diff --git a/src/parser.ts b/src/parser.ts
index fc5471a0..27521e21 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -4413,6 +4413,26 @@ export function setCachePutMeta(meta: { startMs: number; endMs: number; sig: str
   putMeta = meta
 }
 
+export function isRootedProjectPattern(pattern: string): boolean {
+  const raw = pattern.trim().replace(/\\/g, '/')
+  return raw.startsWith('/') || /^[a-zA-Z]:\//.test(raw)
+}
+
+/// An absolute path names ONE project, so it anchors on a segment boundary (the
+/// isProxiedPath rule): "/a/proj" takes "/a/proj/sub" but not "/a/proj-ui-kit".
+/// Both sides key through normalizeAbsProjectPathKey (Windows casefolds, POSIX
+/// does not, #1260), and rootedness alone picks the branch, so "/" names none.
+export function matchesProjectPattern(project: { project: string; projectPath?: string }, pattern: string): boolean {
+  const projectPath = project.projectPath ?? ''
+  if (isRootedProjectPattern(pattern)) {
+    const anchor = normalizeAbsProjectPathKey(pattern)
+    const target = normalizeAbsProjectPathKey(projectPath)
+    return anchor !== null && target !== null && (target === anchor || target.startsWith(anchor + '/'))
+  }
+  const needle = pattern.toLowerCase()
+  return project.project.toLowerCase().includes(needle) || projectPath.toLowerCase().includes(needle)
+}
+
 export function filterProjectsByName(
   projects: ProjectSummary[],
   include?: string[],
@@ -4420,20 +4440,10 @@ export function filterProjectsByName(
 ): ProjectSummary[] {
   let result = projects
   if (include && include.length > 0) {
-    const patterns = include.map(s => s.toLowerCase())
-    result = result.filter(p => {
-      const name = p.project.toLowerCase()
-      const path = p.projectPath.toLowerCase()
-      return patterns.some(pat => name.includes(pat) || path.includes(pat))
-    })
+    result = result.filter(p => include.some(pattern => matchesProjectPattern(p, pattern)))
   }
   if (exclude && exclude.length > 0) {
-    const patterns = exclude.map(s => s.toLowerCase())
-    result = result.filter(p => {
-      const name = p.project.toLowerCase()
-      const path = p.projectPath.toLowerCase()
-      return !patterns.some(pat => name.includes(pat) || path.includes(pat))
-    })
+    result = result.filter(p => !exclude.some(pattern => matchesProjectPattern(p, pattern)))
   }
   return result
 }
diff --git a/src/usage-aggregator.ts b/src/usage-aggregator.ts
index c3e80d69..68c93470 100644
--- a/src/usage-aggregator.ts
+++ b/src/usage-aggregator.ts
@@ -3,7 +3,7 @@ import { CATEGORY_LABELS, type ProjectSummary, type SessionSummary, type TaskCat
 import { isBehavioralCall } from './behavioral-weight.js'
 import { type PeriodData, type ProviderCost, type BreakdownArrays, type MenubarPayload, type ClaudeConfigSelector, type HydrationState, buildMenubarPayload } from './menubar-json.js'
 import { type SessionCountBasis } from './session-count-label.js'
-import { parseAllSessions, filterProjectsByName, filterProjectsByDays, filterProjectsByClaudeConfigSource, filterProjectsByDateRange, isSessionHydrationComplete, sessionHydrationSnapshot } from './parser.js'
+import { parseAllSessions, filterProjectsByName, filterProjectsByDays, filterProjectsByClaudeConfigSource, filterProjectsByDateRange, isSessionHydrationComplete, matchesProjectPattern, sessionHydrationSnapshot } from './parser.js'
 import { findUnpricedModels, getFlatRateModelsConfigHash, getLocalModelSavingsConfigHash, getPriceOverridesConfigHash, getShortModelName, isExpectedFreeModel } from './models.js'
 import { getAllProviders, safeDiscoverSessions } from './providers/index.js'
 import { loadPlugins, pluginPayloadSections } from './plugins/loader.js'
@@ -376,17 +376,17 @@ export function overlayProviderDaySlices(
   return mergeDayEntries(freshSliced, sliced, false, undefined, true)
 }
 
-/// Does a cached day's project entry pass the active name filters? Mirrors
-/// parser.filterProjectsByName exactly — case-insensitive substring match
-/// against the project name OR its filesystem path, include first then exclude —
-/// so a filter selects the same projects whether it is resolved against a fresh
-/// parse or against the day cache. Patterns arrive pre-lowercased. `path` is
+/// Does a cached day's project entry pass the active name filters? Delegates to
+/// the one rule filterProjectsByName applies, so a filter selects the same
+/// projects whether it is resolved against a fresh parse or against the day
+/// cache — a second copy here put anchored live days and substring-matched
+/// cached days inside one headline. Patterns arrive raw: the rule casefolds
+/// identified Windows paths itself and keeps POSIX case as identity. `path` is
 /// absent on entries whose sessions were gone before it could be recorded; the
 /// name is then all there is to match on, as it is for the display layers.
 function dayProjectMatches(name: string, path: string | undefined, include: string[], exclude: string[]): boolean {
-  const n = name.toLowerCase()
-  const p = (path ?? '').toLowerCase()
-  const hit = (pattern: string): boolean => n.includes(pattern) || (p !== '' && p.includes(pattern))
+  const entry = { project: name, projectPath: path ?? '' }
+  const hit = (pattern: string): boolean => matchesProjectPattern(entry, pattern)
   if (include.length > 0 && !include.some(hit)) return false
   if (exclude.length > 0 && exclude.some(hit)) return false
   return true
@@ -532,8 +532,8 @@ export function buildDurableOverviewFromNormalizedIndex(
   opts: AggregateOpts = {},
 ): IndexedDurableOverview {
   const pf = opts.provider ?? 'all'
-  const include = (opts.project ?? []).map(value => value.toLowerCase())
-  const exclude = (opts.exclude ?? []).map(value => value.toLowerCase())
+  const include = opts.project ?? []
+  const exclude = opts.exclude ?? []
   const hasProjectFilter = include.length > 0 || exclude.length > 0
   const filteredProjects = filterProjectsByName(normalizedProjects, opts.project ?? [], opts.exclude ?? [])
   const scanProjects = filterProjectsByDateRange(filteredProjects, periodInfo.range)
@@ -704,8 +704,8 @@ export async function buildDurablePeriod(periodInfo: PeriodInfo, opts: Aggregate
   // name-filtered above (`fp`), but the historical remainder comes straight out
   // of the day cache, so without this slice a --project/--exclude headline
   // counted every expired-source day whole while the detail panels did not.
-  const projectInclude = (opts.project ?? []).map(s => s.toLowerCase())
-  const projectExclude = (opts.exclude ?? []).map(s => s.toLowerCase())
+  const projectInclude = opts.project ?? []
+  const projectExclude = opts.exclude ?? []
   const hasProjectFilter = projectInclude.length > 0 || projectExclude.length > 0
   // What a filtered total cannot claim, and therefore has to leave out: a cached
   // day with no project split at all, or — with a provider filter also active,
diff --git a/tests/parser-filter.test.ts b/tests/parser-filter.test.ts
index 4c347220..829522d4 100644
--- a/tests/parser-filter.test.ts
+++ b/tests/parser-filter.test.ts
@@ -52,6 +52,58 @@ describe('filterProjectsByName', () => {
     expect(result.map(p => p.project).sort()).toEqual(['AgentSeal', 'dashboard'])
   })
 
+  it('an absolute-path pattern does not swallow a sibling sharing its prefix', () => {
+    const siblings = [
+      makeProject('my-company', '/Users/alice/work/my-company'),
+      makeProject('my-company-kit', '/Users/alice/work/my-company-kit'),
+      makeProject('client', '/Users/alice/work/my-company/packages/client'),
+    ]
+    const result = filterProjectsByName(siblings, undefined, ['/Users/alice/work/my-company'])
+    expect(result.map(p => p.project)).toEqual(['my-company-kit'])
+  })
+
+  it('anchors an absolute-path include the same way', () => {
+    const siblings = [
+      makeProject('my-company', '/Users/alice/work/my-company'),
+      makeProject('my-company-kit', '/Users/alice/work/my-company-kit'),
+    ]
+    expect(filterProjectsByName(siblings, ['/Users/alice/work/my-company']).map(p => p.project)).toEqual(['my-company'])
+  })
+
+  it('keeps a plain word loose, so it still spans siblings and worktrees', () => {
+    const siblings = [
+      makeProject('my-company', '/Users/alice/work/my-company'),
+      makeProject('my-company-kit', '/Users/alice/work/my-company-kit'),
+      makeProject('other', '/Users/alice/work/other'),
+    ]
+    expect(filterProjectsByName(siblings, ['my-company']).map(p => p.project)).toEqual(['my-company', 'my-company-kit'])
+  })
+
+  it('is trailing-slash and backslash tolerant on an absolute pattern', () => {
+    const win = [makeProject('app', 'C:\\Users\\alice\\app'), makeProject('app-two', 'C:\\Users\\alice\\app-two')]
+    expect(filterProjectsByName(win, undefined, ['C:/Users/alice/app/']).map(p => p.project)).toEqual(['app-two'])
+  })
+
+  it('folds case on an identified Windows pattern and keeps POSIX case identity', () => {
+    const posix = [makeProject('Vault', '/a/Vault'), makeProject('vault', '/a/vault')]
+    expect(filterProjectsByName(posix, ['/a/Vault']).map(p => p.project)).toEqual(['Vault'])
+    const win = [makeProject('vault', 'C:\\Work\\Vault')]
+    expect(filterProjectsByName(win, ['c:/work/vault']).map(p => p.project)).toEqual(['vault'])
+    const unc = [makeProject('vault', '\\\\Server\\Share\\Vault')]
+    expect(filterProjectsByName(unc, ['//server/share']).map(p => p.project)).toEqual(['vault'])
+  })
+
+  it('anchors a POSIX pattern against a Codex-style stripped absolute path', () => {
+    const codex = [makeProject('vault', 'root/vault'), makeProject('vault-ui', 'root/vault-ui')]
+    expect(filterProjectsByName(codex, undefined, ['/root/vault']).map(p => p.project)).toEqual(['vault-ui'])
+  })
+
+  it('names no project for a rooted pattern that keys to nothing', () => {
+    expect(filterProjectsByName(projects, ['/'])).toEqual([])
+    expect(filterProjectsByName(projects, undefined, ['/'])).toEqual(projects)
+    expect(filterProjectsByName(projects, undefined, ['//'])).toEqual(projects)
+  })
+
   it('exclude matches path substring', () => {
     const result = filterProjectsByName(projects, undefined, ['/tmp'])
     expect(result.map(p => p.project)).not.toContain('sandbox')
diff --git a/tests/project-filter-durable-totals.test.ts b/tests/project-filter-durable-totals.test.ts
index 9d8cffdb..f405afdd 100644
--- a/tests/project-filter-durable-totals.test.ts
+++ b/tests/project-filter-durable-totals.test.ts
@@ -112,6 +112,18 @@ function carriedDayTwoProviders(date: string): DailyEntry {
   return day
 }
 
+/** The same carried day, with the two projects as path siblings sharing a prefix. */
+function carriedDaySiblingProjects(date: string): DailyEntry {
+  const day = carriedDayWithProjects(date)
+  const projects = {
+    app: { cost: KEEP.cost, calls: KEEP.calls, savingsUSD: 0, sessions: KEEP.sessions, path: '/Users/gone/app' },
+    'app-kit': { cost: DROP.cost, calls: DROP.calls, savingsUSD: 0, sessions: DROP.sessions, path: '/Users/gone/app-kit' },
+  }
+  day.projects = projects
+  day.providers['claude']!.projects = projects
+  return day
+}
+
 async function seedCache(...days: DailyEntry[]): Promise<void> {
   const cache: DailyCache = {
     version: DAILY_CACHE_VERSION,
@@ -235,6 +247,35 @@ describe('durable headline honours --project / --exclude on carried days', () =>
     expect(durable.data.cost).toBeCloseTo(live.cost + KEEP.cost, 6)
   })
 
+  // A cached day and a live day must answer the same pattern the same way. The
+  // two below are the shapes where a substring copy of the rule diverges from
+  // the anchored one, inside a single headline total.
+  it('anchors an absolute pattern on a carried day, so the sibling survives', async () => {
+    await seedCache(carriedDaySiblingProjects(daysAgoStr(10)))
+    await seedLiveTodaySession()
+    const range = coveringRange()
+
+    const live = await liveOnly(range, [], ['/Users/gone/app'])
+    clearSessionCache()
+    const durable = await buildDurablePeriod({ range, label: 'p' }, { provider: 'all', exclude: ['/Users/gone/app'] })
+
+    expect(durable.data.cost).toBeCloseTo(live.cost + DROP.cost, 6)
+    expect(durable.data.calls).toBe(live.calls + DROP.calls)
+  })
+
+  it('keeps POSIX case identity on a carried day, so a wrong-case path selects nothing', async () => {
+    await seedCache(carriedDaySiblingProjects(daysAgoStr(10)))
+    await seedLiveTodaySession()
+    const range = coveringRange()
+
+    const live = await liveOnly(range, [], ['/users/gone/app'])
+    clearSessionCache()
+    const durable = await buildDurablePeriod({ range, label: 'p' }, { provider: 'all', exclude: ['/users/gone/app'] })
+
+    expect(durable.data.cost).toBeCloseTo(live.cost + DAY_COST, 6)
+    expect(durable.data.calls).toBe(live.calls + DAY_CALLS)
+  })
+
   it('keeps a project whose name is a prototype member (constructor) in the sliced total', async () => {
     // A project directory can legitimately be named "constructor"/"valueOf"/etc.
     // The day cache must carry it as an own key: if the load path drops it, the