diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 80266ca..a0fa47f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -39,5 +39,5 @@ jobs:
       - name: Install dependencies
         run: npm ci
 
-      - name: Test native and mocked Windows project paths
-        run: npx vitest run src/lib/usage
+      - name: Test on Windows
+        run: npm run test
diff --git a/src/lib/agents/adapters/core-json.test.ts b/src/lib/agents/adapters/core-json.test.ts
index c1aa611..cd430fc 100644
--- a/src/lib/agents/adapters/core-json.test.ts
+++ b/src/lib/agents/adapters/core-json.test.ts
@@ -1,6 +1,7 @@
 import { mkdtemp, mkdir, writeFile } from "node:fs/promises"
 import { tmpdir } from "node:os"
-import { dirname, join } from "node:path"
+import { dirname, join, resolve, sep } from "node:path"
+import { pathToFileURL } from "node:url"
 import { describe, expect, test, vi } from "vitest"
 import type { AgentAdapter, DiscoveryContext, UsageSource } from "../types"
 import { ampAdapter } from "./amp"
@@ -37,9 +38,11 @@ describe("whole-file JSON adapters", () => {
     const home = await mkdtemp(join(tmpdir(), "stats-amp-"))
     const data = join(home, "data")
     const path = join(data, "amp", "threads", "T-one.json")
-    await json(path, { id: "thread", created: 1767312000000, env: { initial: { workspaceRoot: "/tmp/worktree/", trees: [{ uri: "file:///other", repository: { url: "/work/other" } }, { uri: "file:///tmp/worktree", repository: { url: "/work/app/." } }] } }, messages: [{ role: "assistant", usage: { model: "wrong", inputTokens: 99 } }], usageLedger: { events: [{ timestamp: "2026-01-02T00:00:00Z", model: "claude-sonnet", credits: 0.25, tokens: { input: 11, output: 5, cacheReadInputTokens: 3, cacheCreationInputTokens: 2 } }] } })
+    // Native paths and file URLs: Windows rejects a file URL without a drive.
+    const worktree = join(home, "worktree")
+    await json(path, { id: "thread", created: 1767312000000, env: { initial: { workspaceRoot: `${worktree}${sep}`, trees: [{ uri: pathToFileURL(join(home, "other")).href, repository: { url: "/work/other" } }, { uri: pathToFileURL(worktree).href, repository: { url: "/work/app/." } }] } }, messages: [{ role: "assistant", usage: { model: "wrong", inputTokens: 99 } }], usageLedger: { events: [{ timestamp: "2026-01-02T00:00:00Z", model: "claude-sonnet", credits: 0.25, tokens: { input: 11, output: 5, cacheReadInputTokens: 3, cacheCreationInputTokens: 2 } }] } })
     const source = await first(ampAdapter, home, { XDG_DATA_HOME: data })
-    expect((await ampAdapter.parse(source, parseContext())).events[0]).toMatchObject({ project: "/work/app", tokens: { input: 11, output: 5, cacheRead: 3, cacheWrite: 2, reasoning: 0 }, costUsd: 0.25, costSource: "reported" })
+    expect((await ampAdapter.parse(source, parseContext())).events[0]).toMatchObject({ project: resolve("/work/app"), tokens: { input: 11, output: 5, cacheRead: 3, cacheWrite: 2, reasoning: 0 }, costUsd: 0.25, costSource: "reported" })
   })
 
   test("Amp uses timestamped usage from actor snapshots", async () => {
@@ -48,7 +51,7 @@ describe("whole-file JSON adapters", () => {
     const path = join(data, "amp", "threads", "T-actor.json")
     await json(path, { id: "T-actor", created: 1767225600000, env: { initial: { workspaceRoot: "/work/app/" } }, messages: [{ messageId: "M-one", role: "assistant", createdAt: "2026-01-02T00:00:02Z", usage: { timestamp: "2026-01-02T00:00:01Z", model: "gpt-5", inputTokens: 7, outputTokens: 3 } }] })
     const source = await first(ampAdapter, home, { XDG_DATA_HOME: data })
-    expect((await ampAdapter.parse(source, parseContext())).events[0]).toMatchObject({ sessionId: "T-actor", project: "/work/app", timestamp: 1767312001000, model: "gpt-5", tokens: { input: 7, output: 3 } })
+    expect((await ampAdapter.parse(source, parseContext())).events[0]).toMatchObject({ sessionId: "T-actor", project: resolve("/work/app"), timestamp: 1767312001000, model: "gpt-5", tokens: { input: 7, output: 3 } })
   })
 
   test("Droid maps settings totals and project sidecar directory", async () => {
diff --git a/src/lib/sync/sync.test.ts b/src/lib/sync/sync.test.ts
index d4993fa..226dcc9 100644
--- a/src/lib/sync/sync.test.ts
+++ b/src/lib/sync/sync.test.ts
@@ -8,7 +8,7 @@ import {
 import { tmpdir } from "node:os"
 import { join } from "node:path"
 import Database from "better-sqlite3"
-import { afterEach, beforeEach, describe, expect, it } from "vitest"
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest"
 import { codexAdapter } from "../agents/adapters/codex"
 import { closeDb, getDb } from "../db/client.server"
 import { syncUsage } from "./sync.server"
@@ -72,12 +72,21 @@ describe("syncUsage", () => {
   beforeEach(() => {
     home = mkdtempSync(join(tmpdir(), "ts-home-"))
     dataDir = mkdtempSync(join(tmpdir(), "ts-data-"))
-    process.env.TELEMETRY_STATS_DATA_DIR = dataDir
-    process.env.HOME = home
+    vi.stubEnv("TELEMETRY_STATS_DATA_DIR", dataDir)
+    // Point every base directory adapters search at the temp home, so a sync never
+    // reads the real agent logs. os.homedir() reads USERPROFILE on Windows, not HOME.
+    vi.stubEnv("HOME", home)
+    vi.stubEnv("USERPROFILE", home)
+    vi.stubEnv("APPDATA", join(home, "AppData", "Roaming"))
+    vi.stubEnv("LOCALAPPDATA", join(home, "AppData", "Local"))
+    vi.stubEnv("XDG_DATA_HOME", join(home, ".local", "share"))
+    vi.stubEnv("XDG_CONFIG_HOME", join(home, ".config"))
     writePricingCache()
   })
 
   afterEach(() => {
+    vi.unstubAllEnvs()
+    vi.unstubAllGlobals()
     closeDb()
     rmSync(home, { recursive: true, force: true })
     rmSync(dataDir, { recursive: true, force: true })
@@ -653,6 +662,9 @@ describe("syncUsage", () => {
 
   it("leaves costs null and unpriced for unknown models without a catalog", async () => {
     rmSync(join(dataDir, "models-dev.json"))
+    // Without a cached catalog the loader fetches models.dev; keep the test offline so
+    // a slow network can't time it out and leave its sync running into the next test.
+    vi.stubGlobal("fetch", vi.fn().mockRejectedValue(new Error("offline")))
     writeOmpSession([
       HEADER,
       JSON.stringify({