diff --git a/internal/auth/gemini/gemini_auth.go b/internal/auth/gemini/gemini_auth.go
index c459c5ca..2995a1cb 100644
--- a/internal/auth/gemini/gemini_auth.go
+++ b/internal/auth/gemini/gemini_auth.go
@@ -305,6 +305,9 @@ func (g *GeminiAuth) getTokenFromWeb(ctx context.Context, config *oauth2.Config,
 		defer manualPromptTimer.Stop()
 	}
 
+	var manualInputCh <-chan string
+	var manualInputErrCh <-chan error
+
 waitForCallback:
 	for {
 		select {
@@ -326,13 +329,14 @@ waitForCallback:
 				return nil, err
 			default:
 			}
-			input, err := opts.Prompt("Paste the Gemini callback URL (or press Enter to keep waiting): ")
-			if err != nil {
-				return nil, err
-			}
-			parsed, err := misc.ParseOAuthCallback(input)
-			if err != nil {
-				return nil, err
+			manualInputCh, manualInputErrCh = misc.AsyncPrompt(opts.Prompt, "Paste the Gemini callback URL (or press Enter to keep waiting): ")
+			continue
+		case input := <-manualInputCh:
+			manualInputCh = nil
+			manualInputErrCh = nil
+			parsed, errParse := misc.ParseOAuthCallback(input)
+			if errParse != nil {
+				return nil, errParse
 			}
 			if parsed == nil {
 				continue
@@ -345,6 +349,8 @@ waitForCallback:
 			}
 			authCode = parsed.Code
 			break waitForCallback
+		case errManual := <-manualInputErrCh:
+			return nil, errManual
 		case <-timeoutTimer.C:
 			return nil, fmt.Errorf("oauth flow timed out")
 		}
diff --git a/internal/misc/oauth.go b/internal/misc/oauth.go
index c14f39d2..88be2eef 100644
--- a/internal/misc/oauth.go
+++ b/internal/misc/oauth.go
@@ -30,6 +30,23 @@ type OAuthCallback struct {
 	ErrorDescription string
 }
 
+// AsyncPrompt runs a prompt function in a goroutine and returns channels for
+// the result. The returned channels are buffered (size 1) so the goroutine can
+// complete even if the caller abandons the channels.
+func AsyncPrompt(promptFn func(string) (string, error), message string) (<-chan string, <-chan error) {
+	inputCh := make(chan string, 1)
+	errCh := make(chan error, 1)
+	go func() {
+		input, err := promptFn(message)
+		if err != nil {
+			errCh <- err
+			return
+		}
+		inputCh <- input
+	}()
+	return inputCh, errCh
+}
+
 // ParseOAuthCallback extracts OAuth parameters from a callback URL.
 // It returns nil when the input is empty.
 func ParseOAuthCallback(input string) (*OAuthCallback, error) {
diff --git a/sdk/auth/antigravity.go b/sdk/auth/antigravity.go
index 6ed31d6d..d52bf1d2 100644
--- a/sdk/auth/antigravity.go
+++ b/sdk/auth/antigravity.go
@@ -98,6 +98,9 @@ func (AntigravityAuthenticator) Login(ctx context.Context, cfg *config.Config, o
 		defer manualPromptTimer.Stop()
 	}
 
+	var manualInputCh <-chan string
+	var manualInputErrCh <-chan error
+
 waitForCallback:
 	for {
 		select {
@@ -115,10 +118,11 @@ waitForCallback:
 				break waitForCallback
 			default:
 			}
-			input, errPrompt := opts.Prompt("Paste the antigravity callback URL (or press Enter to keep waiting): ")
-			if errPrompt != nil {
-				return nil, errPrompt
-			}
+			manualInputCh, manualInputErrCh = misc.AsyncPrompt(opts.Prompt, "Paste the antigravity callback URL (or press Enter to keep waiting): ")
+			continue
+		case input := <-manualInputCh:
+			manualInputCh = nil
+			manualInputErrCh = nil
 			parsed, errParse := misc.ParseOAuthCallback(input)
 			if errParse != nil {
 				return nil, errParse
@@ -132,6 +136,8 @@ waitForCallback:
 				Error: parsed.Error,
 			}
 			break waitForCallback
+		case errManual := <-manualInputErrCh:
+			return nil, errManual
 		case <-timeoutTimer.C:
 			return nil, fmt.Errorf("antigravity: authentication timed out")
 		}
diff --git a/sdk/auth/claude.go b/sdk/auth/claude.go
index 706763b3..d82a718b 100644
--- a/sdk/auth/claude.go
+++ b/sdk/auth/claude.go
@@ -124,6 +124,9 @@ func (a *ClaudeAuthenticator) Login(ctx context.Context, cfg *config.Config, opt
 		defer manualPromptTimer.Stop()
 	}
 
+	var manualInputCh <-chan string
+	var manualInputErrCh <-chan error
+
 waitForCallback:
 	for {
 		select {
@@ -149,10 +152,11 @@ waitForCallback:
 				return nil, err
 			default:
 			}
-			input, errPrompt := opts.Prompt("Paste the Claude callback URL (or press Enter to keep waiting): ")
-			if errPrompt != nil {
-				return nil, errPrompt
-			}
+			manualInputCh, manualInputErrCh = misc.AsyncPrompt(opts.Prompt, "Paste the Claude callback URL (or press Enter to keep waiting): ")
+			continue
+		case input := <-manualInputCh:
+			manualInputCh = nil
+			manualInputErrCh = nil
 			parsed, errParse := misc.ParseOAuthCallback(input)
 			if errParse != nil {
 				return nil, errParse
@@ -167,6 +171,8 @@ waitForCallback:
 				Error: parsed.Error,
 			}
 			break waitForCallback
+		case errManual := <-manualInputErrCh:
+			return nil, errManual
 		}
 	}
 
diff --git a/sdk/auth/codex.go b/sdk/auth/codex.go
index 1af36936..269e3d8b 100644
--- a/sdk/auth/codex.go
+++ b/sdk/auth/codex.go
@@ -127,6 +127,9 @@ func (a *CodexAuthenticator) Login(ctx context.Context, cfg *config.Config, opts
 		defer manualPromptTimer.Stop()
 	}
 
+	var manualInputCh <-chan string
+	var manualInputErrCh <-chan error
+
 waitForCallback:
 	for {
 		select {
@@ -152,10 +155,11 @@ waitForCallback:
 				return nil, err
 			default:
 			}
-			input, errPrompt := opts.Prompt("Paste the Codex callback URL (or press Enter to keep waiting): ")
-			if errPrompt != nil {
-				return nil, errPrompt
-			}
+			manualInputCh, manualInputErrCh = misc.AsyncPrompt(opts.Prompt, "Paste the Codex callback URL (or press Enter to keep waiting): ")
+			continue
+		case input := <-manualInputCh:
+			manualInputCh = nil
+			manualInputErrCh = nil
 			parsed, errParse := misc.ParseOAuthCallback(input)
 			if errParse != nil {
 				return nil, errParse
@@ -170,6 +174,8 @@ waitForCallback:
 				Error: parsed.Error,
 			}
 			break waitForCallback
+		case errManual := <-manualInputErrCh:
+			return nil, errManual
 		}
 	}
 
diff --git a/sdk/auth/iflow.go b/sdk/auth/iflow.go
index a695311d..584a3169 100644
--- a/sdk/auth/iflow.go
+++ b/sdk/auth/iflow.go
@@ -109,6 +109,9 @@ func (a *IFlowAuthenticator) Login(ctx context.Context, cfg *config.Config, opts
 		defer manualPromptTimer.Stop()
 	}
 
+	var manualInputCh <-chan string
+	var manualInputErrCh <-chan error
+
 waitForCallback:
 	for {
 		select {
@@ -128,10 +131,11 @@ waitForCallback:
 				return nil, fmt.Errorf("iflow auth: callback wait failed: %w", err)
 			default:
 			}
-			input, errPrompt := opts.Prompt("Paste the iFlow callback URL (or press Enter to keep waiting): ")
-			if errPrompt != nil {
-				return nil, errPrompt
-			}
+			manualInputCh, manualInputErrCh = misc.AsyncPrompt(opts.Prompt, "Paste the iFlow callback URL (or press Enter to keep waiting): ")
+			continue
+		case input := <-manualInputCh:
+			manualInputCh = nil
+			manualInputErrCh = nil
 			parsed, errParse := misc.ParseOAuthCallback(input)
 			if errParse != nil {
 				return nil, errParse
@@ -145,6 +149,8 @@ waitForCallback:
 				Error: parsed.Error,
 			}
 			break waitForCallback
+		case errManual := <-manualInputErrCh:
+			return nil, errManual
 		}
 	}
 	if result.Error != "" {