`strict: false` for server functions by schiller-manuel · Pull Request #7277 · TanStack/router

schiller-manuel · 2026-04-27T22:07:07Z

Add a strict: false server function handler option to opt out of type-level serialization checks for server function return values.

Summary by CodeRabbit

New Features
- Added a new strict option for server functions to control serialization validation. Set strict: false to disable checks for both inputs and outputs, or configure strict: { output: false } to disable only output validation, enabling handling of non-serializable values.

coderabbitai · 2026-04-27T22:07:23Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: ea1a1f76-318a-4c43-b116-fa421ed63dd2

📥 Commits

Reviewing files that changed from the base of the PR and between 62538cc and 64eeb08.

📒 Files selected for processing (4)

.changeset/strict-server-functions.md
packages/start-client-core/src/createServerFn.ts
packages/start-client-core/src/index.tsx
packages/start-client-core/src/tests/createServerFn.test-d.ts

🚧 Files skipped from review as they are similar to previous changes (2)

packages/start-client-core/src/tests/createServerFn.test-d.ts
packages/start-client-core/src/createServerFn.ts

📝 Walkthrough

Walkthrough

This PR introduces a new strict option to createServerFn that controls type-level serialization validation. The feature allows disabling serializability checks globally (strict: false) or selectively for inputs/outputs via an options object, propagating a new TStrict generic parameter through the entire type system.

Changes

Cohort / File(s)	Summary
Type System Enhancement `packages/start-client-core/src/createServerFn.ts`	Introduces `TStrict` generic parameter (default `true`) threaded through `CreateServerFn`, `ServerFnOptions`, `ServerFnReturnType`, `ServerFnBaseOptions`, `ValidateValidatorInput`, `ConstrainValidator`, middleware/validator/handler/builder/types interfaces. Conditionally bypasses serializability validation for inputs/outputs based on strict configuration, while preserving POST/FormData special-case handling when strict is enabled.
Type Assertions & Tests `packages/start-client-core/src/tests/createServerFn.test-d.ts`	Adds comprehensive type-level test coverage verifying that disabled strict modes (`strict: false`, `strict.output: false`, `strict.input: false`) preserve non-serializable types (functions, Promises) and bypass validation checks as expected.
Public Type Exports `packages/start-client-core/src/index.tsx`	Exports new public types: `ServerFnOptions`, `ServerFnStrict`, `ServerFnStrictInput`, `ServerFnStrictOutput`.
Feature Documentation `.changeset/strict-server-functions.md`	Changeset documenting the new `strict` option for `createServerFn` with examples of both factory-level (`strict: false`) and targeted (`strict: { output: false }`) disabling of serialization checks.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A rabbit hops through types so true,
With strict controls now shiny new,
Functions flow where checks once stood,
Serialization, good and good!
Options dance in gentle ways,
Validation blooms in strictest days! 🌟

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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 summarizes the main change: introducing a `strict: false` option for server functions to disable type-level serialization checks.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

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Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch serverfn-strict-false

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nx-cloud · 2026-04-27T22:07:37Z

View your CI Pipeline Execution ↗ for commit 64eeb08

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:unit,tes...`	❌ Failed	5m 10s	View ↗
`nx run-many --target=build --exclude=examples/*...`	✅ Succeeded	1s	View ↗

☁️ Nx Cloud last updated this comment at 2026-04-30 21:25:12 UTC

github-actions · 2026-04-27T22:08:41Z

🚀 Changeset Version Preview

1 package(s) bumped directly, 13 bumped as dependents.

🟨 Minor bumps

Package	Version	Reason
`@tanstack/start-client-core`	1.167.22 → 1.168.0	Changeset

🟩 Patch bumps

Package	Version	Reason
`@tanstack/react-start`	1.167.55 → 1.167.56	Dependent
`@tanstack/react-start-client`	1.166.45 → 1.166.46	Dependent
`@tanstack/react-start-rsc`	0.0.34 → 0.0.35	Dependent
`@tanstack/react-start-server`	1.166.46 → 1.166.47	Dependent
`@tanstack/solid-start`	1.167.52 → 1.167.53	Dependent
`@tanstack/solid-start-client`	1.166.44 → 1.166.45	Dependent
`@tanstack/solid-start-server`	1.166.45 → 1.166.46	Dependent
`@tanstack/start-plugin-core`	1.169.10 → 1.169.11	Dependent
`@tanstack/start-server-core`	1.167.24 → 1.167.25	Dependent
`@tanstack/start-static-server-functions`	1.166.38 → 1.166.39	Dependent
`@tanstack/vue-start`	1.167.48 → 1.167.49	Dependent
`@tanstack/vue-start-client`	1.166.40 → 1.166.41	Dependent
`@tanstack/vue-start-server`	1.166.41 → 1.166.42	Dependent

github-actions · 2026-04-27T22:10:13Z

Bundle Size Benchmarks

Commit: cf5eb2f16816
Measured at: 2026-04-30T21:20:51.472Z
Baseline source: history:c4256c2c857f
Dashboard: bundle-size history

Scenario	Current (gzip)	Delta vs baseline	Raw	Brotli	Trend
`react-router.minimal`	87.15 KiB	0 B (0.00%)	273.94 KiB	75.70 KiB	███▇▇▇▇▇▁▁▁
`react-router.full`	90.68 KiB	0 B (0.00%)	285.45 KiB	78.71 KiB	▇▇▇█████▁▁▁
`solid-router.minimal`	35.38 KiB	0 B (0.00%)	106.25 KiB	31.81 KiB	███▇▇▇▇▇▁▁▁
`solid-router.full`	40.10 KiB	0 B (0.00%)	120.46 KiB	36.04 KiB	███▇▇▇▇▇▁▁▁
`vue-router.minimal`	53.15 KiB	0 B (0.00%)	151.39 KiB	47.73 KiB	████████▁▁▁
`vue-router.full`	58.28 KiB	0 B (0.00%)	167.56 KiB	52.18 KiB	████████▁▁▁
`react-start.minimal`	101.76 KiB	0 B (0.00%)	322.10 KiB	87.97 KiB	████████▁▁▁
`react-start.full`	105.19 KiB	0 B (0.00%)	332.43 KiB	90.96 KiB	████████▁▁▁
`react-start.rsbuild.minimal`	99.33 KiB	0 B (0.00%)	316.47 KiB	85.46 KiB	██████▂▂▁▁▁
`react-start.rsbuild.full`	102.63 KiB	0 B (0.00%)	326.90 KiB	88.28 KiB	██████▂▂▁▁▁
`solid-start.minimal`	49.40 KiB	0 B (0.00%)	152.08 KiB	43.60 KiB	███▇▇▇▇▇▁▁▁
`solid-start.full`	55.20 KiB	0 B (0.00%)	168.98 KiB	48.51 KiB	███▇▇▇▇▇▁▁▁

Trend sparkline is historical gzip bytes ending with this PR measurement; lower is better.

pkg-pr-new · 2026-04-27T22:10:14Z

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commit: 3161042

codspeed-hq · 2026-04-27T22:25:31Z

Merging this PR will not alter performance

✅ 5 untouched benchmarks
⏩ 1 skipped benchmark¹

_{Comparing serverfn-strict-false (3161042) with main (c4256c2)²}

1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩
No successful run was found on main (cf5eb2f) during the generation of this report, so c4256c2 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Add a `strict` option to `createServerFn` for type-level server function serialization checks

nx-cloud

Nx Cloud has identified a flaky task in your failed CI:

🔂 Since the failure was identified as flaky, we triggered a CI rerun by adding an empty commit to this branch.

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github-actions Bot added package: start-plugin-core package: start-client-core labels Apr 27, 2026

schiller-manuel requested a review from chorobin April 27, 2026 22:09

feat: strict: false for server functions

64eeb08

Add a `strict` option to `createServerFn` for type-level server function serialization checks

schiller-manuel force-pushed the serverfn-strict-false branch from 62538cc to 64eeb08 Compare April 30, 2026 21:01

nx-cloud Bot reviewed Apr 30, 2026

View reviewed changes

feat: strict: false for server functions [Self-Healing CI Rerun]

3161042

schiller-manuel merged commit 82b0613 into main Apr 30, 2026
16 of 17 checks passed

schiller-manuel deleted the serverfn-strict-false branch April 30, 2026 21:52

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`strict: false` for server functions#7277

`strict: false` for server functions#7277
schiller-manuel merged 2 commits intomainfrom
serverfn-strict-false

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