encode MCP message headers with Base64#550
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deathbyknowledge merged 7 commits intocloudflare:mainfrom Oct 10, 2025
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deathbyknowledge
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Thank you for this. We can prune a lot of the code regarding format but this will fix the issue 👍
…pread in header : {
...existingHeaders,
deathbyknowledge
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Looks good, just needs to remove an unnecessary check.
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thanks! I've just removed the message size check, hopefully should be good to go @deathbyknowledge |
threepointone
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lgtm but I'll let @deathbyknowledge verify and land when he's up
deathbyknowledge
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encode MCP message headers with Base64 to support unicode characters
Fixes #549
brief description - detailed explanation is in the issue:
JSON-RPC payloads with Unicode characters (emoji, em dashes, smart quotes) fail in HTTP headers. This happened when creating a ChatGPT app with agents library because ChatGPT sends requests with Unicode characters.
Solution:
cf-mcp-messageheader contentcf-mcp-message-encodingheader to indicate encoding typeChanges:
src/mcp/utils.ts: encodes outgoing messagessrc/mcp/index.ts: decodes incoming messages with fallbacksrc/mcp/transport.ts: clears encoding headersrc/tests/mcp/transports/streamable-http.test.ts: added Unicode testTrade-offs:
zlibmodule for compression even if header size is not a concernEnd to end test: tested the solution by tarballing my fork into existing mcp server and it worked with previous messages that has unicode characters