feat: lossless terminal output with on-demand retrieval

[hannesrudolph]

Summary

Refactors terminal command output handling to preserve full output losslessly. Instead of truncating large outputs and losing information, Roo now saves complete output to disk and provides the LLM with a preview plus the ability to retrieve the full content on demand.

Closes #10941

Problem

Users experienced several pain points with the previous terminal output handling:

• Lost output from long builds/tests: When running npm install, cargo build, test suites, or other commands that produce significant output, important error messages at the end could get truncated away
• Confusing settings: Two separate sliders for "line limit" and "character limit" were difficult to understand and tune correctly
• No recovery option: Once output was truncated, the LLM had no way to retrieve the lost information, often leading to missed errors or incomplete debugging

Solution

This PR implements a "persisted output" pattern:

1. Lossless preservation: All command output is captured. When output exceeds the preview threshold, it is automatically saved to disk in the task's storage directory
2. Smart previews: The LLM receives a configurable preview (5KB, 10KB, or 20KB) using head/tail preservation plus metadata about the full output size
3. On-demand retrieval: A new read_command_output tool lets the LLM fetch the complete output or search for specific patterns when needed
4. Automatic cleanup: Artifacts are cleaned up when tasks complete or when conversation history is rewound

User-Facing Changes

Settings

Before: Two confusing sliders

• "Terminal Output Line Limit" (slider)
• "Terminal Output Character Limit" (slider)

After: One simple dropdown

• "Command output preview size" with options: Small (5KB), Medium (10KB, default), Large (20KB)

Output Format

Small output (under preview threshold): Works exactly as before - full output shown inline.

Large output (over preview threshold): LLM receives:

• Head and tail of output (50/50 split of preview budget)
• [...N bytes omitted...] indicator in the middle
• Total size metadata
• Reference to full output artifact (cmd-{timestamp}.txt)
• Guidance to use read_command_output for full content or search

Technical Details

Output Limits (Aligned with Terminal Integration Spec)

Component	Value	Spec Reference
Preview sizes	5KB / 10KB / 20KB (default 10KB)	MODEL_TRUNCATION_BYTES (10KB)
read_command_output default	40KB	DEFAULT_MAX_OUTPUT_TOKENS (10,000 tokens × 4 bytes)

New Tool: read_command_output

// Read full output with pagination
{ "artifact_id": "cmd-1706119234567.txt", "offset": 0, "limit": 40960 }

// Search for patterns (like grep)
{ "artifact_id": "cmd-1706119234567.txt", "search": "error|failed|Error" }

Storage

Artifacts are stored at: globalStoragePath/tasks/{taskId}/command-output/cmd-{timestamp}.txt

Files Changed

• packages/types/src/global-settings.ts - Updated preview size constants (5KB/10KB/20KB)
• src/core/tools/ReadCommandOutputTool.ts - Updated default limit to 40KB
• src/core/prompts/tools/native-tools/read_command_output.ts - Updated tool description
• src/integrations/terminal/OutputInterceptor.ts - Head/tail buffer implementation
• src/core/tools/ExecuteCommandTool.ts - Integration with OutputInterceptor

Testing

• Added comprehensive unit tests for OutputInterceptor
• Added unit tests for ReadCommandOutputTool
• All 51 tests passing for the affected modules

[roomote]

Oroocle   See task on Roo Cloud

Re-review complete on latest commit. No additional issues found beyond what is already addressed.

• Update terminal output preview size labels (and locales) to match actual thresholds (5KB/10KB/20KB)

Previous reviews

• a3a50b7: Review #1
• fe913cb: Review #2
• c30924e: Review #3
• 61e7820: Review #4
• 765528e: Review #5
• b0ec581: Review #6
• d4680cd: Review #7
• 2e5bb4f: Review #8
• 650a421: Review #9
• 4f7e826: Review #10
• b9b3ee4: Review #11
• 771006d: Review #12
• 4125869: Review #13
• e61dc7c: Review #14
• 53939b6: Review #15
• 6c1bfe6: Review #16
• 06cb430: Review #17
• b89fe0e: Review #18
• b89fe0e: Review #19

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

[roomote]

Oroocle   Follow along on Roo Cloud

Flagged a few correctness and contract issues to address before merge.

• execute_command should respect terminalOutputPreviewSize (currently hardcoded to default)
• read_command_output native tool schema should not require optional params (search/offset/limit) under strict mode
• Avoid allocating Buffer(offset) in read_command_output for large offsets (line-number calculation can blow up memory)

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

[daniel-lxs]

LGTM