question: file:// URLs are only half-supported by open/load — support or document as unsupported

[platonai]

Summary

file:///abs/path.html URLs are only half-supported by PulsarSession.open/load: they pass normalize, but they are not treated as local files by the driver, and support is effectively accidental.

Current behavior (verified)

• normalize("file:///...") succeeds: AbstractPulsarContext.normalize passes strings containing :// through, and URLUtils.normalize (URIBuilder -> URI.toURL) can produce a file: URL.
• URLUtils.isStandard("file:///...") is false because getURLOrNull2 uses OkHttp HttpUrl.parse, which only accepts http/https. Consequences:
  • CombinedUrlNormalizer drops the href for file URLs (href is only kept when isStandard).
  • Various standard-URL filters / isAllowed treat file URLs as non-standard.
• The driver's local-file branch (PulsarWebDriver.navigateInvaded -> openLocalFile) only triggers for http://localfile.internal (URLUtils.isLocalFile is a prefix check against that host), so file:// is handed straight to PageHandler.navigate(file://...):
  • no DOM-integrity / timeout bypass that BrowserEmulatorImplBase applies to local files;
  • works for simple HTML only "by accident".
• Note: ActionValidator.validateNavigate currently allows only http/https schemes and would block file:// if wired into the MCP dispatch (it has no callers in the current code path).

Question / proposed scope

Decide whether file:// should be officially supported:

• If yes: make the driver's local-file detection also recognize the file:// scheme (or convert file:// to the pseudo-URL at normalize time), apply the same DOM-integrity bypass, and add unit + e2e tests.
• If no: document file:// as unsupported and fail early at normalize with a clear error instead of half-working, and make the MCP layer's validation consistent with that decision.

References

• AbstractPulsarContext.normalize: browser4-core/browser4-skeleton/src/main/kotlin/ai/platon/pulsar/skeleton/context/support/AbstractPulsarContext.kt
• URLUtils.isStandard/getURLOrNull2: pulsar-common dependency
• Driver local-file branch: pulsar-browser dependency (PulsarWebDriver.navigateInvaded -> openLocalFile)
• BrowserEmulatorImplBase local-file handling: browser4-core/browser4-protocol/src/main/kotlin/ai/platon/pulsar/protocol/browser/emulator/impl/BrowserEmulatorImplBase.kt
• ActionValidator: browser4-agentic/src/main/kotlin/ai/platon/pulsar/agentic/tools/util/ActionValidator.kt