I am acting as the control policy of the reasoning engine, choosing verbs freely from the v1 library and calling the encyclopedia tools to anchor the decision. I chose **Approach B (verb-driven)**: drive from the verb library, but use only the verbs that earn their place, stopping when the decision is sound.

# Working

## Verb: match (retrieve)
Anchored the problem to the catalog two ways.

- `search_prime` (semantic, meta-model query): "a critical function depends on a single component whose failure is catastrophic; choose between adding an independent parallel path versus hardening the single component." Top structural hits: **systemic_risk**, **critical_mass / threshold_and_criticality** (single-point criticality), **redundancy**, **functional_redundancy_degeneracy**, **antifragility**, plus **FMEA** (mixed-framed).
- `search_by_facets` over five facets of the problem. The per-facet rankings are the load-bearing read here:
  - "single point whose failure brings down the whole" → systemic_risk, FMEA, threshold_and_criticality
  - "surviving failure by having an independent backup path" → **fault_tolerance (0.70)**, **redundancy (0.68)**, fail_safe
  - "improving reliability of one element under a fixed budget" → margin_of_safety, refinement, **redundancy** (note: even the *hardening* facet surfaces redundancy near the top)
  - "correlated failure when paths share a common cause" → **confounding**, FMEA, **systemic_risk**, correlation
  - "diversity reduces the chance all paths fail at once" → diversity, requisite_variety, risk_pooling
  - Fused (RRF): FMEA, systemic_risk, **redundancy**, fault_tolerance.

Post satisfied: ≥1 candidate with recorded source-prime overlap. Candidates with overlap: {redundancy, fault_tolerance, systemic_risk, margin_of_safety, FMEA}.

## Verb: salience-rank
Order by load-bearing relevance (would removing it change the recommendation?).

- **fault_tolerance — load_bearing.** Names the actual goal: continue acceptable service *in the presence of* component failure, "no single point of failure." It is the property; the choice is which mechanism achieves it.
- **redundancy — load_bearing.** Supplies the mechanism (independent alternate path) and the decisive math: under independence, simultaneous-failure probability shrinks as the *product* of individual failure probabilities; a single component cannot reach that regime no matter how hard it is hardened.
- **systemic_risk — load_bearing (the guard).** Warns that the redundant path is only worth its cost if the two paths fail *independently*; shared/common-cause dependencies (power, code, vendor, operator) defeat redundancy. This is what makes the choice non-trivial and shapes *how* A must be built.
- **margin_of_safety — context.** This is the structural core of Approach B (absorb more demand / harden the one component). Useful as the foil but not the recommendation.
- **FMEA / critical_mass — context.** Framing/analysis aids, not the deciding factor.

Post satisfied: each tagged with rationale.

## Verb: prune
Kept the operative subset {fault_tolerance, redundancy, systemic_risk, margin_of_safety}. Cut critical_mass, antifragility, FMEA, requisite_variety, confounding as not load-bearing for a binary fund-A-or-B call (each cut: either an analysis lens or a near-synonym already represented by the kept set).

## Verb: get_prime (deepen the load-bearing primes)
Pulled redundancy, fault_tolerance, systemic_risk in full.

- **redundancy.** "Any single component has non-zero failure probability… the probability of simultaneous independent failure of N components is the product of individual probabilities (shrinking exponentially in N under independence)." Hardening reduces one factor; it never makes the product structure exist. Crucially: redundancy is "not the same as margin_of_safety — where margin absorbs demand variation above a single component's capability, redundancy handles component failure through alternate pathways." Approach B is margin; Approach A is redundancy. Only redundancy removes the single point.
- **fault_tolerance.** "Robust systems must be designed so that *individual* failures do not produce *system-level* failures, typically by ensuring no single point of failure." That sentence *is* the stated success criterion. It also flags T1 (correlated failures defeat redundancy) and T6 (single point of failure in the detection/failover path) — design caveats for A, not reasons to pick B.
- **systemic_risk.** The single component is a too-connected-to-fail node; risk lives in the dependency on it. But it also supplies the over-lift guard: a redundant path that shares a common cause is "not redundancy." So A must be built as an *independent* path (diverse implementation, separate power/network/vendor/operator), or it collapses back into a single point with extra cost.

## Verb: evaluate-fit (gate the two approaches against the success criterion)
Success criterion is conjunctive and the first clause is absolute: **"No single failure may take down the critical capability" AND "the budget must be used effectively."**

- **Approach B (harden the one component).** Anti-signature: a single component retains non-zero failure probability for *some* failure mode (defect, wear, bit-flip, human error, the very fire/outage that motivates the question). Hardening lowers the probability but cannot drive it to zero, so a single failure *can still* take down the capability. → **Trips the disqualifying condition (first clause is violated as a matter of structure, not degree). DROP.**
- **Approach A (independent second path).** Does not trip the disqualifier *provided* the second path is genuinely independent: with two independent paths the capability survives any single failure (no single point remains). Residual risks are correlated/common-cause failure and a single-point failover/detection path — these are design obligations (diversify dependencies, make failover itself redundant), not disqualifiers. The fixed budget is "used effectively" because it buys the only outcome that satisfies the absolute clause; spending it all on B buys an outcome that cannot satisfy it. → **KEEP.**

Post satisfied: each anti-signature explicitly evaluated with reason; B dropped as disqualified.

## Decision check (no reconcile needed)
The concrete model and the domain-stripped meta-model agree rather than diverge: "make one node un-failable" is unreachable (every node has a failure mode), whereas "no single node's failure is fatal" is reachable only by an independent alternate path. The two readings converge on A, so a reconcile step would be decorative here. Decision is sound — **STOP.**

# Recommendation
Fund **Approach A**: build a second, independent path. Spend the budget first on making the two paths fail-independently (different implementation/supplier/power/network/operator) and on a trustworthy, itself-redundant failover/detection mechanism — because an alternate path that shares a common cause, or a single failover controller, silently recreates the single point of failure.

===DECISION_BEGIN===
DECISIVE_FACTOR: The success criterion forbids any single failure from taking down the capability, and no amount of hardening can drive a single component's failure probability to zero, so only an independent second path can meet that absolute requirement.
CHOICE: A
JUSTIFICATION: A single component, however well-built, always retains some way to fail, so pouring the whole budget into it leaves the capability exposed to that one failure. Building a separate, independent path means no single failure can take everything down, which is exactly what is required. The money is best spent ensuring the two paths do not share hidden common weaknesses (power, design, supplier, operator) and that the switchover between them is itself trustworthy. That is the only spending plan that actually satisfies the stated goal.
===DECISION_END===
