[nedtwigg]

Surface-creating commands now take their placement reference as --from: split, ensure, tool, open, and iframe. The old placement spelling --surface is rejected. --surface now only names the existing browser that dor agent-browser and dor playwright drive.

The browser providers read --from like their other Dormouse options: anywhere in the argv, up to an optional bare -- that ends interception. They reject it together with --surface before invoking the provider, and carry it to surface.resolveBrowser and surface.browser. The shared router routes on the placement reference, so a --key resolves in that Surface's Workspace. Private non-browser control requests keep their existing surface reference field.

Browser --from fails only a placement the request would make:

• surface.resolveBrowser checks it before the provider runs, when a command that may bind finds no Surface for its key.
• surface.browser checks it before attaching, when no Surface in the answering Wall shows the key or session.

A stale, minimized, or other-Workspace reference therefore never fails a reuse, the Workspace that holds the session answering it, or a diagnostics or dor-embed-size request. Example: --from surface:self after the user minimized the agent's terminal.

Help, the skill, takeover wording, and specs use the new syntax. The skill describes --from once, under "Browser identity": it places only a pane the command creates. It does not tell agents to repeat it, except to keep a key they placed in another Workspace. docs/specs/layout.md's split-from-a-Door rule now defers to "Focus intent", since a split that takes focus is laid out as a pane. Root split help has a regression check for grouped directions and its -- boundary.

Stack: 7/8, based on #1743. Breaking change for Dormouse 2.0.

Validation:

• dor: build and 357 tests (350 passed, 7 platform skips), help snapshots regenerated
• lib: tsc -b; the Wall, wall/ (router, use-dor-control, tool-takeover, preview-slot, and the rest), and WorkspaceWindow suites, 71 files and 1508 tests
• website: pnpm test (typecheck plus 486 tests); standalone tsc --noEmit
• lint:specs (dor-cli budget ratcheted to 6200) and its 58 self-checks, lint:md, lint:public-docs, git diff --check

Mutation checks:

• restoring the old check on every --from request fails the reuse, resolution, and cross-Workspace holder tests
• checking on surface.browser reuse, or not at all, fails the reuse or the refusal-before-attach test
• dropping, or widening, the resolveBrowser create-only check fails the resolution test, as does checking diagnostics or the viewport
• removing the --from/--surface exclusion in the CLI fails the browser placement test

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[dormouse-bot]

One finding, inline: the early --from placement check also runs on requests that reuse an existing browser, so a reference that later becomes unavailable breaks a browser that needs no placement.