diff --git a/src/Runner.Worker/Dap/DapMessages.cs b/src/Runner.Worker/Dap/DapMessages.cs
new file mode 100644
index 000000000..bf8685981
--- /dev/null
+++ b/src/Runner.Worker/Dap/DapMessages.cs
@@ -0,0 +1,1134 @@
+using System.Collections.Generic;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace GitHub.Runner.Worker.Dap
+{
+    public enum DapCommand
+    {
+        Continue,
+        Next,
+        StepIn,
+        StepOut,
+        Disconnect
+    }
+
+    /// <summary>
+    /// Base class of requests, responses, and events per DAP specification.
+    /// </summary>
+    public class ProtocolMessage
+    {
+        /// <summary>
+        /// Sequence number of the message (also known as message ID).
+        /// The seq for the first message sent by a client or debug adapter is 1,
+        /// and for each subsequent message is 1 greater than the previous message.
+        /// </summary>
+        [JsonProperty("seq")]
+        public int Seq { get; set; }
+
+        /// <summary>
+        /// Message type: 'request', 'response', 'event'
+        /// </summary>
+        [JsonProperty("type")]
+        public string Type { get; set; }
+    }
+
+    /// <summary>
+    /// A client or debug adapter initiated request.
+    /// </summary>
+    public class Request : ProtocolMessage
+    {
+        /// <summary>
+        /// The command to execute.
+        /// </summary>
+        [JsonProperty("command")]
+        public string Command { get; set; }
+
+        /// <summary>
+        /// Object containing arguments for the command.
+        /// Using JObject for flexibility with different argument types.
+        /// </summary>
+        [JsonProperty("arguments")]
+        public JObject Arguments { get; set; }
+    }
+
+    /// <summary>
+    /// Response for a request.
+    /// </summary>
+    public class Response : ProtocolMessage
+    {
+        /// <summary>
+        /// Sequence number of the corresponding request.
+        /// </summary>
+        [JsonProperty("request_seq")]
+        public int RequestSeq { get; set; }
+
+        /// <summary>
+        /// Outcome of the request. If true, the request was successful.
+        /// </summary>
+        [JsonProperty("success")]
+        public bool Success { get; set; }
+
+        /// <summary>
+        /// The command requested.
+        /// </summary>
+        [JsonProperty("command")]
+        public string Command { get; set; }
+
+        /// <summary>
+        /// Contains the raw error in short form if success is false.
+        /// </summary>
+        [JsonProperty("message", NullValueHandling = NullValueHandling.Ignore)]
+        public string Message { get; set; }
+
+        /// <summary>
+        /// Contains request result if success is true and error details if success is false.
+        /// </summary>
+        [JsonProperty("body", NullValueHandling = NullValueHandling.Ignore)]
+        public object Body { get; set; }
+    }
+
+    /// <summary>
+    /// A debug adapter initiated event.
+    /// </summary>
+    public class Event : ProtocolMessage
+    {
+        public Event()
+        {
+            Type = "event";
+        }
+
+        /// <summary>
+        /// Type of event.
+        /// </summary>
+        [JsonProperty("event")]
+        public string EventType { get; set; }
+
+        /// <summary>
+        /// Event-specific information.
+        /// </summary>
+        [JsonProperty("body", NullValueHandling = NullValueHandling.Ignore)]
+        public object Body { get; set; }
+    }
+
+    #region Initialize Request/Response
+
+    /// <summary>
+    /// Arguments for 'initialize' request.
+    /// </summary>
+    public class InitializeRequestArguments
+    {
+        /// <summary>
+        /// The ID of the client using this adapter.
+        /// </summary>
+        [JsonProperty("clientID")]
+        public string ClientId { get; set; }
+
+        /// <summary>
+        /// The human-readable name of the client using this adapter.
+        /// </summary>
+        [JsonProperty("clientName")]
+        public string ClientName { get; set; }
+
+        /// <summary>
+        /// The ID of the debug adapter.
+        /// </summary>
+        [JsonProperty("adapterID")]
+        public string AdapterId { get; set; }
+
+        /// <summary>
+        /// The ISO-639 locale of the client using this adapter, e.g. en-US or de-CH.
+        /// </summary>
+        [JsonProperty("locale")]
+        public string Locale { get; set; }
+
+        /// <summary>
+        /// If true all line numbers are 1-based (default).
+        /// </summary>
+        [JsonProperty("linesStartAt1")]
+        public bool LinesStartAt1 { get; set; } = true;
+
+        /// <summary>
+        /// If true all column numbers are 1-based (default).
+        /// </summary>
+        [JsonProperty("columnsStartAt1")]
+        public bool ColumnsStartAt1 { get; set; } = true;
+
+        /// <summary>
+        /// Determines in what format paths are specified. The default is 'path'.
+        /// </summary>
+        [JsonProperty("pathFormat")]
+        public string PathFormat { get; set; } = "path";
+
+        /// <summary>
+        /// Client supports the type attribute for variables.
+        /// </summary>
+        [JsonProperty("supportsVariableType")]
+        public bool SupportsVariableType { get; set; }
+
+        /// <summary>
+        /// Client supports the paging of variables.
+        /// </summary>
+        [JsonProperty("supportsVariablePaging")]
+        public bool SupportsVariablePaging { get; set; }
+
+        /// <summary>
+        /// Client supports the runInTerminal request.
+        /// </summary>
+        [JsonProperty("supportsRunInTerminalRequest")]
+        public bool SupportsRunInTerminalRequest { get; set; }
+
+        /// <summary>
+        /// Client supports memory references.
+        /// </summary>
+        [JsonProperty("supportsMemoryReferences")]
+        public bool SupportsMemoryReferences { get; set; }
+
+        /// <summary>
+        /// Client supports progress reporting.
+        /// </summary>
+        [JsonProperty("supportsProgressReporting")]
+        public bool SupportsProgressReporting { get; set; }
+    }
+
+    /// <summary>
+    /// Debug adapter capabilities returned in InitializeResponse.
+    /// </summary>
+    public class Capabilities
+    {
+        /// <summary>
+        /// The debug adapter supports the configurationDone request.
+        /// </summary>
+        [JsonProperty("supportsConfigurationDoneRequest")]
+        public bool SupportsConfigurationDoneRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports function breakpoints.
+        /// </summary>
+        [JsonProperty("supportsFunctionBreakpoints")]
+        public bool SupportsFunctionBreakpoints { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports conditional breakpoints.
+        /// </summary>
+        [JsonProperty("supportsConditionalBreakpoints")]
+        public bool SupportsConditionalBreakpoints { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports a (side effect free) evaluate request for data hovers.
+        /// </summary>
+        [JsonProperty("supportsEvaluateForHovers")]
+        public bool SupportsEvaluateForHovers { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports stepping back via the stepBack and reverseContinue requests.
+        /// </summary>
+        [JsonProperty("supportsStepBack")]
+        public bool SupportsStepBack { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports setting a variable to a value.
+        /// </summary>
+        [JsonProperty("supportsSetVariable")]
+        public bool SupportsSetVariable { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports restarting a frame.
+        /// </summary>
+        [JsonProperty("supportsRestartFrame")]
+        public bool SupportsRestartFrame { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the gotoTargets request.
+        /// </summary>
+        [JsonProperty("supportsGotoTargetsRequest")]
+        public bool SupportsGotoTargetsRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the stepInTargets request.
+        /// </summary>
+        [JsonProperty("supportsStepInTargetsRequest")]
+        public bool SupportsStepInTargetsRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the completions request.
+        /// </summary>
+        [JsonProperty("supportsCompletionsRequest")]
+        public bool SupportsCompletionsRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the modules request.
+        /// </summary>
+        [JsonProperty("supportsModulesRequest")]
+        public bool SupportsModulesRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the terminate request.
+        /// </summary>
+        [JsonProperty("supportsTerminateRequest")]
+        public bool SupportsTerminateRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the terminateDebuggee attribute on the disconnect request.
+        /// </summary>
+        [JsonProperty("supportTerminateDebuggee")]
+        public bool SupportTerminateDebuggee { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the delayed loading of parts of the stack.
+        /// </summary>
+        [JsonProperty("supportsDelayedStackTraceLoading")]
+        public bool SupportsDelayedStackTraceLoading { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the loadedSources request.
+        /// </summary>
+        [JsonProperty("supportsLoadedSourcesRequest")]
+        public bool SupportsLoadedSourcesRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports sending progress reporting events.
+        /// </summary>
+        [JsonProperty("supportsProgressReporting")]
+        public bool SupportsProgressReporting { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the runInTerminal request.
+        /// </summary>
+        [JsonProperty("supportsRunInTerminalRequest")]
+        public bool SupportsRunInTerminalRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports the cancel request.
+        /// </summary>
+        [JsonProperty("supportsCancelRequest")]
+        public bool SupportsCancelRequest { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports exception options.
+        /// </summary>
+        [JsonProperty("supportsExceptionOptions")]
+        public bool SupportsExceptionOptions { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports value formatting options.
+        /// </summary>
+        [JsonProperty("supportsValueFormattingOptions")]
+        public bool SupportsValueFormattingOptions { get; set; }
+
+        /// <summary>
+        /// The debug adapter supports exception info request.
+        /// </summary>
+        [JsonProperty("supportsExceptionInfoRequest")]
+        public bool SupportsExceptionInfoRequest { get; set; }
+    }
+
+    #endregion
+
+    #region Attach Request
+
+    /// <summary>
+    /// Arguments for 'attach' request. Additional attributes are implementation specific.
+    /// </summary>
+    public class AttachRequestArguments
+    {
+        /// <summary>
+        /// Arbitrary data from the previous, restarted session.
+        /// </summary>
+        [JsonProperty("__restart", NullValueHandling = NullValueHandling.Ignore)]
+        public object Restart { get; set; }
+    }
+
+    #endregion
+
+    #region Disconnect Request
+
+    /// <summary>
+    /// Arguments for 'disconnect' request.
+    /// </summary>
+    public class DisconnectRequestArguments
+    {
+        /// <summary>
+        /// A value of true indicates that this disconnect request is part of a restart sequence.
+        /// </summary>
+        [JsonProperty("restart")]
+        public bool Restart { get; set; }
+
+        /// <summary>
+        /// Indicates whether the debuggee should be terminated when the debugger is disconnected.
+        /// </summary>
+        [JsonProperty("terminateDebuggee")]
+        public bool TerminateDebuggee { get; set; }
+
+        /// <summary>
+        /// Indicates whether the debuggee should stay suspended when the debugger is disconnected.
+        /// </summary>
+        [JsonProperty("suspendDebuggee")]
+        public bool SuspendDebuggee { get; set; }
+    }
+
+    #endregion
+
+    #region Threads Request/Response
+
+    /// <summary>
+    /// A Thread in DAP represents a unit of execution.
+    /// For Actions runner, we have a single thread representing the job.
+    /// </summary>
+    public class Thread
+    {
+        /// <summary>
+        /// Unique identifier for the thread.
+        /// </summary>
+        [JsonProperty("id")]
+        public int Id { get; set; }
+
+        /// <summary>
+        /// The name of the thread.
+        /// </summary>
+        [JsonProperty("name")]
+        public string Name { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'threads' request.
+    /// </summary>
+    public class ThreadsResponseBody
+    {
+        /// <summary>
+        /// All threads.
+        /// </summary>
+        [JsonProperty("threads")]
+        public List<Thread> Threads { get; set; } = new List<Thread>();
+    }
+
+    #endregion
+
+    #region StackTrace Request/Response
+
+    /// <summary>
+    /// Arguments for 'stackTrace' request.
+    /// </summary>
+    public class StackTraceArguments
+    {
+        /// <summary>
+        /// Retrieve the stacktrace for this thread.
+        /// </summary>
+        [JsonProperty("threadId")]
+        public int ThreadId { get; set; }
+
+        /// <summary>
+        /// The index of the first frame to return.
+        /// </summary>
+        [JsonProperty("startFrame")]
+        public int? StartFrame { get; set; }
+
+        /// <summary>
+        /// The maximum number of frames to return.
+        /// </summary>
+        [JsonProperty("levels")]
+        public int? Levels { get; set; }
+    }
+
+    /// <summary>
+    /// A Stackframe contains the source location.
+    /// For Actions runner, each step is a stack frame.
+    /// </summary>
+    public class StackFrame
+    {
+        /// <summary>
+        /// An identifier for the stack frame.
+        /// </summary>
+        [JsonProperty("id")]
+        public int Id { get; set; }
+
+        /// <summary>
+        /// The name of the stack frame, typically a method name.
+        /// For Actions, this is the step display name.
+        /// </summary>
+        [JsonProperty("name")]
+        public string Name { get; set; }
+
+        /// <summary>
+        /// The source of the frame.
+        /// </summary>
+        [JsonProperty("source", NullValueHandling = NullValueHandling.Ignore)]
+        public Source Source { get; set; }
+
+        /// <summary>
+        /// The line within the source of the frame.
+        /// </summary>
+        [JsonProperty("line")]
+        public int Line { get; set; }
+
+        /// <summary>
+        /// Start position of the range covered by the stack frame.
+        /// </summary>
+        [JsonProperty("column")]
+        public int Column { get; set; }
+
+        /// <summary>
+        /// The end line of the range covered by the stack frame.
+        /// </summary>
+        [JsonProperty("endLine", NullValueHandling = NullValueHandling.Ignore)]
+        public int? EndLine { get; set; }
+
+        /// <summary>
+        /// End position of the range covered by the stack frame.
+        /// </summary>
+        [JsonProperty("endColumn", NullValueHandling = NullValueHandling.Ignore)]
+        public int? EndColumn { get; set; }
+
+        /// <summary>
+        /// A hint for how to present this frame in the UI.
+        /// </summary>
+        [JsonProperty("presentationHint", NullValueHandling = NullValueHandling.Ignore)]
+        public string PresentationHint { get; set; }
+    }
+
+    /// <summary>
+    /// A Source is a descriptor for source code.
+    /// </summary>
+    public class Source
+    {
+        /// <summary>
+        /// The short name of the source.
+        /// </summary>
+        [JsonProperty("name", NullValueHandling = NullValueHandling.Ignore)]
+        public string Name { get; set; }
+
+        /// <summary>
+        /// The path of the source to be shown in the UI.
+        /// </summary>
+        [JsonProperty("path", NullValueHandling = NullValueHandling.Ignore)]
+        public string Path { get; set; }
+
+        /// <summary>
+        /// If the value > 0 the contents of the source must be retrieved through
+        /// the 'source' request (even if a path is specified).
+        /// </summary>
+        [JsonProperty("sourceReference", NullValueHandling = NullValueHandling.Ignore)]
+        public int? SourceReference { get; set; }
+
+        /// <summary>
+        /// A hint for how to present the source in the UI.
+        /// </summary>
+        [JsonProperty("presentationHint", NullValueHandling = NullValueHandling.Ignore)]
+        public string PresentationHint { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'stackTrace' request.
+    /// </summary>
+    public class StackTraceResponseBody
+    {
+        /// <summary>
+        /// The frames of the stack frame.
+        /// </summary>
+        [JsonProperty("stackFrames")]
+        public List<StackFrame> StackFrames { get; set; } = new List<StackFrame>();
+
+        /// <summary>
+        /// The total number of frames available in the stack.
+        /// </summary>
+        [JsonProperty("totalFrames", NullValueHandling = NullValueHandling.Ignore)]
+        public int? TotalFrames { get; set; }
+    }
+
+    #endregion
+
+    #region Scopes Request/Response
+
+    /// <summary>
+    /// Arguments for 'scopes' request.
+    /// </summary>
+    public class ScopesArguments
+    {
+        /// <summary>
+        /// Retrieve the scopes for the stack frame identified by frameId.
+        /// </summary>
+        [JsonProperty("frameId")]
+        public int FrameId { get; set; }
+    }
+
+    /// <summary>
+    /// A Scope is a named container for variables.
+    /// For Actions runner, scopes are: github, env, inputs, steps, secrets, runner, job
+    /// </summary>
+    public class Scope
+    {
+        /// <summary>
+        /// Name of the scope such as 'Arguments', 'Locals', or 'Registers'.
+        /// For Actions: 'github', 'env', 'inputs', 'steps', 'secrets', 'runner', 'job'
+        /// </summary>
+        [JsonProperty("name")]
+        public string Name { get; set; }
+
+        /// <summary>
+        /// A hint for how to present this scope in the UI.
+        /// </summary>
+        [JsonProperty("presentationHint", NullValueHandling = NullValueHandling.Ignore)]
+        public string PresentationHint { get; set; }
+
+        /// <summary>
+        /// The variables of this scope can be retrieved by passing the value of
+        /// variablesReference to the variables request.
+        /// </summary>
+        [JsonProperty("variablesReference")]
+        public int VariablesReference { get; set; }
+
+        /// <summary>
+        /// The number of named variables in this scope.
+        /// </summary>
+        [JsonProperty("namedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? NamedVariables { get; set; }
+
+        /// <summary>
+        /// The number of indexed variables in this scope.
+        /// </summary>
+        [JsonProperty("indexedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? IndexedVariables { get; set; }
+
+        /// <summary>
+        /// If true, the number of variables in this scope is large or expensive to retrieve.
+        /// </summary>
+        [JsonProperty("expensive")]
+        public bool Expensive { get; set; }
+
+        /// <summary>
+        /// The source for this scope.
+        /// </summary>
+        [JsonProperty("source", NullValueHandling = NullValueHandling.Ignore)]
+        public Source Source { get; set; }
+
+        /// <summary>
+        /// The start line of the range covered by this scope.
+        /// </summary>
+        [JsonProperty("line", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Line { get; set; }
+
+        /// <summary>
+        /// Start position of the range covered by this scope.
+        /// </summary>
+        [JsonProperty("column", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Column { get; set; }
+
+        /// <summary>
+        /// The end line of the range covered by this scope.
+        /// </summary>
+        [JsonProperty("endLine", NullValueHandling = NullValueHandling.Ignore)]
+        public int? EndLine { get; set; }
+
+        /// <summary>
+        /// End position of the range covered by this scope.
+        /// </summary>
+        [JsonProperty("endColumn", NullValueHandling = NullValueHandling.Ignore)]
+        public int? EndColumn { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'scopes' request.
+    /// </summary>
+    public class ScopesResponseBody
+    {
+        /// <summary>
+        /// The scopes of the stack frame.
+        /// </summary>
+        [JsonProperty("scopes")]
+        public List<Scope> Scopes { get; set; } = new List<Scope>();
+    }
+
+    #endregion
+
+    #region Variables Request/Response
+
+    /// <summary>
+    /// Arguments for 'variables' request.
+    /// </summary>
+    public class VariablesArguments
+    {
+        /// <summary>
+        /// The variable for which to retrieve its children.
+        /// </summary>
+        [JsonProperty("variablesReference")]
+        public int VariablesReference { get; set; }
+
+        /// <summary>
+        /// Filter to limit the child variables to either named or indexed.
+        /// </summary>
+        [JsonProperty("filter", NullValueHandling = NullValueHandling.Ignore)]
+        public string Filter { get; set; }
+
+        /// <summary>
+        /// The index of the first variable to return.
+        /// </summary>
+        [JsonProperty("start", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Start { get; set; }
+
+        /// <summary>
+        /// The number of variables to return.
+        /// </summary>
+        [JsonProperty("count", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Count { get; set; }
+    }
+
+    /// <summary>
+    /// A Variable is a name/value pair.
+    /// </summary>
+    public class Variable
+    {
+        /// <summary>
+        /// The variable's name.
+        /// </summary>
+        [JsonProperty("name")]
+        public string Name { get; set; }
+
+        /// <summary>
+        /// The variable's value.
+        /// </summary>
+        [JsonProperty("value")]
+        public string Value { get; set; }
+
+        /// <summary>
+        /// The type of the variable's value.
+        /// </summary>
+        [JsonProperty("type", NullValueHandling = NullValueHandling.Ignore)]
+        public string Type { get; set; }
+
+        /// <summary>
+        /// If variablesReference is > 0, the variable is structured and its children
+        /// can be retrieved by passing variablesReference to the variables request.
+        /// </summary>
+        [JsonProperty("variablesReference")]
+        public int VariablesReference { get; set; }
+
+        /// <summary>
+        /// The number of named child variables.
+        /// </summary>
+        [JsonProperty("namedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? NamedVariables { get; set; }
+
+        /// <summary>
+        /// The number of indexed child variables.
+        /// </summary>
+        [JsonProperty("indexedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? IndexedVariables { get; set; }
+
+        /// <summary>
+        /// A memory reference to a location appropriate for this result.
+        /// </summary>
+        [JsonProperty("memoryReference", NullValueHandling = NullValueHandling.Ignore)]
+        public string MemoryReference { get; set; }
+
+        /// <summary>
+        /// A reference that allows the client to request the location where the
+        /// variable's value is declared.
+        /// </summary>
+        [JsonProperty("declarationLocationReference", NullValueHandling = NullValueHandling.Ignore)]
+        public int? DeclarationLocationReference { get; set; }
+
+        /// <summary>
+        /// The evaluatable name of this variable which can be passed to the evaluate
+        /// request to fetch the variable's value.
+        /// </summary>
+        [JsonProperty("evaluateName", NullValueHandling = NullValueHandling.Ignore)]
+        public string EvaluateName { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'variables' request.
+    /// </summary>
+    public class VariablesResponseBody
+    {
+        /// <summary>
+        /// All (or a range) of variables for the given variable reference.
+        /// </summary>
+        [JsonProperty("variables")]
+        public List<Variable> Variables { get; set; } = new List<Variable>();
+    }
+
+    #endregion
+
+    #region Continue Request/Response
+
+    /// <summary>
+    /// Arguments for 'continue' request.
+    /// </summary>
+    public class ContinueArguments
+    {
+        /// <summary>
+        /// Specifies the active thread. If the debug adapter supports single thread
+        /// execution, setting this will resume only the specified thread.
+        /// </summary>
+        [JsonProperty("threadId")]
+        public int ThreadId { get; set; }
+
+        /// <summary>
+        /// If this flag is true, execution is resumed only for the thread with given
+        /// threadId. If false, all threads are resumed.
+        /// </summary>
+        [JsonProperty("singleThread")]
+        public bool SingleThread { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'continue' request.
+    /// </summary>
+    public class ContinueResponseBody
+    {
+        /// <summary>
+        /// If true, all threads are resumed. If false, only the thread with the given
+        /// threadId is resumed.
+        /// </summary>
+        [JsonProperty("allThreadsContinued")]
+        public bool AllThreadsContinued { get; set; } = true;
+    }
+
+    #endregion
+
+    #region Next Request
+
+    /// <summary>
+    /// Arguments for 'next' request.
+    /// </summary>
+    public class NextArguments
+    {
+        /// <summary>
+        /// Specifies the thread for which to resume execution for one step.
+        /// </summary>
+        [JsonProperty("threadId")]
+        public int ThreadId { get; set; }
+
+        /// <summary>
+        /// Stepping granularity.
+        /// </summary>
+        [JsonProperty("granularity", NullValueHandling = NullValueHandling.Ignore)]
+        public string Granularity { get; set; }
+
+        /// <summary>
+        /// If this flag is true, all other suspended threads are not resumed.
+        /// </summary>
+        [JsonProperty("singleThread")]
+        public bool SingleThread { get; set; }
+    }
+
+    #endregion
+
+    #region Evaluate Request/Response
+
+    /// <summary>
+    /// Arguments for 'evaluate' request.
+    /// </summary>
+    public class EvaluateArguments
+    {
+        /// <summary>
+        /// The expression to evaluate.
+        /// </summary>
+        [JsonProperty("expression")]
+        public string Expression { get; set; }
+
+        /// <summary>
+        /// Evaluate the expression in the scope of this stack frame.
+        /// </summary>
+        [JsonProperty("frameId", NullValueHandling = NullValueHandling.Ignore)]
+        public int? FrameId { get; set; }
+
+        /// <summary>
+        /// The context in which the evaluate request is used.
+        /// Values: 'watch', 'repl', 'hover', 'clipboard', 'variables'
+        /// </summary>
+        [JsonProperty("context", NullValueHandling = NullValueHandling.Ignore)]
+        public string Context { get; set; }
+    }
+
+    /// <summary>
+    /// Response body for 'evaluate' request.
+    /// </summary>
+    public class EvaluateResponseBody
+    {
+        /// <summary>
+        /// The result of the evaluate request.
+        /// </summary>
+        [JsonProperty("result")]
+        public string Result { get; set; }
+
+        /// <summary>
+        /// The type of the evaluate result.
+        /// </summary>
+        [JsonProperty("type", NullValueHandling = NullValueHandling.Ignore)]
+        public string Type { get; set; }
+
+        /// <summary>
+        /// If variablesReference is > 0, the evaluate result is structured.
+        /// </summary>
+        [JsonProperty("variablesReference")]
+        public int VariablesReference { get; set; }
+
+        /// <summary>
+        /// The number of named child variables.
+        /// </summary>
+        [JsonProperty("namedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? NamedVariables { get; set; }
+
+        /// <summary>
+        /// The number of indexed child variables.
+        /// </summary>
+        [JsonProperty("indexedVariables", NullValueHandling = NullValueHandling.Ignore)]
+        public int? IndexedVariables { get; set; }
+
+        /// <summary>
+        /// A memory reference to a location appropriate for this result.
+        /// </summary>
+        [JsonProperty("memoryReference", NullValueHandling = NullValueHandling.Ignore)]
+        public string MemoryReference { get; set; }
+    }
+
+    #endregion
+
+    #region Events
+
+    /// <summary>
+    /// Body for 'stopped' event.
+    /// The event indicates that the execution of the debuggee has stopped.
+    /// </summary>
+    public class StoppedEventBody
+    {
+        /// <summary>
+        /// The reason for the event. For backward compatibility this string is shown
+        /// in the UI if the description attribute is missing.
+        /// Values: 'step', 'breakpoint', 'exception', 'pause', 'entry', 'goto',
+        /// 'function breakpoint', 'data breakpoint', 'instruction breakpoint'
+        /// </summary>
+        [JsonProperty("reason")]
+        public string Reason { get; set; }
+
+        /// <summary>
+        /// The full reason for the event, e.g. 'Paused on exception'.
+        /// This string is shown in the UI as is and can be translated.
+        /// </summary>
+        [JsonProperty("description", NullValueHandling = NullValueHandling.Ignore)]
+        public string Description { get; set; }
+
+        /// <summary>
+        /// The thread which was stopped.
+        /// </summary>
+        [JsonProperty("threadId", NullValueHandling = NullValueHandling.Ignore)]
+        public int? ThreadId { get; set; }
+
+        /// <summary>
+        /// A value of true hints to the client that this event should not change the focus.
+        /// </summary>
+        [JsonProperty("preserveFocusHint", NullValueHandling = NullValueHandling.Ignore)]
+        public bool? PreserveFocusHint { get; set; }
+
+        /// <summary>
+        /// Additional information. E.g. if reason is 'exception', text contains the
+        /// exception name.
+        /// </summary>
+        [JsonProperty("text", NullValueHandling = NullValueHandling.Ignore)]
+        public string Text { get; set; }
+
+        /// <summary>
+        /// If allThreadsStopped is true, a debug adapter can announce that all threads
+        /// have stopped.
+        /// </summary>
+        [JsonProperty("allThreadsStopped", NullValueHandling = NullValueHandling.Ignore)]
+        public bool? AllThreadsStopped { get; set; }
+
+        /// <summary>
+        /// Ids of the breakpoints that triggered the event.
+        /// </summary>
+        [JsonProperty("hitBreakpointIds", NullValueHandling = NullValueHandling.Ignore)]
+        public List<int> HitBreakpointIds { get; set; }
+    }
+
+    /// <summary>
+    /// Body for 'continued' event.
+    /// The event indicates that the execution of the debuggee has continued.
+    /// </summary>
+    public class ContinuedEventBody
+    {
+        /// <summary>
+        /// The thread which was continued.
+        /// </summary>
+        [JsonProperty("threadId")]
+        public int ThreadId { get; set; }
+
+        /// <summary>
+        /// If true, all threads have been resumed.
+        /// </summary>
+        [JsonProperty("allThreadsContinued", NullValueHandling = NullValueHandling.Ignore)]
+        public bool? AllThreadsContinued { get; set; }
+    }
+
+    /// <summary>
+    /// Body for 'terminated' event.
+    /// The event indicates that debugging of the debuggee has terminated.
+    /// </summary>
+    public class TerminatedEventBody
+    {
+        /// <summary>
+        /// A debug adapter may set restart to true to request that the client
+        /// restarts the session.
+        /// </summary>
+        [JsonProperty("restart", NullValueHandling = NullValueHandling.Ignore)]
+        public object Restart { get; set; }
+    }
+
+    /// <summary>
+    /// Body for 'output' event.
+    /// The event indicates that the target has produced some output.
+    /// </summary>
+    public class OutputEventBody
+    {
+        /// <summary>
+        /// The output category. If not specified, 'console' is assumed.
+        /// Values: 'console', 'important', 'stdout', 'stderr', 'telemetry'
+        /// </summary>
+        [JsonProperty("category", NullValueHandling = NullValueHandling.Ignore)]
+        public string Category { get; set; }
+
+        /// <summary>
+        /// The output to report.
+        /// </summary>
+        [JsonProperty("output")]
+        public string Output { get; set; }
+
+        /// <summary>
+        /// Support for keeping an output log organized by grouping related messages.
+        /// Values: 'start', 'startCollapsed', 'end'
+        /// </summary>
+        [JsonProperty("group", NullValueHandling = NullValueHandling.Ignore)]
+        public string Group { get; set; }
+
+        /// <summary>
+        /// If variablesReference is > 0, the output contains objects which can be
+        /// retrieved by passing variablesReference to the variables request.
+        /// </summary>
+        [JsonProperty("variablesReference", NullValueHandling = NullValueHandling.Ignore)]
+        public int? VariablesReference { get; set; }
+
+        /// <summary>
+        /// The source location where the output was produced.
+        /// </summary>
+        [JsonProperty("source", NullValueHandling = NullValueHandling.Ignore)]
+        public Source Source { get; set; }
+
+        /// <summary>
+        /// The source location's line where the output was produced.
+        /// </summary>
+        [JsonProperty("line", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Line { get; set; }
+
+        /// <summary>
+        /// The position in line where the output was produced.
+        /// </summary>
+        [JsonProperty("column", NullValueHandling = NullValueHandling.Ignore)]
+        public int? Column { get; set; }
+
+        /// <summary>
+        /// Additional data to report.
+        /// </summary>
+        [JsonProperty("data", NullValueHandling = NullValueHandling.Ignore)]
+        public object Data { get; set; }
+    }
+
+    /// <summary>
+    /// Body for 'thread' event.
+    /// The event indicates that a thread has started or exited.
+    /// </summary>
+    public class ThreadEventBody
+    {
+        /// <summary>
+        /// The reason for the event.
+        /// Values: 'started', 'exited'
+        /// </summary>
+        [JsonProperty("reason")]
+        public string Reason { get; set; }
+
+        /// <summary>
+        /// The identifier of the thread.
+        /// </summary>
+        [JsonProperty("threadId")]
+        public int ThreadId { get; set; }
+    }
+
+    /// <summary>
+    /// Body for 'exited' event.
+    /// The event indicates that the debuggee has exited and returns its exit code.
+    /// </summary>
+    public class ExitedEventBody
+    {
+        /// <summary>
+        /// The exit code returned from the debuggee.
+        /// </summary>
+        [JsonProperty("exitCode")]
+        public int ExitCode { get; set; }
+    }
+
+    #endregion
+
+    #region Error Response
+
+    /// <summary>
+    /// A structured error message.
+    /// </summary>
+    public class Message
+    {
+        /// <summary>
+        /// Unique identifier for the message.
+        /// </summary>
+        [JsonProperty("id")]
+        public int Id { get; set; }
+
+        /// <summary>
+        /// A format string for the message.
+        /// </summary>
+        [JsonProperty("format")]
+        public string Format { get; set; }
+
+        /// <summary>
+        /// An object used as a dictionary for looking up the variables in the format string.
+        /// </summary>
+        [JsonProperty("variables", NullValueHandling = NullValueHandling.Ignore)]
+        public Dictionary<string, string> Variables { get; set; }
+
+        /// <summary>
+        /// If true send to telemetry.
+        /// </summary>
+        [JsonProperty("sendTelemetry", NullValueHandling = NullValueHandling.Ignore)]
+        public bool? SendTelemetry { get; set; }
+
+        /// <summary>
+        /// If true show user.
+        /// </summary>
+        [JsonProperty("showUser", NullValueHandling = NullValueHandling.Ignore)]
+        public bool? ShowUser { get; set; }
+
+        /// <summary>
+        /// A url where additional information about this message can be found.
+        /// </summary>
+        [JsonProperty("url", NullValueHandling = NullValueHandling.Ignore)]
+        public string Url { get; set; }
+
+        /// <summary>
+        /// A label that is presented to the user as the UI for opening the url.
+        /// </summary>
+        [JsonProperty("urlLabel", NullValueHandling = NullValueHandling.Ignore)]
+        public string UrlLabel { get; set; }
+    }
+
+    /// <summary>
+    /// Body for error responses.
+    /// </summary>
+    public class ErrorResponseBody
+    {
+        /// <summary>
+        /// A structured error message.
+        /// </summary>
+        [JsonProperty("error", NullValueHandling = NullValueHandling.Ignore)]
+        public Message Error { get; set; }
+    }
+
+    #endregion
+}
diff --git a/src/Runner.Worker/Dap/IDapDebugSession.cs b/src/Runner.Worker/Dap/IDapDebugSession.cs
new file mode 100644
index 000000000..5a45d49da
--- /dev/null
+++ b/src/Runner.Worker/Dap/IDapDebugSession.cs
@@ -0,0 +1,32 @@
+using System.Threading;
+using System.Threading.Tasks;
+using GitHub.Runner.Common;
+
+namespace GitHub.Runner.Worker.Dap
+{
+    public enum DapSessionState
+    {
+        WaitingForConnection,
+        Initializing,
+        Ready,
+        Paused,
+        Running,
+        Terminated
+    }
+
+    [ServiceLocator(Default = typeof(DapDebugSession))]
+    public interface IDapDebugSession : IRunnerService
+    {
+        bool IsActive { get; }
+        DapSessionState State { get; }
+        void SetDapServer(IDapServer server);
+        Task WaitForHandshakeAsync(CancellationToken cancellationToken);
+        Task OnStepStartingAsync(IStep step, IExecutionContext jobContext, bool isFirstStep, CancellationToken cancellationToken);
+        void OnStepCompleted(IStep step);
+        void OnJobCompleted();
+        void CancelSession();
+        void HandleClientConnected();
+        void HandleClientDisconnected();
+        Task HandleMessageAsync(string messageJson, CancellationToken cancellationToken);
+    }
+}
diff --git a/src/Runner.Worker/Dap/IDapServer.cs b/src/Runner.Worker/Dap/IDapServer.cs
new file mode 100644
index 000000000..a5b879360
--- /dev/null
+++ b/src/Runner.Worker/Dap/IDapServer.cs
@@ -0,0 +1,18 @@
+using System.Threading;
+using System.Threading.Tasks;
+using GitHub.Runner.Common;
+
+namespace GitHub.Runner.Worker.Dap
+{
+    [ServiceLocator(Default = typeof(DapServer))]
+    public interface IDapServer : IRunnerService
+    {
+        void SetSession(IDapDebugSession session);
+        Task StartAsync(int port, CancellationToken cancellationToken);
+        Task WaitForConnectionAsync(CancellationToken cancellationToken);
+        Task StopAsync();
+        void SendMessage(ProtocolMessage message);
+        void SendEvent(Event evt);
+        void SendResponse(Response response);
+    }
+}