fix(codex): walk billed+nest trees on the no-arg singleton

filterOverlap required an explicit nest path, so export const codex =
createCodexProvider() never deduped. When the resolved dir is a launcher
nest and ~/.codex is a distinct existing tree, discover both and drop nest
sources whose session id is already billed. Unique nest and billed sessions
stay. Soften the Buzz doctor note to a presence heuristic.

src/launcher-homes.ts

@@ -23,8 +23,9 @@ export function sameCodexHome(a: string, b: string): boolean {
 }
 
 /** True when `dir` is a Codex home nested under a launcher nest, and a distinct
- *  primary Codex home exists. Gate for overlap-only filtering on a *second*
- *  provider instance — it does not by itself drop sessions. */
+ *  primary Codex home exists. Gate for overlap-only filtering — it does not by
+ *  itself drop sessions. The production no-arg factory uses this to walk both
+ *  trees; an explicit nest factory uses it to drop overlapping nest ids. */
 export function isNestedLauncherCodexHome(
   dir: string,
   opts: { primaryDir: string; launcherRoots: string[] },
@@ -125,7 +126,7 @@ export function collectLauncherNotes(home = homedir()): LauncherNote[] {
       name: 'buzz',
       path: buzz,
       billedVia: 'codex',
-      verdict: 'LAUNCHER (billed via Codex)',
+      verdict: 'LAUNCHER (heuristic; billed via Codex)',
     })
   }
   const grokStore = join(home, '.grok')

src/providers/codex.ts

@@ -1330,24 +1330,40 @@ export async function parseCodexFileFull(source: SessionSource, seenKeys: Set<st
   return { calls, ...(capture.write ? { write: capture.write } : {}) }
 }
 
+function rootsFor(home: string): ProbeRoot[] {
+  return [
+    { path: join(home, 'sessions'), label: 'sessions' },
+    { path: join(home, 'archived_sessions'), label: 'archived' },
+  ]
+}
+
+function dropOverlappingNestSources(sources: SessionSource[], billedHome: string): SessionSource[] {
+  const billedIds = listRolloutSessionIds(billedHome)
+  return sources.filter(source => {
+    const id = rolloutFileSessionId(source.path)
+    return !(id && billedIds.has(id))
+  })
+}
+
 export function createCodexProvider(
   codexDir?: string,
   opts?: { primaryDir?: string; launcherRoots?: string[] },
 ): Provider {
   const dir = getCodexDir(codexDir)
-  // Production singleton (no args) still honors CODEX_HOME / override as the
-  // one root. An explicit nest path — even without second-factory opts —
-  // overlap-filters against the default billed home using defaultLauncherRoots
-  // so a future createCodexProvider(nest) cannot double-count session ids.
   const primaryDir = opts?.primaryDir ?? defaultBilledCodexHome()
   const launcherRoots = opts?.launcherRoots ?? defaultLauncherRoots()
+  // Explicit nest factory whose path is a realpath alias of the billed home:
+  // empty so a second factory cannot double-count the same tree. The no-arg
+  // singleton must not take this branch — CODEX_HOME may be that alias.
   const duplicateHome =
     codexDir !== undefined &&
     sameCodexHome(dir, primaryDir) &&
     resolve(dir) !== resolve(primaryDir)
-  const filterOverlap =
-    codexDir !== undefined &&
-    isNestedLauncherCodexHome(dir, { primaryDir, launcherRoots })
+  const nestHome = isNestedLauncherCodexHome(dir, { primaryDir, launcherRoots })
+  // Production `codex` singleton is createCodexProvider() with no args. When
+  // the resolved dir is a launcher nest and ~/.codex is a distinct existing
+  // tree, walk BOTH and drop nest sources whose session id is already billed.
+  const scanBoth = nestHome && codexDir === undefined
 
   return {
     name: 'codex',
@@ -1364,13 +1380,12 @@ export function createCodexProvider(
       return toolNameMap[rawTool] ?? rawTool
     },
 
-    // Same `dir` discoverSessionsInDir walks: <codexDir>/sessions (dated
-    // rollout files) and <codexDir>/archived_sessions. Honors CODEX_HOME.
+    // Trees discoverSessions actually walks. Honors CODEX_HOME; when the
+    // production singleton scans nest + billed home, both appear here.
     async probeRoots(): Promise<ProbeRoot[]> {
-      return [
-        { path: join(dir, 'sessions'), label: 'sessions' },
-        { path: join(dir, 'archived_sessions'), label: 'archived' },
-      ]
+      if (duplicateHome) return []
+      if (scanBoth) return [...rootsFor(primaryDir), ...rootsFor(dir)]
+      return rootsFor(dir)
     },
 
     async discoverSessions(): Promise<SessionSource[]> {
@@ -1378,12 +1393,12 @@ export function createCodexProvider(
       // distinct nest. isNestedLauncherCodexHome is false in that case.
       if (duplicateHome) return []
       const sources = await discoverSessionsInDir(dir)
-      if (!filterOverlap) return sources
-      const primaryIds = listRolloutSessionIds(primaryDir)
-      return sources.filter(source => {
-        const id = rolloutFileSessionId(source.path)
-        return !(id && primaryIds.has(id))
-      })
+      if (scanBoth) {
+        const billed = await discoverSessionsInDir(primaryDir)
+        return [...billed, ...dropOverlappingNestSources(sources, primaryDir)]
+      }
+      if (!nestHome) return sources
+      return dropOverlappingNestSources(sources, primaryDir)
     },
 
     createSessionParser(source: SessionSource, seenKeys: Set<string>): SessionParser {

tests/launcher-homes.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeEach, afterEach } from 'vitest'
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
 import { mkdtemp, mkdir, writeFile, rm, symlink } from 'fs/promises'
 import { join } from 'path'
 import { tmpdir } from 'os'
@@ -114,6 +114,8 @@ describe('Codex discover overlap-only nest filter', () => {
       expect(names(await provider.discoverSessions())).toEqual(['rollout-buzz.jsonl'])
       const roots = await provider.probeRoots!()
       expect(roots.map(r => r.path)).toEqual([
+        join(primary, 'sessions'),
+        join(primary, 'archived_sessions'),
         join(nested, 'sessions'),
         join(nested, 'archived_sessions'),
       ])
@@ -125,19 +127,51 @@ describe('Codex discover overlap-only nest filter', () => {
     }
   })
 
-  it('default factory with CODEX_HOME=nest does not drop unique nest rollouts when ~/.codex has its own', async () => {
+  it('no-arg factory discovers billed + unique nest and drops overlapping nest ids', async () => {
     const home = root
     const primary = join(home, '.codex')
     const nested = join(home, '.buzz', '.codex')
-    await writeCodexSession(primary, 'rollout-primary.jsonl')
-    await writeCodexSession(nested, 'rollout-buzz.jsonl')
+    await writeCodexSession(primary, 'rollout-billed.jsonl', 'sess-shared')
+    await writeCodexSession(primary, 'rollout-billed-only.jsonl', 'sess-billed')
+    await writeCodexSession(nested, 'rollout-renamed.jsonl', 'sess-shared')
+    await writeCodexSession(nested, 'rollout-buzz-only.jsonl', 'sess-buzz')
     const prevHome = process.env.HOME
     const prevCodex = process.env.CODEX_HOME
     process.env.HOME = home
     process.env.CODEX_HOME = nested
     try {
       const provider = createCodexProvider()
-      expect(names(await provider.discoverSessions())).toEqual(['rollout-buzz.jsonl'])
+      expect(names(await provider.discoverSessions()).sort()).toEqual([
+        'rollout-billed-only.jsonl',
+        'rollout-billed.jsonl',
+        'rollout-buzz-only.jsonl',
+      ])
+    } finally {
+      if (prevHome === undefined) delete process.env.HOME
+      else process.env.HOME = prevHome
+      if (prevCodex === undefined) delete process.env.CODEX_HOME
+      else process.env.CODEX_HOME = prevCodex
+    }
+  })
+
+  it('exported codex singleton dedups nest ids against billed home', async () => {
+    const home = root
+    const primary = join(home, '.codex')
+    const nested = join(home, '.buzz', '.codex')
+    await writeCodexSession(primary, 'rollout-billed.jsonl', 'sess-shared')
+    await writeCodexSession(nested, 'rollout-renamed.jsonl', 'sess-shared')
+    await writeCodexSession(nested, 'rollout-buzz-only.jsonl', 'sess-buzz')
+    const prevHome = process.env.HOME
+    const prevCodex = process.env.CODEX_HOME
+    process.env.HOME = home
+    process.env.CODEX_HOME = nested
+    vi.resetModules()
+    try {
+      const { codex } = await import('../src/providers/codex.js')
+      expect(names(await codex.discoverSessions()).sort()).toEqual([
+        'rollout-billed.jsonl',
+        'rollout-buzz-only.jsonl',
+      ])
     } finally {
       if (prevHome === undefined) delete process.env.HOME
       else process.env.HOME = prevHome