diff --git a/src/main/runtime/orca-runtime.ts b/src/main/runtime/orca-runtime.ts
index c33d741bc29..ee1f977ca88 100644
--- a/src/main/runtime/orca-runtime.ts
+++ b/src/main/runtime/orca-runtime.ts
@@ -534,7 +534,8 @@ import {
   WORKTREE_ID_SEPARATOR,
   getRepoIdFromWorktreeId,
   splitWorktreeId,
-  splitWorktreeIdForFilesystem
+  splitWorktreeIdForFilesystem,
+  worktreeIdComparisonKey
 } from '../../shared/worktree/id'
 import {
   getProjectIdForProviderIdentity,
@@ -32294,6 +32295,7 @@ export class OrcaRuntimeService {
     return worktreeId
   }
 
+  /** Resolves one workspace or throws `selector_not_found` / `selector_ambiguous` — never picks a winner. */
   private async resolveWorktreeSelector(selector: string): Promise<ResolvedWorktree> {
     const explicitWorktreeId = this.getValidatedExplicitWorktreeIdSelector(selector)
     // Why only `id:`: every other selector kind is matched across the whole fleet, and their
@@ -32315,6 +32317,16 @@ export class OrcaRuntimeService {
     if (selector.startsWith('id:')) {
       const worktreeId = explicitWorktreeId ?? selector.slice(3)
       candidates = worktrees.filter((worktree) => worktree.id === worktreeId)
+      if (candidates.length === 0) {
+        // Why (#16243): `id:` is the only shape the renderer can send, and a stored id can spell
+        // its path differently from the scan — the divergence `path:` has always absorbed.
+        // The bare unprefixed branch below stays byte-exact on purpose: only `id:` reaches a
+        // renderer caller, so `id:repo::p/` folds here while bare `repo::p/` still misses.
+        const comparisonKey = worktreeIdComparisonKey(worktreeId)
+        candidates = comparisonKey
+          ? worktrees.filter((worktree) => worktreeIdComparisonKey(worktree.id) === comparisonKey)
+          : candidates
+      }
       if (candidates.length === 0) {
         const parsed = splitWorktreeIdForFilesystem(worktreeId)
         const repo = parsed ? this.store?.getRepo(parsed.repoId) : null
@@ -41428,12 +41440,8 @@ function runtimePathsEqual(left: string, right: string): boolean {
  * Windows/WSL/SSH ids still match themselves across hosts.
  */
 function runtimeWorktreeIdsEqual(left: string, right: string): boolean {
-  const parsedLeft = splitWorktreeId(left)
-  const parsedRight = splitWorktreeId(right)
-  return parsedLeft && parsedRight
-    ? parsedLeft.repoId === parsedRight.repoId &&
-        runtimePathsEqual(parsedLeft.worktreePath, parsedRight.worktreePath)
-    : left === right
+  const leftKey = worktreeIdComparisonKey(left)
+  return leftKey === null ? left === right : leftKey === worktreeIdComparisonKey(right)
 }
 
 function runtimeWorktreeIdentityKey(worktreeId: string): string {
diff --git a/src/main/runtime/repo-worktree-row-resolution.test.ts b/src/main/runtime/repo-worktree-row-resolution.test.ts
index be50f5678a7..d4bff4a9442 100644
--- a/src/main/runtime/repo-worktree-row-resolution.test.ts
+++ b/src/main/runtime/repo-worktree-row-resolution.test.ts
@@ -200,3 +200,88 @@ describe('host-qualified scoped worktree resolution', () => {
     expect(getRepos).not.toHaveBeenCalled()
   })
 })
+
+/**
+ * #16243: the renderer can only address a workspace by `id:<repoId>::<path>`, and this scoped
+ * lookup is what a host-qualified removal resolves through. It matched the id byte for byte while a
+ * `path:` selector has always compared through `normalizeRuntimePathForComparison`, so a stored id
+ * spelling its path differently from `git worktree list` resolved for the CLI and not for the UI.
+ */
+describe('scoped worktree id resolution across path spellings (#16243)', () => {
+  it.each([
+    ['a trailing slash', '/same/worktree', 'shared::/same/worktree/'],
+    ['a doubled separator', '/same/worktree', 'shared::/same//worktree'],
+    ['an NFD name', '/same/café', `shared::${'/same/café'.normalize('NFD')}`]
+  ])('resolves the scanned row when the id carries %s', async (_label, scannedPath, worktreeId) => {
+    const owner = repo('shared', '/local/repo', { executionHostId: 'local' })
+    const deps = createDeps([owner])
+    deps.scanRepo.mockImplementation(async () => ({
+      ok: true,
+      worktrees: [gitWorktree(scannedPath)]
+    }))
+
+    await expect(resolveScopedWorktreeIdRow(deps, worktreeId, 'local')).resolves.toMatchObject({
+      id: `shared::${scannedPath}`,
+      path: scannedPath
+    })
+  })
+
+  it('still refuses the same path under a different repo id', async () => {
+    const deps = createDeps([
+      repo('shared', '/local/repo', { executionHostId: 'local' }),
+      repo('unrelated', '/unrelated/repo', { executionHostId: 'local' })
+    ])
+
+    await expect(
+      resolveScopedWorktreeIdRow(deps, 'unrelated::/same/worktree/', 'local')
+    ).resolves.toBeNull()
+  })
+
+  it('refuses rather than guessing when two rows spell one path', async () => {
+    const owner = repo('shared', '/local/repo', { executionHostId: 'local' })
+    const deps = createDeps([owner])
+    deps.scanRepo.mockImplementation(async () => ({
+      ok: true,
+      worktrees: [gitWorktree('/same/worktree'), gitWorktree('/same//worktree')]
+    }))
+
+    await expect(
+      resolveScopedWorktreeIdRow(deps, 'shared::/same/worktree/', 'local')
+    ).resolves.toBeNull()
+  })
+
+  it('prefers the exactly matching row over an equivalent spelling', async () => {
+    const owner = repo('shared', '/local/repo', { executionHostId: 'local' })
+    const deps = createDeps([owner])
+    deps.scanRepo.mockImplementation(async () => ({
+      ok: true,
+      worktrees: [gitWorktree('/same//worktree'), gitWorktree('/same/worktree')]
+    }))
+
+    await expect(
+      resolveScopedWorktreeIdRow(deps, 'shared::/same//worktree', 'local')
+    ).resolves.toMatchObject({ id: 'shared::/same//worktree' })
+  })
+
+  // #15598/#15616: the backslash spelling is what a pre-restart Windows registration recorded.
+  it('resolves a Windows backslash id against the forward-slash spelling git reports', async () => {
+    const path = 'D:/Agentic/game2/battle-core'
+    const owner = repo('shared', 'D:/Agentic/game2', { executionHostId: 'runtime:windows' })
+    const deps = createDeps([owner])
+    deps.scanRepo.mockImplementation(async () => ({ ok: true, worktrees: [gitWorktree(path)] }))
+
+    await expect(
+      resolveScopedWorktreeIdRow(deps, 'shared::D:\\Agentic\\game2\\battle-core', 'runtime:windows')
+    ).resolves.toMatchObject({ id: `shared::${path}`, path })
+  })
+
+  it.each([
+    ['no repo boundary', 'not-an-id'],
+    ['an empty path', 'shared::']
+  ])('keeps exact matching for a malformed id with %s', async (_label, worktreeId) => {
+    const deps = createDeps([repo('shared', '/local/repo', { executionHostId: 'local' })])
+
+    await expect(resolveScopedWorktreeIdRow(deps, worktreeId, 'local')).resolves.toBeNull()
+    expect(deps.scanRepo).not.toHaveBeenCalled()
+  })
+})
diff --git a/src/main/runtime/repo-worktree-row-resolution.ts b/src/main/runtime/repo-worktree-row-resolution.ts
index b65fd9295f6..a9ef618ced7 100644
--- a/src/main/runtime/repo-worktree-row-resolution.ts
+++ b/src/main/runtime/repo-worktree-row-resolution.ts
@@ -1,4 +1,8 @@
-import { splitWorktreeId, splitWorktreeIdForFilesystem } from '../../shared/worktree/id'
+import {
+  splitWorktreeId,
+  splitWorktreeIdForFilesystem,
+  worktreeIdComparisonKey
+} from '../../shared/worktree/id'
 import { getRepoExecutionHostId, type ExecutionHostId } from '../../shared/execution-host'
 import { isFolderRepo } from '../../shared/repo-kind'
 import { projectResolvedWorktreeLineage } from '../../shared/resolved-worktree-lineage'
@@ -195,5 +199,18 @@ export async function resolveScopedWorktreeIdRow(
     resolveLocalProjectRuntimesForRepos(store, [repo])
   )
   const projected = projectResolvedWorktreeLineage(rows, store.getAllWorktreeLineage?.() ?? {})
-  return projected.find((worktree) => worktree.id === worktreeId) ?? null
+  const exact = projected.find((worktree) => worktree.id === worktreeId)
+  if (exact) {
+    return exact
+  }
+  // Why (#16243): the scan can spell this id's path differently — the divergence `path:` absorbs.
+  // One equivalent row may stand in; two is an ambiguity a scoped lookup must refuse, not guess.
+  const comparisonKey = worktreeIdComparisonKey(worktreeId)
+  if (comparisonKey === null) {
+    return null
+  }
+  const equivalent = projected.filter(
+    (worktree) => worktreeIdComparisonKey(worktree.id) === comparisonKey
+  )
+  return equivalent.length === 1 ? equivalent[0] : null
 }
diff --git a/src/main/runtime/worktree-rm-id-selector-path-spelling.test.ts b/src/main/runtime/worktree-rm-id-selector-path-spelling.test.ts
new file mode 100644
index 00000000000..f4e61a76381
--- /dev/null
+++ b/src/main/runtime/worktree-rm-id-selector-path-spelling.test.ts
@@ -0,0 +1,273 @@
+/**
+ * Pins path-SPELLING parity between an `id:` selector and `path:`, deliberately not dedupe parity:
+ * where two same-host rows spell one directory, `path:` collapses them to the first while `id:`
+ * refuses as ambiguous, because this resolver also serves delete (#16243).
+ */
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+const electronMocks = vi.hoisted(() => {
+  const ipcMain = {
+    on: vi.fn(() => ipcMain),
+    removeListener: vi.fn(() => ipcMain),
+    emit: vi.fn(() => true)
+  }
+  return {
+    BrowserWindow: { fromId: vi.fn((): unknown => null) },
+    webContents: { fromId: vi.fn((): unknown => null) },
+    ipcMain,
+    app: { getPath: vi.fn(() => '/tmp'), isPackaged: false }
+  }
+})
+vi.mock('electron', () => electronMocks)
+
+const getSshGitProviderMock = vi.hoisted(() => vi.fn())
+vi.mock('../providers/ssh-git-dispatch', () => ({
+  getSshGitProvider: getSshGitProviderMock,
+  getSshGitProviderGeneration: vi.fn(() => 0),
+  SSH_GIT_PROVIDER_UNAVAILABLE_MESSAGE: 'unavailable',
+  requireSshGitProvider: (connectionId: string) => getSshGitProviderMock(connectionId)
+}))
+
+const listWorktreesStrictMock = vi.hoisted(() => vi.fn())
+vi.mock('../git/worktree', async (importOriginal) => ({
+  ...(await importOriginal<Record<string, unknown>>()),
+  listWorktreesStrict: listWorktreesStrictMock
+}))
+
+import { LOCAL_EXECUTION_HOST_ID } from '../../shared/execution-host'
+import { OrcaRuntimeService } from './orca-runtime'
+
+const REPO_ID = 'repo-local'
+const REPO_PATH = '/srv/projects/app'
+/** The spelling `git worktree list` reports. */
+const WORKTREE_PATH = '/srv/projects/workspaces/plugin-host'
+const CANONICAL_ID = `${REPO_ID}::${WORKTREE_PATH}`
+
+/** One directory, other spellings a stored id can legitimately carry. */
+const ID_SPELLINGS: [label: string, worktreePath: string, repoPath?: string][] = [
+  ['a trailing slash', `${WORKTREE_PATH}/`],
+  ['a doubled separator', '/srv/projects//workspaces/plugin-host'],
+  ['an NFD workspace name', '/srv/projects/workspaces/café-plugin'.normalize('NFD')],
+  // #15598/#15616: a Windows registration records backslashes; git reports forward slashes.
+  ['a backslash Windows spelling', 'D:\\Agentic\\game2\\battle-core', 'D:/Agentic/game2']
+]
+
+/** What a scan reports for a stored id: the same directory, canonically spelled. */
+function scannedSpellingOf(storedPath: string): string {
+  const slashed = /^[A-Za-z]:[\\/]/.test(storedPath) ? storedPath.replace(/\\/g, '/') : storedPath
+  return slashed.normalize('NFC').replace(/\/+/g, '/').replace(/\/$/, '')
+}
+
+/** One registered repo whose worktree meta is writable, so a delete's `forgetLocal` is observable. */
+function makeStore(repoPath: string = REPO_PATH) {
+  const metaById: Record<string, Record<string, unknown>> = {}
+  const store = {
+    getRepo: (id: string) => store.getRepos().find((repo) => repo.id === id),
+    getRepos: () => [
+      { id: REPO_ID, path: repoPath, displayName: 'app', badgeColor: 'blue', addedAt: 1 }
+    ],
+    getAllWorktreeMeta: vi.fn(() => metaById),
+    getWorktreeMeta: (id: string) => metaById[id],
+    setWorktreeMeta: (id: string, meta: Record<string, unknown>) => {
+      metaById[id] = { ...metaById[id], ...meta }
+      return metaById[id]
+    },
+    removeWorktreeMeta: () => {},
+    getAllWorktreeLineage: () => ({}),
+    getAllWorkspaceLineage: () => ({}),
+    removeWorktreeLineage: vi.fn(),
+    removeWorkspaceLineage: vi.fn(),
+    getGitHubCache: () => undefined as never,
+    getSettings: () => ({
+      workspaceDir: '/tmp/workspaces',
+      nestWorkspaces: false,
+      refreshLocalBaseRefOnWorktreeCreate: false,
+      branchPrefix: 'none',
+      branchPrefixCustom: ''
+    }),
+    getProjects: () => []
+  }
+  return store
+}
+
+/** `git worktree list` output: the main checkout plus one workspace at `worktreePath`. */
+function scanReports(worktreePath: string, repoPath: string = REPO_PATH): void {
+  listWorktreesStrictMock.mockResolvedValue([
+    { path: repoPath, head: 'abc', branch: 'main', isBare: false, isMainWorktree: true },
+    { path: worktreePath, head: 'def', branch: 'feature', isBare: false, isMainWorktree: false }
+  ])
+}
+
+type RemovalInternals = {
+  resolveWorktreeRemovalTarget: (
+    worktreeSelector: string,
+    requiredHostId?: string
+  ) => Promise<{ id: string; repoId: string; path: string }>
+}
+
+beforeEach(() => {
+  getSshGitProviderMock.mockReset()
+  listWorktreesStrictMock.mockReset()
+})
+
+describe('worktree id selectors vs. the path spelling git reports (#16243)', () => {
+  it.each(ID_SPELLINGS)(
+    'resolves through the fleet path what `path:` resolves when the id carries %s',
+    async (_label, storedPath, repoPath) => {
+      scanReports(scannedSpellingOf(storedPath), repoPath)
+      const runtime = new OrcaRuntimeService(makeStore(repoPath) as never)
+
+      // The CLI's shape, and the live data point: `path:` already resolves it.
+      const byPath = await runtime.showManagedWorktree(`path:${storedPath}`)
+      // The only shape the renderer can send must resolve the SAME workspace.
+      await expect(
+        runtime.showManagedWorktree(`id:${REPO_ID}::${storedPath}`)
+      ).resolves.toMatchObject({ id: byPath.id, path: byPath.path })
+    }
+  )
+
+  it.each(ID_SPELLINGS)(
+    'resolves a host-qualified removal target when the id carries %s',
+    async (_label, storedPath, repoPath) => {
+      scanReports(scannedSpellingOf(storedPath), repoPath)
+      const runtime = new OrcaRuntimeService(makeStore(repoPath) as never)
+      const internals = runtime as unknown as RemovalInternals
+
+      // The scoped path the UI's delete takes must agree with the fleet path above.
+      await expect(
+        internals.resolveWorktreeRemovalTarget(
+          `id:${REPO_ID}::${storedPath}`,
+          LOCAL_EXECUTION_HOST_ID
+        )
+      ).resolves.toMatchObject({ repoId: REPO_ID, path: scannedSpellingOf(storedPath) })
+    }
+  )
+
+  it('still refuses an id whose path names a different workspace', async () => {
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+
+    await expect(
+      runtime.showManagedWorktree(`id:${REPO_ID}::/srv/projects/workspaces/other-plugin`)
+    ).rejects.toThrow('selector_not_found')
+  })
+
+  // STA-4343: matching across repo ids would delete a workspace the caller never confirmed.
+  it('still refuses the same path under a different repo id', async () => {
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+
+    await expect(runtime.showManagedWorktree(`id:other-repo::${WORKTREE_PATH}/`)).rejects.toThrow(
+      'selector_not_found'
+    )
+  })
+
+  it('still refuses a removal qualified to a host that does not own the repo id', async () => {
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+    const internals = runtime as unknown as RemovalInternals
+
+    await expect(
+      internals.resolveWorktreeRemovalTarget(`id:${CANONICAL_ID}/`, 'runtime:env-b')
+    ).rejects.toThrow('selector_not_found')
+  })
+
+  it('keeps `id:` and `path:` agreeing on a dot segment neither canonicalizes', async () => {
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+    const dotted = '/srv/projects/./workspaces/plugin-host'
+
+    await expect(runtime.showManagedWorktree(`path:${dotted}`)).rejects.toThrow(
+      'selector_not_found'
+    )
+    await expect(runtime.showManagedWorktree(`id:${REPO_ID}::${dotted}`)).rejects.toThrow(
+      'selector_not_found'
+    )
+  })
+
+  // #15598/#15616: on Windows one checkout is recorded under both spellings, and git reports the
+  // forward-slash one. The backslash id itself rides the ID_SPELLINGS rows above; these pin the
+  // folding limits around it.
+  describe('Windows drive-letter spellings', () => {
+    const WINDOWS_REPO = 'D:/Agentic/game2'
+    const WINDOWS_WORKTREE = 'D:/Agentic/game2/battle-core'
+
+    it('folds drive-letter case only for Windows paths, never for a POSIX path', async () => {
+      scanReports(WINDOWS_WORKTREE, WINDOWS_REPO)
+      const windowsRuntime = new OrcaRuntimeService(makeStore(WINDOWS_REPO) as never)
+
+      // A Windows root is case-insensitive, as `path:` already treats it.
+      await expect(
+        windowsRuntime.showManagedWorktree(`id:${REPO_ID}::d:/agentic/game2/battle-core`)
+      ).resolves.toMatchObject({ path: WINDOWS_WORKTREE })
+
+      // A POSIX root is not: folding case there would merge distinct directories for a delete.
+      scanReports(WORKTREE_PATH)
+      const posixRuntime = new OrcaRuntimeService(makeStore() as never)
+
+      await expect(
+        posixRuntime.showManagedWorktree(`id:${REPO_ID}::/SRV/projects/workspaces/plugin-host`)
+      ).rejects.toThrow('selector_not_found')
+    })
+
+    it('does not fold a backslash inside a POSIX path, where it is a valid filename character', async () => {
+      scanReports(WORKTREE_PATH)
+      const runtime = new OrcaRuntimeService(makeStore() as never)
+
+      await expect(
+        runtime.showManagedWorktree(`id:${REPO_ID}::/srv/projects\\workspaces\\plugin-host`)
+      ).rejects.toThrow('selector_not_found')
+    })
+  })
+
+  // The fail-closed guard on a delete-capable resolver: two rows spelling one directory must not
+  // let a folded id pick one. `path:` collapses same-host duplicates; `id:` deliberately refuses.
+  it('refuses a folded id when two same-repo rows spell one directory', async () => {
+    listWorktreesStrictMock.mockResolvedValue([
+      { path: REPO_PATH, head: 'abc', branch: 'main', isBare: false, isMainWorktree: true },
+      { path: WORKTREE_PATH, head: 'def', branch: 'feature', isBare: false, isMainWorktree: false },
+      {
+        path: '/srv/projects//workspaces/plugin-host',
+        head: 'ghi',
+        branch: 'feature-2',
+        isBare: false,
+        isMainWorktree: false
+      }
+    ])
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+
+    // Matches neither row exactly, folds to both.
+    await expect(runtime.showManagedWorktree(`id:${CANONICAL_ID}/`)).rejects.toThrow(
+      'selector_ambiguous'
+    )
+  })
+
+  // Live-proof limit, pinned so nobody "fixes" the trimming: a folder-workspace id only trims a
+  // trailing slash at end of string, so one placed before the instance suffix stays exact-only.
+  it('keeps a folder-workspace id exact when a slash precedes the instance suffix', async () => {
+    const instanceSuffix = '::workspace:123e4567-e89b-12d3-a456-426614174000'
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+
+    await expect(
+      runtime.showManagedWorktree(`id:${REPO_ID}::${WORKTREE_PATH}/${instanceSuffix}`)
+    ).rejects.toThrow('selector_not_found')
+  })
+
+  // #15616 guarantees malformed ids keep exact-match behavior; both sites must honour that too.
+  it.each([
+    ['no repo boundary', 'not-an-id'],
+    ['an empty path', `${REPO_ID}::`]
+  ])('keeps exact matching for a malformed id with %s', async (_label, malformedId) => {
+    scanReports(WORKTREE_PATH)
+    const runtime = new OrcaRuntimeService(makeStore() as never)
+    const internals = runtime as unknown as RemovalInternals
+
+    await expect(runtime.showManagedWorktree(`id:${malformedId}`)).rejects.toThrow(
+      'selector_not_found'
+    )
+    await expect(
+      internals.resolveWorktreeRemovalTarget(`id:${malformedId}`, LOCAL_EXECUTION_HOST_ID)
+    ).rejects.toThrow('selector_not_found')
+  })
+})
diff --git a/src/shared/worktree/id.test.ts b/src/shared/worktree/id.test.ts
index e64d27784f5..726e53abe5a 100644
--- a/src/shared/worktree/id.test.ts
+++ b/src/shared/worktree/id.test.ts
@@ -4,7 +4,8 @@ import {
   getRepoIdFromWorktreeId,
   getWorktreePathBasenameFromId,
   splitWorktreeId,
-  splitWorktreeIdForFilesystem
+  splitWorktreeIdForFilesystem,
+  worktreeIdComparisonKey
 } from './id'
 
 describe('WORKTREE_ID_SEPARATOR', () => {
@@ -119,3 +120,65 @@ describe('getWorktreePathBasenameFromId', () => {
     expect(getWorktreePathBasenameFromId('repo-123::')).toBeNull()
   })
 })
+
+/**
+ * #16243: the renderer can only address a workspace by `id:<repoId>::<path>`, so the key must fold
+ * exactly the path spellings a `path:` selector already folds — and nothing more.
+ */
+describe('worktreeIdComparisonKey path-spelling parity for id: selectors (#16243)', () => {
+  const canonical = 'repo-123::/srv/workspaces/plugin'
+  const key = (worktreeId: string): string | null => worktreeIdComparisonKey(worktreeId)
+
+  it('folds the path spellings a `path:` selector already accepts', () => {
+    expect(key('repo-123::/srv/workspaces/plugin/')).toBe(key(canonical))
+    expect(key('repo-123::/srv//workspaces/plugin')).toBe(key(canonical))
+    expect(key('repo-123::/srv/workspaces/Café'.normalize('NFD'))).toBe(
+      key('repo-123::/srv/workspaces/Café'.normalize('NFC'))
+    )
+  })
+
+  it('folds no more loosely than `path:` does', () => {
+    // A leading `//` is a UNC root, not a doubled separator.
+    expect(key('repo-123://srv/workspaces/plugin')).not.toBe(key(canonical))
+    // Dot segments are not canonicalized, so `id:` and `path:` still agree on refusing them.
+    expect(key('repo-123::/srv/./workspaces/plugin')).not.toBe(key(canonical))
+  })
+
+  // #15598/#15616: the same Windows checkout is recorded with both separators.
+  it('folds Windows separator and drive-letter case, as `path:` already does', () => {
+    const windows = 'repo-123::D:/Agentic/game2'
+    expect(key('repo-123::D:\\Agentic\\game2')).toBe(key(windows))
+    expect(key('repo-123::d:/agentic/game2')).toBe(key(windows))
+    // A backslash is a valid POSIX filename character, so a POSIX path never folds it.
+    expect(key('repo-123::/srv\\workspaces')).not.toBe(key('repo-123::/srv/workspaces'))
+    // POSIX roots stay case-sensitive.
+    expect(key('repo-123::/srv/Workspaces')).not.toBe(key('repo-123::/srv/workspaces'))
+  })
+
+  it('keeps a UNC or WSL root distinct from a drive-letter location', () => {
+    // Different roots naming different filesystems must never collapse into one key.
+    expect(key('repo-123://server/share/game2')).not.toBe(key('repo-123::D:/server/share/game2'))
+    expect(key('repo-123://wsl.localhost/Ubuntu/home/dev/game2')).not.toBe(
+      key('repo-123::D:/home/dev/game2')
+    )
+    // The two UNC aliases Windows exposes for one WSL distro are the same location.
+    expect(key('repo-123://wsl.localhost/Ubuntu/home/dev/game2')).toBe(
+      key('repo-123://wsl$/Ubuntu/home/dev/game2')
+    )
+  })
+
+  it('never merges different repos, workspaces, or folder sessions', () => {
+    // STA-4343: the repo id stays exact, or a removal lands on a repo the caller never confirmed.
+    expect(key('repo-999::/srv/workspaces/plugin')).not.toBe(key(canonical))
+    expect(key('repo-123::/srv/workspaces/other')).not.toBe(key(canonical))
+    expect(key('repo-a::/srv/folder::workspace:123e4567-e89b-12d3-a456-426614174000')).not.toBe(
+      key('repo-a::/srv/folder::workspace:123e4567-e89b-12d3-a456-426614174001')
+    )
+  })
+
+  it('returns null for ids with no repo boundary so callers keep exact matching', () => {
+    expect(key('repo-a')).toBeNull()
+    expect(key('repo-a::')).toBeNull()
+    expect(key('/srv/workspaces/plugin')).toBeNull()
+  })
+})
diff --git a/src/shared/worktree/id.ts b/src/shared/worktree/id.ts
index d71cbac66eb..478ac6bfa76 100644
--- a/src/shared/worktree/id.ts
+++ b/src/shared/worktree/id.ts
@@ -1,3 +1,4 @@
+import { normalizeRuntimePathForComparison } from '../cross-platform-path'
 import { WORKTREE_ID_SEPARATOR } from '../pty-session-id-format'
 
 export { WORKTREE_ID_SEPARATOR } from '../pty-session-id-format'
@@ -17,6 +18,22 @@ export function getRepoIdFromWorktreeId(worktreeId: string): string {
   return separatorIdx === -1 ? worktreeId : worktreeId.slice(0, separatorIdx)
 }
 
+/**
+ * Canonical comparison form of a worktree id: the repoId is compared EXACT and only the path folds,
+ * through the same `normalizeRuntimePathForComparison` a `path:` selector has always applied and
+ * byte-exact id matching denied the renderer (#16243). Null for a malformed id, so callers keep
+ * exact matching for it. Comparison only — never persist or return this key.
+ */
+export function worktreeIdComparisonKey(worktreeId: string): string | null {
+  const parsed = splitWorktreeId(worktreeId)
+  if (!parsed || !parsed.repoId || !parsed.worktreePath) {
+    return null
+  }
+  return `${parsed.repoId}${WORKTREE_ID_SEPARATOR}${normalizeRuntimePathForComparison(
+    parsed.worktreePath
+  )}`
+}
+
 export function splitWorktreeId(worktreeId: string): ParsedWorktreeId | null {
   const separatorIdx = worktreeId.indexOf(WORKTREE_ID_SEPARATOR)
   if (separatorIdx === -1) {