[nwparker]

	Files	Added	Deleted	Net
Test	1	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​296	0	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​296
Prod	2	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​146	$\color{#cf222e}{\Huge{\mathbf{−}}}$​1	$\color{#1a7f37}{\Huge{\mathbf{+}}}$​145

ELI5

Later in this series, editor tabs that show the same file in different workspaces will share one record of their unsaved edits. Deciding "is this the same file?" has to be exactly right: if two different files are treated as one, edits from one could be written into the other. This PR adds only that decision, as a small module with thorough tests. Nothing uses it yet, so nothing changes for users.

What Changed

• New src/renderer/src/store/slices/editor/buffers/editor-buffer-identity.ts: computes the key that will decide which tabs share a buffer record (environment, host, runtime revision, path). Rules:
  • Case is never folded in file names (case-insensitive file systems can't be proven from the client).
  • Windows paths: separators and the drive letter are normalized only for paths proven to be Windows (drive letter or \\), or // paths on a host known to be Windows. On Linux/SSH, //repo/a\b.ts and //repo/a/b.ts stay different files.
  • UNC: only the server name is case-folded, matching how editor models are shared today.
  • WSL: \\wsl$\… and \\wsl.localhost\… are treated as the same file only on a local Windows client, using a tagged key that can't collide with a real share named wsl.
  • SSH: keyed by the endpoint the tab captured when it opened, never the connection's current endpoint, so a target edited to point at another machine can't merge files across machines. Missing endpoint → never shares.
  • Non-edit tabs, unresolved owners and retired runtimes never share.
• editor-model-owner.ts: splits resolveEditorModelOwner out of getEditorModelOwnerKey (pure refactor; output unchanged).

Why

This is step 1b-1 of moving to one editor buffer per file. Landing the identity rules first, unused, lets them be reviewed in isolation. Two independent reviews (GPT and Opus) found four ways an earlier draft could merge different files or split files that share today (WSL vs a real \\wsl share, POSIX // paths, SSH retargeting, UNC server case); all are fixed and covered by tests.

A change to the editor model URI for remote files (from draft #30714) was split out of this PR: it is a user-visible fix in its own right (remote .tsx files currently parse as plain TypeScript, and imports can resolve to the local machine's file at the same path) and will come as its own PR.

Linked Issue

Follow-up to #31251.

Visual Proof

N/A: no behaviour change; the module is not used yet.

Testing

• 27 identity tests (exact case, drive letters/separators, WSL folding on Windows only, POSIX // paths, UNC server case on local and remote Windows hosts, SSH captured endpoint across retarget and reconnect, runtime revision continuation and retirement quarantine).

• Editor slice and editor-model suites pass (484 tests); pnpm tc, check:code-quality:changed, oxfmt --check, oxlint clean.

• Reviewed by GPT (three rounds) and Opus.

• I manually tested these changes locally

• Automated tests added/updated, or explained why not below

AI Disclosure

Review

Agent skill upstream boundary

• Not applicable, or this change copies or mechanically translates no upstream skill-installer source, tests, fixtures, registry entries, path tables, comments, or documentation.

Notes

Ensure no issues in: Security, Cross-platoform support (Linux, Windows, Mac), Remote SSH, Mobile, general backwards compatibility, performance

The renderer does not yet have each SSH tab's captured endpoint; supplying it is part of the later switch PR. Until then the module would never share SSH tabs.

Checklist

• This PR is small and focused
• I explained what changed and why (ELI5, the user-facing before/after, the mechanism, and why over the alternatives)
• Before/after screenshots or videos attached for UI changes, or N/A with reason
• Self-reviewed for correctness, security, and performance
• Cross-platform, SSH/remote, and path/shortcut impact considered (or N/A)
• pnpm lint, pnpm typecheck, pnpm test, and pnpm build pass (or CI will cover; local preferred)

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• Configuration used: Repository UI
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📥 Commits

Reviewing files that changed from the base of the PR and between 786d4b9 and fd08847.

📒 Files selected for processing: 3

• src/renderer/src/components/editor/editor-model-owner.ts
• src/renderer/src/store/slices/editor/buffers/editor-buffer-identity.test.ts
• src/renderer/src/store/slices/editor/buffers/editor-buffer-identity.ts

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📥 Commits

Reviewing files that changed from the base of the PR and between 6e973fa and edc4cff.

📒 Files selected for processing: 3

• src/renderer/src/components/editor/editor-model-owner.ts
• src/renderer/src/store/slices/editor/buffers/editor-buffer-identity.test.ts
• src/renderer/src/store/slices/editor/buffers/editor-buffer-identity.ts

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📝 Walkthrough

The change adds resolveEditorModelOwner and updates getEditorModelOwnerKey to use its resolved owner. It also adds utilities to create editor buffer identities from environment, host, runtime pairing, SSH endpoint, and normalized path data. The utilities handle unresolved or non-edit tabs, retired environments, and detached record IDs. New tests cover path normalization, host and ownership cases, and runtime pairing revisions.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to edc4c

This change adds groundwork for deciding when editor tabs refer to the same file, but nothing uses it yet. The existing editor owner key behaves the same as before, so users should see no change. No merge-blocking risk was found.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly identifies the main change: adding rules to determine when editor tabs represent the same file. The phase and unused status provide useful scope context.
Description check		The description is detailed and covers the change, rationale, testing, visual proof, scope, and checklist. It does not provide an actual linked issue URL as required by the template; it only reference…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description is detailed and covers the change, rationale, testing, visual proof, scope, and checklist. It does not provide an actual linked issue URL as required by the template; it only references #31251, and the full validation command checklist remains unchecked.

✨ Finishing Touches: 💡 1

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