[diegosouzapw]

What

Adds per-request Auto-Combo routing controls via two response-safe request headers, so a caller can steer an auto combo on a single request without mutating its stored config.

Header	Accepts	Effect
X-OmniRoute-Mode	preset alias (fast, balanced, quality, cheap, reliable, offline) or a raw mode-pack name (ship-fast, cost-saver, quality-first, offline-friendly, reliability-first)	Overrides scoring weights for this request. balanced/default → default weights. Unknown values ignored.
X-OmniRoute-Budget	positive USD number	Hard per-request cost ceiling — candidates above it are filtered before selection, falling back to the cheapest healthy one. Garbage ignored.

curl -sS localhost:20128/v1/chat/completions \
  -H "X-OmniRoute-Mode: fast" -H "X-OmniRoute-Budget: 0.05" \
  -d '{"model":"auto","messages":[{"role":"user","content":"hi"}]}'

Why this shape

The auto-combo engine already consumes config.modePack and config.budgetCap (weights resolution + budget filtering with cheapest-fallback both already exist in engine.ts). The only gap was a per-request entry point. So this PR adds:

• Pure resolvers resolveRequestModePack / parseRequestBudgetCap in open-sse/services/autoCombo/requestControls.ts (no engine changes).
• Header parsing in src/sse/handlers/chat.ts, threaded through relayOptions.
• Precedence in combo.ts auto path: request header overrides stored config for that request only; absent/invalid header preserves the combo's saved config.

Scope note

This closes the input-side children of umbrella #5811 (#6023 budget-cap, #6024 latency-vs-quality presets, #6025 mode-pack header). The remaining umbrella child #6022 (X-OmniRoute-Decision trace response header) is a separate output-side threading job (combo selection → chatCore response-header builders) and is intentionally not in this PR. #6010 (fastest routing + MCP tool) already shipped in #6011.

Tests / validation (Hard Rule #18)

• TDD: tests/unit/auto-combo-request-controls-6024.test.ts (5) — presets, aliases, raw pack names, balanced→default, unknown-ignored, budget parse/reject. Green.
• typecheck:core clean · check:cycles clean · check:docs-sync clean · eslint clean on touched files · auto-combo-engine + auto-combos-suffixes-4235 suites green.

Docs: docs/routing/AUTO-COMBO.md → new "Per-Request Controls (headers)" section.

[gemini-code-assist]

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.