dbg

dbg - Stateless Debugger & Browser Automation

Debug Node.js processes and native apps programmatically. Every dbg invocation is stateless: one command in, one response out, exit. A background daemon holds the CDP/DAP connection between calls.

When to Use

• User reports a bug or unexpected behavior in Node.js code
• Need to inspect runtime state, variables, or call stacks
• Investigating why code fails at a specific line
• Analyzing object properties or prototype chains
• Diagnosing slow CDP calls or flaky connections
• Need post-hoc analysis of debugger session history
• Browser debugging: console errors, network failures, DOM inspection
• Browser automation: navigate, click, type, screenshot
• Performance testing: network throttling, device emulation, coverage
• API mocking: intercept network requests with custom responses

Commands

Start a Session

dbg open <port|host:port>       # attach to --inspect process
dbg run "node <file>"           # spawn with --inspect-brk, connect

Set Breakpoints

dbg b <file>:<line>                  # set breakpoint
dbg b <file>:<line> --if "<cond>"    # conditional breakpoint
dbg bl                               # list all breakpoints
dbg db <id>                          # delete breakpoint

Taps (Logpoints)

A tap is a never-pausing conditioned breakpoint that logs an expression each time the line runs — instrument code without editing it or stopping execution. Works on browser AND node (V8 inspector) sessions.

dbg tap add src/Cart.tsx:42 "user.id"   # log user.id whenever line 42 runs (1-based)
dbg tap add app.js:3 "doubled" --url "app\\.js"  # --url overrides the file-suffix regex (bundles)
dbg tap list                            # all taps (id, file, line, expr, url_regex)
dbg tap hits <id> --tail 20             # the most-recent values this tap captured
dbg tap rm <id>                         # remove the tap + its CDP breakpoint
dbg q "SELECT ts, value FROM tap_hits WHERE tap_id = <id>"

tap add echoes the RESOLVED location ("armed on <url>:<line>") or "arms on script load" when no matching script is loaded yet — never silently pending. The __dbg_tap: console sentinel is routed to tap_hits and suppressed from the user-facing console, after consoleDelta, dbg why, and the timeline.

Flows (Record and Replay)

Flows record user actions on the active visual recorder page and replay them with trusted CDP input, per-step readiness gates, captures, console verdicts, and diff-vs-last-run data.

dbg record http://localhost:3000
dbg flow record checkout
dbg flow stop
dbg flow run checkout --step-timeout 5000
dbg flow list
dbg flow show checkout
dbg q "SELECT * FROM flow_run_steps"

Selector capture prefers unique #id, then [data-testid], then a unique tag/class selector, then a full nth-of-type fallback path. Scroll-only flows are valid: recording a user scroll or window.scrollTo(...) persists a scroll step and replays it against static file:// reports as well as app pages.

Use dbg for CDP-backed debugger state, flight-recorder verdicts, SQL tables, and replayable flows. The CLI package installs @douglance/play as a normal dependency, so general Playwright-runner workflows with durable named sessions, accessibility snapshots, and smart selector helpers are available without depending on ad hoc global setup.

Control Execution

dbg c                           # continue (blocks until next pause)
dbg n                           # step over
dbg s                           # step into
dbg o                           # step out
dbg pause                       # pause execution
dbg status                      # check connection/pause state

Inspect State (SQL)

dbg q "SELECT * FROM frames"
dbg q "SELECT name, type, value FROM vars WHERE frame_id = 0"
dbg q "SELECT * FROM scripts WHERE file LIKE '%<pattern>%'"
dbg q "SELECT name, value FROM props WHERE object_id = '<id>'"
dbg q "SELECT * FROM console"
dbg q "SELECT * FROM exceptions"

SQL syntax: SELECT [cols | *] FROM <table> [WHERE ...] [ORDER BY col [ASC|DESC]] [LIMIT n]

WHERE operators: =, !=, <, >, <=, >=, LIKE, AND, OR, ()

Evaluate and View Source

dbg e "<expression>"            # evaluate, bare value output
dbg src                         # source around current location
dbg src <file> <start> <end>    # specific line range

Diagnostics

dbg trace                       # recent CDP send/recv with latency
dbg trace 50                    # limit to 50 messages
dbg health                      # probe target, report latency (ms)
dbg reconnect                   # reconnect to last websocket URL

Session Lifecycle

dbg restart                     # respawn, reconnect, restore breakpoints
dbg close                       # disconnect (kills target if started via run)

Multi-Session (Frontend + Backend)

dbg run "node server.ts"                             # auto-named s0
dbg open 9229 be                                     # positional name (backend)
dbg open 9222 fe --type page                        # named "fe", targets browser tab
dbg b server.ts:42 --session be                      # breakpoint on backend
dbg navigate "http://localhost:3000/login" --session fe
dbg q "SELECT * FROM console WHERE type = 'error'" --session fe
dbg q "SELECT * FROM vars" --session be

Browser Navigation

dbg navigate <url>                     # go to URL
dbg navigate reload                    # reload current page
dbg navigate back                      # go back in history
dbg navigate forward                   # go forward in history

Browser Interaction

dbg click "<selector>"                 # click element by CSS selector
dbg type "<selector>" "<text>"         # type into element
dbg select "<selector>" "<value>"      # select dropdown option
dbg screenshot                         # capture PNG (returns base64)
dbg screenshot /tmp/page.png           # save to file

Browser Query Tables

dbg q "SELECT method, url, status FROM network WHERE status >= 400"
dbg q "SELECT * FROM dom WHERE selector = 'h1'"
dbg q "SELECT * FROM cookies"
dbg q "SELECT key, value FROM storage WHERE type = 'local'"
dbg q "SELECT * FROM performance"
dbg q "SELECT * FROM console WHERE type = 'error'"

Network Mocking

dbg mock "/api/users" '{"users":[]}'              # intercept with mock response
dbg mock "/api/data" '{}' --status 500             # mock error response
dbg unmock "/api/users"                            # remove specific mock
dbg unmock                                         # clear all mocks

Device Emulation & Throttling

dbg emulate iphone-14                  # emulate iPhone 14 (390x844)
dbg emulate ipad                       # emulate iPad (810x1080)
dbg emulate pixel-7                    # emulate Pixel 7
dbg emulate reset                      # reset to default

dbg throttle 3g                        # simulate 3G network
dbg throttle slow-3g                   # simulate slow 3G
dbg throttle offline                   # simulate offline
dbg throttle off                       # disable throttling

Code Coverage

dbg coverage start                     # begin tracking JS + CSS usage
# ... interact with the page ...
dbg coverage stop
dbg q "SELECT url, used_pct FROM coverage ORDER BY used_pct ASC"

Visual Flight Recorder (record → edit → after)

dbg record http://localhost:3000     # daemon launches headless Chrome, keeps recording
dbg record http://localhost:3000 --viewport 1280x720   # WxH or preset (desktop|tablet|mobile)
dbg mark before-fix                  # stamp a named epoch (auto-epochs happen on edit bursts)
# ... edit code; saved files + vite HMR modules annotate captures automatically ...
dbg after --json                     # capture now, diff vs anchor: pixels + component blame
                                     #   + style deltas + new console/network errors + report.html
dbg after --at mark:before-fix       # explicit anchors: capture:<id> | mark:<name> | time:<ts|10m> | file:<path>
dbg after --perf-budget lcp=2500,cls=0.1   # perfDelta (ΔLCP/ΔCLS/bundle); nonzero exit on breach (--skip-perf to omit)
dbg why                              # blame the most recent error → ranked edit/epoch/commit/prompt
dbg why "coupon"                     # blame the most recent error whose text contains "coupon"
dbg timeline                         # filmstrip HTML of every capture with annotations
dbg replay <captureId>               # restore a capture's URL/scroll in the recorder page
dbg record --status                  # captureCount, epochCount, lastCaptureTs
dbg record --stop                    # end recording, kill managed Chrome

dbg after --json returns pair (diffPercent, diffPixels, clusters), regions (diff clusters blamed to React component names, or tag.class on non-React pages; causal: true when the component's file was just edited), styleChanges (computed-style deltas like padding-top: 8px → 40px), consoleDelta / exceptionDelta / networkDelta, and reportPath (self-contained HTML with side-by-side / wipe / onion-skin / diff-overlay views). Add --open for humans.

Verdict sections (Plan V) — dbg after also returns:

• networkDiff — requests grouped by method + normalized URL pattern (numeric ids / uuids collapsed to :id), classified added / removed / statusChanged / durationDelta (anchor window vs after window).
• stateChanges — added/removed/changed local & sessionStorage keys (JSON-parsed values), from the per-capture state_snapshots.
• a11yNew — accessibility issues present in the after capture but not the anchor (five rules: missing alt, control/button without name, control without label, duplicate landmark, missing document title).
• perfDelta (Plan X) — ΔLCP, ΔCLS (new layout shift during flows), new longtask count, ΔJSHeap, Δbundle_bytes, and interaction count/max-duration. Sourced from a buffered PerformanceObserver (LCP/CLS/longtask/paint/event) plus a per-capture Performance.getMetrics subset (JSHeapUsedSize, JSHeapTotalSize, Nodes, Documents, JSEventListeners, LayoutCount, RecalcStyleCount) and a per-nav Script/Stylesheet bundle_bytes total. nav_id increments per main-frame navigation observed by the daemon; entries are stamped with the nav_id current at receipt. The recorder loop is HMR-alive (not reload-heavy), so CLS/LCP are per-hard-nav — they reset only on real document navigations. Rows land in the perf_samples table.

dbg why [substring] walks the substrate back from the target error to ranked causes and returns a why verdict + one-line answer, e.g. "'Cannot read x of undefined' first seen …, 2.1s after you saved src/Cart.tsx (epoch 4: 'before-fix', prompt: 'add coupon field')". Ranking = edit recency + file-in-stack-trace bonus; plus the enclosing epoch, nearest commit, and active agent prompt. Reads errors from the persisted event store, so it works after record --stop (subject to the events TTL).

Each after section is individually skippable to stay fast: --skip-network, --skip-state, --skip-a11y, --skip-perf (measured after ≈ 220ms with all on — perfDelta is pure store reads and adds no CDP round-trip to after, so no budget bump was needed; the only cold cost is one Performance.getMetrics call per capture, best-effort and parallel to snapshot work). --perf-budget lcp=2500,cls=0.1 fails (nonzero exit) when the after-side delta breaches a budget (keys: lcp, cls, longtask, jsheap, bundle).

Deliberate Captures (shoot)

dbg shoot http://localhost:3000 --selector "#nav" --states hover,focus
dbg shoot src/Button.tsx --props '{"variant":"primary"}'   # esbuild harness renders
                                     # the component with YOUR react-dom at #dbg-root
dbg shoot http://localhost:3000 --viewport mobile --full-page
dbg shoot http://localhost:3000 --out screenshots/ --name nav-check

Viewport presets: desktop (1280x800), tablet (768x1024), mobile (390x844), or any WxH. Each state produces its own PNG under .dbg/shots/ (base name for the default state, name@hover.png etc. for forced states); shots also land as captures rows under session shoot. prefers-reduced-motion is emulated so animations don't pollute pixels. For Storybook, shoot the story URL directly (e.g. dbg shoot 'http://localhost:6006/iframe.html?id=button--primary').

Apple Device / Simulator (iOS, tvOS, watchOS, visionOS)

dbg devices                            # list all devices + simulators
dbg devices --platform ios             # filter by platform
dbg apps <device-id>                   # list installed apps on a device
dbg attach com.example.myapp           # attach to running app
dbg attach com.example.myapp --launch  # launch app then attach
dbg attach com.example.myapp --device sim:"iPhone 15" --launch
dbg attach com.example.myapp --device device:<udid> --launch

On physical devices, if attach fails without --launch, dbg automatically retries with --launch. After a --launch attach, dbg auto-continues past dyld into app code (lands at main).

Native Debug (LLDB Sessions)

dbg attach-lldb ./a.out                # launch local binary via lldb-dap
dbg registers                          # show CPU registers
dbg memory <addr> <len>                # read process memory
dbg disasm                             # disassemble at current location
dbg disasm <addr>                      # disassemble at specific address

Note: registers on physical devices returns a friendly error instead of crashing the session if the adapter disconnects.

Target Management

dbg targets 9222                       # list all debuggable tabs
dbg open 9222 --type page              # connect to first page target
dbg open 9222 --target <id>            # connect to specific tab

Virtual Tables

Debugger State

Table	Description	Required Filter
frames	Call stack	—
scopes	Scope chains	—
vars	Variables (frame 0, skips global)	—
this	this binding per frame	—
props	Object properties	object_id
proto	Prototype chain	object_id
breakpoints	All breakpoints	—
scripts	Loaded scripts	—
source	Source lines	file or script_id
console	Console messages	—
exceptions	Thrown exceptions	—
async_frames	Async stack traces	—
listeners	Event listeners	object_id

Event Log

Table	Description
events	Raw event log (daemon, CDP, connections)
cdp / cdp_messages	CDP messages with direction and latency
connections	Connection lifecycle (connect, disconnect, reconnect)
events_stream	CDP event-stream debug view (stream/phase/severity classification, windowing, coalescing)

Event log queries:

dbg q "SELECT direction, method, latency_ms FROM cdp ORDER BY id DESC LIMIT 20"
dbg q "SELECT method, latency_ms FROM cdp WHERE latency_ms > 100"
dbg q "SELECT ts, event, session_id FROM connections"
dbg q "SELECT ts, stream, severity, method, entity, summary FROM events_stream ORDER BY ts DESC LIMIT 120"
dbg q "SELECT ts, stream, severity, method, summary FROM events_stream WHERE include = 'errors' ORDER BY ts DESC LIMIT 80"
dbg q "SELECT ts, stream, method, summary FROM events_stream WHERE detail = 'full' AND window_ms = 5000 ORDER BY ts DESC LIMIT 200"

Note: the timeline name now refers to the unified cross-source stream (see Unified Timeline below). The CDP event-stream view was renamed to events_stream; its schema and behavior are unchanged.

Event-backed tables (events, cdp, connections, events_stream, timeline) can be queried even when no debug session is active.

Native Tables (LLDB/DAP Sessions)

Table	Description	Required Filter
registers	CPU register values	—
memory	Process memory bytes	address, length
disassembly	Disassembled instructions	address
threads	Active threads	—
modules	Loaded modules/libraries	—
watchpoints	Hardware watchpoints	—
signals	Signal information	—

Browser Tables

Table	Description	Required Filter
network	HTTP requests/responses	—
network_headers	Request/response headers	request_id
network_body	Response body content	request_id
page_events	Page lifecycle events	—
dom	DOM elements by selector	selector
styles	Computed CSS styles	node_id
performance	Performance metrics	—
cookies	Browser cookies	—
storage	localStorage/sessionStorage	type (local/session)
ws_frames	WebSocket messages	—
coverage	JS/CSS code coverage	—

Browser table queries:

dbg q "SELECT method, url, status, duration_ms FROM network"
dbg q "SELECT name, value FROM network_headers WHERE request_id = '<id>'"
dbg q "SELECT body FROM network_body WHERE request_id = '<id>'"
dbg q "SELECT node_id, tag, text FROM dom WHERE selector = '.error'"
dbg q "SELECT name, value FROM styles WHERE node_id = 42"
dbg q "SELECT name, value FROM cookies WHERE domain LIKE '%example%'"
dbg q "SELECT key, value FROM storage WHERE type = 'local'"

Recorder & Dev Tables

Every development signal is stored on one epoch-milliseconds timeline (UTC ts INTEGER across every table), so screenshots, file edits, git commits, and agent history all join on ts directly.

Table	Description	Source
captures	Screenshot capture metadata (url, hash, epoch_id, tier)	recorder store
epochs	Epoch markers (auto on edit bursts, or named via dbg mark)	recorder store
diffs	dbg after pixel-diff results	recorder store
regions	Blamed diff clusters (diff_id)	recorder store
edits	First-class file-edit stream — one row per fs-watch event (ts, path, epoch_id, session_id), tagged with the current epoch	recorder store
state_snapshots	Per-capture local/sessionStorage dump (capture_id, kind, data JSON)	recorder store
a11y_issues	Per-capture accessibility issues (capture_id, rule, selector, detail)	recorder store
taps	Logpoints (id, session_id, file, line, expr, url_regex, enabled)	debug store
tap_hits	Each tap fire (tap_id, ts, value)	debug store
flows	Recorded user flows (id, ts, name, url, session_id)	recorder store
flow_steps	Recorded flow actions (flow_id, idx, kind, selector, fallback_path, value)	recorder store
flow_runs	Flow replay summaries (status, steps_total, steps_passed)	recorder store
flow_run_steps	Per-step replay verdicts (status, capture_id, error, diff_percent)	recorder store
commits	git log (hash, short_hash, ts, author, summary, files); default repo = cwd, override WHERE repo = '/abs' (500 most recent)	git
agent_prompts	Claude Code prompts (ts, display, project); default-scoped to cwd, WHERE project = '<slug>' widens	~/.claude/history.jsonl
agent_sessions	Per-session transcript summaries (ts_first, ts_last, title, message_count)	~/.claude/projects/<slug>
timeline	Unified union over all of the above	union

dbg q threads your shell's cwd to the daemon, so commits / agent_prompts / agent_sessions scope to your project, not the daemon's.

Unified Timeline

timeline is a single ts-ordered union (columns: ts, kind, session_id, label, ref_id, detail). kind ∈ capture (label=url) · mark/epoch · edit (label=path) · error / exception (label=text) · netfail (label=method url status) · commit (label=summary, ref_id=short_hash) · prompt (label=first 120 chars) · diff. It defaults to the last 24h unless a WHERE constrains ts.

Multi-table joins, BETWEEN, GROUP BY, and aliases now run as real SQL: queries that reference more than one table (or that the single-table engine can't parse) are materialized into an in-memory SQLite DB and executed there.

# 1. Causal chain — which prompt caused the edit that produced an error
dbg q "SELECT p.display, e.path, c.url, x.label
       FROM agent_prompts p
       JOIN edits e ON e.ts BETWEEN p.ts AND p.ts + 600000
       JOIN captures c ON c.ts BETWEEN e.ts AND e.ts + 30000
       JOIN timeline x ON x.kind = 'error' AND x.ts BETWEEN e.ts AND e.ts + 5000
       ORDER BY e.ts"

# 2. Errors within 5s of each edit
dbg q "SELECT e.path, e.ts, t.label
       FROM edits e
       JOIN timeline t ON t.kind = 'error' AND t.ts BETWEEN e.ts AND e.ts + 5000
       ORDER BY e.ts"

# 3. Commits with no subsequent capture (shipped but never re-recorded)
dbg q "SELECT c.short_hash, c.summary
       FROM commits c
       WHERE (SELECT COUNT(*) FROM captures cap WHERE cap.ts > c.ts) = 0"

Cold-scan costs: commits shells out to git log (~50–150ms). agent_prompts reads one JSONL file (~100ms cold). agent_sessions scans a project's transcript dir — ~0.7s cold on a large history, ~50ms warm (results are cached by path+mtime+size). edits / captures / epochs / diffs are indexed store reads (sub-ms). dbg timeline HTML now interleaves commit + prompt chips between frame cards by ts.

Network failures ride the timeline as the netfail kind, reconstructed from the raw events table (whose ts is wall-clock epoch-ms at receipt — not CDP's monotonic Network.*.timestamp), so they honor the unified ts contract.

Output Format

• TOON (compact, token-efficient) by default for every command
• JSON: dbg q "SELECT * FROM frames" --json (or --format json)
• --format toon|json|yaml|md|jsonl picks the encoding explicitly
• Flow commands return a structured object (status: paused, file, line, function)
• Exit 0 success, 1 error. Parse stdout, check exit code.

Object Drill-Down Pattern

# 1. Get object_id from variables
dbg q "SELECT name, object_id FROM vars WHERE name = 'config'"

# 2. Inspect its properties
dbg q "SELECT name, type, value FROM props WHERE object_id = '<id>'"

# 3. Keep drilling into nested objects
dbg q "SELECT name, value FROM props WHERE object_id = '<child_id>'"

Example Workflow

# Scenario: Function returns unexpected value
dbg run "node app.ts"
dbg b app.ts:42
dbg c
dbg q "SELECT name, type, value FROM vars WHERE frame_id = 0"
dbg e "config.settings"
dbg q "SELECT id, function, file, line FROM frames LIMIT 5"
dbg n
dbg q "SELECT name, value FROM vars WHERE name = 'result'"
dbg close

Browser Debug Loop

# Scenario: Login page is broken
dbg open 9222 --type page
dbg navigate "http://localhost:3000/login"
dbg q "SELECT type, text FROM console WHERE type = 'error'" --json
dbg q "SELECT method, status, url FROM network WHERE status >= 400" --json
dbg q "SELECT node_id, text FROM dom WHERE selector = '.error-message'" --json
# ... identify and fix the bug in code ...
dbg navigate reload
dbg q "SELECT * FROM console WHERE type = 'error'" --json
dbg screenshot /tmp/login-fixed.png
# Verify: zero errors, page renders correctly
dbg close

Environment Variables

Variable	Default	Description
DBG_SOCK	/tmp/dbg.sock	Unix socket path for daemon communication
DBG_EVENTS_DB	/tmp/dbg-events.db	SQLite event store path (set a persistent path to keep history across runs)

Postmortem Timeline Workflow

# Keep one persistent event DB for repeated runs
export DBG_EVENTS_DB="$HOME/.dbg/history.db"

# Run dbg workflows as usual (open/run/navigate/etc.)
# Later, even with no active session:
dbg q "SELECT ts, stream, severity, method, summary FROM timeline ORDER BY ts DESC LIMIT 200"
dbg q "SELECT ts, method, error FROM cdp WHERE error != '' ORDER BY ts DESC LIMIT 100"

Native Device Debug Loop

# Scenario: Debug an iOS app on a physical device
dbg devices --platform ios
dbg apps <device-id>
dbg attach com.example.myapp               # auto-retries with --launch if needed
# Now paused in app code (main), not dyld
dbg b ViewController.swift:42
dbg c
dbg q "SELECT name, value FROM vars WHERE frame_id = 0"
dbg n
dbg e "self.viewModel.state"
dbg close

Visual Before/After Loop (agents)

The recorder gives every code edit a visual paper trail — no window, no human:

dbg record http://localhost:3000     # 1. start recording (background, headless)
dbg mark attempt-1                   # 2. stamp where you are
# 3. edit code — file saves and HMR updates annotate captures automatically
dbg after --json                     # 4. verdict: pixel diff % + blamed components
                                     #    + style deltas + new errors, in one JSON
# 5. iterate; when done, show report.html to the human (dbg after --open)
dbg record --stop

"Before" always exists retroactively: the anchor defaults to the last capture at the newest epoch, so you can edit first and ask questions later.

Performance: sub-second after-verdicts are the design target, so poll freely. CI-enforced budgets (test/perf.test.ts): record cold start < 4s, mark < 500ms, after < 1.5s, timeline < 1s, shoot < 5s, mutation → capture row < 1.5s.

The dbg after --json verdict shape:

{
  "ok": true,
  "pair": { "name": "capture 1 → capture 3", "baseline": {"captureId": 1, "ts": 0},
            "after": {"captureId": 3, "ts": 0}, "diffPercent": 27.8,
            "diffPixels": 133588, "dimensionsChanged": false, "clusters": 2 },
  "regions": [ { "box": {"x": 8, "y": 61, "w": 480, "h": 280},
                 "label": "ColorCard", "component": "ColorCard",
                 "file": null, "causal": true } ],
  "styleChanges": [ { "selector": "div.color-card", "prop": "padding-top",
                      "before": "8px", "after": "40px" } ],
  "consoleDelta": { "new": [ {"type": "error", "text": "boom", "ts": 0} ] },
  "exceptionDelta": { "new": [] },
  "networkDelta": { "failed": [] },
  "reportPath": ".dbg/recordings/report.html"
}

Retention: capture history is bounded — metadata rows are kept forever, but pixels decay oldest-first once past the budgets (200 full frames / 100MB per session; --max-frames, --max-bytes). Decayed frames become ≤320px thumbs, then metadata-only (captures.tier = 'full'|'thumb'|'meta'). Epoch anchors, diff baselines, and the newest capture never decay, so dbg after anchors stay diffable; a decayed --at anchor returns an error suggesting the nearest full capture. Raw CDP events rows expire after 30 minutes (most-recent 50k kept; --events-ttl). Check usage with dbg record --status (diskBytes, fullFrames/thumbFrames/metaFrames, eventsRows).

Recorder SQL tables (join them with console, network, etc.):

dbg q "SELECT ts, changed_files, hmr_modules, epoch_id FROM captures"  # visual git log
dbg q "SELECT id, ts, name, auto FROM epochs"                          # marks + edit bursts
dbg q "SELECT name, diff_percent, report_path FROM diffs"              # every after verdict
dbg q "SELECT diff_id, component, causal FROM regions"                 # who changed the pixels

Tips

• Every dbg call is independent — no session to manage
• Breakpoints persist across dbg restart
• Use SQL WHERE clauses to filter large result sets
• dbg trace shows CDP/DAP latency to diagnose slow operations
• dbg health quickly verifies the target is responsive
• dbg reconnect recovers from dropped websocket connections
• For browser pages, use dbg open <port> --type page to skip Node.js targets
• dbg targets <port> lists all available tabs — use --target <id> for specific ones
• Network mocks survive page reload (Fetch domain stays enabled)
• Screenshot returns base64 PNG — agents can "see" the page
• Combine DOM queries + screenshots for both structural and visual verification
• Physical device attach auto-retries with --launch if needed
• After --launch, dbg auto-continues past dyld to main
• registers on physical devices fails gracefully (no session crash)

Success Criteria

• Root cause identified and documented
• Relevant variables, stack frames, or object state captured
• Fix validated by re-running with breakpoints at the fix point