fix: handle context.Canceled in gemini backend to report "aborted" status

server/pkg/agent/gemini.go

@@ -0,0 +1,138 @@
+package agent
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// geminiBackend implements Backend by spawning the Google Gemini CLI
+// (`gemini -p <prompt> --yolo -o text`) and collecting its stdout.
+//
+// This is a minimal v1 implementation — it captures the final text
+// response but does not stream tool calls in real time. Follow-ups
+// can move to `-o stream-json` and parse Gemini's event schema once
+// we have a reliable reproduction of its output format.
+type geminiBackend struct {
+	cfg Config
+}
+
+func (b *geminiBackend) Execute(ctx context.Context, prompt string, opts ExecOptions) (*Session, error) {
+	execPath := b.cfg.ExecutablePath
+	if execPath == "" {
+		execPath = "gemini"
+	}
+	if _, err := exec.LookPath(execPath); err != nil {
+		return nil, fmt.Errorf("gemini executable not found at %q: %w", execPath, err)
+	}
+
+	timeout := opts.Timeout
+	if timeout == 0 {
+		timeout = 20 * time.Minute
+	}
+	runCtx, cancel := context.WithTimeout(ctx, timeout)
+
+	args := buildGeminiArgs(prompt, opts)
+
+	cmd := exec.CommandContext(runCtx, execPath, args...)
+	if opts.Cwd != "" {
+		cmd.Dir = opts.Cwd
+	}
+	cmd.Env = buildEnv(b.cfg.Env)
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		cancel()
+		return nil, fmt.Errorf("gemini stdout pipe: %w", err)
+	}
+	cmd.Stderr = newLogWriter(b.cfg.Logger, "[gemini:stderr] ")
+
+	if err := cmd.Start(); err != nil {
+		cancel()
+		return nil, fmt.Errorf("start gemini: %w", err)
+	}
+
+	b.cfg.Logger.Info("gemini started", "pid", cmd.Process.Pid, "cwd", opts.Cwd, "model", opts.Model)
+
+	msgCh := make(chan Message, 16)
+	resCh := make(chan Result, 1)
+
+	go func() {
+		defer cancel()
+		defer close(msgCh)
+		defer close(resCh)
+
+		startTime := time.Now()
+		output, readErr := io.ReadAll(bufio.NewReader(stdout))
+
+		// Forward the full response as a single text message so the daemon
+		// can persist it verbatim. Tool streaming is intentionally omitted
+		// in v1; see the file-level comment.
+		text := strings.TrimRight(string(output), "\n")
+		if text != "" {
+			trySend(msgCh, Message{Type: MessageText, Content: text})
+		}
+
+		waitErr := cmd.Wait()
+		durationMs := time.Since(startTime).Milliseconds()
+
+		result := Result{
+			Status:     "completed",
+			Output:     text,
+			DurationMs: durationMs,
+		}
+
+		if readErr != nil {
+			result.Status = "failed"
+			result.Error = fmt.Sprintf("read stdout: %s", readErr.Error())
+		} else if waitErr != nil {
+			// Distinguish context cancellation (timeout/abort) from exit errors.
+			if runCtx.Err() == context.DeadlineExceeded {
+				result.Status = "timeout"
+				result.Error = fmt.Sprintf("gemini timed out after %s", timeout)
+			} else if runCtx.Err() == context.Canceled {
+				result.Status = "aborted"
+				result.Error = "execution cancelled"
+			} else {
+				result.Status = "failed"
+				result.Error = waitErr.Error()
+			}
+		}
+
+		resCh <- result
+	}()
+
+	return &Session{Messages: msgCh, Result: resCh}, nil
+}
+
+// buildGeminiArgs assembles the argv for a one-shot gemini invocation.
+//
+// Flags:
+//
+//	-p / --prompt         non-interactive prompt (the user's task)
+//	--yolo                auto-approve all tool executions (equivalent to
+//	                      claude's --permission-mode bypassPermissions)
+//	-o text               plain text output (stream-json is a follow-up)
+//	-m <model>            optional model override (from MULTICA_GEMINI_MODEL)
+//	-r <session>          resume a previous session (if provided)
+//
+// Note: gemini reads stdin and appends it to -p when both are present.
+// The daemon does not pipe stdin, so the prompt comes exclusively from -p.
+func buildGeminiArgs(prompt string, opts ExecOptions) []string {
+	args := []string{
+		"-p", prompt,
+		"--yolo",
+		"-o", "text",
+	}
+	if opts.Model != "" {
+		args = append(args, "-m", opts.Model)
+	}
+	if opts.ResumeSessionID != "" {
+		args = append(args, "-r", opts.ResumeSessionID)
+	}
+	return args
+}