perf(router-core): derive match frame depth

[Sheraff]

Summary

• remove the derived depth field from private route-match stack frames
• derive optional-skip and specificity depth from the canonical trie node
• add an equal-specificity pathless regression test and focused uncached matcher benchmark
• record before/after bundle and runtime results

Why

Every match frame already carries a trie node whose immutable depth is the source used by branch construction. Copying that same fact onto every speculative frame adds a non-mangleable object key, a property store, and a larger frame shape.

This applies the “one fact, one representation” principle without changing a public API or restructuring the matcher.

Measurements

react-router.minimal:

Metric	Before	After	Delta
gzip	89,200	89,164	-36
initial gzip	89,058	89,023	-35
raw	275,591	275,481	-110
brotli	77,742	77,653	-89

The full 17-scenario matrix improved gzip by 29–54 bytes in every scenario, initial gzip in every scenario, and raw output by 90–110 bytes. Brotli varied from -115 to +127 bytes across differently chunked apps; gzip is the benchmark’s primary metric and raw output decreased everywhere.

Focused findSingleMatch means also improved directionally:

• deep static: 0.0348 ms → 0.0347 ms
• all optionals present: 1.2670 ms → 1.2458 ms
• all optionals skipped: 0.0909 ms → 0.0894 ms
• mixed optionals: 0.9191 ms → 0.8908 ms

All benchmark RMEs were below 1%; the mixed-optional result is the clearest signal.

Checks

• @tanstack/router-core:test:unit: 105 files passed; 1,524 passed, 3 expected failures
• @tanstack/router-core:test:types: TypeScript 5.6, 5.7, 5.8, 5.9, 6.0, and 7.0 passed
• @tanstack/router-core:test:eslint: 0 errors (26 existing warnings)
• React Router nested-pathless-layout e2e: 3 passed
• full bundle-size benchmark
• five independent invariant/test/performance reviews

Summary by CodeRabbit

• Bug Fixes

  • Improved route matching specificity for pathless layout routes.
  • Fixed cases where equally specific routes could select the incorrect match.
  • Preserved correct parameter parsing for pathless routes.

• Tests

  • Added regression coverage for pathless and direct route matching.
  • Added performance benchmarks for static and optional route patterns.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: a22596f3-feac-49cf-b424-1834abe5b8f1

📥 Commits

Reviewing files that changed from the base of the PR and between 697ebb6 and 4f280b7.

📒 Files selected for processing (3)

• packages/router-core/src/new-process-route-tree.ts
• packages/router-core/tests/new-process-route-tree.test.ts
• packages/router-core/tests/route-tree-matching.bench.ts

---

📝 Walkthrough

Walkthrough

The route matcher removes computed depth from match frames and uses trie-node depth for specificity and optional-segment masks. Tests cover pathless-route selection, and a benchmark covers static and optional matching.

Changes

Route matching

Layer / File(s)	Summary
Intrinsic trie-depth matching packages/router-core/src/new-process-route-tree.ts	Match frames no longer store computed depth. Optional and pathless candidates use intrinsic trie depth, and specificity compares node depths.
Matching validation packages/router-core/tests/new-process-route-tree.test.ts, packages/router-core/tests/route-tree-matching.bench.ts	A regression test verifies pathless-route selection. A benchmark covers static and optional route matching cases.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: deriving match frame depth in router-core.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/bundle-size-principles

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View your CI Pipeline Execution ↗ for commit 67f46f9

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---

☁️ Nx Cloud last updated this comment at 2026-08-06 10:38:07 UTC

[github-actions]

🚀 Changeset Version Preview

5 package(s) bumped directly, 18 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/react-router	1.170.20 → 1.170.21	Changeset
@tanstack/router-core	1.171.17 → 1.171.18	Changeset
@tanstack/solid-router	1.170.20 → 1.170.21	Changeset
@tanstack/start-server-core	1.169.20 → 1.169.21	Changeset
@tanstack/vue-router	1.170.19 → 1.170.20	Changeset
@tanstack/react-start	1.168.37 → 1.168.38	Dependent
@tanstack/react-start-client	1.168.18 → 1.168.19	Dependent
@tanstack/react-start-rsc	0.1.36 → 0.1.37	Dependent
@tanstack/react-start-server	1.167.25 → 1.167.26	Dependent
@tanstack/router-cli	1.167.23 → 1.167.24	Dependent
@tanstack/router-generator	1.167.23 → 1.167.24	Dependent
@tanstack/router-plugin	1.168.25 → 1.168.26	Dependent
@tanstack/router-vite-plugin	1.167.25 → 1.167.26	Dependent
@tanstack/solid-start	1.168.36 → 1.168.37	Dependent
@tanstack/solid-start-client	1.168.18 → 1.168.19	Dependent
@tanstack/solid-start-server	1.167.25 → 1.167.26	Dependent
@tanstack/start-client-core	1.170.16 → 1.170.17	Dependent
@tanstack/start-plugin-core	1.171.28 → 1.171.29	Dependent
@tanstack/start-static-server-functions	1.167.21 → 1.167.22	Dependent
@tanstack/start-storage-context	1.167.19 → 1.167.20	Dependent
@tanstack/vue-start	1.168.35 → 1.168.36	Dependent
@tanstack/vue-start-client	1.167.21 → 1.167.22	Dependent
@tanstack/vue-start-server	1.167.25 → 1.167.26	Dependent

[github-actions]

Bundle Size Benchmarks

• Commit: a481655f2167
• Measured at: 2026-08-06T10:29:20.683Z
• Baseline source: history:697ebb6ddbd4
• Dashboard: bundle-size history

The following scenarios have bundle-size changes compared with the baseline:

Scenario	Current (gzip)	Delta vs baseline	Initial gzip	Raw	Brotli	Trend
react-router.minimal	87.07 KiB	-36 B (-0.04%)	86.94 KiB	269.02 KiB	75.83 KiB	████▂▂▂▂▂▁▂▁
react-router.full	90.86 KiB	-36 B (-0.04%)	90.73 KiB	280.98 KiB	79.14 KiB	████▃▃▃▃▃▂▂▁
solid-router.minimal	34.77 KiB	-29 B (-0.08%)	34.64 KiB	99.88 KiB	31.35 KiB	████▂▂▂▂▂▁▁▁
solid-router.full	39.86 KiB	-36 B (-0.09%)	39.74 KiB	115.05 KiB	35.87 KiB	████▂▂▂▂▂▁▁▁
vue-router.minimal	52.07 KiB	-30 B (-0.06%)	51.93 KiB	143.03 KiB	46.89 KiB	████▂▂▂▂▂▁▁▁
vue-router.full	58.02 KiB	-34 B (-0.06%)	57.89 KiB	161.70 KiB	52.08 KiB	████▂▂▂▂▂▁▁▁
react-start.minimal	100.56 KiB	-35 B (-0.03%)	100.43 KiB	312.19 KiB	87.26 KiB	███████▁▁▁▁▁
react-start.deferred-hydration	101.31 KiB	-32 B (-0.03%)	100.45 KiB	313.56 KiB	87.95 KiB	███████▁▁▁▁▁
react-start.full	103.87 KiB	-54 B (-0.05%)	103.73 KiB	322.14 KiB	90.21 KiB	███████▁▁▁▁▁
react-start.rsbuild.minimal	100.19 KiB	-48 B (-0.05%)	100.02 KiB	316.70 KiB	86.35 KiB	▁▁▁▁▂▂▂████▇
react-start.rsbuild.minimal-iife	100.60 KiB	-49 B (-0.05%)	100.43 KiB	317.63 KiB	86.72 KiB	▁▁▁▁▂▂▂████▇
react-start.rsbuild.full	103.52 KiB	-54 B (-0.05%)	103.34 KiB	326.79 KiB	89.13 KiB	▁▁▁▁▃▃▃████▇
solid-start.minimal	48.15 KiB	-32 B (-0.06%)	48.02 KiB	142.02 KiB	42.87 KiB	███████▁▁▁▁▁
solid-start.deferred-hydration	51.41 KiB	-30 B (-0.06%)	48.08 KiB	150.06 KiB	45.78 KiB	███████▁▁▁▁▁
solid-start.full	53.40 KiB	-38 B (-0.07%)	53.27 KiB	157.75 KiB	47.41 KiB	████▆▆▆▁▁▁▁▁
vue-start.minimal	68.93 KiB	-45 B (-0.06%)	68.80 KiB	195.03 KiB	61.33 KiB	████▆▆▆▁▁▁▁▁
vue-start.full	72.90 KiB	-36 B (-0.05%)	72.77 KiB	207.53 KiB	64.79 KiB	████▆▆▆▁▁▁▁▁

Current gzip tracks all emitted client JS chunks. Initial gzip tracks only the entry/import graph. Trend sparkline is historical current gzip ending with this PR measurement; lower is better.

[pkg-pr-new]

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commit: 67f46f9

[codspeed-hq]

Merging this PR will regress 4 benchmarks

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 9 improved benchmarks
❌ 4 regressed benchmarks
✅ 167 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Memory	mem server request-churn (react)	491.6 KB	531.9 KB	-7.57%
❌	Simulation	ssr server-fn during document ssr (react)	62.9 ms	66.3 ms	-5.22%
❌	Memory	mem client navigation-churn (solid)	580.3 KB	606.2 KB	-4.28%
❌	Simulation	ssr dehydrate rich types (vue)	135.2 ms	139.6 ms	-3.2%
⚡	Memory	mem server server-fn-churn (vue)	4,147.3 KB	270.5 KB	×15
⚡	Memory	mem server error-paths unmatched (vue)	2,142.1 KB	478.7 KB	×4.5
⚡	Memory	mem server peak-large-page (react)	1,737.5 KB	953.5 KB	+82.23%
⚡	Memory	mem server error-paths redirect (solid)	388 KB	278.4 KB	+39.35%
⚡	Memory	mem server error-paths redirect (vue)	338.6 KB	313.9 KB	+7.88%
⚡	Memory	mem server error-paths unmatched (react)	317.5 KB	299.3 KB	+6.08%
⚡	Memory	mem client navigation-churn (vue)	1.3 MB	1.2 MB	+4.45%
⚡	Simulation	ssr control-flow unmatched 404 (react)	58.1 ms	56 ms	+3.69%
⚡	Memory	mem server error-paths not-found (react)	277.7 KB	268.6 KB	+3.36%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing codex/bundle-size-principles (67f46f9) with main (697ebb6)}