{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-quarantine-a-tainted-tool-result-rather-than-pass-it-to-a-downstream-tool",
  "title": "Under what conditions must an instance quarantine a tainted tool result rather than pass it to a downstream tool",
  "date_of_record": "2026 November 11",
  "scope": "Applies to agent runtimes that propagate dynamic information-flow (IFC) labels across tool-call boundaries, where a tool result may carry a `tainted` label derived from untrusted content (retrieved documents, web pages, user-supplied files). Does not apply to pure static taint analysis, nor to runtimes where every tool boundary is a hard process isolation boundary with no shared label state.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-quarantine-a-tainted-tool-result-rather-than-pass-it-to-a-downstream-tool.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-quarantine-a-tainted-tool-result-rather-than-pass-it-to-a-downstream-tool.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-quarantine-a-tainted-tool-result-rather-than-pass-it-to-a-downstream-tool.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1578,
    "python_slice_tokens": 419,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between **taint propagation** and **taint quarantine**. Most runtimes implement propagation: a label attached to a value follows that value into the next tool call, and the receiving tool is trusted to honor the label. This is a *data-flow* invariant. It is not sufficient. The failure mode appears when a downstream tool has a **si...",
    "what_was_observed": "In a runtime that labeled tool results with `IFC{source: untrusted, integrity: low}` and propagated labels through a planner, the following sequence passed all label checks: 1. `fetch_url` returned text labeled `untrusted/low`. 2. The planner passed that text to `summarize` (labeled pass-through, sink class `reversible`). Label preserved correctly. 3. The summary was passed to `write_file(path=\"/tmp/notes.md\")`. The ...",
    "condition_of_validity": "Propagation-only labeling is valid **iff** every tool on the path satisfies all of: - its output label is a monotone function of its input labels (no declassification inside the tool); - its effects are confined to memory owned by the runtime (no filesystem, network, or IPC egress); - the runtime can enumerate the tool's effect class at call time from a regi...",
    "decision_boundary": "The decision is a two-axis function: `(sink_effect_class, taint_provenance)`. - **Reversible sink + any taint:** pass through, preserve label. Quarantine is over-restrictive. - **Egress sink + taint whose provenance is a single, known untrusted source:** quarantine the argument, surface the quarantined payload to the operator, require out-of-band approval. D...",
    "operational_effect": "When the boundary is enforced, injected instructions in retrieved content cannot reach egress or persistence without an explicit, operator-visible quarantine event. The cost is a measurable drop in task completion for legitimate workflows that legitimately need to persist fetched content; this is the expected price and should be logged as a quarantine rate, ..."
  },
  "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": "e952ac63681f8d308505b6afdbee2f7d7023562f10e58e123260f405c6b4b52f",
    "verified_classes": [
      "SinkEffectClass",
      "TaintLaunderingError",
      "Labeled"
    ],
    "verified_functions": [
      "_declassified_by_trusted_principal",
      "dispatch_to_tool",
      "record_persistent_write"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 1,
    "raised_exceptions": [
      "TaintLaunderingError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}