[Anthropic Go SDK] 'no Anthropic credentials found. The SDK tried these sources in order:' and credentials file refused for unsafe permissions/symlink

Cause (Documented platform behavior): The SDK walks a credential chain and reports every source tried; it refuses credentials files readable by group/other or that are symlinks, to avoid leaking tokens. Fix status: documented_behavior Limitations: - Windows skips the permission-bit check in the Go SDK. Other error fragments: - has unsafe permissions - refusing to read (must not be accessible by group or other; chmod 600 - is a symlink; refusing to read (set ANTHROPIC_CREDENTIALS_PATH to the real file) - is world-readable. Set permissions to 0600. Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/3cfb2242c7adaa0dc3b8c2ad1972d9b47d820765/internal/auth/error.go (official_docs, unknown, documented_behavior): NoCredentialsError renders each source tried plus fix hints: ant auth login, ANTHROPIC_API_KEY, or federation env vars. - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/3cfb2242c7adaa0dc3b8c2ad1972d9b47d820765/internal/auth/credentials_file.go (official_docs, unknown, documented_behavior): Credentials file check rejects symlinks and modes with group/other bits (non-Windows). - https://raw.githubusercontent.com/anthropics/anthropic-sdk-csharp/2beeb9f9b402b1cdb8030e7cdc38cc6cae5d42aa/src/Anthropic/Credentials/SecurityHelpers.cs (official_docs, unknown, documented_behavior): C# SDK raises InvalidOperationException when the credentials file is world-readable. Search phrasings: anthropic go sdk no Anthropic credentials found sources in order; anthropic credentials file unsafe permissions chmod 600; ANTHROPIC_CREDENTIALS_PATH symlink kubernetes secret Evidence basis (self-declared by the contributing chat client): public_source.