{
  "schema_version": "1.3.0",
  "slug": "what-multicast-fanout-invariants-must-survive-heterogeneous-receiver-capabilities",
  "title": "What multicast fan-out invariants must survive heterogeneous receiver capabilities?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** Messages are sent to multiple receivers, receiver capabilities vary, and sender needs delivery certainty. * **Does not apply when:** Receivers are homogeneous, or fan-out is strictly best-effort (no delivery certainty ne",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-multicast-fanout-invariants-must-survive-heterogeneous-receiver-capabilities.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-multicast-fanout-invariants-must-survive-heterogeneous-receiver-capabilities.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-multicast-fanout-invariants-must-survive-heterogeneous-receiver-capabilities.warrant.json"
  },
  "token_profile": {
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    "python_slice_tokens": 367,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The separation between **fan-out transmission** (the message is sent to all receivers) and **fan-out delivery** (each receiver successfully processes the message). Relying on transmission creates the **Heterogeneous Fanout Degradation**: receivers with weaker capabilities cannot process the message at the speed or format the sender provided, causing some to ...",
    "what_was_observed": "In heterogeneous fan-out architectures, failing to account for receiver capability variance produces three primary failure modes: 1. **Buffer Overflow Slaughter:** The sender fans out to 100 receivers. 20 have small buffers and cannot accept the full message. Their transports drop the message silently, and the sender thinks all 100 received. 2. **Protocol Version Rejection:** The message is sent in v2 format. Half th...",
    "condition_of_validity": "* **Applies when:** Messages are sent to multiple receivers, receiver capabilities vary, and sender needs delivery certainty. * **Does not apply when:** Receivers are homogeneous, or fan-out is strictly best-effort (no delivery certainty needed).",
    "decision_boundary": "1. **Is the fan-out to heterogeneous receivers?** If no, standard multicast applies. If yes, proceed. 2. **Is the `receiver_capability_registry_receipt` current?** If yes, use it to choose encoding and chunking. If no, assume worst-case capabilities. 3. **Is `capability_aware_encoding_signature` applied?** If yes, encoding matches receivers. If no, the messa...",
    "operational_effect": "1. **Delivery Certainty:** Per-receiver receipts distinguish transmission from delivery. 2. **Capability Matching:** Encoding adapts to receiver capabilities. 3. **Slow Receiver Isolation:** Completion threshold prevents one slow receiver from blocking the fan-out."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "2ddef0fae571078714339022addcc332b4b119dd3dc4da94c2f04ba2ed671a3c",
    "verified_classes": [
      "FanoutVerdict",
      "Receiver",
      "FanoutMessage",
      "FanoutPolicy",
      "FanoutManifest",
      "MulticastHeterogeneousGuard"
    ],
    "verified_functions": [
      "_hash",
      "evaluate_fanout"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 0,
    "raised_exceptions": [],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib",
      "json"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}