Historical forks (Berlin → Pectra)

Status: Live on the public MCP. One catalogue page for past execution-layer hardforks.

Why this page exists

The probe exposes the Berlin→Glamsterdam lineage so agents can answer “when did this EIP appear?” and run simulations on any named fork. Human docs use three buckets:

Bucket	Doc page	Probe role
Preview / upcoming	Glamsterdam (later e.g. Hegota)	preview
Current mainnet EL	Fusaka	current
History	This page (Berlin → Pectra)	historical

Historical forks are generic run targets: { "baseHardfork": "<id>", "eips": [] } on the three run tools. Use eipIntroductions from Describe Capabilities for when-did-this-activate facts. Pectra+ also enables set-code type-4 txs via Run transaction authorizationList (fork feature, not a catalogue twin). Current-mainnet twins on Fusaka follow when that role rotates.

From Shapella on, the catalog id is the combined upgrade name; the EL city name is an alias. Paris has no Shapella-style portmanteau — paris stays canonical (aliases merge, the-merge).

Not in the catalogue: difficulty-bomb delay forks (Arrow Glacier, Gray Glacier, Muir Glacier, …) and blob-parameter-only upgrades — the lineage jumps Berlin → London → Paris on mainnet.

Single fork vs compare

Single fork: pick the fork the user named and run once (e.g. PUSH0 bytecode on shapella only).

Compare (when the user asks):

1. Look up the EIP or keyword in eipIntroductions.
2. Note introducedAt.
3. Run the same verb on predecessorFork(introducedAt) and on introducedAt.

Examples (compare prompts):

• EIP-1559 → london → compare berlin then london on the same Run transaction (fee market / paid gasUsed).
• PUSH0 (3855) → shapella → compare paris then shapella (0x5f00 on bytecode).
• ModExp repricing (7883) → fusaka → compare pectra then fusaka (EIP-7883).

Upgrade mascots

From Paris (The Merge) on, Ethereum upgrades often have a community mascot (EIP-8066). The probe exposes them on namedForks[].mascotEmoji and on run results as provenance.forkLabel / forkMascotEmoji. Berlin and London predate that process.

Fork	Mascot
Paris (Merge)	🐼
Shapella	🦉
Dencun	🐡
Pectra	🦒
Fusaka	🦓
Glamsterdam	🐻‍❄️

Lineage table (historical rows)

Order	baseHardfork	Mascot	Aliases	Notable activations (full lists in probe)
0	berlin	—	—	2565 ModExp, 2718 typed txs, 2929 cold/warm gas, 2930 access lists
1	london	—	—	1559 fee market, 3198 BASEFEE, 3529 refunds, 3541 initcode prefix
2	paris	🐼	merge, the-merge	3675 Merge (not replayable here), 4399 PREVRANDAO
3	shapella	🦉	shanghai	3855 PUSH0, 3860 initcode, 4895 withdrawals (limited in lab)
4	dencun	🐡	cancun	1153 transient storage, 5656 MCOPY, 4844 blobs (no blob txs in lab)
5	pectra	🦒	prague	7702 set-code (authorizationList on run_transaction), 2537 BLS precompiles, 7623 calldata

Floor: Berlin — Istanbul and earlier hardforks are out of scope for this MCP round.

Honesty

The lab does not replay Merge consensus, beacon withdrawals, or PeerDAS. Those introductions use coverage: consensus (EIP-3675, EIP-4895, EIP-6110, EIP-7251). EIP-4399 PREVRANDAO stays an execution opcode. Blob sidecars stay listed: out of this lab, and not consensus-only.

What you can ask your agent

Prompts to copy

Berlin vs London

On Berlin then London, run a plain 1 wei transfer to an existing account — when does gas pricing change for 1559?

Berlin vs London

On London versus Berlin, run bytecode that executes BASEFEE — does BASEFEE exist only on London?

Paris vs Shapella

On Paris versus Shapella, run bytecode PUSH0 — when does PUSH0 succeed?

Historical Forks Catalogue Changelog

Historical Forks Catalogue Changelog

1. v0.82026-10-06Historical fork runs are live on the hosted MCP.
2. v0.72026-09-29Merge, withdrawals, deposits, and max effective balance are coverage consensus.
3. v0.62026-09-177702 set-code documented as Pectra fork feature — not a catalogue EIP page.
4. v0.52026-09-17Historical forks still host advertised twins for adoption runs, not only compares.
5. v0.42026-09-17Pectra 7702 twin linked from the lineage table.
6. v0.32026-09-17Canonical ids from Shapella on are combined names (shapella, dencun, pectra); EL city names are aliases.
7. v0.22026-09-16Berlin and London added to lineage floor; glacier delay forks excluded from catalog.
8. v0.12026-09-16Combined historical doc; preview / mainnet / history trio.