Summary

Describe the problem and fix in 2–5 bullets:

• Problem: GatewayBrowserClient reconnect flow used inline magic numbers (800, 1.7, 15000, 750) in multiple places.
• Why it matters: reconnect behavior tuning/review was harder because the same values were repeated without semantic names.
• What changed: extracted reconnect timing knobs into named constants (INITIAL_RECONNECT_BACKOFF_MS, RECONNECT_BACKOFF_MULTIPLIER, MAX_RECONNECT_BACKOFF_MS, CONNECT_QUEUE_DELAY_MS) and replaced inline literals.
• What did NOT change (scope boundary): no reconnect algorithm/ordering changes, no protocol changes, no behavior changes.

Change Type (select all)

• Bug fix
• Feature
• Refactor
• Docs
• Security hardening
• Chore/infra

Scope (select all touched areas)

• Gateway / orchestration
• Skills / tool execution
• Auth / tokens
• Memory / storage
• Integrations
• API / contracts
• UI / DX
• CI/CD / infra

Linked Issue/PR

• Closes UI: Extract magic numbers in GatewayBrowserClient reconnect logic into named constants #30402
• Related TUI: make missing API key fallback errors actionable #31585

User-visible / Behavior Changes

None.

Security Impact (required)

• New permissions/capabilities? (No)
• Secrets/tokens handling changed? (No)
• New/changed network calls? (No)
• Command/tool execution surface changed? (No)
• Data access scope changed? (No)
• If any Yes, explain risk + mitigation:

Repro + Verification

Environment

• OS: macOS
• Runtime/container: local dev checkout
• Model/provider: N/A
• Integration/channel (if any): Control UI gateway client
• Relevant config (redacted): default

Steps

1. Open ui/src/ui/gateway.ts.
2. Inspect reconnect queue/backoff code paths (backoffMs init, growth/cap, reset, connect queue delay).
3. Verify literals are replaced by named constants and references compile.

Expected

• Reconnect constants are named and centralized.

Actual

• Constants are now declared once and reused in reconnect logic.

Evidence

Attach at least one:

• Failing test/log before + passing after
• Trace/log snippets
• Screenshot/recording
• Perf numbers (if relevant)

Human Verification (required)

What you personally verified (not just CI), and how:

• Verified scenarios: reconnect code paths now reference named constants only.
• Edge cases checked: backoff reset after successful connect still uses initial backoff value.
• What you did not verify: live browser reconnect timing against a running gateway.

Compatibility / Migration

• Backward compatible? (Yes)
• Config/env changes? (No)
• Migration needed? (No)
• If yes, exact upgrade steps:

Failure Recovery (if this breaks)

• How to disable/revert this change quickly: revert commit 947609308.
• Files/config to restore: ui/src/ui/gateway.ts.
• Known bad symptoms reviewers should watch for: unexpected reconnect delay changes (should not occur; value-only extraction).

Risks and Mitigations

List only real risks for this PR. Add/remove entries as needed. If none, write None.

• Risk: accidental constant mismatch could alter reconnect cadence.
  • Mitigation: constants preserve original literal values exactly.