TanStack Start vs Leptos

Real-world performance comparison based on identical SaaS dashboard implementations.

TanStack Start

TanStack Start

VPS

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A full-stack React framework from the creators of TanStack Query, Table, and Router. Built on Vinxi (a Vite-based meta-framework engine), TanStack Start brings the TanStack philosophy of type-safety and developer experience to server rendering. Features isomorphic data fetching with TanStack Router's loader patterns, full-stack type safety from database to component, and first-class support for server functions. The router provides file-based routing with powerful search param management. Still in beta but rapidly maturing, TanStack Start appeals to developers who love TanStack Query's patterns and want them extended to the full stack.

Leptos

Leptos

VPS (Rust)

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A full-stack Rust framework using fine-grained reactivity. Leptos compiles to WebAssembly for near-native browser performance, with server functions that run seamlessly on the backend. The framework's signal-based reactivity (similar to SolidJS) enables surgical DOM updates without a virtual DOM. Server functions provide RPC-like calls with full type safety between client and server. Leptos can render on the server and hydrate on the client. For Rust developers, Leptos offers a compelling way to build web applications with the safety and performance guarantees Rust is known for. The learning curve is steep but the results are impressive.

Performance Metrics

Lower is better for all metrics. Green indicates the faster framework.

Metric TanStack Start Leptos Winner
TTFB (p50) 50ms 44.85ms ▶
TTFB (p95) 55.06ms 50.07ms ▶
LCP (p50) 76ms 72ms ▶
LCP (p95) 84ms 78.2ms ▶
CLS 0 0 =
TBT 0 ms 0 ms =
LCP → TTFB N/A N/A -
LCP → Load Delay N/A N/A -
LCP → Load Duration N/A N/A -
LCP → Render Delay N/A N/A -
Performance Score 99 98 ◀
SEO Score 92 83 ◀
Accessibility Score 86 86 =
Best Practices Score 100 100 =

LLM Understanding (Claude Opus 4.5)

How efficiently Claude Opus 4.5 understands the codebase. Based on exploration + validation tests.

Metric TanStack Start Leptos Winner
Exploration Time 3649ms 3206ms ▶
Exploration Tokens 3993 2884 ▶
Files Examined 10 5 ▶
Validation Accuracy 93% 72% ◀
Time Per File 365ms 641ms ◀
Tokens Per File 3258 4138 ◀
Efficiency Score 31.16 29.54 ◀

LLM Understanding (Claude Haiku 4.5)

How efficiently Claude Haiku 4.5 understands the codebase. Based on exploration + validation tests.

Metric TanStack Start Leptos Winner
Exploration Time 3047ms 2152ms ▶
Exploration Tokens 4017 2880 ▶
Files Examined 10 5 ▶
Validation Accuracy 80% 61% ◀
Time Per File 305ms 430ms ◀
Tokens Per File 3263 4098 ◀
Efficiency Score 30.79 34.01 ▶

Build Metrics

Metric TanStack Start Leptos Winner
Bundle Size (JS) 382.4KB 1050.2KB ◀
Bundle Size (CSS) 22.8KB 0KB ▶
Build Time 0s 0s =
Dependencies 21 15 ▶

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