Native Session Artifact Opening

Traceability

• Spec ID: native-session-artifact-opening
• Status: Implemented

Intent

Treat files retained by a coding Session as the source of truth for Viewer surfaces. A user should be able to select, press Enter on, or double-click a Session file such as review.diff and inspect its exact current revision in the right-hand Artifact View. The model must not call a Viewer-specific tool merely to make an existing file visible.

Acceptance Scenarios

• AC-1: Studio correlates only the Session's already-confined Artifact catalog entries; it does not infer a browser-readable path from raw tool arguments.
• AC-2: A Session with an observed .diff or .patch file shows that file as a native row. Selecting it, pressing Enter, or double-clicking it opens the exact catalog revision in the adjacent right-hand Artifact View.
• AC-3: Opening a Session file performs no mutation and emits no model or MCP tool call. Diff and Patch files use the activated Provider or native fallback selected by the existing Artifact registry.
• AC-4: A missing, stale, unsafe, unsupported, or unobserved path is absent from the Session file list rather than being opened directly from the browser.
• AC-5: Wide, compact, and narrow Studio layouts remain bounded, keyboard reachable, and free of page or console errors.

Non-goals

• Applying a Patch from Studio; the current public Provider contract has no reviewed mutation and approval transport.
• Reconstructing a historical file revision when only the current workspace file is retained.
• Turning terminal sessions into files or allowing a Viewer to create a PTY.
• Adding a new host adapter or weakening Provider activation, revision, or opaque-origin policies.

Plan and Tasks

1. Reuse /api/artifacts and its Session observations as the only browser catalog for Session files.
2. Load the selected Session detail and its correlated Artifact descriptors, then render a docked file list and right-hand ArtifactView without adding a second format switch.
3. Keep single-click selection, Enter opening, and double-click acceleration on one command path.
4. Add focused contract/browser coverage for a Session-created .diff file and verify responsive behavior.

Test and Review Evidence

• AC-1/AC-4: focused workspace Artifact observation and server route tests.
• AC-2/AC-3: browser test that opens an observed .diff, asserts the Diff surface, and asserts no Viewer tool request is made.
• AC-5: Playwright screenshots and horizontal-overflow checks at 1440x900, 1024x768, and 390x844, plus console/page error collection.
• Review risk: the worktree already contains unrelated staged Compare UX changes. This implementation must not stage, rewrite, or claim them.

Implemented evidence: Harness Studio typecheck/build and 47 files/293 Vitest tests passed; the focused workspace browser scenario passed with review.diff opened through the Session file row into the right-hand Diff surface at all three widths, with no horizontal overflow or captured console/page error.