Anthony Eid 6bca2136a1 agent: Batch streaming edit operations (#58037) ... ## Summary While profiling agent sessions that make a lot of `edit_file` operations, I noticed the LSP `textDocument/didChange` handler firing excessively. Looking into this, I found out that the streaming edit pipeline was applying each `CharOperation` from `StreamingDiff` as its own `buffer.edit` transaction, and every transaction emits a `BufferEvent::Edited` event. Each event can trigger several other expensive events depending on whether the buffer is being rendered in an editor or is registered with a language. For example, there are `didChange` LSP events, the editor's on edit work (matching brackets, bracket colorization, code actions, outline), and more. A single `edit_file` could trigger hundreds of these at the higher end in a single synchronous app update, which would block the foreground thread for a bit and cause Zed to drop frames. I fixed this by collecting all of a chunk's `CharOperation`s and applying them in one `buffer.edit` call, so only a single `BufferEvent::Edited` event gets emitted. This is safe because operations are non overlapping by design of streaming diff (the edit cursor only advances). ## Why this wasn't caught earlier The cost only fully appears when a buffer is both registered with a language server and rendered in an editor. Without that, most of the per transaction observers never run, so the existing `edit_file_tool` benchmark (which ran the tool against a bare buffer) didn't surface it. I reworked the benchmark to open the edited buffer in an editor view, register a fake language server with per edit diagnostics, and lay out a frame, so it exercises the same cascade as the real editor. I also added a larger fixture. ## Results Measured with the `release-fast` profile on the reworked benchmark: | Fixture | Initial file | Before | After | Improvement | | --- | --- | --- | --- | --- | | `tiny_function_rewrite` | 1.4 KB | 31.1 ms | 12.1 ms | −61% | | `small_function_rewrite` | 3.0 KB | 42.4 ms | 19.3 ms | −55% | | `medium_many_small_changes` | 4.6 KB | 309.2 ms | 151.5 ms | −51% | | `medium_insertions` | 4.6 KB | 171.8 ms | 126.1 ms | −27% | | `large_multi_edit` | 44 KB | 9,549 ms | 919 ms | −90% | Self-Review Checklist: - [x] I've reviewed my own diff for quality, security, and reliability - [x] Unsafe blocks (if any) have justifying comments - [x] The content is consistent with the UI/UX checklist - [x] Tests cover the new/changed behavior - [x] Performance impact has been considered and is acceptable Release Notes: - Improved agent's edit file tool performance		2026-05-29 09:49:55 +00:00
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edit_file_tool.rs	agent: Batch streaming edit operations (#58037)	2026-05-29 09:49:55 +00:00