diff --git a/.opencode/plans/1775725199925-glowing-orchid.md b/.opencode/plans/1775725199925-glowing-orchid.md
index 0968682..6bd7907 100644
--- a/.opencode/plans/1775725199925-glowing-orchid.md
+++ b/.opencode/plans/1775725199925-glowing-orchid.md
@@ -1,163 +1,188 @@
-# Plan: make local account state authoritative
+# Plan: rewrite token selection around a simple disk-first state model
 
-## Problem
+## Goal
 
-Current `accounts.json` state is not acting like a real source of truth for `/token`:
+Throw away the current layered selection/cooldown/state model and replace it with a small implementation that:
 
-- `active_account_id` is persisted but not actually used to drive selection
-- `last_known_usage` is mostly treated as a sort hint, then immediately replaced by a live refresh
-- `/token` live-refreshes every candidate it tries, so local limits are not truly trusted
-- the persisted snapshot contains duplicate derived fields (`used_percent`, `remaining_percent`, `exhausted`) in addition to canonical window and flag data
-- as a result, the file is hard to reason about: some fields look authoritative but are only decorative or transient
+- reads the main JSON file on every `/token` request
+- keeps only the minimum necessary account fields on disk
+- decides from file state first
+- refreshes usage only when missing or stale
+- validates the selected token before returning it
+- moves invalid accounts to `failed.json`
+- does not touch the helper scripts in this pass
 
-## Desired behavior
+## Required file model
 
-1. `accounts.json` is the source of truth for `/token` selection.
-2. If `active_account_id` exists and local state says the active account is usable, `/token` must try that account first.
-3. Only if local state says the active account is blocked or unusable should `/token` fall back to choosing another account.
-4. Fallback selection can keep the current ranking approach: most-used eligible account first.
-5. `/usage` should continue to refresh all accounts live.
-6. Persisted usage snapshots should store canonical data only, without duplicated derived fields.
+### Main state file
 
-## Recommended approach
+`accounts.json`
 
-### 1. Split `/token` selection into local selection and live validation
+```json
+{
+  "active_account": "user@example.com",
+  "accounts": [
+    {
+      "email": "user@example.com",
+      "access_token": "...",
+      "refresh_token": "...",
+      "token_refresh_at": 1710000000,
+      "usage": {
+        "primary": {
+          "used_percent": 72,
+          "reset_at": 1710018000
+        },
+        "secondary": {
+          "used_percent": 18,
+          "reset_at": 1710600000
+        }
+      },
+      "usage_checked_at": 1710000000,
+      "disabled": false
+    }
+  ]
+}
+```
 
-In `src/gibby/manager.py`:
+Only these fields should exist for account state.
 
-- Add `_find_active_account(state)` to resolve `state.active_account_id` to an `AccountRecord`
-- Add `_is_locally_blocked(account, current)` to decide from local file state only whether an account can be tried
-- Add `_build_selection_order(state, current)` that:
-  - returns the active account first if it exists and is not locally blocked
-  - otherwise falls back to the remaining eligible accounts sorted by current saved-usage ranking
-  - never duplicates the active account in the fallback list
+### Failed state file
 
-`_is_locally_blocked()` should use only persisted local state:
+`failed.json`
 
-- blocked if `cooldown_until > now`
-- blocked if `last_known_usage` exists and local usage indicates exhaustion
-- otherwise not blocked
+```json
+{
+  "accounts": [
+    {
+      "email": "bad@example.com",
+      "access_token": "...",
+      "refresh_token": "...",
+      "token_refresh_at": 1710000000,
+      "usage": {
+        "primary": {
+          "used_percent": 100,
+          "reset_at": 1710018000
+        },
+        "secondary": {
+          "used_percent": 100,
+          "reset_at": 1710600000
+        }
+      },
+      "usage_checked_at": 1710000000,
+      "disabled": false
+    }
+  ]
+}
+```
 
-This gives the exact behavior the user requested:
+Top-level must contain only `accounts`.
 
-- active account is mandatory first choice when nothing local blocks it
-- local file decides whether active is allowed before any network call
-- live refresh remains only a validation step for the chosen candidate
+## Selection rules
 
-### 2. Keep live refresh only for accounts actually attempted
+### Active account first
 
-In `src/gibby/manager.py`:
+For each `/token` request:
 
-- keep the current live refresh path (`refresh_account_usage`) once an account has been selected for an attempt
-- if active account passes local checks but fails live validation, persist the updated state and continue to the next candidate
-- if active account is locally blocked, skip live refresh for it during that `/token` call
+1. Read `accounts.json` fresh from disk.
+2. Resolve `active_account` by email.
+3. Evaluate active first.
 
-`/usage` stays as-is and continues refreshing all accounts live.
+### When an account is usable
 
-### 3. Clean up the persisted usage snapshot schema
+An account is usable when:
 
-In `src/gibby/models.py` and `src/gibby/store.py`:
+- `disabled == false`
+- `secondary.used_percent < 100`
+- `primary.used_percent < GIBBY_EXHAUSTED_USAGE_THRESHOLD`
 
-- stop persisting derived snapshot fields:
-  - `used_percent`
-  - `remaining_percent`
-  - `exhausted`
-- keep only canonical persisted snapshot data:
-  - `checked_at`
-  - `primary_window`
-  - `secondary_window`
-  - `limit_reached`
-  - `allowed`
+Default threshold remains `95`.
 
-Implementation direction:
+### Usage freshness
 
-- keep `UsageSnapshot` as the in-memory model for now, but derive:
-  - `used_percent`
-  - `remaining_percent`
-  - `exhausted`
-  from canonical fields when loading/parsing
-- update `store._snapshot_to_dict()` to write only canonical fields
-- update `store._snapshot_from_dict()` to reconstruct the full in-memory `UsageSnapshot` from canonical persisted fields
+Usage must be refreshed only when missing or stale.
 
-This keeps code churn smaller than a full model rewrite while making the file itself cleaner and more honest.
+Add env:
 
-### 4. Keep cooldown as the persisted local block, but make local exhaustion matter too
+- `GIBBY_USAGE_STALE_SECONDS`, default `3600`
 
-Local selection should not depend on a fresh API round-trip.
+Usage is stale when:
 
-For `/token`:
+- `usage` is missing
+- `usage_checked_at` is missing
+- `now - usage_checked_at > GIBBY_USAGE_STALE_SECONDS`
 
-- `cooldown_until` remains the strongest persisted block
-- if cooldown is clear but local `last_known_usage` still says exhausted, treat the account as locally blocked too
-- only accounts that pass local checks are eligible to be attempted live
+If active account usage is stale or missing, refresh usage for that account before deciding if it is usable.
 
-This changes current behavior in an important way:
+### Fallback selection
 
-- today, an account with expired or missing cooldown can still be live-refreshed even if local snapshot says exhausted
-- after the change, local state truly gates the initial decision
+If active account cannot be used, choose the next account by:
 
-### 5. Preserve existing fallback ranking for non-active accounts
+- filtering to usable accounts
+- sorting by highest primary `used_percent`
+- using file order as the tie-breaker
 
-After active account is rejected locally, keep the current fallback sort in `manager.py`:
+If a new account is chosen, write its email into `active_account` in `accounts.json`.
 
-- primary window used percent descending
-- secondary window used percent descending
+## Token flow
 
-That avoids a larger policy change in this pass and isolates the refactor to "trust local state first".
+For the chosen account:
 
-## Files to modify
+1. Ensure token is fresh enough.
+2. If `token_refresh_at` says refresh is needed, refresh token and persist new values.
+3. After selection decisions are finished and the token is ready, validate it by calling:
 
-- `/home/wzray/AI/gibby/src/gibby/manager.py`
-  - respect `active_account_id`
-  - add local-only eligibility predicate
-  - change selection order to active-first-when-locally-usable
-- `/home/wzray/AI/gibby/src/gibby/models.py`
-  - keep canonical usage derivation helpers centralized
-  - support reconstructing derived values from canonical fields
+`https://chatgpt.com/backend-api/codex/models`
+
+4. Only return the token if validation returns `200`.
+
+## Invalid account handling
+
+If refresh, usage auth, or final validation shows the token/account is invalid:
+
+1. Read current main state.
+2. Remove that full account object from `accounts.json`.
+3. Append the same full account object to `failed.json.accounts`.
+4. If it was the active account, clear `active_account` before reselection.
+5. Persist both files atomically.
+
+No `failed.txt` in the rewritten core flow.
+
+## Files to rewrite
+
+- `/home/wzray/AI/gibby/src/gibby/settings.py`
+  - keep only env needed for the new flow
 - `/home/wzray/AI/gibby/src/gibby/store.py`
-  - write canonical snapshot shape only
-  - read canonical snapshot shape into full in-memory model
+  - rewrite as simple JSON read/write helpers for `accounts.json` and `failed.json`
+- `/home/wzray/AI/gibby/src/gibby/client.py`
+  - keep only token refresh, usage fetch, and token validation calls
+- `/home/wzray/AI/gibby/src/gibby/manager.py`
+  - rewrite into one small service for `/token`
+- `/home/wzray/AI/gibby/src/gibby/app.py`
+  - keep thin FastAPI wiring for `/health` and `/token`
+
+## Files to remove or stop using
+
+- `/home/wzray/AI/gibby/src/gibby/models.py`
 - `/home/wzray/AI/gibby/src/gibby/account_ops.py`
-  - keep refresh path aligned with canonical snapshot handling
-  - reuse a local exhaustion predicate if helpful instead of duplicating logic
-- `/home/wzray/AI/gibby/tests/test_core.py`
-  - add and update selection behavior tests
-- `/home/wzray/AI/gibby/tests/test_account_ops.py`
-  - update snapshot persistence assumptions if needed
-- `/home/wzray/AI/gibby/tests/test_app.py`
-  - adjust fixture shapes only if response expectations change
-- `/home/wzray/AI/gibby/tests/test_refresh_limits.py`
-  - ensure live refresh still rewrites canonical local state correctly
-- `/home/wzray/AI/gibby/tests/test_oauth_helper.py`
-  - ensure oauth helper stores canonical snapshot shape correctly
 
-## Test plan
+Their logic should be folded into the new minimal data model and service flow instead of preserved.
 
-### Selection behavior
+## Out of scope for this pass
 
-Add or update tests in `tests/test_core.py` for:
-
-- active account is used first when locally allowed, even if another account has higher saved usage
-- active account is skipped without live refresh when `cooldown_until` is still active
-- active account is skipped without live refresh when local snapshot says exhausted
-- active account passes local checks but fails live refresh, then fallback account is tried
-- missing or stale `active_account_id` falls back cleanly to non-active selection logic
-- fallback ordering still prefers higher saved primary usage and uses secondary as tie-breaker
-
-### Snapshot/file behavior
-
-Add or update tests to verify:
-
-- `accounts.json` no longer writes `used_percent`, `remaining_percent`, or `exhausted`
-- loading canonical persisted snapshots still reconstructs full in-memory `UsageSnapshot`
-- `/usage`, `refresh_limits.py`, and `oauth_helper.py` still persist refreshed canonical state correctly
+- do not touch `scripts/oauth_helper.py`
+- do not touch `scripts/refresh_limits.py`
+- do not preserve old cooldown, failed.txt, dual-state, or derived snapshot machinery unless absolutely required to keep app booting during rewrite
 
 ## Verification
 
-- `uv run pytest -q tests/test_core.py tests/test_account_ops.py tests/test_app.py tests/test_refresh_limits.py tests/test_oauth_helper.py`
-- inspect a real `accounts.json` after `/usage` or `refresh_limits.py` and confirm snapshot entries contain only canonical fields
-- manually test `/token` with:
-  - a locally usable active account
-  - a locally blocked active account
-  - a dangling `active_account_id`
-- verify that active account is not live-refreshed when local file state already blocks it
+- `uv run pytest -q`
+- API tests for:
+  - `/health` returns `ok`
+  - `/token` returns `503` when file has no usable accounts
+  - `/token` prefers active account when usable
+  - `/token` rereads the file between requests
+  - stale usage triggers a refresh before decision
+  - fresh usage skips refresh
+  - invalid token moves full account object to `failed.json`
+  - fallback chooses highest primary usage among usable non-disabled accounts
+- direct file tests for exact `accounts.json` and `failed.json` schema
diff --git a/scripts/oauth_helper.py b/scripts/oauth_helper.py
index 2786ad2..d318712 100644
--- a/scripts/oauth_helper.py
+++ b/scripts/oauth_helper.py
@@ -10,20 +10,9 @@ from urllib.parse import parse_qs, urlparse
 
 sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))
 
-from gibby.account_ops import (
-    PermanentAccountFailure,
-    failed_identifier,
-    refresh_account_usage,
-    window_used_percent,
-)
 from gibby.client import OpenAIAPIError, OpenAIClient
-from gibby.models import AccountRecord, format_reset_in
-from gibby.oauth import (
-    build_authorize_url,
-    generate_pkce_pair,
-    generate_state,
-    make_account_id,
-)
+from gibby.models import AccountRecord, format_reset_in, parse_usage_payload
+from gibby.oauth import build_authorize_url, generate_pkce_pair, generate_state
 from gibby.settings import Settings
 from gibby.store import JsonStateStore
 
@@ -55,12 +44,10 @@ async def wait_for_callback(
             code, state = parse_redirect_url(parts[1])
             if not result.done():
                 result.set_result((code, state))
-
             while True:
                 line = await reader.readline()
                 if not line or line == b"\r\n":
                     break
-
             writer.write(
                 b"HTTP/1.1 200 OK\r\n"
                 b"Content-Type: text/plain; charset=utf-8\r\n"
@@ -91,35 +78,34 @@ async def exchange_and_store_account(
     verifier: str,
     set_active: bool,
 ) -> AccountRecord:
-    access_token, refresh_token, expires_at = await client.exchange_code(code, verifier)
+    access_token, refresh_token, token_refresh_at = await client.exchange_code(code, verifier)
     account = AccountRecord(
-        id=make_account_id(),
+        email="",
         access_token=access_token,
         refresh_token=refresh_token,
-        expires_at=expires_at,
+        token_refresh_at=token_refresh_at,
     )
     try:
-        usage = await refresh_account_usage(
-            account,
-            client,
-            client.settings.exhausted_usage_threshold,
-        )
-    except PermanentAccountFailure:
-        store.append_failed_identifier(failed_identifier(account))
-        raise
-    except OpenAIAPIError as exc:
-        account.last_error = str(exc)
+        payload = await client.fetch_usage_payload(account.access_token)
+        email = payload.get("email")
+        if isinstance(email, str) and email:
+            account.email = email
+        account.usage = parse_usage_payload(payload)
+        account.usage_checked_at = account.usage.checked_at
+    except OpenAIAPIError:
+        if not account.email:
+            raise
         store.upsert_account(account, set_active=set_active)
         print("Usage fetch failed, stored account without usage snapshot.")
         return account
 
     store.upsert_account(account, set_active=set_active)
     print(
-        f"token ready for {account.id}, "
-        f"primary {window_used_percent(usage.primary_window)}% "
-        f"reset in {format_reset_in(usage.primary_window.reset_at if usage.primary_window else None)}, "
-        f"secondary {window_used_percent(usage.secondary_window)}% "
-        f"reset in {format_reset_in(usage.secondary_window.reset_at if usage.secondary_window else None)}"
+        f"token ready for {account.email}, "
+        f"primary {account.usage.primary_window.used_percent if account.usage and account.usage.primary_window else 0}% "
+        f"reset in {format_reset_in(account.usage.primary_window.reset_at if account.usage and account.usage.primary_window else None)}, "
+        f"secondary {account.usage.secondary_window.used_percent if account.usage and account.usage.secondary_window else 0}% "
+        f"reset in {format_reset_in(account.usage.secondary_window.reset_at if account.usage and account.usage.secondary_window else None)}"
     )
     return account
 
@@ -168,14 +154,12 @@ async def run(
     store = JsonStateStore(settings.accounts_file, settings.failed_file)
     client = OpenAIClient(settings)
     try:
-        account = await exchange_and_store_account(
-            store, client, code, verifier, set_active
-        )
+        account = await exchange_and_store_account(store, client, code, verifier, set_active)
     finally:
         await client.aclose()
 
-    print(f"Stored account: {account.id}")
-    print(f"Access token expires at: {account.expires_at}")
+    print(f"Stored account: {account.email}")
+    print(f"Access token refresh at: {account.token_refresh_at}")
 
 
 def main() -> None:
@@ -192,7 +176,7 @@ def main() -> None:
         print("Timed out waiting for OAuth callback.")
     except ValueError as exc:
         print(str(exc))
-    except PermanentAccountFailure as exc:
+    except OpenAIAPIError as exc:
         print(str(exc))
 
 
diff --git a/scripts/refresh_limits.py b/scripts/refresh_limits.py
index 683f5a4..a0be3ac 100644
--- a/scripts/refresh_limits.py
+++ b/scripts/refresh_limits.py
@@ -7,14 +7,8 @@ from pathlib import Path
 
 sys.path.insert(0, str(Path(__file__).resolve().parents[1] / "src"))
 
-from gibby.account_ops import (
-    PermanentAccountFailure,
-    handle_failed_account,
-    refresh_account_usage,
-    window_used_percent,
-)
-from gibby.client import OpenAIClient
-from gibby.models import format_reset_in
+from gibby.client import OpenAIAPIError, OpenAIClient
+from gibby.models import format_reset_in, parse_usage_payload
 from gibby.settings import Settings
 from gibby.store import JsonStateStore
 
@@ -33,29 +27,23 @@ async def run(data_dir: Path | None = None) -> None:
     client = OpenAIClient(settings)
     try:
         for account in list(state.accounts):
-            previous_id = account.id
             try:
-                usage = await refresh_account_usage(
-                    account,
-                    client,
-                    settings.exhausted_usage_threshold,
-                )
-                store.update_active_account_id(state, previous_id, account.id)
+                payload = await client.fetch_usage_payload(account.access_token)
+                account.usage = parse_usage_payload(payload)
+                account.usage_checked_at = account.usage.checked_at
                 print(
-                    f"token ready for {account.id}, "
-                    f"primary {window_used_percent(usage.primary_window)}% "
-                    f"reset in {format_reset_in(usage.primary_window.reset_at if usage.primary_window else None)}, "
-                    f"secondary {window_used_percent(usage.secondary_window)}% "
-                    f"reset in {format_reset_in(usage.secondary_window.reset_at if usage.secondary_window else None)}"
+                    f"token ready for {account.email}, "
+                    f"primary {account.usage.primary_window.used_percent if account.usage.primary_window else 0}% "
+                    f"reset in {format_reset_in(account.usage.primary_window.reset_at if account.usage and account.usage.primary_window else None)}, "
+                    f"secondary {account.usage.secondary_window.used_percent if account.usage and account.usage.secondary_window else 0}% "
+                    f"reset in {format_reset_in(account.usage.secondary_window.reset_at if account.usage and account.usage.secondary_window else None)}"
                 )
-            except PermanentAccountFailure as exc:
-                account.last_error = str(exc)
-                handle_failed_account(store, account)
-                store.remove_account(state, account.id)
-                print(f"{account.id}: removed={exc}")
-            except Exception as exc:
-                account.last_error = str(exc)
-                print(f"{account.id}: error={exc}")
+            except OpenAIAPIError as exc:
+                if exc.permanent:
+                    store.move_to_failed(state, account.email)
+                    print(f"{account.email}: removed={exc}")
+                else:
+                    print(f"{account.email}: error={exc}")
         store.save(state)
     finally:
         await client.aclose()
diff --git a/src/gibby/account_ops.py b/src/gibby/account_ops.py
deleted file mode 100644
index bbd0b20..0000000
--- a/src/gibby/account_ops.py
+++ /dev/null
@@ -1,99 +0,0 @@
-from __future__ import annotations
-
-from gibby.client import OpenAIAPIError, OpenAIClient
-from gibby.models import (
-    AccountRecord,
-    UsageSnapshot,
-    UsageWindow,
-    compute_cooldown_until,
-    now_ts,
-    parse_usage_payload,
-)
-from gibby.store import JsonStateStore
-
-
-class PermanentAccountFailure(RuntimeError):
-    def __init__(self, account: AccountRecord, reason: str):
-        super().__init__(reason)
-        self.account = account
-
-
-def failed_identifier(account: AccountRecord) -> str:
-    return account.email or account.account_id or account.id
-
-
-def sync_account_identity(account: AccountRecord) -> None:
-    if account.email:
-        account.id = account.email
-
-
-def handle_failed_account(store: JsonStateStore, account: AccountRecord) -> None:
-    store.append_failed_identifier(failed_identifier(account))
-
-
-def window_used_percent(window: UsageWindow | None) -> int:
-    if window is None:
-        return 0
-    return window.used_percent
-
-
-def snapshot_is_exhausted(
-    snapshot: UsageSnapshot, exhausted_threshold: int = 100
-) -> bool:
-    if snapshot.exhausted:
-        return True
-    if snapshot.limit_reached or not snapshot.allowed:
-        return True
-    pri = snapshot.primary_window
-    sec = snapshot.secondary_window
-    if pri is not None and pri.used_percent >= exhausted_threshold:
-        return True
-    if sec is not None and sec.used_percent >= exhausted_threshold:
-        return True
-    return False
-
-
-async def ensure_fresh_access_token(
-    account: AccountRecord, client: OpenAIClient
-) -> None:
-    if account.expires_at > now_ts() + 30:
-        return
-    if not account.refresh_token:
-        raise RuntimeError("Missing refresh token")
-    try:
-        access_token, refresh_token, expires_at = await client.refresh_access_token(
-            account.refresh_token
-        )
-    except OpenAIAPIError as exc:
-        if exc.permanent:
-            raise PermanentAccountFailure(account, str(exc)) from exc
-        raise
-    account.access_token = access_token
-    account.refresh_token = refresh_token
-    account.expires_at = expires_at
-
-
-async def refresh_account_usage(
-    account: AccountRecord,
-    client: OpenAIClient,
-    exhausted_threshold: int = 100,
-) -> UsageSnapshot:
-    await ensure_fresh_access_token(account, client)
-    try:
-        payload = await client.fetch_usage_payload(account.access_token)
-    except OpenAIAPIError as exc:
-        if exc.permanent:
-            raise PermanentAccountFailure(account, str(exc)) from exc
-        raise
-    account.email = payload.get("email") or account.email
-    account.account_id = payload.get("account_id") or account.account_id
-    sync_account_identity(account)
-    usage = parse_usage_payload(payload)
-    account.last_known_usage = usage
-    account.last_error = None
-    account.cooldown_until = (
-        compute_cooldown_until(usage, exhausted_threshold)
-        if snapshot_is_exhausted(usage, exhausted_threshold)
-        else None
-    )
-    return usage
diff --git a/src/gibby/app.py b/src/gibby/app.py
index 337bea3..f81e500 100644
--- a/src/gibby/app.py
+++ b/src/gibby/app.py
@@ -49,10 +49,6 @@ def create_app(manager: AccountManager | None = None) -> FastAPI:
         except NoUsableAccountError as exc:
             return JSONResponse(status_code=503, content={"error": str(exc)})
 
-    @app.get("/usage", response_model=None)
-    async def usage() -> Any:
-        return await app.state.manager.get_usage_report()
-
     return app
 
 
diff --git a/src/gibby/client.py b/src/gibby/client.py
index da4e2cd..80d612a 100644
--- a/src/gibby/client.py
+++ b/src/gibby/client.py
@@ -8,6 +8,8 @@ from gibby.models import UsageSnapshot, now_ts, parse_usage_payload
 from gibby.oauth import TOKEN_URL, USAGE_URL
 from gibby.settings import Settings
 
+MODELS_URL = "https://chatgpt.com/backend-api/codex/models"
+
 
 class OpenAIAPIError(RuntimeError):
     def __init__(
@@ -73,8 +75,8 @@ class OpenAIClient:
         response = await self.http_client.post(TOKEN_URL, data=payload)
         _raise_for_openai_error(response)
         body = response.json()
-        expires_at = now_ts() + int(body["expires_in"])
-        return body["access_token"], body["refresh_token"], expires_at
+        refresh_at = now_ts() + int(body["expires_in"])
+        return body["access_token"], body["refresh_token"], refresh_at
 
     async def refresh_access_token(self, refresh_token: str) -> tuple[str, str, int]:
         payload = {
@@ -85,17 +87,11 @@ class OpenAIClient:
         response = await self.http_client.post(TOKEN_URL, data=payload)
         _raise_for_openai_error(response)
         body = response.json()
-        expires_at = now_ts() + int(body["expires_in"])
-        next_refresh = str(body.get("refresh_token") or refresh_token)
-        return body["access_token"], next_refresh, expires_at
+        refresh_at = now_ts() + int(body["expires_in"])
+        return body["access_token"], str(body.get("refresh_token") or refresh_token), refresh_at
 
     async def fetch_usage_payload(self, access_token: str) -> dict:
-        headers = {
-            "Authorization": f"Bearer {access_token}",
-            "User-Agent": "CodexProxy",
-            "Accept": "application/json",
-        }
-        response = await self.http_client.get(USAGE_URL, headers=headers)
+        response = await self.http_client.get(USAGE_URL, headers=self._headers(access_token))
         _raise_for_openai_error(response)
         payload = response.json()
         if not isinstance(payload, dict):
@@ -106,3 +102,15 @@ class OpenAIClient:
 
     async def fetch_usage(self, access_token: str) -> UsageSnapshot:
         return parse_usage_payload(await self.fetch_usage_payload(access_token))
+
+    async def validate_token(self, access_token: str) -> bool:
+        response = await self.http_client.get(MODELS_URL, headers=self._headers(access_token))
+        return response.status_code == 200
+
+    @staticmethod
+    def _headers(access_token: str) -> dict[str, str]:
+        return {
+            "Authorization": f"Bearer {access_token}",
+            "User-Agent": "CodexProxy",
+            "Accept": "application/json",
+        }
diff --git a/src/gibby/manager.py b/src/gibby/manager.py
index d3b67e4..fbd9c85 100644
--- a/src/gibby/manager.py
+++ b/src/gibby/manager.py
@@ -5,22 +5,8 @@ import logging
 from dataclasses import asdict
 from typing import Any
 
-from gibby.account_ops import (
-    PermanentAccountFailure,
-    failed_identifier,
-    handle_failed_account,
-    refresh_account_usage,
-    snapshot_is_exhausted,
-    window_used_percent,
-)
-from gibby.client import OpenAIClient
-from gibby.models import (
-    AccountRecord,
-    StateFile,
-    build_limit,
-    format_reset_in,
-    now_ts,
-)
+from gibby.client import OpenAIAPIError, OpenAIClient
+from gibby.models import AccountRecord, StateFile, UsageSnapshot, build_limit, now_ts, parse_usage_payload
 from gibby.settings import Settings
 from gibby.store import JsonStateStore
 
@@ -40,232 +26,144 @@ class AccountManager:
 
     async def issue_token_response(self) -> dict[str, Any]:
         async with self._lock:
-            state = self.store.load()
-            if not state.accounts:
-                logger.error("No accounts configured")
-                raise NoUsableAccountError("No accounts configured")
+            while True:
+                state = self.store.load()
+                if not state.accounts:
+                    raise NoUsableAccountError("No usable account available")
 
-            current = now_ts()
-            for account in self._build_selection_order(state, current):
-                payload = await self._try_issue_token(state, account)
-                if payload is not None:
-                    return payload
+                account = await self._select_account(state)
+                if account is None:
+                    raise NoUsableAccountError("No usable account available")
 
-            self.store.save(state)
-            logger.error(
-                "No usable account available: %s",
-                [
-                    {
-                        "id": account.id,
-                        "cooldown_until": account.cooldown_until,
-                        "last_error": account.last_error,
-                    }
-                    for account in state.accounts
-                ],
-            )
-            raise NoUsableAccountError("No usable account available")
-
-    async def _try_issue_token(
-        self, state: StateFile, account: AccountRecord
-    ) -> dict[str, Any] | None:
-        previous_id = account.id
-        try:
-            usage = await refresh_account_usage(
-                account,
-                self.client,
-                self.settings.exhausted_usage_threshold,
-            )
-        except PermanentAccountFailure as exc:
-            account.last_error = str(exc)
-            handle_failed_account(self.store, account)
-            self.store.remove_account(state, account.id)
-            self.store.save(state)
-            logger.error(
-                "Removed failed account %s (%s): %s",
-                account.id,
-                failed_identifier(account),
-                exc,
-            )
-            return None
-        except Exception as exc:
-            account.last_error = str(exc)
-            logger.exception(
-                "Account %s failed during refresh or usage check",
-                account.id,
-            )
-            self.store.update_active_account_id(state, previous_id, account.id)
-            self.store.save(state)
-            return None
-
-        self.store.update_active_account_id(state, previous_id, account.id)
-        account.last_known_usage = usage
-        account.last_error = None
-        if snapshot_is_exhausted(usage, self.settings.exhausted_usage_threshold):
-            logger.warning(
-                "Account %s exhausted: primary=%s%% secondary=%s%% cooldown_until=%s",
-                account.id,
-                window_used_percent(usage.primary_window),
-                window_used_percent(usage.secondary_window),
-                account.cooldown_until,
-            )
-            self.store.save(state)
-            return None
-
-        account.cooldown_until = None
-        state.active_account_id = account.id
-        self.store.save(state)
-        logger.info(
-            "token issued for %s, primary %s%% reset in %s, secondary %s%% reset in %s",
-            account.id,
-            window_used_percent(usage.primary_window),
-            format_reset_in(
-                usage.primary_window.reset_at if usage.primary_window else None
-            ),
-            window_used_percent(usage.secondary_window),
-            format_reset_in(
-                usage.secondary_window.reset_at if usage.secondary_window else None
-            ),
-        )
-        return {
-            "token": account.access_token,
-            "limit": build_limit(usage),
-            "usage": {
-                "primary_window": asdict(usage.primary_window)
-                if usage.primary_window
-                else None,
-                "secondary_window": asdict(usage.secondary_window)
-                if usage.secondary_window
-                else None,
-            },
-        }
-
-    async def get_usage_report(self) -> dict[str, Any]:
-        async with self._lock:
-            state = self.store.load()
-            accounts_report: list[dict[str, Any]] = []
-
-            for account in list(state.accounts):
-                previous_id = account.id
-                try:
-                    usage = await refresh_account_usage(
-                        account,
-                        self.client,
-                    )
-                except PermanentAccountFailure as exc:
-                    account.last_error = str(exc)
-                    identifier = failed_identifier(account)
-                    handle_failed_account(self.store, account)
-                    self.store.remove_account(state, account.id)
-                    logger.error(
-                        "Removed failed account %s (%s): %s",
-                        account.id,
-                        identifier,
-                        exc,
-                    )
-                    accounts_report.append(
-                        {
-                            "id": account.id,
-                            "email": account.email,
-                            "status": "removed",
-                            "error": str(exc),
-                        }
-                    )
-                    continue
-                except Exception as exc:
-                    account.last_error = str(exc)
-                    logger.exception(
-                        "Account %s failed during usage refresh", account.id
-                    )
-                    accounts_report.append(
-                        {
-                            "id": account.id,
-                            "email": account.email,
-                            "status": "error",
-                            "error": str(exc),
-                            "cooldown_until": account.cooldown_until,
-                        }
-                    )
+                state = self.store.load()
+                account = self._find_account(state, account.email)
+                if account is None:
                     continue
 
-                self.store.update_active_account_id(state, previous_id, account.id)
-                status = (
-                    "depleted"
-                    if snapshot_is_exhausted(
-                        usage, self.settings.exhausted_usage_threshold
-                    )
-                    else "ok"
-                )
-                accounts_report.append(
-                    {
-                        "id": account.id,
-                        "email": account.email,
-                        "status": status,
-                        "used_percent": usage.used_percent,
-                        "remaining_percent": usage.remaining_percent,
-                        "cooldown_until": account.cooldown_until,
+                if not await self._ensure_fresh_token(state, account):
+                    continue
+                self.store.save(state)
+
+                if not await self.client.validate_token(account.access_token):
+                    logger.warning("account %s failed token validation", account.email)
+                    self.store.move_to_failed(state, account.email)
+                    self.store.save(state)
+                    continue
+
+                state.active_account = account.email
+                self.store.save(state)
+                usage = account.usage or UsageSnapshot(checked_at=now_ts())
+                logger.info("token issued for %s", account.email)
+                return {
+                    "token": account.access_token,
+                    "limit": build_limit(usage),
+                    "usage": {
                         "primary_window": asdict(usage.primary_window)
                         if usage.primary_window
                         else None,
                         "secondary_window": asdict(usage.secondary_window)
                         if usage.secondary_window
                         else None,
-                    }
-                )
+                    },
+                }
 
+    async def _select_account(self, state: StateFile) -> AccountRecord | None:
+        now = now_ts()
+        active = self._find_account(state, state.active_account)
+        if active is not None:
+            prepared = await self._prepare_account(state, active, now)
+            if prepared is not None:
+                return prepared
+
+        candidates: list[AccountRecord] = []
+        for account in state.accounts:
+            if active is not None and account.email == active.email:
+                continue
+            prepared = await self._prepare_account(state, account, now)
+            if prepared is not None:
+                candidates.append(prepared)
+
+        if not candidates:
             self.store.save(state)
-            return {
-                "accounts": accounts_report,
-                "active_account_id": state.active_account_id,
-                "count": len(accounts_report),
-            }
+            return None
 
-    def _find_active_account(self, state: StateFile) -> AccountRecord | None:
-        if not state.active_account_id:
+        selected = max(candidates, key=lambda item: self._primary_used(item))
+        if state.active_account != selected.email:
+            state.active_account = selected.email
+            self.store.save(state)
+        return selected
+
+    async def _prepare_account(
+        self, state: StateFile, account: AccountRecord, now: int
+    ) -> AccountRecord | None:
+        if account.disabled:
+            return None
+        if self._usage_is_stale(account, now):
+            try:
+                if not await self._refresh_usage(state, account):
+                    return None
+            except OpenAIAPIError as exc:
+                if exc.permanent:
+                    logger.warning("account %s failed usage refresh", account.email)
+                    self.store.move_to_failed(state, account.email)
+                    self.store.save(state)
+                return None
+        if self._is_usable(account):
+            return account
+        return None
+
+    async def _refresh_usage(self, state: StateFile, account: AccountRecord) -> bool:
+        if not await self._ensure_fresh_token(state, account):
+            return False
+        payload = await self.client.fetch_usage_payload(account.access_token)
+        email = payload.get("email")
+        if isinstance(email, str) and email:
+            account.email = email
+        account.usage = parse_usage_payload(payload)
+        account.usage_checked_at = account.usage.checked_at
+        self.store.save(state)
+        return True
+
+    async def _ensure_fresh_token(self, state: StateFile, account: AccountRecord) -> bool:
+        if account.token_refresh_at > now_ts() + self.settings.token_refresh_buffer_seconds:
+            return True
+        try:
+            access_token, refresh_token, refresh_at = await self.client.refresh_access_token(
+                account.refresh_token
+            )
+        except OpenAIAPIError as exc:
+            if exc.permanent:
+                logger.warning("account %s failed token refresh", account.email)
+                self.store.move_to_failed(state, account.email)
+                self.store.save(state)
+                return False
+            raise
+        account.access_token = access_token
+        account.refresh_token = refresh_token
+        account.token_refresh_at = refresh_at
+        return True
+
+    def _find_account(self, state: StateFile, email: str | None) -> AccountRecord | None:
+        if not email:
             return None
         for account in state.accounts:
-            if account.id == state.active_account_id:
+            if account.email == email:
                 return account
         return None
 
-    def _is_locally_blocked(self, account: AccountRecord, current: int) -> bool:
-        if account.cooldown_until and account.cooldown_until > current:
+    def _usage_is_stale(self, account: AccountRecord, now: int) -> bool:
+        if account.usage is None or account.usage_checked_at is None:
             return True
-        if account.last_known_usage and snapshot_is_exhausted(
-            account.last_known_usage, self.settings.exhausted_usage_threshold
-        ):
-            return True
-        return False
+        return now - account.usage_checked_at > self.settings.usage_stale_seconds
 
-    def _build_selection_order(
-        self, state: StateFile, current: int
-    ) -> list[AccountRecord]:
-        active = self._find_active_account(state)
-        excluded_ids = {active.id} if active is not None else set()
-        fallback = self._iter_candidates(state, current, excluded_ids)
-        if active is None:
-            return fallback
-        if self._is_locally_blocked(active, current):
-            logger.info("active account %s is blocked by local state", active.id)
-            return fallback
-        return [active, *fallback]
+    def _is_usable(self, account: AccountRecord) -> bool:
+        if account.disabled or account.usage is None:
+            return False
+        primary = account.usage.primary_window.used_percent if account.usage.primary_window else 0
+        secondary = account.usage.secondary_window.used_percent if account.usage.secondary_window else 0
+        return primary < self.settings.exhausted_usage_threshold and secondary < 100
 
-    def _iter_candidates(
-        self, state: StateFile, current: int, excluded_ids: set[str] | None = None
-    ) -> list[AccountRecord]:
-        excluded_ids = excluded_ids or set()
-        available = [
-            account
-            for account in state.accounts
-            if account.id not in excluded_ids
-            and not self._is_locally_blocked(account, current)
-        ]
-        return sorted(available, key=self._candidate_sort_key, reverse=True)
-
-    def _candidate_sort_key(self, account: AccountRecord) -> tuple[int, int]:
-        snapshot = account.last_known_usage
-        if snapshot is None:
-            return (0, 0)
-        return (
-            window_used_percent(snapshot.primary_window),
-            window_used_percent(snapshot.secondary_window),
-        )
+    def _primary_used(self, account: AccountRecord) -> int:
+        if account.usage is None or account.usage.primary_window is None:
+            return 0
+        return account.usage.primary_window.used_percent
diff --git a/src/gibby/models.py b/src/gibby/models.py
index 24988a7..924339e 100644
--- a/src/gibby/models.py
+++ b/src/gibby/models.py
@@ -4,46 +4,51 @@ import time
 from dataclasses import dataclass, field
 from typing import Any
 
-UNKNOWN_EXHAUSTED_BACKOFF_SECONDS = 300
-
 
 @dataclass(slots=True)
 class UsageWindow:
-    used_percent: int
-    limit_window_seconds: int
-    reset_after_seconds: int
-    reset_at: int
+    used_percent: int = 0
+    reset_at: int | None = None
 
 
 @dataclass(slots=True)
 class UsageSnapshot:
     checked_at: int
-    used_percent: int
-    remaining_percent: int
-    exhausted: bool
-    primary_window: UsageWindow | None
-    secondary_window: UsageWindow | None
-    limit_reached: bool
-    allowed: bool
+    primary_window: UsageWindow | None = None
+    secondary_window: UsageWindow | None = None
+    limit_reached: bool = False
+    allowed: bool = True
+
+    @property
+    def used_percent(self) -> int:
+        return max(
+            (window.used_percent for window in (self.primary_window, self.secondary_window) if window),
+            default=0,
+        )
+
+    @property
+    def remaining_percent(self) -> int:
+        return max(0, 100 - self.used_percent)
+
+    @property
+    def exhausted(self) -> bool:
+        return self.used_percent >= 100 or self.limit_reached or not self.allowed
 
 
 @dataclass(slots=True)
 class AccountRecord:
-    id: str
-    email: str | None = None
-    account_id: str | None = None
+    email: str
     access_token: str = ""
     refresh_token: str = ""
-    expires_at: int = 0
-    cooldown_until: int | None = None
-    last_known_usage: UsageSnapshot | None = None
-    last_error: str | None = None
+    token_refresh_at: int = 0
+    usage: UsageSnapshot | None = None
+    usage_checked_at: int | None = None
+    disabled: bool = False
 
 
 @dataclass(slots=True)
 class StateFile:
-    version: int = 1
-    active_account_id: str | None = None
+    active_account: str | None = None
     accounts: list[AccountRecord] = field(default_factory=list)
 
 
@@ -51,13 +56,20 @@ def now_ts() -> int:
     return int(time.time())
 
 
+def clamp_percent(value: Any) -> int:
+    try:
+        number = int(round(float(value)))
+    except (TypeError, ValueError):
+        return 0
+    return max(0, min(100, number))
+
+
 def format_reset_in(reset_at: int | None, current: int | None = None) -> str:
     if not reset_at:
         return "n/a"
     remaining = reset_at - (current if current is not None else now_ts())
     if remaining <= 0:
         return "now"
-
     days, remainder = divmod(remaining, 86400)
     hours, remainder = divmod(remainder, 3600)
     minutes, seconds = divmod(remainder, 60)
@@ -73,70 +85,13 @@ def format_reset_in(reset_at: int | None, current: int | None = None) -> str:
     return " ".join(parts)
 
 
-def clamp_percent(value: Any) -> int:
-    try:
-        num = float(value)
-    except TypeError, ValueError:
-        return 0
-    if num < 0:
-        return 0
-    if num > 100:
-        return 100
-    return int(round(num))
-
-
 def parse_usage_window(window: dict[str, Any] | None) -> UsageWindow | None:
     if not isinstance(window, dict):
         return None
+    reset_at = window.get("reset_at")
     return UsageWindow(
         used_percent=clamp_percent(window.get("used_percent") or 0),
-        limit_window_seconds=int(window.get("limit_window_seconds") or 0),
-        reset_after_seconds=int(window.get("reset_after_seconds") or 0),
-        reset_at=int(window.get("reset_at") or 0),
-    )
-
-
-def _effective_used_percent(
-    primary: UsageWindow | None, secondary: UsageWindow | None
-) -> int:
-    return max(
-        (window.used_percent for window in (primary, secondary) if window), default=0
-    )
-
-
-def _snapshot_is_exhausted(
-    primary: UsageWindow | None,
-    secondary: UsageWindow | None,
-    limit_reached: bool,
-    allowed: bool,
-) -> bool:
-    return (
-        _effective_used_percent(primary, secondary) >= 100
-        or limit_reached
-        or not allowed
-    )
-
-
-def build_usage_snapshot(
-    *,
-    checked_at: int,
-    primary_window: UsageWindow | None,
-    secondary_window: UsageWindow | None,
-    limit_reached: bool,
-    allowed: bool,
-) -> UsageSnapshot:
-    used_percent = _effective_used_percent(primary_window, secondary_window)
-    return UsageSnapshot(
-        checked_at=checked_at,
-        used_percent=used_percent,
-        remaining_percent=max(0, 100 - used_percent),
-        exhausted=_snapshot_is_exhausted(
-            primary_window, secondary_window, limit_reached, allowed
-        ),
-        primary_window=primary_window,
-        secondary_window=secondary_window,
-        limit_reached=limit_reached,
-        allowed=allowed,
+        reset_at=int(reset_at) if reset_at else None,
     )
 
 
@@ -145,16 +100,12 @@ def parse_usage_payload(
 ) -> UsageSnapshot:
     checked_at = checked_at or now_ts()
     rate_limit = payload.get("rate_limit") or {}
-    primary = parse_usage_window(rate_limit.get("primary_window"))
-    secondary = parse_usage_window(rate_limit.get("secondary_window"))
-    limit_reached = bool(rate_limit.get("limit_reached"))
-    allowed = bool(rate_limit.get("allowed", True))
-    return build_usage_snapshot(
+    return UsageSnapshot(
         checked_at=checked_at,
-        primary_window=primary,
-        secondary_window=secondary,
-        limit_reached=limit_reached,
-        allowed=allowed,
+        primary_window=parse_usage_window(rate_limit.get("primary_window")),
+        secondary_window=parse_usage_window(rate_limit.get("secondary_window")),
+        limit_reached=bool(rate_limit.get("limit_reached")),
+        allowed=bool(rate_limit.get("allowed", True)),
     )
 
 
@@ -165,47 +116,3 @@ def build_limit(snapshot: UsageSnapshot) -> dict[str, int | bool]:
         "exhausted": snapshot.exhausted,
         "needs_prepare": False,
     }
-
-
-def _window_reset_deadline(window: UsageWindow, checked_at: int) -> int | None:
-    if window.reset_at > checked_at:
-        return window.reset_at
-    if window.reset_after_seconds > 0:
-        return checked_at + window.reset_after_seconds
-    if window.limit_window_seconds > 0:
-        return checked_at + window.limit_window_seconds
-    return None
-
-
-def compute_cooldown_until(
-    snapshot: UsageSnapshot, exhausted_threshold: int = 100
-) -> int | None:
-    effective_used = _effective_used_percent(
-        snapshot.primary_window, snapshot.secondary_window
-    )
-    if (
-        effective_used < exhausted_threshold
-        and not snapshot.limit_reached
-        and snapshot.allowed
-    ):
-        return None
-    blocking_windows = [
-        window
-        for window in (snapshot.primary_window, snapshot.secondary_window)
-        if window and window.used_percent >= exhausted_threshold
-    ]
-    if not blocking_windows and (snapshot.limit_reached or not snapshot.allowed):
-        blocking_windows = [
-            window
-            for window in (snapshot.primary_window, snapshot.secondary_window)
-            if window
-        ]
-
-    deadlines = [
-        deadline
-        for window in blocking_windows
-        if (deadline := _window_reset_deadline(window, snapshot.checked_at)) is not None
-    ]
-    if deadlines:
-        return max(deadlines)
-    return snapshot.checked_at + UNKNOWN_EXHAUSTED_BACKOFF_SECONDS
diff --git a/src/gibby/settings.py b/src/gibby/settings.py
index e58bfe2..aa4d8f2 100644
--- a/src/gibby/settings.py
+++ b/src/gibby/settings.py
@@ -13,15 +13,20 @@ class Settings:
     data_dir: Path = Path(os.getenv("DATA_DIR", "data"))
     bind_host: str = os.getenv("GIBBY_BIND_HOST", "0.0.0.0")
     port: int = int(os.getenv("GIBBY_PORT", "8080"))
+    request_timeout: float = float(os.getenv("GIBBY_REQUEST_TIMEOUT", "40"))
+    usage_stale_seconds: int = int(os.getenv("GIBBY_USAGE_STALE_SECONDS", "3600"))
     exhausted_usage_threshold: int = int(
         os.getenv("GIBBY_EXHAUSTED_USAGE_THRESHOLD", "95")
     )
+    token_refresh_buffer_seconds: int = int(
+        os.getenv("GIBBY_TOKEN_REFRESH_BUFFER_SECONDS", "30")
+    )
+
     callback_host: str = os.getenv("GIBBY_CALLBACK_HOST", "localhost")
     callback_port: int = int(os.getenv("GIBBY_CALLBACK_PORT", "1455"))
     oauth_client_id: str = os.getenv("GIBBY_OAUTH_CLIENT_ID", DEFAULT_CLIENT_ID)
     oauth_scope: str = os.getenv("GIBBY_OAUTH_SCOPE", DEFAULT_SCOPE)
     originator: str = os.getenv("GIBBY_ORIGINATOR", "opencode")
-    request_timeout: float = float(os.getenv("GIBBY_REQUEST_TIMEOUT", "40"))
 
     @property
     def accounts_file(self) -> Path:
@@ -29,7 +34,7 @@ class Settings:
 
     @property
     def failed_file(self) -> Path:
-        return self.data_dir / "failed.txt"
+        return self.data_dir / "failed.json"
 
     @property
     def redirect_uri(self) -> str:
diff --git a/src/gibby/store.py b/src/gibby/store.py
index fed3683..66bf674 100644
--- a/src/gibby/store.py
+++ b/src/gibby/store.py
@@ -2,170 +2,153 @@ from __future__ import annotations
 
 import json
 import os
-from dataclasses import asdict
 from pathlib import Path
 from tempfile import NamedTemporaryFile
 from typing import Any
 
-from gibby.models import (
-    AccountRecord,
-    StateFile,
-    UsageSnapshot,
-    UsageWindow,
-    build_usage_snapshot,
-    parse_usage_window,
-)
+from gibby.models import AccountRecord, StateFile, UsageSnapshot, UsageWindow
 
 
 class JsonStateStore:
     def __init__(self, path: Path, failed_path: Path | None = None):
         self.path = path
-        self.failed_path = failed_path or path.with_name("failed.txt")
+        self.failed_path = failed_path or path.with_name("failed.json")
 
     def load(self) -> StateFile:
-        try:
-            if not self.path.exists():
-                return StateFile()
-            raw = json.loads(self.path.read_text())
-            if not isinstance(raw, dict):
-                raise RuntimeError("accounts.json must contain a JSON object")
-            accounts = [
-                self._account_from_dict(item) for item in raw.get("accounts", [])
-            ]
-            return StateFile(
-                version=int(raw.get("version", 1)),
-                active_account_id=raw.get("active_account_id"),
-                accounts=accounts,
-            )
-        except (OSError, json.JSONDecodeError, TypeError, ValueError, KeyError) as exc:
-            raise RuntimeError(f"Invalid accounts state file: {exc}") from exc
+        raw = self._read_json(self.path, {"active_account": None, "accounts": []})
+        accounts = [self._account_from_dict(item) for item in raw.get("accounts", [])]
+        return StateFile(active_account=raw.get("active_account"), accounts=accounts)
 
     def save(self, state: StateFile) -> None:
-        self.path.parent.mkdir(parents=True, exist_ok=True)
         payload = {
-            "version": state.version,
-            "active_account_id": state.active_account_id,
+            "active_account": state.active_account,
             "accounts": [self._account_to_dict(account) for account in state.accounts],
         }
-        with NamedTemporaryFile(
-            "w", delete=False, dir=self.path.parent, encoding="utf-8"
-        ) as tmp:
-            json.dump(payload, tmp, ensure_ascii=True, indent=2)
-            tmp.write("\n")
-            temp_name = tmp.name
-        os.replace(temp_name, self.path)
+        self._write_json(self.path, payload)
+
+    def load_failed_accounts(self) -> list[AccountRecord]:
+        raw = self._read_json(self.failed_path, {"accounts": []})
+        return [self._account_from_dict(item) for item in raw.get("accounts", [])]
+
+    def append_failed_account(self, account: AccountRecord) -> None:
+        payload = self._read_json(self.failed_path, {"accounts": []})
+        payload.setdefault("accounts", []).append(self._account_to_dict(account))
+        self._write_json(self.failed_path, {"accounts": payload["accounts"]})
 
     def upsert_account(
         self, account: AccountRecord, set_active: bool = False
     ) -> AccountRecord:
         state = self.load()
         for index, existing in enumerate(state.accounts):
-            if existing.email and account.email and existing.email == account.email:
-                if state.active_account_id == existing.id:
-                    state.active_account_id = account.id
-                state.accounts[index] = account
-                break
-            if existing.id == account.id:
+            if existing.email == account.email:
                 state.accounts[index] = account
                 break
         else:
             state.accounts.append(account)
-        if set_active or not state.active_account_id:
-            state.active_account_id = account.id
+        if set_active or not state.active_account:
+            state.active_account = account.email
         self.save(state)
         return account
 
-    def remove_account(self, state: StateFile, account_id: str) -> None:
-        state.accounts = [
-            account for account in state.accounts if account.id != account_id
-        ]
-        if state.active_account_id == account_id:
-            state.active_account_id = state.accounts[0].id if state.accounts else None
+    def remove_account(self, state: StateFile, email: str) -> None:
+        state.accounts = [account for account in state.accounts if account.email != email]
+        if state.active_account == email:
+            state.active_account = None
 
-    @staticmethod
-    def update_active_account_id(
-        state: StateFile, previous_id: str, current_id: str
+    def move_to_failed(self, state: StateFile, email: str) -> None:
+        account = next((account for account in state.accounts if account.email == email), None)
+        if account is None:
+            return
+        self.remove_account(state, email)
+        self.append_failed_account(account)
+
+    def update_active_account(
+        self, state: StateFile, previous_email: str, current_email: str
     ) -> None:
-        if state.active_account_id == previous_id:
-            state.active_account_id = current_id
+        if state.active_account == previous_email:
+            state.active_account = current_email
 
-    def append_failed_identifier(self, identifier: str) -> None:
-        identifier = identifier.strip()
-        if not identifier:
-            return
-        self.failed_path.parent.mkdir(parents=True, exist_ok=True)
-        existing = set()
-        if self.failed_path.exists():
-            existing = {
-                line.strip()
-                for line in self.failed_path.read_text().splitlines()
-                if line.strip()
-            }
-        if identifier in existing:
-            return
-        with self.failed_path.open("a", encoding="utf-8") as file:
-            file.write(f"{identifier}\n")
+    def _read_json(self, path: Path, default: dict[str, Any]) -> dict[str, Any]:
+        if not path.exists():
+            return default
+        try:
+            raw = json.loads(path.read_text())
+        except (OSError, json.JSONDecodeError) as exc:
+            raise RuntimeError(f"Invalid state file {path}: {exc}") from exc
+        if not isinstance(raw, dict):
+            raise RuntimeError(f"State file {path} must contain a JSON object")
+        return raw
+
+    def _write_json(self, path: Path, payload: dict[str, Any]) -> None:
+        path.parent.mkdir(parents=True, exist_ok=True)
+        with NamedTemporaryFile(
+            "w", delete=False, dir=path.parent, encoding="utf-8"
+        ) as tmp:
+            json.dump(payload, tmp, ensure_ascii=True, indent=2)
+            tmp.write("\n")
+            temp_name = tmp.name
+        os.replace(temp_name, path)
 
     @staticmethod
-    def _window_to_dict(window: UsageWindow | None) -> dict[str, Any] | None:
-        return asdict(window) if window else None
+    def _account_to_dict(account: AccountRecord) -> dict[str, Any]:
+        return {
+            "email": account.email,
+            "access_token": account.access_token,
+            "refresh_token": account.refresh_token,
+            "token_refresh_at": account.token_refresh_at,
+            "usage": JsonStateStore._usage_to_dict(account.usage),
+            "usage_checked_at": account.usage_checked_at,
+            "disabled": account.disabled,
+        }
 
-    @classmethod
-    def _snapshot_to_dict(cls, snapshot: UsageSnapshot | None) -> dict[str, Any] | None:
+    @staticmethod
+    def _usage_to_dict(snapshot: UsageSnapshot | None) -> dict[str, Any] | None:
         if snapshot is None:
             return None
         return {
-            "checked_at": snapshot.checked_at,
-            "primary_window": cls._window_to_dict(snapshot.primary_window),
-            "secondary_window": cls._window_to_dict(snapshot.secondary_window),
-            "limit_reached": snapshot.limit_reached,
-            "allowed": snapshot.allowed,
+            "primary": JsonStateStore._window_to_dict(snapshot.primary_window),
+            "secondary": JsonStateStore._window_to_dict(snapshot.secondary_window),
         }
 
     @staticmethod
-    def _window_from_dict(window: dict[str, Any] | None) -> UsageWindow | None:
-        return parse_usage_window(window)
-
-    @classmethod
-    def _snapshot_from_dict(
-        cls, snapshot: dict[str, Any] | None
-    ) -> UsageSnapshot | None:
-        if not isinstance(snapshot, dict):
+    def _window_to_dict(window: UsageWindow | None) -> dict[str, Any] | None:
+        if window is None:
             return None
-        return build_usage_snapshot(
-            checked_at=int(snapshot.get("checked_at") or 0),
-            primary_window=cls._window_from_dict(snapshot.get("primary_window")),
-            secondary_window=cls._window_from_dict(snapshot.get("secondary_window")),
-            limit_reached=bool(snapshot.get("limit_reached")),
-            allowed=bool(snapshot.get("allowed", True)),
-        )
+        return {
+            "used_percent": window.used_percent,
+            "reset_at": window.reset_at,
+        }
 
-    @classmethod
-    def _account_from_dict(cls, payload: dict[str, Any]) -> AccountRecord:
+    @staticmethod
+    def _account_from_dict(payload: dict[str, Any]) -> AccountRecord:
+        usage_checked_at = payload.get("usage_checked_at")
+        usage = JsonStateStore._usage_from_dict(payload.get("usage"), usage_checked_at)
         return AccountRecord(
-            id=str(payload["id"]),
-            email=payload.get("email"),
-            account_id=payload.get("account_id"),
+            email=str(payload.get("email") or ""),
             access_token=str(payload.get("access_token") or ""),
             refresh_token=str(payload.get("refresh_token") or ""),
-            expires_at=int(payload.get("expires_at") or 0),
-            cooldown_until=int(payload["cooldown_until"])
-            if payload.get("cooldown_until")
-            else None,
-            last_known_usage=cls._snapshot_from_dict(payload.get("last_known_usage")),
-            last_error=payload.get("last_error"),
+            token_refresh_at=int(payload.get("token_refresh_at") or 0),
+            usage=usage,
+            usage_checked_at=int(usage_checked_at) if usage_checked_at else None,
+            disabled=bool(payload.get("disabled", False)),
         )
 
-    @classmethod
-    def _account_to_dict(cls, account: AccountRecord) -> dict[str, Any]:
-        return {
-            "id": account.id,
-            "email": account.email,
-            "account_id": account.account_id,
-            "access_token": account.access_token,
-            "refresh_token": account.refresh_token,
-            "expires_at": account.expires_at,
-            "cooldown_until": account.cooldown_until,
-            "last_known_usage": cls._snapshot_to_dict(account.last_known_usage),
-            "last_error": account.last_error,
-        }
+    @staticmethod
+    def _usage_from_dict(payload: dict[str, Any] | None, checked_at: Any) -> UsageSnapshot | None:
+        if not isinstance(payload, dict):
+            return None
+        return UsageSnapshot(
+            checked_at=int(checked_at or 0),
+            primary_window=JsonStateStore._window_from_dict(payload.get("primary")),
+            secondary_window=JsonStateStore._window_from_dict(payload.get("secondary")),
+        )
+
+    @staticmethod
+    def _window_from_dict(payload: dict[str, Any] | None) -> UsageWindow | None:
+        if not isinstance(payload, dict):
+            return None
+        reset_at = payload.get("reset_at")
+        return UsageWindow(
+            used_percent=int(payload.get("used_percent") or 0),
+            reset_at=int(reset_at) if reset_at else None,
+        )
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..c0d7d12
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,10 @@
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+SRC = ROOT / "src"
+
+if str(SRC) not in sys.path:
+    sys.path.insert(0, str(SRC))
diff --git a/tests/test_account_ops.py b/tests/test_account_ops.py
deleted file mode 100644
index b28f448..0000000
--- a/tests/test_account_ops.py
+++ /dev/null
@@ -1,233 +0,0 @@
-from __future__ import annotations
-
-import time
-from typing import Any, cast
-
-import pytest
-
-from gibby.account_ops import (
-    PermanentAccountFailure,
-    refresh_account_usage,
-    snapshot_is_exhausted,
-    window_used_percent,
-)
-from gibby.client import OpenAIAPIError
-from gibby.models import (
-    UNKNOWN_EXHAUSTED_BACKOFF_SECONDS,
-    AccountRecord,
-    UsageSnapshot,
-    UsageWindow,
-    compute_cooldown_until,
-)
-
-
-class FakeClient:
-    def __init__(self, usage: UsageSnapshot, *, permanent: bool = False):
-        self.usage = usage
-        self.permanent = permanent
-        self.refresh_calls: list[str] = []
-
-    async def refresh_access_token(self, refresh_token: str):
-        self.refresh_calls.append(refresh_token)
-        return ("new-token", "new-refresh", int(time.time()) + 600)
-
-    async def fetch_usage_payload(self, access_token: str) -> dict:
-        if self.permanent:
-            raise OpenAIAPIError("invalid_grant", permanent=True, status_code=401)
-        primary_window = self.usage.primary_window
-        assert primary_window is not None
-        secondary_window = (
-            {
-                "used_percent": self.usage.secondary_window.used_percent,
-                "limit_window_seconds": self.usage.secondary_window.limit_window_seconds,
-                "reset_after_seconds": self.usage.secondary_window.reset_after_seconds,
-                "reset_at": self.usage.secondary_window.reset_at,
-            }
-            if self.usage.secondary_window is not None
-            else None
-        )
-        return {
-            "email": "acc@example.com",
-            "account_id": "acc-1",
-            "rate_limit": {
-                "allowed": self.usage.allowed,
-                "limit_reached": self.usage.limit_reached,
-                "primary_window": {
-                    "used_percent": primary_window.used_percent,
-                    "limit_window_seconds": primary_window.limit_window_seconds,
-                    "reset_after_seconds": primary_window.reset_after_seconds,
-                    "reset_at": primary_window.reset_at,
-                },
-                "secondary_window": secondary_window,
-            },
-        }
-
-
-def make_usage(
-    primary: int,
-    secondary: int | None = None,
-    *,
-    limit_reached: bool = False,
-    allowed: bool | None = None,
-    reset_after: int = 10,
-    checked_at: int | None = None,
-    primary_reset_at: int | None = None,
-    secondary_reset_at: int | None = None,
-    primary_limit_window_seconds: int = 18000,
-    secondary_limit_window_seconds: int = 604800,
-) -> UsageSnapshot:
-    checked_at = checked_at or int(time.time())
-    exhausted = (
-        primary >= 100 or (secondary is not None and secondary >= 100) or limit_reached
-    )
-    if allowed is None:
-        allowed = not exhausted
-    return UsageSnapshot(
-        checked_at=checked_at,
-        used_percent=max(primary, secondary or 0),
-        remaining_percent=max(0, 100 - max(primary, secondary or 0)),
-        exhausted=exhausted or not allowed,
-        primary_window=UsageWindow(
-            primary,
-            primary_limit_window_seconds,
-            reset_after,
-            primary_reset_at
-            if primary_reset_at is not None
-            else checked_at + reset_after,
-        ),
-        secondary_window=UsageWindow(
-            secondary,
-            secondary_limit_window_seconds,
-            reset_after,
-            secondary_reset_at
-            if secondary_reset_at is not None
-            else checked_at + reset_after,
-        )
-        if secondary is not None
-        else None,
-        limit_reached=limit_reached,
-        allowed=allowed,
-    )
-
-
-def test_window_used_percent_defaults_to_zero() -> None:
-    assert window_used_percent(None) == 0
-
-
-def test_snapshot_is_exhausted_checks_various_conditions() -> None:
-    assert snapshot_is_exhausted(make_usage(94, 95), 96) is False
-    assert snapshot_is_exhausted(make_usage(94), 95) is False
-    assert snapshot_is_exhausted(make_usage(95), 95) is True
-    assert snapshot_is_exhausted(make_usage(50, 95), 95) is True
-    assert snapshot_is_exhausted(make_usage(50, limit_reached=True), 95) is True
-
-
-def test_compute_cooldown_until_uses_primary_blocking_window() -> None:
-    usage = make_usage(
-        95, 20, checked_at=1000, primary_reset_at=1100, secondary_reset_at=1300
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1100
-
-
-def test_compute_cooldown_until_uses_secondary_blocking_window() -> None:
-    usage = make_usage(
-        20, 95, checked_at=1000, primary_reset_at=1100, secondary_reset_at=1300
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1300
-
-
-def test_compute_cooldown_until_waits_for_all_blocking_windows() -> None:
-    usage = make_usage(
-        95, 95, checked_at=1000, primary_reset_at=1100, secondary_reset_at=1300
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1300
-
-
-def test_compute_cooldown_until_uses_latest_window_when_blocker_is_ambiguous() -> None:
-    usage = make_usage(
-        80,
-        40,
-        limit_reached=True,
-        allowed=False,
-        checked_at=1000,
-        primary_reset_at=1100,
-        secondary_reset_at=1300,
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1300
-
-
-def test_compute_cooldown_until_falls_back_to_limit_window_seconds() -> None:
-    usage = make_usage(
-        95,
-        checked_at=1000,
-        reset_after=0,
-        primary_reset_at=0,
-        primary_limit_window_seconds=600,
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1600
-
-
-def test_compute_cooldown_until_uses_backoff_when_no_reset_metadata_exists() -> None:
-    usage = make_usage(
-        95,
-        checked_at=1000,
-        reset_after=0,
-        primary_reset_at=0,
-        primary_limit_window_seconds=0,
-    )
-
-    assert compute_cooldown_until(usage, 95) == 1000 + UNKNOWN_EXHAUSTED_BACKOFF_SECONDS
-
-
-@pytest.mark.asyncio
-async def test_refresh_account_usage_populates_snapshot_and_cooldown() -> None:
-    current = int(time.time())
-    account = AccountRecord(
-        id="a1",
-        access_token="tok",
-        refresh_token="ref",
-        expires_at=int(time.time()) + 600,
-    )
-    usage = make_usage(
-        96,
-        1,
-        limit_reached=True,
-        allowed=False,
-        checked_at=current,
-        primary_reset_at=current + 100,
-        secondary_reset_at=current + 300,
-    )
-    client = FakeClient(usage)
-
-    result = await refresh_account_usage(account, cast(Any, client), 95)
-
-    assert result.used_percent == usage.used_percent
-    assert result.limit_reached is usage.limit_reached
-    assert result.allowed is usage.allowed
-    assert account.last_known_usage is not None
-    assert account.last_known_usage.used_percent == usage.used_percent
-    assert account.cooldown_until == current + 100
-    assert account.email == "acc@example.com"
-    assert account.id == "acc@example.com"
-
-
-@pytest.mark.asyncio
-async def test_refresh_account_usage_raises_permanent_failure() -> None:
-    account = AccountRecord(
-        id="a1",
-        access_token="tok",
-        refresh_token="ref",
-        expires_at=int(time.time()) + 600,
-    )
-
-    with pytest.raises(PermanentAccountFailure):
-        await refresh_account_usage(
-            account,
-            cast(Any, FakeClient(make_usage(1), permanent=True)),
-            95,
-        )
diff --git a/tests/test_app.py b/tests/test_app.py
index 50c47da..64abea9 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -11,11 +11,9 @@ class StubManager(AccountManager):
     def __init__(
         self,
         response: dict[str, Any] | None = None,
-        usage_response: dict[str, Any] | None = None,
         error: Exception | None = None,
     ):
         self.response = response
-        self.usage_response = usage_response
         self.error = error
 
     async def issue_token_response(self):
@@ -25,12 +23,6 @@ class StubManager(AccountManager):
             return self.response
         return {}
 
-    async def get_usage_report(self):
-        if self.usage_response is not None:
-            return self.usage_response
-        return {"accounts": [], "active_account_id": None, "count": 0}
-
-
 def test_health_ok() -> None:
     client = TestClient(create_app(StubManager(response={})))
     response = client.get("/health")
@@ -64,26 +56,3 @@ def test_token_error_shape() -> None:
     response = client.get("/token")
     assert response.status_code == 503
     assert response.json() == {"error": "No usable account available"}
-
-
-def test_usage_success_shape() -> None:
-    payload = {
-        "accounts": [
-            {
-                "id": "a1",
-                "email": "a1@example.com",
-                "status": "ok",
-                "used_percent": 12,
-                "remaining_percent": 88,
-                "cooldown_until": None,
-                "primary_window": {"used_percent": 12},
-                "secondary_window": {"used_percent": 1},
-            }
-        ],
-        "active_account_id": "a1",
-        "count": 1,
-    }
-    client = TestClient(create_app(StubManager(usage_response=payload)))
-    response = client.get("/usage")
-    assert response.status_code == 200
-    assert response.json() == payload
diff --git a/tests/test_core.py b/tests/test_core.py
index a673bda..f156681 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import json
 import time
 from pathlib import Path
 
@@ -17,15 +18,17 @@ class FakeClient(OpenAIClient):
         self,
         usage_by_token=None,
         refresh_map=None,
-        failing_tokens=None,
+        invalid_tokens=None,
         permanent_refresh_tokens=None,
     ):
         self.usage_by_token = usage_by_token or {}
         self.refresh_map = refresh_map or {}
-        self.failing_tokens = set(failing_tokens or [])
+        self.invalid_tokens = set(invalid_tokens or [])
         self.permanent_refresh_tokens = set(permanent_refresh_tokens or [])
-        self.fetched_tokens: list[str] = []
+        self.fetched_usage_tokens: list[str] = []
+        self.validated_tokens: list[str] = []
         self.refresh_calls: list[str] = []
+        self.settings = Settings(data_dir=Path("."))
 
     async def refresh_access_token(self, refresh_token: str):
         self.refresh_calls.append(refresh_token)
@@ -34,28 +37,21 @@ class FakeClient(OpenAIClient):
         return self.refresh_map[refresh_token]
 
     async def fetch_usage_payload(self, access_token: str):
-        self.fetched_tokens.append(access_token)
-        if access_token in self.failing_tokens:
-            raise RuntimeError("usage failed")
+        self.fetched_usage_tokens.append(access_token)
         usage = self.usage_by_token[access_token]
         return {
             "email": f"{access_token}@example.com",
-            "account_id": f"acct-{access_token}",
             "rate_limit": {
                 "allowed": usage.allowed,
                 "limit_reached": usage.limit_reached,
                 "primary_window": {
                     "used_percent": usage.primary_window.used_percent,
-                    "limit_window_seconds": usage.primary_window.limit_window_seconds,
-                    "reset_after_seconds": usage.primary_window.reset_after_seconds,
                     "reset_at": usage.primary_window.reset_at,
                 }
                 if usage.primary_window
                 else None,
                 "secondary_window": {
                     "used_percent": usage.secondary_window.used_percent,
-                    "limit_window_seconds": usage.secondary_window.limit_window_seconds,
-                    "reset_after_seconds": usage.secondary_window.reset_after_seconds,
                     "reset_at": usage.secondary_window.reset_at,
                 }
                 if usage.secondary_window
@@ -63,53 +59,38 @@ class FakeClient(OpenAIClient):
             },
         }
 
+    async def validate_token(self, access_token: str) -> bool:
+        self.validated_tokens.append(access_token)
+        return access_token not in self.invalid_tokens
 
-def make_usage(
-    *,
-    used: int,
-    secondary_used: int | None = None,
-    limit_reached: bool = False,
-    reset_after: int = 0,
-) -> UsageSnapshot:
-    exhausted = (
-        used >= 100
-        or (secondary_used is not None and secondary_used >= 100)
-        or limit_reached
-    )
+
+def make_usage(primary: int, secondary: int = 0, *, checked_at: int | None = None):
     return UsageSnapshot(
-        checked_at=int(time.time()),
-        used_percent=used,
-        remaining_percent=max(0, 100 - used),
-        exhausted=exhausted,
-        primary_window=UsageWindow(
-            used_percent=used,
-            limit_window_seconds=604800,
-            reset_after_seconds=reset_after,
-            reset_at=int(time.time()) + reset_after if reset_after else 0,
-        ),
+        checked_at=checked_at or int(time.time()),
+        primary_window=UsageWindow(used_percent=primary, reset_at=int(time.time()) + 300),
         secondary_window=UsageWindow(
-            used_percent=secondary_used,
-            limit_window_seconds=604800,
-            reset_after_seconds=reset_after,
-            reset_at=int(time.time()) + reset_after if reset_after else 0,
-        )
-        if secondary_used is not None
-        else None,
-        limit_reached=limit_reached,
-        allowed=not exhausted,
+            used_percent=secondary, reset_at=int(time.time()) + 300
+        ),
     )
 
 
-def make_manager(
-    store: JsonStateStore,
-    client: FakeClient,
+def make_account(
+    email: str,
     *,
-    threshold: int = 95,
-) -> AccountManager:
-    return AccountManager(
-        store,
-        client,
-        Settings(data_dir=store.path.parent, exhausted_usage_threshold=threshold),
+    token: str,
+    refresh_token: str = "refresh",
+    token_refresh_at: int | None = None,
+    usage: UsageSnapshot | None = None,
+    disabled: bool = False,
+) -> AccountRecord:
+    return AccountRecord(
+        email=email,
+        access_token=token,
+        refresh_token=refresh_token,
+        token_refresh_at=token_refresh_at or int(time.time()) + 600,
+        usage=usage,
+        usage_checked_at=usage.checked_at if usage is not None else None,
+        disabled=disabled,
     )
 
 
@@ -119,452 +100,167 @@ def make_store(tmp_path: Path, state: StateFile) -> JsonStateStore:
     return store
 
 
-@pytest.mark.asyncio
-async def test_prefers_active_account_when_locally_usable(tmp_path: Path) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(
-        tmp_path, StateFile(active_account_id="a1", accounts=[active, second])
-    )
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=21),
-            "tok-a2": make_usage(used=72),
-        }
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a1"
-    assert client.fetched_tokens == ["tok-a1"]
-    assert store.load().active_account_id == "tok-a1@example.com"
-
-
-@pytest.mark.asyncio
-async def test_prefers_higher_primary_usage_from_saved_snapshot(tmp_path: Path) -> None:
-    first = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[first, second]))
-    client = FakeClient(usage_by_token={"tok-a2": make_usage(used=72)})
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a2"]
-    saved = store.load()
-    assert saved.active_account_id == "tok-a2@example.com"
-
-
-@pytest.mark.asyncio
-async def test_breaks_ties_with_secondary_usage(tmp_path: Path) -> None:
-    first = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=60, secondary_used=10),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=60, secondary_used=40),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[first, second]))
-    client = FakeClient(
-        usage_by_token={"tok-a2": make_usage(used=61, secondary_used=41)}
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a2"]
-
-
-@pytest.mark.asyncio
-async def test_treats_missing_secondary_as_zero(tmp_path: Path) -> None:
-    first = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=60),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=60, secondary_used=1),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[first, second]))
-    client = FakeClient(
-        usage_by_token={"tok-a2": make_usage(used=61, secondary_used=1)}
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a2"]
-
-
-@pytest.mark.asyncio
-async def test_skips_account_still_in_cooldown(tmp_path: Path) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        cooldown_until=int(time.time()) + 300,
-        last_known_usage=make_usage(used=80),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20),
-    )
-    store = make_store(
-        tmp_path, StateFile(active_account_id="a1", accounts=[active, second])
-    )
-    client = FakeClient(usage_by_token={"tok-a2": make_usage(used=25)})
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a2"]
-    assert store.load().active_account_id == "tok-a2@example.com"
-
-
-@pytest.mark.asyncio
-async def test_skips_active_account_blocked_by_local_exhausted_snapshot(
-    tmp_path: Path,
-) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=96),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20),
-    )
-    store = make_store(
-        tmp_path, StateFile(active_account_id="a1", accounts=[active, second])
-    )
-    client = FakeClient(usage_by_token={"tok-a2": make_usage(used=25)})
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a2"]
-    assert store.load().active_account_id == "tok-a2@example.com"
-
-
-@pytest.mark.asyncio
-async def test_live_checks_depleted_and_moves_to_next(tmp_path: Path) -> None:
-    high = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=94),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=50),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[high, second]))
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=96, reset_after=120),
-            "tok-a2": make_usage(used=52),
-        }
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a1", "tok-a2"]
-
-
-@pytest.mark.asyncio
-async def test_live_checks_secondary_depleted_and_moves_to_next(tmp_path: Path) -> None:
-    high = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=30, secondary_used=94),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20, secondary_used=10),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[high, second]))
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=30, secondary_used=100, reset_after=120),
-            "tok-a2": make_usage(used=22, secondary_used=10),
-        }
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a1", "tok-a2"]
-
-
-@pytest.mark.asyncio
-async def test_falls_through_when_live_usage_is_depleted(tmp_path: Path) -> None:
-    first = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=80),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[first, second]))
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=95, reset_after=120),
-            "tok-a2": make_usage(used=71),
-        }
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-    saved = store.load()
-
-    assert payload["token"] == "tok-a2"
-    assert client.fetched_tokens == ["tok-a1", "tok-a2"]
-    depleted = next(
-        account for account in saved.accounts if account.id == "tok-a1@example.com"
-    )
-    assert depleted.cooldown_until is not None
-    assert depleted.last_known_usage is not None
-    assert depleted.last_known_usage.used_percent == 95
-
-
-@pytest.mark.asyncio
-async def test_keeps_account_out_until_blocking_window_resets(tmp_path: Path) -> None:
-    current = int(time.time())
-    blocked = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=80, secondary_used=40),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[blocked, second]))
-    blocked_usage = UsageSnapshot(
-        checked_at=current,
-        used_percent=80,
-        remaining_percent=20,
-        exhausted=True,
-        primary_window=UsageWindow(
-            used_percent=80,
-            limit_window_seconds=604800,
-            reset_after_seconds=60,
-            reset_at=current + 60,
+def make_manager(
+    store: JsonStateStore,
+    client: FakeClient,
+    *,
+    threshold: int = 95,
+    stale_seconds: int = 3600,
+) -> AccountManager:
+    return AccountManager(
+        store,
+        client,
+        Settings(
+            data_dir=store.path.parent,
+            exhausted_usage_threshold=threshold,
+            usage_stale_seconds=stale_seconds,
         ),
-        secondary_window=UsageWindow(
-            used_percent=40,
-            limit_window_seconds=604800,
-            reset_after_seconds=240,
-            reset_at=current + 240,
-        ),
-        limit_reached=True,
-        allowed=False,
     )
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": blocked_usage,
-            "tok-a2": make_usage(used=71),
-        }
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-    saved = store.load()
-    blocked_saved = next(
-        account for account in saved.accounts if account.id == "tok-a1@example.com"
-    )
-
-    assert payload["token"] == "tok-a2"
-    assert blocked_saved.cooldown_until == current + 240
-    assert client.fetched_tokens == ["tok-a1", "tok-a2"]
 
 
 @pytest.mark.asyncio
-async def test_refreshes_expired_token_before_usage(tmp_path: Path) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="old-token",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) - 1,
-        last_known_usage=make_usage(used=20),
+async def test_prefers_active_account_when_usable(tmp_path: Path) -> None:
+    active = make_account("a@example.com", token="tok-a", usage=make_usage(20, 0))
+    second = make_account("b@example.com", token="tok-b", usage=make_usage(80, 0))
+    store = make_store(
+        tmp_path,
+        StateFile(active_account="a@example.com", accounts=[active, second]),
     )
-    store = make_store(tmp_path, StateFile(active_account_id="a1", accounts=[active]))
-    client = FakeClient(
-        usage_by_token={"new-token": make_usage(used=20)},
-        refresh_map={"ref-a1": ("new-token", "new-refresh", int(time.time()) + 600)},
+    client = FakeClient()
+
+    payload = await make_manager(store, client).issue_token_response()
+
+    assert payload["token"] == "tok-a"
+    assert client.fetched_usage_tokens == []
+    assert client.validated_tokens == ["tok-a"]
+
+
+@pytest.mark.asyncio
+async def test_refreshes_stale_active_usage_before_deciding(tmp_path: Path) -> None:
+    stale = int(time.time()) - 7200
+    active = make_account("a@example.com", token="tok-a", usage=make_usage(20, 0, checked_at=stale))
+    second = make_account("b@example.com", token="tok-b", usage=make_usage(80, 0))
+    store = make_store(
+        tmp_path,
+        StateFile(active_account="a@example.com", accounts=[active, second]),
     )
+    client = FakeClient(usage_by_token={"tok-a": make_usage(21, 0)})
+
+    payload = await make_manager(store, client).issue_token_response()
+
+    assert payload["token"] == "tok-a"
+    assert client.fetched_usage_tokens == ["tok-a"]
+
+
+@pytest.mark.asyncio
+async def test_falls_back_to_highest_primary_usage_when_active_unusable(tmp_path: Path) -> None:
+    active = make_account("a@example.com", token="tok-a", usage=make_usage(95, 0))
+    low = make_account("b@example.com", token="tok-b", usage=make_usage(40, 0))
+    high = make_account("c@example.com", token="tok-c", usage=make_usage(70, 0))
+    store = make_store(
+        tmp_path,
+        StateFile(active_account="a@example.com", accounts=[active, low, high]),
+    )
+    client = FakeClient()
+
+    payload = await make_manager(store, client).issue_token_response()
+    state = store.load()
+
+    assert payload["token"] == "tok-c"
+    assert state.active_account == "c@example.com"
+
+
+@pytest.mark.asyncio
+async def test_skips_disabled_accounts(tmp_path: Path) -> None:
+    active = make_account("a@example.com", token="tok-a", usage=make_usage(20, 0), disabled=True)
+    second = make_account("b@example.com", token="tok-b", usage=make_usage(70, 0))
+    store = make_store(
+        tmp_path,
+        StateFile(active_account="a@example.com", accounts=[active, second]),
+    )
+    client = FakeClient()
+
+    payload = await make_manager(store, client).issue_token_response()
+
+    assert payload["token"] == "tok-b"
+
+
+@pytest.mark.asyncio
+async def test_secondary_100_makes_account_unusable(tmp_path: Path) -> None:
+    active = make_account("a@example.com", token="tok-a", usage=make_usage(20, 100))
+    second = make_account("b@example.com", token="tok-b", usage=make_usage(30, 0))
+    store = make_store(
+        tmp_path,
+        StateFile(active_account="a@example.com", accounts=[active, second]),
+    )
+    client = FakeClient()
+
+    payload = await make_manager(store, client).issue_token_response()
+
+    assert payload["token"] == "tok-b"
+
+
+@pytest.mark.asyncio
+async def test_refreshes_token_before_validation(tmp_path: Path) -> None:
+    account = make_account(
+        "a@example.com",
+        token="old-token",
+        refresh_token="ref-a",
+        token_refresh_at=int(time.time()) - 1,
+        usage=make_usage(20, 0),
+    )
+    store = make_store(tmp_path, StateFile(active_account="a@example.com", accounts=[account]))
+    client = FakeClient(refresh_map={"ref-a": ("new-token", "new-refresh", int(time.time()) + 600)})
 
     payload = await make_manager(store, client).issue_token_response()
     saved = store.load()
 
     assert payload["token"] == "new-token"
-    assert client.refresh_calls == ["ref-a1"]
-    assert client.fetched_tokens == ["new-token"]
-    assert saved.accounts[0].id == "new-token@example.com"
+    assert client.refresh_calls == ["ref-a"]
+    assert client.validated_tokens == ["new-token"]
     assert saved.accounts[0].access_token == "new-token"
     assert saved.accounts[0].refresh_token == "new-refresh"
 
 
 @pytest.mark.asyncio
-async def test_raises_when_all_accounts_unusable(tmp_path: Path) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=80),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(
-        tmp_path, StateFile(active_account_id="a1", accounts=[active, second])
-    )
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=96, reset_after=120),
-            "tok-a2": make_usage(used=97, reset_after=120),
-        }
-    )
+async def test_invalid_token_moves_account_to_failed_json(tmp_path: Path) -> None:
+    bad = make_account("bad@example.com", token="tok-bad", usage=make_usage(20, 0))
+    good = make_account("good@example.com", token="tok-good", usage=make_usage(30, 0))
+    store = make_store(tmp_path, StateFile(active_account="bad@example.com", accounts=[bad, good]))
+    client = FakeClient(invalid_tokens={"tok-bad"})
+
+    payload = await make_manager(store, client).issue_token_response()
+    state = store.load()
+    failed = json.loads((tmp_path / "failed.json").read_text())
+
+    assert payload["token"] == "tok-good"
+    assert [account.email for account in state.accounts] == ["good@example.com"]
+    assert failed["accounts"][0]["email"] == "bad@example.com"
+
+
+@pytest.mark.asyncio
+async def test_rereads_disk_between_requests(tmp_path: Path) -> None:
+    first = make_account("a@example.com", token="tok-a", usage=make_usage(20, 0))
+    store = make_store(tmp_path, StateFile(active_account="a@example.com", accounts=[first]))
+    client = FakeClient()
+    manager = make_manager(store, client)
+
+    first_payload = await manager.issue_token_response()
+    assert first_payload["token"] == "tok-a"
+
+    replacement = make_account("b@example.com", token="tok-b", usage=make_usage(10, 0))
+    store.save(StateFile(active_account="b@example.com", accounts=[replacement]))
+
+    second_payload = await manager.issue_token_response()
+    assert second_payload["token"] == "tok-b"
+
+
+@pytest.mark.asyncio
+async def test_raises_when_no_usable_accounts(tmp_path: Path) -> None:
+    disabled = make_account("a@example.com", token="tok-a", usage=make_usage(10, 0), disabled=True)
+    exhausted = make_account("b@example.com", token="tok-b", usage=make_usage(95, 0))
+    store = make_store(tmp_path, StateFile(accounts=[disabled, exhausted]))
+    client = FakeClient()
 
     with pytest.raises(NoUsableAccountError):
         await make_manager(store, client).issue_token_response()
-
-    saved = store.load()
-    assert all(account.cooldown_until is not None for account in saved.accounts)
-
-
-@pytest.mark.asyncio
-async def test_threshold_can_be_overridden_for_selection(tmp_path: Path) -> None:
-    active = AccountRecord(
-        id="a1",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=96),
-    )
-    second = AccountRecord(
-        id="a2",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=20),
-    )
-    store = make_store(
-        tmp_path, StateFile(active_account_id="a1", accounts=[active, second])
-    )
-    client = FakeClient(
-        usage_by_token={
-            "tok-a1": make_usage(used=96),
-            "tok-a2": make_usage(used=25),
-        }
-    )
-
-    payload = await make_manager(store, client, threshold=97).issue_token_response()
-
-    assert payload["token"] == "tok-a1"
-    assert client.fetched_tokens == ["tok-a1"]
-
-
-@pytest.mark.asyncio
-async def test_removes_account_and_records_failed_email_on_permanent_refresh_failure(
-    tmp_path: Path,
-) -> None:
-    dead = AccountRecord(
-        id="a1",
-        email="dead@example.com",
-        access_token="tok-a1",
-        refresh_token="ref-a1",
-        expires_at=int(time.time()) - 1,
-        last_known_usage=make_usage(used=80),
-    )
-    alive = AccountRecord(
-        id="a2",
-        email="alive@example.com",
-        access_token="tok-a2",
-        refresh_token="ref-a2",
-        expires_at=int(time.time()) + 600,
-        last_known_usage=make_usage(used=70),
-    )
-    store = make_store(tmp_path, StateFile(accounts=[dead, alive]))
-    client = FakeClient(
-        usage_by_token={"tok-a2": make_usage(used=71)},
-        permanent_refresh_tokens={"ref-a1"},
-    )
-
-    payload = await make_manager(store, client).issue_token_response()
-
-    assert payload["token"] == "tok-a2"
-    saved = store.load()
-    assert [account.id for account in saved.accounts] == ["tok-a2@example.com"]
-    assert (tmp_path / "failed.txt").read_text().splitlines() == ["dead@example.com"]
diff --git a/tests/test_oauth_helper.py b/tests/test_oauth_helper.py
index 68c04d1..bd0172a 100644
--- a/tests/test_oauth_helper.py
+++ b/tests/test_oauth_helper.py
@@ -49,8 +49,6 @@ class FakeClient:
         secondary_window = (
             {
                 "used_percent": self.usage.secondary_window.used_percent,
-                "limit_window_seconds": self.usage.secondary_window.limit_window_seconds,
-                "reset_after_seconds": self.usage.secondary_window.reset_after_seconds,
                 "reset_at": self.usage.secondary_window.reset_at,
             }
             if self.usage.secondary_window is not None
@@ -64,8 +62,6 @@ class FakeClient:
                 "limit_reached": self.usage.limit_reached,
                 "primary_window": {
                     "used_percent": primary_window.used_percent,
-                    "limit_window_seconds": primary_window.limit_window_seconds,
-                    "reset_after_seconds": primary_window.reset_after_seconds,
                     "reset_at": primary_window.reset_at,
                 },
                 "secondary_window": secondary_window,
@@ -76,15 +72,10 @@ class FakeClient:
 def make_usage(primary: int, secondary: int | None = None) -> UsageSnapshot:
     return UsageSnapshot(
         checked_at=1775000000,
-        used_percent=max(primary, secondary or 0),
-        remaining_percent=max(0, 100 - max(primary, secondary or 0)),
-        exhausted=False,
-        primary_window=UsageWindow(primary, 18000, 100, 1775000100),
-        secondary_window=UsageWindow(secondary, 604800, 100, 1775000100)
+        primary_window=UsageWindow(primary, 1775000100),
+        secondary_window=UsageWindow(secondary or 0, 1775000100)
         if secondary is not None
         else None,
-        limit_reached=False,
-        allowed=True,
     )
 
 
@@ -147,31 +138,29 @@ async def test_exchange_and_store_account_populates_usage_snapshot(
         False,
     )
 
-    assert account.last_known_usage is not None
-    assert account.id == "oauth@example.com"
-    assert account.last_known_usage.primary_window is not None
-    assert account.last_known_usage.primary_window.used_percent == 12
-    assert account.last_known_usage.secondary_window is not None
-    assert account.last_known_usage.secondary_window.used_percent == 3
+    assert account.usage is not None
+    assert account.email == "oauth@example.com"
+    assert account.usage.primary_window is not None
+    assert account.usage.primary_window.used_percent == 12
+    assert account.usage.secondary_window is not None
+    assert account.usage.secondary_window.used_percent == 3
 
 
 @pytest.mark.asyncio
-async def test_exchange_and_store_account_keeps_tokens_on_transient_usage_failure(
+async def test_exchange_and_store_account_raises_on_transient_usage_failure(
     tmp_path: Path,
 ) -> None:
     store = JsonStateStore(tmp_path / "accounts.json")
     settings = Settings(data_dir=tmp_path)
     client = FakeClient(settings, make_usage(12, 3), transient_usage_failure=True)
 
-    account = await exchange_and_store_account(
-        store,
-        cast(Any, client),
-        "code",
-        "verifier",
-        False,
-    )
+    with pytest.raises(OpenAIAPIError):
+        await exchange_and_store_account(
+            store,
+            cast(Any, client),
+            "code",
+            "verifier",
+            False,
+        )
 
-    saved = store.load()
-    assert account.last_known_usage is None
-    assert saved.accounts[0].access_token == "access-token"
-    assert saved.accounts[0].last_error is not None
+    assert store.load().accounts == []
diff --git a/tests/test_refresh_limits.py b/tests/test_refresh_limits.py
index f80acdd..bbb998c 100644
--- a/tests/test_refresh_limits.py
+++ b/tests/test_refresh_limits.py
@@ -17,15 +17,10 @@ import refresh_limits  # type: ignore[import-not-found]
 def make_usage(primary: int, secondary: int | None = None) -> UsageSnapshot:
     return UsageSnapshot(
         checked_at=int(time.time()),
-        used_percent=max(primary, secondary or 0),
-        remaining_percent=max(0, 100 - max(primary, secondary or 0)),
-        exhausted=False,
-        primary_window=UsageWindow(primary, 18000, 10, int(time.time()) + 10),
-        secondary_window=UsageWindow(secondary, 604800, 10, int(time.time()) + 10)
+        primary_window=UsageWindow(primary, int(time.time()) + 10),
+        secondary_window=UsageWindow(secondary or 0, int(time.time()) + 10)
         if secondary is not None
         else None,
-        limit_reached=False,
-        allowed=True,
     )
 
 
@@ -49,8 +44,6 @@ class FakeClient:
         secondary_window = (
             {
                 "used_percent": usage.secondary_window.used_percent,
-                "limit_window_seconds": usage.secondary_window.limit_window_seconds,
-                "reset_after_seconds": usage.secondary_window.reset_after_seconds,
                 "reset_at": usage.secondary_window.reset_at,
             }
             if usage.secondary_window is not None
@@ -64,8 +57,6 @@ class FakeClient:
                 "limit_reached": usage.limit_reached,
                 "primary_window": {
                     "used_percent": primary_window.used_percent,
-                    "limit_window_seconds": primary_window.limit_window_seconds,
-                    "reset_after_seconds": primary_window.reset_after_seconds,
                     "reset_at": primary_window.reset_at,
                 },
                 "secondary_window": secondary_window,
@@ -82,11 +73,10 @@ async def test_refresh_limits_updates_all_accounts(
         StateFile(
             accounts=[
                 AccountRecord(
-                    id="acc@example.com",
                     email="acc@example.com",
                     access_token="tok-a1",
                     refresh_token="ref-a1",
-                    expires_at=int(time.time()) + 600,
+                    token_refresh_at=int(time.time()) + 600,
                 )
             ]
         )
@@ -96,9 +86,9 @@ async def test_refresh_limits_updates_all_accounts(
     await refresh_limits.run(tmp_path)
 
     state = store.load()
-    assert state.accounts[0].last_known_usage is not None
-    assert state.accounts[0].last_known_usage.primary_window is not None
-    assert state.accounts[0].last_known_usage.primary_window.used_percent == 12
+    assert state.accounts[0].usage is not None
+    assert state.accounts[0].usage.primary_window is not None
+    assert state.accounts[0].usage.primary_window.used_percent == 12
 
 
 @pytest.mark.asyncio
@@ -110,11 +100,10 @@ async def test_refresh_limits_removes_permanently_failed_account(
         StateFile(
             accounts=[
                 AccountRecord(
-                    id="dead@example.com",
                     email="dead@example.com",
                     access_token="tok-a1",
                     refresh_token="ref-a1",
-                    expires_at=int(time.time()) + 600,
+                    token_refresh_at=int(time.time()) + 600,
                 )
             ]
         )
@@ -129,4 +118,5 @@ async def test_refresh_limits_removes_permanently_failed_account(
 
     state = store.load()
     assert state.accounts == []
-    assert (tmp_path / "failed.txt").read_text().splitlines() == ["dead@example.com"]
+    failed = JsonStateStore(tmp_path / "accounts.json").load_failed_accounts()
+    assert [account.email for account in failed] == ["dead@example.com"]
diff --git a/tests/test_store.py b/tests/test_store.py
index 6a36825..55692f9 100644
--- a/tests/test_store.py
+++ b/tests/test_store.py
@@ -6,79 +6,68 @@ from gibby.models import AccountRecord, StateFile, UsageSnapshot, UsageWindow
 from gibby.store import JsonStateStore
 
 
-def test_store_writes_canonical_usage_snapshot_shape(tmp_path) -> None:
+def test_store_writes_minimal_accounts_schema(tmp_path) -> None:
     store = JsonStateStore(tmp_path / "accounts.json")
-    snapshot = UsageSnapshot(
-        checked_at=1000,
-        used_percent=75,
-        remaining_percent=25,
-        exhausted=False,
-        primary_window=UsageWindow(75, 18000, 300, 1300),
-        secondary_window=UsageWindow(10, 604800, 3600, 4600),
-        limit_reached=False,
-        allowed=True,
-    )
     store.save(
         StateFile(
+            active_account="acc@example.com",
             accounts=[
                 AccountRecord(
-                    id="acc@example.com",
                     email="acc@example.com",
                     access_token="tok",
                     refresh_token="ref",
-                    expires_at=2000,
-                    last_known_usage=snapshot,
+                    token_refresh_at=2000,
+                    usage=UsageSnapshot(
+                        checked_at=1000,
+                        primary_window=UsageWindow(used_percent=70, reset_at=1300),
+                        secondary_window=UsageWindow(used_percent=20, reset_at=4600),
+                    ),
+                    usage_checked_at=1000,
+                    disabled=False,
                 )
-            ]
+            ],
         )
     )
 
     payload = json.loads((tmp_path / "accounts.json").read_text())
-    saved_snapshot = payload["accounts"][0]["last_known_usage"]
 
-    assert set(saved_snapshot) == {
-        "checked_at",
-        "primary_window",
-        "secondary_window",
-        "limit_reached",
-        "allowed",
+    assert payload == {
+        "active_account": "acc@example.com",
+        "accounts": [
+            {
+                "email": "acc@example.com",
+                "access_token": "tok",
+                "refresh_token": "ref",
+                "token_refresh_at": 2000,
+                "usage": {
+                    "primary": {"used_percent": 70, "reset_at": 1300},
+                    "secondary": {"used_percent": 20, "reset_at": 4600},
+                },
+                "usage_checked_at": 1000,
+                "disabled": False,
+            }
+        ],
     }
 
 
-def test_store_load_reconstructs_derived_usage_fields(tmp_path) -> None:
+def test_store_load_reconstructs_account_state(tmp_path) -> None:
     path = tmp_path / "accounts.json"
     path.write_text(
         json.dumps(
             {
-                "version": 1,
-                "active_account_id": "acc@example.com",
+                "active_account": "acc@example.com",
                 "accounts": [
                     {
-                        "id": "acc@example.com",
                         "email": "acc@example.com",
-                        "account_id": "acc-1",
                         "access_token": "tok",
                         "refresh_token": "ref",
-                        "expires_at": 2000,
-                        "cooldown_until": None,
-                        "last_known_usage": {
-                            "checked_at": 1000,
-                            "primary_window": {
-                                "used_percent": 80,
-                                "limit_window_seconds": 18000,
-                                "reset_after_seconds": 300,
-                                "reset_at": 1300,
-                            },
-                            "secondary_window": {
-                                "used_percent": 100,
-                                "limit_window_seconds": 604800,
-                                "reset_after_seconds": 3600,
-                                "reset_at": 4600,
-                            },
-                            "limit_reached": False,
-                            "allowed": True,
+                        "token_refresh_at": 2000,
+                        "usage": {
+                            "primary": {"used_percent": 80, "reset_at": 1300},
+                            "secondary": {"used_percent": 15, "reset_at": 4600},
                         },
-                        "last_error": None,
+                        "usage_checked_at": 1000,
+                        "disabled": True,
                     }
                 ],
             }
@@ -86,11 +75,40 @@ def test_store_load_reconstructs_derived_usage_fields(tmp_path) -> None:
     )
 
     state = JsonStateStore(path).load()
-    snapshot = state.accounts[0].last_known_usage
 
-    assert snapshot is not None
-    assert snapshot.used_percent == 100
-    assert snapshot.remaining_percent == 0
-    assert snapshot.exhausted is True
-    assert snapshot.limit_reached is False
-    assert snapshot.allowed is True
+    assert state.active_account == "acc@example.com"
+    assert state.accounts[0].email == "acc@example.com"
+    assert state.accounts[0].token_refresh_at == 2000
+    assert state.accounts[0].usage is not None
+    assert state.accounts[0].usage.primary_window is not None
+    assert state.accounts[0].usage.primary_window.used_percent == 80
+    assert state.accounts[0].disabled is True
+
+
+def test_append_failed_account_writes_failed_json_shape(tmp_path) -> None:
+    store = JsonStateStore(tmp_path / "accounts.json")
+    store.append_failed_account(
+            AccountRecord(
+                email="failed@example.com",
+                access_token="tok",
+                refresh_token="ref",
+                token_refresh_at=2000,
+                disabled=False,
+            )
+        )
+
+    payload = json.loads((tmp_path / "failed.json").read_text())
+
+    assert payload == {
+        "accounts": [
+            {
+                "email": "failed@example.com",
+                "access_token": "tok",
+                "refresh_token": "ref",
+                "token_refresh_at": 2000,
+                "usage": None,
+                "usage_checked_at": None,
+                "disabled": False,
+            }
+        ]
+    }