structuredClone regression causes high CPU/heat in v1.2.9+ #14458

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1. github-actions

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   rekram1-node

   on Feb 20, 2026
2. github-actions

   added

   coreAnything pertaining to core functionality of the application (opencode server stuff)Anything pertaining to core functionality of the application (opencode server stuff)

   perfIndicates a performance issue or need for optimizationIndicates a performance issue or need for optimization

   needs:complianceThis means the issue will auto-close after 2 hours.This means the issue will auto-close after 2 hours.

   and removed

   needs:complianceThis means the issue will auto-close after 2 hours.This means the issue will auto-close after 2 hours.

   on Feb 20, 2026
3. github-actions commented on Feb 20, 2026

   

   github-actionsBot

   on Feb 20, 2026 – with GitHub Actions

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   Thanks for updating the issue! It now follows the contributing guidelines with the required template structure, description, reproduction steps, and system context. Removing the compliance flag.

   👍React with 👍1Reacted by Tom
4. monotykamary commented on Feb 20, 2026

   

   monotykamary

   on Feb 20, 2026

   Last edited by monotykamary

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   Benchmark code used to verify the performance regression:

   #!/usr/bin/env bun
   /**
    * Benchmark comparing structuredClone vs previous implementation
    * Tests actual use cases from opencode codebase
    */
   
   import { clone } from "remeda"
   
   // Generate realistic mock data similar to opencode's message structures
   const generateMessage = (id: number, size: "small" | "medium" | "large") => {
     const textContent = {
       small: "Hello, this is a short message.",
       medium: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. ".repeat(50),
       large: "Lorem ipsum dolor sit amet, consectetur adipiscing elit. ".repeat(500),
     }[size]
   
     return {
       id,
       info: {
         id,
         role: id % 2 === 0 ? "user" : "assistant",
         time: Date.now(),
         name: null,
       },
       parts: [
         {
           type: "text",
           text: textContent,
           ignored: false,
           synthetic: false,
         },
       ],
     }
   }
   
   // Benchmark runner
   const benchmark = async <T>(
     name: string,
     fn: () => T,
     iterations: number,
   ): Promise<{ avgMs: number }> => {
     const start = performance.now()
     for (let i = 0; i < iterations; i++) fn()
     return { avgMs: (performance.now() - start) / iterations }
   }
   
   const runBenchmarks = async () => {
     const results = []
   
     for (const size of ["small", "medium", "large"] as const) {
       const messages = Array.from({ length: 20 }, (_, i) => generateMessage(i, size))
   
       const oldImpl = await benchmark("old impl", () => clone(messages), 10000)
       const newImpl = await benchmark("structuredClone", () => structuredClone(messages), 10000)
   
       results.push({ size, oldImpl: oldImpl.avgMs, newImpl: newImpl.avgMs })
     }
   
     console.table(results)
   }
   
   runBenchmarks()

   Run with:

   • bun run benchmark/clone.ts
   • bun run --expose-gc benchmark/clone.ts (for memory stats)

   The benchmark simulates opencode's actual data structures (session messages, prompt history) with realistic sizes. Results show structuredClone becomes exponentially slower as data size increases.
5. monotykamary commented on Feb 20, 2026

   

   monotykamary

   on Feb 20, 2026

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   May or may not be a red herring (could also be all of the FS stuff we're doing to make stuff platform agnostic). This one was the most obvious one I found this week.
6. rekram1-node commented on Feb 20, 2026

   

   rekram1-node

   on Feb 20, 2026

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   Are u sure??

   The clone call is incredibly expensive. I suspect due to the reference saving mechanism and linear lookup:
   
   https://github.com/remeda/remeda/blob/047c93e314bb9351b3ab93b34ce4b6cf67df7b1d/packages/remeda/src/clone.ts#L80
   
   Replacing it with const sessionMessages = structuredClone(msgs) call directly is much faster. Still takes 1352ms in this case, suggesting a large msgs object.
   
7. rekram1-node commented on Feb 20, 2026

   

   rekram1-node

   on Feb 20, 2026

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   are u using any plugins?
8. monotykamary commented on Feb 20, 2026

   

   monotykamary

   on Feb 20, 2026

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   my opencode is virgin
9. monotykamary commented on Feb 20, 2026

   

   monotykamary

   on Feb 20, 2026

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   My colleague does experience higher CPU. I see it with really long conversation threads + a ton of subagents; but otherwise, it's pretty okay at the moment. Might need to look in deeper.
10. github-actions commented on Apr 22, 2026

    

    github-actionsBot

    on Apr 22, 2026 – with GitHub Actions

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    To stay organized issues are automatically closed after 60 days of no activity. If the issue is still relevant please open a new one.
11. github-actions

    closed this as completedon Apr 22, 2026