Copilot CLI SDK for Go

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

Note: This SDK is in technical 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

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

    // Set up event handler
    done := make(chan bool)
    session.On(func(event copilot.SessionEvent) {
        if event.Type == "assistant.message" {
            if event.Data.Content != nil {
                fmt.Println(*event.Data.Content)
            }
        }
        if event.Type == "session.idle" {
            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:

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

That's it! When your application calls copilot.NewClient without a CLIPath nor the 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
GetState() ConnectionState - Get connection state
Ping(message string) (*PingResponse, error) - Ping the server
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:

CLIPath (string): Path to CLI executable (default: "copilot" or COPILOT_CLI_PATH env var)
CLIUrl (string): URL of existing CLI server (e.g., "localhost:8080", "http://127.0.0.1:9000", or just "8080"). When provided, the client will not spawn a CLI process.
Cwd (string): Working directory for CLI process
Port (int): Server port for TCP mode (default: 0 for random)
UseStdio (bool): Use stdio transport instead of TCP (default: true)
LogLevel (string): Log level (default: "info")
AutoStart (*bool): Auto-start server on first use (default: true). Use Bool(false) to disable.
AutoRestart (*bool): Auto-restart on crash (default: true). Use Bool(false) to disable.
Env ([]string): Environment variables for CLI 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 CLIUrl.

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
Provider (*ProviderConfig): Custom API provider configuration (BYOK). See Custom Providers section.
Streaming (bool): Enable streaming delta events
InfiniteSessions (*InfiniteSessionConfig): Automatic context compaction configuration
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.

ResumeSessionConfig:

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

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
GetMessages(ctx context.Context) ([]SessionEvent, error) - Get message history
Destroy() error - Destroy the session

Helper Functions

Bool(v bool) *bool - Helper to create bool pointers for AutoStart/AutoRestart options

Image Support

The SDK supports image attachments via the Attachments field in MessageOptions. You can attach images by providing their file path:

_, err = session.Send(context.Background(), copilot.MessageOptions{
    Prompt: "What's in this image?",
    Attachments: []copilot.Attachment{
        {
            Type: "file",
            Path: "/path/to/image.jpg",
        },
    },
})

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

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: true,
    })
    if err != nil {
        log.Fatal(err)
    }
    defer session.Destroy()

    done := make(chan bool)

    session.On(func(event copilot.SessionEvent) {
        if event.Type == "assistant.message_delta" {
            // Streaming message chunk - print incrementally
            if event.Data.DeltaContent != nil {
                fmt.Print(*event.Data.DeltaContent)
            }
        } else if event.Type == "assistant.reasoning_delta" {
            // Streaming reasoning chunk (if model supports reasoning)
            if event.Data.DeltaContent != nil {
                fmt.Print(*event.Data.DeltaContent)
            }
        } else if event.Type == "assistant.message" {
            // Final message - complete content
            fmt.Println("\n--- Final message ---")
            if event.Data.Content != nil {
                fmt.Println(*event.Data.Content)
            }
        } else if event.Type == "assistant.reasoning" {
            // Final reasoning content (if model supports reasoning)
            fmt.Println("--- Reasoning ---")
            if event.Data.Content != nil {
                fmt.Println(*event.Data.Content)
            }
        }
        if event.Type == "session.idle" {
            close(done)
        }
    })

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

    <-done
}

When Streaming: 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.

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.

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

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Copilot CLI SDK for Go

Installation

Run the Sample

Quick Start

Distributing your application with an embedded GitHub Copilot CLI

API Reference

Client

Session

Helper Functions

Image Support

Tools

Using DefineTool (Recommended)

Using Tool struct directly

Overriding Built-in Tools

Streaming

Infinite Sessions

Custom Providers

User Input Requests

Session Hooks

Transport Modes

stdio (Default)

TCP

Environment Variables

License

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README.md

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History

README.md

File metadata and controls

Copilot CLI SDK for Go

Installation

Run the Sample

Quick Start

Distributing your application with an embedded GitHub Copilot CLI

API Reference

Client

Session

Helper Functions

Image Support

Tools

Using DefineTool (Recommended)

Using Tool struct directly

Overriding Built-in Tools

Streaming

Infinite Sessions

Custom Providers

User Input Requests

Session Hooks

Transport Modes

stdio (Default)

TCP

Environment Variables

License