Add modelCapabilities override to all SDK languages

[SteveSandersonMS]

Summary

Same as #1022 but new PR needed as that one was prematurely merged in error.

Adds modelCapabilities parameter to the Node SDK's createSession and setModel APIs, allowing SDK consumers to override individual model capabilities (e.g., vision support) without specifying the full capabilities object.

Closes #994

Changes

• Codegen: Regenerated RPC types from runtime schema (adds modelCapabilities to model.switchTo)
• Types: Added ModelCapabilitiesOverride type, exported from index
• Session: createSession and setModel accept optional modelCapabilities
• E2E tests: Two tests verify vision toggle via setModel changes image processing behavior

Usage

` ypescript
// Override vision at session creation
const session = await client.createSession({
model: "my-byok-model",
provider: { type: "openai", baseUrl: "..." },
modelCapabilities: { supports: { vision: true } },
});

// Toggle vision mid-session
await session.setModel("my-byok-model", {
modelCapabilities: { supports: { vision: false } },
});
`

Testing

E2E tests run against a local runtime build and verify that:

• Starting with vision disabled then enabling via setModel causes image_url content to appear
• Starting with vision enabled then disabling via setModel causes image_url content to stop appearing

[Copilot]

Pull request overview

Adds cross-SDK support for overriding model capabilities (notably vision) at session creation and via setModel, aligning SDK APIs with updated runtime schema and validating behavior through E2E replay snapshots.

Changes:

• Regenerates RPC/session-event types to include modelCapabilities on model.switchTo (+ related schema-driven type updates).
• Exposes modelCapabilities overrides in Node/Python/Go/.NET session create/resume and model switching APIs.
• Adds E2E coverage (snapshots + tests) to verify that toggling vision via setModel changes whether image_url content is sent.

Show a summary per file

File	Description
test/snapshots/session_config/vision_enabled_then_disabled_via_setmodel.yaml	Adds replay snapshot for toggling vision off mid-session.
test/snapshots/session_config/vision_disabled_then_enabled_via_setmodel.yaml	Adds replay snapshot for toggling vision on mid-session.
test/harness/package.json	Bumps @github/copilot used by the shared E2E harness.
test/harness/package-lock.json	Lockfile update for harness dependency bump.
scripts/codegen/python.ts	Improves Python type modernization for nested Union[...] parsing.
scripts/codegen/csharp.ts	Adjusts C# RPC class naming to prefer schema title when present.
python/e2e/test_session_config.py	Adds Python E2E tests for vision capability overrides.
python/copilot/session.py	Adds model_capabilities support to CopilotSession.set_model().
python/copilot/generated/session_events.py	Regenerated session events (schema updates, renames, new fields).
python/copilot/generated/rpc.py	Regenerated RPC types including ModelCapabilitiesOverride and vision limits.
python/copilot/client.py	Adds Python-side override dataclasses + wiring into create/resume payloads.
python/copilot/init.py	Exports new Python override types from the package root.
nodejs/test/e2e/session_config.test.ts	Adds Node E2E tests validating vision toggling via setModel.
nodejs/src/types.ts	Adds modelCapabilities to SessionConfig and exports override type.
nodejs/src/session.ts	Extends setModel() options to accept modelCapabilities.
nodejs/src/index.ts	Re-exports ModelCapabilitiesOverride.
nodejs/src/generated/session-events.ts	Regenerated session event typings (idle/background tasks + UI completion payloads).
nodejs/src/generated/rpc.ts	Regenerated RPC types incl. ModelCapabilities(Override) + vision limits.
nodejs/src/client.ts	Sends modelCapabilities in session.create and session.resume RPC payloads.
nodejs/package.json	Bumps Node SDK dependency on @github/copilot.
nodejs/package-lock.json	Lockfile update for Node SDK dependency bump.
go/types.go	Adds ModelCapabilities override to Go session config structs.
go/session.go	Adds ModelCapabilities override support to Session.SetModel.
go/rpc/generated_rpc.go	Regenerated Go RPC types incl. model capabilities overrides + vision limits.
go/internal/e2e/testharness/proxy.go	Updates exchange parsing to handle multimodal content (string vs array).
go/internal/e2e/session_config_test.go	Adds Go E2E tests for toggling vision via SetModel.
go/client.go	Wires ModelCapabilities into Go create/resume session requests.
dotnet/test/ToolsTests.cs	Updates tests to use StringContent after harness content type change.
dotnet/test/ToolResultsTests.cs	Updates tests to use StringContent after harness content type change.
dotnet/test/SessionConfigTests.cs	Adds .NET E2E tests for toggling vision via SetModelAsync.
dotnet/test/Harness/E2ETestBase.cs	Uses StringContent for extracting system message from captured requests.
dotnet/test/Harness/CapiProxy.cs	Updates harness message Content to JsonElement? + adds StringContent helper.
dotnet/src/Types.cs	Adds ModelCapabilities to session config types and JSON context.
dotnet/src/Session.cs	Extends SetModelAsync API to accept modelCapabilities.
dotnet/src/Generated/SessionEvents.cs	Regenerated events with updated payloads and removed idle backgroundTasks shape.
dotnet/src/Generated/Rpc.cs	Regenerated RPC types incl. ModelCapabilitiesOverride and vision limits.
dotnet/src/Client.cs	Wires ModelCapabilities into create/resume session RPC requests and JSON context.

Copilot's findings

Files not reviewed (2)

• nodejs/package-lock.json: Language not supported
• test/harness/package-lock.json: Language not supported

• Files reviewed: 29/37 changed files
• Comments generated: 2

[github-actions]

Generated by SDK Consistency Review Agent for issue #1029

[github-actions]

Cross-SDK Consistency Review ✅

This PR maintains full cross-language parity for the modelCapabilities / ModelCapabilitiesOverride feature.

SDK	SessionConfig	ResumeSessionConfig	setModel	Type exported
Node.js	✅ (this PR)	✅ (this PR)	✅ (this PR)	✅
Python	✅ (from #1022)	✅ (from #1022)	✅ (from #1022)	✅
Go	✅ (this PR)	✅ (this PR)	✅ (SetModelOptions)	✅
.NET	✅ (this PR)	✅ (this PR)	✅ (SetModelAsync)	✅

The ModelCapabilitiesOverride type structure (with supports.vision, supports.reasoningEffort, limits.*) is consistent across all four SDKs. Each SDK also exports the type from its public API surface using idiomatic naming (ModelCapabilitiesOverride in TS/.NET/Go, ModelCapabilitiesOverride in Python).

No consistency gaps found.

Generated by SDK Consistency Review Agent for issue #1029 · ◷