bedrock.WithLoadDefaultConfig panics on ordinary AWS config failures (unknown profile, no SSO cache), so a CLI answers a login prompt with a stack trace

[cru-Luis-Rodriguez]

Summary

bedrock.WithLoadDefaultConfig panics when config.LoadDefaultConfig returns an error:

func WithLoadDefaultConfig(ctx context.Context, optFns ...func(*config.LoadOptions) error) option.RequestOption {
	cfg, err := config.LoadDefaultConfig(ctx, optFns...)
	if err != nil {
		panic(err)
	}
	return WithConfig(cfg)
}

bedrock/bedrock.go:186-192 (v1.55.1)

Every failure this converts into a panic is an ordinary, recoverable, user-caused condition rather than a programmer error: a profile name that does not exist, a missing or malformed ~/.aws/config, an SSO cache that was never populated. For a CLI those are the common case on first run, so the tool answers "you have not logged in yet" with a stack trace, and the user cannot tell a misconfiguration from a crash.

Versions

• github.com/anthropics/anthropic-sdk-go v1.55.1
• github.com/aws/aws-sdk-go-v2/config v1.32.34
• go1.25.6, darwin/arm64 (not platform-specific)

Reproduction

No AWS setup required beyond a profile name that does not exist:

package main

import (
	"context"
	"fmt"

	"github.com/anthropics/anthropic-sdk-go"
	"github.com/anthropics/anthropic-sdk-go/bedrock"
)

func main() {
	defer func() {
		if r := recover(); r != nil {
			fmt.Printf("PANICKED: %v\n", r)
		}
	}()
	_ = anthropic.NewClient(bedrock.WithLoadDefaultConfig(context.Background()))
	fmt.Println("no panic")
}

$ AWS_PROFILE=definitely-not-a-real-profile AWS_REGION=us-east-1 go run .
PANICKED: failed to get shared config profile, definitely-not-a-real-profile

Without the recover, that is a stack trace and a non-zero exit.

Expected

The failure is surfaced as an error the caller can present, not a panic.

Why it is awkward to fix, and two options

option.RequestOption has no error channel, which is presumably why the panic is there. Two ways out, either of which would work for us:

1. An erroring variant, leaving the current function untouched for callers who genuinely want to fail fast:

   func WithLoadDefaultConfigErr(ctx context.Context, optFns ...func(*config.LoadOptions) error) (option.RequestOption, error)

2. Defer the failure to the first request: capture the error in the returned option and have the middleware return it, so a caller that never issues a request never sees it and one that does gets a normal error.

Workaround

Call config.LoadDefaultConfig directly, keep the error, and pass the config to bedrock.WithConfig — deferring the failure to the first request with a message naming the likely fix. That is what we do in alibaba/open-code-review, and it is the only reason an expired SSO session there produces a sentence instead of a stack trace.

Note for anyone landing here from the same direction: bedrock.WithConfig needs its own care on SSO profiles — see #414 and #415.