/delta, chat/responsePart, chat/reasoning, chat/usage,
  chat/turnComplete, chat/turnCancelled, chat/error) — optional
  provider-specific metadata so hosts can carry portable per-event context,
  such as attributing an event to a specific agent (e.g. a sub-agent acting
  within the turn).

Changed

• ToolResultSubagentContent.resource is now specified as the spawned worker
  chat URI (ahp-chat:/<cid>), not a session URI — a tool-spawned
  sub-agent is a chat. Its doc now describes the correspondence with the worker
  chat's ChatOrigin.tool record (matching toolCallId), which remains the
  canonical representation of the spawn relationship.
• BREAKING: SessionStatus is now an OptionSet with a UInt32 rawValue
  (was Int), an unsigned 32-bit bitset that preserves combined and unknown
  forward-compat bits. Combine flags with set-union (∪ / union) and test
  membership with contains(_:).
• BREAKING: ChangesetOperationTarget's range target now carries a nested
  TextRange ({start: {line, character}, end: {line, character}}) instead of
  a flat {start, end} integer pair.

Added

• SnapshotState.resourceWatch case and matching
  MultiHostStateMirror.resourceWatches slot, so applySnapshot(host:snapshot:)
  can seed an ahp-resource-watch: channel's descriptor (root URI, recursive
  flag, optional includes/excludes) alongside the existing root / session /
  terminal / changeset / annotations slots. reset(host:) / reset() clear
  the new slot.

Fixed

• AnyCodable.encode no longer corrupts NSNumber-backed Int/Double values to Bool/Int. NSNumber is now special-cased before the generic Swift type arms, using CFBooleanGetTypeID() to distinguish boolean from numeric NSNumber instances.
• AnyCodable.encode(to:) now preserves unsigned integers above Int64.max (encoding NSNumber values whose objCType is unsigned via uint64Value instead of the signed int64Value fallback), and the AnyCodable.swift template in scripts/generate-swift.ts reproduces the full encode/equality logic so regenerating the scaffold no longer reintroduces the bug.
• MultiHostClient/host runtime now advertises the generated SUPPORTED_PROTOCOL_VERSIONS on initialize instead of a stale hard-coded "0.2.0".
• Session reducers now apply _meta (meta) updates from every
  tool-call-scoped action, not only session/toolCallStart.

Added

• annotationsReducer implemented; annotations conformance fixtures (210–219) now pass.

• AnnotationsUpdatedAction (annotations/updated) — partially updates an
  existing annotation's turnId / resource / range / resolved without
  resending its entries. Handled by the annotations reducer (no-op on unknown
  id).

• ahp-chat: channel for per-chat conversation state; SessionState.chats[] catalog; SessionState.defaultChat? input-routing hint; ChatOrigin provenance union; createChat / disposeChat commands.

• SessionChatAddedAction, SessionChatRemovedAction, and SessionChatUpdatedAction handling for incremental chat catalog updates.

• ChatSummary.workingDirectory — optional per-chat working directory. Falls back to the session's workingDirectory when absent.

• SessionDefaultChatChangedAction (session/defaultChatChanged) — updates SessionState.defaultChat to steer new input to the designated chat; absent value clears the hint.

• ErrorInfo.meta: [String: AnyCodable]? — optional provider-specific metadata bag on error payloads (serialized as _meta), mirroring the existing meta field on UsageInfo and other protocol types. Clients MAY inspect well-known keys here for richer, localised error UI.

• RootState now exposes an optional _meta property bag (meta: [String: AnyCodable]?) for implementation-defined agent-host metadata, such as a
  well-known hostBuild key carrying the host's build version/commit/date.

• changesetReducer and resourceWatchReducer — the two state reducers
  that were missing from the Swift client are now implemented, mirroring the
  canonical TypeScript reducers (and the Kotlin/.NET clients). changesetReducer
  folds changeset/* actions into ChangesetState; resourceWatchReducer
  treats resourceWatch/changed as a documented event pass-through. The
  fixture-driven reducer test no longer silently skips the terminal, changeset,
  and resourceWatch fixture families — they now decode and assert, with the
  remaining gaps (unknown-discriminant response part; the not-yet-implemented
  annotations channel) pinned by an explicit drift tripwire.

Changed

• ChatState is now flat — the previous embedded summary has been replaced with inlined resource / title / status / activity / modifiedAt / model / agent / origin / workingDirectory properties. ChatSummary remains as the standalone catalog entry on SessionState.chats.
• ChatSummary.modifiedAt and ChatState.modifiedAt are now ISO 8601 String values instead of Int64/UInt64 milliseconds.

Added

• ChatSummary.interactivity / ChatState.interactivity ("full" | "read-only" | "hidden") indicating how the user can interact with a chat. Absent defaults to "full".

Removed

• SessionChatsChangedAction (replaced by the three discrete chat-catalog actions above).

Fixed

• Encode-fidelity: an unknown StateAction variant no longer re-encodes to
  {} (dropping its type discriminant and extra fields); the raw payload is
  preserved on decode and re-emitted verbatim.
• Forward-compatibility: unknown discriminants on wire-decoded discriminated
  unions (ResponsePart, ToolCallState, TerminalClaim,
  TerminalContentPart, Customization, and other evolvable unions) now decode
  to a raw passthrough and re-encode verbatim instead of throwing
  DecodingError, so a snapshot carrying an unknown variant still decodes and
  subsequent actions fold correctly.
• ChangesetOperationResourceTarget / …RangeTarget now encode their kind
  discriminant (previously a computed property excluded from CodingKeys, so it
  was dropped on encode).