ENG-9892: feat(plugins): add register_route hook and get_plugin lookup

[FarhanAliRaza]

Plugins that contribute pages (e.g. auth) previously needed global state and circular-import workarounds to find their configured instance and inject routes. Instead:

• Plugin.register_route(app) runs once per app at the start of compile_app, letting plugins add pages before routes are resolved.
• get_plugin(cls) resolves the configured plugin instance from the rxconfig plugins list, raising ConfigError on ambiguous matches.
• add_page invalidates the cached router so late-added routes resolve.

All Submissions:

• Have you followed the guidelines stated in CONTRIBUTING.md file?
• Have you checked to ensure there aren't any other open Pull Requests for the desired changed?

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

New Feature Submission:

• Does your submission pass the tests?
• Have you linted your code locally prior to submission?

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

[greptile-apps]

Greptile Summary

This PR adds plugin-owned route registration and lookup support. The main changes are:

• A staged Plugin.register_route hook for contributing pages before compile.
• A get_plugin() helper for resolving configured plugin instances.
• Router-cache invalidation when pages are committed through the new page path.
• Tests and docs for plugin page registration behavior.

Confidence Score: 4/5

This is close, but the router cache issue should be fixed before merging.

• Page commits now clear the cached router.
• The compile path still replaces _pages directly without clearing the cached router.
• A long-lived app can keep resolving routes from an older compile after _pages is rebuilt.

reflex/compiler/compiler.py

Important Files Changed

Filename	Overview
reflex/app.py	Adds staged page preparation, plugin route collection, and router invalidation on page commit.
reflex/compiler/compiler.py	Registers plugin routes before page evaluation, but the compile-time page reset can still leave the cached router stale.
packages/reflex-base/src/reflex_base/plugins/base.py	Adds the route-registration hook context and configured plugin lookup helper.
reflex/state.py	Adds dynamic route argument type introspection for staged plugin route validation.

_{Reviews (3): Last reviewed commit: "feat(plugins): stage register_route hook..." | Re-trigger Greptile}

[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 8 skipped benchmarks¹

---

_{Comparing FarhanAliRaza:farhan/eng-9892-auth-remove-global-state-circular-import-workarounds-in (b9ced03) with main (948c619)²}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (3b97060) during the generation of this report, so 948c619 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[FarhanAliRaza]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🎉

Reviewed commit: b9ced03cae

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