BSV Overlay Stack Merges Optional VeriFast Script Verification

Developer Tools / Data-infrastructure

In Brief

The BSV TypeScript stack has merged support for overlay operators to configure VeriFast, an existing WebAssembly verification backend, for transaction script checks.

The integration covers transaction submission and synchronization, with project benchmarks reporting substantially shorter verification times for selected workloads. The option remains off by default, and the changes have not yet appeared in published overlay packages.

News Report

Pull request #1456 merged into the BSV TypeScript Stack repository on October 30 at 19:11 UTC. It adds configuration options to @bsv/overlay and @bsv/overlay-express for supplying a script-verification backend to the engine.

Overlay services maintain application-specific transaction state and answer queries on BSV Blockchain. Their verification work includes checking input scripts for unconfirmed transactions and validating the supporting proof information.

VeriFast provides a WebAssembly version of the BSV BDK script engine. The new contribution connects that existing verifier to overlay processing paths that previously offered no direct configuration option for passing it into transaction verification.

Verification During Submission and Synchronization

The first integration point is the engine’s transaction-submission path. The second is graph-anchor validation during GASP synchronization, where the service checks the transaction graph it has received.

Both now pass the configured verifier into the SDK’s transaction-verification method. The change preserves the surrounding verification process and existing overlay admission rules.

Overlay Express adds configureScriptVerifier, alongside an equivalent engine configuration option. Operators choosing VeriFast install it separately and initialize the verifier before configuring the engine and serving traffic. The contribution does not make VeriFast a mandatory runtime dependency of Overlay Express.

Initialization matters because VeriFast’s default adaptive mode continues using the JavaScript interpreter while its WebAssembly module loads. Once ready, eligible scripts can use WebAssembly; smaller non-cryptographic scripts may continue through JavaScript. The new configuration method warns when a supplied verifier reports that it is not ready.

VeriFast’s documentation also distinguishes this routing choice from error recovery: after a check selects WebAssembly, an error does not trigger a retry through the JavaScript interpreter.

What the Reported Performance Shows

The contribution reports tests using unconfirmed transactions spending outputs with confirmation proofs, through the verification call used by the overlay engine.

For a transaction with 100 P2PKH inputs, reported verification time fell from 122.3 milliseconds with the JavaScript interpreter to 11.1 milliseconds with a preloaded VeriFast verifier. A 100-input PushDrop case fell from 122.5 milliseconds to 11.0 milliseconds.

Those results represent approximately elevenfold improvements in the measured verification cases. They use the best of five runs with the verifier already loaded. They do not measure complete server request handling, database activity, network propagation or overall overlay throughput.

The contribution also reports matching accept-or-reject results across 30 valid and deliberately damaged transaction cases. Added integration tests exercise the real VeriFast backend, checking that it is called and that a transaction with a corrupted signature is rejected by both verification paths.

The relevant hosted build, test, lint and merge checks passed. BSV TIMES reviewed the merged changes and test records; it has not independently reproduced the timings or tested a live overlay deployment.

Release Status

At the time of checking, npm still listed @bsv/overlay 2.7.0 and @bsv/overlay-express 2.8.0, both published on October 28. Inspection of those package archives found that the new configuration support was absent.

The merged changelog entries remain under Unreleased. The contribution also explicitly leaves enabling the verifier in the repository’s overlay-server deployment to separate operational work.

The current milestone is therefore availability in merged source. Package publication and operator adoption remain subsequent steps.

BSV TIMES Read

This extends earlier VeriFast work into another part of the application infrastructure. A faster verification engine becomes more useful when services can select it through a supported configuration interface.

For overlays checking many input scripts, reducing verification time could lower the processing cost of that stage. The effect on a complete service will depend on its transaction mix and other bottlenecks.

The practical next evidence will be a published package containing the integration and measurements from actual overlay workloads, alongside continued checks that the two verification paths produce consistent decisions.

Developer Context

The pull request was opened by GitHub user imranterranode, and its implementation commit credits Imran Munir.

The contribution builds on @bsv/verifast, maintained within the BSV TypeScript monorepo. BSV TIMES covered VeriFast’s broader script and wallet acceleration work in July; this change adds explicit integration with the overlay engine and its server configuration.

Source Links

Posted on October 31, 2026 (UTC)