docs: update skill docs for v0.16.0 upstream changes

Add CrUX field data, source-mapped stacks, Error.cause chains,
and Error object formatting to skill documentation.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: omalleyandy

skills/chrome-devtools/SKILL.md

@@ -74,7 +74,7 @@ The server does not inject code into the page; it uses DevTools network data. Yo
 | List HTTP/WebSocket requests | `list_network_requests` (optional `resourceTypes: ['websocket']`) |
 | Inspect one request/response | `get_network_request` (reqid, optional file paths for bodies) |
 | Console errors/warnings | `list_console_messages` (optional `types`), `get_console_message` |
-| Performance / CWV | `performance_start_trace`, `performance_stop_trace`, `performance_analyze_insight` |
+| Performance / CWV | `performance_start_trace`, `performance_stop_trace`, `performance_analyze_insight` (includes CrUX field data) |
 | Emulation | `emulate` (viewport, userAgent, networkConditions, etc.), `resize_page` |
 
 See [Tool reference](../../docs/tool-reference.md) for full parameters.
@@ -85,11 +85,24 @@ Tool responses are shaped by internal formatters. You don’t call them directly
 
 - **SnapshotFormatter**: Turns the a11y tree into the text snapshot with `uid`s and optional “selected in DevTools” hint. Use `verbose: true` on `take_snapshot` for more detail.
 - **NetworkFormatter**: Formats request/response (URL, status, headers, body). Large bodies can be truncated or written to `requestFilePath`/`responseFilePath`.
-- **ConsoleFormatter**: Formats console messages (level, text, stack, resolved arguments when detailed data is requested).
-- **IssueFormatter**: Formats DevTools “issues” (e.g. deprecations, violations) when included in responses.
+- **ConsoleFormatter**: Formats console messages (level, text, stack, resolved arguments when detailed data is requested). Error objects logged via `console.log(new Error(...))` now include the full message, source-mapped stack trace (1-based line/column), and `Error.cause` chain (shown as nested "Caused by:" sections).
+- **IssueFormatter**: Formats DevTools "issues" (e.g. deprecations, violations) when included in responses.
 
 A full **Network & Console breakdown** (data flow, collectors, filter options, what you see in responses) is in [network-and-console-breakdown.md](./network-and-console-breakdown.md).
 
+## Performance traces and CrUX field data
+
+Performance traces now include **CrUX (Chrome User Experience Report)** real-user field metrics alongside lab data:
+
+- **Metrics shown**: LCP (with breakdown: TTFB, load delay, load duration, render delay), INP, CLS
+- **Scope**: Data may be for the specific URL or the entire origin, indicated in the output
+- **Privacy**: URLs from traces are sent to Google's CrUX API to fetch field data
+- **Disable**: Start the server with `--no-performance-crux` to opt out of CrUX data
+
+## Error debugging improvements
+
+Stack traces for uncaught errors and `console.log(Error)` are now **source-mapped** (showing original file paths and 1-based line/column numbers instead of minified bundles). Error objects also display their full **Error.cause** chain as nested "Caused by:" sections with their own stack traces.
+
 ## Telemetry
 
 Google collects usage statistics (e.g. tool invocation success, latency, environment) to improve the server. Collection is **on by default**.

skills/chrome-devtools/network-and-console-breakdown.md

@@ -118,13 +118,35 @@ Example: only errors and issues → `types: ['error', 'issue']`.
 - **Single message (detailed)** from `get_console_message`:
   - **Console message**: ID, type, message text, **Arguments** (resolved values), **Stack trace** (with file:line when available).
   - **Issue**: ID, description (markdown), “Learn more” links, **Affected resources** (e.g. request reqid, element uid).
-  - **Uncaught error**: ID, message, stack.
+  - **Uncaught error**: ID, message, **source-mapped stack trace** (1-based line/column), and **Error.cause chain** (nested "Caused by:" sections, each with its own message and stack).
+
+### Error object formatting (v0.16.0+)
+
+When an Error object is logged via `console.log(new Error(...))` or thrown as an uncaught exception, the ConsoleFormatter now extracts:
+
+- **Message**: The error message string.
+- **Source-mapped stack trace**: Stack frames are resolved through source maps, showing original file paths and 1-based line/column numbers instead of minified/compiled references.
+- **Error.cause chain**: If the error has a `.cause`, it's shown as a "Caused by:" section with its own message and stack. Chains are followed recursively.
+
+Example detailed output for an uncaught error with a cause chain:
+```
+Message: error> Uncaught Error: foo failed
+### Stack trace
+at Iife (main.js:18:11)
+at <anonymous> (main.js:14:1)
+Caused by: Error: bar failed
+at foo (main.js:10:11)
+...
+Caused by: Error: b00m!
+at bar (main.js:3:9)
+...
+```
 
 ### Formatters (internal)
 
 - **ConsoleFormatter** (`formatters/ConsoleFormatter.ts`):
   - **Summary**: `toString()` → `msgid=X [type] text (N args)`.
-  - **Detailed**: `toStringDetailed()` → ID, message, Arguments, Stack trace. For detailed, it can resolve `args` via `jsonValue()` and resolve stack via DevTools (when available).
+  - **Detailed**: `toStringDetailed()` → ID, message, Arguments, Stack trace. For detailed, it can resolve `args` via `jsonValue()` and resolve stack via DevTools (when available). Error-subtype arguments are expanded with message, stack, and cause chain.
 - **IssueFormatter** (`formatters/IssueFormatter.ts`):
   - **Summary**: `toString()` → `msgid=X [issue] title (count: N)`.
   - **Detailed**: `toStringDetailed()` → ID, description, links, affected resources (request id, element uid, etc.).

skills/chrome-devtools/reference.md

@@ -30,7 +30,7 @@ Use this alongside [SKILL.md](./SKILL.md). Full parameter details: [docs/tool-re
 
 ### Performance (3)
 - **performance_start_trace** – `reload`, `autoStop`; optional `filePath` for trace file
-- **performance_stop_trace** – Optional `filePath`
+- **performance_stop_trace** – Optional `filePath`. Now includes **CrUX field data** (LCP with breakdown, INP, CLS) from real users alongside lab metrics. Disable with `--no-performance-crux`.
 - **performance_analyze_insight** – `insightSetId`, `insightName` (from trace results)
 
 ### Network (2)
@@ -43,15 +43,15 @@ Use this alongside [SKILL.md](./SKILL.md). Full parameter details: [docs/tool-re
 - **take_screenshot** – Optional `uid`, `fullPage`, `format`, `quality`, `filePath`
 - **evaluate_script** – `function` (JS function as string), optional `args` (array of `{uid}`). Return value must be JSON-serializable.
 - **list_console_messages** – Optional `pageSize`, `pageIdx`, `types`, `includePreservedMessages`
-- **get_console_message** – `msgid`
+- **get_console_message** – `msgid`. Error objects show source-mapped stacks (1-based line/column) and Error.cause chains.
 
 ## Formatters (internal)
 
 | Formatter | Used for | Notes |
 |-----------|----------|--------|
 | SnapshotFormatter | `take_snapshot` output | Text snapshot with `uid`s; `verbose` adds more a11y data |
 | NetworkFormatter | `list_network_requests`, `get_network_request` | URL, status, headers, body (truncated or saved to file) |
-| ConsoleFormatter | `list_console_messages`, `get_console_message` | Level, text, stack, resolved args |
+| ConsoleFormatter | `list_console_messages`, `get_console_message` | Level, text, source-mapped stack, resolved args, Error.cause chains |
 | IssueFormatter | DevTools issues in responses | Deprecations, violations, etc. |
 
 ## Telemetry