Overview

The Strangler Pattern Specialist is an L3 agent operating in the integration domain of the Prismatic Platform. This agent manages the gradual replacement of legacy system components using the strangler fig pattern -- a software migration strategy inspired by the strangler fig tree that grows around its host, eventually replacing it entirely while maintaining system functionality throughout the transition.

In a platform with 90 umbrella applications and over 20 years of accumulated knowledge in the GARDEN legacy repository system, systematic legacy replacement is an ongoing operational concern. The Strangler Pattern Specialist ensures that legacy components are replaced incrementally, with each replacement step maintaining full backward compatibility and zero downtime. This approach contrasts with "big bang" rewrites that carry unacceptable risk for production systems operating under the NO MERCY doctrine.

This agent is part of the platform's 434-strong autonomous agent ecosystem, operating under AIAD standard compliance and coordinating with the GARDEN integration infrastructure for legacy knowledge extraction.

The Strangler Fig Pattern

The strangler fig pattern was first described by Martin Fowler and has become the industry-standard approach for safely replacing legacy systems. The pattern consists of three phases applied iteratively to each component of the legacy system.

Phase	Activity	Risk Level	Duration
Transform	Create new implementation alongside legacy	Low	Days-Weeks
Coexist	Route traffic to new implementation gradually	Medium	Weeks
Eliminate	Remove legacy component once fully replaced	Low	Days

Pattern Lifecycle

Legacy System (100% traffic)
    ├── Step 1: Build new component A alongside legacy A
    ├── Step 2: Route 10% traffic to new A (canary)
    ├── Step 3: Route 50% traffic to new A (split)
    ├── Step 4: Route 100% traffic to new A (full cutover)
    ├── Step 5: Remove legacy A (elimination)
    └── Repeat for components B, C, D...

Migration Tracking

The Strangler Pattern Specialist maintains a comprehensive migration registry that tracks the status of every legacy component undergoing replacement.

Component	Legacy Location	New Location	Phase	Traffic Split	Health
Entity Resolution	GARDEN/sig	prismatic_storage_core	Eliminated	100% new	Healthy
OSINT Providers	GARDEN/sig	prismatic_osint	Coexist	85% new	Healthy
Graph Storage	GARDEN/kuzu-ex	prismatic_storage_kuzu	Coexist	90% new	Healthy
Blackboard System	GARDEN/prismatic-legacy	prismatic_blackboard	Transform	0% new	In Progress

Technical Implementation

defmodule PrismaticAgents.StranglerPatternSpecialist do
  @moduledoc """
  L3 Strangler Pattern Specialist agent.
  Manages gradual legacy system replacement using strangler fig pattern.
  """

  use GenServer
  require Logger

  @migration_check_interval_ms :timer.hours(1)

  defstruct [
    :migration_registry,
    :active_migrations,
    :traffic_split_configs,
    :health_checks,
    :last_check_at,
    status: :monitoring
  ]

  @spec start_link(keyword()) :: GenServer.on_start()
  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
  end

  @impl true
  def init(_opts) do
    registry = load_migration_registry()
    schedule_migration_check()
    {:ok, %__MODULE__{migration_registry: registry, active_migrations: []}}
  end

  @impl true
  def handle_info(:migration_check, state) do
    health = check_all_migration_health(state.migration_registry)
    recommendations = analyze_traffic_split_readiness(state.migration_registry)

    :telemetry.execute(
      [:prismatic, :agents, :strangler, :check],
      %{active_migrations: length(state.active_migrations)},
      %{healthy: health.healthy_count, unhealthy: health.unhealthy_count}
    )

    schedule_migration_check()

    {:noreply, %{state |
      health_checks: health,
      last_check_at: DateTime.utc_now()
    }}
  end

  @spec advance_migration(String.t(), float()) :: {:ok, map()} | {:error, term()}
  def advance_migration(component_id, new_traffic_percentage) do
    GenServer.call(__MODULE__, {:advance, component_id, new_traffic_percentage})
  end

  @impl true
  def handle_call({:advance, component_id, percentage}, _from, state) do
    with {:ok, migration} <- find_migration(state.migration_registry, component_id),
         :ok <- validate_health_prerequisites(migration),
         {:ok, updated} <- update_traffic_split(migration, percentage) do
      {:reply, {:ok, updated}, update_registry(state, updated)}
    else
      {:error, reason} -> {:reply, {:error, reason}, state}
    end
  end
end

Traffic Routing Strategy

The Strangler Pattern Specialist implements sophisticated traffic routing that enables gradual migration with real-time health monitoring.

Routing Strategy	Description	Use Case
Canary	Route small percentage to new system	Initial validation
A/B Split	Deterministic split based on request attributes	Comparative testing
Shadow	Send copies to new system without using results	Pre-production validation
Gradual Ramp	Incrementally increase new system traffic	Controlled rollout
Feature Flag	Route based on feature flag state	Per-feature migration

Health Check Framework

Before any traffic split advancement, the specialist runs comprehensive health checks on both legacy and new implementations.

Health Check	Threshold	Block Advancement
Error rate	< 0.1%	Yes
Latency P95	< 2x legacy	Yes
Data consistency	100% match	Yes
Resource usage	< 1.5x legacy	Warning
Test coverage	> 90%	Yes

GARDEN Integration

The Strangler Pattern Specialist coordinates closely with the GARDEN legacy knowledge system to extract patterns, algorithms, and domain knowledge from legacy repositories before replacement. This extraction process ensures that decades of accumulated domain knowledge are preserved and migrated to the new implementations rather than being lost during component replacement.

GARDEN Repository	Content	Files	Extraction Status	Priority
sig	250+ OSINT providers	1,200+	85% extracted	P1
prismatic-legacy	Blackboard system, core logic	1,302	60% extracted	P1
kuzu-ex	KuzuDB Elixir SDK	45	95% extracted	P2
crisstal	Pattern matching engine	280	70% extracted	P2
code-weaver	Code generation templates	150	50% extracted	P3
simple_geocoder	Geocoding library	35	100% extracted	Complete

Migration Risk Assessment

Before advancing any migration phase, the Strangler Pattern Specialist conducts a comprehensive risk assessment that evaluates both technical and operational risks associated with the migration step.

defmodule PrismaticAgents.StranglerPatternSpecialist.RiskAssessment do
  @moduledoc """
  Migration risk assessment for strangler pattern phase advancement.
  Evaluates technical and operational risks before traffic split changes.
  """

  @spec assess_migration_risk(map(), float()) :: {:ok, :acceptable} | {:error, :unacceptable, map()}
  def assess_migration_risk(migration, target_percentage) do
    risks = [
      assess_data_consistency_risk(migration),
      assess_performance_risk(migration),
      assess_rollback_capability(migration),
      assess_downstream_impact(migration, target_percentage),
      assess_monitoring_coverage(migration)
    ]

    max_risk = Enum.max_by(risks, & &1.score)
    total_risk = Enum.sum(Enum.map(risks, & &1.score)) / length(risks)

    cond do
      max_risk.score > 0.8 ->
        {:error, :unacceptable, %{reason: max_risk.category, score: max_risk.score}}
      total_risk > 0.6 ->
        {:error, :unacceptable, %{reason: :aggregate_risk, score: total_risk}}
      true ->
        {:ok, :acceptable}
    end
  end

  defp assess_data_consistency_risk(migration) do
    consistency_score = compare_output_consistency(
      migration.legacy_component,
      migration.new_component,
      migration.test_inputs
    )

    %{category: :data_consistency, score: 1.0 - consistency_score}
  end
end

Risk Category	Assessment Method	Acceptable Threshold	Blocking
Data Consistency	Output comparison with 1,000+ test inputs	< 0.1% divergence	Yes
Performance	Benchee comparison under realistic load	< 2x legacy latency	Yes
Rollback Capability	Verified rollback procedure with test execution	Must complete < 5 min	Yes
Downstream Impact	Dependency analysis of all consumers	No breaking changes	Yes
Monitoring Coverage	Telemetry event verification	100% of key metrics covered	Yes

Integration Points

Quality Gates -- Migration advancement gated by quality checks
Telemetry Integration -- Migration health metrics
Real-time Monitoring -- Live migration dashboards
AIAD Standard -- Full agent specification compliance

Rollback Procedures

Every migration managed by the Strangler Pattern Specialist includes a documented and tested rollback procedure. Rollback capability is a non-negotiable prerequisite for advancing any migration phase, as the NO MERCY doctrine requires that no migration step can leave the platform in a state where reversal is impossible.

Rollback Aspect	Requirement	Verification
Traffic Routing	Instant redirect back to legacy component	Tested before each advancement
Data Migration	Backward-compatible schema changes only	Schema reversibility proven
Configuration	Feature flags for instant toggle	Flag state verified in staging
Dependencies	Both legacy and new dependencies available	Dependency tree validated
State Recovery	Stateful components preserve rollback state	State snapshot before advancement

The Strangler Pattern Specialist maintains rollback procedures as executable scripts that can be triggered manually by operators or automatically by the platform's health monitoring system. Each rollback procedure is tested quarterly to ensure it remains functional as the system evolves.

Migration Success Criteria

Before any migration component can be declared "eliminated" (fully migrated), it must pass a comprehensive set of success criteria verified by both automated testing and manual review.

Criterion	Measurement	Threshold	Authority
Functional Equivalence	Output comparison against 10,000+ test cases	100% match	Automated
Performance Parity	Benchmark comparison under production load	Within 10% of legacy	Automated
Zero Downtime	Monitoring during migration period	0 user-visible errors	Automated
Test Coverage	New implementation test coverage	> 95% line coverage	Automated
Documentation	Migration report with architectural decisions	Complete report filed	Manual review

AIAD Specification Compliance

AIAD Component	Status
Agent specification file	Compliant
Behavioral rules	12 rules defined
Telemetry integration	Full coverage
NM/ND doctrine enforcement	Active
SEADF integration	Registered

Scalability Architect -- Ensures new implementations scale properly
Source Archive Specialist -- Archives legacy code before removal
Unified Orchestrator -- Coordinates multi-agent migration tasks

Authority Level

L3 - Strategic Command - Multi-domain coordination with authority to manage legacy system replacement across the platform's umbrella applications.

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Created by Tomáš Korcak (korczis) | Open Source under GHL

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strangler-pattern-specialist

Overview

The Strangler Fig Pattern

Pattern Lifecycle

Migration Tracking

Technical Implementation

Traffic Routing Strategy

Health Check Framework

GARDEN Integration

Migration Risk Assessment

Integration Points

Rollback Procedures

Migration Success Criteria

AIAD Specification Compliance

Authority Level

Connect & Contribute

Agent Info

Agent Distribution

Agent Domains

Related Content

Color Teams

Doctrine

OSINT Sources

strangler-pattern-specialist

Overview

The Strangler Fig Pattern

Pattern Lifecycle

Migration Tracking

Technical Implementation

Traffic Routing Strategy

Health Check Framework

GARDEN Integration

Migration Risk Assessment

Integration Points

Rollback Procedures

Migration Success Criteria

AIAD Specification Compliance

Related Agents

Authority Level

Connect & Contribute

Agent Info

Agent Distribution

Agent Domains

Related Content

Color Teams

Doctrine

OSINT Sources