Strip the API key from fixed error text and keep typed matches

ProviderError and the new NewRateLimitedError constructor now keep the
credential and remove it from their complete Error() text, including
fixed words such as "HTTP" and "rate", so errors.As to them succeeds
through the adapter's redaction stand-in instead of being refused. The
openai adapter builds RateLimitedError with the key. Tests cover the keys
"HTTP" (500), "rate" (429) and "openai" (401 and no model), checking
Error(), Body(), every unwrap layer, errors.Is and errors.As.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/ai/llm/errors.go

@@ -26,17 +26,28 @@ var (
 )
 
 // RateLimitedError is a throttled request. It matches ErrRateLimited.
+// Adapters build it with NewRateLimitedError so its text never holds their
+// credential.
 type RateLimitedError struct {
 	// RetryAfter is how long the vendor asked callers to wait; 0 means it
 	// did not say.
 	RetryAfter time.Duration
+	secret     string
+}
+
+// NewRateLimitedError returns the error for a throttled request. secret is
+// the credential sent with the request, or "" when the request sent none;
+// Error removes every occurrence of a non-empty secret, even where the
+// fixed text happens to spell it.
+func NewRateLimitedError(retryAfter time.Duration, secret string) *RateLimitedError {
+	return &RateLimitedError{RetryAfter: retryAfter, secret: secret}
 }
 
 func (e *RateLimitedError) Error() string {
 	if e.RetryAfter == 0 {
-		return ErrRateLimited.Error()
+		return Redact(ErrRateLimited.Error(), e.secret)
 	}
-	return fmt.Sprintf("%s: retry after %v", ErrRateLimited, e.RetryAfter)
+	return Redact(fmt.Sprintf("%s: retry after %v", ErrRateLimited, e.RetryAfter), e.secret)
 }
 
 // Is reports whether target is ErrRateLimited.
@@ -73,6 +84,7 @@ func Redact(s, secret string) string {
 type ProviderError struct {
 	status int
 	body   string
+	secret string
 }
 
 // NewProviderError returns the error for an unexpected HTTP status. It
@@ -80,7 +92,8 @@ type ProviderError struct {
 // credential sent with the request, or "" when the request sent none; every
 // occurrence of a non-empty secret in body is removed by Redact before the
 // body is cut, so no part of it survives, and again after the cut, so the
-// truncation mark cannot complete it.
+// truncation mark cannot complete it. Error removes it from the complete
+// text too, even where the fixed text happens to spell it.
 func NewProviderError(status int, body []byte, secret string) *ProviderError {
 	s := strings.TrimSpace(Redact(string(body), secret))
 	if len(s) > MaxBodyExcerpt {
@@ -90,7 +103,7 @@ func NewProviderError(status int, body []byte, secret string) *ProviderError {
 		}
 		s = Redact(s[:cut]+"…", secret)
 	}
-	return &ProviderError{status: status, body: s}
+	return &ProviderError{status: status, body: s, secret: secret}
 }
 
 // Status returns the HTTP status code.
@@ -102,9 +115,9 @@ func (e *ProviderError) Body() string { return e.body }
 
 func (e *ProviderError) Error() string {
 	if e.body == "" {
-		return fmt.Sprintf("%s: HTTP %d", ErrProvider, e.status)
+		return Redact(fmt.Sprintf("%s: HTTP %d", ErrProvider, e.status), e.secret)
 	}
-	return fmt.Sprintf("%s: HTTP %d: %s", ErrProvider, e.status, e.body)
+	return Redact(fmt.Sprintf("%s: HTTP %d: %s", ErrProvider, e.status, e.body), e.secret)
 }
 
 // Is reports whether target is ErrProvider.