Crate turnframe_provider 

turnframe-provider: the provider-neutral model layer of Turnframe (spec §20).

The core runtime never sees OpenAI-, Anthropic-, Gemini- or Bedrock-specific wire types (spec §0 rule 8). It speaks this crate’s normalized vocabulary:

• a request::ModelRequest describes one model call: purpose, messages, expected request::OutputSpec, read-only tools, limits and metadata;
• a response::ModelResponse carries the normalized answer, a response::FinishReason and response::TokenUsage;
• a stream::ModelStream delivers the same answer incrementally and stream::reconstruct rebuilds the full response deterministically;
• structured::parse_structured turns a response into a typed value all-or-nothing (spec I18): schema validation with deny-unknown semantics, then typed deserialization; a single malformed act rejects the whole output;
• error::ProviderError is the typed failure family, classified by error::RetryClass and free of secrets, request bodies and headers;
• provider::ModelProvider is the trait every adapter implements against a configured capabilities::ModelProfile; capabilities are declared per provider-model pair, never inferred from the brand (spec §20.3);
• router::PolicyRouter selects candidates by capability fit first, then tenant policy, then health and preference — and refuses to downgrade the structured-output requirement of a critical stage (spec §0 rule 9, §20.4);
• fallback::execute_with_fallback tries candidates in order, retries by class, records every attempt and never merges partial outputs (spec §20.7).

Concrete adapters live in sibling crates (turnframe-provider-openai, …) and prove themselves with the reusable [conformance] suite (feature conformance, spec §20.8).

Where the safety rules live

Rule	Where it is enforced
Model arrays are all-or-nothing (I18)	structured, stream::StreamAccumulator
No silent capability downgrade (§0.9)	purpose::ModelPurpose::requirements, router::PolicyRouter
Provider failure cannot repeat effects (I17)	fallback::FallbackStage is a required parameter
Secrets never reach prompts or logs (§25.2)	secret::ApiKey, secret::Redactor, error Display
Record every provider attempt (§20.7)	fallback::ProviderAttempt

Modules

capabilities

Capability model (spec §20.3) and per-model configuration profiles.

dialect

Rewriting a JSON Schema for a provider’s dialect, without weakening it.

error

The typed provider failure family and its retry classification (spec §24, §20.7).

fallback

Retry and fallback across candidates (spec §20.7, invariant I17).

ids

Identity newtypes of the provider layer.

prelude

The most used items, for use turnframe_provider::prelude::*.

provider

The trait every adapter implements (spec §20.1).

purpose

Normalized request purposes (spec §20.2) and what each one demands.

request

The normalized model request (spec §20.1).

response

The normalized model response (spec §20.1).

router

Provider selection (spec §20.4, §20.6, ADR-008).

secret

Credentials and redaction (spec §25.2).

stream

Incremental output and its deterministic reassembly (spec §18.5, §20.8).

structured

All-or-nothing structured parsing (invariant I18, spec §0 rule 6).

testing

Test doubles for the provider layer, always compiled.

trace

Every call a provider makes, as it went over the wire, for a person debugging a turn: the request with its prompts and schema, and what came back.