{
  "schema_version": "1.3.0",
  "slug": "when-does-a-minor-version-bump-break-a-parser-that-claims-forward-compatibility",
  "title": "When does a minor version bump break a parser that claims forward compatibility?",
  "date_of_record": "2026 November 1",
  "scope": "Applies to parsers and consumers that read versioned payloads under a semver or semver-like contract where minor bumps are promised backward compatible. Excludes strict schema validators that intentionally reject unknown fields.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-does-a-minor-version-bump-break-a-parser-that-claims-forward-compatibility.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-does-a-minor-version-bump-break-a-parser-that-claims-forward-compatibility.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-does-a-minor-version-bump-break-a-parser-that-claims-forward-compatibility.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 855,
    "python_slice_tokens": 130,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "**Predicate.** A consumer is forward compatible within a major version if and only if it ignores unknown fields, accepts any minor greater than or equal to the minor it was built against, and does not validate exhaustively. A parser that pins the exact minor, or that treats unknown fields as errors, is not forward compatible regardless of what the contract p...",
    "what_was_observed": "**Signature.** Consumer error rate rising immediately after a producer deploy, with errors naming unknown fields. The producer reports 100 percent success. Rollback of the consumer fixes it, which misidentifies the consumer as the faulty component. **Trace.** Producer at 1.4.0 emits field region. Consumer built against 1.3.x validates with additionalProperties false. Every payload is rejected. Consumer availability d...",
    "condition_of_validity": "A consumer is compatible with future minors only while all hold: 1. **Lenient parsing.** Unknown fields are ignored rather than rejected. 2. **Range acceptance.** The version check accepts any minor greater than or equal to the built version, not an exact match. 3. **Required-field discipline.** Only fields the consumer genuinely requires are marked required...",
    "decision_boundary": "- Lenient parse plus range acceptance: forward compatible within the major version. - Strict parse with exact version pin: compatible only with the exact minor it was built against. Any bump breaks it. - Lenient parse with exact pin: rejects a version it could have handled. The pin, not the parser, is the defect. - Required field added in a minor bump: a con...",
    "operational_effect": "The invariant is a property of the consumer's parsing posture, which is usually written once and never revisited, while the producer's version advances continuously. Remediation is to make parsing lenient and version checks range-based. The trap is to coordinate deploys so the consumer ships first. That works for the next bump and fails for the one after, wh..."
  },
  "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": "f8b6f46ea98d49d5ba7a437f58c7a9d794b0c91c007d7556389464b1ef249131",
    "verified_classes": [
      "VersionCompatibilityError",
      "ParserGate"
    ],
    "verified_functions": [
      "dispatch_parse_mode",
      "verify"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "VersionCompatibilityError"
    ],
    "sample_fail_closed_invariants": [
      "parser rejects unknown fields: not forward compatible"
    ],
    "stdlib_dependencies": [
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}