Description of the bug
The Emulation examples in skills/chrome-devtools-cli/SKILL.md include chrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0x0". The --geolocation value must be <latitude>,<longitude>; with "0x0" the command fails with Invalid longitude "undefined" and neither the geolocation nor the CPU throttling in the same call is applied. The example is identical in the 1.10.1 npm package and on main at b2f522c.
Actual behavior
Step 3 printed Invalid longitude "undefined". Longitude must be a number between -180 and 180. (exit status 0 on 1.10.1; 1 on main b2f522c, same message with an Error: prefix). "0x0" has no comma, so the whole string becomes the latitude (Number("0x0") is 0 as a hex literal) and the longitude is undefined. The step 4 control printed Emulation configured successfully, Emulating geolocation: latitude=0, longitude=0 and Emulating CPU throttling: 4x slowdown. From source (not separately observed): the transform throws during argument parsing, before the handler runs, so the CPU throttling in the failing call is not applied either.
Reproduction
Executed on macOS against the published 1.10.1 package and a local build of main b2f522c, with usage statistics and update checks disabled and XDG_RUNTIME_DIR pointed at a scratch directory so the CLI daemon socket was private to the test.
npm i --prefix /tmp/x chrome-devtools-mcp@1.10.1.chrome-devtools start --no-usage-statistics --no-performance-crux (from /tmp/x/node_modules/.bin).- Run the skill line verbatim:
chrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0x0".
- Control:
chrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0,0".
chrome-devtools stop.
Expectation
The skill example should configure the emulation its comment describes ("Emulate CPU throttling and geolocation"). The emulate tool documents geolocation as "<latitude>,<longitude>" (src/tools/emulation.ts; docs/tool-reference.md, emulate), parsed by geolocationTransform in src/tools/ToolDefinition.ts, which splits on ,.
MCP configuration
CLI daemon started with --no-usage-statistics --no-performance-crux
Chrome DevTools MCP version
1.10.1 (npm) and main b2f522c (local build)
Chrome version
154.0.8037.93 (stable, headless, isolated)
Node version
v24.21.0
Operating system
macOS
Evidence
- Expected source:
src/tools/emulation.ts (geolocation description) and geolocationTransform in src/tools/ToolDefinition.ts, at tag chrome-devtools-mcp-v1.10.1 and main b2f522c.
- Failure source:
skills/chrome-devtools-cli/SKILL.md:82 (identical in 1.10.1 and main b2f522c) and the CLI output quoted under Actual behavior.
- Evidence provenance: observed
- Local verification: reproduced
- Reproduction completeness: complete
Fix check
Failing now: running the skill's geolocation example verbatim prints the invalid-longitude error. Restored: the skill's geolocation example, run verbatim, prints Emulation configured successfully with the geolocation and CPU throttling it describes, as the step 4 control does. Control: emulate keeps rejecting a geolocation string that is not <latitude>,<longitude>.
Description of the bug
The Emulation examples in
skills/chrome-devtools-cli/SKILL.mdincludechrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0x0". The--geolocationvalue must be<latitude>,<longitude>; with"0x0"the command fails withInvalid longitude "undefined"and neither the geolocation nor the CPU throttling in the same call is applied. The example is identical in the 1.10.1 npm package and onmainat b2f522c.Actual behavior
Step 3 printed
Invalid longitude "undefined". Longitude must be a number between -180 and 180.(exit status 0 on 1.10.1; 1 onmainb2f522c, same message with anError:prefix)."0x0"has no comma, so the whole string becomes the latitude (Number("0x0")is 0 as a hex literal) and the longitude is undefined. The step 4 control printedEmulation configured successfully,Emulating geolocation: latitude=0, longitude=0andEmulating CPU throttling: 4x slowdown. From source (not separately observed): the transform throws during argument parsing, before the handler runs, so the CPU throttling in the failing call is not applied either.Reproduction
Executed on macOS against the published 1.10.1 package and a local build of
mainb2f522c, with usage statistics and update checks disabled andXDG_RUNTIME_DIRpointed at a scratch directory so the CLI daemon socket was private to the test.npm i --prefix /tmp/x chrome-devtools-mcp@1.10.1.chrome-devtools start --no-usage-statistics --no-performance-crux(from/tmp/x/node_modules/.bin).chrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0x0".chrome-devtools emulate 1 --cpuThrottlingRate 4 --geolocation "0,0".chrome-devtools stop.Expectation
The skill example should configure the emulation its comment describes ("Emulate CPU throttling and geolocation"). The
emulatetool documentsgeolocationas "<latitude>,<longitude>" (src/tools/emulation.ts;docs/tool-reference.md,emulate), parsed bygeolocationTransforminsrc/tools/ToolDefinition.ts, which splits on,.MCP configuration
CLI daemon started with
--no-usage-statistics --no-performance-cruxChrome DevTools MCP version
1.10.1 (npm) and
mainb2f522c (local build)Chrome version
154.0.8037.93 (stable, headless, isolated)
Node version
v24.21.0
Operating system
macOS
Evidence
src/tools/emulation.ts(geolocationdescription) andgeolocationTransforminsrc/tools/ToolDefinition.ts, at tagchrome-devtools-mcp-v1.10.1andmainb2f522c.skills/chrome-devtools-cli/SKILL.md:82(identical in 1.10.1 andmainb2f522c) and the CLI output quoted under Actual behavior.Fix check
Failing now: running the skill's geolocation example verbatim prints the invalid-longitude error. Restored: the skill's geolocation example, run verbatim, prints
Emulation configured successfullywith the geolocation and CPU throttling it describes, as the step 4 control does. Control:emulatekeeps rejecting a geolocation string that is not<latitude>,<longitude>.