perf(viz): lazy-load SignalR via dynamic import (−54 KB main bundle)

[WomB0ComB0]

Summary

The main bundle has been creeping against the 800 KiB cap (98.8% after #79). The next non-trivial main-bundle feature would have failed CI. Defer @microsoft/signalr until start() runs.

Bundle delta

Asset	Before	After	Δ
main	809.0 KB	753.6 KB	−55 KB
esm (new lazy)	—	55.3 KB	+55 KB
sensor	20.5 KB	20.5 KB	0
% of cap	98.8 %	92.0 %	−6.8 pp

Mechanics

• Eager import { HubConnectionBuilder, LogLevel } from '@microsoft/signalr' → import type { HubConnection } (type-only, zero runtime cost).
• connection is a module-scoped let HubConnection | null, initialized inside start() via await import('@microsoft/signalr'). Subsequent reconnects reuse the cached module AND the same HubConnection instance.
• Handler registration moved into _wireConnection(c) so it runs once after the lazy build.

Cost

~50 ms one-time chunk fetch on first start(). Overlaps with the existing async boot path (_autoSpawnIfEmpty, terrain loading) so user-visible startup time is unchanged in practice.

Test plan

• npm run build passes; main bundle 753.6 KB, well under 819.2 KB cap
• tsc --noEmit clean
• Browser smoke test: reload / and confirm SignalR connection comes up; check Network tab for the deferred esm-*.js chunk
• CI: client-budget reports 92% of budget (or whatever measure step hits)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Refactor
  • Optimized real-time communication initialization by deferring module loading to first use instead of application startup.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 4420f738-1e32-4cdc-b2d4-c8e079e3a524

📥 Commits

Reviewing files that changed from the base of the PR and between ff4b695 and 6546185.

📒 Files selected for processing (1)

• CLAUDE.md

📝 Walkthrough

Walkthrough

SignalR initialization has been refactored from eager loading at module startup to lazy loading on first start() call. Event handlers are now wired through a dedicated _wireConnection() helper function, and the runtime module is imported dynamically, improving startup performance and deferring dependencies.

Changes

Cohort / File(s)	Summary
SignalR Lazy Initialization src/ResQ.Viz.Web/client/app.ts	Converted SignalR from eager module-load initialization to lazy on-demand initialization. Extracted connection event wiring into _wireConnection() helper. Replaced static import with dynamic import('@microsoft/signalr') during first start() call. Connection instance is now cached for reuse on subsequent starts.

Sequence Diagram(s)

sequenceDiagram
    participant Client as App Client
    participant Module as SignalR Module
    participant Hub as HubConnection

    Note over Client,Hub: Previous (Eager Initialization)
    Client->>Module: import at module load
    Module-->>Client: SignalR library
    Client->>Hub: new HubConnectionBuilder().build()
    Hub-->>Client: connection instance
    Note over Client: Connection ready but unused until start()

    Note over Client,Hub: New (Lazy Initialization)
    Client->>Client: Module loads, connection = null
    Client->>Client: start() called
    Client->>Module: dynamic import('@microsoft/signalr')
    Module-->>Client: SignalR library
    Client->>Hub: new HubConnectionBuilder().build()
    Hub-->>Client: connection instance
    Client->>Client: _wireConnection(connection)
    Note over Client: Event handlers wired
    Client->>Hub: connect()

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Poem

🐰 A lazy rabbit knows the way,
Why rush your load on startup's day?
We've deferred the SignalR dance,
Till first start() gives us a chance—
Cached connections, handlers wired tight,
Lazy loading done just right! 🎯

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: lazy-loading SignalR via dynamic import with a quantified performance benefit (−54 KB main bundle reduction).
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/defer-signalr

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@src/ResQ.Viz.Web/client/app.ts`:
- Around line 743-748: The project currently uses SignalR client code
(HubConnectionBuilder, LogLevel and the connection creation logic) that is fine,
but package.json declares "@microsoft/signalr": "^10.0.0"; update
src/ResQ.Viz.Web/package.json to set "@microsoft/signalr": "^8.0.0" to comply
with the TypeScript client requirement, then reinstall dependencies (npm/Yarn
install) so the HubConnectionBuilder/LogLevel imports resolve against SignalR
8.x.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6bd3c2bf-1eaf-4a8e-a578-a0095d9d2ac3

📥 Commits

Reviewing files that changed from the base of the PR and between a30f8a1 and ff4b695.

📒 Files selected for processing (1)

• src/ResQ.Viz.Web/client/app.ts

[gemini-code-assist]

Code Review

This pull request implements lazy loading for the SignalR runtime in the web client to improve initial load performance and reduce the main bundle size. The @microsoft/signalr dependency is now dynamically imported within the start function, and connection event handlers have been refactored into a _wireConnection helper. I have no feedback to provide.