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Nabla-X LegacySense

Forty-year-old logic, explained in plain English before you touch it.

Turns the explainability engine on old code instead of models or agents: reads a decades-old system, explains what it actually does and why, and produces a dependency map before anyone attempts a migration. Roughly 220 billion lines of COBOL still run production systems in banking, government, and healthcare — and the average COBOL programmer is 55, with about a tenth of that workforce retiring every year.

Illustrative output — target output, not a real run
InputCOBOL batch job, 4,200 lines, last modified 1997, no remaining documentation
Plain-English SummaryCalculates end-of-month interest accrual for savings accounts, applies penalty rules for early withdrawal
Dependency MapReads from 3 upstream files, writes to 2 downstream systems including the nightly settlement batch
Migration Risk FlagPenalty-rule logic branches on a hardcoded date range — likely needs manual review before migration

Core Capabilities

Plain-English Code Explanation

Reads decades-old systems and explains what they actually do, not just what the code syntactically says.

Dependency Mapping

Produces a map of what a legacy system reads from and writes to before anyone attempts to touch it.

Migration Risk Flagging

Surfaces the specific logic most likely to break or need manual review during a migration attempt.

How LegacySense Would Work

Planned design — this pipeline does not exist yet.

1. Ingest Legacy Source Code

Reads a legacy codebase — COBOL and similar decades-old systems are the named starting point.

2. Explain What It Actually Does

Applies Decision Intelligence's explainability approach to code instead of model decisions, producing a plain-English summary.

3. Map Dependencies and Flag Risk

Documents upstream/downstream dependencies and flags logic most likely to need careful handling during migration.

Dependency Map, Built Incrementally

Concept — not yet built

Routine by routine, as LegacySense reads more of a codebase, the map fills in.

BILLING.CBLExplainedRATE-TABLE.CPYExplainedLEDGER-POST.CBLExplainedCUST-LOOKUP.CBLUnmappedAUDIT-TRAIL.CPYUnmappedREPORT-GEN.CBLUnmapped

Illustrative shape of the output only. No codebase has been mapped — the map, the explanations, and the "explained / unmapped" states shown here are a design target, not a screenshot.

How LegacySense Would Think

The reasoning approach this concept is designed around — a path from cryptic code to a plain-English read, one step at a time.

Concept only — no reasoning path has been built or tested.

WS-CALC-01→the interest-calculation subroutine

Explainability Applied to Code, Not Models

The core reframing: the same 'why did this happen' approach Decision Intelligence applies to model decisions, applied to what a legacy system's logic actually does.

•Same underlying approach, different subject matter
PERFORM UNTIL WS-EOF→a named, verifiable pressure — not a hunch

Grounded in a Real, Named Problem

Points to a specific, verifiable pressure: a large volume of COBOL still runs production systems, and the workforce that understands it is aging out.

•Named problem with real workforce and volume pressure behind it
CALL 'SUB-RATE-TBL'→a dependency, mapped before anyone touches it

Dependency Mapping Before Migration Risk

The map comes before the migration attempt, not after something breaks — the goal is to de-risk a migration, not clean up after one.

•Produced proactively, not as post-incident forensics
(extends Decision Intelligence)→an application, not a separate engine

Built on Decision Intelligence

Depends on Decision Intelligence's explainability core existing first — LegacySense is an application of that engine, not a separate one.

•Blocked on Decision Intelligence in the same way AgentSense and ClinicalSense are
Concept Architecture

Planned Architecture

Nothing below is built. This describes the intended design and its dependencies — laid out here as a translation view, since that's the actual job: old logic in, plain English out.

Dependency: LegacySense applies Decision Intelligence's explainability engine to legacy source code instead of models or agents. Decision Intelligence's core engine does not exist yet.
Code Parsing · Not yet designed
LEGACY-ROUTINE.CBL
       PERFORM VARYING WS-IDX
           FROM 1 BY 1
           UNTIL WS-IDX > WS-MAX-REC
           IF WS-REC-FLG(WS-IDX) = '1'
               COMPUTE WS-INT-AMT =
                   WS-PRIN * WS-RATE-TBL(WS-IDX)
               ADD WS-INT-AMT TO WS-BAL
           END-IF
       END-PERFORM.
Illustrative snippet — not parsed by a real system.
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Logic Explanation · Unspecified
Plain-English Explanation

"For every active record, calculate interest using that record's entry in the rate table, then add it to the running balance."

Design target for the output — LegacySense doesn't exist yet, so this isn't real output.
Dependency Graph (concept)
Dependency Tracing · Unspecified
This RoutineRate Table LookupBalance Update

Shape only — which routines a piece of legacy logic calls. Not yet designed.

Parent: Decision Intelligence(extends Decision Intelligence): Not startedFull build: Blocked on dependency

Decades-Old Systems

Named starting point: COBOL and similar legacy production code.

Dependency Mapping First

Produces the map before anyone attempts a migration, not after something breaks.

Built on Decision Intelligence

Applies the same explainability engine to code instead of models.

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