fix: accumulate OAuth scopes on 401/403 instead of overwriting#1657
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rechedev9 wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
fix: accumulate OAuth scopes on 401/403 instead of overwriting#1657rechedev9 wants to merge 1 commit intomodelcontextprotocol:mainfrom
rechedev9 wants to merge 1 commit intomodelcontextprotocol:mainfrom
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Replace raw `this._scope = scope` assignments with a `mergeScopes()` utility that unions existing and incoming scope strings. Prevents infinite re-authorization loops when an MCP server uses per-operation progressive authorization (RFC 6750 §3.1). Fixes modelcontextprotocol#1582
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
commit: |
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Summary
this._scope = scopeassignments with amergeScopes()utility that unions existing and incoming scope strings (space-separated,Set-based deduplication, insertion-order stable)StreamableHTTPClientTransport(lines 520, 553) andSSEClientTransport(lines 167, 281)Root cause
The 401/403 handlers overwrote
this._scopewith only the scope from the currentWWW-Authenticateheader. With per-operation scopes (e.g.,initfor initialize,mcp:tools:readfor tools/list), re-authorizing for the new scope dropped coverage of all prior scopes, causing an infinite loop between operations.Approach
A module-level unexported
mergeScopes(existing, incoming)function:Set<string>(deduplicates, preserves insertion order)undefinedwhen the result is empty (matches_scope?: stringsemantics)Duplicated in both transport files to keep each self-contained — no new shared modules or public API surface.
Testing
Added 8 regression tests:
streamableHttp.test.ts: mergeScopes edge cases, multi-scope accumulation across 401→403 sequences, circuit-breaker compatibilitysse.test.ts: scope accumulation in EventSource reconnect and send pathsAll 265 client tests pass. Typecheck and lint pass.
Fixes #1582