Inference errors are typed at the boundary that owns the failure. Request validation and model capability errors happen before I/O; codecs classify wire shape; transport maps network and HTTP status; streams preserve the first terminal failure. Context cancellation is never converted into a retryable provider failure.

Layers

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flowchart TD
    V["request/model validation"] --> C["codec error"]
    C --> T["transport: network or API status"]
    T --> S["stream reader terminal state"]
    X["context cancellation/deadline"] --> T
    X --> S

Use errors.As for stable typed inspection and errors.Is for context and package sentinel errors. Error strings are diagnostics, not a protocol.

Cancellation

Invoke observes the caller context through request construction, authorization, HTTP, and bounded body reading. Stream uses the context for setup and leaves the long-lived body bounded by that context after response headers arrive. StreamReader.Close releases the body and is safe to call repeatedly.

Source and proof

Run go test ./failure ./transport ./stream ./gateway.