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+# Glamsterdam Write Prepayment — Phase 1
+
+Base: `ethereum/execution-specs@20f7f6271a720091e5fea0a82e7bc802866ae36a` (`forks/amsterdam`, 2026-08-26).
+
+## Decision gate
+
+Do not change consensus semantics and do not scan mainnet until the current
+execution-spec constants prove both invariants:
+
+1. `Osaka PASS -> Amsterdam FAIL -> Amsterdam + prepayment PASS` under the
+   same immutable child-call gas budget.
+2. Moving the repricing delta outside the child preserves the full Amsterdam
+   execution-resource charge.
+
+The executable proof is:
+
+`tests/amsterdam/eip8038_state_access_gas_cost_increase/test_write_prepayment_prototype.py`
+
+This phase is deliberately a branch-pinned accounting/liveness proof. It does
+**not** yet define a new transaction encoding or modify EVM consensus behavior.
+That implementation is the next gate only if this proof survives CI.
+
+## Minimal reproduction
+
+Use an existing non-zero storage slot and a child that executes:
+
+```text
+PUSH value
+PUSH key
+SSTORE
+```
+
+Two `PUSH` instructions cost 6 execution gas. Give the child an immutable
+5,006-gas budget.
+
+### Osaka
+
+For the first non-zero -> non-zero overwrite of a cold slot:
+
+```text
+2,100 cold storage access
++ 2,900 write component
++     6 stack setup
+= 5,006
+```
+
+Result: `PASS`.
+
+### Amsterdam, unchanged
+
+Current `forks/amsterdam` constants:
+
+```text
+2,100 COLD_STORAGE_ACCESS
++ 10,000 STORAGE_WRITE
++      6 stack setup
+= 12,106
+```
+
+The same immutable 5,006-gas child cannot execute it.
+
+Result: `FAIL`.
+
+### Amsterdam, write-prepaid
+
+Decompose the Amsterdam write price:
+
+```text
+10,000 STORAGE_WRITE
+= 2,800 historical write component
++ 7,200 repricing delta
+```
+
+Prepay the 7,200 delta outside the child and prewarm the storage key. The
+child sees:
+
+```text
+100 warm access
++ 2,800 historical write component
++     6 stack setup
+= 2,906
+```
+
+Result: `PASS` under the same 5,006-gas child budget.
+
+## Conservation proof
+
+The mechanism is invalid if it makes Amsterdam work cheaper globally.
+
+Ordinary cold Amsterdam storage write:
+
+```text
+2,100 cold access + 10,000 write = 12,100
+```
+
+Prepaid split:
+
+```text
+2,000 access-list storage-key prepayment
++ 100 warm access in the child
++ 7,200 write-repricing prepayment
++ 2,800 historical write component in the child
+= 12,100
+```
+
+Account access conserves independently:
+
+```text
+ordinary: 3,000 cold account access
+prepaid: 2,900 access-list address prepayment + 100 warm runtime access
+        = 3,000
+```
+
+Therefore the core state/call resource accounting is identical:
+
+```text
+ordinary Amsterdam core charge = 3,000 + 12,100 = 15,100
+prepaid Amsterdam core charge  = 3,000 + 12,100 = 15,100
+```
+
+The proposal changes **where** the repricing delta is charged, not whether it
+is charged.
+
+## Next gate
+
+Only after the phase-1 test passes:
+
+1. choose an explicit opt-in transaction representation for write vouchers;
+2. implement voucher state and rollback semantics in EELS;
+3. prove change -> restore -> change net-metering, nested-call revert/halt
+   behavior, duplicate voucher handling, and EIP-8037 state-gas interaction;
+4. run the Amsterdam/Osaka test suites and independent client fixtures;
+5. only then scan deployed mainnet bytecode for fixed-gas asset-release paths
+   and quantify value reachable only through failing paths.
+
+A mainnet value estimate before those gates would measure a hypothesis rather
+than a demonstrated compatibility failure.
diff --git a/tests/amsterdam/eip8038_state_access_gas_cost_increase/test_write_prepayment_prototype.py b/tests/amsterdam/eip8038_state_access_gas_cost_increase/test_write_prepayment_prototype.py
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+"""
+Executable phase-1 proof for Glamsterdam storage-write prepayment.
+
+The proof reads the Osaka and Amsterdam gas constants directly from the
+current execution-spec source tree. It must fail if those branch constants
+move enough to invalidate either the liveness transition or conservation
+claim.
+"""
+
+OSAKA_GAS_PATH = "src/ethereum/forks/osaka/vm/gas.py"
+AMSTERDAM_GAS_PATH = "src/ethereum/forks/amsterdam/vm/gas.py"
+
+
+def _uint_constant(path: str, name: str) -> int:
+    """Read a direct ``Uint(...)`` gas constant from a fork gas module."""
+    with open(path, encoding="utf-8") as source_file:
+        for line in source_file:
+            stripped = line.strip()
+            if stripped.startswith(f"{name}:") and "Uint(" in stripped:
+                raw_value = stripped.rsplit("Uint(", 1)[1].split(")", 1)[0]
+                return int(raw_value)
+    raise AssertionError(f"direct Uint constant not found: {path}:{name}")
+
+
+def _amsterdam_access_list_formulas_survive() -> None:
+    """Pin the access-list prepayment formulas used by the proof."""
+    with open(AMSTERDAM_GAS_PATH, encoding="utf-8") as source_file:
+        source = source_file.read()
+
+    assert "TX_ACCESS_LIST_ADDRESS: Final[ExecutionGas] = (" in source
+    assert "COLD_ACCOUNT_ACCESS - WARM_ACCESS" in source
+    assert "TX_ACCESS_LIST_STORAGE_KEY: Final[ExecutionGas] = (" in source
+    assert "COLD_STORAGE_ACCESS - WARM_ACCESS" in source
+
+
+def test_osaka_pass_amsterdam_fail_prepaid_pass() -> None:
+    """Prove one immutable child budget flips PASS -> FAIL -> PASS."""
+    osaka_warm = _uint_constant(OSAKA_GAS_PATH, "WARM_ACCESS")
+    osaka_cold_storage = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_ACCESS")
+    osaka_cold_write = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_WRITE")
+    osaka_push = _uint_constant(OSAKA_GAS_PATH, "VERY_LOW")
+
+    amsterdam_warm = _uint_constant(AMSTERDAM_GAS_PATH, "WARM_ACCESS")
+    amsterdam_cold_storage = _uint_constant(
+        AMSTERDAM_GAS_PATH, "COLD_STORAGE_ACCESS"
+    )
+    amsterdam_write = _uint_constant(AMSTERDAM_GAS_PATH, "STORAGE_WRITE")
+    amsterdam_push = _uint_constant(AMSTERDAM_GAS_PATH, "VERY_LOW")
+
+    legacy_write = osaka_cold_write - osaka_cold_storage - osaka_warm
+    fixed_child_gas = osaka_cold_write + 2 * osaka_push
+
+    osaka_required = osaka_cold_write + 2 * osaka_push
+    amsterdam_required = (
+        amsterdam_cold_storage + amsterdam_write + 2 * amsterdam_push
+    )
+    prepaid_required = amsterdam_warm + legacy_write + 2 * amsterdam_push
+
+    assert legacy_write == 2_800
+    assert fixed_child_gas == 5_006
+    assert osaka_required == 5_006
+    assert amsterdam_required == 12_106
+    assert prepaid_required == 2_906
+
+    assert osaka_required <= fixed_child_gas
+    assert amsterdam_required > fixed_child_gas
+    assert prepaid_required <= fixed_child_gas
+
+
+def test_prepayment_preserves_glamsterdam_execution_resource_charge() -> None:
+    """Prove repricing relocation preserves the full Amsterdam core charge."""
+    _amsterdam_access_list_formulas_survive()
+
+    osaka_warm = _uint_constant(OSAKA_GAS_PATH, "WARM_ACCESS")
+    osaka_cold_storage = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_ACCESS")
+    osaka_cold_write = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_WRITE")
+
+    amsterdam_warm = _uint_constant(AMSTERDAM_GAS_PATH, "WARM_ACCESS")
+    amsterdam_cold_account = _uint_constant(
+        AMSTERDAM_GAS_PATH, "COLD_ACCOUNT_ACCESS"
+    )
+    amsterdam_cold_storage = _uint_constant(
+        AMSTERDAM_GAS_PATH, "COLD_STORAGE_ACCESS"
+    )
+    amsterdam_write = _uint_constant(AMSTERDAM_GAS_PATH, "STORAGE_WRITE")
+
+    legacy_write = osaka_cold_write - osaka_cold_storage - osaka_warm
+    write_repricing_delta = amsterdam_write - legacy_write
+    access_list_address = amsterdam_cold_account - amsterdam_warm
+    access_list_storage_key = amsterdam_cold_storage - amsterdam_warm
+
+    baseline_call_access = amsterdam_cold_account
+    baseline_storage = amsterdam_cold_storage + amsterdam_write
+    baseline_core_charge = baseline_call_access + baseline_storage
+
+    prepaid_call_access = access_list_address + amsterdam_warm
+    prepaid_storage = (
+        access_list_storage_key
+        + amsterdam_warm
+        + write_repricing_delta
+        + legacy_write
+    )
+    prepaid_core_charge = prepaid_call_access + prepaid_storage
+
+    assert write_repricing_delta == 7_200
+    assert baseline_call_access == prepaid_call_access == 3_000
+    assert baseline_storage == prepaid_storage == 12_100
+    assert baseline_core_charge == prepaid_core_charge == 15_100
+
+
+def test_prepayment_is_not_a_subsidy() -> None:
+    """Prove the rescued local frame does not make global work cheaper."""
+    osaka_warm = _uint_constant(OSAKA_GAS_PATH, "WARM_ACCESS")
+    osaka_cold_storage = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_ACCESS")
+    osaka_cold_write = _uint_constant(OSAKA_GAS_PATH, "COLD_STORAGE_WRITE")
+
+    amsterdam_warm = _uint_constant(AMSTERDAM_GAS_PATH, "WARM_ACCESS")
+    amsterdam_cold_storage = _uint_constant(
+        AMSTERDAM_GAS_PATH, "COLD_STORAGE_ACCESS"
+    )
+    amsterdam_write = _uint_constant(AMSTERDAM_GAS_PATH, "STORAGE_WRITE")
+
+    legacy_write = osaka_cold_write - osaka_cold_storage - osaka_warm
+    write_repricing_delta = amsterdam_write - legacy_write
+    access_list_storage_key = amsterdam_cold_storage - amsterdam_warm
+
+    local_prepaid_sstore = amsterdam_warm + legacy_write
+    globally_paid_sstore = (
+        access_list_storage_key + local_prepaid_sstore + write_repricing_delta
+    )
+
+    assert local_prepaid_sstore == 2_900
+    assert globally_paid_sstore == amsterdam_cold_storage + amsterdam_write