feat: add line_range support to simpleReadFileTool and improve truncation notices

[roomote]

This PR attempts to address Issue #10239.

Summary

This PR adds line_range parameter support to simpleReadFileTool and improves truncation notices across both read file tools to provide clearer instructions for incremental file reading.

Problem

As identified in the issue, simpleReadFileTool (used by models that only support single file reads) did NOT support line ranges. This was explicitly stated in the code comments:

* This is a streamlined version of readFileTool that:
* - Does not support line ranges  // <-- The problem!

When files were truncated, the tool would suggest using line_range but the tool could not actually process that parameter, causing models to repeatedly re-read from line 1.

Changes

1. Added line_range parameter support to simpleReadFileTool

• Added parseLineRange() helper function to parse "start-end" format
• Added line_range to toolParamNames in src/shared/tools.ts
• Implemented line range reading logic using the existing readLines function
• Updated tool description in simple-read-file.ts with examples

2. Improved truncation notices

Updated truncation messages across both tools to include:

• The exact next line number to continue from
• A concrete syntax example for continuation

Before:

Showing only 500 of 2000 total lines. File is too large for complete display

After:

Showing lines 1-500 of 2000 total lines. To continue reading, use the read_file tool again with the line_range parameter starting at line 501 (e.g., <line_range>501-1000</line_range>)

Files Modified

• src/core/prompts/tools/simple-read-file.ts - Updated tool description with line_range parameter
• src/core/tools/simpleReadFileTool.ts - Added line_range parsing and handling
• src/core/tools/ReadFileTool.ts - Improved truncation notices
• src/shared/tools.ts - Added line_range to toolParamNames

Testing

• TypeScript compilation passes
• ESLint passes with no warnings
• Related tests pass (filter-tools-for-mode.spec.ts, converters.spec.ts)

Feedback and guidance are welcome!

[roomote]

Rooviewer   See task on Roo Cloud

Review complete. No issues found.

The latest commit addresses @pwilkin's feedback by always including line_range parameter documentation in the tool description regardless of the partialReadsEnabled setting. This ensures users always see how to use line ranges when truncation notices suggest using them.

Previous reviews

• 756cbfc: Review #1
• 13ab4dd: Review #2

_{Mention @roomote in a comment to request specific changes to this pull request or fix all unresolved issues.}

[pwilkin]

@roomote Seems like you have an error in the new message here:

const notice = Showing only definitions of ${totalLines} total lines. To read actual content, use the read_file tool again with the line_range parameter (e.g., line_ranges: [[1, 500]])

[roomote]

Fixaroo   See task on Roo Cloud

Fixed the parameter name inconsistency: changed "line_range parameter" to "line_ranges parameter" in all 3 truncation notice messages to match the example syntax. All local checks passed.

_{View commit | Revert commit}

[pwilkin]

@roomote Also, can you please check the logic for src/core/prompts/tools/read-file.ts whether the partialReads parameter is always enabled when there is a context limit? Because another reason I can imagine this error happening is if the tool description doesn't actually mention the line_range parameter.

[roomote]

Fixaroo   See task on Roo Cloud

Fixed the reported issue. The read-file.ts tool description now always includes line_range information, regardless of the partialReadsEnabled setting. This ensures models know how to continue reading truncated files even when truncation happens due to context token budget limits (not just maxReadFileLine limits). All local checks passed.

_{View commit | Revert commit}