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

Quick Start

package main

import (
    "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(); err != nil {
        log.Fatal(err)
    }
    defer client.Stop()

    // Create a session
    session, err := client.CreateSession(&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(copilot.MessageOptions{
        Prompt: "What is 2+2?",
    })
    if err != nil {
        log.Fatal(err)
    }

    // Wait for completion
    <-done
}

API Reference

Client

• NewClient(options *ClientOptions) *Client - Create a new client
• Start() error - Start the CLI server
• Stop() []error - Stop the CLI server (returns array of errors, empty if all succeeded)
• ForceStop() - Forcefully stop without graceful cleanup
• CreateSession(config *SessionConfig) (*Session, error) - Create a new session
• ResumeSession(sessionID string) (*Session, error) - Resume an existing session
• ResumeSessionWithOptions(sessionID string, config *ResumeSessionConfig) (*Session, error) - Resume with additional configuration
• GetState() ConnectionState - Get connection state
• Ping(message string) (*PingResponse, error) - Ping the server

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)

ResumeSessionConfig:

• Tools ([]Tool): Tools to expose when resuming
• Provider (*ProviderConfig): Custom model provider configuration

Session

• Send(options MessageOptions) (string, error) - Send a message
• On(handler SessionEventHandler) func() - Subscribe to events (returns unsubscribe function)
• Abort() error - Abort the currently processing message
• GetMessages() ([]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

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(&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]interface{}{
        "type": "object",
        "properties": map[string]interface{}{
            "id": map[string]interface{}{
                "type":        "string",
                "description": "Issue identifier",
            },
        },
        "required": []string{"id"},
    },
    Handler: func(invocation copilot.ToolInvocation) (copilot.ToolResult, error) {
        args := invocation.Arguments.(map[string]interface{})
        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(&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.

Streaming

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

package main

import (
    "fmt"
    "log"

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

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

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

    session, err := client.CreateSession(&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(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.

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