fix: reject unexpanded shell vars in MCP args - #628
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Detect literal $1/$2-style placeholders from misconfigured MCP clients, return actionable ExpectedMcpError guidance, and keep those validation failures out of Sentry (including historical absolute-path messages). Co-authored-by: Kent C. Dodds <me+github@kentcdodds.com>
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July 24, 2026 19:57
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Summary
Sentry track E-1 (
EPICSHOP-EF,EPICSHOP-B3,EPICSHOP-B1,EPICSHOP-FR): one user’s MCP client was passing literal unexpanded shell placeholders ($1,$2) into@epic-web/workshop-mcp, producing ~1,600 events (~40% of epicshop project volume). Those are caller/config mistakes, not workshop bugs.This change:
workshopDirectory/exerciseNumbervalidationExpectedMcpErrorthat tells the user their MCP config has a literal$1/$2that was never substitutedbeforeSendfilter for the new messages plus the historicalmust be an absolute pathmessage (already fixed by Handle relative workshop directories in MCP #589 allowing relative paths)Sibling issues covered and resolved in Sentry:
EPICSHOP-EF,EPICSHOP-B3(double-report via mcp-server integration),EPICSHOP-B1,EPICSHOP-FR.Test plan
nx run @epic-web/workshop-mcp:testnx run @epic-web/workshop-mcp:typechecknx run @epic-web/workshop-mcp:buildRelease note
Patch release for
@epic-web/workshop-mcp(fix:commit). Publishes clearer arg-validation errors and keeps those expected failures out of Sentry.