fix(mcp-bridge): encode stderr notifications as JSON#13549
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shreemaan-abhishek wants to merge 5 commits into
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fix(mcp-bridge): encode stderr notifications as JSON#13549shreemaan-abhishek wants to merge 5 commits into
shreemaan-abhishek wants to merge 5 commits into
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Build the notifications/stderr message with core.json.encode instead of string concatenation, so subprocess stderr output containing double quotes, backslashes or other JSON special characters no longer breaks the framing of the JSON-RPC notification sent to the client.
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Pull request overview
This PR fixes malformed notifications/stderr JSON-RPC notifications emitted by the mcp-bridge plugin when the subprocess writes stderr lines containing JSON-special characters, by switching from manual string concatenation to core.json.encode.
Changes:
- Build
notifications/stderrmessages viacore.json.encodeto ensure correct JSON escaping. - Add a regression test that feeds stderr content containing quotes, backslashes, and
}}, and asserts the notification JSON round-trips correctly.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
apisix/plugins/mcp-bridge.lua |
Switch stderr notification construction to JSON encoding instead of string concatenation. |
t/plugin/mcp-bridge.t |
Add a regression test ensuring stderr content with JSON-special characters yields valid JSON. |
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Extract the notifications/stderr message construction into a helper that is also exercised directly by the regression test, log the encode error on the fallback path, and reap the spawned subprocess in the test.
Document the mcp-bridge plugin in both languages, add it to the AI plugin category in the sidebars, and note that the plugin is currently experimental.
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Description
The
mcp-bridgeplugin forwards a spawned MCP subprocess's stderr to theclient as a
notifications/stderrJSON-RPC message. The message was builtby concatenating the raw stderr line into a JSON string literal, so any
stderr output containing JSON special characters (double quotes,
backslashes, etc.) produced a malformed JSON-RPC notification and broke the
framing of the message sent to the client.
This change builds the notification with
core.json.encodeinstead, whichproperly escapes the content. A regression test in
t/plugin/mcp-bridge.tfeeds a stderr line containing quotes, a backslash and a
}}sequence andasserts the resulting notification is well-formed JSON that round-trips back
to the original content.
Which issue(s) this PR fixes:
Fixes #
Checklist