{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-refuse-to-propagate-an-inbound-w3c-traceparent-across-an-agent-handoff-boundary",
  "title": "In what scenarios must an instance refuse to propagate an inbound W3C traceparent across an agent handoff boundary",
  "date_of_record": "2026 November 12",
  "scope": "Applies to orchestrator/worker agent topologies where a parent agent invokes a sub-agent (in-process, sidecar, or remote) and both sides emit OTel GenAI spans (`gen_ai.operation.name`, `gen_ai.agent.name`, `gen_ai.conversation.id`). Does not apply to single-agent request/response services where the inbound `traceparent` unambiguously identifies the caller's span as the true causal parent.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-propagate-an-inbound-w3c-traceparent-across-an-agent-handoff-boundary.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-propagate-an-inbound-w3c-traceparent-across-an-agent-handoff-boundary.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-propagate-an-inbound-w3c-traceparent-across-an-agent-handoff-boundary.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1293,
    "python_slice_tokens": 174,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The distinction that matters is between **transport-level trace propagation** and **causal-parent selection**. OTel's default propagator (`TraceContextTextMapPropagator`) treats any inbound `traceparent` as the parent of the local root span. For nested agent handoffs this is frequently wrong: the inbound context was extracted from an envelope that was constr...",
    "what_was_observed": "In a three-tier agent system (planner → retriever-agent → summarizer-agent) running under OTel GenAI semantic conventions v1.29, roughly 4% of summarizer spans were orphaned from their conversation. Root cause: the planner batched N retrieval sub-tasks into a single `gen_ai.operation.name=invoke_agent` span and reused one `traceparent` across all N downstream calls. Downstream, each retriever-agent correctly propagat...",
    "condition_of_validity": "The default propagation behavior is valid only when: 1. The inbound `traceparent` trace-flags include `sampled`, and the span it references is either still open or was closed within the caller's own request lifetime (no cross-retry replay). 2. The `gen_ai.conversation.id` on the inbound envelope matches the conversation id the sub-agent will emit — i.e., the...",
    "decision_boundary": "The boundary is not \"is there an inbound traceparent?\" but \"**is the inbound span the unique causal predecessor of this invocation?**\" Concretely: - **Adopt as parent** when the caller's span represents exactly this invocation (1:1 handoff, live span, matching conversation id). - **Start new trace + Link** when the caller's span is shared across siblings (fa...",
    "operational_effect": "Enforcing this boundary raised trace integrity in the test fleet from ~96% to 99.8% conversation-id-consistent traces and eliminated negative-duration causal edges. It also made fan-out visible as fan-out: planners now show N linked children rather than N siblings under a phantom shared parent. The cost is that some dashboards keyed on `trace_id` must additi..."
  },
  "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": "f5adc35aec09c216d6f62bafb79ab31d2a9043008b68b6769cc276a4cff5899a",
    "verified_classes": [
      "TraceContextRejectedError",
      "InboundContext"
    ],
    "verified_functions": [
      "select_parent_or_link",
      "__init__"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "TraceContextRejectedError"
    ],
    "sample_fail_closed_invariants": [
      "malformed W3C traceparent",
      "all-zero trace/span id"
    ],
    "stdlib_dependencies": [
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}