{
  "schema_version": "1.3.0",
  "slug": "what-fallback-triggers-must-be-logged-after-an-upstream-service-degrades-gracefully",
  "title": "What fallback triggers must be logged after an upstream service degrades gracefully?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** The upstream service implements a graceful degradation pattern (returning 2xx responses with degraded content) and a successor instance will consume that content or interact with the same upstream service. * **Does not a",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-fallback-triggers-must-be-logged-after-an-upstream-service-degrades-gracefully.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-fallback-triggers-must-be-logged-after-an-upstream-service-degrades-gracefully.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-fallback-triggers-must-be-logged-after-an-upstream-service-degrades-gracefully.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1201,
    "python_slice_tokens": 311,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The separation between **transient fallback execution** (the degraded response actually consumed during the session, such as a stale cache hit or a default empty array) and the **fallback trigger boundary** (the exact threshold, circuit breaker state, or error rate that caused the service to switch from primary to fallback mode). A transient fallback masks t...",
    "what_was_observed": "In distributed agent architectures, failing to log fallback triggers after graceful degradation produces three primary failure modes: 1. **Silent Stale Data Ingestion:** An API serves a cached response from 72 hours ago because its primary database is down. The instance ingests the stale data as fresh, failing to log that the primary path is degraded and the cache TTL was exceeded. 2. **Circuit Breaker Blindness:** A...",
    "condition_of_validity": "* **Applies when:** The upstream service implements a graceful degradation pattern (returning 2xx responses with degraded content) and a successor instance will consume that content or interact with the same upstream service. * **Does not apply when:** The upstream service fails explicitly with an error code (allowing standard retry logic), or the fallback p...",
    "decision_boundary": "1. **Did the session consume a degraded or fallback response (e.g., stale cache, partial payload, default value)?** If no, standard state persistence applies. If yes, proceed to log the trigger. 2. **Is the exact `fallback_trigger_metric` identifiable?** If no, the fallback is indistinguishable from primary data, and the instance must flag the entire dataset...",
    "operational_effect": "1. **Degradation Transparency:** Exposes hidden fallbacks, preventing successors from treating stale or partial data as verified ground truth. 2. **Thundering Herd Prevention:** Prevents successors from hammering a recovering upstream service by enforcing the circuit breaker cooldown epoch. 3. **Deterministic Recovery:** Replaces blind retries with an explic..."
  },
  "matched_failure_symptoms": [
    "HTTP_502_503_504_CASCADE"
  ],
  "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": "262d926c9be60aafc1135b53d504b65b3286609d54308db19b79405d56e33eb4",
    "verified_classes": [
      "FallbackTrigger",
      "DegradedState",
      "DegradationEvent",
      "DegradationManifest",
      "CurrentTimeContext",
      "GracefulDegradationLogger"
    ],
    "verified_functions": [
      "_hash",
      "seal_manifest",
      "verify_primary_path_readiness"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "ValueError"
    ],
    "sample_fail_closed_invariants": [
      "Upstream service ID is required to log a fallback trigger.",
      "A health predicate is mandatory; successors must be able to confirm primary-path recovery.",
      "Circuit breaker cooldown epoch must be a positive timestamp."
    ],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib",
      "json",
      "time"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}