bug-prospector

name	bug-prospector
description	Mine for hidden bugs that pattern-based auditors miss. 7 analysis lenses: assumptions, state machines, boundary conditions, data lifecycle, error paths, time-dependent behavior, and platform divergence. Triggers: "prospect for bugs", "find hidden bugs", "assumption audit", "what could go wrong", "bug prospector".
version	1.0.0
author	Terry Nyberg
license	MIT
allowed-tools	["Grep","Glob","Read","Write","Bash","AskUserQuestion","Agent"]
metadata	{"tier":"analysis","category":"debugging"}

Bug Prospector

Quick Ref: Find bugs that pattern-based scanners miss by analyzing intent, not syntax. Output: .agents/research/YYYY-MM-DD-bug-prospector-*.md

YOU MUST EXECUTE THIS WORKFLOW. Do not just describe it.

Required output: Every BUG finding MUST include Urgency, Risk, ROI, and Blast Radius ratings using the Issue Rating Table format. Do not omit these ratings.

Philosophy: Auditing tools find what's syntactically wrong. Bug Prospector finds what's semantically fragile — the gap between "the code compiles" and "the code handles every real-world scenario."

---

Pre-flight: Git Safety Check

git status --short

If uncommitted changes exist:

AskUserQuestion with questions:
[
  {
    "question": "You have uncommitted changes. Commit before proceeding?",
    "header": "Git",
    "options": [
      {"label": "Commit first (Recommended)", "description": "Save current work so you can revert if this skill modifies files"},
      {"label": "Continue without committing", "description": "Proceed — I accept the risk"}
    ],
    "multiSelect": false
  }
]

If "Commit first": Ask for a commit message, stage changed files, and commit. Then proceed.

Freshness

Base all findings on current source code only. Do not read or reference files in .agents/, scratch/, or prior audit reports. Ignore cached findings from auto-memory or previous sessions. Every finding must come from scanning the actual codebase as it exists now.

---

Step 1: Choose Scope and Lenses

1.1: Determine Scope

AskUserQuestion with questions:
[
  {
    "question": "What should I prospect?",
    "header": "Scope",
    "options": [
      {"label": "Specific file or feature", "description": "I'll tell you which file(s) or feature to analyze"},
      {"label": "Recently changed files", "description": "Analyze files changed in the last 5 commits"},
      {"label": "Full codebase", "description": "Broad scan across all source files (slower, more thorough)"}
    ],
    "multiSelect": false
  }
]

If "Specific file or feature": Ask which file(s) or feature name.

If "Recently changed files":

git diff --name-only HEAD~5 -- "*.swift" | head -30

If "Full codebase": Use Glob pattern="**/*.swift" to inventory, then prioritize:

1. ViewModels and Managers (business logic)
2. Data layer (persistence, sync, networking)
3. Views with complex state (forms, multi-step flows)
4. Skip: pure layout views, previews, test files

1.2: Choose Lenses

AskUserQuestion with questions:
[
  {
    "question": "Which analysis lenses should I apply?",
    "header": "Lenses",
    "options": [
      {"label": "All 7 lenses (Recommended)", "description": "Full prospecting — assumptions, state machines, boundaries, data lifecycle, error paths, time, platform"},
      {"label": "Quick 3", "description": "Assumptions + Error Paths + Boundaries — highest bug yield"},
      {"label": "Let me pick", "description": "I'll choose specific lenses"}
    ],
    "multiSelect": false
  }
]

If "Let me pick":

AskUserQuestion with questions:
[
  {
    "question": "Select the lenses to apply:",
    "header": "Lenses",
    "options": [
      {"label": "1. Assumption Audit", "description": "List every implicit assumption and what breaks when violated"},
      {"label": "2. State Machine Analysis", "description": "Find unreachable states, simultaneous states, interrupted transitions"},
      {"label": "3. Boundary Conditions", "description": "Zero, one, max values; empty strings; nil chains; off-by-one"},
      {"label": "4. Data Lifecycle Tracing", "description": "Follow data from creation to deletion — find gaps"}
    ],
    "multiSelect": true
  },
  {
    "question": "Additional lenses:",
    "header": "More",
    "options": [
      {"label": "5. Error Path Exerciser", "description": "What happens when every try/catch and optional chain fails?"},
      {"label": "6. Time-Dependent Bugs", "description": "Timezone, locale, rapid actions, slow network, first launch after weeks"},
      {"label": "7. Platform Divergence", "description": "Hardware assumptions, OS version gaps, device-specific behavior"}
    ],
    "multiSelect": true
  }
]

---

Step 2: Execute Selected Lenses

For each file in scope, apply the selected lenses. Read the full file before analysis — never analyze from grep matches alone.

Lens 1: Assumption Audit

Goal: Surface every implicit assumption the code makes, then evaluate what happens when each is violated.

Process:

1. Read the file completely
2. For every function/computed property, list assumptions such as:
   • "This array will always have at least one element"
   • "This network call will complete before the view disappears"
   • "The user will have iCloud enabled"
   • "This date string will always be in ISO 8601 format"
   • "This dictionary key will always exist"
   • "The parent view will always pass a non-nil value"
   • "This enum will never have new cases added"
3. For each assumption, determine:
   • How likely is violation? (Never / Rare / Occasional / Common)
   • What happens on violation? (Crash / Silent data loss / Wrong UI / Graceful degradation)
   • Is there a guard? (Yes — handled / No — unprotected)
4. Flag as BUG if: likelihood >= Rare AND consequence >= Silent data loss AND no guard

Search accelerators (grep for common assumption patterns):

Grep pattern="\.first!" glob="**/*.swift"
Grep pattern="\.last!" glob="**/*.swift"
Grep pattern="\[0\]" glob="**/*.swift"
Grep pattern="\.removeFirst\(\)" glob="**/*.swift"
Grep pattern="as!" glob="**/*.swift"

Lens 2: State Machine Analysis

Goal: Find states that become unreachable, states that can be simultaneously active, and transitions that leave the app in an inconsistent state.

Process:

1. Identify all @State, @Published, @Observable properties that represent user-facing state
2. Map the state transitions:
   • Draw the state graph: which states lead to which?
   • Can any state become a dead end? (entered but never exited)
   • Can two mutually exclusive states be true simultaneously?
3. Check interruption resilience:
   • What happens if the user backgrounds the app mid-transition?
   • What happens if a sheet is dismissed during an async operation?
   • What happens if the view disappears before a Task completes?
4. Check reset paths:
   • After an error, does state reset to a usable starting point?
   • After cancellation, are all intermediate states cleaned up?

Search accelerators:

Grep pattern="@State.*=.*true" glob="**/*.swift"
Grep pattern="@Published.*=.*true" glob="**/*.swift"
Grep pattern="isLoading|isProcessing|isSaving|isAnalyzing" glob="**/*.swift"
Grep pattern="showingError|showingAlert|showingSheet" glob="**/*.swift"

Lens 3: Boundary Conditions

Goal: Find off-by-one errors, empty collection crashes, and edge case failures.

Process:

1. For every conditional (if, guard, switch), evaluate:
   • Zero: What happens with 0 items, empty string, nil?
   • One: What happens with exactly 1 item? (Singular/plural, first==last)
   • Maximum: What happens at Int.max, massive arrays, very long strings?
   • Negative: What happens with negative numbers where unsigned is expected?
2. For every array/collection access:
   • Is the index bounds-checked?
   • Does removeFirst() / removeLast() have an emptiness guard?
   • Does prefix() / suffix() handle count > array.count?
3. For every string operation:
   • Does it handle empty strings?
   • Does it handle Unicode (emoji, RTL, combining characters)?
   • Does it handle strings with special characters (quotes, backslashes)?

Search accelerators:

Grep pattern="\.remove(First|Last)\(\)" glob="**/*.swift"
Grep pattern="\.\[.*\]" glob="**/*.swift"
Grep pattern="\.prefix\(|\.suffix\(" glob="**/*.swift"
Grep pattern="\.split\(|\.components\(" glob="**/*.swift"
Grep pattern="Int\.max|\.count\s*-\s*1" glob="**/*.swift"

Lens 4: Data Lifecycle Tracing

Goal: Follow data from creation to deletion and find gaps where data can be lost, duplicated, or become stale.

Process:

1. Pick the primary data entities (models, cached values, user input)
2. For each entity, trace:
   • Creation: Where is it created? What validations exist at creation time?
   • Modification: Where is it modified? Can modifications conflict? Are changes persisted immediately or batched?
   • Persistence: Where is it saved? Can the save fail silently? Is there a race between saves?
   • Display: Where is it displayed? Can stale data be shown after a background update?
   • Deletion: Where is it deleted? Are all references cleaned up? Are related entities cascaded?
   • Sync: If synced, what happens on conflict? Is there a "last write wins" that could lose data?
3. Flag gaps:
   • Created but never persisted (in-memory only, lost on crash)
   • Modified but UI not updated (stale display)
   • Deleted but references remain (dangling pointers, orphaned data)
   • Synced but no conflict resolution

Search accelerators:

Grep pattern="context\.insert\(" glob="**/*.swift"
Grep pattern="context\.delete\(" glob="**/*.swift"
Grep pattern="context\.save\(" glob="**/*.swift"
Grep pattern="\.deleteRule\s*=" glob="**/*.swift"
Grep pattern="@Query" glob="**/*.swift"

Lens 5: Error Path Exerciser

Goal: For every try/catch, async/await, and optional chain — determine what happens when the error path is taken.

Process:

1. Find all error-producing code:
   • try / try? / try!
   • await (can throw via Task cancellation)
   • Optional chaining (?.)
   • guard let ... else { return }
2. For each error path, evaluate:
   • Does the UI reflect the error? Or does it show a loading state forever?
   • Is the app left in a consistent state? Or is it half-modified?
   • Can the user retry? Or are they stuck?
   • Is the error logged? Or silently swallowed?
3. Specifically check for:
   • try? that converts a meaningful error to nil (information loss)
   • catch blocks that log but don't update UI state
   • Missing isLoading = false in error paths (loading state trap)
   • guard let with bare return that silently aborts a user-initiated action
   • Task {} without error handling (errors vanish)

Search accelerators:

Grep pattern="try\?" glob="**/*.swift"
Grep pattern="catch\s*\{" glob="**/*.swift" -A 3
Grep pattern="guard let.*else\s*\{\s*return\s*\}" glob="**/*.swift"
Grep pattern="Task\s*\{" glob="**/*.swift" -A 5

Lens 6: Time-Dependent Bugs

Goal: Find code that behaves differently based on time, speed, or duration.

Process:

1. Timezone and locale:
   • DateFormatters without explicit timezone set
   • Date comparisons using < instead of Calendar methods
   • String-to-date parsing that assumes a specific locale
   • Display of dates without considering user's locale
2. Duration since last use:
   • Cached data that expires but has no expiry check
   • Tokens/sessions that timeout but the app doesn't re-authenticate
   • "First launch" flags that don't account for app updates
3. Rapid repeated actions:
   • Buttons without debouncing that trigger duplicate network calls
   • Double-tap on save that creates duplicate records
   • Rapid navigation that crashes due to concurrent presentations
4. Slow or absent network:
   • Operations that assume network availability
   • Missing timeout on network requests
   • No offline fallback for features that need data
   • Optimistic UI that doesn't roll back on failure

Search accelerators:

Grep pattern="DateFormatter\(\)" glob="**/*.swift"
Grep pattern="Date\(\)" glob="**/*.swift"
Grep pattern="timeIntervalSince" glob="**/*.swift"
Grep pattern="URLSession.*dataTask\|URLSession.*data\(" glob="**/*.swift"
Grep pattern="\.debounce\|\.throttle" glob="**/*.swift"

Lens 7: Platform Divergence

Goal: Find code that assumes specific hardware, OS version, or device capabilities.

Process:

1. Hardware assumptions:
   • Image/video processing that assumes GPU acceleration (fails on Intel Macs, old devices)
   • Memory-intensive operations without pressure checks
   • Camera/sensor access without capability checks
   • Biometric auth that assumes Face ID (could be Touch ID or neither)
2. OS version gaps:
   • #available checks where the else branch is incomplete or empty
   • Features gated by availability but degraded path not tested
   • API behavioral differences between OS versions (not just availability)
3. Device-specific behavior:
   • Screen size assumptions (hardcoded widths, missing adaptive layout)
   • Keyboard presence assumptions (iPad with hardware keyboard, Mac)
   • Rotation handling that only works on certain devices
   • Split View / Stage Manager compatibility
4. Platform #if blocks:
   • #if os(iOS) with logic not mirrored in #else (macOS)
   • Platform-specific features without feature detection
   • Conditional compilation where one branch is clearly less tested

Search accelerators:

Grep pattern="#if os\(" glob="**/*.swift"
Grep pattern="#available\(" glob="**/*.swift"
Grep pattern="UIScreen\.main" glob="**/*.swift"
Grep pattern="UIDevice\.current" glob="**/*.swift"
Grep pattern="ProcessInfo.*physicalMemory\|ProcessInfo.*processorCount" glob="**/*.swift"
Grep pattern="CIContext\|MTLDevice\|MTLCreateSystemDefaultDevice" glob="**/*.swift"

---

Step 3: Verification Rule

Before classifying ANY finding:

1. Read the flagged file — at minimum 30 lines around the issue
2. Check for existing guards — the assumption may already be protected
3. Check for intentional design — comments, documentation, or clear architectural decisions
4. Check if it's actually reachable — dead code or unreachable paths are not bugs
5. Assess real-world likelihood — theoretical issues in impossible scenarios are not bugs
6. Count blast radius — grep for callers/references of the affected function or property to determine how many files the fix would touch
7. Classify as:
   • BUG: Real risk, no guard, realistic scenario
   • FRAGILE: Works now but will break under foreseeable conditions
   • OK: Already guarded or intentional design
   • REVIEW: Unclear, needs human judgment

Classification rules:

• A finding is NOT a bug if the code already handles the case (even if the handling is in a different function)
• A finding is NOT a bug if the scenario requires conditions that the app's architecture prevents
• A finding IS a bug if a real user could trigger it through normal usage
• A finding is FRAGILE if it works today but depends on an assumption that could change

---

Step 4: Generate Report

4.1: Check Terminal Width

Before rendering the report, check terminal width:

tput cols

• 160+ columns: Use the full 8-column table inline and in the report file.
• Under 160 columns: Use the compact 4-column table inline, write the full 8-column table to the report file only. Display this notice after the inline table:

Compact view — your terminal is [N] columns wide (160+ needed for full table). The complete Issue Rating Table with all 8 columns has been written to .agents/research/YYYY-MM-DD-bug-prospector-<scope>.md. Open that file or widen your terminal to 160+ columns to view it as a single table.

4.2: Render Report

Display the summary and findings inline, then write to .agents/research/YYYY-MM-DD-bug-prospector-<scope>.md.

The report file always uses the full 8-column table regardless of terminal width.

# Bug Prospector Report: [Scope Description]

**Date:** YYYY-MM-DD
**Scope:** [Files/features analyzed]
**Lenses Applied:** [List of lenses used]
**Files Analyzed:** N

## Summary

| Status | Count |
|--------|-------|
| Bugs Found | X |
| Fragile Code | Y |
| OK (Already Guarded) | Z |
| Needs Review | W |

## Issue Rating Table

All BUG and FRAGILE findings rated and sorted by Urgency then ROI:

Full table (160+ columns) — used inline AND in report file:

#	Finding	Lens	Urgency	Risk: Fix	Risk: No Fix	ROI	Blast Radius	Fix Effort
1	File.swift:45 — array accessed without bounds check	Boundary	🔴 Critical	⚪ Low	🔴 Critical	🟠 Excellent	⚪ 1 file	Trivial
2	Manager.swift:89 — isLoading never reset on error	Error Path	🟡 High	⚪ Low	🟡 High	🟠 Excellent	⚪ 1 file	Trivial
3	ViewModel.swift:200 — DateFormatter without timezone	Time	🟢 Medium	⚪ Low	🟢 Medium	🟢 Good	🟢 3 files	Small

Compact table (under 160 columns) — used inline only:

#	Finding	Urgency	Fix Effort
1	File.swift:45 — array accessed without bounds check	🔴 Critical	Trivial
2	Manager.swift:89 — isLoading never reset on error	🟡 High	Trivial
3	ViewModel.swift:200 — DateFormatter without timezone	🟢 Medium	Small

The compact table keeps the two most actionable columns (Urgency + Fix Effort). Full ratings are in the report file.

Use the Issue Rating scale:
- **Urgency:** 🔴 CRITICAL (crash/data loss) · 🟡 HIGH (incorrect behavior) · 🟢 MEDIUM (degraded UX) · ⚪ LOW (cosmetic/minor)
- **Risk: Fix:** Risk of the fix introducing regressions (⚪ Low for isolated changes, 🟡 High for shared code paths)
- **Risk: No Fix:** User-facing consequence if left unfixed
- **ROI:** 🟠 Excellent · 🟢 Good · 🟡 Marginal · 🔴 Poor
- **Blast Radius:** Number of files the fix touches (e.g., "⚪ 1 file", "🟢 3 files", "🟡 12 files"). Count by grepping for callers/references before rating.
- **Fix Effort:** Trivial / Small / Medium / Large

Detailed Findings

1. [File:Line] — [Brief Description]

Lens: [Which lens found this] Assumption: [What the code assumes] Violation scenario: [How a real user triggers this] Consequence: [What happens — crash, data loss, wrong UI, etc.]

Current code:

// problematic code

Suggested fix:

// corrected code

2. [File:Line] — [Brief Description]

...

Fragile Code (Works Now, May Break Later)

F1. [File:Line] — [Brief Description]

Lens: [Which lens found this] Current behavior: [What happens now] Breaking scenario: [What foreseeable change would break this] Recommendation: [How to harden it]

Already Guarded (Reference)

These were flagged by search but are correctly handled:

• file.swift:123 — [why it's OK]

Needs Human Review

These findings require domain knowledge to classify:

• file.swift:456 — [what's unclear and why]

---

## Step 5: Follow-up

AskUserQuestion with questions: [ { "question": "How would you like to proceed?", "header": "Next", "options": [ {"label": "Fix all bugs now", "description": "Walk through each BUG finding and apply fixes (phase-by-phase)"}, {"label": "Fix selected bugs", "description": "I'll choose which ones to fix"}, {"label": "Create implementation plan", "description": "Generate a phased plan from the findings"}, {"label": "Report is sufficient", "description": "I'll handle fixes manually"} ], "multiSelect": false } ]

If creating plan: Group findings by file proximity and dependency, order by urgency, output as a numbered plan.

### Fix Workflow: "Fix all bugs now"

Group bugs into phases by file proximity and dependency (as in the report's Implementation Plan). Before each phase, prompt with a **phase gate** — one question, always includes opt-out:

AskUserQuestion with questions: [ { "question": "Phase N: [Phase name] ([count] fixes — [key files]). Proceed?", "header": "Phase N", "options": [ {"label": "Proceed (Recommended)", "description": "Implement this phase now"}, {"label": "Proceed — skip remaining phase gates", "description": "Batch mode: implement all remaining phases without prompting"}, {"label": "Let's chat about this phase", "description": "Discuss before deciding"}, {"label": "Stop here", "description": "Skip remaining phases"} ], "multiSelect": false } ]

**Every phase gets this same prompt** (including the opt-out) until the user either completes all phases or opts out.

**Rules:**
- If user chooses "skip remaining phase gates": execute all remaining phases without prompting
- If user chooses "Let's chat": wait for user input, answer questions, then re-prompt the same phase gate
- If user chooses "Stop here": stop fixing and report what was completed
- Always build both platforms after each phase to verify

### Fix Workflow: "Fix selected bugs"

Present the bug list for selection:

AskUserQuestion with questions: [ { "question": "Which bugs should I fix? (Reference the Issue Rating Table above)", "header": "Select", "options": [ {"label": "Bug 1 — [brief description]", "description": "[Urgency] [Fix Effort]"}, {"label": "Bug 2 — [brief description]", "description": "[Urgency] [Fix Effort]"}, {"label": "Bug 3 — [brief description]", "description": "[Urgency] [Fix Effort]"} ], "multiSelect": true } ]

After selection, one confirmation prompt with opt-out:

AskUserQuestion with questions: [ { "question": "Fix [N] selected bugs: [brief list]. Proceed?", "header": "Confirm", "options": [ {"label": "Proceed (Recommended)", "description": "Fix all selected bugs now"}, {"label": "Let's chat first", "description": "Discuss specific bugs before fixing"}, {"label": "Go back", "description": "Re-select bugs"} ], "multiSelect": false } ]

Then fix all selected bugs without per-bug prompting — the selection itself was the decision.

**If user chooses "Let's chat":** Answer questions, then re-prompt the confirmation.

---

## Lens Selection Guide

| Situation | Recommended Lenses |
|-----------|--------------------|
| Pre-release audit | All 7 |
| After adding a new feature | 1 (Assumptions) + 2 (State) + 5 (Errors) |
| After a crash report | 3 (Boundaries) + 5 (Errors) + 7 (Platform) |
| Debugging intermittent failures | 2 (State) + 6 (Time) |
| New platform support (macOS/iPad) | 7 (Platform) + 3 (Boundaries) |
| Data model changes | 4 (Data Lifecycle) + 1 (Assumptions) |
| Performance investigation | 3 (Boundaries) + 6 (Time) |

---

## What This Finds vs. What Auditors Find

| Auditors Find | Bug Prospector Finds |
|---------------|---------------------|
| Missing `@MainActor` | State machine deadlocks |
| Force unwraps | Assumptions that hold today but break tomorrow |
| Retain cycles | Data that's created but never cleaned up |
| Missing `try?` conversion | Error paths that leave UI in loading state |
| Deprecated API usage | Code that works on Apple Silicon but fails on Intel |
| Missing accessibility labels | Rapid-tap scenarios that create duplicate data |

---

## Troubleshooting

| Problem | Solution |
|---------|----------|
| Too many findings | Narrow scope to specific files or use "Quick 3" lenses |
| All findings are theoretical | Increase the realism threshold — only flag scenarios a real user could trigger |
| Overlapping with auditor findings | Focus on *why* not *what* — auditors find the pattern, prospector finds the consequence |
| File too complex to analyze | Split analysis by MARK sections or extract to Agent subprocesses |
| Can't determine if guarded | Classify as REVIEW, not BUG — let the human decide |