Error handling hook

The onErrorOccurred hook is called when errors occur during session execution. Use it to:

• Implement custom error logging
• Track error patterns
• Provide user-friendly error messages
• Trigger alerts for critical errors

Hook signature

import type { ErrorOccurredHookInput, HookInvocation, ErrorOccurredHookOutput } from "@github/copilot-sdk";
type ErrorOccurredHandler = (
  input: ErrorOccurredHookInput,
  invocation: HookInvocation
) => Promise<
  ErrorOccurredHookOutput | null | undefined
>;

For hook signatures in Python, Go, and .NET, see the github/copilot-sdk repository.

Input

Field	Type	Description
timestamp	number	Unix timestamp when the error occurred
cwd	string	Current working directory
error	string	Error message
errorContext	string	Where the error occurred: "model_call", "tool_execution", "system", or "user_input"
recoverable	boolean	Whether the error can potentially be recovered from

Output

Return null or undefined to use default error handling. Otherwise, return an object with any of the following fields.

Field	Type	Description
suppressOutput	boolean	If true, don't show error output to user
errorHandling	string	How to handle: "retry", "skip", or "abort"
retryCount	number	Number of times to retry (if errorHandling is "retry")
userNotification	string	Custom message to show the user

Examples

Basic error logging

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (
      input, invocation
    ) => {
      console.error(
        `[${invocation.sessionId}] `
        + `Error: ${input.error}`
      );
      console.error(
        `  Context: ${input.errorContext}`
      );
      console.error(
        `  Recoverable: ${input.recoverable}`
      );
      return null;
    },
  },
});

For examples in Python, Go, and .NET, see the github/copilot-sdk repository.

Send errors to monitoring service

import { captureException } from "@sentry/node"; // or your monitoring service

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (input, invocation) => {
      captureException(new Error(input.error), {
        tags: {
          sessionId: invocation.sessionId,
          errorContext: input.errorContext,
        },
        extra: {
          error: input.error,
          recoverable: input.recoverable,
          cwd: input.cwd,
        },
      });
      
      return null;
    },
  },
});

User-friendly error messages

const ERROR_MESSAGES: Record<string, string> = {
  "model_call":
    "There was an issue communicating "
    + "with the AI model. Please try again.",
  "tool_execution":
    "A tool failed to execute. "
    + "Please check your inputs and try again.",
  "system":
    "A system error occurred. "
    + "Please try again later.",
  "user_input":
    "There was an issue with your input. "
    + "Please check and try again.",
};

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (input) => {
      const friendlyMessage =
        ERROR_MESSAGES[input.errorContext];

      if (friendlyMessage) {
        return {
          userNotification: friendlyMessage,
        };
      }

      return null;
    },
  },
});

Suppress non-critical errors

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (input) => {
      // Suppress tool execution errors
      // that are recoverable
      if (
        input.errorContext === "tool_execution"
        && input.recoverable
      ) {
        console.log(
          `Suppressed recoverable error: `
          + `${input.error}`
        );
        return { suppressOutput: true };
      }
      return null;
    },
  },
});

Add recovery context

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (input) => {
      if (
        input.errorContext === "tool_execution"
      ) {
        return {
          userNotification:
            "The tool failed. Here are some "
            + "recovery suggestions:\n"
            + "- Check if required dependencies "
            + "are installed\n"
            + "- Verify file paths are correct\n"
            + "- Try a simpler approach",
        };
      }

      if (
        input.errorContext === "model_call"
        && input.error.includes("rate")
      ) {
        return {
          errorHandling: "retry",
          retryCount: 3,
          userNotification:
            "Rate limit hit. Retrying...",
        };
      }

      return null;
    },
  },
});

Track error patterns

interface ErrorStats {
  count: number;
  lastOccurred: number;
  contexts: string[];
}

const errorStats =
  new Map<string, ErrorStats>();

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (
      input, invocation
    ) => {
      const key =
        `${input.errorContext}:`
        + `${input.error.substring(0, 50)}`;

      const existing =
        errorStats.get(key) || {
          count: 0,
          lastOccurred: 0,
          contexts: [],
        };

      existing.count++;
      existing.lastOccurred = input.timestamp;
      existing.contexts.push(
        invocation.sessionId
      );

      errorStats.set(key, existing);

      // Alert if error is recurring
      if (existing.count >= 5) {
        console.warn(
          `Recurring error detected: `
          + `${key} (${existing.count} times)`
        );
      }

      return null;
    },
  },
});

Alert on critical errors

const CRITICAL_CONTEXTS = [
  "system", "model_call",
];

const session = await client.createSession({
  hooks: {
    onErrorOccurred: async (
      input, invocation
    ) => {
      if (
        CRITICAL_CONTEXTS.includes(
          input.errorContext
        )
        && !input.recoverable
      ) {
        await sendAlert({
          level: "critical",
          message:
            `Critical error in session `
            + `${invocation.sessionId}`,
          error: input.error,
          context: input.errorContext,
          timestamp: new Date(
            input.timestamp
          ).toISOString(),
        });
      }

      return null;
    },
  },
});

Best practices

• Always log errors. Even if you suppress them from users, keep logs for debugging.
• Categorize errors. Use errorContext to handle different errors appropriately.
• Don't swallow critical errors. Only suppress errors you're certain are non-critical.
• Keep hooks fast. Error handling shouldn't slow down recovery.
• Monitor error patterns. Track recurring errors to identify systemic issues.

Further reading

• Quickstart for hooks
• Session lifecycle hooks
• Pre-tool use hook