Agents cannot read pasted content in their session — arrives as unreadable placeholder

Summary

When a user pastes text directly into an agent's session (via the agent panel), the agent receives a placeholder like [Pasted text #2 +12 lines] instead of the actual content. The agent has no way to retrieve or read the pasted text.

Steps to reproduce

1. Spawn a named subagent via the Agent tool
2. Open the agent's panel in the Claude Code UI
3. Paste multi-line text (e.g. log output, console text, a code snippet) into the agent's input and send
4. Observe: the agent sees [Pasted text #N +M lines] and cannot access the content

Expected behavior

Pasted text is delivered to the agent as inline content, the same way it works in the main session.

Actual behavior

The agent receives an opaque placeholder. It cannot retrieve the content. The user typically has to re-enter the text, or route it through the main session via SendMessage.

Impact

This affects any workflow where a user pastes diagnostic output, logs, or other content directly to an agent. The agent-direct-addressing feature makes this more likely as users naturally try to share context with agents the same way they share it with the main session.

Workaround

Route pasted content through the main session using SendMessage to the agent — this delivers it inline. Not obvious or discoverable.