TanStack Router SSR: seroval-plugins version constraint incompatible with seroval v1.4.0

[austinm911]

Which project does this relate to?

Router

Describe the bug

Claude generated the summary below. It does indeed look like seroval just merged a large project refactor

https://github.com/lxsmnsyc/seroval/pull/65/files#diff-ec8d5ffcbab68429c095a0d64c3f313375fd7fcac972795f23488d5946e7874d

Problem Statement

TanStack Router (v1.136.x and earlier) declares dependencies on incompatible
versions of seroval and seroval-plugins:

  "@tanstack/router-core@1.136.17": {                                            
    "dependencies": {                                                            
      "seroval": "^1.3.2",                                                       
      "seroval-plugins": "^1.3.2"                                                
    }                                                                            
  }                                                                              

This causes a critical SSR failure when the environment resolves to seroval
v1.4.0 (which may happen due to other dependencies or monorepo setups):

  Error: ctx.createEffectfulFunction is not a function                           
      at web.mjs:32                                                              
      at processTicksAndRejection (async :...)                                   
  Error: Unable to enqueue response (SSR streaming failed)                       

Root Cause

seroval v1.4.0 is incompatible with seroval-plugins v1.3.x:

1. seroval v1.4.0 removed or renamed the createEffectfulFunction API
2. seroval-plugins v1.3.x was built against seroval v1.3.x and still calls
   ctx.createEffectfulFunction()
3. When both versions coexist in the dependency tree (e.g., due to other
   packages requiring seroval v1.4.0), the older plugins try to call a method that
   no longer exists

Why This Happens:

• Other dependencies in the ecosystem may declare seroval@^1.4.0
• Monorepo setups or overrides may force a newer seroval version
• TanStack Router's pinned v1.3.2 constraint doesn't prevent newer versions from
  being installed alongside it
• The older seroval-plugins v1.3.x then fails at runtime

Impact

• Blocking Issue: SSR breaks completely when seroval v1.4.0 is present in the
  dependency tree
• Cascading Failures: Data serialization fails during SSR streaming, affecting
  all routes
• No User Workaround Available: Users cannot fix this without package.json
  overrides (not all package managers support this)

Affected Versions

• TanStack Router: v1.136.x and earlier
• TanStack Start: v1.136.x and earlier
• seroval: v1.4.0+
• seroval-plugins: v1.3.x
• Environments: Any project using TanStack Start with SSR where seroval v1.4.0+
  is present

Reproduction

In a monorepo or project where seroval v1.4.0 is declared:

1. Install @tanstack/react-start@latest (which depends on TanStack Router
   v1.136.x)
2. Ensure seroval v1.4.0 is present in node_modules (via direct dependency or
   other packages)
3. Run SSR (dev or build)
4. Observe: "ctx.createEffectfulFunction is not a function" error during
   serialization

Solution

Update TanStack Router packages to support seroval v1.4.0+:

Update the dependency declarations in:

• @tanstack/router-core
• @tanstack/start-client-core
• @tanstack/start-server-core

From:

  {                                                                              
    "dependencies": {                                                            
      "seroval": "^1.3.2",                                                       
      "seroval-plugins": "^1.3.2"                                                
    }                                                                            
  }                                                                              

To:

  {                                                                              
    "dependencies": {                                                            
      "seroval": "^1.4.0",                                                       
      "seroval-plugins": "^1.4.0"                                                
    }                                                                            
  }                                                                              

Or (if backward compatibility with v1.3.x is desired):

  {                                                                              
    "dependencies": {                                                            
      "seroval": "^1.3.2 || ^1.4.0",                                             
      "seroval-plugins": "^1.3.2 || ^1.4.0"                                      
    }                                                                            
  }                                                                              

Implementation Notes

• seroval v1.4.0+ should be compatible with existing TanStack Router SSR code
  (seroval maintains backward compatibility in the public plugin API)

• seroval-plugins v1.4.0 was specifically built to work with seroval v1.4.0

• This change should be released as a patch version (e.g., 1.136.18) with
  appropriate testing

• Affected packages: @tanstack/router-core, @tanstack/start-client-core,
  @tanstack/start-server-core

Your Example Website or App

see above

Steps to Reproduce the Bug or Issue

See above

Expected behavior

see above

Screenshots or Videos

No response

Platform

• Router / Start Version: [e.g. 1.121.0]
• OS: [e.g. macOS, Windows, Linux]
• Browser: [e.g. Chrome, Safari, Firefox]
• Browser Version: [e.g. 91.1]
• Bundler: [e.g. vite]
• Bundler Version: [e.g. 7.0.0]

Additional context

No response

[birkskyum]

@austinm911 there will be new releases out at the end of the ongoing CI run. I've updated the tanstack router/start to seroval 1.4.0 - i think that'll solve your issue.