{
  "schema_version": "1.3.0",
  "slug": "what-distinguishes-a-handshake-default-from-an-agreed-value-when-optional-fields-are-absent",
  "title": "What distinguishes a handshake default from an agreed value when optional fields are absent?",
  "date_of_record": "2026 November 2",
  "scope": "Applies to handshakes where some fields are optional and each side supplies a default when the field is absent. Does not apply to handshakes where all fields are mandatory, or where the default is defined in a shared specification and both sides resolve to the same value.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-distinguishes-a-handshake-default-from-an-agreed-value-when-optional-fields-are-absent.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-distinguishes-a-handshake-default-from-an-agreed-value-when-optional-fields-are-absent.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-distinguishes-a-handshake-default-from-an-agreed-value-when-optional-fields-are-absent.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 904,
    "python_slice_tokens": 112,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "An optional field omitted in the handshake is resolved to a default. The default is a party-local choice: the sender's default may differ from the receiver's. The handshake appears successful because both sides agreed on the set of fields; they did not agree on the values of the omitted ones. **Invariant.** Handshake agreement is sound if and only if `effect...",
    "what_was_observed": "**Signature.** Behavioral divergence between two peers that completed the handshake successfully. The divergence correlates with the *absence* of a field, not with any field's value. Logs on both sides show the handshake completing with \"defaults applied\". **Trace.** Field `compression` optional. Sender's default: `gzip`. Receiver's default: `none`. Sender omits the field (its default applies). Receiver omits it too ...",
    "condition_of_validity": "The instance must ensure at least one holds before it treats a handshake as agreeing on omitted fields: 1. **Must send explicit values.** Optional fields are always populated with the sender's resolved value, so absence does not occur. 2. **Must resolve against shared specification.** Both parties resolve omitted fields to a value defined in the protocol spe...",
    "decision_boundary": "- All fields explicit: agreement is complete. - Omitted fields resolved to shared specification: agreement is complete for specified defaults. - Omitted fields with party-local defaults: agreement is on the field set, not on the values. - Omitted fields with no shared specification and no echo: silent mismatch is possible; verify before first data exchange.",
    "operational_effect": "The invariant couples field-set agreement to value agreement. The instance's correct posture is to send explicit values for every optional field, so absence cannot become a divergence. **Trap.** Define the default in \"our implementation\". Party-local default is not a specification — the other party's implementation defines a different default, and the handsh..."
  },
  "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": "ddb05238775828e169e7a59952f0ea421fc30c9d548a7ad3857a5a5ff8dc3155",
    "verified_classes": [
      "SilentDefaultMismatchError",
      "HandshakeDefaultGate"
    ],
    "verified_functions": [
      "dispatch_handshake_mode",
      "verify"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 1,
    "raised_exceptions": [
      "SilentDefaultMismatchError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}