googleapis/google/cloud/ces/v1/session_service.proto

// Copyright 2026 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.cloud.ces.v1;

import "google/api/annotations.proto";
import "google/api/client.proto";
import "google/api/field_behavior.proto";
import "google/api/resource.proto";
import "google/cloud/ces/v1/common.proto";
import "google/cloud/ces/v1/example.proto";
import "google/cloud/ces/v1/search_suggestions.proto";
import "google/protobuf/struct.proto";

option go_package = "cloud.google.com/go/ces/apiv1/cespb;cespb";
option java_multiple_files = true;
option java_outer_classname = "SessionServiceProto";
option java_package = "com.google.cloud.ces.v1";
option (google.api.resource_definition) = {
  type: "ces.googleapis.com/Session"
  pattern: "projects/{project}/locations/{location}/apps/{app}/sessions/{session}"
};

// Session service provides APIs for interacting with CES agents.
service SessionService {
  option (google.api.default_host) = "ces.googleapis.com";
  option (google.api.oauth_scopes) =
      "https://www.googleapis.com/auth/ces,"
      "https://www.googleapis.com/auth/cloud-platform";

  // Initiates a single-turn interaction with the CES agent within a session.
  rpc RunSession(RunSessionRequest) returns (RunSessionResponse) {
    option (google.api.http) = {
      post: "/v1/{config.session=projects/*/locations/*/apps/*/sessions/*}:runSession"
      body: "*"
    };
  }

  // Initiates a single-turn interaction with the CES agent. Uses server-side
  // streaming to deliver incremental results and partial responses as they are
  // generated.
  //
  // By default, complete responses (e.g., messages from callbacks or full LLM
  // responses) are sent to the client as soon as they are available. To enable
  // streaming individual text chunks directly from the model, set
  // [enable_text_streaming][google.cloud.ces.v1.SessionConfig.enable_text_streaming]
  // to true.
  rpc StreamRunSession(RunSessionRequest) returns (stream RunSessionResponse) {
    option (google.api.http) = {
      post: "/v1/{config.session=projects/*/locations/*/apps/*/sessions/*}:streamRunSession"
      body: "*"
    };
  }

  // Establishes a bidirectional streaming connection with the CES agent.
  // The agent processes continuous multimodal inputs (e.g., text, audio) and
  // generates real-time multimodal output streams.
  //
  // --- Client Request Stream ---
  // The client streams requests in the following order:
  //
  // 1.  Initialization:
  //     The first message must contain
  //     [SessionConfig][google.cloud.ces.v1.BidiSessionClientMessage.config].
  //     For audio sessions, this should also include
  //     [InputAudioConfig][google.cloud.ces.v1.SessionConfig.input_audio_config]
  //     and
  //     [OutputAudioConfig][google.cloud.ces.v1.SessionConfig.output_audio_config]
  //     to define audio processing and synthesis parameters.
  //
  // 2.  Interaction:
  //     Subsequent messages stream
  //     [SessionInput][google.cloud.ces.v1.BidiSessionClientMessage.realtime_input]
  //     containing real-time user input data.
  //
  // 3.  Termination:
  //     The client should half-close the stream when there is no more user
  //     input. It should also half-close upon receiving
  //     [EndSession][google.cloud.ces.v1.BidiSessionServerMessage.end_session]
  //     or [GoAway][google.cloud.ces.v1.BidiSessionServerMessage.go_away] from
  //     the agent.
  //
  // --- Server Response Stream ---
  // For each interaction turn, the agent streams messages in the following
  // sequence:
  //
  // 1.  Speech Recognition (First N messages):
  //     Contains
  //     [RecognitionResult][google.cloud.ces.v1.BidiSessionServerMessage.recognition_result]
  //     representing the concatenated user speech segments captured so far.
  //     This is only populated for audio sessions.
  //
  // 2.  Response (Next M messages):
  //     Contains
  //     [SessionOutput][google.cloud.ces.v1.BidiSessionServerMessage.session_output]
  //     delivering the agent's response in various modalities (e.g., text,
  //     audio).
  //
  // 3.  Turn Completion (Final message of the turn):
  //     Contains
  //     [SessionOutput][google.cloud.ces.v1.BidiSessionServerMessage.session_output]
  //     with [turn_completed][google.cloud.ces.v1.SessionOutput.turn_completed]
  //     set to true. This signals the end of the current turn and includes
  //     [DiagnosticInfo][google.cloud.ces.v1.SessionOutput.diagnostic_info]
  //     with execution details.
  //
  // --- Audio Best Practices ---
  // 1.  Streaming:
  //     Stream [audio data][google.cloud.ces.v1.SessionInput.audio]
  //     **CONTINUOUSLY**, even during silence. Recommended chunk size: 40-120ms
  //     (balances latency vs. efficiency).
  //
  // 2.  Playback & Interruption:
  //     Play [audio responses][google.cloud.ces.v1.SessionOutput.audio] upon
  //     receipt. Stop playback immediately if an
  //     [InterruptionSignal][google.cloud.ces.v1.BidiSessionServerMessage.interruption_signal]
  //     is received (e.g., user barge-in or new agent response).
  rpc BidiRunSession(stream BidiSessionClientMessage)
      returns (stream BidiSessionServerMessage) {}
}

// AudioEncoding specifies the encoding format for audio data.
enum AudioEncoding {
  // Unspecified audio encoding.
  AUDIO_ENCODING_UNSPECIFIED = 0;

  // 16-bit linear PCM audio encoding.
  LINEAR16 = 1;

  // 8-bit samples that compand 14-bit audio samples using G.711 PCMU/mu-law.
  MULAW = 2;

  // 8-bit samples that compand 14-bit audio samples using G.711 PCMU/A-law.
  ALAW = 3;
}

// InputAudioConfig configures how the CES agent should interpret the incoming
// audio data.
message InputAudioConfig {
  // Required. The encoding of the input audio data.
  AudioEncoding audio_encoding = 1 [(google.api.field_behavior) = REQUIRED];

  // Required. The sample rate (in Hertz) of the input audio data.
  int32 sample_rate_hertz = 2 [(google.api.field_behavior) = REQUIRED];

  // Optional. Whether to enable noise suppression on the input audio.
  // Available values are "low", "moderate", "high", "very_high".
  string noise_suppression_level = 6 [(google.api.field_behavior) = OPTIONAL];
}

// OutputAudioConfig configures how the CES agent should synthesize outgoing
// audio responses.
message OutputAudioConfig {
  // Required. The encoding of the output audio data.
  AudioEncoding audio_encoding = 1 [(google.api.field_behavior) = REQUIRED];

  // Required. The sample rate (in Hertz) of the output audio data.
  int32 sample_rate_hertz = 2 [(google.api.field_behavior) = REQUIRED];
}

// The configuration for the session.
message SessionConfig {
  // [QueryParameters](https://cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#queryparameters)
  // to send to the remote
  // [Dialogflow](https://cloud.google.com/dialogflow/cx/docs/concept/console-conversational-agents)
  // agent when the session control is transferred to the remote agent.
  message RemoteDialogflowQueryParameters {
    // Optional. The HTTP headers to be sent as webhook_headers in
    // [QueryParameters](https://cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#queryparameters).
    map<string, string> webhook_headers = 1
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. The payload to be sent in
    // [QueryParameters](https://cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#queryparameters).
    google.protobuf.Struct payload = 2 [(google.api.field_behavior) = OPTIONAL];

    // Optional. The end user metadata to be sent in
    // [QueryParameters](https://cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#queryparameters).
    google.protobuf.Struct end_user_metadata = 3
        [(google.api.field_behavior) = OPTIONAL];
  }

  // Required. The unique identifier of the session.
  // Format:
  // `projects/{project}/locations/{location}/apps/{app}/sessions/{session}`
  string session = 1 [
    (google.api.field_behavior) = REQUIRED,
    (google.api.resource_reference) = { type: "ces.googleapis.com/Session" }
  ];

  // Optional. Configuration for processing the input audio.
  InputAudioConfig input_audio_config = 2
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. Configuration for generating the output audio.
  OutputAudioConfig output_audio_config = 3
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. The historical context of the session, including user inputs,
  // agent responses, and other messages. Typically, CES agent would manage
  // session automatically so client doesn't need to explicitly populate this
  // field. However, client can optionally override the historical contexts to
  // force the session start from certain state.
  repeated Message historical_contexts = 5
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. The entry agent to handle the session. If not specified, the
  // session will be handled by the [root
  // agent][google.cloud.ces.v1.App.root_agent] of the app. Format:
  // `projects/{project}/locations/{location}/apps/{app}/agents/{agent}`
  string entry_agent = 12 [
    (google.api.field_behavior) = OPTIONAL,
    (google.api.resource_reference) = { type: "ces.googleapis.com/Agent" }
  ];

  // Optional. The deployment of the app to use for the session.
  // Format:
  // `projects/{project}/locations/{location}/apps/{app}/deployments/{deployment}`
  string deployment = 8 [(google.api.field_behavior) = OPTIONAL];

  // Optional. The time zone of the user. If provided, the agent will use the
  // time zone for date and time related variables. Otherwise, the agent will
  // use the time zone specified in the App.time_zone_settings.
  //
  // The format is the IANA Time Zone Database time zone, e.g.
  // "America/Los_Angeles".
  string time_zone = 11 [(google.api.field_behavior) = OPTIONAL];

  // Optional. Whether to use tool fakes for the session.
  // If this field is set, the agent will attempt use tool fakes instead of
  // calling the real tools.
  bool use_tool_fakes = 14 [(google.api.field_behavior) = OPTIONAL];

  // Optional.
  // [QueryParameters](https://cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#queryparameters)
  // to send to the remote
  // [Dialogflow](https://cloud.google.com/dialogflow/cx/docs/concept/console-conversational-agents)
  // agent when the session control is transferred to the remote agent.
  RemoteDialogflowQueryParameters remote_dialogflow_query_parameters = 15
      [(google.api.field_behavior) = OPTIONAL];

  // Optional. Whether to enable streaming text outputs from the model.
  // By default, text outputs from the model are collected before sending to the
  // client.
  // NOTE: This is only supported for text (non-voice) sessions via
  // [StreamRunSession][google.cloud.ces.v1.SessionService.StreamRunSession] or
  // [BidiRunSession][google.cloud.ces.v1.SessionService.BidiRunSession].
  bool enable_text_streaming = 18 [(google.api.field_behavior) = OPTIONAL];
}

// Request for the client to execute the tools and return the execution results
// before continuing the session.
message ToolCalls {
  // Optional. The list of tool calls to execute.
  repeated ToolCall tool_calls = 1 [(google.api.field_behavior) = OPTIONAL];
}

// Execution results for the requested tool calls from the client.
message ToolResponses {
  // Optional. The list of tool execution results.
  repeated ToolResponse tool_responses = 1
      [(google.api.field_behavior) = OPTIONAL];
}

// Citations associated with the agent response.
message Citations {
  // Piece of cited information.
  message CitedChunk {
    // URI used for citation.
    string uri = 1;

    // Title of the cited document.
    string title = 2;

    // Text used for citation.
    string text = 3;
  }

  // List of cited pieces of information.
  repeated CitedChunk cited_chunks = 1;
}

// Event input.
message Event {
  // Required. The name of the event.
  string event = 1 [(google.api.field_behavior) = REQUIRED];
}

// Input for the session.
message SessionInput {
  // The type of the input.
  oneof input_type {
    // Optional. Text data from the end user.
    string text = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. DTMF digits from the end user.
    string dtmf = 6 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Audio data from the end user.
    bytes audio = 2 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Execution results for the tool calls from the client.
    ToolResponses tool_responses = 3 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Image data from the end user.
    Image image = 4 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Blob data from the end user.
    Blob blob = 7 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Contextual variables for the session, keyed by name. Only
    // variables declared in the app will be used by the CES agent.
    //
    // Unrecognized variables will still be sent to the [Dialogflow
    // agent][Agent.RemoteDialogflowAgent] as additional session parameters.
    google.protobuf.Struct variables = 5
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. Event input.
    Event event = 9 [(google.api.field_behavior) = OPTIONAL];
  }

  // Optional. A flag to indicate if the current message is a fragment of a
  // larger input in the bidi streaming session.
  //
  // When set to `true`, the agent defers processing until it receives a
  // subsequent message where `will_continue` is `false`, or until the system
  // detects an endpoint in the audio input.
  //
  // NOTE: This field does not apply to audio and DTMF inputs, as they are
  // always processed automatically based on the endpointing signal.
  bool will_continue = 8 [(google.api.field_behavior) = OPTIONAL];
}

// Output for the session.
message SessionOutput {
  // Contains execution details during the processing.
  message DiagnosticInfo {
    // List of the messages that happened during the processing.
    repeated Message messages = 1;

    // A trace of the entire request processing, represented as a root span.
    // This span can contain nested child spans for specific operations.
    Span root_span = 3;
  }

  // The type of the output.
  oneof output_type {
    // Output text from the CES agent.
    string text = 1;

    // Output audio from the CES agent.
    bytes audio = 2;

    // Request for the client to execute the tools.
    ToolCalls tool_calls = 3;

    // Citations that provide the source information for the agent's generated
    // text.
    Citations citations = 8;

    // The suggestions returned from Google Search as a result of invoking the
    // [GoogleSearchTool][google.cloud.ces.v1.GoogleSearchTool].
    GoogleSearchSuggestions google_search_suggestions = 10;

    // Indicates the session has ended.
    EndSession end_session = 9;

    // Custom payload with structured output from the CES agent.
    google.protobuf.Struct payload = 11;
  }

  // Indicates the sequential order of conversation turn to which this output
  // belongs to, starting from 1.
  int32 turn_index = 6;

  // If true, the CES agent has detected the end of the current conversation
  // turn and will provide no further output for this turn.
  bool turn_completed = 4;

  // Optional. Diagnostic information contains execution details during the
  // processing of the input. Only populated in the last SessionOutput (with
  // `turn_completed=true`) for each turn.
  DiagnosticInfo diagnostic_info = 7 [(google.api.field_behavior) = OPTIONAL];
}

// Speech recognition result for the audio input.
message RecognitionResult {
  // Optional. Concatenated user speech segments captured during the current
  // turn.
  string transcript = 1 [(google.api.field_behavior) = OPTIONAL];
}

// Indicates the agent's audio response has been interrupted. The client should
// immediately stop any current audio playback (e.g., due to user barge-in or
// a new agent response being generated).
message InterruptionSignal {
  // Whether the interruption is caused by a user barge-in event.
  bool barge_in = 1;
}

// Indicates the session has terminated, due to either successful completion
// (e.g. user says "Good bye!" ) or an agent escalation.
//
// The agent will not process any further inputs after session is terminated and
// the client should half-close and disconnect after receiving all remaining
// responses from the agent.
message EndSession {
  // Optional. Provides additional information about the end session signal,
  // such as the reason for ending the session.
  google.protobuf.Struct metadata = 1 [(google.api.field_behavior) = OPTIONAL];
}

// Indicates that the server will disconnect soon and the client should
// half-close and restart the connection.
message GoAway {}

// Request message for
// [SessionService.RunSession][google.cloud.ces.v1.SessionService.RunSession].
message RunSessionRequest {
  // Required. The configuration for the session.
  SessionConfig config = 1 [(google.api.field_behavior) = REQUIRED];

  // Required. Inputs for the session.
  repeated SessionInput inputs = 3 [(google.api.field_behavior) = REQUIRED];
}

// Response message for
// [SessionService.RunSession][google.cloud.ces.v1.SessionService.RunSession].
message RunSessionResponse {
  // Outputs for the session.
  repeated SessionOutput outputs = 1;
}

// The top-level message sent by the client for the
// [SessionService.BidiRunSession][google.cloud.ces.v1.SessionService.BidiRunSession]
// method.
message BidiSessionClientMessage {
  // The type of the message.
  oneof message_type {
    // Optional. The initial config message for the session.
    SessionConfig config = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Realtime input for the session.
    SessionInput realtime_input = 2 [(google.api.field_behavior) = OPTIONAL];
  }
}

// The top-level message returned from
// [SessionService.BidiRunSession][google.cloud.ces.v1.SessionService.BidiRunSession]
// method.
message BidiSessionServerMessage {
  // The type of the message.
  oneof message_type {
    // Optional. Processing result from the CES agent.
    SessionOutput session_output = 1 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Realtime speech recognition result for the audio input.
    RecognitionResult recognition_result = 2
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. Indicates the agent's audio response has been interrupted.
    InterruptionSignal interruption_signal = 3
        [(google.api.field_behavior) = OPTIONAL];

    // Optional. Indicates that the session has ended.
    EndSession end_session = 5 [(google.api.field_behavior) = OPTIONAL];

    // Optional. Indicates that the server will disconnect soon and the client
    // should half-close and restart the connection.
    GoAway go_away = 6 [(google.api.field_behavior) = OPTIONAL];
  }
}