go

Copilot CLI SDK for Go

A Go SDK for programmatic access to the GitHub Copilot CLI.

Note: This SDK is in public preview and may change in breaking ways.

Installation

go get github.com/github/copilot-sdk/go

Run the Sample

Try the interactive chat sample (from the repo root):

cd go/samples
go run chat.go

The manual permission/tool-result resume sample can be run from the same directory:

go run ./manual_tool_resume

Quick Start

package main

import (
	"context"
    "fmt"
    "log"

    copilot "github.com/github/copilot-sdk/go"
)

func main() {
    // Create client
    client := copilot.NewClient(&copilot.ClientOptions{
        LogLevel: "error",
    })

    // Start the client
    if err := client.Start(context.Background()); err != nil {
        log.Fatal(err)
    }
    defer client.Stop()

    // Create a session (OnPermissionRequest is optional; ApproveAll allows every tool)
    session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
        Model:               "gpt-5",
        OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
    })
    if err != nil {
        log.Fatal(err)
    }
    defer session.Disconnect()

    // Set up event handler
    done := make(chan bool)
    session.On(func(event copilot.SessionEvent) {
        switch d := event.Data.(type) {
        case *copilot.AssistantMessageData:
            fmt.Println(d.Content)
        case *copilot.SessionIdleData:
            close(done)
        }
    })

    // Send a message
    _, err = session.Send(context.Background(), copilot.MessageOptions{
        Prompt: "What is 2+2?",
    })
    if err != nil {
        log.Fatal(err)
    }

    // Wait for completion
    <-done
}

Distributing your application with an embedded GitHub Copilot CLI

The SDK supports bundling, using Go's embed package, the Copilot CLI binary within your application's distribution. This allows you to bundle a specific CLI version and avoid external dependencies on the user's system.

Follow these steps to embed the CLI:

1. Run go get -tool github.com/github/copilot-sdk/go/cmd/bundler. This is a one-time setup step per project.
2. Run go tool bundler in your build environment just before building your application.

That's it! When your application calls copilot.NewClient without a Connection field (or with an empty StdioConnection{}) and no COPILOT_CLI_PATH environment variable, the SDK will automatically install the embedded CLI to a cache directory and use it for all operations.

API Reference

Client

• NewClient(options *ClientOptions) *Client - Create a new client
• Start(ctx context.Context) error - Start the CLI server
• Stop() error - Stop the CLI server
• ForceStop() - Forcefully stop without graceful cleanup
• CreateSession(config *SessionConfig) (*Session, error) - Create a new session
• ResumeSession(sessionID string, config *ResumeSessionConfig) (*Session, error) - Resume an existing session
• ResumeSessionWithOptions(sessionID string, config *ResumeSessionConfig) (*Session, error) - Resume with additional configuration
• ListSessions(filter *SessionListFilter) ([]SessionMetadata, error) - List sessions (with optional filter)
• DeleteSession(sessionID string) error - Delete a session permanently
• GetLastSessionID(ctx context.Context) (*string, error) - Get the ID of the most recently updated session
• Ping(message string) (*PingResponse, error) - Ping the server
• RuntimePort() int - TCP port the runtime is listening on (0 if stdio)
• GetForegroundSessionID(ctx context.Context) (*string, error) - Get the session ID currently displayed in TUI (TUI+server mode only)
• SetForegroundSessionID(ctx context.Context, sessionID string) error - Request TUI to display a specific session (TUI+server mode only)
• On(handler SessionLifecycleHandler) func() - Subscribe to all lifecycle events; returns unsubscribe function
• OnEventType(eventType SessionLifecycleEventType, handler SessionLifecycleHandler) func() - Subscribe to specific lifecycle event type

Session Lifecycle Events:

// Subscribe to all lifecycle events
unsubscribe := client.On(func(event copilot.SessionLifecycleEvent) {
    fmt.Printf("Session %s: %s\n", event.SessionID, event.Type)
})
defer unsubscribe()

// Subscribe to specific event type
unsubscribe := client.OnEventType(copilot.SessionLifecycleForeground, func(event copilot.SessionLifecycleEvent) {
    fmt.Printf("Session %s is now in foreground\n", event.SessionID)
})

Event types: SessionLifecycleCreated, SessionLifecycleDeleted, SessionLifecycleUpdated, SessionLifecycleForeground, SessionLifecycleBackground

ClientOptions:

• Connection (RuntimeConnection): How the SDK connects to the runtime. Construct via one of:

  • StdioConnection{Path, Args} — spawn a runtime over stdio (the default if Connection is nil)
  • TcpConnection{Port, ConnectionToken, Path, Args} — spawn a runtime that listens on TCP
  • UriConnection{URL, ConnectionToken} — connect to an already-running runtime (no process spawned)

  When Path is empty for stdio/tcp, the SDK uses the bundled CLI (or COPILOT_CLI_PATH env var).

• Cwd (string): Working directory for the runtime process

• BaseDirectory (string): Base directory for Copilot data (session state, config, etc.). Sets COPILOT_HOME on the spawned runtime. When empty, the runtime defaults to ~/.copilot. Ignored with UriConnection. This does not affect where the Go SDK extracts the embedded CLI binary; use embeddedcli.Config.Dir for the extraction/cache location.

• LogLevel (string): Log level. When empty (default), the runtime uses its own default level (the SDK does not pass --log-level).

• Env ([]string): Environment variables for the runtime process (default: inherits from current process)

• GitHubToken (string): GitHub token for authentication. When provided, takes priority over other auth methods.

• UseLoggedInUser (*bool): Whether to use logged-in user for authentication (default: true, but false when GitHubToken is provided). Cannot be used with UriConnection.

• EnableRemoteSessions (bool): Enable remote session support (Mission Control integration). Ignored with UriConnection.

• Telemetry (*TelemetryConfig): OpenTelemetry configuration for the runtime. Providing this enables telemetry — no separate flag needed. See Telemetry below.

SessionConfig:

• Model (string): Model to use ("gpt-5", "claude-sonnet-4.5", etc.). Required when using custom provider.
• ReasoningEffort (string): Reasoning effort level for models that support it ("low", "medium", "high", "xhigh"). Use ListModels() to check which models support this option.
• SessionID (string): Custom session ID
• Tools ([]Tool): Custom tools exposed to the CLI
• SystemMessage (*SystemMessageConfig): System message configuration. Supports three modes:
  • append (default): Appends Content after the SDK-managed prompt
  • replace: Replaces the entire prompt with Content
  • customize: Selectively override individual sections via Sections map (keys: SectionIdentity, SectionTone, SectionToolEfficiency, SectionEnvironmentContext, SectionCodeChangeRules, SectionGuidelines, SectionSafety, SectionToolInstructions, SectionCustomInstructions, SectionRuntimeInstructions, SectionLastInstructions; values: SectionOverride with Action and optional Content)
• Provider (*ProviderConfig): Custom API provider configuration (BYOK). See Custom Providers section.
• Streaming (*bool): Enable streaming delta events (nil = runtime default)
• InfiniteSessions (*InfiniteSessionConfig): Automatic context compaction configuration
• OnPermissionRequest (PermissionHandlerFunc): Optional handler called before each tool execution to approve or deny it. When nil, permission requests are emitted as events and left pending for manual resolution. Use copilot.PermissionHandler.ApproveAll to allow everything, or provide a custom function for fine-grained control. See Permission Handling section.
• OnUserInputRequest (UserInputHandler): Handler for user input requests from the agent (enables ask_user tool). See User Input Requests section.
• Hooks (*SessionHooks): Hook handlers for session lifecycle events. See Session Hooks section.
• Commands ([]CommandDefinition): Slash-commands registered for this session. See Commands section.
• OnElicitationRequest (ElicitationHandler): Handler for elicitation requests from the server. See Elicitation Requests section.

ResumeSessionConfig:

• OnPermissionRequest (PermissionHandlerFunc): Optional handler called before each tool execution to approve or deny it. See Permission Handling section.
• Tools ([]Tool): Tools to expose when resuming
• ReasoningEffort (string): Reasoning effort level for models that support it
• Provider (*ProviderConfig): Custom API provider configuration (BYOK). See Custom Providers section.
• Streaming (*bool): Enable streaming delta events (nil = runtime default)
• Commands ([]CommandDefinition): Slash-commands. See Commands section.
• OnElicitationRequest (ElicitationHandler): Elicitation handler. See Elicitation Requests section.

Session

• Send(ctx context.Context, options MessageOptions) (string, error) - Send a message
• On(handler SessionEventHandler) func() - Subscribe to events (returns unsubscribe function)
• Abort(ctx context.Context) error - Abort the currently processing message
• GetEvents(ctx context.Context) ([]SessionEvent, error) - Get event history
• Disconnect() error - Disconnect the session (releases in-memory resources, preserves disk state)
• UI() *SessionUI - Interactive UI API for elicitation dialogs
• Capabilities() SessionCapabilities - Host capabilities (e.g. elicitation support)

Helper Functions

• Bool(v bool) *bool - Helper to create bool pointers (e.g. for Streaming)
• Int(v int) *int - Helper to create int pointers for MinLength, MaxLength
• String(v string) *string - Helper to create string pointers
• Float64(v float64) *float64 - Helper to create float64 pointers

System Message Customization

Control the system prompt using SystemMessage in session config:

session, err := client.CreateSession(ctx, &copilot.SessionConfig{
    SystemMessage: &copilot.SystemMessageConfig{
        Content: "Always check for security vulnerabilities before suggesting changes.",
    },
})

The SDK auto-injects environment context, tool instructions, and security guardrails. The default CLI persona is preserved, and your Content is appended after SDK-managed sections. To change the persona or fully redefine the prompt, use Mode: "replace" or Mode: "customize".

Customize Mode

Use Mode: "customize" to selectively override individual sections of the prompt while preserving the rest:

session, err := client.CreateSession(ctx, &copilot.SessionConfig{
    SystemMessage: &copilot.SystemMessageConfig{
        Mode: "customize",
        Sections: map[string]copilot.SectionOverride{
            // Replace the tone/style section
            copilot.SectionTone: {Action: "replace", Content: "Respond in a warm, professional tone. Be thorough in explanations."},
            // Remove coding-specific rules
            copilot.SectionCodeChangeRules: {Action: "remove"},
            // Append to existing guidelines
            copilot.SectionGuidelines: {Action: "append", Content: "\n* Always cite data sources"},
        },
        // Additional instructions appended after all sections
        Content: "Focus on financial analysis and reporting.",
    },
})

Available section constants: SectionIdentity, SectionTone, SectionToolEfficiency, SectionEnvironmentContext, SectionCodeChangeRules, SectionGuidelines, SectionSafety, SectionToolInstructions, SectionCustomInstructions, SectionRuntimeInstructions, SectionLastInstructions.

Each section override supports four actions:

• replace — Replace the section content entirely
• remove — Remove the section from the prompt
• append — Add content after the existing section
• prepend — Add content before the existing section

Unknown section IDs are handled gracefully: content from replace/append/prepend overrides is appended to additional instructions, and remove overrides are silently ignored.

Image Support

The SDK supports image attachments via the Attachments field in MessageOptions. You can attach images by providing their file path, or by passing base64-encoded data directly using a blob attachment:

// File attachment — runtime reads from disk
_, err = session.Send(context.Background(), copilot.MessageOptions{
    Prompt: "What's in this image?",
    Attachments: []copilot.Attachment{
        &copilot.UserMessageAttachmentFile{
            DisplayName: "image.jpg",
            Path:        "/path/to/image.jpg",
        },
    },
})

// Blob attachment — provide base64 data directly
mimeType := "image/png"
_, err = session.Send(context.Background(), copilot.MessageOptions{
    Prompt: "What's in this image?",
    Attachments: []copilot.Attachment{
        &copilot.UserMessageAttachmentBlob{
            Data:     base64ImageData,
            MIMEType: mimeType,
        },
    },
})

Supported image formats include JPG, PNG, GIF, and other common image types. The agent's view tool can also read images directly from the filesystem, so you can also ask questions like:

_, err = session.Send(context.Background(), copilot.MessageOptions{
    Prompt: "What does the most recent jpg in this directory portray?",
})

Tools

Expose your own functionality to Copilot by attaching tools to a session.

Using DefineTool (Recommended)

Use DefineTool for type-safe tools with automatic JSON schema generation:

type LookupIssueParams struct {
    ID string `json:"id" jsonschema:"Issue identifier"`
}

lookupIssue := copilot.DefineTool("lookup_issue", "Fetch issue details from our tracker",
    func(params LookupIssueParams, inv copilot.ToolInvocation) (any, error) {
        // params is automatically unmarshaled from the LLM's arguments
        issue, err := fetchIssue(params.ID)
        if err != nil {
            return nil, err
        }
        return issue.Summary, nil
    })

session, _ := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    Tools: []copilot.Tool{lookupIssue},
})

Using Tool struct directly

For more control over the JSON schema, use the Tool struct directly:

lookupIssue := copilot.Tool{
    Name:        "lookup_issue",
    Description: "Fetch issue details from our tracker",
    Parameters: map[string]any{
        "type": "object",
        "properties": map[string]any{
            "id": map[string]any{
                "type":        "string",
                "description": "Issue identifier",
            },
        },
        "required": []string{"id"},
    },
    Handler: func(invocation copilot.ToolInvocation) (copilot.ToolResult, error) {
        args := invocation.Arguments.(map[string]any)
        issue, err := fetchIssue(args["id"].(string))
        if err != nil {
            return copilot.ToolResult{}, err
        }
        return copilot.ToolResult{
            TextResultForLLM: issue.Summary,
            ResultType:       "success",
            SessionLog:       fmt.Sprintf("Fetched issue %s", issue.ID),
        }, nil
    },
}

session, _ := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    Tools: []copilot.Tool{lookupIssue},
})

When the model selects a tool, the SDK automatically runs your handler (in parallel with other calls) and responds to the CLI's tool.call with the handler's result.

Overriding Built-in Tools

If you register a tool with the same name as a built-in CLI tool (e.g. edit_file, read_file), the SDK will throw an error unless you explicitly opt in by setting OverridesBuiltInTool = true. This flag signals that you intend to replace the built-in tool with your custom implementation.

editFile := copilot.DefineTool("edit_file", "Custom file editor with project-specific validation",
    func(params EditFileParams, inv copilot.ToolInvocation) (any, error) {
        // your logic
    })
editFile.OverridesBuiltInTool = true

Skipping Permission Prompts

Set SkipPermission = true on a tool to allow it to execute without triggering a permission prompt:

safeLookup := copilot.DefineTool("safe_lookup", "A read-only lookup that needs no confirmation",
    func(params LookupParams, inv copilot.ToolInvocation) (any, error) {
        // your logic
    })
safeLookup.SkipPermission = true

Streaming

Enable streaming to receive assistant response chunks as they're generated:

package main

import (
	"context"
    "fmt"
    "log"

    copilot "github.com/github/copilot-sdk/go"
)

func main() {
    client := copilot.NewClient(nil)

    if err := client.Start(context.Background()); err != nil {
        log.Fatal(err)
    }
    defer client.Stop()

    session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
        Model:     "gpt-5",
        Streaming: copilot.Bool(true),
    })
    if err != nil {
        log.Fatal(err)
    }
    defer session.Disconnect()

    done := make(chan bool)

    session.On(func(event copilot.SessionEvent) {
        switch d := event.Data.(type) {
        case *copilot.AssistantMessageDeltaData:
            // Streaming message chunk - print incrementally
            fmt.Print(d.DeltaContent)
        case *copilot.AssistantReasoningDeltaData:
            // Streaming reasoning chunk (if model supports reasoning)
            fmt.Print(d.DeltaContent)
        case *copilot.AssistantMessageData:
            // Final message - complete content
            fmt.Println("\n--- Final message ---")
            fmt.Println(d.Content)
        case *copilot.AssistantReasoningData:
            // Final reasoning content (if model supports reasoning)
            fmt.Println("--- Reasoning ---")
            fmt.Println(d.Content)
        case *copilot.SessionIdleData:
            close(done)
        }
    })

    _, err = session.Send(context.Background(), copilot.MessageOptions{
        Prompt: "Tell me a short story",
    })
    if err != nil {
        log.Fatal(err)
    }

    <-done
}

When Streaming: copilot.Bool(true):

• assistant.message_delta events are sent with DeltaContent containing incremental text
• assistant.reasoning_delta events are sent with DeltaContent for reasoning/chain-of-thought (model-dependent)
• Accumulate DeltaContent values to build the full response progressively
• The final assistant.message and assistant.reasoning events contain the complete content

Note: assistant.message and assistant.reasoning (final events) are always sent regardless of streaming setting.

Infinite Sessions

By default, sessions use infinite sessions which automatically manage context window limits through background compaction and persist state to a workspace directory.

// Default: infinite sessions enabled with default thresholds
session, _ := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
})

// Access the workspace path for checkpoints and files
fmt.Println(session.WorkspacePath())
// => ~/.copilot/session-state/{sessionId}/

// Custom thresholds
session, _ := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    InfiniteSessions: &copilot.InfiniteSessionConfig{
        Enabled:                       copilot.Bool(true),
        BackgroundCompactionThreshold: copilot.Float64(0.80), // Start compacting at 80% context usage
        BufferExhaustionThreshold:     copilot.Float64(0.95), // Block at 95% until compaction completes
    },
})

// Disable infinite sessions
session, _ := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    InfiniteSessions: &copilot.InfiniteSessionConfig{
        Enabled: copilot.Bool(false),
    },
})

When enabled, sessions emit compaction events:

• session.compaction_start - Background compaction started
• session.compaction_complete - Compaction finished (includes token counts)

Custom Providers

The SDK supports custom OpenAI-compatible API providers (BYOK - Bring Your Own Key), including local providers like Ollama. When using a custom provider, you must specify the Model explicitly.

ProviderConfig:

• Type (string): Provider type - "openai", "azure", or "anthropic" (default: "openai")
• BaseURL (string): API endpoint URL (required)
• APIKey (string): API key (optional for local providers like Ollama)
• BearerToken (string): Bearer token for authentication (takes precedence over APIKey)
• WireApi (string): API format for OpenAI/Azure - "completions" or "responses" (default: "completions")
• Azure.APIVersion (string): Azure API version (default: "2024-10-21")

Example with Ollama:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "deepseek-coder-v2:16b", // Required when using custom provider
    Provider: &copilot.ProviderConfig{
        Type:    "openai",
        BaseURL: "http://localhost:11434/v1", // Ollama endpoint
        // APIKey not required for Ollama
    },
})

Example with custom OpenAI-compatible API:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-4",
    Provider: &copilot.ProviderConfig{
        Type:    "openai",
        BaseURL: "https://my-api.example.com/v1",
        APIKey:  os.Getenv("MY_API_KEY"),
    },
})

Example with Azure OpenAI:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-4",
    Provider: &copilot.ProviderConfig{
        Type:    "azure",  // Must be "azure" for Azure endpoints, NOT "openai"
        BaseURL: "https://my-resource.openai.azure.com",  // Just the host, no path
        APIKey:  os.Getenv("AZURE_OPENAI_KEY"),
        Azure: &copilot.AzureProviderOptions{
            APIVersion: "2024-10-21",
        },
    },
})

Important notes:

• When using a custom provider, the Model parameter is required. The SDK will return an error if no model is specified.
• For Azure OpenAI endpoints (*.openai.azure.com), you must use Type: "azure", not Type: "openai".
• The BaseURL should be just the host (e.g., https://my-resource.openai.azure.com). Do not include /openai/v1 in the URL - the SDK handles path construction automatically.

Telemetry

The SDK supports OpenTelemetry for distributed tracing. Provide a Telemetry config to enable trace export and automatic W3C Trace Context propagation.

client, err := copilot.NewClient(copilot.ClientOptions{
    Telemetry: &copilot.TelemetryConfig{
        OTLPEndpoint: "http://localhost:4318",
    },
})

TelemetryConfig fields:

• OTLPEndpoint (string): OTLP HTTP endpoint URL
• FilePath (string): File path for JSON-lines trace output
• ExporterType (string): "otlp-http" or "file"
• SourceName (string): Instrumentation scope name
• CaptureContent (bool): Whether to capture message content

Trace context (traceparent/tracestate) is automatically propagated between the SDK and CLI on CreateSession, ResumeSession, and Send calls, and inbound when the CLI invokes tool handlers.

Note: The current ToolHandler signature does not accept a context.Context, so the inbound trace context cannot be passed to handler code. Spans created inside a tool handler will not be automatically parented to the CLI's execute_tool span. A future version may add a context parameter.

Dependency: go.opentelemetry.io/otel

Permission Handling

An OnPermissionRequest handler is optional when you create or resume a session. When provided, it is called before the agent executes each tool (file writes, shell commands, custom tools, etc.) and returns a decision. When nil, permission requests are emitted as events and left pending for the consumer to resolve with the pending permission RPC.

Approve All (simplest)

Use the built-in PermissionHandler.ApproveAll helper to allow every tool call without any checks:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model:               "gpt-5",
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
})

Custom Permission Handler

Provide your own PermissionHandlerFunc to inspect each request and apply custom logic:

import (
    "fmt"

    copilot "github.com/github/copilot-sdk/go"
    "github.com/github/copilot-sdk/go/rpc"
)

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    OnPermissionRequest: func(request copilot.PermissionRequest, invocation copilot.PermissionInvocation) (rpc.PermissionDecision, error) {
        // Type-switch on the discriminated PermissionRequest variants to
        // access per-kind fields:
        if shell, ok := request.(*copilot.PermissionRequestShell); ok {
            feedback := fmt.Sprintf("Refusing shell: %s", shell.FullCommandText)
            return &rpc.PermissionDecisionReject{Feedback: &feedback}, nil
        }
        return &rpc.PermissionDecisionApproveOnce{}, nil
    },
})

Permission Decisions

The handler returns an rpc.PermissionDecision — a sealed interface implemented by every decision variant:

Variant	Meaning
&rpc.PermissionDecisionApproveOnce{}	Allow this single request
&rpc.PermissionDecisionReject{...}	Deny the request (set Feedback to forward a message to the LLM)
&rpc.PermissionDecisionUserNotAvailable{}	Deny because no user is available to confirm
&rpc.PermissionDecisionNoResult{}	Decline to respond, allowing another connected client to answer instead

Richer decisions (PermissionDecisionApproveForSession, PermissionDecisionApproveForLocation, PermissionDecisionApprovePermanently) carry per-kind approval payloads — instantiate the variant struct directly.

Resuming Sessions

You may pass OnPermissionRequest when resuming a session too:

session, err := client.ResumeSession(context.Background(), sessionID, &copilot.ResumeSessionConfig{
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
})

Per-Tool Skip Permission

To let a specific custom tool bypass the permission prompt entirely, set SkipPermission = true on the tool. See Skipping Permission Prompts under Tools.

User Input Requests

Enable the agent to ask questions to the user using the ask_user tool by providing an OnUserInputRequest handler:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    OnUserInputRequest: func(request copilot.UserInputRequest, invocation copilot.UserInputInvocation) (copilot.UserInputResponse, error) {
        // request.Question - The question to ask
        // request.Choices - Optional slice of choices for multiple choice
        // request.AllowFreeform - Whether freeform input is allowed (default: true)

        fmt.Printf("Agent asks: %s\n", request.Question)
        if len(request.Choices) > 0 {
            fmt.Printf("Choices: %v\n", request.Choices)
        }

        // Return the user's response
        return copilot.UserInputResponse{
            Answer:      "User's answer here",
            WasFreeform: true, // Whether the answer was freeform (not from choices)
        }, nil
    },
})

Session Hooks

Hook into session lifecycle events by providing handlers in the Hooks configuration:

session, err := client.CreateSession(context.Background(), &copilot.SessionConfig{
    Model: "gpt-5",
    Hooks: &copilot.SessionHooks{
        // Called before each tool execution
        OnPreToolUse: func(input copilot.PreToolUseHookInput, invocation copilot.HookInvocation) (*copilot.PreToolUseHookOutput, error) {
            fmt.Printf("About to run tool: %s\n", input.ToolName)
            // Return permission decision and optionally modify args
            return &copilot.PreToolUseHookOutput{
                PermissionDecision: "allow", // "allow", "deny", or "ask"
                ModifiedArgs:       input.ToolArgs, // Optionally modify tool arguments
                AdditionalContext:  "Extra context for the model",
            }, nil
        },

        // Called after each tool execution
        OnPostToolUse: func(input copilot.PostToolUseHookInput, invocation copilot.HookInvocation) (*copilot.PostToolUseHookOutput, error) {
            fmt.Printf("Tool %s completed\n", input.ToolName)
            return &copilot.PostToolUseHookOutput{
                AdditionalContext: "Post-execution notes",
            }, nil
        },

        // Called when user submits a prompt
        OnUserPromptSubmitted: func(input copilot.UserPromptSubmittedHookInput, invocation copilot.HookInvocation) (*copilot.UserPromptSubmittedHookOutput, error) {
            fmt.Printf("User prompt: %s\n", input.Prompt)
            return &copilot.UserPromptSubmittedHookOutput{
                ModifiedPrompt: input.Prompt, // Optionally modify the prompt
            }, nil
        },

        // Called when session starts
        OnSessionStart: func(input copilot.SessionStartHookInput, invocation copilot.HookInvocation) (*copilot.SessionStartHookOutput, error) {
            fmt.Printf("Session started from: %s\n", input.Source) // "startup", "resume", "new"
            return &copilot.SessionStartHookOutput{
                AdditionalContext: "Session initialization context",
            }, nil
        },

        // Called when session ends
        OnSessionEnd: func(input copilot.SessionEndHookInput, invocation copilot.HookInvocation) (*copilot.SessionEndHookOutput, error) {
            fmt.Printf("Session ended: %s\n", input.Reason)
            return nil, nil
        },

        // Called when an error occurs
        OnErrorOccurred: func(input copilot.ErrorOccurredHookInput, invocation copilot.HookInvocation) (*copilot.ErrorOccurredHookOutput, error) {
            fmt.Printf("Error in %s: %s\n", input.ErrorContext, input.Error)
            return &copilot.ErrorOccurredHookOutput{
                ErrorHandling: "retry", // "retry", "skip", or "abort"
            }, nil
        },
    },
})

Available hooks:

• OnPreToolUse - Intercept tool calls before execution. Can allow/deny or modify arguments.
• OnPostToolUse - Process tool results after execution. Can modify results or add context.
• OnUserPromptSubmitted - Intercept user prompts. Can modify the prompt before processing.
• OnSessionStart - Run logic when a session starts or resumes.
• OnSessionEnd - Cleanup or logging when session ends.
• OnErrorOccurred - Handle errors with retry/skip/abort strategies.

Commands

Register slash-commands that users can invoke from the CLI TUI. When a user types /deploy production, the SDK dispatches to your handler and responds via the RPC layer.

session, err := client.CreateSession(ctx, &copilot.SessionConfig{
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
    Commands: []copilot.CommandDefinition{
        {
            Name:        "deploy",
            Description: "Deploy the app to production",
            Handler: func(ctx copilot.CommandContext) error {
                fmt.Printf("Deploying with args: %s\n", ctx.Args)
                // ctx.SessionID, ctx.Command, ctx.CommandName, ctx.Args
                return nil
            },
        },
        {
            Name:        "rollback",
            Description: "Rollback the last deployment",
            Handler: func(ctx copilot.CommandContext) error {
                return nil
            },
        },
    },
})

Commands are also available when resuming sessions:

session, err := client.ResumeSession(ctx, sessionID, &copilot.ResumeSessionConfig{
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
    Commands: []copilot.CommandDefinition{
        {Name: "status", Description: "Show status", Handler: statusHandler},
    },
})

If a handler returns an error, the SDK sends the error message back to the server. Unknown commands automatically receive an error response.

UI Elicitation

The SDK provides convenience methods to ask the user questions via elicitation dialogs. These are gated by host capabilities — check session.Capabilities().UI.Elicitation before calling.

ui := session.UI()

// Confirmation dialog — returns bool
confirmed, err := ui.Confirm(ctx, "Deploy to production?")

// Selection dialog — returns (selected string, ok bool, error)
choice, ok, err := ui.Select(ctx, "Pick an environment", []string{"staging", "production"})

// Text input — returns (text, ok bool, error)
name, ok, err := ui.Input(ctx, "Enter the release name", &copilot.UiInputOptions{
    Title:       "Release Name",
    Description: "A short name for the release",
    MinLength:   copilot.Int(1),
    MaxLength:   copilot.Int(50),
})

// Full custom elicitation with a schema
result, err := ui.Elicitation(ctx, "Configure deployment", rpc.RequestedSchema{
    Type: rpc.RequestedSchemaTypeObject,
    Properties: map[string]rpc.Property{
        "target": {Type: rpc.PropertyTypeString, Enum: []string{"staging", "production"}},
        "force":  {Type: rpc.PropertyTypeBoolean},
    },
    Required: []string{"target"},
})
// result.Action is "accept", "decline", or "cancel"
// result.Content has the form values when Action is "accept"

Elicitation Requests (Server→Client)

When the server (or an MCP tool) needs to ask the end-user a question, it sends an elicitation.requested event. Register a handler to respond:

session, err := client.CreateSession(ctx, &copilot.SessionConfig{
    OnPermissionRequest: copilot.PermissionHandler.ApproveAll,
    OnElicitationRequest: func(ctx copilot.ElicitationContext) (copilot.ElicitationResult, error) {
        // ctx.SessionID — session that triggered the request
        // ctx.Message — what's being asked
        // ctx.RequestedSchema — form schema (if mode is "form")
        // ctx.Mode — "form" or "url"
        // ctx.ElicitationSource — e.g. MCP server name
        // ctx.URL — browser URL (if mode is "url")

        // Return the user's response
        return copilot.ElicitationResult{
            Action:  "accept",
            Content: map[string]any{"confirmed": true},
        }, nil
    },
})

When OnElicitationRequest is provided, the SDK automatically:

• Sends requestElicitation: true in the create/resume payload
• Routes elicitation.requested events to your handler
• Auto-cancels the request if your handler returns an error (so the server doesn't hang)

Transport Modes

stdio (Default)

Communicates with CLI via stdin/stdout pipes. Recommended for most use cases.

client := copilot.NewClient(nil) // Uses stdio by default

TCP

Communicates with CLI via TCP socket. Useful for distributed scenarios.

Environment Variables

• COPILOT_CLI_PATH - Path to the Copilot CLI executable

License

MIT