EIP complexity assessment

EIP-3855: PUSH0 instruction

Assessed in Shanghai / Shapella. The score describes the EIP text available at the assessment cutoff, not the EIP as it stands today.

RetrospectiveShanghai / ShapellaAssessment cutoff 2022-02-04Included by cutoffLayers: execution

LLM Completescore 6

Human Not available· Human complexity assessments were not produced for this fork; only the LLM assessment exists.

LLM assessment

Evaluated on: 2026-08-25 · Spec revision: 2021-09-22 · 6caab461df

Scope at the cutoff. At the recorded cutoff, EIP-3855 proposed activating a single new EVM opcode, PUSH0 (0x5f), at the fork boundary. The opcode has no immediate data, pops no stack items, pushes the value zero, and costs 2 gas under the existing verylow cost class. The proposal aimed to reduce bytecode size and reliance on context-sensitive zero-producing instructions, while noting that deployed code containing the formerly unavailable opcode could change behavior.

6LowLow

Evaluator: LLMChecklist v2
Confidence: High
Under-specified at assessment cutoff: No
Plausible range: 6–6 (Low)
Assessment cutoff: 2022-02-04 · EIP revision 6caab461df (2021-09-22)

Score bands · Checklist revision 2

Low <12
Medium 12–22
High ≥23

28 criteria scored 0–3 (4 in exceptional cases; cross-EIP interactions is uncapped); nominal maximum 84.

Complexity profile

Each segment is one criterion's contribution to the LLM total. Hover or focus a segment for its score and rationale.

Under-specified at assessment cutoff: No

The EIP text available at the assessment cutoff left material behavior unresolved. The affected criteria and the plausible total range record that uncertainty.

The assessor found no material behavior left unresolved by the EIP text at the cutoff.

Notable ambiguities noted by the assessor (1)

The proposal cites EIP-2733 as motivation rather than as a dependency; this assessment records the explicit relationship as a limited, non-critical cross-EIP interaction.

Criterion breakdown

EIP-3855 Shanghai / Shapella: LLM criterion scores and rationale
Criterion	Score	Why this score	Evidence / uncertainty
Added opcodes	1	This exactly matches one new simple opcode with no data portion, simple stack mechanics, and constant gas.	eip.md · Specification, lines 34-36 One opcode at 0x5f is added; it has no immediate data, pops nothing, pushes one constant value, and has constant gas cost. Confidence: High
EVM Gas rule changes	1	The gas schedule gains one opcode entry, but it reuses the existing constant-cost verylow mechanism; this is an update to existing gas accounting rather than a new mechanism.	eip.md · Specification and Rationale/Gas cost, lines 34-42 PUSH0 is assigned a constant cost of 2 gas, explicitly identified with the existing verylow cost class. Confidence: High
Patterns affecting pre-existing tests	1	A minor, localized subset of pre-existing invalid-opcode or bytecode-execution cases involving 0x5f must be updated across the activation boundary.	eip.md · Backwards Compatibility and Test Cases, lines 48-56 Byte 0x5f becomes an executable opcode, changing behavior for existing code containing it; the proposal supplies success and stack-overflow cases for the new behavior. Confidence: Medium Uncertainty: The package does not enumerate the pre-existing test corpus, so the affected subset is inferred from the specified change in 0x5f behavior.
Security risks	1	The consensus behavior change has a limited implementation and compatibility risk, but it is self-contained, isolatable, and does not introduce complex security interactions.	eip.md · Backwards Compatibility and Security Considerations, lines 48-60 Existing code containing 0x5f can change behavior, but the opcode is self-contained and its lack of immediate bytes leaves jump-destination analysis unaffected. Confidence: Medium Uncertainty: The document reports no known security impact; the nonzero score reflects the explicit deployed-code behavior change if the opcode is implemented or activated incorrectly.
Edge/boundary conditions	1	The new opcode exposes one clear boundary-prone mechanism at the EVM stack-depth limit.	eip.md · Test Cases, lines 52-56 The test cases explicitly distinguish 1024 successful pushes from a 1025th push that aborts for stack overflow. Confidence: High
Cross-EIP interactions	1	The relationship to EIP-2733 is explicit but limited and non-critical; PUSH0 can be specified and tested independently.	eip.md · Motivation, lines 25-32 PUSH0 is intended to reduce reliance on context-sensitive zero-producing opcodes, and the proposal identifies EIP-2733's possible RETURNDATASIZE behavior change as an example. Confidence: Medium Uncertainty: EIP-2733 is cited as motivation rather than as a dependency, so the interaction does not warrant coordinated-mechanism complexity above score 1. Interacting EIPs: EIP-2733

Show 22 zero-score criteria

Zero-score criteria (Checklist revision 2)
Criterion	Why this score	Evidence / uncertainty
Modified opcodes	No pre-existing opcode's behavior is modified or deprecated.	eip.md · Backwards Compatibility, lines 48-50 The document characterizes 0x5f as a new opcode that did not previously exist, rather than a modification of an existing opcode.
Added precompiles	No precompile is introduced.	eip.md · Abstract and Specification, lines 13-15 and 34-36 The proposal adds an EVM instruction at an opcode byte and does not define a precompile.
Modified precompiles	No existing precompile is modified.	eip.md · Specification, lines 34-36 The specified opcode has no connection to precompile logic or precompile gas accounting.
Added system contracts	No system contract is added.	eip.md · Abstract and Specification, lines 13-15 and 34-36 The proposal introduces an instruction, not a contract or reserved-address mechanism.
Modified system contracts	No pre-existing system contract is directly or indirectly modified by the specified mechanism.	eip.md · Specification, lines 34-36 PUSH0's specified behavior is confined to a stack operation and does not identify or alter any system contract.
State-access ordering within opcode execution	PUSH0 neither accesses state nor changes gas charging relative to a state access, so no opcode state-access ordering changes.	eip.md · Specification, lines 34-36 The new instruction only performs a stack push and specifies no state access.
Blob gas accounting changes	No blob gas accounting is introduced or modified.	eip.md · Specification, lines 34-36 The proposal specifies only an EVM opcode's execution-gas cost and contains no blob-gas mechanism.
State gas accounting changes	The proposal has no state-gas cost, charging site, budget, reservoir, or spill-path change.	eip.md · Specification, lines 34-36 PUSH0 changes only the EVM stack and has no state write or state-gas charge.
New EVM gas refund	No new gas-refund mechanism is introduced.	eip.md · Specification, lines 34-36 The instruction has a fixed 2-gas charge and the specification defines no refund behavior.
New transaction types	No new transaction type is introduced.	eip.md · Metadata and Specification, lines 7-10 and 34-36 This Core proposal defines an EVM opcode and contains no transaction envelope or transaction type.
New or modified transaction validity mechanisms	Existing transaction validity mechanisms and intrinsic gas calculation are unchanged.	eip.md · Specification, lines 34-36 The only validity-like condition is opcode availability after the fork; no transaction validity or intrinsic-gas rule is specified.
New block / header fields	No new block or block-header field is introduced.	eip.md · Specification, lines 34-36 Fork activation gates an opcode behavior and introduces no block-body or header field.
Encoding changes (RLP/SSZ)	Opcode-byte assignment is outside this anchor's transaction, block, and interface encoding scope.	eip.md · Specification, lines 34-36 The proposal assigns an EVM bytecode opcode but makes no transaction, block, RLP, SSZ, or interface encoding change.
Block syncing changes	No block RLP validation mechanism requiring syncing tests is introduced.	eip.md · Specification, lines 34-36 The proposal changes EVM instruction execution only and specifies no block RLP field or validation rule.
New fork activation mechanism	Standard fork gating of a new opcode is not a new activation mechanism and requires no activation-block state or internal-variable modification.	eip.md · Specification, lines 34-36 PUSH0 becomes available at the ordinary HF boundary, with no state transition or existing internal-variable modification specified at activation.
Engine API changes	No Engine API change is required.	eip.md · Specification, lines 34-36 The complete specified change is an EVM opcode and includes no Engine API field, endpoint, or communication mechanism.
Transition-tool interface changes	The change requires no transition-tool interface modification or new field.	eip.md · Specification, lines 34-36 Activation and behavior are expressed entirely as an opcode rule, with no new transition-tool input or output field.
New invariant on pre-existing tests	Pre-existing tests unrelated to PUSH0 gain no new invariant to assert.	eip.md · Specification and Test Cases, lines 34-36 and 52-56 The specified outputs and stack-limit checks apply to tests of PUSH0 itself, not as an additional assertion on unrelated tests.
New test-framework primitives	Existing execution, stack, and exceptional-halt test primitives suffice; no new framework abstraction is required.	eip.md · Test Cases, lines 52-56 The proposed cases are ordinary raw-bytecode execution and stack-result or abort checks.
Performance risks	The proposal introduces no mechanism whose performance needs validation beyond the isolated constant-time opcode behavior.	eip.md · Specification and Rationale, lines 34-46 PUSH0 is a constant stack operation with no immediate data and may share the contiguous PUSH implementation.
Cryptography	No cryptographic mechanism is introduced or modified.	eip.md · Specification, lines 34-36 PUSH0 places a fixed zero value on the stack and performs no cryptographic operation.
Unspecified behavior requiring cross-client consensus	The historical text determines the constructible PUSH0 behaviors using ordinary EVM execution rules; no localized detail requires new cross-client agreement.	eip.md · Specification, Test Cases, and Security Considerations, lines 34-36, 52-60 The opcode byte, activation condition, immediate-data length, stack inputs and output, gas cost, overflow outcome, and jump-destination treatment are specified.

Assessment provenance

Assessed EIP revision: ethereum/EIPs@6caab461df EIPS/eip-3855.md committed 2021-09-22 · information cutoff 2022-02-04
Current master · File history · blob e86efc6e13 · sha256 f89cc30713d2
Rubric: Checklist revision 2 · ethspecs/pm@3d8c0128c5
Evaluator: gpt-5.6-sol at xhigh reasoning effort · isolation bubblewrap_one_eip_capsule_v1
Source record: Frozen research record research/tasks/05-retrospective-complexity-assignment/outputs/fork-eips/shanghai/eip-3855.yaml · sha256 8ff8b9cbf299

Compare EIP-3855 with other assessments All Shanghai / Shapella assessments

Criterion legend and glossary

Every stacked bar, comparison matrix, and criterion table on this site uses the same criterion colours, abbreviations, and order. Colour marks the criterion group; the abbreviation and name identify the criterion. Scores are 0–3 per criterion (4 is exceptional; cross-EIP interactions is uncapped).

EVM surface

Opcodes, precompiles, and system contracts that are added or modified.

OP+
Added opcodes
Introduces new opcodes
Score anchors
0
No new opcodes are introduced.
1
A new simple opcode is introduced (no data portion, no complex stack mechanics, and a constant gas cost).
2
Multiple new simple opcodes are introduced, or a single new complex opcode is introduced (has data portion, or complex stack mechanics, or a dynamic gas cost).
3
Multiple new opcodes are introduced, and at least one of them is complex (has data portion, or complex stack mechanics, or a dynamic gas cost).
- Cryptography opcodes are not considered complex by default. Refer to the "Cryptography" section for a separate assessment.
Modified opcodes
Modifies pre-existing opcodes
Score anchors
0
No pre-existing opcode modifications are introduced.
3
At least one pre-existing opcode's behavior is modified (not including gas changes) or a pre-existing opcode is deprecated.
PC+
Added precompiles
Introduces new precompiles
Score anchors
0
No new precompiles are introduced.
1
A new simple precompile is introduced (constant input length, constant gas cost).
2
Multiple new simple precompiles are introduced, or a single new complex precompile is introduced (dynamic input length or dynamic gas cost).
3
Multiple new precompiles are introduced, and at least one of them is complex (dynamic input length or dynamic gas cost).
- Cryptography precompiles are not considered complex by default. Refer to the "Cryptography" for a separate assessment.
Modified precompiles
Modifies pre-existing precompiles logic or gas-accounting
Score anchors
0
No pre-existing precompiles are modified.
1
At least one pre-existing precompile has its gas schedule modified.
2
Multiple pre-existing precompiles have their gas schedule modified, or a single pre-existing precompile has its behavior modified.
3
The behavior of multiple pre-existing precompiles, or a single complex pre-existing precompile modified.
Added system contracts
Introduces new system contract, stateful or not
Score anchors
0
No new system contracts are introduced.
1
A new system contract is introduced that is not stateful nor does it trigger a new system action (e.g. requests to the consensus layer).
2
Multiple new system contracts are introduced or a single new system contract that is either stateful or triggers a new system action (e.g. requests to the consensus layer).
3
Multiple new system contracts are introduced and at least one of them is either stateful or triggers a new system action (e.g. requests to the consensus layer).
Modified system contracts
Modifies pre-existing system contracts
Score anchors
0
No modifications to pre-existing system contracts are introduced, directly or indirectly.
1
Does not directly modify any system contract, but its behavior has minor indirect effects on one or more system contracts.
2
Does not directly modify any system contract, but its behavior has major indirect effects on one or more system contracts.
3
At least one pre-existing system contract code or state is modified, which would involve irregular state transition or a similarly complex transition methodology.

Gas and accounting

Execution, blob, and state gas rules, refunds, and where charges happen inside opcodes.

EVM Gas rule changes
New EVM gas accounting rules
Score anchors
0
No gas accounting changes.
1
Existing gas accounting mechanism is updated.
2
A new gas accounting mechanism is introduced but it does not affect existing mechanisms nor does it affect existing tests.
3
A new gas accounting mechanism is introduced and affects existing mechanisms which in turn affect existing tests.
ORD
State-access ordering within opcode execution · Checklist revision 2 only
Changes *where inside an opcode's execution* state is accessed, or where gas is charged relative to that access. Because a state access is recorded in the block-level access list only if execution had enough gas to reach it, this ordering is consensus-critical: moving it changes the BAL at every gas boundary of every affected opcode.
Score anchors
0
No change to where state is accessed, or to where gas is charged relative to a state access, within any opcode.
1
A single opcode's state-access or gas-charge ordering changes.
2
Multiple opcodes' ordering changes, or a new state-accessing operation is introduced whose position in the order must be settled.
3
The ordering rule changes for a whole class of state-accessing opcodes at once, or what counts as a recordable state access is redefined — requiring existing BAL vectors to be re-derived across opcodes and forks.
- Distinct from "Modified opcodes", which asks whether an opcode's **result** changed. This row asks about the **path to the result**, which is observable even when the result is identical. An EIP can be 0 on that row and 3 on this one.
- Score changes **to** the ordering. Do not score the fact that state accesses are observable — they always are.
- Each boundary must be re-tested against every other dimension that can change the answer (cold/warm, static/non-static, delegated/direct, revert/success), so the case count grows multiplicatively rather than additively. Note this explicitly under Special Considerations.
Blob gas accounting changes
New Blob gas accounting rules which potentially affect pre-existing tests
Score anchors
0
No blob gas accounting changes.
1
Existing blob gas accounting mechanism is updated.
2
A new blob gas accounting mechanism is introduced but it does not affect existing mechanisms nor does it affect existing tests.
3
A new blob gas accounting mechanism is introduced and affects existing mechanisms which in turn affect existing tests.
SGAS
State gas accounting changes · Checklist revision 2 only
New state gas accounting rules. State gas is the cost of *writing* state, as opposed to accessing or executing it: `StateGasCosts`, `COST_PER_STATE_BYTE`, the block-level state gas budget, and the spill path into execution gas.
Score anchors
0
No state gas accounting changes.
1
An existing state gas cost or `STATE_BYTES_PER_*` rate is adjusted.
2
A new state-gas-charging site is introduced, or the block-level state gas budget or reservoir allocation is modified.
3
A new state gas charging mechanism is introduced, or the spill interaction between state gas and execution gas is modified, affecting existing gas tests.
- Harder to test than blob gas: the spill path means state gas cannot be metered independently of execution gas, and some costs (e.g. `NEW_ACCOUNT`) are state-dependent.
New EVM gas refund
New gas-refund mechanism
Score anchors
0
No new gas-refund mechanisms are introduced.
1
A new simple gas-refund mechanism is introduced that does not affect either existing tests or existing gas-refund mechanisms.
2
A new complex gas-refund mechanism is introduced or a simple mechanism that affects existing tests or existing gas-refund mechanisms.
3
A new complex gas-refund mechanism is introduced that affects existing tests or existing gas-refund mechanisms.

Blocks, transactions, and encoding

Transaction types and validity, block and header fields, encodings, syncing, and activation-time changes.

New transaction types
Introduces a new transaction type
Score anchors
0
No new transaction types are introduced.
3
A new transaction type is introduced.
New or modified transaction validity mechanisms
Creates new or modifies pre-existing transaction types' validation mechanisms
Score anchors
0
No changes are introduced to the validity rules of existing transaction types or to their intrinsic gas cost calculation.
1
Minor adjustments are introduced to validity rules or intrinsic gas cost calculation, but they do not significantly affect existing tests.
2
Changes to validity rules or intrinsic gas cost calculation affect existing tests, but require only limited updates to test cases and no redesign of the testing infrastructure.
3
Changes to validity rules or intrinsic gas cost calculation require extensive rework or redesign of the tests or testing infrastructure.
New block / header fields
Introduces new block or block header fields
Score anchors
0
No new block or header fields are introduced.
3
A new block or header field is introduced.
ENC
Encoding changes (RLP/SSZ)
Introduces encoding changes at the transaction/block/interfaces level
Score anchors
0
No encoding changes are introduced at the transaction, block, or interfaces levels.
3
An encoding change is introduced at transaction, block or interfaces level (e.g. RLP -> SSZ).
- "Interfaces level" includes the Engine API. Score an Engine API encoding change (e.g. JSON -> SSZ) here.
Block syncing changes
Modifies block RLP validation mechanisms that require test client syncing.
Score anchors
0
No new RLP validation mechanism is introduced.
1
A single simple RLP validation mechanism is introduced.
2
Multiple simple RLP validation mechanisms are introduced or a single complex one.
3
Multiple RLP validation mechanisms are introduced and at least one of them is deemed complex.
ACT
New fork activation mechanism
Modifies state, internal variables, or similar, at the fork activation block
Score anchors
0
No state modifications, internal variables or similar are modified at the fork activation block.
3
Either a state modification or internal variables are modified at the fork activation block.
- Initialization of new internal variable is not considered a modification.

Client interfaces

Engine API and transition-tool interface changes.

Engine API changes
Introduces new fields to the Engine API directives
Score anchors
0
No new fields or communication mechanisms are introduced to the Engine API.
1
A single new field is introduced in one of the Engine API endpoints.
2
Multiple fields are introduced to one or multiple Engine API end points, or a new Engine API end-point is introduced.
3
Multiple fields are introduced to one or multiple Engine API end points and a new Engine API end-point is introduced.
Engine API encoding changes · Checklist revision 1 only
Engine API encoding changes (the revision-1 template defines no anchor text for this row).
T8N
Transition-tool interface changes
Modifies or adds new fields to the transition tool interface.
Score anchors
0
No modifications to the transition tool interface are required.
1
A single new field needs to be introduced to the transition tool interface.
2
Multiple new fields or a new mechanism has to be introduced to the transition tool interface.
3
Multiple new fields and a new mechanism has to be introduced to the transition tool interface.
- Special consideration must be paid to this section if the EIP introduces a mechanism that requires the state transition tool to be aware whether the block it is processing is the fork-activation block.

Testing impact

Rework, new invariants, and new primitives required in the test framework.

Patterns affecting pre-existing tests
Implements a new validation mechanism or rule that translates in reworking pre-existing tests
Score anchors
0
No pre-existing tests are affected by this change.
1
Minor subset of existing tests are affected by this change.
2
Considerable subset of existing tests are affected by this change but involves only a contrived category of tests.
3
Major subset of existing tests are affected, including diverse category of tests (benchmarks, static, multiple forks, etc.).
INV
New invariant on pre-existing tests · Checklist revision 2 only
Tests that are **not about this EIP** must nonetheless assert something this EIP produces. Their logic does not change; they gain a new thing to check.
Score anchors
0
Pre-existing tests assert nothing new.
1
A narrow, contrived category of pre-existing tests gains a new assertion.
2
A broad category gains a new assertion, applied mechanically.
3
Every test in the fork gains the assertion regardless of what it tests, and pre-fork vectors must be re-derived to satisfy it.
- Paired with the row above, and easy to confuse with it. "Patterns affecting pre-existing tests" asks whether existing tests must be **reworked**; this row asks whether they must **additionally assert something new**. Score both — an EIP can be low on one and high on the other.
New test-framework primitives · Checklist revision 2 only
Requires new abstractions in the test framework itself — expectation types, modifiers, helpers — beyond writing test functions with what already exists.
Score anchors
0
Existing test primitives suffice.
1
Existing primitives need minor extension.
2
New expectation or modifier primitives are required, reusable within this EIP's own test suite.
3
New framework-level primitives are required that become a permanent part of the framework and are used by other EIPs' tests.

Risk and validation

Security, performance, boundary conditions, and cryptography that need validation.

Security risks
Introduces or modifies mechanisms that could compromise the security of the chain, users, validators, or other stakeholders, if not implemented properly.
Score anchors
0
No new mechanisms are introduced that could pose a security risk.
1
The introduced mechanisms are self-contained, can be validated in isolation, and do not alter existing invariants that could pose a security risk for any stakeholders.
2
The introduced mechanisms interact with a limited number of existing components, slightly altering their security assumptions and requiring a targeted security review or fuzzing.
3
The introduced mechanisms interact with multiple existing components, including critical ones, substantially altering their security assumptions and requiring an extensive security review and fuzzing.
Performance risks
Introduces or modifies mechanisms and requires performance validation.
Score anchors
0
No new mechanisms are introduced that require performance validation.
1
The introduced mechanisms can be benchmarked in isolation and do not affect existing performance behavior.
2
The introduced mechanisms cannot be fully benchmarked in isolation, but they only have a limited impact on the existing performance benchmarks.
3
The introduced mechanisms cannot be benchmarked in isolation and have a substantial impact on existing performance benchmarks or have complex interactions with existing mechanisms.
Edge/boundary conditions
Feature contains edge/boundary conditions.
Score anchors
0
No discernible edge cases or boundary conditions are introduced.
1
A single edge-case or boundary-condition prone mechanism is introduced.
2
Multiple edge-case or boundary-condition prone mechanisms are introduced, but none of them requires an elevated number of cases to test.
3
Multiple edge-case or boundary-condition prone mechanisms are introduced and at least one of them requires an elevated number of cases to test.
Cryptography
Introduces new cryptography mechanisms or modifies existing functionality that involves cryptography
Score anchors
0
No cryptography mechanisms are introduced.
1
A new cryptography mechanism is introduced but it is a well known mechanism that is known to have vast resources to aid on its testing.
2
Multiple new cryptography mechanisms are introduced that are well-known or a single but novel mechanism is introduced that is either untested or has limited resources.
3
Multiple new cryptography mechanisms are introduced and at least one of them is a novel mechanism.

Coordination

Cross-EIP interactions and behavior that clients must agree on before tests exist.

XEIP
Cross-EIP interactions
Introduces or modifies mechanisms that affect other EIPs in either the same or past forks.
Score anchors
0
Fully self-contained EIP that does not depend on, modify, or conflict with any other EIP.
1
The EIP interacts with one or more other EIPs in a non-critical and limited way but can be tested independently for the most part.
2
The EIP depends on or modifies one or more other EIPs such that coordinated testing and consideration is required, but interactions are limited in scope and not complex.
3
The EIP has strong interdependencies with multiple EIPs, requiring extensive coordinated cross-EIP testing as well as potential re-design of existing test vectors.
- +1 for every 3 additional interacting EIPs beyond the first 3, each of which requires its own coordinated test cases. List the EIPs in the rationale.
- This row is intentionally uncapped, unlike every other anchor: each interacting EIP is another axis of the test matrix, so a ceiling would make a 12-EIP product indistinguishable from a 3-EIP one.
UNSP
Unspecified behavior requiring cross-client consensus · Checklist revision 2 only
The EIP text does not determine the answer for cases a test can construct. Clients must agree on a previously unspecified detail before tests can be baselined. The cost here is coordination and re-baselining, not test writing.
Score anchors
0
The EIP text determines the answer for every case a test could construct.
1
A few details are unspecified but have an obvious intended reading.
2
Details require client agreement before tests can be written, but they are localized.
3
A previously unspecified *and previously unobservable* behavior becomes consensus-critical; expect tests to be re-baselined on each round of EIP amendment.
- Score this from the EIP's state at assessment time: whether it has client implementations, whether it has been through a devnet, and how many open questions remain on its discussion thread.