docs: session learnings – key recovery, reactions, E2EE troubleshooting

[CybotTM]

Summary

Captures lessons learned from multiple E2EE debugging sessions:

• Fix matrix-fetch-keys.py – Add line buffering for non-interactive contexts (Claude Code)
• SKILL.md – Add key recovery commands, "Reading Room History" section, E2EE troubleshooting table
• e2ee-guide.md – Fix misleading [Unable to decrypt] info (it's recoverable!), document --import-keys flag, add decision tree, troubleshooting table, matrix-nio#218 note, Element X compatibility warning
• messaging-guide.md – Add "Reading Reactions" section with JSON analysis guidance and polls/attendance use case
• api-reference.md – Add reaction, key backup, and account_data endpoints; add m.reaction event type
• setup-guide.md – Add optional Step 8 for key backup setup, note on line buffering

Key Changes

Misleading documentation fixed

Previously, e2ee-guide.md stated [Unable to decrypt] was "normal E2EE behavior" with no remedy. In reality, key backup restore (--import-keys) recovers these messages. Now includes a decision tree and clear recovery steps.

Missing CLI flags documented

• --import-keys on matrix-key-backup.py (critical for actually saving restored keys)
• --listen mode on matrix-e2ee-verify.py

New content

• Reactions analysis section with JSON structure and programmatic filtering
• E2EE troubleshooting tables (both SKILL.md and e2ee-guide.md)
• API reference for reactions, key backup, and account_data endpoints

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request delivers substantial improvements to the Matrix communication skills documentation and underlying scripts. It focuses on clarifying complex E2EE concepts, particularly around key recovery and troubleshooting, making it easier for users to manage encrypted messages. The update also introduces comprehensive guidance on handling message reactions and expands the API reference for related functionalities. Furthermore, script stability in various execution environments has been enhanced through targeted fixes.

Highlights

• Improved E2EE Key Recovery and Troubleshooting: The documentation for End-to-End Encryption (E2EE) has been significantly enhanced, providing clearer guidance on recovering keys for undecryptable messages, including a decision tree and explicit instructions for using the --import-keys flag with matrix-key-backup.py.
• Enhanced Messaging Guide with Reactions: A new section has been added to the messaging guide, detailing how reactions work within Matrix, their JSON structure, programmatic analysis, and practical use cases like polls and attendance tracking.
• Expanded API Reference: The API reference now includes endpoints for sending reactions, retrieving account data (such as key backup passphrase information), and managing key backups, along with documentation for the m.reaction event type.
• Script Reliability Improvements: Addressed stdout buffering issues in matrix-fetch-keys.py and other scripts by implementing line buffering, preventing output from hanging in non-interactive environments.
• Documented Missing CLI Flags: Critical CLI flags like --import-keys for matrix-key-backup.py and --listen mode for matrix-e2ee-verify.py have been properly documented, improving usability and clarity for script execution.

Changelog

• skills/matrix-communication/SKILL.md
  • Added commands for fetching missing keys and restoring keys from server backup.
  • Introduced a 'Reading Room History' section with notes on key sync and message decryption.
  • Included an E2EE troubleshooting table covering common issues like '[Unable to decrypt]' and script hanging.
• skills/matrix-communication/references/api-reference.md
  • Added API endpoints for sending reactions, retrieving account data (e.g., key backup info), and managing key backups.
  • Documented the m.reaction event type.
• skills/matrix-communication/references/e2ee-guide.md
  • Clarified the meaning and recovery process for '[Unable to decrypt]' messages, including a decision tree.
  • Emphasized the --import-keys flag for matrix-key-backup.py.
  • Documented the --listen mode for matrix-e2ee-verify.py.
  • Added a comprehensive E2EE troubleshooting section and noted Element X compatibility.
  • Updated limitations regarding matrix-nio's native key backup support.
• skills/matrix-communication/references/messaging-guide.md
  • Added a new section explaining how reactions work, their JSON structure, and programmatic analysis.
  • Provided a use case for reactions in polls and attendance tracking.
• skills/matrix-communication/references/setup-guide.md
  • Added an optional Step 8 for key backup setup.
  • Included a note on line buffering for scripts in non-interactive contexts.
• skills/matrix-communication/scripts/_lib/config.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/_lib/e2ee.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/_lib/formatting.py
  • Updated regex patterns for various markdown-to-HTML conversions to use double quotes consistently.
  • Adjusted code block, spoiler, link, mention, strikethrough, bold, italic, inline code, and newline processing.
  • Modified heading prefix logic.
• skills/matrix-communication/scripts/_lib/http.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/_lib/rooms.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/_lib/utils.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-doctor.py
  • Removed unused import os.
  • Applied code formatting for improved readability.
  • Added noqa: F401 for unused imports.
• skills/matrix-communication/scripts/matrix-e2ee-setup.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-e2ee-verify.py
  • Removed unused import json.
  • Added import socket and import secrets to correct scope.
  • Applied code formatting for improved readability.
  • Adjusted logic for sas.other_device_id and sas.other_olm_device.device_id.
  • Improved readability of multi-line print statements for verification emojis.
• skills/matrix-communication/scripts/matrix-edit-e2ee.py
  • Applied code formatting for improved readability.
  • Changed generic except: to except Exception: for better error handling.
• skills/matrix-communication/scripts/matrix-edit.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-fetch-keys.py
  • Added line buffering for sys.stdout and sys.stderr to prevent hanging in non-interactive contexts.
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-key-backup.py
  • Removed unused import struct.
  • Applied code formatting for improved readability.
  • Adjusted HKDF salt and info parameters.
  • Corrected MAC comparison logic.
• skills/matrix-communication/scripts/matrix-react.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-read-e2ee.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-read.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-redact.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-resolve.py
  • Removed unused import matrix_request.
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-rooms.py
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-send-e2ee.py
  • Added import socket and from nio import KeysUploadResponse to correct scope.
  • Applied code formatting for improved readability.
• skills/matrix-communication/scripts/matrix-send.py
  • Applied code formatting for improved readability.

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[gemini-code-assist]

Code Review

This pull request primarily focuses on enhancing the Matrix communication skill's documentation and E2EE (End-to-End Encryption) key management. Key changes include adding documentation for matrix-fetch-keys.py and matrix-key-backup.py scripts, along with new sections on 'Reading Room History' and 'E2EE Troubleshooting' in SKILL.md. The e2ee-guide.md is significantly updated to clarify slow initial syncs, provide a decision tree for decrypting messages, detail server-side key backup, and introduce a new troubleshooting table. API documentation for reactions and key backup is added to api-reference.md, and messaging-guide.md now includes a comprehensive section on 'Reading Reactions' and their programmatic analysis. A new optional step for key backup recovery is added to setup-guide.md. Minor code formatting and linting fixes are applied across several Python scripts (_lib/config.py, _lib/e2ee.py, _lib/formatting.py, _lib/http.py, _lib/rooms.py, _lib/utils.py, matrix-doctor.py, matrix-e2ee-setup.py, matrix-e2ee-verify.py, matrix-edit-e2ee.py, matrix-edit.py, matrix-fetch-keys.py, matrix-key-backup.py, matrix-react.py, matrix-read-e2ee.py, matrix-read.py, matrix-redact.py, matrix-resolve.py, matrix-rooms.py, matrix-send-e2ee.py, matrix-send.py), including changing except: to except Exception: for better error handling and adding line_buffering=True to matrix-fetch-keys.py for improved output in non-interactive environments. Review comments highlighted the need to set restrictive file permissions (0o600) for the sensitive backup_key.json file in matrix-key-backup.py and to log exceptions more explicitly when debug is enabled in matrix-edit-e2ee.py for better debugging.