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[PR #12990] fix: handle undefined MCP tool output in stream processor #14467

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opened 2026-02-16 18:19:15 -05:00 by yindo · 0 comments
yindo commented 2026-02-16 18:19:15 -05:00
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Original Pull Request: https://github.com/anomalyco/opencode/pull/12990

State: open
Merged: No

Summary

Fixes #12987 — Kubernetes MCP server tools (and potentially other MCP servers) can fail with TypeError: undefined is not an object (evaluating 'output.output.toLowerCase') when tool-result payloads are not in the expected nested shape.

Root Cause

session/processor.ts assumed every tool-result chunk had:

value.output = { output: string, metadata: object, title: string, ... }

For some dynamic/provider/MCP result shapes, that assumption can be false (e.g. raw content[] payloads), causing undefined access and downstream crashes.

Changes

  • packages/opencode/src/session/processor.ts

    • Normalize dynamic tool results safely before persisting:
      • use nested output.output when present
      • fallback to content[] text extraction when available
      • fallback to raw string output
      • final fallback to JSON stringification for unknown payloads
    • Guard metadata/title/attachments with shape checks to avoid unsafe property access.

  • packages/opencode/src/session/prompt.ts

    • Guard MCP wrapper handling with result.content ?? [] to avoid iterating undefined content.

Verification

  • bun run typecheck (package-level) ✅
  • Push hook bun turbo typecheck (workspace-level) ✅
  • Focused regression tests:
    • bun test test/session/prompt-special-chars.test.ts test/session/prompt-missing-file.test.ts test/mcp/headers.test.ts ✅
**Original Pull Request:** https://github.com/anomalyco/opencode/pull/12990 **State:** open **Merged:** No --- ## Summary Fixes #12987 — Kubernetes MCP server tools (and potentially other MCP servers) can fail with `TypeError: undefined is not an object (evaluating 'output.output.toLowerCase')` when tool-result payloads are not in the expected nested shape. ## Root Cause `session/processor.ts` assumed every `tool-result` chunk had: ```ts value.output = { output: string, metadata: object, title: string, ... } ``` For some dynamic/provider/MCP result shapes, that assumption can be false (e.g. raw `content[]` payloads), causing undefined access and downstream crashes. ## Changes - **`packages/opencode/src/session/processor.ts`** - Normalize dynamic tool results safely before persisting: - use nested `output.output` when present - fallback to `content[]` text extraction when available - fallback to raw string output - final fallback to JSON stringification for unknown payloads - Guard metadata/title/attachments with shape checks to avoid unsafe property access. - **`packages/opencode/src/session/prompt.ts`** - Guard MCP wrapper handling with `result.content ?? []` to avoid iterating undefined content. ## Verification - `bun run typecheck` (package-level) ✅ - Push hook `bun turbo typecheck` (workspace-level) ✅ - Focused regression tests: - `bun test test/session/prompt-special-chars.test.ts test/session/prompt-missing-file.test.ts test/mcp/headers.test.ts` ✅
yindo added the pull-request label 2026-02-16 18:19:15 -05:00
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Reference: anomalyco/opencode#14467
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