[DZakh]

Anonymous EVM events can now be indexed. An event is anonymous when its signature ends in anonymous or its ABI entry has "anonymous": true. Such logs carry no signature topic: topic0 holds the first indexed param. So every registration of an anonymous event must filter that param by concrete values:

events:
  - event: LogNote(bytes4 indexed sig, address indexed guy, bytes32 indexed foo, bytes32 indexed bar, uint256 wad, bytes fax) anonymous

indexer.onEvent(
  { contract: "Vat", event: "LogNote", where: { params: { sig: "0x29ae8114" } } },
  async ({ event }) => { /* event.params.sig === "0x29ae8114" */ },
);

Replaces the config-only topic0: approach in #1706 (discussed there). Covers the fixed-topic0 case; the varying-topic0 case in #990 is not covered yet.

Design

Rather than special-casing anonymous events, the topic-filter pipeline is generalized. All four topic positions are now symmetric, and the event's signature is just a topic0 constraint, which an anonymous event doesn't have. The layers stay as they were:

• CLI config (Rust):
  • Event.sighash: Option<String>, which is None only for anonymous events.
  • Indexed-param limits: 1–4 for anonymous events, at most 3 otherwise. The second check was missing before.
  • Duplicate-event checks treat anonymous events correctly.
  • The internal JSON leaves out sighash when there is none.
• ReScript runtime:
  • Internal.topicConstraint (Any | Values | ContractAddresses) and topicFilter (topic0…topic3); resolvedWhere.topicFilters is a list of alternatives, any of which may match.
  • LogSelection.parseWhereOrThrow lays out the positions from the optional sighash plus the indexed params. For an anonymous event it throws at the onEvent/contractRegister call site unless every alternative gives topic0 values. The error names the event, the contract and the param.
• Rust sources (HyperSync and RPC share them):
  • One topic-filter model, evm_hypersync_source/topic_filter.rs, is used by both query building (selection.rs) and routing (decode.rs). It replaces two duplicate parsers that each special-cased topic0.
  • Routing no longer compares topic0 to the sighash separately. The decoder is built from the optional sighash.
  • compress merges only selections that constrain topic0 alone. Any other selection stays separate, so an unconstrained topic0 can't be dropped silently.
• Simulate (createTestIndexer):
  • A simulated item now reaches only the handlers whose where matches it, through the same topic encoding. Before, every handler of the event ran; this affected regular events too.
  • chain.X.addresses is checked per alternative, as real routing does. The per-registration addressFilterParamGroups and the code that existed only for it are deleted.
• TS types: for an anonymous event, where is required on onEvent and contractRegister, every filter must name the first param, and a callback may return a filter or false but not true. The generated ReScript types are unchanged.
• Docs: an "Anonymous events" section in the indexer-filters skill.

Supporting #990 later (an anonymous event with no topic0 filter) only needs the ReScript check and the Rust check relaxed; query building already handles an open topic0.

Should the source interface take generic filters? No

What exists today:

• The source contract. Source.t.getItemsOrThrow takes ~selection: FetchState.selection: the partition's registrations plus dependsOnAddresses. It also takes ~addressSet, the partition's addresses, which is already ecosystem-neutral. Sources get no separate filter argument.
• Where each ecosystem's filter lives. Each ecosystem's filter is already on its registration subtype in Internal.res:
  • EVM: evmOnEventRegistration.resolvedWhere.topicFilters (topic constraints per position, as a list of alternatives);
  • SVM: svmOnEventRegistration.accountFilters (account slots) plus isInner;
  • Fuel: no filter.
• Who reads the filters. The EVM sources (HyperSync and RPC) convert registrations to the napi input once, when the client is created (HyperSyncClient.Registration.fromOnEventRegistrations). From then on Rust owns the filter: per-partition query building (selection.rs, SelectionBuilder, also used by evm_rpc_source/mod.rs) and item routing (decode.rs). The SVM source does the same with its own Registration. Only SimulateSource reads topicFilters in ReScript.

So a generic filter in the source interface would be a union that every source unwraps to its own ecosystem's kind. Topic positions, account slots and Fuel receipt kinds share no meaning, so there's nothing common for a source to do with it. What future filter features need is the EVM topic filter itself to be general, which this PR does. For the move to Rust, the remaining ReScript part is turning a user's where into topic filters: callbacks, the chain object and the chain.X.addresses sentinel. It stays in ReScript so errors point at the onEvent call site. The next step would be a napi call made at registration time that lays out the topic positions and encodes the values (encoding already goes through the addon's encodeIndexedTopic).

Also fixed

• bytesN params decode to their declared width. Since Decode EVM, SVM and Fuel params to a JS value tape on the worker #1675 the decoder wrote the full 32-byte word, so a bytes4 read 0x29ae8114000…0. It now reads 0x29ae8114. This changes values for bytes1–bytes31 params, back to what they were before Decode EVM, SVM and Fuel params to a JS value tape on the worker #1675.
• Anonymous events without a handler under raw_events: true no longer fail at startup. Simulating one reports the usual "no handler" error.
• Two anonymous overloads with the same name now get the "use the name field" error instead of "remove the duplicate".

Tests

Each new test failed first:

• AnonymousEvent_test.res: the full indexer on Postgres over HyperSync and RPC, with config declaring the event by signature (Vat) and by ABI file (Jug). One assertion covers:
  • which handler saw which log, with every decoded param;
  • a regular event with four topics on the same contract that isn't misrouted;
  • a wildcard registration and chain.X.addresses on a later param;
  • the filters each source sent.
• AnonymousEventWhereErrors_test.res: 11 cases that must reject with the exact message, and 4 that must pass.
• SimulateWhereParams_test.res, SimulateWhereAddresses_test.res, AnonymousEventSimulate_test.res: simulate routing.
• UserApiValidation_test.res: indexed-param limits, and same-named anonymous overloads.
• EvmHandlersApi_test.res "Anonymous event types": accepted forms and 9 @ts-expect-error cases.
• Rust: compress keeps an open topic0 separate; anonymous routing and decoding; both sides reject an anonymous registration with no topic0 values.

The outside-in OnEventWhere* tests from #1762 pass unchanged, which guards the refactor.

Verification

• cargo fmt --check and cargo clippy --all-targets --all-features -D warnings are clean. cargo test --lib: 1046 passed.
• envio-tests on Postgres:
  • every changed test file, every file that uses simulate, and test/lib_tests: 96 files, 928 passed, 2 expected failures;
  • OnEventWhere*, the source contracts, EvmHandlersApi, UserApiValidation and Config: 262 passed, 3 expected failures.
• ClickHouse (ENVIO_TEST_STORAGE=clickhouse): 10 passed, 1 expected failure.
• pnpm lint is clean.
• envio codegen + tsc --noEmit pass in test_codegen, fuel_test and e2e_test.
• Five review rounds ran on the branch. The last two found no bugs, and the final one found nothing to change.

Some test files show formatting-only changes. They weren't formatted on main, and the push hook formats every file a branch touches.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WdwJuj1pgyeoPb8vfekdfy

Summary by CodeRabbit

• New Features
  • Added support for anonymous EVM events, including decoding and filtering by indexed parameters.
  • Added validation requiring anonymous-event filters to specify the first indexed parameter, with support for multiple filter alternatives.
  • Improved event simulation to apply parameter and contract-address filters.
• Bug Fixes
  • Fixed fixed-size ABI byte values to serialize using their declared length.
  • Enforced EVM indexed-topic limits and improved validation of anonymous event configurations.
• Documentation
  • Added guidance for declaring and filtering anonymous events.

[coderabbitai]

📝 Walkthrough

This change adds support for anonymous EVM events. It makes event sighashes optional, represents filters across four topic positions, and updates event registration, decoding, HyperSync routing, type checks, and simulation.

Changes: Anonymous EVM Events

Layer / File(s)	Summary
Event model and validation packages/cli/src/config_parsing/*, packages/envio/src/Config.res, packages/envio/src/EventConfigBuilder.res, packages/envio/src/Internal.res, packages/envio-tests/test/UserApiValidation_test.res	Event sighashes are optional. EVM parsing and validation account for anonymous events, including duplicate detection and indexed-parameter limits. Fuel and SVM events retain their sighashes.
Topic-filter parsing and registration contract packages/envio/src/LogSelection.res, packages/envio/src/EventConfigBuilder.res, packages/envio/src/Internal.res, packages/envio/index.d.ts, packages/cli/src/hbs_templating/codegen_templates.rs, packages/envio-tests/test/EvmHandlersApi_test.res, packages/envio-tests/test/AnonymousEventWhereErrors_test.res, packages/cli/templates/static/shared/.claude/skills/indexer-filters/SKILL.md	Filters express constraints for each of four topic positions. Anonymous-event registrations require explicit values for the first indexed parameter, and generated TypeScript types reflect that requirement.
HyperSync filtering and decoding packages/cli/src/evm_hypersync_source/*, packages/envio/src/sources/HyperSyncClient.res	The CLI parses and materializes topic filters for HyperSync. Routing no longer requires a signature in topic0, and anonymous-event decoding treats topic0 as the first indexed parameter.
Runtime matching and simulation packages/envio/src/*, packages/envio/src/sources/*, packages/envio-tests/test/AnonymousEvent*_test.res, packages/envio-tests/test/SimulateWhere*_test.res, packages/envio-tests/test/*	Runtime registration and simulation use resolved topic filters, including contract-address constraints. Tests cover anonymous-event filtering, decoding, and simulation, and update existing registration fixtures to the new filter shape.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant EventConfigBuilder
  participant LogSelection
  participant HyperSyncClient
  participant HyperSync
  participant NativeDecoder
  EventConfigBuilder->>LogSelection: Parse where filters into topicFilters
  EventConfigBuilder->>HyperSyncClient: Pass resolved registration
  HyperSyncClient->>HyperSync: Send four-position topic filters
  HyperSync-->>NativeDecoder: Return matching logs
  NativeDecoder->>NativeDecoder: Route and decode logs

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Merge Risk: 🔵 Low · up to 18559

Simulating an unmatched event with raw events enabled can fail instead of recording the raw event. This is a bounded issue, but it should be fixed or explicitly accepted before merging.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 42 functions across 10 files. (5 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: adding support for indexing anonymous EVM events through a generalized topic-filter pipeline.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 57.14% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 42 functions across 10 files. (5 skipped: 5 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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Actionable comments posted: 1

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Inline comments:
Review comments at @packages/envio/src/HandlerRegister.res:
- Around line 485-488: Update getSimulateOnEventRegistrations to use the
registrations returned by finishRegistration rather than only the active raw
registrations, so unmatched non-anonymous events with raw_events enabled still
receive a simulation registration and can be written as raw events.

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• packages/cli/src/hbs_templating/codegen_templates.rs
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• packages/envio/src/EventConfigBuilder.res
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