Clarify search replace line matching

[wwwillchen]

Summary

• Clarifies that local-agent search_replace matching is line-based, not partial substring matching within a line.
• Updates both prompt guidance and tool schema descriptions so models include full lines when editing part of a line.
• Refreshes request/prompt snapshots that serialize the updated guidance.

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Note

Low Risk
Prompt and tool-description only; no change to search/replace execution logic.

Overview
Documents that local-agent search_replace matches whole lines, not substrings within a line, and that partial-line edits must use full original and replacement lines.

Updates the tool definition in search_replace.ts (description and old_string schema text), adds matching guidance to file_editing_tool_selection in local_agent_prompt.ts, and refreshes prompt unit snapshots plus E2E request snapshots so serialized tool/prompt payloads stay in sync. rules/local-agent-tools.md now reminds contributors to grep extensionless baselines under e2e-tests/snapshots/ when tool copy changes.

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[wwwillchen]

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[gemini-code-assist]

Code Review

This pull request updates the search_replace tool description and system prompts to explicitly clarify that matching is line-based and requires full-line matches rather than partial fragments. It also updates corresponding E2E test snapshots, prompt test snapshots, and the local agent tools documentation to reflect these changes and guide future snapshot updates. I have no feedback to provide as there are no review comments.

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[Copilot]

Pull request overview

This PR clarifies how the local-agent search_replace tool matches text by documenting that matching is line-based (whole-line matching), and updates prompt guidance plus snapshot baselines so serialized tool/prompt payloads stay consistent across tests.

Changes:

• Updated local-agent prompt guidance to explicitly instruct that partial-line edits must include the full original and replacement lines.
• Updated search_replace tool schema/description text to reflect line-based matching and discourage partial-line fragments.
• Refreshed prompt unit snapshots and E2E request snapshots (including extensionless baselines) to match the updated copy.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/prompts/local_agent_prompt.ts	Adds explicit guidance that search_replace matches whole lines and requires full-line old/new strings for partial-line edits.
src/prompts/snapshots/local_agent_prompt.test.ts.snap	Updates prompt snapshots to reflect the new guidance text.
src/pro/main/ipc/handlers/local_agent/tools/search_replace.ts	Updates tool schema and description text to document line-based matching and full-line requirements.
rules/local-agent-tools.md	Adds guidance to also grep extensionless E2E snapshot baselines when tool copy changes.
e2e-tests/snapshots/local_agent_explore_code.spec.ts_disabled	Refreshes serialized tool description/schema snapshot for search_replace (extensionless baseline).
e2e-tests/snapshots/local_agent_basic.spec.ts_local-agent---dump-request-1.txt	Refreshes request snapshot with updated search_replace description/schema text.
e2e-tests/snapshots/local_agent_auto.spec.ts_local-agent---auto-model-1.txt	Refreshes request snapshot to include updated prompt/tool copy.
e2e-tests/snapshots/local_agent_advanced.spec.ts_local-agent---mention-apps-1.txt	Refreshes request snapshot with updated search_replace description/schema text.
e2e-tests/snapshots/local_agent_advanced.spec.ts_local-agent---mcp-tool-search-1.txt	Refreshes request snapshot with updated search_replace description/schema text.

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[dyad-assistant]

Claude review: 1 inline finding(s).

[dyad-assistant]

🟡 MEDIUM

old_string field description drops exact-match whitespace guidance

The old old_string schema description explicitly told the model the text "must match the file contents exactly, including all whitespace and indentation." The new description focuses on line-based semantics and drops this exact-match emphasis. While the guidance still exists in the tool's main description body (the UNIQUENESS section still says "Include all whitespace, indentation, and surrounding code exactly as it appears in the file"), the per-field description is the most prominent place for per-parameter guidance. Models sometimes weight per-field descriptions more heavily, so losing the exact-match emphasis here could reduce initial attempt accuracy for whitespace fidelity.

💡 Suggestion: Consider restoring the exact-match phrasing alongside the new line-based guidance: "The text block to replace. Matching is line-based: each line in old_string must match a whole line in the file exactly (including whitespace and indentation), not just a substring within a line. To edit part of a line, include the entire original line in old_string and the entire edited line in new_string. The block must be unique within the file."

[dyad-assistant]

🔍 Dyadbot Code Review Summary

Verdict: ✅ YES - Ready to merge
Recommendation: ready

This PR correctly clarifies that the search_replace tool uses line-based matching. The claim is verified by search_replace_processor.ts -- findMatchPositions splits file content into lines and compares line-by-line, so partial-line inputs genuinely won't match. The changes are consistent across all three surfaces (tool definition, system prompt, snapshots), and no snapshot files were missed.

Issues Summary

Severity	File	Issue
🟡 MEDIUM	src/pro/main/ipc/handlers/local_agent/tools/search_replace.ts:33	old_string field description drops exact-match whitespace guidance

MEDIUM: old_string field description drops exact-match whitespace guidance (src/pro/main/ipc/handlers/local_agent/tools/search_replace.ts:33)

The old old_string schema description explicitly told the model the text "must match the file contents exactly, including all whitespace and indentation." The new description focuses on line-based semantics and drops this exact-match emphasis. While the guidance still exists in the tool's main description body (the UNIQUENESS section still says "Include all whitespace, indentation, and surrounding code exactly as it appears in the file"), the per-field description is prominent for model behavior. Consider restoring it alongside the new line-based guidance, e.g.: "...each line in old_string must match a whole line in the file exactly (including whitespace and indentation), not just a substring within a line."

🟢 Low Priority Notes (3 items)

• Slight wording inconsistency across surfaces - Tool description says "old_string must match whole file lines, not a partial fragment", the Pro prompt says "the target text must match whole file lines, not only a partial fragment", and the Basic prompt omits the negative clause entirely. All are semantically equivalent but create three phrasings to maintain. (src/pro/main/ipc/handlers/local_agent/tools/search_replace.ts, src/prompts/local_agent_prompt.ts)

• New rule names a specific file that may become stale - The added rule in rules/local-agent-tools.md calls out local_agent_explore_code.spec.ts_disabled by name. If this file is renamed or removed, the example goes stale, though the broader guidance ("search all e2e-tests/snapshots/ baselines") remains valuable. (rules/local-agent-tools.md)

• No enforcement change needed - The documentation says old_string "must match whole file lines," but no runtime validation is needed because the line-by-line matching architecture already prevents partial-line matches from succeeding. The tool returns a clear error if the model sends a partial line. This is purely an observation that the docs accurately describe existing behavior.

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