Added AnthropicOptions.fallbacks + wire types + response parsing gated on the opt-in — server-side fallback stays fully inert on every request that does not set the option.
Coding-agent surfaces the feature via providers.anthropic.serverSideFallback (default off). When enabled, Fable/Mythos requests inject fallbacks: [{ model: claude-opus-4-8 }]; caller-supplied fallbacks always win.
transformMessages centrally strips persisted fallback blocks on cross-provider hops and non-official Anthropic replays so a stored fallback turn never wedges downstream converters. Retry resets restore output.model to the requested id.
Fixes#4177
Forwarded persisted provider stream timeout settings into model requests so slow local LLM streams can widen or disable first-event and idle watchdogs without environment variables.
Fixes#3878
- Added textVerbosity configuration schema to allow user control over model response length.
- Integrated textVerbosity into settings-aware stream processing for "openai-responses" and "openai-codex-responses" APIs.
- Updated settings stream tests to verify that verbosity settings correctly apply while respecting caller overrides.
AgentSession.#buildAdvisorRuntime constructed the advisor Agent without the provider-shaping options the SDK installs on the main agent: the streamFn wrapper that applies providers.openrouterVariant / providers.antigravityEndpoint / providers.maxInFlightRequests / model.loopGuard.*, the onPayload/onResponse/onSseEvent hooks, the shared providerSessionState map, transformProviderContext (snapcompact, secret obfuscation, image clamping), and a stable promptCacheKey. Advisor turns therefore dropped the OpenRouter sticky-routing variant suffix, used a different prompt_cache_key than the main turn, and skipped the per-session provider hooks — producing intermittent OpenRouter response-cache misses across consecutive advisor calls.
Extract the inline streamFn wrapper in sdk.ts into a shared createSettingsAwareStreamFn helper (packages/coding-agent/src/session/settings-stream-fn.ts) and pass it (plus transformProviderContext) through AgentSessionConfig as advisorStreamFn / transformProviderContext. #buildAdvisorRuntime now hands the advisor Agent the same streamFn, hooks, providerSessionState, promptCacheKey (= advisor session id), and transformProviderContext as the main turn. Adds getAdvisorAgent() accessor on AgentSession for diagnostics and parity tests.
Fixes#3639
roboomp