Arch Lens Error Resilience

Error/Resilience Architecture Lens

Cognitive Mode: Diagnostic Primary Question: "How are failures handled?" Focus: Error Propagation, Recovery Mechanisms, Circuit Breakers, Validation Gates

When to Use

• Need to understand error handling architecture
• Documenting recovery and retry mechanisms
• Analyzing validation gates and circuit breakers
• User invokes /autoskillit:arch-lens-error-resilience or /autoskillit:make-arch-diag error

Critical Constraints

NEVER:

• Modify any source code files
• Show happy path details (that's process flow lens)
• Ignore validation and fail-fast patterns
• Run subagents in the background (run_in_background: true is prohibited)

ALWAYS:

• Focus on FAILURE paths and recovery
• Show validation gates and their failure modes
• Document retry limits and circuit breakers
• Include exception hierarchy if present
• BEFORE creating any diagram, LOAD the /autoskillit:mermaid skill using the Skill tool - this is MANDATORY
• If the Skill tool cannot be used (disable-model-invocation) or refuses this invocation, do NOT proceed with diagram creation. Abort this step and omit the diagram from output.
• After writing the diagram file, emit the absolute path as a structured output token as your final output. Resolve the relative temp/arch-lens-error-resilience/... save path to absolute by prepending the full CWD:

  diagram_path = /absolute/cwd/temp/arch-lens-error-resilience/{filename}.md
  

  This token is MANDATORY — the pipeline cannot proceed without it.

Arguments

/autoskillit:arch-lens-error-resilience [context_path]

• context_path (optional) — Absolute path to a PR context file containing new files (★-prefixed) and modified files (●-prefixed) from the PR diff. When provided, read this file before beginning analysis and focus the diagram on the architectural areas affected by these specific files. When absent, explore the full CWD.

Analysis Workflow

Step 0: Read PR context (when provided)

If a context_path positional argument is present:

1. Read the file at context_path
2. Extract: new files list (★-prefixed), modified files list (●-prefixed)
3. Focus Step 1 exploration on the modules/components these files belong to
4. Apply ★ prefix on diagram nodes representing new files/components
5. Apply ● prefix on diagram nodes representing modified files/components

If no context_path is provided, skip this step and explore the full CWD in Step 1.

Step 1: Launch Parallel Exploration Subagents

Spawn Explore subagents to investigate:

Exception Hierarchy

• Find custom exception classes
• Map inheritance relationships
• Look for: Exception, Error, raise, error classes, custom exceptions

Validation Gates

• Find validation/guard functions
• Identify fail-fast patterns
• Look for: validate_*, check_*, assert, guard, gate, precondition checks

Error Detection

• Find error detection points
• Identify how failures are recognized
• Look for: try/except, catch, on_error, handle_error, error handling

Recovery Mechanisms

• Find retry logic
• Identify fallback strategies
• Look for: retry, backoff, attempt, max_retries, retry policies

Circuit Breakers

• Find patterns that prevent infinite retries
• Identify failure thresholds
• Look for: circuit, breaker, max_failures, trip, failure thresholds

Error Routing

• Find how errors are propagated
• Identify error terminal states
• Look for: raise, return Error, error node, ERROR state

Step 2: Map Error Paths

For each major operation, document:

• Success Path: Normal completion
• Retry Path: Transient failure recovery
• Failure Path: Permanent failure handling
• Circuit Break Path: Threshold exceeded

CRITICAL - Analyze Read/Write Direction: For EVERY error handling component:

• Error context capture: What data is READ to build error context?
• Error logging: Where are errors WRITTEN (logs, database, files)?
• State updates: What state is WRITTEN on failure?
• Recovery reads: What data is READ during recovery?

Distinguish:

• Error logs (write-only, never read back for logic)
• Failure context in database (may be read for retry/debugging)
• Debug artifacts (write-only diagnostics)

Step 3: Document Recovery Mechanisms

Step 4: Create the Diagram

Use flowchart with:

Direction: TB for error flow hierarchy

Subgraphs:

• Execution (normal operation)
• Validation Gates (fail-fast checks)
• Error Handling (detection and routing)
• Recovery (retry, fallback)
• Terminals (success, failure states)

Node Styling:

• handler class: Execution nodes
• detector class: Validation gates, error detection
• gap class: Failed/error state (yellow warning)
• stateNode class: Decision points, circuit breaker
• output class: Recovery actions
• terminal class: Final states (success, error)

Connection Types:

• Solid: Normal flow
• Edge labels: Conditions, error types
• Show loops for retry mechanisms

Step 5: Write Output

Write the diagram to: {{AUTOSKILLIT_TEMP}}/arch-lens-error-resilience/arch_diag_error_resilience_{YYYY-MM-DD_HHMMSS}.md (relative to the current working directory)

After writing the diagram file, emit a structured output line:

IMPORTANT: Emit the structured output tokens as literal plain text with no markdown formatting on the token names. Do not wrap token names in **bold**, *italic*, or any other markdown. The adjudicator performs a regex match on the exact token name — decorators cause match failure.

diagram_path = {absolute_path_to_diagram_file}

Output Template

# Error/Resilience Diagram: {System Name}

**Lens:** Error/Resilience (Diagnostic)
**Question:** How are failures handled?
**Date:** {YYYY-MM-DD}
**Scope:** {What was analyzed}

## Exception Hierarchy

BaseError ├── ValidationError ├── ProcessingError │ └── RetryableError └── FatalError

## Resilience Diagram

```mermaid
%%{init: {'flowchart': {'nodeSpacing': 40, 'rankSpacing': 50, 'curve': 'basis'}}}%%
flowchart TB
    %% CLASS DEFINITIONS %%
    classDef terminal fill:#1a237e,stroke:#7986cb,stroke-width:2px,color:#fff;
    classDef stateNode fill:#004d40,stroke:#4db6ac,stroke-width:2px,color:#fff;
    classDef handler fill:#e65100,stroke:#ffb74d,stroke-width:2px,color:#fff;
    classDef phase fill:#6a1b9a,stroke:#ba68c8,stroke-width:2px,color:#fff;
    classDef detector fill:#b71c1c,stroke:#ef5350,stroke-width:2px,color:#fff;
    classDef output fill:#00695c,stroke:#4db6ac,stroke-width:2px,color:#fff;
    classDef gap fill:#ff6f00,stroke:#ffa726,stroke-width:2px,color:#000;

    subgraph Execution ["EXECUTION"]
        EXEC["Execute<br/>━━━━━━━━━━<br/>Main operation"]
        SUCCESS["SUCCESS<br/>━━━━━━━━━━<br/>Completed"]
        RETRY["RETRY<br/>━━━━━━━━━━<br/>Transient failure"]
        FAILED["FAILED<br/>━━━━━━━━━━<br/>Needs handling"]
    end

    subgraph Gates ["VALIDATION GATES (Fail-Fast)"]
        GATE1["Validate Input<br/>━━━━━━━━━━<br/>Check required fields"]
        GATE2["Validate State<br/>━━━━━━━━━━<br/>Check preconditions"]
    end

    subgraph Recovery ["RECOVERY MECHANISMS"]
        direction TB
        R_RETRY["Retry with Backoff<br/>━━━━━━━━━━<br/>Max N attempts"]
        R_FALLBACK["Fallback Action<br/>━━━━━━━━━━<br/>Alternative path"]
        R_CIRCUIT{"Circuit<br/>Breaker<br/>triggered?"}
    end

    subgraph Terminals ["TERMINAL STATES"]
        T_COMPLETE([COMPLETE])
        T_ERROR([ERROR])
        T_CIRCUIT([CIRCUIT_BROKEN])
    end

    %% EXECUTION FLOW %%
    EXEC --> SUCCESS
    EXEC --> RETRY
    EXEC --> FAILED

    SUCCESS --> T_COMPLETE
    RETRY -->|"back to queue"| EXEC

    %% VALIDATION GATES %%
    GATE1 -->|"missing"| T_ERROR
    GATE1 -->|"valid"| GATE2
    GATE2 -->|"invalid"| T_ERROR
    GATE2 -->|"valid"| EXEC

    %% RECOVERY %%
    FAILED --> R_CIRCUIT
    R_CIRCUIT -->|"not triggered"| R_RETRY
    R_CIRCUIT -->|"triggered"| T_CIRCUIT
    R_RETRY --> EXEC
    R_RETRY -->|"exhausted"| R_FALLBACK
    R_FALLBACK --> T_ERROR

    %% CLASS ASSIGNMENTS %%
    class EXEC,SUCCESS handler;
    class RETRY,FAILED gap;
    class GATE1,GATE2 detector;
    class R_RETRY,R_FALLBACK output;
    class R_CIRCUIT stateNode;
    class T_COMPLETE,T_ERROR,T_CIRCUIT terminal;

Color Legend:

Recovery Mechanisms

Validation Gates

---

## Pre-Diagram Checklist

Before creating the diagram, verify:

- [ ] LOADED `/autoskillit:mermaid` skill using the Skill tool
- [ ] Using ONLY classDef styles from the mermaid skill (no invented colors)
- [ ] Diagram will include a color legend table

---

## Related Skills

- `/autoskillit:make-arch-diag` - Parent skill for lens selection
- `/autoskillit:mermaid` - MUST BE LOADED before creating diagram
- `/autoskillit:arch-lens-process-flow` - For normal flow view
- `/autoskillit:arch-lens-concurrency` - For parallel failure handling