feat: enrich subtask handoff with structured context summaries (Phase 1 of #12330)

[roomote-v0]

Related GitHub Issue

Closes: #12330 (Phase 1)

Description

This PR attempts to address Issue #12330 by implementing Phase 1: Enhanced context handoff visibility between parent and child tasks during delegation.

When a subtask completes via attempt_completion, the handoff back to the parent now includes a structured summary of what the subtask accomplished, rather than just the raw completion text. This gives both the parent LLM and the user much better visibility into the subtask's work.

Key implementation details:

• SubtaskSummary type (packages/types/src/history.ts): New structured type capturing mode, files modified/read, commands executed, tool usage counts, and todo completion stats.
• buildSubtaskSummary utility (src/core/task/buildSubtaskSummary.ts): Scans the child task's API conversation history to extract tool_use blocks and build metadata. Also provides formatSubtaskSummaryForApi for enriched parent LLM context.
• AttemptCompletionTool: Builds the structured summary on subtask completion, with try/catch fallback to plain text for robustness.
• reopenParentFromDelegation: Parses the structured summary, uses enriched markdown format for the API history (so the parent LLM gets files changed, mode, commands, etc.) and passes raw JSON to the UI message.
• ChatRow UI: Detects JSON summaries and renders structured data with mode badge, file lists, command lists, and todo progress. Falls back to plain markdown for backward compatibility.
• Fully backward compatible: Plain-text summaries from older tasks still render correctly.

Test Procedure

• 19 new unit tests in src/core/task/__tests__/buildSubtaskSummary.spec.ts covering:
  • File extraction from write_to_file, apply_diff, read_file, execute_command tool_use blocks
  • Deduplication of modified files
  • Long command truncation
  • Tool usage summary extraction
  • Todo stats computation
  • Edge cases (empty history, non-array content, user messages)
  • formatSubtaskSummaryForApi output formatting
• Verified all existing delegation tests still pass (newTaskTool.spec.ts, history-resume-delegation.spec.ts, nested-delegation-resume.spec.ts, new-task-delegation.spec.ts)

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue
• Scope: Changes are focused on subtask handoff enrichment
• Self-Review: Performed thorough self-review
• Testing: 19 new tests added, all existing delegation tests pass
• Documentation Impact: No user-facing docs changes needed for this phase
• Contribution Guidelines: Read and agreed

Documentation Updates

No user-facing documentation changes required. This enhancement is transparent to existing workflows.

Feedback and guidance are welcome.

Interactively review PR in Roo Code Cloud

[easonLiangWorldedtech]

Thanks for the quick work on this!

I noticed the check-translations check is failing. It seems the new strings for the "Task Delegation" section need to be added to the translation files. Could you fix that?

Overall the implementation looks clean and non-intrusive. Appreciate you getting the first version out so fast.

@roomote

[roomote-v0]

Fixaroo   See task

Added the 4 missing subtask translation keys (filesModified, filesRead, commandsExecuted, todoStats) to all 17 non-English locale chat.json files. Translation validation script passes clean.

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