Per-server "collapse by default" for MCP Apps (Atlassian's Jira cards take over Claude threads)

[adrianorocha-dev]

What happened

Since #29803, Claude threads render MCP Apps inline. Atlassian's MCP server attaches an app to its Jira tools that renders a full issue view: the whole description, acceptance criteria, and so on. It asks for a height large enough to fit all of it, on every call. In a single "refine this ticket" turn, that meant the main issue plus one card per linked issue, each up to 2,000px tall with its own scroll bar. The assistant's reply ended up spread between them.

T3 Code renders what the app asks for, so this is mainly Atlassian's design. But we can't change third-party apps, and as more MCP servers ship apps, users need a way to rein in the ones that don't behave.

Diagnosis

In McpAppFrame, the host provides no close or collapse control: its only button is "Exit full screen", and a card closes only when the app requests teardown. Nothing in settings or per server turns rendering off either. Cards grow to whatever height the app reports, up to MCP_APP_MAX_HEIGHT (2000). Other timeline rows, such as the changed-files section, can already be collapsed.

Proposal

A per-server "collapse by default" list in settings (a list of shame, if you will):

• Apps from listed servers render as a one-line collapsed row (server, tool, expand button) instead of an inline card.
• Expanding shows the app as it does today. Ideally there's also a "Collapse apps from this server" action on the card itself, so you don't have to dig through settings.
• Everything else stays as it is, so well-behaved apps keep rendering inline.

A host-side collapse button on every card would be useful on its own too, but the per-server default is what keeps a thread usable without clicking six times.

Steps to reproduce

1. Server on 0.1.8-nightly.20261105.4205 or later, Claude Code 2.1.301 or later.
2. Connect the Atlassian MCP connector.
3. In a Claude thread: "help me refine ABC-123 so it is ready to build".
4. Each Jira tool call renders as a tall inline Jira card.

Version

0.1.8-nightly.20261105.4218 (remote server background service and desktop app).

Environment

Desktop app on macOS (arm64) connected to a remote Linux server running as a background service. Claude Code 2.1.318.

Evidence

Screenshot withheld because it contains private work content. One turn produced six stacked Jira cards, each scrolling on its own.

Related issues

#29803

Fix applied or workaround

None. The only workaround is downgrading T3 Code or the Claude CLI.

Filed by

Triaged with Claude Opus 5.5 (claude-opus-5-5) in Claude Code, via t3 triage.

[Niklas-Mezynski]

Same here with the claude.ai Trello connector: every trelloReadCard/board read in a Claude thread now renders an inline Trello widget (ui://widget/trello-widget.html), so agent tasks that read cards in the background fill the thread with cards nobody asked to see.

+1 for per-server "collapse by default". A global "don't render MCP Apps inline" toggle would also help: in agent workflows the tool result is for the model, and the widget is rarely useful to the person.

T3 Code Nightly 0.1.8-nightly.20261105.4205, desktop on macOS 27.0.1 (arm64), Claude provider (Opus 5.5) via Claude Code.

[JulienZD]

Related discussion with redacted images showing how big the Jira MCP app cards are