{
  "schema_version": "1.3.0",
  "slug": "when-must-an-agent-emit-a-causal-link-span-before-it-acknowledges-a-federated-parent",
  "title": "When must an agent emit a causal-link span before it acknowledges a federated parent?",
  "date_of_record": "2026 November 6",
  "scope": "Applies to agents that participate in federated trace graphs where spans from multiple trust domains are stitched via causal-link tokens (e.g., W3C `traceparent` plus vendor link attributes). Does not apply to single-domain tracing where all spans share one collector and one clock authority.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-agent-emit-a-causal-link-span-before-it-acknowledges-a-federated-parent.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-agent-emit-a-causal-link-span-before-it-acknowledges-a-federated-parent.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-agent-emit-a-causal-link-span-before-it-acknowledges-a-federated-parent.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 861,
    "python_slice_tokens": 157,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "A *parent-child* edge is a claim about causality enforced at span emission time by a single writer. A *causal-link* edge is a claim about causality asserted *after the fact* by a third party reading two independently-emitted spans. The non-obvious failure is that federated agents frequently satisfy the first invariant (they emit a parent span) while violatin...",
    "what_was_observed": "During a multi-agent handoff (planner → retriever → synthesizer across three trust domains), the synthesizer acknowledged task completion to its caller before its causal-link record was flushed to the shared link store. Under normal load the flush completed in ~40 ms and the link resolved. Under a retriever stall, the synthesizer's link write was queued behind a backpressured exporter and the acknowledgment propagate...",
    "condition_of_validity": "The acknowledgment-before-link invariant holds only if the causal-link record is durable (fsynced or acknowledged by the link store) in the same linearization point as the task-completion acknowledgment. If the link store is eventually consistent, or if the exporter applies backpressure, the invariant is void. A second condition: the link token must be minte...",
    "decision_boundary": "Emit-and-acknowledge atomically when: (a) the link store returns a durable write receipt, and (b) the child minted its own link token bound to the parent's span ID. Otherwise, acknowledge *provisionally* and mark the span `link_pending` so the federated viewer treats reachability as unknown rather than absent. The boundary is not \"did I emit a span\" but \"is ...",
    "operational_effect": "Agents that cross this boundary produce ghost completions that pass local health checks and fail federated reachability alerts — the worst combination, because the failure is invisible to the component that caused it. Enforcing the atomicity check converts silent orphaning into an explicit `LinkNotDurableError`, which upstream planners can retry or escalate...."
  },
  "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": "12b06b059b07b73d143e9abb37756de041bb8b6ff6fbacff6b69374c0f0ca8a3",
    "verified_classes": [
      "LinkNotDurableError",
      "LinkReceipt"
    ],
    "verified_functions": [
      "acknowledge_with_causal_link"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "LinkNotDurableError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "time"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}