v2.4.0

• debug_mode: provider cost_details. When the provider reports a cost breakdown next to the total (OpenRouter's usage.cost_details — upstream_inference_cost, cache_discount), it's now surfaced under the cost_debug block. The displayed cost still uses the authoritative top-level cost; this is diagnostics only (the provider-vs-upstream split and any cache discount).
• debug_mode: web-search usage hint. A new web_search block flags whether the response carried server-side web-search citations (url_citation → OWUI sources), with a citation count and the domains. It's a heads-up that a provider-side search/tool surcharge may not be fully reflected in usage.cost (and BYOK engines bill outside the gateway entirely) — cross-check the Activity page. Detection only; the visible stats line is byte-identical.
• Docs: added a "Does the cost include tool / function / MCP calls?" section (Open-WebUI-orchestrated tool turns are summed across rounds into the shown cost; only a provider's own server-side tool surcharge outside usage.cost is invisible), and strengthened the estimate-mode caveat — a token×price estimate can drift several-fold under a gateway's routing / tier / cache pricing, so auto (native, authoritative) is preferred.