v0.1.11913 Aug 2026·DevTools, Tabs & interface

DevTools: a Sources panel with a clickable line gutter

The debugger stops being blind. Until now you set a breakpoint by typing a line NUMBER into a box, with no way to see what was on that line. Now the Debugger tab shows the running script itself, with a line gutter you click to set or clear a breakpoint - and the current pause line lights up as you step. It renders the exact source the engine parsed, so line N in the gutter is line N a breakpoint lands on, and it only offers a breakpoint on a line that begins a statement (the same compile-time line table stepping already uses), so there is no way to click a line that could never fire. It is captured only while the debugger is enabled, so a page that is not being debugged is untouched and the whole conformance suite is unchanged. DevTools moves 31 to 33; overall holds at 51 - the piece that lifts the floor, a WebSocket transport that lets external tools like Puppeteer attach, is the remaining step.

Parity with the reference browser

74overall, as of v0.1.343

Web APIs / DOM surface42

Security architecture66

GPU / graphics acceleration68

DevTools / extensions72

Networking85

Media85

Accessibility85

Real-world site compatibility99

HTML parsing100

CSS parsing + selectors100

Layout: block / flex / grid / tables / writing-modes100

Paint + visual100

JavaScript language100

JavaScript performance (JIT)100

HTML parsing100

What changed 3 changes

Tabs & interface	The running script is rendered with a line gutter: Debugger.getScriptSource returns the exact text the engine parsed and compiled (so gutter line N is the line a breakpoint fires on), and Debugger.getPossibleBreakpoints returns the distinct lines that begin a statement, read straight off the compile-time line table that breakpoints and stepping already index. A blank line, a comment or the middle of an expression is greyed out and unclickable - by construction there is no reachable "set a breakpoint that silently never fires" state.
DevTools	Click a line in the gutter to toggle its breakpoint: it drives the same setBreakpointByUrl / removeBreakpoint path the numeric box does (a new single-line clear alongside the existing clear-all), so a gutter click and a typed line number produce the identical breakpoint set, and the current pause line is highlighted while interactive stepping is on. The source and its breakpoint-able lines are captured only when the Debugger domain is enabled - a normal page run early-returns and pays nothing.
Tabs & interface	Wired end to end and gate-clean: two engine natives (__debug_script_source / __debug_possible_lines), two CDP methods (Debugger.getScriptSource / getPossibleBreakpoints), and a Sources block in the visual Debugger panel that polls the source deduped by content so the gutter only re-renders when the script actually changes. 2 new property tests (24 in the debugger module), conformance gate 6375/6375 with native-JIT and no-nanbox green. Honest remaining floor: a multi-file Sources tree and the WebSocket CDP transport for external tooling. Research note docs/devtools-sources.md.