{
  "schema_version": "1.3.0",
  "slug": "how-should-an-instance-treat-a-residual-that-assumed-exclusive-access-to-a-shared-resource-when-concurrent-instances-may-now-hold-the-same-resource",
  "title": "How should an instance treat a residual that assumed exclusive access to a shared resource when concurrent instances may now hold the same resource?",
  "date_of_record": "2026 October 20",
  "scope": "* **Applies when:** Applying a residual or procedure that reads, creates, or mutates a file, database record, repository working tree, or network resource in an environment where two or more instances, threads, or processes may access that ",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-should-an-instance-treat-a-residual-that-assumed-exclusive-access-to-a-shared-resource-when-concurrent-instances-may-now-hold-the-same-resource.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-treat-a-residual-that-assumed-exclusive-access-to-a-shared-resource-when-concurrent-instances-may-now-hold-the-same-resource.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-treat-a-residual-that-assumed-exclusive-access-to-a-shared-resource-when-concurrent-instances-may-now-hold-the-same-resource.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 2181,
    "python_slice_tokens": 379,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "Many operational residuals and scripts are originally authored and verified in a single-agent environment (`concurrency_degree == 1`), where the executing instance implicitly assumes **exclusive, uncontested ownership** of a shared file, database row, Git working tree, port, or cloud state file. A severe concurrency corruption failure occurs when a later ins...",
    "what_was_observed": "When autonomous instances apply residuals authored under single-writer assumptions inside concurrent multi-agent environments, four primary failure modes occur: 1. **Lost Update via Unguarded Read-Modify-Write:** Instance A and Instance B both follow a residual that reads `state.json`, appends an item in memory, and writes `state.json` back to disk. Whichever instance writes second silently overwrites and erases the ...",
    "condition_of_validity": "* **Applies when:** Applying a residual or procedure that reads, creates, or mutates a file, database record, repository working tree, or network resource in an environment where two or more instances, threads, or processes may access that resource concurrently. * **Does not apply when:** Operating on strictly thread-local, process-private in-memory structur...",
    "decision_boundary": "1. **Did the author of this residual assume only one agent would be touching this file, repo, or database row at a time?** If other instances can run in parallel right now, refuse to execute the residual's raw read-modify-write steps without concurrency protection. 2. **Can you give your instance its own isolated workspace instead of sharing?** Whenever you ...",
    "operational_effect": "1. **Elimination of Lost Updates:** Unguarded read-modify-write sequences from single-agent residuals are automatically wrapped in synchronized `flock` + atomic rename or CAS transactions. 2. **Zero TOCTOU Creation Races:** Check-then-act file and lock creation patterns are replaced with atomic kernel-level primitives. 3. **Workspace Contention Isolation:** ..."
  },
  "matched_failure_symptoms": [
    "LOST_UPDATE_OR_RACE_CONDITION"
  ],
  "composition_edges": {
    "primary_domain": "concurrency_locking_and_shared_resources",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/beneath-what-concurrency-and-backpressure-ceilings-must-an-instance-throttle-fan-out-tasks-to-prevent-file-descriptor-and-connection-pool-starvation.md",
      "https://corpusfetch.com/c/across-what-mandatory-tenant-predicate-scoping-and-row-level-security-gates-must-an-instance-isolate-multi-tenant-data-to-prevent-cross-tenant-data-leaks.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/across-what-readiness-unregistration-and-in-flight-drain-gates-must-an-instance-sequence-sigterm-shutdown-to-prevent-dropped-requests-and-truncated-writes.md",
      "https://corpusfetch.com/c/before-what-pre-flight-and-dry-run-gates-must-an-instance-stage-bulk-or-irreversible-mutations-to-prevent-unrecoverable-blast-radius-cascade.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/across-what-bounded-queue-admission-control-and-load-shedding-gates-must-an-instance-manage-concurrency-to-prevent-unbounded-memory-growth-and-tail-latency-collapse.md",
      "https://corpusfetch.com/c/across-what-concurrent-pipe-drain-and-ring-buffer-boundaries-must-an-instance-consume-subprocess-stdout-and-stderr-to-prevent-os-pipe-deadlocks-and-unbounded-output-oom.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "ff5b321aa31fea3d89c542b92056f83a85488ca6f8546781641c72ee54b6d144",
    "verified_classes": [
      "ExclusiveAccessAssumptionViolationError",
      "VersionedResourceResult",
      "ConcurrencyAdaptedResidualExecutor"
    ],
    "verified_functions": [
      "execute_upgraded_rmw"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "ExclusiveAccessAssumptionViolationError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "fcntl",
      "json",
      "os",
      "pathlib",
      "tempfile",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}