fix(oauth): Split an oversized keyring token blob across entries

internal/cli/auth.go

@@ -74,6 +74,8 @@ func runAuth(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) in
 		return runAuthStatus(args[1:], stdout, stderr, deps)
 	case "refresh":
 		return runAuthRefresh(args[1:], stdout, stderr, deps)
+	case "reset":
+		return runAuthReset(args[1:], stdout, stderr, deps)
 	case "openrouter":
 		return runAuthOpenRouter(args[1:], stdout, stderr, deps)
 	case "chatgpt":
@@ -321,6 +323,7 @@ func validateAuthFlags(sub string, a authArgs) error {
 		"logout":  {"json": true},
 		"status":  {"json": true},
 		"refresh": {"watch": true},
+		"reset":   {"json": true},
 	}[sub]
 	bad := func(name string) error { return fmt.Errorf("zero auth %s does not accept %s", sub, name) }
 	if a.json && !allowed["json"] {
@@ -569,6 +572,40 @@ func runAuthRefreshWatch(manager *oauth.Manager, key, provider string, stdout io
 	return exitSuccess
 }
 
+func runAuthReset(args []string, stdout io.Writer, stderr io.Writer, deps appDeps) int {
+	parsed, err := parseAuthArgs("reset", args)
+	if err != nil {
+		return writeExecUsageError(stderr, err.Error())
+	}
+	if parsed.help {
+		_ = writeAuthHelp(stdout)
+		return exitSuccess
+	}
+	if len(parsed.positional) > 0 {
+		return writeExecUsageError(stderr, fmt.Sprintf("zero auth reset takes no arguments (got %q)", parsed.positional[0]))
+	}
+	manager, err := newAuthManager(deps, stdout)
+	if err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if err := manager.Reset(); err != nil {
+		return writeAppError(stderr, redaction.ErrorMessage(err, redaction.Options{}), exitCrash)
+	}
+	if parsed.json {
+		payload := struct {
+			Reset bool `json:"reset"`
+		}{Reset: true}
+		if err := writePrettyJSON(stdout, payload); err != nil {
+			return exitCrash
+		}
+		return exitSuccess
+	}
+	if _, err := fmt.Fprintln(stdout, "Reset OAuth token store."); err != nil {
+		return exitCrash
+	}
+	return exitSuccess
+}
+
 func filterAuthStatuses(statuses []oauth.Status, provider string) []oauth.Status {
 	want := oauth.ProviderKey(provider)
 	filtered := make([]oauth.Status, 0, 1)
@@ -589,6 +626,7 @@ Commands:
   logout <provider>                               Delete a provider's stored login
   status [provider]                               Show login presence/expiry (never the token)
   refresh <provider> [--watch]                    Force a token refresh (--watch keeps it fresh)
+  reset                                           Reset the OAuth token store (clears corrupted entries and tokens)
   openrouter                                      Log in to OpenRouter in the browser; mints an API key
   chatgpt                                         Log in to ChatGPT in the browser (Codex backend, ChatGPT Plus/Pro)
 
@@ -615,7 +653,7 @@ Flags:
       --device   Use the device-code flow (headless/SSH; no browser)
       --scope    Add an OAuth scope (repeatable)
       --watch    Keep the token fresh in the foreground (refresh only)
-      --json     Print result as JSON (status/logout)
+      --json     Print result as JSON (status/logout/reset)
   -h, --help     Show this help
 `)
 	return err

internal/cli/auth_test.go

@@ -196,13 +196,42 @@ func TestRunAuthHelp(t *testing.T) {
 	if code := runWithDeps([]string{"auth", "--help"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
 		t.Fatalf("exit = %d", code)
 	}
-	for _, want := range []string{"zero auth", "login", "logout", "status", "refresh", "--device"} {
+	for _, want := range []string{"zero auth", "login", "logout", "status", "refresh", "reset", "--device"} {
 		if !strings.Contains(stdout.String(), want) {
 			t.Fatalf("help missing %q:\n%s", want, stdout.String())
 		}
 	}
 }
 
+func TestRunAuthReset(t *testing.T) {
+	path := withAuthStore(t)
+	store, err := oauth.NewStore(oauth.StoreOptions{FilePath: path})
+	if err != nil {
+		t.Fatalf("NewStore: %v", err)
+	}
+	if err := store.Save(oauth.ProviderKey("demo"), oauth.Token{AccessToken: "secret"}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+
+	var stdout, stderr bytes.Buffer
+	if code := runWithDeps([]string{"auth", "reset"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("exit = %d stderr=%s", code, stderr.String())
+	}
+	if !strings.Contains(stdout.String(), "Reset OAuth token store") {
+		t.Fatalf("stdout = %q", stdout.String())
+	}
+
+	// Verify store is now empty.
+	stdout.Reset()
+	stderr.Reset()
+	if code := runWithDeps([]string{"auth", "status"}, &stdout, &stderr, appDeps{}); code != exitSuccess {
+		t.Fatalf("status exit = %d", code)
+	}
+	if !strings.Contains(stdout.String(), "No OAuth provider logins are stored.") {
+		t.Fatalf("expected empty store after reset, got: %q", stdout.String())
+	}
+}
+
 // TestRunAuthLoginChatGPTRoutesToDedicatedFlow verifies `zero auth login
 // chatgpt` reaches the dedicated ChatGPT login (fixed-port loopback + mandatory
 // authorize params), not the generic manager path. The generic login accepts

internal/cli/completions.go

@@ -78,7 +78,7 @@ var completionRoot = completionNode{
 			{names: []string{"tools"}, children: leafNodes("list")},
 			{names: []string{"oauth"}, children: leafNodes("login", "logout", "status")},
 		}},
-		{names: []string{"auth"}, children: leafNodes("openrouter", "chatgpt", "login", "logout", "status", "refresh")},
+		{names: []string{"auth"}, children: leafNodes("openrouter", "chatgpt", "login", "logout", "status", "refresh", "reset")},
 		{names: []string{"sandbox"}, children: []completionNode{
 			{names: []string{"policy"}}, {names: []string{"setup"}}, {names: []string{"check"}},
 			{names: []string{"grants"}, children: leafNodes("list", "allow", "deny", "revoke", "clear")},

internal/cli/completions_test.go

@@ -159,6 +159,7 @@ func TestCompletionTreeCoversAliasesNestingAndCommonFlags(t *testing.T) {
 	assertCandidates(t, byPath["worktree"], "prepare", "release")
 	assertCandidates(t, byPath["daemon"], "start", "stop", "status", "run", "attach")
 	assertCandidates(t, byPath["mcp oauth"], "login", "logout", "status")
+	assertCandidates(t, byPath["auth"], "openrouter", "chatgpt", "login", "logout", "status", "refresh", "reset")
 	assertCandidates(t, byPath["sandbox grants"], "list", "allow", "deny", "revoke", "clear")
 	assertCandidates(t, byPath["completions"], "bash", "zsh", "fish", "powershell", "elvish")
 	assertCandidates(t, byPath["plugins"], "list", "add", "info", "remove", "rm")

internal/keyring/keyring.go

@@ -9,7 +9,9 @@
 // through `security -i` (interactive mode), whose command parser is line-based
 // with a fixed 4096-byte line buffer, so Set rejects secrets containing
 // newlines or exceeding that budget rather than silently corrupting them;
-// Linux's secret-tool has no such restriction.
+// Linux's secret-tool has no such restriction. MaxSecretLen reports that budget
+// so a caller holding a larger value can split it across entries instead of
+// being turned away.
 package keyring
 
 import (
@@ -82,7 +84,7 @@ func (k *Keyring) Set(service, account, secret string) error {
 			}
 		}
 		// -U updates the item if it already exists rather than failing.
-		line := "add-generic-password -U -s " + securityQuote(service) + " -a " + securityQuote(account) + " -w " + securityQuote(secret) + "\n"
+		line := securityAddLine(service, account, secret)
 		if len(line) > securityMaxLine {
 			return wrap("set", fmt.Errorf("secret too large for the macOS security tool's %d-byte command line; use the file backend instead", securityMaxLine))
 		}
@@ -162,11 +164,42 @@ func (k *Keyring) Delete(service, account string) (bool, error) {
 	}
 }
 
+// MaxSecretLen reports the largest secret, in bytes, that Set accepts under
+// (service, account) on this platform. ok is false when the backend imposes no
+// practical limit, which is the case for Linux's secret-tool: it reads the
+// secret from stdin rather than a command line. On macOS the secret shares the
+// `security -i` command line with the service and account, so the budget
+// depends on both and a caller that splits an oversized value must size each
+// part against the exact account name it will be stored under.
+//
+// The budget assumes the secret needs no quote escaping. securityQuote only
+// expands `\` and `"`, neither of which appears in base64 or hex, so a caller
+// storing encoded data gets the exact figure.
+func (k *Keyring) MaxSecretLen(service, account string) (int, bool) {
+	if k.goos != "darwin" {
+		return 0, false
+	}
+	// Measuring the real command with an empty secret counts the surrounding
+	// quotes too, so a secret of exactly this length lands on securityMaxLine.
+	budget := securityMaxLine - len(securityAddLine(service, account, ""))
+	if budget < 0 {
+		budget = 0
+	}
+	return budget, true
+}
+
 // securityMaxLine is the most `security -i` can read as one command: its line
 // buffer is MAX_LINE_LEN (4096) bytes in Apple's SecurityTool, one of which the
 // terminating NUL consumes.
 const securityMaxLine = 4095
 
+// securityAddLine renders the `security -i` command that stores secret under
+// (service, account). Set writes it and MaxSecretLen measures it, so the two
+// cannot disagree about how much of the line the overhead consumes.
+func securityAddLine(service, account, secret string) string {
+	return "add-generic-password -U -s " + securityQuote(service) + " -a " + securityQuote(account) + " -w " + securityQuote(secret) + "\n"
+}
+
 // securityQuote wraps s for one argument of a `security -i` command line. The
 // tool's parser (split_line in Apple's SecurityTool) treats a backslash inside
 // double quotes as escaping the next character and the matching quote as the

internal/keyring/keyring_test.go

@@ -375,3 +375,46 @@ func TestAvailable(t *testing.T) {
 		t.Fatal("linux should be available")
 	}
 }
+
+// TestMaxSecretLenMatchesTheDarwinSetBoundary pins the budget to the boundary
+// Set actually enforces. A caller that splits an oversized value depends on the
+// two agreeing exactly: one byte of drift either wastes an entry or produces a
+// chunk security silently splits into two garbage commands.
+func TestMaxSecretLenMatchesTheDarwinSetBoundary(t *testing.T) {
+	k := newFake("darwin").keyring()
+	budget, bounded := k.MaxSecretLen("zero", "oauth-tokens")
+	if !bounded {
+		t.Fatal("MaxSecretLen reported darwin as unbounded")
+	}
+	if err := newFake("darwin").keyring().Set("zero", "oauth-tokens", strings.Repeat("a", budget)); err != nil {
+		t.Errorf("Set(budget=%d bytes): %v, want acceptance at the boundary", budget, err)
+	}
+	if err := newFake("darwin").keyring().Set("zero", "oauth-tokens", strings.Repeat("a", budget+1)); err == nil {
+		t.Errorf("Set(%d bytes) succeeded, want rejection one byte past the budget", budget+1)
+	}
+}
+
+// TestMaxSecretLenShrinksWithTheAccountName covers why the budget takes the
+// account: on macOS the account and the secret share one command line, so a
+// longer account name leaves less room for the secret.
+func TestMaxSecretLenShrinksWithTheAccountName(t *testing.T) {
+	k := newFake("darwin").keyring()
+	short, _ := k.MaxSecretLen("zero", "oauth-tokens")
+	long, _ := k.MaxSecretLen("zero", "oauth-tokens.a.63")
+	if want := short - len(".a.63"); long != want {
+		t.Fatalf("MaxSecretLen for the longer account = %d, want %d", long, want)
+	}
+	if err := newFake("darwin").keyring().Set("zero", "oauth-tokens.a.63", strings.Repeat("a", long+1)); err == nil {
+		t.Error("Set one byte past the longer account's budget succeeded")
+	}
+}
+
+// TestMaxSecretLenUnboundedOffDarwin keeps the limit platform-specific:
+// secret-tool reads the secret from stdin, so there is no command line to fill.
+func TestMaxSecretLenUnboundedOffDarwin(t *testing.T) {
+	for _, goos := range []string{"linux", "windows"} {
+		if n, bounded := newFake(goos).keyring().MaxSecretLen("zero", "oauth-tokens"); bounded || n != 0 {
+			t.Errorf("MaxSecretLen on %s = (%d, %v), want (0, false)", goos, n, bounded)
+		}
+	}
+}

internal/oauth/manager.go

@@ -416,6 +416,14 @@ func (m *Manager) Logout(name string) (bool, error) {
 	return m.store.Delete(ProviderKey(name))
 }
 
+// Reset clears all persistent state in the underlying store.
+func (m *Manager) Reset() error {
+	if m == nil || m.store == nil {
+		return nil
+	}
+	return m.store.Reset()
+}
+
 // StatusAll returns the status of every provider login.
 func (m *Manager) StatusAll() ([]Status, error) {
 	return m.store.Status(KeyPrefixProvider)