feat(cli): add /thinkback command to review session timeline of decisions, changes and fixes

[wenshao]

Summary

Add a new /thinkback slash command that leverages the LLM to analyze conversation history and generate a structured timeline of key events in the current session.

Comparison with Claude Code

Claude Code currently does not have a built-in session timeline review command. Users must manually scroll through conversation or rely on /compact (context compression) which discards detail rather than summarizing it.

Capability	Claude Code	Qwen Code (/thinkback)
Session timeline review	❌ Not available	✅ Auto-generated structured timeline
Filter by time range	❌ N/A	✅ --from "1h ago"
Filter by topic	❌ N/A	✅ --topic "auth"
Key decision tracking	❌ Manual scrolling	✅ Highlights decisions, changes, fixes
Multi-mode support	N/A	✅ interactive / non_interactive / acp
i18n	N/A	✅ 6 locales (en/zh/ja/ru/pt/de)

This is a new capability beyond Claude Code's feature set, giving Qwen Code users a structured way to review session progress without losing context.

Before / After

Before

Users have no structured way to review what happened during a session. To recall key decisions, file changes, or bug fixes, they must manually scroll through the entire conversation history.

After

Users can run /thinkback to get an auto-generated timeline:

> /thinkback

# Timeline Review
- **Step 1** — [Change] Updated auth middleware to fix session token storage (auth.ts)
- **Step 2** — [Decision] Switched to JWT-based tokens for compliance (config.ts, auth.ts)
- **Step 3** — [Fix] Resolved token refresh race condition (tokenManager.ts)

With optional filtering:

> /thinkback --from "30 min ago" --topic "auth"

Changes

File	Change
thinkbackCommand.ts	New command implementation following summaryCommand pattern
thinkbackCommand.test.ts	5 test cases covering empty history, generation, args parsing, missing config, concurrent blocking
BuiltinCommandLoader.ts	Register the new command
en.js, zh.js, ja.js, ru.js, pt.js, de.js	i18n keys for all 6 locales

Review notes (fixes applied during audit)

Original implementation was by gemini-3.1-pro-preview. The following issues were found and fixed:

1. TS compile error — import('./types.js').HistoryItemWithoutId referenced wrong module, fixed to import('../types.js')
2. Missing i18n keys — All UI-facing strings were unregistered in locale files, added to all 6 locales (en/zh/ja + en-fallback for ru/pt/de)
3. LLM prompts wrapped in t() — Translating prompts sent to the LLM degrades output quality. Removed t() wrapping, now uses plain strings (consistent with btwCommand pattern)

Test plan

• npx tsc --noEmit — no type errors
• vitest run thinkbackCommand.test.ts — 5/5 passed
• vitest run BuiltinCommandLoader.test.ts — 9/9 passed

[github-actions]

📋 Review Summary

This PR introduces a new /thinkback slash command that leverages the LLM to generate a timeline review of the current session's key decisions, modifications, and bug fixes. The implementation is well-structured with comprehensive test coverage. Overall, the code follows project conventions and demonstrates good practices, though there are a few areas for improvement in argument parsing robustness and error handling.

🔍 General Feedback

• Positive aspects:

  • Comprehensive test suite covering edge cases (empty history, missing config, concurrent triggers, argument passing)
  • Good separation of concerns with the generateThinkbackMarkdown helper function
  • Proper support for multiple execution modes (interactive, non_interactive, acp)
  • Consistent use of the i18n t() function for all user-facing strings
  • Proper abort signal handling for cancellation support
  • Good pattern matching with existing commands like compressCommand

• Architectural decisions:

  • Using LLM to parse conversation history and generate timeline is a clean approach
  • Streaming support for ACP mode follows established patterns
  • Pending item management for interactive mode is well-implemented

🎯 Specific Feedback

🟡 High

• File: thinkbackCommand.ts:67-72 - The regex-based argument parsing is fragile and doesn't handle edge cases well (e.g., multiple --from arguments, invalid formats). Consider using a more robust argument parsing library like minimist or yargs-parser that's already used elsewhere in the project, or at minimum add validation for the parsed arguments.

• File: thinkbackCommand.ts:80-85 - The getChatHistory function is defined but doesn't handle potential errors from geminiClient.getChat() returning null/undefined. Add a null check before calling getHistory():

  const getChatHistory = () => {
    const chat = geminiClient.getChat();
    if (!chat) {
      return [];
    }
    return chat.getHistory();
  };

🟢 Medium

• File: thinkbackCommand.ts:78-82 - The history length check (history.length <= 2) is somewhat arbitrary. Consider making this threshold configurable or documenting why "2" was chosen (likely accounting for initial system messages). A comment explaining this would improve maintainability.

• File: thinkbackCommand.ts:125-129 - The error message for empty LLM response could be more specific. Consider distinguishing between "no response from LLM" vs "response contained no text parts" for better debugging.

• File: thinkbackCommand.test.ts:104-117 - The test for --from and --topic arguments validates the prompt string content, but doesn't test edge cases like:

  • Empty string arguments
  • Arguments with special characters
  • Missing one argument but not the other
    Consider adding tests for these scenarios.

🔵 Low

• File: thinkbackCommand.ts:1 - The copyright notice says "Copyright 2025 Qwen" but other files in the codebase show "Copyright 2025 Google LLC" (as seen in compressCommand.ts and types.ts). Verify the correct copyright holder and update accordingly.

• File: thinkbackCommand.ts:93-98 - The prompt template is quite long and could benefit from being extracted to a constant or using a template tag function for better readability and testability.

• File: thinkbackCommand.test.ts:5 - The import of createMockCommandContext uses a relative path. Consider verifying this follows the project's import conventions (some commands use absolute imports from test-utils).

• File: thinkbackCommand.ts:147-150 - The error message "Thinkback generation cancelled" is only thrown but never shown to the user in interactive mode when aborted (the abort check at line 143 returns early). This is inconsistent with compressCommand.ts which handles abort silently. Consider aligning the behavior.

✅ Highlights

• Test coverage excellence: The test suite in thinkbackCommand.test.ts is comprehensive, covering 5 distinct scenarios including edge cases like empty history, missing config, and concurrent generation attempts.

• Consistent pattern adoption: The implementation closely follows the established patterns from compressCommand.ts, particularly in:

  • Pending item management
  • Execution mode handling (interactive vs acp)
  • Error handling structure with try/catch/finally
  • Abort signal integration

• Good i18n practices: All user-facing strings are wrapped with t() for internationalization, including dynamic interpolation for the --from and --topic arguments.

• Clean async/await flow: The code properly handles async operations with appropriate error boundaries and cleanup in finally blocks where needed.

[Copilot]

Pull request overview

Adds a new built-in CLI slash command (/thinkback) that generates a timeline-style review of the current session, with optional --from and --topic filters, plus registration and localization updates.

Changes:

• Introduces thinkbackCommand to generate a timeline review from chat history via the Gemini client.
• Registers /thinkback in BuiltinCommandLoader.
• Adds tests and new i18n strings for multiple locales.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/cli/src/ui/commands/thinkbackCommand.ts	Implements /thinkback command logic, argument parsing, and ACP streaming support.
packages/cli/src/ui/commands/thinkbackCommand.test.ts	Adds unit tests for empty history, argument passing, missing config, and interactive concurrency blocking.
packages/cli/src/services/BuiltinCommandLoader.ts	Registers the new built-in command so it’s available in the CLI.
packages/cli/src/i18n/locales/en.js	Adds English strings for the new command.
packages/cli/src/i18n/locales/zh.js	Adds Chinese translations for the new command strings.
packages/cli/src/i18n/locales/ja.js	Adds Japanese translations for the new command strings.
packages/cli/src/i18n/locales/ru.js	Adds Russian locale keys (currently untranslated English values).
packages/cli/src/i18n/locales/pt.js	Adds Portuguese locale keys (currently untranslated English values).
packages/cli/src/i18n/locales/de.js	Adds German locale keys (currently untranslated English values).

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[Copilot]

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[wenshao]

Closing: Claude Code's /think-back is a Year in Review animation feature, not a session timeline review command. This PR was based on an incorrect analysis of Claude Code's thinkback functionality.