Port Registrar: visualStudio agent migration + C# discovery client

[TalZaccai]

Why

The visualStudio bridge bound a hardcoded port (5680) and the VSIX dialed the matching hardcoded URI. This blocks the design goal of OS-assigned ephemeral ports brokered through PortRegistrar.

What changes

TS bridge (visualStudioActionHandler.ts) — rewritten to mirror the code and browser handlers:

• Async VisualStudioBridge.start(port = 0) factory; resolves on listening, rejects on first error.
• verifyClient Origin gate via a new originAllowlist.ts (loopback + absent/null; the C# ClientWebSocket sends no Origin header).
• Module-scoped shared bridge with refcount + start/close serialization, so rapid enable/disable cycles under a fixed-port override don't race into EADDRINUSE.
• Per-session registerPort("default", bridge.port), released in both updateAgentContext(false) and closeAgentContext.
• VISUALSTUDIO_BRIDGE_PORT escape hatch, mirroring the other agents.
• Multi-client + @system ports integration — bridge tracks all connected VS instances via Map<clientId, WebSocket> (instead of silently displacing on second connect); per-request clientId so a disconnect only fails that client's pending RPCs. Emits onClientCountChanged to the session context, surfaced via notifyClientCountChanged with a primary-session fanout so shared sessions don't double-count. send() routes to the most-recently-connected OPEN client (preserves legacy last-wins behavior).

C# bridge — VSIX is .NET Framework 4.7.2, can't reuse the TS discovery helper:

• New Bridge/BridgeDiscovery.cs (~190 LOC, single public method) speaks the agent-rpc discovery protocol over ClientWebSocket. Never throws — returns the discovered port or a fallback.
• AgentBridgeClient.cs drops the hardcoded URI; resolves the port on every reconnect, so a running VS adapts to an agent-server restart without an extension reload.
• Three env knobs (documented in README): AGENT_SERVER_PORT (default 8999), TYPEAGENT_VS_USE_DISCOVERY (default on), TYPEAGENT_VS_FALLBACK_PORT (default 5680).

Docs — README diagram + "Port discovery" / troubleshooting sections updated.

Validation

• pnpm --filter visualstudio-agent build — green.
• Prettier — clean.
• C# — compiles against the existing csproj; no new NuGet deps.

Notes

• Role is "default" (not "ws-bridge" from the design doc) to match code / browser and keep @system ports consistent.
• originAllowlist.ts is deliberately duplicated rather than shared — different scheme prefixes per agent, ~30 LOC.
• No new tests; this package has no existing TS or C# test harness. Happy to add layer-6/layer-8 coverage as a follow-up.

Reading order

1. src/originAllowlist.ts — origin policy.
2. src/visualStudioActionHandler.ts — TS bridge rewrite.
3. host/csharp/Bridge/BridgeDiscovery.cs — new discovery client.
4. host/csharp/Bridge/AgentBridgeClient.cs — hardcoded URI removed.
5. README.md — new env vars, discovery flow.

[Copilot]

Pull request overview

This PR migrates the Visual Studio agent bridge from a fixed, hardcoded port to OS-assigned ephemeral ports registered via PortRegistrar, and updates the VSIX host to discover the bridge port via the agent-server discovery channel on each reconnect.

Changes:

• Reworks the TS WebSocket bridge lifecycle to support ephemeral ports, origin gating, shared bridge reuse, and per-session port registration/release.
• Adds a .NET Framework discovery client (BridgeDiscovery) and updates AgentBridgeClient to resolve the bridge port dynamically on every reconnect.
• Updates Visual Studio agent docs and adds debug logging dependency.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
ts/pnpm-lock.yaml	Adds debug deps for visualStudio agent but also contains broad lockfile churn.
ts/packages/agents/visualStudio/src/visualStudioActionHandler.ts	New async bridge startup with origin gate, shared lifecycle/refcount, and PortRegistrar registration.
ts/packages/agents/visualStudio/src/originAllowlist.ts	New origin allowlist helper for the Visual Studio bridge.
ts/packages/agents/visualStudio/README.md	Documents discovery flow and new env knobs; updates architecture diagram/troubleshooting.
ts/packages/agents/visualStudio/package.json	Adds debug + @types/debug.
ts/packages/agents/visualStudio/host/csharp/VisualStudioTypeAgent.csproj	Includes the new discovery source file in the VSIX build.
ts/packages/agents/visualStudio/host/csharp/Bridge/BridgeDiscovery.cs	Implements discovery-channel lookup of (visualStudio, default) port with fallback behavior.
ts/packages/agents/visualStudio/host/csharp/Bridge/AgentBridgeClient.cs	Removes hardcoded URI; performs discovery on each reconnect attempt.

Files not reviewed (1)

• ts/pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (1)

ts/packages/agents/visualStudio/src/visualStudioActionHandler.ts:191

• send() has no timeout or cancellation path if the plugin never replies, so actions can hang forever even if the socket stays open. Adding a per-request timeout (and cleaning up the pending entry on timeout) would prevent stuck sessions and unbounded pending growth.

    async send(actionName: string, parameters: unknown): Promise<unknown> {
        if (!this.client) {
            throw new Error(`No host plugin connected on port ${this.port}`);
        }
        const id = `${Date.now()}-${Math.random().toString(36).slice(2)}`;
        return new Promise((resolve, reject) => {
            this.pending.set(id, (res) =>
                res.success
                    ? resolve(res.result)
                    : reject(new Error(res.error)),
            );
            this.client!.send(
                JSON.stringify({
                    id,
                    actionName,
                    parameters,
                } satisfies BridgeRequest),
            );
        });

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