#23381: fix(tools): allow empty newText in edit tool for text deletion

## Summary - **Problem:** The `edit` tool rejects empty strings for `newText`/`new_string`, making text deletion impossible - **Why it matters:** Users cannot delete text by replacing it with an empty string — they must rewrite the entire file instead - **What changed:** Added `allowEmpty: true` to the `newText` parameter group in `CLAUDE_PARAM_GROUPS` - **What did NOT change:** All other parameter validation behavior, `oldText` still requires non-empty ## Change Type (select all) - [x] Bug fix - [ ] Feature - [ ] Refactor - [ ] Docs - [ ] Security hardening - [ ] Chore/infra ## Scope (select all touched areas) - [ ] Gateway / orchestration - [ ] Skills / tool execution - [ ] Auth / tokens - [ ] Memory / storage - [ ] Integrations - [ ] API / contracts - [x] UI / DX - [ ] CI/CD / infra ## Linked Issue/PR - Closes #23375 ## User-visible / Behavior Changes - `edit` tool now accepts empty string for `newText`/`new_string`, enabling text deletion by replacement ## Security Impact (required) - New permissions/capabilities? `No` - Secrets/tokens handling changed? `No` - New/changed network calls? `No` - Command/tool execution surface changed? `No` - Data access scope changed? `No` ## Repro + Verification ### Environment - OS: macOS - Runtime: Node.js - Integration/channel: All ### Steps 1. Call `edit` tool with `oldText: "some text"` and `newText: ""` 2. Before fix: throws "Missing required parameter: newText" 3. After fix: succeeds, deleting the matched text ### Expected - Empty `newText` is accepted, effectively deleting the matched text ### Actual - Before fix: `Missing required parameter: newText (newText or new_string). Supply correct parameters before retrying.` - After fix: replacement succeeds with empty string ## Evidence The validation in `assertRequiredParams` checks `value.trim().length > 0` by default. Adding `allowEmpty: true` bypasses this check: ```typescript if (group.allowEmpty) { return true; } return value.trim().length > 0; ``` ## Human Verification (required) - Verified scenarios: empty string newText, non-empty newText, missing newText - Edge cases checked: whitespace-only newText (still rejected without allowEmpty on oldText) - What I did **not** verify: end-to-end file edit with empty replacement ## Compatibility / Migration - Backward compatible? `Yes` - Config/env changes? `No` - Migration needed? `No` ## Failure Recovery (if this breaks) - How to disable/revert: revert the one-line change - Files/config to restore: `src/agents/pi-tools.read.ts` - Known bad symptoms: edit tool accepts empty replacement strings ## Risks and Mitigations None — this restores expected behavior for a valid use case <!-- greptile_comment --> <h3>Greptile Summary</h3> Added `allowEmpty: true` flag to the `newText` parameter in the edit tool configuration, enabling text deletion by replacing content with an empty string. Previously, the validation logic rejected empty strings for `newText`, forcing users to rewrite entire files when they wanted to delete text. This change restores expected behavior for a valid use case while maintaining all other validation constraints. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The change is a single-line addition that follows an established pattern used consistently across 30+ locations in the codebase. The validation logic properly handles the `allowEmpty` flag, and the change is backward compatible while fixing a legitimate bug. No security concerns identified. - No files require special attention _{Last reviewed commit: ffe8d86} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->