mail-threading 0.1.1

JWZ email threading (RFC 5256). Reconstruct message threads from References/In-Reply-To headers, with subject fallback for broken clients.
Documentation 
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{
  "name": "subject-forward-wrapper-normalization",
  "description": "The RFC 5256 [fwd: subject] wrapper is removed during subject fallback.",
  "spec": {
    "source": "RFC 5256",
    "url": "https://www.rfc-editor.org/rfc/rfc5256",
    "behavior": "base subject extraction removes forward header/trailer wrappers"
  },
  "input": [
    {
      "id": "topic",
      "message_id": "<fwd-wrapper-topic@example>",
      "in_reply_to": null,
      "references": [],
      "subject": "Wrapped Topic",
      "date": "2026-05-15T09:00:00Z"
    },
    {
      "id": "wrapped",
      "message_id": "<fwd-wrapper-forward@example>",
      "in_reply_to": null,
      "references": [],
      "subject": "[Fwd: Wrapped Topic]",
      "date": "2026-05-15T09:05:00Z"
    }
  ],
  "expected": {
    "threads": [
      {
        "root": "topic",
        "messages": [
          "topic",
          "wrapped"
        ]
      }
    ]
  }
}