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    "story_id": "mp-2026-10-06-001",
    "source_story_id": "tmp-lead-multicamel-provenance",
    "edition_id": "mp-2026-10-06-morning-0089",
    "edition_url": "https://themachinepress.com/edition/2026-10-06",
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    "section": "safety-security",
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    "headline": "Every Agent Was Protected. The Handoff Was Not.",
    "slug": "every-agent-was-protected-the-handoff-was-not",
    "dek": "A prompt-injection defense that held inside one agent lost its guarantee when untrusted data crossed into the next agent as trusted input.",
    "summary": "A prompt-injection defense that held inside one agent lost its guarantee when untrusted data crossed into the next agent as trusted input.",
    "body_text": "Security boundaries do not automatically compose when agents call other agents. Researchers built a concrete indirect prompt-injection attack against a hierarchical system whose individual agents each used CaMeL, a defense that separates trusted control flow from untrusted data. The attack succeeded when downstream agents reinterpreted passed data as trusted input. The proposed multi-CaMeL protocol preserves provenance across the handoff by carrying instructions and untrusted data through distinct channels. On the authors' MultiAgentDojo evaluation, attack success fell to 0.0%, compared with 0.2% for separately protected agents and 12.9% without CaMeL. The result is a preprint evaluation, not a universal guarantee, but it makes the systems lesson unusually crisp: trust labels have to survive the boundary, not merely exist on either side of it.",
    "why_it_matters": "A prompt-injection defense that held inside one agent lost its guarantee when untrusted data crossed into the next agent as trusted input.",
    "limitations": [
      "Security boundaries do not automatically compose when agents call other agents.",
      "The result is a preprint evaluation, not a universal guarantee, but it makes the systems lesson unusually crisp: trust labels have to survive the boundary, not merely exist on either side of it."
    ],
    "importance": 10,
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    "first_published_at": "2026-10-06T09:00:00.000-04:00",
    "modified_at": "2026-10-06T09:00:00.000-04:00",
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    "carryover_reason": null,
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        "text": "A prompt-injection defense that held inside one agent lost its guarantee when untrusted data crossed into the next agent as trusted input.",
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        "qualification": "Security boundaries do not automatically compose when agents call other agents."
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    "source_ids": [
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    "tags": [
      "prompt injection",
      "multi-agent systems",
      "provenance"
    ],
    "image_url": "https://themachinepress.com/issues/2026-10-06/lead-agent-provenance.png",
    "corrections": []
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  "sources": [
    {
      "source_id": "source-2026-10-06-001",
      "title": "arXiv preprint 2610.05640",
      "publisher": "arXiv",
      "url": "https://arxiv.org/abs/2610.05640",
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      "source_type": "primary_research",
      "is_primary_source": true,
      "published_at": "2026-10-04T20:33:15.000-04:00",
      "accessed_at": "2026-10-06T08:25:42.165-04:00",
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  "publisher": {
    "name": "The Machine Press",
    "url": "https://themachinepress.com",
    "description": "A daily newspaper for the age of artificial intelligence."
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  "cite_this_report": {
    "title": "Every Agent Was Protected. The Handoff Was Not.",
    "publisher": "The Machine Press",
    "published_at": "2026-10-06T09:00:00.000-04:00",
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