stacklok / toolhive-studio / 25735617285

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fix(playground): avoid renderer freeze on large MCP tool results (#2226)

* fix(playground): render large MCP tool results as raw text to avoid renderer freeze

Tool results above 50k chars now render in a <pre> with an opt-in
'Render as markdown' button instead of going through Streamdown.
JSON-shaped payloads bypass the markdown engine entirely and pretty-print.
Streamdown plugins are hoisted to module scope and the mermaid plugin is
dropped on this surface (scans every fenced block, no realistic tool
output uses it).

* test(playground): cover large/JSON/raw paths in tool-output rendering

Adds coverage for the JSON-detection path, the >50k raw fallback,
its 'Render as markdown' opt-in, the 500k truncation notice, and the
Copy button on both raw and JSON blocks.

* fix(playground): gate tool-output JSON parse on size/streaming, toast clipboard errors

Address review feedback on the large-tool-results PR:

- `tryFormatAsJson` now bails on streaming (partial JSON would fail-parse
  on every chunk → O(n²) over the stream) and on payloads above
  `RAW_RENDER_THRESHOLD` (the parse + stringify is itself a freeze risk
  for the multi-MB GitHub-MCP shapes this PR was written for; the raw
  `<pre>` branch already handles these correctly).
- The Copy button now awaits `navigator.clipboard.writeText` in a
  `try/catch` and surfaces a sonner toast on success/failure, instead of
  letting the rejection escape as an unhandled promise.

Tests cover the streaming-bypass, the oversized-JSON-bypass, and the
clipboard-failure-toast paths.

4821 of 7589 branches covered (63.53%)

28 of 28 new or added lines in 1 file covered. (100.0%)

7205 of 10500 relevant lines covered (68.62%)

119.01 hits per line