Error Handling

AI operations can fail in predictable ways. ThinkLang provides typed error handling with try/catch so you can respond to specific failure modes.

Syntax

try {
  // statements
} catch ErrorType (binding) {
  // handle error
}

Example

type Summary {
  headline: string
  points: string[]
}

let text = "Brief update: all systems operational."

try {
  let result = think<Summary>("Summarize this text in detail")
    with context: text
  print result
} catch SchemaViolation (e) {
  print "Schema error occurred"
} catch ConfidenceTooLow (e) {
  print "Confidence too low for reliable result"
}

Error Types

ThinkLang defines these error types, all extending a base ThinkError:

Error Type	When it occurs
SchemaViolation	AI output does not match the expected type/schema
ConfidenceTooLow	Confidence is below the threshold passed to expect()
GuardFailed	A guard constraint was not satisfied
TokenBudgetExceeded	The request would exceed the token budget
ModelUnavailable	The configured model cannot be reached
Timeout	The AI call timed out

Multiple Catch Clauses

You can catch different error types in separate clauses:

try {
  let result = think<Analysis>("Analyze this data")
    with context: data
    guard { length: 100..1000 }
  print result
} catch SchemaViolation (e) {
  print "The AI returned malformed data"
} catch GuardFailed (e) {
  print "Output did not meet constraints"
} catch Timeout (e) {
  print "The request timed out"
}

Unmatched error types propagate up the call stack.

Combining with Guards

Guards and try/catch complement each other. Use guards with on_fail: retry(N) for automatic recovery, and try/catch for handling failures that retries cannot fix:

try {
  let result = think<Summary>("Summarize")
    with context: text
    guard { length: 50..500 }
    on_fail: retry(3)
  print result
} catch GuardFailed (e) {
  print "All retries failed — guard still not satisfied"
}

Combining with Confidence

Handle ConfidenceTooLow when using expect():

try {
  let value = result.expect(0.9)
  print value
} catch ConfidenceTooLow (e) {
  print "Falling back to manual review"
}