Workspace manager - design

Design B, refined and aligned with the design system of the jupyterlab-extension skill. DQ-21 and DQ-22 were decided by the Star Colonel on 2026-10-29. DQ-02, DQ-04, DQ-05 and DQ-19 were amended by his direction on 2026-10-30, and DQ-23 was added the same day. DQ-28 was added by his direction on 2026-11-01, and DQ-02, DQ-07, DQ-20, DQ-22 and DQ-27 were amended the same day. DQ-29 was decided by the Star Colonel on 2026-11-02, and DQ-02, DQ-05, DQ-10, DQ-18, DQ-21 and DQ-28 were amended the same day. DQ-36 was added by his direction on 2026-11-04, and DQ-02, DQ-28 and DQ-29 were amended the same day; DQ-36 narrows DQ-10. DQ-37 was added the same day, and DQ-06, DQ-07, DQ-21, DQ-24, DQ-30 and DQ-32 were amended with it. DQ-26 was amended the same day by the design system's section divider rule. DQ-26 was amended again on 2026-11-05 by his direction, the last band drawing one line where it meets the status bar. DQ-18, DQ-20, DQ-29 and DQ-31 were amended by his direction on 2026-11-05: the number badge is 18 x 13.5 px and takes its first holder's colour at the 24 % wash, the terminal tooltip always states its workspaces, and the KERNELS and TERMINALS band button opens a shut-down menu. DQ-18 was amended by his direction on 2026-11-06: a held badge draws its outline and number in its holder's colour, the hue at 45 % over --jp-inverse-layout-color1. The same day his direction moved the + New workspace button from the panel header to the WORKSPACES band, left of the eraser (ACC-PANEL-297-NEW-BAND).

1. What the panel is for

The WORKBENCH sidebar replaces the built-in panel Running Terminals and Kernels. It lists every workspace of the server, and inside each workspace its tabs, terminals and kernels, then every kernel, terminal and language server that runs on the server. It is built for a user who runs several projects at once: each project is one workspace, told apart by its workspace colour, and the panel shows what the workspace holds, how old it is and what can be shut down.

2. The panel

The panel is a header band over four section bands. One section is open at a time, and the three lab bands stand at the bottom of the panel only while WORKSPACES is open (DQ-33).

Panel header

• The header is a band 37 px tall on --jp-layout-color2. Its title reads WORKBENCH in --jp-ui-font-size0 at weight 600, uppercase, with 1 px letter spacing, in --jp-ui-font-color1
• Three 24 px buttons follow, in this order: filter, show hidden (an eye) and refresh the four buttons led by new workspace (+) superseded by the owner's 2026-11-06 direction: the + moved to the WORKSPACES band (ACC-PANEL-297-NEW-BAND). Each draws a 14 px glyph in --jp-inverse-layout-color3; hover and active paint --jp-layout-color3, and an active glyph takes --jp-brand-color1
• The + button on the WORKSPACES band opens the New workspace dialog the + in this panel header superseded by the owner's 2026-11-06 direction (ACC-PANEL-297-NEW-BAND): a name, with the keyboard focus, and an optional short description of at most 100 characters, which is the purpose the card shows. Enter creates, Escape closes without a change
• The filter button shows a field under the header. The field finds anything in the panel: workspace names and purposes, tab paths, terminal process names and kernel types. Hiding the field clears the filter, and a clear button sits inside it
• The eye includes the hidden workspaces in the list. It shows an eye with a stroke while hidden workspaces are included
• Refresh reloads workspaces, terminals, sessions and process names; the button is disabled until the requests return. While the panel is visible it reloads by itself every 10 s

Section bands

• Four bands, in this order: WORKSPACES, KERNELS, TERMINALS and LANGUAGE SERVERS. Each carries its count in brackets after the label: WORKSPACES (6), KERNELS (2), TERMINALS (10), LANGUAGE SERVERS (0)
• A band is the reference panel's content-sized ~24 px surface on --jp-layout-color2: 4 px above and below a --jp-ui-font-size0 line, so it stays shorter than the 37 px panel header; hover --jp-layout-color3. The caret is the reference's text glyph, ▾ open and ▸ closed, in a 14 px column in --jp-ui-font-color2 on the 4 px inset; the label at 18 px from the edge in --jp-ui-font-size0 at weight 600, uppercase, with 1 px letter spacing, and the count 6 px after the label in --jp-ui-font-color2. No drop shadow
• WORKSPACES is open by default. A click on a collapsed band opens it and closes the one that was open; a click on the open band closes it, leaving all four closed. The closed set is saved per panel in localStorage, read and written in try/catch (DQ-04)
• The panel body is one flex column of fixed height. An open WORKSPACES section takes the height left between the panel header and the collapsed bands (flex: 1 1 auto; min-height: 0); any other open section is as tall as its rows and shrinks to keep every band in view (flex: 0 1 auto; min-height: 0), and the band below it follows its last row (DQ-33). The open section's body is the only scroll container (overflow-y: auto), with no reserved scrollbar strip (scrollbar-gutter: auto, DQ-05) and no row cap. A collapsed section keeps only its band; KERNELS, TERMINALS and LANGUAGE SERVERS keep their order after WORKSPACES and never scroll out of view. They stand at the panel bottom only while WORKSPACES is open, with nothing below the LANGUAGE SERVERS band and no empty strip of panel background above the bands; while WORKSPACES is folded they follow it from the top and the free height stands below the last band (DQ-23, DQ-33). No axis has two scroll containers
• The end of every band carries a band button. On KERNELS and TERMINALS its name is Shut down and it opens a menu with Shut down all and Shut down detached the single Shut down all dialog on these two bands superseded by the owner's 2026-11-05 direction (ACC-ACCORD-292-SHUTDOWN-MENU); on LANGUAGE SERVERS its name is Shut down all and it opens the confirmation dialog; on WORKSPACES its name is Clean up workspaces (DQ-22) and its glyph is an eraser (DQ-29), and the + New workspace button, the same band button, stands immediately left of it, shown and enabled with the section open or closed; a click, Enter or Space on the + opens the New workspace dialog and never opens or closes the section the eraser as the one WORKSPACES band button superseded by the owner's 2026-11-06 direction (ACC-PANEL-297-NEW-BAND). The button is 22 px square with a 14 px glyph in --jp-inverse-layout-color3, with no background and no border at rest; disabled it keeps that look at opacity 0.4. The band-end glyphs stand in one column under the WORKBENCH Refresh glyph, and the eraser's ink stands as far from the band's top edge as from its bottom edge. A menu entry and the LANGUAGE SERVERS button open a confirmation dialog and stop nothing by themselves. Detached means held by no workspace, and the Shut down detached entry is disabled when the section holds no such item

Workspace card

• Each workspace is one edge tab (DQ-29): a card 2 px from the panel's left edge and 2 px from the right edge of its list, square at the left with a 2 px right radius. The header carries the workspace hue at 24 % and the body the hue at 9.6 %, both mixed over --jp-layout-color1, with no rule between them the 30 % and 12 % mixes superseded by the 2026-11-04 owner order (ACC-PANEL-278-TINT-ALPHA). A workspace with no colour paints the plain surfaces: a --jp-layout-color2 header over a --jp-layout-color1 body
• A 4 px strip is the card's left border in the full-strength hue; this window's card paints the same hue, strip and tints as any other card. The palette is the coloured tabs extension's default palette at 1.4 saturation, with rose 2 degrees pinker, peach 3 points darker, lemon 1 point lighter and 2 degrees cooler, and mint 2 points darker, so rose and peach read apart. The six hues stand once on :root, with no theme branch, and each theme's layout colour sets the tints (DQ-28). The strip and the tints together are what tell workspaces apart
• The first header line carries the triangle, the name with its row count in brackets, the age and the eye. While the card is open a second line carries the purpose; a filter adds the (N of M) line the count chips and the second header button superseded by the 2026-11-04 owner order (ACC-ACCORD-276-NAME-COUNT, ACC-ACCORD-283-NO-DOTS)
• Several cards stay open at once: a triangle opens or closes only its own card and every other open card stays open, and a click on another workspace's header still switches this window (ACC-ACCORD-241-MANY-OPEN). Inside a filter every matching card is open until its triangle closes it, and clearing the filter restores the cards the unfiltered view had open
• The name is --jp-ui-font-size1 at weight 400. The age reads now, Nm ago, Nh ago, Nd ago, Nmo ago or Ny ago, at --jp-ui-font-size0 as a row's time does (DQ-21), and never stands empty; a hidden card shows the word hidden in its place, at the same size. On a coloured card the name, the triangle and the glyphs take --jp-inverse-layout-color0, the count and the purpose --jp-inverse-layout-color1 and the age --jp-inverse-layout-color2 (DQ-29, DQ-37) the age at --jp-inverse-layout-color1 superseded on 2026-11-04; on a plain card the name takes --jp-ui-font-color1 and the age --jp-ui-font-color2. The name and the purpose start at the left edge of the row labels below them
• The row count stands in brackets right after the name: the open tabs plus the terminals. A kernel takes no count and the header carries no count glyph the three count chips with their glyphs superseded by the 2026-11-04 owner order (ACC-ACCORD-276-NAME-COUNT)
• The purpose is the short description of the workspace, at most 100 characters, in --jp-ui-font-color2 on a plain card. It shows while the card is open, and a card with no purpose shows no purpose text
• The eye keeps its place on every card: it hides the workspace, and it is disabled on this window's card. No card header carries a ... button: a right-click on the header, the eye included, opens the workspace menu at the pointer, and the context-menu key on the focused header opens it below the header; a hidden card's header opens no menu. Open workspace and Clear workspace are items of that menu (DQ-34) the ... button and the Close all tabs label superseded by the 2026-11-04 owner order (ACC-ACCORD-283-NO-DOTS, ACC-ACCORD-284-CLEAR-WORKSPACE)
• This window's card carries a 2 px --jp-brand-color2 outline inside its own box (outline-offset: -2px) and no other mark, so the card loses no band to the section body's clip (DQ-19)

Rows

• The open card lists its documents and terminals as one flat list with no group label (DQ-29): a terminal is a row with its glyph and process, and a kernel rides on its document's row. The KERNELS and TERMINALS sections stay, so a background terminal or a headless kernel with no tab stays visible and can be shut down there
• A KERNELS row in a band carries a status dot with its word (idle, busy or unknown), a name, its memory and a time the memory on selection only superseded by the 2026-11-04 owner order (ACC-KERNEL-281-ROW-MEMORY). A row in a card carries a 16 px type icon, a name and, where one is known, the time of its last activity; a document with a running kernel adds the status dot with its word, and a terminal adds its process
• A section row and a plain card's row are neutral (DQ-21): the name is --jp-ui-font-size1 at weight 400 in --jp-ui-font-color1; the time, the status word and every detail value are --jp-ui-font-size0 in --jp-ui-font-color2. A coloured card's row keeps those sizes, with its name in --jp-inverse-layout-color0, its time in --jp-inverse-layout-color3 at rest and --jp-inverse-layout-color2 on the current, hovered or selected row, and the rest in --jp-inverse-layout-color1 (DQ-29, DQ-37) the time at --jp-inverse-layout-color1 superseded on 2026-11-04
• Hover and selection paint the card hue at 9.6 % over --jp-layout-color2 the 12 % mix superseded by the 2026-11-04 owner order (ACC-PANEL-278-TINT-ALPHA) on a coloured card's row, and --jp-layout-color2 on a plain card's row and a section row (DQ-10). The panel has one selected row
• A terminal row shows its tab name, or its process when no tab name is known (DQ-31), in the process slot, with no selection (DQ-24); a TERMINALS row of a numbered terminal shows its number in a small rectangle badge, while a card row drops the tN of a numbered terminal the tN on every terminal row superseded by the 2026-11-04 owner order (ACC-TERM-275-CARD-LABEL); the rectangle badge on a TERMINALS row added by ACC-TERM-285-NUMBER-BADGE. The badge is 18 x 13.5 px and takes the colour of the first workspace holding the terminal in the model's order, at the 24 % wash over --jp-layout-color1, with its outline and number in that hue at 45 % over --jp-inverse-layout-color1, which holds 4.5:1 on the wash and 3:1 on the section for every colour the number in --jp-inverse-layout-color1, the card ink that holds 4.5:1 on that wash, superseded by the owner's 2026-11-06 direction (ACC-TERM-296-BADGE-INK); a terminal in no workspace and a colourless workspace leave the box empty, in the row ink the 20 x 15 px empty box superseded by the owner's 2026-11-05 direction (ACC-TERM-290-BADGE-TINT), and a named terminal keeps its name. After the process stands the path of the foreground process in the width left over, cut at its start so its end stays in view (DQ-30)
• Everything else appears on selection: the kernel type, the document and the CPU, a tab's folder, a card's purpose; a KERNELS row shows its memory in the line, selected or not the memory on selection only superseded by the 2026-11-04 owner order (ACC-KERNEL-281-ROW-MEMORY). The detail line shows under the selected row
• Identifiers - the terminal names of the TERMINALS section, kernel ids and paths - are set in --jp-code-font-family; a card row's label, a terminal's included, is in the UI font (DQ-18), and so is a terminal row's path (DQ-30)
• Recency is carried by the time label alone: now, Nm ago, Nh ago, Nd ago, Nmo ago, Ny ago (DQ-21)
• The only brand colour on a section row or a plain card's row is the focus ring, apart from the current row's pale tint (DQ-36) the focus ring as the only brand colour on a row superseded on 2026-11-04: a 1 px --jp-brand-color1 outline at offset -1px on a section row and a row in a card, so it shows whole at the panel edge, and at offset 1 px on a button, shown for keyboard focus only. On a coloured card the ring on the header, its buttons and its rows takes --jp-inverse-layout-color0, because the brand ring falls to 2.34:1 on the sky surface of a selected row; this window's card header sits 2 px further in (offset -3px)

The card as DQ-02, DQ-21 and DQ-24 left it before DQ-28 and DQ-29

3. Colours and type

4. Dialogs

A dialog has one filled button at most, and Cancel is always a surface button. A destructive action is unfilled, with error-coloured text and border, at the far left (DQ-14).

Delete confirmation

• Delete workspace sits in the workspace menu, with a bin icon before its label, and is drawn in --jp-error-color1 at rest and while selected (DQ-11)
• The first click arms it: the item reads Confirm delete and shows a warning icon in place of the bin, in --jp-error-color1. The second click deletes the workspace
• It never runs on this window's workspace, and the panel refuses it on a workspace another window shows, naming the reason
• The menu's Shut down terminal and Shut down kernel entries are destructive entries too, drawn in --jp-error-color1

Shut-down confirmation

• Every band button named Shut down all opens one confirmation before anything stops. The band asks once with the number of items; a row action names the item: "Shut down terminal 7?"
• A terminal or kernel that another workspace also holds is named with that workspace: "Shut down terminal 7? Workspace auto-6 also holds this terminal."
• Shut down is the destructive action, unfilled with --jp-error-color1 text and border at the far left; Cancel is the surface button at the right; no button is filled
• A state line in a dialog has padding 6 px 12 px on --jp-layout-color2 and a 2 px left border in the state colour (DQ-15)
• Nothing stops until the user confirms

Clean-up confirmation

• The WORKSPACES band carries the same band button as the three bands below it, named Clean up workspaces (DQ-22), with the eraser glyph (DQ-29). It is disabled when there is nothing to clean
• The band button opens one confirmation. It lists every workspace with its name and what it holds: each tab by path, each terminal and kernel by name
• Each workspace is marked with its outcome: deleted, emptied for this window's workspace, or kept for a workspace another window shows
• Clean up deletes every workspace except the one this window shows, closing their tabs. It keeps this window's workspace and empties it, closing its tabs and shutting down its kernels, terminals and language servers. A workspace another window shows is kept and named as kept
• Clean up is the destructive action, unfilled with --jp-error-color1 text and border at the far left; Cancel is the surface button at the right. Nothing happens without this confirmation

5. Decisions

DQ-01 to DQ-20 were decided by the Star Colonel on 2026-10-28 as the design-system alignment; DQ-21 and DQ-22 on 2026-10-29. DQ-02 and DQ-05 were amended by his 2026-10-30 direction: a card carries its workspace colour as a 14 % wash over the body and the header, and every card and row surface spans the panel width with the text inset as padding. DQ-03 was amended by the same direction to the reference panel's 4 px band padding and its ▾/▸ text caret. DQ-04 and DQ-19 were amended by the same direction: the sections open exclusively, and this window's card paints its outline inside its box. DQ-23 was added the same day and docks the three lab bands at the panel bottom. DQ-28 replaced the 14 % wash with the header shade on 2026-11-01. DQ-29 replaced the card with the edge tab on 2026-11-02, and the refinements measured in Galaxa Dark Theme - Steel the same day amended DQ-02, DQ-05, DQ-10, DQ-18, DQ-21 and DQ-28. Each row states the decision, the design-system rule it adopts and the criteria that govern it.

How this design reads the decisions

Each point below is a reading this stage made where a decision left a detail open. Each is stated in the criteria named and can be changed there.

• Selection: a click on a row, or the arrow keys, selects it; the panel has one selected row; it paints the surface of DQ-10 and shows a detail line under its name, except on a terminal row (DQ-24); the row stays lit only while it is worked with (DQ-32), and a reload keeps the selection while its item exists and the row stays lit (ACC-LISTS-210-ROW-SELECT). The click still opens the row's item. For a card, selection is being open: the purpose and the counts show while the card is open
• The name of a kernel row is the file name of the notebook or console it serves, or the kernel id when no session uses it; the kernel type, the document path, memory and CPU are its detail (ACC-KERNEL-48-ROW). The detail line repeats the file name inside the path, which KERN-02 keeps whole
• The name of a terminal row is its number in a small rectangle badge for a number, and any other name as it is, while a card row drops the label of a numbered terminal (ACC-TERM-285-NUMBER-BADGE, ACC-TERM-275-CARD-LABEL); its tab name or its process follows the name in the row (DQ-24, DQ-31). Terminals have no state, so their rows show no dot. Tab rows show the file name, and the folder is the detail. Rows keep their 16 px type icon, which the decision does not list among the details
• The tab of a terminal row: a click or Enter on a terminal row, in a card or in TERMINALS, activates the tab of that terminal's running process - the same session name and a session JupyterLab has not disposed - so a tab whose terminal ended never matches, also after a new terminal takes the name; without a match the row opens a tab (ACC-TERM-215-TAB-MATCH)
• The tab a terminal row keeps: once a row opened or activated a tab, every later click or Enter on that row activates that tab, never a second tab of the terminal; the link ends when the terminal ends or the tab closes, and the row then opens a new tab (ACC-TERM-216-TAB-KEPT)
• Language server rows keep the replaced panel's label, pylsp (python), and its shutdown button
• The eye on every card: DQ-12 keeps the eye's place on shown cards too, so on a shown card it hides the workspace, as the brief's "hidden" toggle with an eye icon asks; it is disabled on this window's card; the ... button is disabled on a hidden card (ACC-HIDDEN-213-EYE-TOGGLE)
• Shut down all sits on the section band, which is --jp-layout-color2, so it is a surface button: --jp-layout-color1 with a 1 px --jp-border-color1 border, as the design system's Buttons section draws a secondary action superseded by DQ-20
• Section header padding: 4 px above and below the text, the reference panel's .jp-AiAssistantsPanel-sectionHeader, with the caret on the 4 px inset and the label at 18 px; the caret is the reference's ▾/▸ text glyph in .jp-AiAssistantsPanel-caret (ACC-PANEL-228-BAND-HEIGHT)
• Shutdown dialogs have no filled button: Shut down is the destructive action, unfilled and at the far left; Cancel is the surface button
• The filter still searches process names and kernel types; a terminal row found by its process shows the process in the row (DQ-24); another row found by its detail shows its name, and selecting it shows the detail
• The recessed filter field keeps its 4 percent black over --jp-layout-color1, which the design language prescribes for recessed surfaces; it is the one literal colour word left

6. Lab pages

The extension shows a web page served on the workstation in the main area, beside the tabs a workspace already holds. The page is reached through the lab's /proxy/<port>/ path. Its iframe is sandboxed unless the caller says otherwise: a page under the proxy path gets the sandbox of a server-proxy:open tab and keeps the lab's session, and any other page runs its scripts without the lab's session.

• The command is workspace-page:open with the arguments of server-proxy:open, {url, title?, id?, newBrowserTab?}, beside icon? and policy?; the tab shows the given title, or the page's own document.title once it loads while the page keeps the lab origin, and icon sets the tab icon from an image URL (svg or png) while without it the tab shows the standard page icon (a comment bubble); id becomes the id of the tab's content, and newBrowserTab: true opens the URL in a new browser tab and no lab tab; a newBrowserTab that is not a boolean or an id that is not a string throws, naming the argument, before anything opens (ACC-OPEN-294-PROXY-ARGS)
• A URL on the lab's origin under /proxy/<port>/ or /proxy/absolute/<port>/ gets the sandbox server-proxy:open gives, allow-same-origin allow-scripts allow-popups allow-forms allow-downloads allow-modals, so the page keeps the lab origin, its session, storage, cookies and POSTs; every other URL gets allow-scripts: the page renders and its scripts run, but its origin is opaque, so it has no lab session, storage or cookies (ACC-OPEN-293-PROXY-SANDBOX)
• policy.sandbox replaces either sandbox verbatim; policy.sandbox: null removes the attribute; allow, referrerPolicy and csp set their iframe attributes when given; a malformed policy throws, naming the field, before any tab opens (ACC-OPEN-287-PAGE-POLICY)
• A page tab the command opened that shows a page on the same port, the proxied port or else the URL's origin, or that carries the same id, is reused: it takes the new iframe attributes, title and icon, loads the new URL, and becomes the current tab, and no second tab opens; a URL on the lab's origin is fetched once past the browser cache before the frame loads it, so the frame shows the page document the server serves now, also for an unchanged URL; the command returns the tab before that fetch ends, and only the URL last requested for the tab is loaded (ACC-OPEN-295-PORT-RELOAD)
• The scripts, styles and data a page loads follow their server's caching headers, so the server of a page with separate files sends Cache-Control: no-store, as the mockup server does
• The mockup handover needs no policy: the mockup saves its comments through /proxy/<port>/comments, which the proxy sandbox allows
• The mockup page declares <link rel="icon" href="data:,"> and its server answers /favicon.ico with 204, so the page requests no favicon; the tab icon comes only from the icon argument
• The widget opens in the main area, activates, and closes cleanly (ACC-OPEN-286-LAB-PAGE, ACC-OPEN-287-PAGE-POLICY)