chore(deps): bump github.com/modelcontextprotocol/go-sdk from 1.3.1 to 1.6.1

[dependabot]

Bumps github.com/modelcontextprotocol/go-sdk from 1.3.1 to 1.6.1.

Release notes

Sourced from github.com/modelcontextprotocol/go-sdk's releases.

v1.6.1

This release adds an MCPGODEBUG flag to opt out of the Content-Type check on POST requests.

Behavior Changes

Prior to v1.6.0 (v1.4.0...v1.5.0), the Content-Type check on POST requests was gated by the same disablecrossoriginprotection MCPGODEBUG flag as the cross-origin protection. In v1.6.0, the cross-origin protection was disabled by default (replaced by the opt-in enableoriginverification flag), but the Content-Type check was kept on unconditionally, leaving no way to disable it. This release restores an escape hatch for both the Streamable HTTP and SSE transports: setting MCPGODEBUG=disablecontenttypecheck=1 skips the Content-Type: application/json validation on POST requests. See #957.

What's Changed

• mcp: add MCPGPDEBUG for opt-in Content-Type check by @​guglielmo-san in modelcontextprotocol/go-sdk#972

Full Changelog: modelcontextprotocol/go-sdk@v1.6.0...v1.6.1

v1.6.0

This release is equivalent to v1.6.0-pre.1. Thank you to those who tested the pre-release.

In this release we introduce several smaller fixes and improvements, and we started working for release 2026-06-30. The main new feature is the introduction of ClientCredentialsHandler for OAuth client credentials grant.

Add ClientCredentialsHandler for OAuth client credentials grant

Added ClientCredentialsHandler implementing auth.OAuthHandler using the OAuth 2.0 Client Credentials grant (RFC 6749 Section 4.4) for service-to-service authentication with pre-registered credentials.

• extauth: add ClientCredentialsHandler for OAuth client credentials grant by @​ravyg in modelcontextprotocol/go-sdk#895

2026-06-30 Release related PRs

• feat: add automatic application_type inference by @​guglielmo-san in modelcontextprotocol/go-sdk#904

  New application_type field is added to the ClientRegistrationMetadata for DynamicClientRegistration. If not specified, the application_type will be inferred from the RedirectURIs. This implements SEP-837.

• feat: HTTP Header Standardization for method and name by @​guglielmo-san in modelcontextprotocol/go-sdk#907

  By mirroring key fields from the JSON-RPC payload into HTTP headers, network intermediaries such as load balancers, proxies, and observability tools can route and process MCP traffic without deep packet inspection, reducing latency and computational overhead. This partially implements SEP-2243.

Behavior Changes

SetError Behavior Change

Previously the SetError method on CallToolResult always overwrote the Content field with the error text. Now SetError preserves the existing value if it has already been populated. You can restore the previous behavior by setting the environment variable seterroroverwrite=1.

• mcp: preserve existing Content in SetError by @​ravyg in modelcontextprotocol/go-sdk#864

Cross-Origin Protection Default Change

Previously (v1.4.1-v1.5.0) default (zero-value) cross-origin protection was applied when CrossOriginProtection in StreamableHTTPOptions was nil. Now cross-origin protection is not enabled by default when CrossOriginProtection is nil. You can restore the previous behavior (enable by default) by setting enableoriginverification=1.

• mcp: remove default cross origin protection by @​maciej-kisiel in modelcontextprotocol/go-sdk#906

... (truncated)

Commits

• d454bba mcp: add MCPGPDEBUG for opt-in Content-Type check (#972)
• f5f2015 MCPGODEBUG update for 1.6.0 (#893)
• e01639a feat: HTTP Header Standardization for method and name (#907)
• 93a41b2 internal/jsonrpc2: remove unused code (#910)
• 446beae mcp: Upgrade jsonschema-go (#912)
• 2e21834 extauth: add ClientCredentialsHandler for OAuth client credentials grant (#895)
• 2643b22 feat: add automatic application_type inference (#904)
• db50910 mcp: do not re-prompt OAuth after cancelled Authorize (#885)
• 5f2cd8f mcp: preserve transport errors in Write error chain (#888)
• 0edc597 Update README.md (#896)
• Additional commits viewable in compare view

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[blue4209211]

Folded into #94 — go-sdk 1.6.1 is included in that PR alongside CI hygiene fixes.

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version. You can also ignore all major, minor, or patch releases for a dependency by adding an ignore condition with the desired update_types to your config file.

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