[vansh (vansh-nagar)]

Pull Request

📖 Description

Parsing a URL such as /search?filter[category]=hardware throws TypeError: currentParams.get is not a function, interrupting route recognition. Use object/array indexing for nested parameters so bracketed objects, indexed arrays, and append-style arrays parse successfully, including output from QueryString.build().

Traversal uses own properties and ignores __proto__ paths so restoring nested parsing does not follow inherited containers. The router's Node test command now includes the new query-string suite.

🎫 Issues

Fixes #7741

👩‍💻 Reviewer Notes

Implementation and tests were developed with Codex. This preserves the existing public TypeScript signatures. The string-only typing of structured query values is outside this fix.

📑 Test Plan

• Before the fix: 11 of the initial 12 query tests fail with currentParams.get is not a function; the flat-query control passes.
• After the fix: all 13 query tests pass, including round trips, inherited-property handling, and recognition of a route with nested query parameters.
• npm run test -w @microsoft/fast-router: 10,930 tests pass; lint and API report checks pass.
• npm test: all 13 runnable monorepo tasks pass (one task skipped); source and declarative browser suites complete without failures across Chromium, Firefox, and WebKit.
• npm run test:validation and npm run biome:ci pass.
• npm run build: all nine monorepo builds pass (macOS arm64, Node 26.0.0).
• Biome checks on the changed TypeScript files, npm run format:check, and npm run checkchange pass.

✅ Checklist

General

• I have included a change request file using $ npm run change
• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Agents

• I have linked to an existing issue in this project that this change addresses
• I have read the skills

The router package has no DESIGN.md.

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