Add frameDomains and baseUriDomains CSP support for MCP Apps #6399
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Implements early support for proposed CSP extensions to the MCP Apps spec: - frameDomains: Controls frame-src directive for nested iframes - baseUriDomains: Controls base-uri directive This anticipates changes proposed in: modelcontextprotocol/ext-apps#158 Note: The upstream spec PR is not yet merged, but we're implementing early to validate the approach.
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Pull request overview
This PR implements early support for two proposed CSP extensions to the MCP Apps specification: frameDomains and baseUriDomains. These additions allow MCP apps to control iframe nesting and base URI policies through CSP directives.
Key changes:
- Added
frameDomainsparameter controllingframe-srcCSP directive (defaults to blocking nested iframes) - Added
baseUriDomainsparameter controllingbase-uriCSP directive (defaults to 'self' only)
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
crates/goose-server/src/routes/mcp_app_proxy.rs |
Adds query parameters and CSP generation logic for frame-src and base-uri directives |
ui/desktop/src/components/McpApps/utils.ts |
Extends CSP type definition and URL builder with frameDomains and baseUriDomains support |
alexhancock
approved these changes
Jan 8, 2026
DOsinga
reviewed
Jan 9, 2026
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DOsinga
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DOsinga
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I'm all for moving fast, but let's make sure that the relevant people look at the PRs before we merge them? this utils.ts is getting a bit out of hand I would say in this case
wpfleger96
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Jan 9, 2026
* main: (89 commits) fix(google): treat signed text as regular content in streaming (#6400) Add frameDomains and baseUriDomains CSP support for MCP Apps (#6399) fix(ci): add missing dependencies to openapi-schema-check job (#6367) feat: http proxy support Add support for changing working dir and extensions in same window/session (#6057) Sort keys in canonical models (#6403) added validation and debug for invalid call tool result (#6368) Update MCP apps tutorial: fix _meta structure and version prereq (#6404) Fixed fonts (#6389) Update confidence levels prompt injection detection to reduce false positive rates (#6390) Add ML-based prompt injection detection (#5623) docs: update custom extensions tutorial (#6388) fix ResultsFormat error when loading old sessions (#6385) docs: add MCP Apps tutorial and documentation updates (#6384) changed z-index to make sure the search highlighter does not appear on modal overlay (#6386) Handling special claude model response in github copilot provider (#6369) fix: prevent duplicate rendering when tool returns both mcp-ui and mcp-apps resources (#6378) fix: update MCP Apps _meta.ui.resourceUri to use nested format (SEP-1865) (#6372) feat(providers): add streaming support for Google Gemini provider (#6191) Blog: edit links in mcp apps post (#6371) ...
wpfleger96
added a commit
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Jan 9, 2026
* main: (89 commits) fix(google): treat signed text as regular content in streaming (#6400) Add frameDomains and baseUriDomains CSP support for MCP Apps (#6399) fix(ci): add missing dependencies to openapi-schema-check job (#6367) feat: http proxy support Add support for changing working dir and extensions in same window/session (#6057) Sort keys in canonical models (#6403) added validation and debug for invalid call tool result (#6368) Update MCP apps tutorial: fix _meta structure and version prereq (#6404) Fixed fonts (#6389) Update confidence levels prompt injection detection to reduce false positive rates (#6390) Add ML-based prompt injection detection (#5623) docs: update custom extensions tutorial (#6388) fix ResultsFormat error when loading old sessions (#6385) docs: add MCP Apps tutorial and documentation updates (#6384) changed z-index to make sure the search highlighter does not appear on modal overlay (#6386) Handling special claude model response in github copilot provider (#6369) fix: prevent duplicate rendering when tool returns both mcp-ui and mcp-apps resources (#6378) fix: update MCP Apps _meta.ui.resourceUri to use nested format (SEP-1865) (#6372) feat(providers): add streaming support for Google Gemini provider (#6191) Blog: edit links in mcp apps post (#6371) ...
fbalicchia
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Jan 13, 2026
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Summary
Implements early support for proposed CSP extensions to the MCP Apps specification:
frameDomains: Controls theframe-srcCSP directive for nested iframesframe-src 'none'(no nested iframes allowed)frame-src <origins>baseUriDomains: Controls thebase-uriCSP directivebase-uri 'self'base-uri 'self' <domains>Context
This PR anticipates changes proposed in the MCP Apps spec:
modelcontextprotocol/ext-apps#158
Why?
Enables MCP App experiences like this Svelte playground, where the app injects an iframe into itself.
Changes
crates/goose-server/src/routes/mcp_app_proxy.rs: Addedframe_domainsandbase_uri_domainsquery parameters and CSP generation logicui/desktop/src/components/McpApps/utils.ts: AddedframeDomainsandbaseUriDomainsto the CSP type and URL builder