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## Why this is needed `toAcpNotifications` can emit an `agent_message_chunk` whose content is an empty string. This happens in two situations: 1. **Streamed text deltas** — the `text` / `text_delta` case builds the update unconditionally from `chunk.text`, and the Claude Agent SDK can stream zero-length text deltas (for example, an empty trailing assistant block at the end of a turn). 2. **Full-string content** — the string-content path emits a chunk even when the string is empty. An empty message chunk carries no information, so at best it is noise. At worst it breaks clients: the ACP spec does not forbid empty content, so clients handle it inconsistently and some throw. In JetBrains Air the frontend event consumer throws on an empty-content `agent_message_chunk` (`Failed to handle agent event`); once that happens the transcript is **frozen for the rest of the turn** — no further updates render and queued prompts are never dispatched. In practice this reproduced repeatedly around image reads and end-of-turn, and the only recovery was restarting the IDE. Because the adapter is client-agnostic, this affects any ACP client that is strict about chunk content, not a single editor — so the correct place to fix it is here, in the adapter, rather than working around it in each client. ## Fix Do not emit empty content. Both call sites are guarded, mirroring the empty-`thinking` guard that already exists a few lines below in the same function, so behavior is consistent across content types: - `text` / `text_delta`: only build the update when `chunk.text.length > 0`; - string content: return `[]` when the string is empty. The change is intentionally minimal and conservative — no information is lost, and non-empty chunks are entirely unaffected. ## Tests Three unit tests added on `toAcpNotifications`: - empty string content → no notifications emitted; - non-empty string content → still emitted unchanged; - a stream containing an empty text block followed by a non-empty one → only the non-empty block is emitted. Full suite green (476 passing); eslint and prettier clean.
ACP adapter for the Claude Agent SDK
Use Claude Agent SDK from ACP-compatible clients!
This tool implements an ACP agent by using the official Claude Agent SDK, supporting:
- Context @-mentions
- Images
- Tool calls (with permission requests)
- Following
- Edit review
- TODO lists
- Interactive (and background) terminals
- Custom Slash commands
- Client MCP servers
Learn more about the Agent Client Protocol.
Contribution Policy
This project does not require a Contributor License Agreement (CLA). Instead, contributions are accepted under the following terms:
By contributing to this project, you agree that your contributions will be licensed under the Apache License, Version 2.0. You affirm that you have the legal right to submit your work, that you are not including code you do not have rights to, and that you understand contributions are made without requiring a Contributor License Agreement (CLA).