Always execute beforeLoad for client lanes

[Sheraff]

What changed

• run beforeLoad independently for every client navigation and preload lane, including identical and same-location requests
• keep loader reuse separate, allowing completed and in-flight loader generations to remain shareable by match ID
• remove whole-preload-lane adoption and same-location transaction deduplication
• narrow loader-flight reservation to navigation handoff and active beforeLoad planning
• make invalidation and filtered clearCache preserve correct loader ownership
• remove the urgent mode from StartTransitionFn
• update the orchestration documentation and add public-API regressions for supersession, invalidation, cache clearing, and signal lifetime

Why

beforeLoad carries lane-specific guard and context semantics, so adopting it from cache or another in-flight lane can expose stale context and control flow. Loader data is the intended reusable boundary. Separating these rules simplifies the match-loading architecture while retaining loader deduplication.

The previous broad reservation and lane-adoption mechanisms also made it possible to leak zero-owner loader flights, replay stale work after invalidation, or make retained shared work undiscoverable during filtered cache clearing.

Impact

Every client lane now evaluates its own beforeLoad. Loader work can still be reused from cache or an in-flight generation, even when lane arguments such as preload or context differ. The resulting orchestration has fewer semantic authorities and removes per-preload full-flight-registry sweeps.

Validation

• router-core unit tests: 1,506 passed, 3 expected failures
• react-router unit tests: 986 passed, 1 skipped
• router-core and react-router TypeScript version matrices
• router-core and react-router ESLint targets (no errors; existing warnings only)
• full bundle-size suite: gzip decreased in all 17 scenarios; react-router.minimal decreased by 166 bytes

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View your CI Pipeline Execution ↗ for commit 79c00bc

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---

☁️ Nx Cloud last updated this comment at 2026-07-30 11:01:24 UTC

[github-actions]

🚀 Changeset Version Preview

4 package(s) bumped directly, 19 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
@tanstack/react-router	1.170.18 → 1.170.19	Changeset
@tanstack/router-core	1.171.15 → 1.171.16	Changeset
@tanstack/solid-router	1.170.18 → 1.170.19	Changeset
@tanstack/vue-router	1.170.17 → 1.170.18	Changeset
@tanstack/react-start	1.168.32 → 1.168.33	Dependent
@tanstack/react-start-client	1.168.16 → 1.168.17	Dependent
@tanstack/react-start-rsc	0.1.31 → 0.1.32	Dependent
@tanstack/react-start-server	1.167.22 → 1.167.23	Dependent
@tanstack/router-cli	1.167.21 → 1.167.22	Dependent
@tanstack/router-generator	1.167.21 → 1.167.22	Dependent
@tanstack/router-plugin	1.168.23 → 1.168.24	Dependent
@tanstack/router-vite-plugin	1.167.23 → 1.167.24	Dependent
@tanstack/solid-start	1.168.32 → 1.168.33	Dependent
@tanstack/solid-start-client	1.168.16 → 1.168.17	Dependent
@tanstack/solid-start-server	1.167.22 → 1.167.23	Dependent
@tanstack/start-client-core	1.170.14 → 1.170.15	Dependent
@tanstack/start-plugin-core	1.171.24 → 1.171.25	Dependent
@tanstack/start-server-core	1.169.17 → 1.169.18	Dependent
@tanstack/start-static-server-functions	1.167.19 → 1.167.20	Dependent
@tanstack/start-storage-context	1.167.17 → 1.167.18	Dependent
@tanstack/vue-start	1.168.31 → 1.168.32	Dependent
@tanstack/vue-start-client	1.167.19 → 1.167.20	Dependent
@tanstack/vue-start-server	1.167.22 → 1.167.23	Dependent

[github-actions]

Bundle Size Benchmarks

• Commit: 535fd16a1219
• Measured at: 2026-07-30T11:36:36.815Z
• Baseline source: history:a3ee355b5934
• 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	87.21 KiB	-145 B (-0.16%)	87.07 KiB	269.46 KiB	75.94 KiB	███████████▁
react-router.full	91.00 KiB	-69 B (-0.07%)	90.86 KiB	281.47 KiB	79.30 KiB	███████████▁
solid-router.minimal	34.91 KiB	-629 B (-1.73%)	34.79 KiB	100.24 KiB	31.48 KiB	███████████▁
solid-router.full	40.01 KiB	-582 B (-1.40%)	39.89 KiB	115.47 KiB	36.00 KiB	███████████▁
vue-router.minimal	52.22 KiB	-802 B (-1.48%)	52.08 KiB	143.40 KiB	47.04 KiB	███████████▁
vue-router.full	58.19 KiB	-769 B (-1.27%)	58.05 KiB	162.17 KiB	52.25 KiB	███████████▁
react-start.minimal	102.20 KiB	+215 B (+0.21%)	102.06 KiB	318.61 KiB	88.84 KiB	▁▁▁▁▁▁▁▁▁▁▁█
react-start.deferred-hydration	102.93 KiB	+214 B (+0.20%)	102.08 KiB	319.99 KiB	89.33 KiB	▁▁▁▁▁▁▁▁▁▁▁█
react-start.full	105.61 KiB	+251 B (+0.23%)	105.47 KiB	328.61 KiB	91.55 KiB	▁▁▁▁▁▁▁▁▁▁▁█
react-start.rsbuild.minimal	99.91 KiB	+223 B (+0.22%)	99.74 KiB	312.99 KiB	86.22 KiB	▁▁▁▁▁▁▁▁▁▁▁█
react-start.rsbuild.minimal-iife	100.31 KiB	+219 B (+0.21%)	100.14 KiB	313.93 KiB	86.56 KiB	▁▁▁▁▁▁▁▁▁▁▁█
react-start.rsbuild.full	103.24 KiB	+343 B (+0.33%)	103.07 KiB	323.14 KiB	88.92 KiB	▁▁▁▁▁▁▁▁▁▁▁█
solid-start.minimal	49.84 KiB	+239 B (+0.47%)	49.71 KiB	148.28 KiB	44.31 KiB	▁▁▁▁▁▁▁▁▁▁▁█
solid-start.deferred-hydration	53.11 KiB	+243 B (+0.45%)	49.77 KiB	156.32 KiB	47.28 KiB	▁▁▁▁▁▁▁▁▁▁▁█
solid-start.full	55.11 KiB	-318 B (-0.56%)	54.98 KiB	164.07 KiB	48.82 KiB	███████████▁
vue-start.minimal	70.59 KiB	-447 B (-0.61%)	70.46 KiB	201.32 KiB	62.65 KiB	███████████▁
vue-start.full	74.57 KiB	-476 B (-0.62%)	74.43 KiB	213.93 KiB	66.16 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: db9445d

[codspeed-hq]

Merging this PR will degrade performance by 12.74%

⚠️ 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

⚡ 5 improved benchmarks
❌ 8 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 error-paths unmatched (react)	261.3 KB	596.3 KB	-56.18%
❌	Memory	mem server error-paths redirect (vue)	306 KB	630.6 KB	-51.47%
❌	Memory	mem client unique-location-churn (react)	665.1 KB	872.7 KB	-23.79%
❌	Memory	mem server error-paths not-found (solid)	751.3 KB	818.3 KB	-8.18%
❌	Memory	mem server streaming-peak chunked (vue)	11.1 MB	11.6 MB	-4.85%
❌	Simulation	ssr control-flow route headers (react)	60.3 ms	62.7 ms	-3.8%
❌	Simulation	ssr selective (solid)	70.3 ms	72.9 ms	-3.62%
❌	Simulation	client-rewrites navigation loop (solid)	81.8 ms	84.5 ms	-3.19%
⚡	Memory	mem client navigation-churn (solid)	544.9 KB	498.5 KB	+9.31%
⚡	Memory	mem server error-paths redirect (react)	201.8 KB	185.2 KB	+8.97%
⚡	Simulation	ssr server-fn multipart (solid)	64.2 ms	61.2 ms	+4.86%
⚡	Simulation	client-preload interaction loop (react)	55.4 ms	53.4 ms	+3.63%
⚡	Simulation	ssr server-fn raw-stream (solid)	111.7 ms	108.1 ms	+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/always-run-beforeload (d49f47f) with fix-router-core-lane-match-loader (2d639e1)}