Track live open canvas snapshots

[jmoseley]

Summary

• update the Rust session event loop to keep Session::open_canvases() current from live session.canvas.opened events
• upsert repeated canvas instance IDs while preserving snapshot order
• add coverage for malformed payload tolerance, live add, and live upsert behavior

Validation

• cargo test --features test-support session_canvas_opened_updates_open_canvas_snapshots
• cargo test --features test-support resume_session_sends_canvas_fields_and_captures_open_canvases
• cargo +nightly-2026-04-14 fmt --check

Paired github-app branch pins this SDK WIP via .sdk-upstream-sha until the normal sync lands.

[Copilot]

Pull request overview

This PR updates the Rust SDK session event loop to keep Session::open_canvases() synchronized with live session.canvas.opened notifications, while preserving snapshot ordering when the same canvas instance is re-opened. It also adds Rust test coverage to validate malformed-payload tolerance, live additions, and live upserts.

Changes:

• Share an open_canvases snapshot store with the session event loop and update it on session.canvas.opened notifications via an upsert helper.
• Populate open_canvases from session.resume responses while keeping the Session API unchanged.
• Add a new Rust test covering live updates and upsert behavior for repeated instanceIds.

Show a summary per file

File	Description
rust/src/session.rs	Tracks and upserts open canvas snapshots on session.canvas.opened events; wires shared state into the event loop and resume path.
rust/tests/session_test.rs	Adds a new test validating malformed event tolerance plus live add/upsert snapshot behavior.

Copilot's findings

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

[SteveSandersonMS]

@jmoseley Looks good. I'm guessing a similar fix is also needed for the other languages. Is that correct?

[jmoseley]

Yes, will work on that.

[github-actions]

Cross-SDK Consistency Review ✅

This PR implements live session.canvas.opened tracking consistently across all five SDK implementations: Node.js/TypeScript, Python, Go, .NET, and Rust.

SDK	Event handler	Upsert logic	Malformed payload warning	Tests
Node.js	✅ upsertOpenCanvasFromEvent	✅	✅ console.warn	✅
Python	✅ _upsert_open_canvas	✅	✅ logger.warning	✅
Go	✅ updateOpenCanvasesFromEvent	✅	✅ fmt.Printf	✅
.NET	✅ UpdateOpenCanvasesFromEvent	✅	✅ LogWarning	✅
Rust	✅ upsert_open_canvas_snapshot	✅	✅ warn!	✅

Behavioral parity confirmed:

• All SDKs validate required fields (instanceId, canvasId, extensionId, availability) and log a warning on malformed payloads
• All SDKs upsert by instanceId (in-place replace preserving order, or append if new)
• All SDKs update the snapshot cache before broadcasting the event to subscribers
• The Rust implementation additionally handles the race between session.resume and live events with upsert semantics — a nice correctness improvement
• Updated docstrings/comments in all SDKs consistently describe the new behavior

No consistency gaps found. 🎉

Generated by SDK Consistency Review Agent for issue #1447 · ● 3.7M · ◷