todowrite：tool call parameter error #10813

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1. jerrod-ji

   added

   bugSomething isn't workingSomething isn't working

   on Jan 27, 2026
2. github-actions

   assigned

   rekram1-node

   on Jan 27, 2026
3. github-actions commented on Jan 27, 2026

   

   github-actionsBot

   on Jan 27, 2026 – with GitHub Actions

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   This issue might be a duplicate of existing issues. Please check:

   • Tools with array/object parameters fail when LLM sends stringified JSON #7512: Tools with array/object parameters fail when LLM sends stringified JSON - This describes the exact same issue where the todos parameter is received as a stringified array instead of an actual array
   • AI_InvalidToolInputError: Invalid input for tool todowrite #1373: AI_InvalidToolInputError: Invalid input for tool todowrite - Another report of the same todowrite validation error with similar root cause

   Feel free to ignore if none of these address your specific case.
4. eliawk commented on Mar 18, 2026

   

   eliawk

   on Mar 18, 2026

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   same issue

   👍React with 👍3Reacted by Vladimir Yudintsev, leohidalgo and Quino Terrasa
5. leohidalgo commented on Mar 21, 2026

   

   leohidalgo

   on Mar 21, 2026

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   Workaround

   .opencode/plugins/todo-fix-plugin.ts

   export const TodoFixPlugin = async (ctx) => {
     return {
       "tool.execute.before": async (input, output) => {
         if (input.tool === "todowrite" && typeof output.args.todos === "string") {
           output.args.todos = JSON.parse(output.args.todos)
         }
       }
     }
   }

   👍React with 👍6Reacted by Quino Terrasa, shaked8634, Bendangelo, Meet Kotadiya, Marsel Arduanov and Maxim
6. thdxr

   removed

   bugSomething isn't workingSomething isn't working

   on May 3, 2026
7. edikid commented on Jul 1, 2026

   

   edikid

   on Jul 1, 2026

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   Still reproduces on opencode 1.17.11, and a heads-up for anyone landing here: the tool.execute.before → JSON.parse(todos) plugin workaround posted earlier in this thread no longer works on current opencode.

   I instrumented a bare version of that workaround (only tool.execute.before, nothing else) and confirmed with markers that for a stringified todos the hook never fires — the call is rejected at argument validation before execute.before runs:

   EXECUTE_BEFORE todosType=string : 0   # stringified calls never reach execute.before
   EXECUTE_BEFORE todosType=object : 1   # only native-array calls do
   

   Why it used to work and now doesn't: the error format in this thread changed from the Zod style (code: "invalid_type", "Invalid input: expected array, received string") to SchemaError(Expected array, got "<string>"). Tool-argument validation moved from Zod to Effect Schema, and it now runs ahead of tool.execute.before, so no plugin can repair the args in time.

   For completeness, none of the plugin hooks can fix this on 1.17.11:

   • tool.definition overriding a built-in tool's parameters/jsonSchema is not used for validation (verified by instrumentation: the override's validate is never called for the built-in todowrite).
   • tool.execute.before runs after validation (markers above).
   • A shadow/custom tool can't replace todowrite because the SDK exposes only GET /session/{id}/todo (no write API), so a plugin can't update todo state.

   Trigger (detailed writeup in #34652): Claude via the native Anthropic provider intermittently emits nested array tool args as JSON strings; OpenAI/function-calling models don't. It is intermittent and not size-gated — even an empty array [] has been observed arriving as "[]".

   Suggested fix: coerce a stringified tool-arg back to the expected type during tool-arg decoding (scoped strictly so it can't mask unrelated errors), or let plugin tool.definition overrides drive validation for built-in tools so the ecosystem can patch provider quirks without a core change.

   👍React with 👍1Reacted by Timothy Corbett-Clark
8. edikid commented on Jul 1, 2026

   

   edikid

   on Jul 1, 2026

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   Quick confirming update from #34652: retested today on the latest opencode (1.17.12) with a newer Claude model (claude-sonnet-5, not the Opus I originally tested) — still reproduces. Same intermittent, non-size-gated pattern (3 consecutive todowrite calls in a fresh session: 7-item payload succeeded, 8-item and even a 1-item payload both failed with the same SchemaError).

   So this isn't an Opus-only quirk and it isn't fixed in the current release. Full evidence and the suggested fix are in #34652.
9. github-actions commented on Aug 31, 2026

   

   github-actionsBot

   on Aug 31, 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.

   👎React with 👎1Reacted by Mikhail Fedorov
10. github-actions

    closed this as not plannedon Aug 31, 2026