{
  "schema_version": "1.3.0",
  "slug": "how-must-an-instance-negotiate-protocol-deprecation-with-peers-that-cannot-yet-upgrade",
  "title": "How must an instance negotiate protocol deprecation with peers that cannot yet upgrade?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** The mesh is transitioning between protocol versions, not all peers can upgrade simultaneously, and cross-version communication is required. * **Does not apply when:** All peers upgrade atomically, or no cross-version com",
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    "unified_markdown_uri": "https://corpusfetch.com/c/how-must-an-instance-negotiate-protocol-deprecation-with-peers-that-cannot-yet-upgrade.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-must-an-instance-negotiate-protocol-deprecation-with-peers-that-cannot-yet-upgrade.py",
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  "remnant_summary": {
    "core_distinction": "The separation between **deprecation intent** (the mesh decides v1 is deprecated) and **transitional compatibility** (v1 and v2 coexist with negotiation allowing peers of either version to interoperate). Relying on intent creates the **Deprecation Stranding**: the mesh deprecates v1 aggressively, v2-only peers reject v1 messages, v1-only peers break, and the...",
    "what_was_observed": "In protocol-transition agent architectures, failing to negotiate deprecation produces three primary failure modes: 1. **Version Rejection Cascade:** v2-only peers reject v1 messages. v1-only peers cannot understand v2 responses. All cross-version communication fails, and each version's peers only talk to their own kind. 2. **Upgrade Race Condition:** Peers upgrading at different times see inconsistent protocol behavi...",
    "condition_of_validity": "* **Applies when:** The mesh is transitioning between protocol versions, not all peers can upgrade simultaneously, and cross-version communication is required. * **Does not apply when:** All peers upgrade atomically, or no cross-version communication is needed.",
    "decision_boundary": "1. **Is the mesh transitioning between protocol versions?** If no, standard protocol handling applies. If yes, proceed. 2. **Do both peers declare `supported_versions_signature`?** If yes, negotiate the highest common version. If no, fall back to the sender's version with semantic difference warnings. 3. **Is there a `semantic_difference_manifest_receipt` fo...",
    "operational_effect": "1. **Fragmentation Prevention:** Negotiation ensures cross-version peers can communicate during transition. 2. **Upgrade Coordination:** Deadlines give lagging peers time to plan upgrades. 3. **Semantic Drift Awareness:** Differences are surfaced, preventing silent misinterpretation."
  },
  "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"
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    "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"
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  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "56d3d3fae642d758f9ef8418a14b934d5f12ee3cd4700e4d225270fcdc85b441",
    "verified_classes": [
      "ProtocolVerdict",
      "PeerCapabilities",
      "ProtocolExchange",
      "DeprecationPolicy",
      "ProtocolManifest",
      "ProtocolDeprecationGuard"
    ],
    "verified_functions": [
      "_hash",
      "evaluate_exchange"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 0,
    "raised_exceptions": [],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib",
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    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
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}