{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-refuse-to-propagate-a-parent-span-context-across-a-federation-boundary",
  "title": "Under what conditions must an instance refuse to propagate a parent span context across a federation boundary",
  "date_of_record": "2026 November 8",
  "scope": "Applies to distributed trace correlation in systems where autonomous agents hand off work to sub-agents and where spans cross administrative federation boundaries (separate trust domains, separate trace backends, or separate tenants). Does not apply to single-domain, single-tenant traces where all spans share one collector and one signing authority.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-propagate-a-parent-span-context-across-a-federation-boundary.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-propagate-a-parent-span-context-across-a-federation-boundary.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-propagate-a-parent-span-context-across-a-federation-boundary.warrant.json"
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  "token_profile": {
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  "remnant_summary": {
    "core_distinction": "There are two distinct things commonly conflated under \"propagating trace context\": 1. **Correlation propagation** — carrying a `trace_id` and a parent `span_id` so that downstream spans can be stitched into the same trace tree. 2. **Authority propagation** — asserting that the downstream span is *causally owned* by the upstream span and therefore inherits i...",
    "what_was_observed": "In a nested handoff chain — orchestrator agent A (federation `alpha`) → planner agent B (federation `beta`) → tool-executor C (federation `gamma`) — we observed the following during a cross-federation incident review: - The `trace_id` propagated correctly through all three hops (W3C `traceparent` header passed verbatim). - The **sampling decision** propagated with it. A's tail-based sampler decided to drop the trace;...",
    "condition_of_validity": "Propagating a parent span context across a federation boundary is valid if and only if all of the following hold: 1. **Trust is explicit, not implied.** The receiving federation has a configured, verifiable trust relationship with the sending federation (mutual TLS with pinned identities, or a signed context envelope). Possession of a `traceparent` string is...",
    "decision_boundary": "The decision to propagate vs. to link-and-root is a function of (a) whether the boundary is a trust boundary and (b) whether the incoming context is fresh and signed. The critical cell is \"cross-federation, unknown peer, fresh & signed-looking.\" A signed-looking context from an unknown peer is exactly the confused-deputy case. The instance must refuse. The e...",
    "operational_effect": "Enforcing this boundary has three concrete effects: - **Trace trees fragment at federation edges.** Downstream federations produce their own roots, linked to upstream via span links rather than parent-child. This is correct: the causal claim is \"related to,\" not \"owned by.\" Dashboards must be taught to follow links, not just parent pointers. - **Sampling bec..."
  },
  "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": "3d43b68947b7c1c7832cce1a6583d88af5a7fa5cea3304c93b92b43f6b4a9dbf",
    "verified_classes": [
      "UntrustedFederationContextError",
      "SpanContext",
      "TrustPolicy"
    ],
    "verified_functions": [
      "decide_propagation",
      "ingest_remote_context",
      "require_trusted_parent"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "UntrustedFederationContextError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "time",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}