EIP-7883 — ModExp Gas Cost Increase
Status: Runnable locally (stdio v0.1, self-hosted). Public MCP not launched yet — use the website exploration today.
What became possible
How are ModExp gas costs changing with Fusaka? EIP-7883 recalibrates the ModExp precompile (0x05) gas formula so cost better reflects real work — especially for larger exponents. EIP-7823 (same fork) tightens input bounds.
The MCP server runs caller-supplied bytecode that invokes ModExp (typically a CALL to 0x05 with the standard ABI: three 32-byte length headers plus B, E, M bodies). Compare gas on Prague vs Osaka to see the repricing — or sweep input sizes on Osaka alone to understand the curve.
What you can ask your agent
Connect the MCP server, then try prompts like:
- “How much gas does ModExp use for a 32-byte RSA-style exponent on Osaka vs Prague?”
- “Run ModExp with these B/E/M hex fields on Osaka and tell me if EIP-7823 rejects the input.”
- “I'm curious how Fusaka changed ModExp — show me gas for the same payload before and after.”
- “Compare ModExp gas for my airdrop verification input on pre-Fusaka and post-Fusaka rules.”
These are inspiration prompts — play, understand, or check your inputs.
What the server does
| Step | Action | Purpose |
|---|---|---|
| 1 | Discover support | Confirm 7883 catalog entry; read ModExp input layout |
| 2 | Run bytecode | Execute CALL bytecode on osaka (or prague then osaka for compare) |
Fork caveat
ModExp repricing is active on Osaka (mainnet today). For before/after, run the same bytecode on prague, then osaka, and diff gasUsed. The catalog exposes comparison: { baselineForkId: "prague", previewForkId: "osaka" }.
Twins and spec
| Link | |
|---|---|
| Website exploration (interactive textbook) | EIP-7883 on feelyourprotocol.org |
| Canonical spec | EIP-7883 |
| Coverage index | Coverage |
Changelog
- v0.12026-08-31Initial catalogue page — ModExp gas repricing, Prague/Osaka compare, twin link.