diff --git a/internal/ai/llm/errors.go b/internal/ai/llm/errors.go
index 50183e6..07fddef 100644
--- a/internal/ai/llm/errors.go
+++ b/internal/ai/llm/errors.go
@@ -32,22 +32,30 @@ type RateLimitedError struct {
 	// RetryAfter is how long the vendor asked callers to wait; 0 means it
 	// did not say.
 	RetryAfter time.Duration
-	secret     string
+	// text is the redacted Error text set by NewRateLimitedError; "" means
+	// the error was built without a credential.
+	text 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.
+// the credential sent with the request, or "" when the request sent none.
+// Every occurrence of a non-empty secret is removed from the error text
+// when it is built, even where the fixed text happens to spell it, and the
+// secret itself is not kept.
 func NewRateLimitedError(retryAfter time.Duration, secret string) *RateLimitedError {
-	return &RateLimitedError{RetryAfter: retryAfter, secret: secret}
+	e := &RateLimitedError{RetryAfter: retryAfter}
+	e.text = Redact(e.Error(), secret)
+	return e
 }
 
 func (e *RateLimitedError) Error() string {
-	if e.RetryAfter == 0 {
-		return Redact(ErrRateLimited.Error(), e.secret)
+	if e.text != "" {
+		return e.text
 	}
-	return Redact(fmt.Sprintf("%s: retry after %v", ErrRateLimited, e.RetryAfter), e.secret)
+	if e.RetryAfter == 0 {
+		return ErrRateLimited.Error()
+	}
+	return fmt.Sprintf("%s: retry after %v", ErrRateLimited, e.RetryAfter)
 }
 
 // Is reports whether target is ErrRateLimited.
@@ -84,7 +92,7 @@ func Redact(s, secret string) string {
 type ProviderError struct {
 	status int
 	body   string
-	secret string
+	text   string
 }
 
 // NewProviderError returns the error for an unexpected HTTP status. It
@@ -92,8 +100,9 @@ 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. Error removes it from the complete
-// text too, even where the fixed text happens to spell it.
+// truncation mark cannot complete it. It is removed from the complete error
+// text too, even where the fixed text happens to spell it, and the secret
+// itself is not kept.
 func NewProviderError(status int, body []byte, secret string) *ProviderError {
 	s := strings.TrimSpace(Redact(string(body), secret))
 	if len(s) > MaxBodyExcerpt {
@@ -103,7 +112,11 @@ func NewProviderError(status int, body []byte, secret string) *ProviderError {
 		}
 		s = Redact(s[:cut]+"…", secret)
 	}
-	return &ProviderError{status: status, body: s, secret: secret}
+	text := fmt.Sprintf("%s: HTTP %d", ErrProvider, status)
+	if s != "" {
+		text += ": " + s
+	}
+	return &ProviderError{status: status, body: s, text: Redact(text, secret)}
 }
 
 // Status returns the HTTP status code.
@@ -113,12 +126,7 @@ func (e *ProviderError) Status() int { return e.status }
 // when the vendor sent no body.
 func (e *ProviderError) Body() string { return e.body }
 
-func (e *ProviderError) Error() string {
-	if e.body == "" {
-		return Redact(fmt.Sprintf("%s: HTTP %d", ErrProvider, e.status), e.secret)
-	}
-	return Redact(fmt.Sprintf("%s: HTTP %d: %s", ErrProvider, e.status, e.body), e.secret)
-}
+func (e *ProviderError) Error() string { return e.text }
 
 // Is reports whether target is ErrProvider.
 func (e *ProviderError) Is(target error) bool { return target == ErrProvider }
diff --git a/internal/ai/llm/errors_test.go b/internal/ai/llm/errors_test.go
index b5784ad..5ac5fa7 100644
--- a/internal/ai/llm/errors_test.go
+++ b/internal/ai/llm/errors_test.go
@@ -184,3 +184,15 @@ func TestRateLimitedErrorWithFixedWordSecretNeverLeaksSecret(t *testing.T) {
 		}
 	}
 }
+
+func TestTypedErrorsDoNotKeepSecret(t *testing.T) {
+	const secret = "sk-live-0123456789abcdef"
+	for _, err := range []error{
+		NewProviderError(500, []byte("down "+secret), secret),
+		NewRateLimitedError(30*time.Second, secret),
+	} {
+		if got := fmt.Sprintf("%#v %+v", err, err); strings.Contains(got, secret) {
+			t.Fatalf("formatting %T leaks the secret: %q", err, got)
+		}
+	}
+}