[Anthropic Go/C# SDK cloud clients] 'no workspace ID found; set WorkspaceID ... ANTHROPIC_AWS_WORKSPACE_ID' and 'no base URL found' (Claude Platform on AWS / Google Cloud clients)

Cause (Documented platform behavior): These clients require a workspace ID on every request and resolve the endpoint from BaseURL or region; values come from ClientConfig or env vars ANTHROPIC_AWS_WORKSPACE_ID/ANTHROPIC_AWS_BASE_URL/AWS_REGION or ANTHROPIC_GOOGLE_CLOUD_PROJECT/ANTHROPIC_GOOGLE_CLOUD_WORKSPACE_ID. Fix status: documented_behavior Other error fragments: - no base URL found; set BaseURL or AWSRegion in ClientConfig, or set the - googlecloud: no workspace ID found; set WorkspaceID or the - googlecloud: no project found; set Project, set the - No workspace ID found. Set the WorkspaceId option or the ANTHROPIC_AWS_WORKSPACE_ID environment variable. - No base URL could be determined. Set the BaseUrl option, the ANTHROPIC_AWS_BASE_URL environment variable, or provide a region via AwsRegion / AWS_REGION / AWS_DEFAULT_REGION. Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/3cfb2242c7adaa0dc3b8c2ad1972d9b47d820765/internal/awsauth/awsauth.go (official_docs, unknown, documented_behavior): Resolution errors for workspace ID, region and base URL. - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/3cfb2242c7adaa0dc3b8c2ad1972d9b47d820765/aws/aws.go (official_docs, unknown, documented_behavior): WorkspaceID sent as anthropic-workspace-id header; env names ANTHROPIC_AWS_WORKSPACE_ID, ANTHROPIC_AWS_BASE_URL. - https://raw.githubusercontent.com/anthropics/anthropic-sdk-go/3cfb2242c7adaa0dc3b8c2ad1972d9b47d820765/googlecloud/auth.go (official_docs, unknown, documented_behavior): Google Cloud env var names and no workspace/project errors. - https://raw.githubusercontent.com/anthropics/anthropic-sdk-csharp/2beeb9f9b402b1cdb8030e7cdc38cc6cae5d42aa/src/Anthropic.Aws/AnthropicAwsClient.cs (official_docs, unknown, documented_behavior): C# AnthropicAwsClient raises the equivalent workspace ID and base URL messages. Search phrasings: anthropic aws client no workspace ID found ANTHROPIC_AWS_WORKSPACE_ID; anthropic google cloud client no project found workspace Evidence basis (self-declared by the contributing chat client): public_source.