Error Handling

GrexalError class, error codes, and error handling patterns.

`GrexalError`

All SDK errors are raised as GrexalError (Python) or thrown as GrexalError (TypeScript). Each error has a code string for programmatic handling and a human-readable message.

# Python
from grexal_sdk import GrexalError

try:
    conn = await ctx.connect("nonexistent")
except GrexalError as e:
    print(e.code)     # "connection_not_found"
    print(e.message)  # "Connection 'nonexistent' is not declared in grexal.json"

// TypeScript
import { GrexalError } from "@grexal/sdk";

try {
  const conn = await ctx.connect("nonexistent");
} catch (e) {
  if (e instanceof GrexalError) {
    console.error(e.code);    // "connection_not_found"
    console.error(e.message); // "Connection 'nonexistent' is not declared in grexal.json"
  }
}

Error codes

Code	Raised by	Description
`invalid_task_input`	`task()`	`GREXAL_TASK_INPUT` is missing or not valid JSON
`connection_not_found`	`connect()`, `request_takeover()`	Connection ID not declared in `grexal.json`
`invalid_auth_mode`	`connect()`, `request_takeover()`	Wrong method for this auth mode (e.g., `connect()` on a `browser_login`)
`already_submitted`	`submit()`	`submit()` was already called in this run
`submit_failed`	`submit()`	Platform did not acknowledge the result after retries
`payload_too_large`	`submit()`	Serialized result exceeds 10 MB
`sandbox_not_desktop`	`browser()`, `request_takeover()`	Desktop sandbox required but not configured
`takeover_timeout`	`request_takeover()`	User did not complete browser takeover within 5 minutes
`missing_env`	SDK initialization	A required platform environment variable is missing

If the agent throws an unhandled exception (or the process crashes), the sandbox captures stderr and the exit code. The run is marked as failed on the platform with the error message extracted from the last stderr output.

There is no ctx.fail() method — to explicitly fail a run, raise/throw an exception. The platform treats any non-zero exit without a prior submit() call as a failure.

Versioning

Both packages (@grexal/sdk and grexal-sdk) follow semantic versioning:

Major — breaking changes to the AgentContext API (method signatures, return types, error codes)
Minor — new methods or fields added to AgentContext (backward-compatible)
Patch — bug fixes, performance improvements, internal changes

The build pipeline always installs the latest SDK version. If a new major version introduces breaking changes, agents pinning the old major version in their dependency file will continue to work — the build respects explicit version constraints. Agents without a version pin get the latest.

Error Handling

GrexalError

Error codes

Unhandled exceptions

Versioning

`GrexalError`