Add experimental multi-provider BYOK registry config across all six SDKs

[stephentoub]

Why

The CLI protocol recently gained a named-provider / provider-model registry (copilot-agent-runtime#9864): providers and models on session create/resume. This lets an app register several BYOK providers, declare multiple models per provider, and bind custom agents to provider-qualified model ids. None of the SDKs surfaced it yet, so SDK consumers couldn't use multi-provider configurations. This PR closes that gap in all six SDKs (.NET, Node, Python, Go, Rust, Java).

What

• New config surface in every SDK: NamedProviderConfig (name, type, wireApi, baseUrl, apiKey/bearerToken, headers, azure) and ProviderModelConfig (id, provider, wireModel, token limits, capabilities), wired onto the session config used for create and resume. Custom agents can reference provider-qualified model ids (e.g. alpha/sonnet).
• Marked experimental using each language's existing convention ([Experimental] / @CopilotExperimental / Experimental: doc markers / etc.). The whole feature should be treated as experimental for now.
• Java AgentInfo parity: added model to the hand-written com.github.copilot.rpc.AgentInfo so it matches the agent-info type already exposed by the other five SDKs (the field deserializes from the existing session.agent.list payload, so no protocol change).
• End-to-end tests in all six SDKs validating that multiple providers, multiple models per provider, and custom agents bound to those models coexist in one session, launch, and route a turn to the correct provider with the configured wire model, X-Provider header, and credential.

Notes for reviewers

• Snapshots are shared across all six SDKs. Each language's harness derives the snapshot folder/file from the test file and test names, so all six suites replay the same four YAML fixtures under test/snapshots/multi_provider_registry/. There are no per-language snapshots.
• Routing tests use openai/completions providers pointed at the replay proxy (only /chat/completions is captured); providers are distinguished on the wire by a per-provider X-Provider header. The agent-binding test additionally includes an anthropic provider purely to prove heterogeneous providers coexist (no dispatch).
• All six E2E suites pass locally (4 tests each), and the Java AgentInfoTest was extended for the new model field (7/7).

Test plan

• .NET: dotnet test E2E MultiProviderRegistryE2ETests - 4/4
• Node: npm run test -- multi_provider_registry - 4/4
• Python: pytest e2e/test_multi_provider_registry_e2e.py - 4/4
• Go: go test -run TestMultiProviderRegistryE2E ./internal/e2e - 4/4
• Rust: cargo test --test e2e multi_provider_registry - 4/4
• Java: mvn test -Dtest=MultiProviderRegistryE2ETest - 4/4, plus AgentInfoTest 7/7; spotless clean

[Copilot]

Pull request overview

This PR adds an experimental multi-provider BYOK registry surface (providers + models) to each SDK’s session create/resume configuration, enabling apps to register multiple named providers, define multiple models per provider, and bind custom agents to provider-qualified model IDs (e.g. alpha/sonnet). It also adds Java parity for AgentInfo.model and introduces cross-SDK E2E coverage using shared replay snapshots.

Changes:

• Added new provider/model registry config types and plumbed providers/models through session create + resume wire payloads across Rust, Go, Python, Node, Java, and .NET.
• Added/updated E2E tests in each language plus shared replay fixtures under test/snapshots/multi_provider_registry/.
• Extended Java AgentInfo with a model field and updated tests accordingly.

Show a summary per file

File	Description
test/snapshots/multi_provider_registry/should_route_delta_turbo_turn_to_its_provider_and_wire_model.yaml	Adds replay fixture for routing the delta/turbo selection to its wire model.
test/snapshots/multi_provider_registry/should_route_alpha_sonnet_turn_to_its_provider_and_wire_model.yaml	Adds replay fixture for routing the alpha/sonnet selection to its wire model.
test/snapshots/multi_provider_registry/should_route_alpha_haiku_turn_to_its_provider_and_wire_model.yaml	Adds replay fixture for routing the alpha/haiku selection to its wire model.
test/snapshots/multi_provider_registry/should_register_multiple_providers_with_custom_agents_bound_to_their_models.yaml	Adds replay fixture used by the registry + agent-binding test case.
rust/tests/e2e/multi_provider_registry.rs	Adds Rust E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
rust/tests/e2e.rs	Registers the new Rust E2E module.
rust/src/wire.rs	Extends Rust wire DTOs for session create/resume with providers and models.
rust/src/types.rs	Introduces NamedProviderConfig + ProviderModelConfig and wires them into SessionConfig / ResumeSessionConfig plus serialization tests.
python/e2e/test_multi_provider_registry_e2e.py	Adds Python E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
python/copilot/session.py	Adds Python TypedDict definitions for NamedProviderConfig and ProviderModelConfig.
python/copilot/client.py	Plumbs providers and models through create_session / resume_session and adds snake_case→wire conversion helpers.
python/copilot/init.py	Exports NamedProviderConfig and ProviderModelConfig from the public Python package surface.
nodejs/test/e2e/multi_provider_registry.e2e.test.ts	Adds Node E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
nodejs/src/types.ts	Adds NamedProviderConfig + ProviderModelConfig and exposes them on SessionConfigBase.
nodejs/src/index.ts	Re-exports the new Node types from the SDK entry point.
nodejs/src/client.ts	Includes providers and models in Node session create/resume RPC payloads.
java/src/test/java/com/github/copilot/MultiProviderRegistryE2ETest.java	Adds Java E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
java/src/test/java/com/github/copilot/MultiProviderConfigTest.java	Adds Java unit tests for JSON serialization and cloning behavior of the new config types + SessionConfig/ResumeSessionConfig integration.
java/src/test/java/com/github/copilot/AgentInfoTest.java	Extends Java tests for the new AgentInfo.model field.
java/src/main/java/com/github/copilot/SessionRequestBuilder.java	Plumbs providers and models from config objects into create/resume request DTOs.
java/src/main/java/com/github/copilot/rpc/SessionConfig.java	Adds experimental providers/models fields + getters/setters + cloning support.
java/src/main/java/com/github/copilot/rpc/ResumeSessionRequest.java	Adds experimental providers/models fields to the internal resume request DTO.
java/src/main/java/com/github/copilot/rpc/ResumeSessionConfig.java	Adds experimental providers/models fields + getters/setters + cloning support.
java/src/main/java/com/github/copilot/rpc/ProviderModelConfig.java	Introduces Java ProviderModelConfig (experimental) with fluent setters and JSON mapping.
java/src/main/java/com/github/copilot/rpc/NamedProviderConfig.java	Introduces Java NamedProviderConfig (experimental) with fluent setters and JSON mapping.
java/src/main/java/com/github/copilot/rpc/CreateSessionRequest.java	Adds experimental providers/models fields to the internal create request DTO.
java/src/main/java/com/github/copilot/rpc/AgentInfo.java	Adds model to Java AgentInfo for parity with other SDKs.
go/types.go	Adds Go NamedProviderConfig + ProviderModelConfig plus SessionConfig/ResumeSessionConfig fields and request struct plumbing.
go/internal/e2e/multi_provider_registry_e2e_test.go	Adds Go E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
go/client.go	Plumbs Providers and Models into Go create/resume session RPC requests.
dotnet/test/E2E/MultiProviderRegistryE2ETests.cs	Adds .NET E2E coverage for registry creation, agent bindings, and per-provider routing assertions.
dotnet/src/Types.cs	Adds .NET NamedProviderConfig + ProviderModelConfig and exposes them on SessionConfigBase.
dotnet/src/Client.cs	Plumbs Providers/Models into .NET create/resume session requests and registers types for JSON source-gen.

Copilot's findings

• Files reviewed: 33/33 changed files
• Comments generated: 0

[github-actions]

Cross-SDK Consistency Review ✅

This PR adds the multi-provider BYOK registry config (NamedProviderConfig + ProviderModelConfig) and the AgentInfo.model parity fix across all six SDKs. Here's what the consistency review found:

✅ NamedProviderConfig — fully consistent

All six SDKs expose identical wire-level fields (name, type, wireApi, baseUrl, apiKey, bearerToken, azure, headers). Each language applies its own naming convention correctly:

Field (wire)	TypeScript	Python	Go	.NET	Java	Rust
name	name	name	Name	Name	name	name
type	type	type	Type	Type	type	provider_type (reserved kw → #[serde(rename="type")])
wireApi	wireApi	wire_api	WireAPI	WireApi	wireApi	wire_api
baseUrl	baseUrl	base_url	BaseURL	BaseUrl	baseUrl	base_url
apiKey	apiKey	api_key	APIKey	ApiKey	apiKey	api_key
bearerToken	bearerToken	bearer_token	BearerToken	BearerToken	bearerToken	bearer_token
azure	azure	azure	Azure	Azure	azure	azure
headers	headers	headers	Headers	Headers	headers	headers

✅ ProviderModelConfig — fully consistent

All nine fields (id, provider, wireModel, modelId, name, maxPromptTokens, maxContextWindowTokens, maxOutputTokens, capabilities) are present in every SDK with correct language-idiomatic naming.

✅ providers / models on SessionConfig and ResumeSessionConfig — fully consistent

All SDKs wire both fields for both create and resume paths.

✅ Experimental markers — language-idiomatic and consistently applied

SDK	Convention used
.NET	[Experimental(Diagnostics.Experimental)] on type and members
Node.js	@experimental JSDoc tag
Go	// Experimental: ... doc comments on fields and types
Rust	**Experimental.** leading paragraph in doc comments
Python	**Experimental.** in docstrings
Java	@CopilotExperimental annotation on class and methods

✅ AgentInfo.model parity fix

Java's hand-written AgentInfo was the only SDK that lacked the model field. The other five SDKs expose it through their generated types (e.g., AgentInfo.model in Go's rpc.go, Model in .NET's Rpc.cs, model in Node.js's rpc.ts, Rust's generated/api_types.rs). Adding it to Java correctly closes the parity gap without any protocol change.

✅ Rust builder pattern

NamedProviderConfig::new(name, base_url) and ProviderModelConfig::new(id, provider) are Rust-idiomatic; no equivalent is needed in other SDKs, which use object/struct literals or fluent setters.

Summary

No cross-SDK inconsistencies found. The feature is implemented in all six languages with consistent wire semantics, correct language idioms, and appropriate experimental markers.

Generated by SDK Consistency Review Agent for issue #1718 · sonnet46 3.9M · ◷