feat: add opencode harness coverage and streaming tests

Author: easel

cmd/dun/main.go

@@ -120,7 +120,7 @@ LOOP MODE:
   and repeats until all checks pass or max iterations is reached.
 
   Options:
-    --harness     Agent to use: codex, claude, gemini (default: from config)
+    --harness     Agent to use: codex, claude, gemini, opencode (default: from config)
     --automation  Mode: manual, plan, auto, yolo (default: auto)
     --max-iterations  Safety limit (default: 100)
     --dry-run     Show prompt without calling agent
@@ -130,7 +130,7 @@ LOOP MODE:
 
   Quorum Options (multi-agent consensus):
     --quorum      Strategy: any, majority, unanimous, or number (e.g., 2)
-    --harnesses   Comma-separated list of harnesses (e.g., codex,claude,gemini)
+    --harnesses   Comma-separated list of harnesses (e.g., codex,claude,gemini,opencode)
     --cost-mode   Run harnesses sequentially to minimize cost
     --escalate    Pause for human review on conflict
     --prefer      Preferred harness on conflict (e.g., codex)
@@ -142,7 +142,7 @@ LOOP MODE:
     dun loop --automation yolo            # Allow autonomous edits
     dun loop --dry-run                    # Preview prompt
     dun loop --verbose                    # Show prompt and responses
-    dun loop --quorum majority --harnesses codex,claude,gemini
+    dun loop --quorum majority --harnesses codex,claude,gemini,opencode
     dun loop --quorum 2 --harnesses codex,claude --prefer codex
 
 VERSION:
@@ -500,7 +500,7 @@ func runLoop(args []string, stdout io.Writer, stderr io.Writer) int {
 	fs := flag.NewFlagSet("loop", flag.ContinueOnError)
 	fs.SetOutput(stderr)
 	configPath := fs.String("config", explicitConfig, "path to config file")
-	harness := fs.String("harness", "", "agent harness (codex|claude|gemini); default from config")
+	harness := fs.String("harness", "", "agent harness (codex|claude|gemini|opencode); default from config")
 	automation := fs.String("automation", opts.AutomationMode, "automation mode (manual|plan|auto|yolo)")
 	maxIterations := fs.Int("max-iterations", 100, "maximum iterations before stopping")
 	dryRun := fs.Bool("dry-run", false, "print prompt without calling harness")

cmd/dun/main_test.go

@@ -1320,7 +1320,7 @@ func TestRunHelpIncludesLoop(t *testing.T) {
 	if !strings.Contains(output, "--max-iterations") {
 		t.Fatalf("help should document max-iterations option")
 	}
-	if !strings.Contains(output, "codex, claude, gemini") {
+	if !strings.Contains(output, "codex, claude, gemini, opencode") {
 		t.Fatalf("help should list available harnesses")
 	}
 }

docs/design/contracts/API-001-dun-cli.md

@@ -207,7 +207,7 @@ $ dun check --prompt
 
 **Options**:
 - `--config` : Path to config file (default `.dun/config.yaml` if present)
-- `--harness` : Agent harness (`codex`, `claude`, `gemini`, default from config)
+- `--harness` : Agent harness (`codex`, `claude`, `gemini`, `opencode`, default from config)
 - `--automation` : Automation mode (`manual`, `plan`, `auto`, `yolo`, default `auto`)
 - `--max-iterations` : Maximum iterations before stopping (default `100`)
 - `--dry-run` : Print prompt without calling harness

internal/dun/harness.go

@@ -107,6 +107,7 @@ func NewHarnessRegistry() *HarnessRegistry {
 	r.Register("claude", NewClaudeHarness)
 	r.Register("gemini", NewGeminiHarness)
 	r.Register("codex", NewCodexHarness)
+	r.Register("opencode", NewOpenCodeHarness)
 	r.Register("mock", NewMockHarness)
 	return r
 }
@@ -300,6 +301,44 @@ func (h *CodexHarness) runCommand(ctx context.Context, name string, stdin string
 	return runHarnessCommand(ctx, h.config, name, stdin, args)
 }
 
+// OpenCodeHarness wraps the OpenCode CLI for agent execution.
+type OpenCodeHarness struct {
+	config HarnessConfig
+}
+
+// NewOpenCodeHarness creates a new OpenCode harness.
+func NewOpenCodeHarness(config HarnessConfig) Harness {
+	if config.Command == "" {
+		config.Command = "opencode"
+	}
+	if config.AutomationMode == "" {
+		config.AutomationMode = AutomationAuto
+	}
+	return &OpenCodeHarness{config: config}
+}
+
+// Name returns "opencode".
+func (h *OpenCodeHarness) Name() string {
+	return "opencode"
+}
+
+// Execute runs the OpenCode CLI with the given prompt.
+// OpenCode expects the prompt as a positional message for `opencode run`.
+func (h *OpenCodeHarness) Execute(ctx context.Context, prompt string) (string, error) {
+	args := []string{"run", prompt}
+
+	return h.runCommand(ctx, h.config.Command, prompt, args...)
+}
+
+// SupportsAutomation returns true for all automation modes.
+func (h *OpenCodeHarness) SupportsAutomation(mode AutomationMode) bool {
+	return true
+}
+
+func (h *OpenCodeHarness) runCommand(ctx context.Context, name string, stdin string, args ...string) (string, error) {
+	return runHarnessCommand(ctx, h.config, name, stdin, args)
+}
+
 // MockHarness is a harness for testing that returns configurable responses.
 type MockHarness struct {
 	config HarnessConfig

internal/dun/harness_integration_test.go

@@ -25,6 +25,10 @@ func TestCodexHarnessIntegration(t *testing.T) {
 	runHarnessIntegration(t, "codex", NewCodexHarness)
 }
 
+func TestOpenCodeHarnessIntegration(t *testing.T) {
+	runHarnessIntegration(t, "opencode", NewOpenCodeHarness)
+}
+
 func runHarnessIntegration(t *testing.T, command string, factory HarnessFactory) {
 	t.Helper()
 	if os.Getenv(harnessIntegrationEnv) == "" {