fix(adapters): ground native schemas, merge-not-replace, add goose/cagent/zed

- common/mcp.go: MCPStyle enum + BuildMCPMapStyled for claude/crush/opencode/zed dialects
- common/jsonmerge.go: MergeJSONKeys (JSON-first, JSONC fallback) preserves user keys;
  fix: try plain json.Unmarshal before StripJSONComments to avoid mangling URLs with //
- common/yamlmerge.go: MergeYAMLKeys for YAML configs (goose)
- common/blocks.go: add ProvidersAsMap for opencode map-shaped provider key
- claudecode: merge settings.json (preserves hooks/permissions/env); MCPClaudeStyle (no type field)
- crush: fix mcp key (was mcpServers); MCPCrushStyle entries include type field; merge crush.json; fix import key mcp
- kilo: drop providers key (kilo has none); MCPOpencodeStyle (local/remote); merge kilo.json
- opencode: fix provider (singular map) + model (not default_model); MCPOpencodeStyle; merge jsonc; fix import key mcp
- goose: new adapter — YAML merge, extensions map, splitProviderModel, import reconstructs MCP from extensions
- cagent: new adapter — renders starter default.yaml, import returns empty
- zed: new adapter — merge settings.json, context_servers (MCPZedStyle) + agent.default_model
- docs: append Grounded harness schemas section to design spec

internal/adapter/common/blocks.go

@@ -48,6 +48,45 @@ func buildModels(models []canonical.Model) []map[string]any {
 	return out
 }
 
+// ProvidersAsMap returns a name-keyed map of provider objects for harnesses
+// like opencode that use `provider` (singular, map-shaped) instead of a slice.
+// The gateway entry is keyed "harness-sync-gateway"; upstreams use their name.
+func ProvidersAsMap(p *canonical.Profile) map[string]any {
+	out := map[string]any{}
+	if p.Gateway.URL != "" {
+		entry := map[string]any{
+			"name": "harness-sync gateway",
+			"options": map[string]any{
+				"baseURL": p.Gateway.URL,
+				"apiKey":  p.Gateway.Token,
+			},
+		}
+		if models := buildModels(p.Models); len(models) > 0 {
+			modelsMap := map[string]any{}
+			for _, m := range p.Models {
+				modelsMap[m.ID] = map[string]any{"name": m.ID}
+			}
+			entry["models"] = modelsMap
+		}
+		out["harness-sync-gateway"] = entry
+	}
+	for _, up := range p.Upstreams {
+		entry := map[string]any{"name": up.Name}
+		opts := map[string]any{}
+		if up.BaseURL != "" {
+			opts["baseURL"] = up.BaseURL
+		}
+		if up.APIKey != "" {
+			opts["apiKey"] = up.APIKey
+		}
+		if len(opts) > 0 {
+			entry["options"] = opts
+		}
+		out[up.Name] = entry
+	}
+	return out
+}
+
 // BuildMCPMap returns canonical MCP servers as a name -> object map.
 // Empty map (not nil) is returned when there are no servers so the caller
 // can decide whether to include the key.

internal/adapter/common/jsonmerge.go

@@ -0,0 +1,34 @@
+package common
+
+import "encoding/json"
+
+// MergeJSONKeys reads existing JSON/JSONC body, overlays the given top-level
+// keys (replacing values for listed keys, preserving every other key), and
+// returns the merged JSON. If existing is empty or invalid JSON the function
+// returns just the overlay encoded fresh (2-space indent + trailing \n).
+// An overlay value of nil deletes the key from the base.
+func MergeJSONKeys(existing []byte, overlay map[string]any) ([]byte, error) {
+	base := map[string]any{}
+	if len(existing) > 0 {
+		// Try plain JSON first (avoids mangling URL strings that contain //).
+		// Only fall back to comment-stripping for JSONC content.
+		if err := json.Unmarshal(existing, &base); err != nil {
+			clean := StripJSONComments(string(existing))
+			if err2 := json.Unmarshal([]byte(clean), &base); err2 != nil {
+				base = map[string]any{}
+			}
+		}
+	}
+	for k, v := range overlay {
+		if v == nil {
+			delete(base, k)
+			continue
+		}
+		base[k] = v
+	}
+	out, err := json.MarshalIndent(base, "", "  ")
+	if err != nil {
+		return nil, err
+	}
+	return append(out, '\n'), nil
+}

internal/adapter/common/jsonmerge_test.go

@@ -0,0 +1,80 @@
+package common
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMergeJSONKeysPreservesOtherKeys(t *testing.T) {
+	existing := []byte(`{"a":1,"b":2}`)
+	overlay := map[string]any{"b": 3, "c": 4}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.Equal(t, float64(3), m["b"])
+	assert.Equal(t, float64(4), m["c"])
+}
+
+func TestMergeJSONKeysEmptyExisting(t *testing.T) {
+	overlay := map[string]any{"x": "y"}
+	out, err := MergeJSONKeys(nil, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, "y", m["x"])
+	assert.Len(t, m, 1)
+}
+
+func TestMergeJSONKeysInvalidExisting(t *testing.T) {
+	existing := []byte(`not json at all`)
+	overlay := map[string]any{"k": "v"}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, "v", m["k"])
+	assert.Len(t, m, 1)
+}
+
+func TestMergeJSONKeysNilOverlayValueDeletesKey(t *testing.T) {
+	existing := []byte(`{"a":1,"b":2}`)
+	overlay := map[string]any{"b": nil}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.NotContains(t, m, "b")
+}
+
+func TestMergeJSONKeysJSONC(t *testing.T) {
+	existing := []byte(`// comment
+{
+  "a": 1, // trailing
+  /* block */ "b": 2
+}`)
+	overlay := map[string]any{"c": 3}
+	out, err := MergeJSONKeys(existing, overlay)
+	require.NoError(t, err)
+
+	var m map[string]any
+	require.NoError(t, json.Unmarshal(out, &m))
+	assert.Equal(t, float64(1), m["a"])
+	assert.Equal(t, float64(2), m["b"])
+	assert.Equal(t, float64(3), m["c"])
+}
+
+func TestMergeJSONKeysTrailingNewline(t *testing.T) {
+	out, err := MergeJSONKeys(nil, map[string]any{"k": "v"})
+	require.NoError(t, err)
+	assert.Equal(t, '\n', rune(out[len(out)-1]))
+}

internal/adapter/common/mcp.go

@@ -0,0 +1,102 @@
+package common
+
+import "github.com/lukaszraczylo/harness-sync/internal/canonical"
+
+// MCPStyle selects the dialect for MCP server entries.
+type MCPStyle int
+
+const (
+	// MCPClaudeStyle: claude-code shape — {command, args, env, url, transport}.
+	MCPClaudeStyle MCPStyle = iota
+	// MCPCrushStyle: crush shape — adds type: stdio|http|sse.
+	MCPCrushStyle
+	// MCPOpencodeStyle: kilo + opencode shape — type: local|remote, command as []string.
+	MCPOpencodeStyle
+	// MCPZedStyle: zed context_servers — {enabled, source, command, args} or {enabled, url}.
+	MCPZedStyle
+)
+
+// BuildMCPMapStyled returns the MCP map for the given harness dialect.
+func BuildMCPMapStyled(reg *canonical.MCPRegistry, style MCPStyle) map[string]any {
+	out := map[string]any{}
+	if reg == nil {
+		return out
+	}
+	for _, s := range reg.Servers {
+		out[s.Name] = mcpEntry(s, style)
+	}
+	return out
+}
+
+func mcpEntry(s canonical.MCPServer, style MCPStyle) map[string]any {
+	e := map[string]any{}
+	switch style {
+	case MCPClaudeStyle:
+		if s.Command != "" {
+			e["command"] = s.Command
+		}
+		if len(s.Args) > 0 {
+			e["args"] = s.Args
+		}
+		if s.URL != "" {
+			e["url"] = s.URL
+		}
+		if s.Transport != "" {
+			e["transport"] = s.Transport
+		}
+		if len(s.Env) > 0 {
+			e["env"] = s.Env
+		}
+	case MCPCrushStyle:
+		if s.URL != "" {
+			t := s.Transport
+			if t == "" {
+				t = "http"
+			}
+			e["type"] = t
+			e["url"] = s.URL
+		} else {
+			e["type"] = "stdio"
+			if s.Command != "" {
+				e["command"] = s.Command
+			}
+			if len(s.Args) > 0 {
+				e["args"] = s.Args
+			}
+			if len(s.Env) > 0 {
+				e["env"] = s.Env
+			}
+		}
+	case MCPOpencodeStyle:
+		if s.URL != "" {
+			e["type"] = "remote"
+			e["url"] = s.URL
+		} else {
+			e["type"] = "local"
+			cmd := []string{}
+			if s.Command != "" {
+				cmd = append(cmd, s.Command)
+			}
+			cmd = append(cmd, s.Args...)
+			e["command"] = cmd
+			if len(s.Env) > 0 {
+				e["environment"] = s.Env
+			}
+		}
+		e["enabled"] = true
+	case MCPZedStyle:
+		e["enabled"] = true
+		if s.URL != "" {
+			e["url"] = s.URL
+		} else {
+			e["source"] = "custom"
+			if s.Command != "" {
+				e["command"] = s.Command
+			}
+			if len(s.Args) > 0 {
+				e["args"] = s.Args
+			}
+		}
+	}
+	return e
+}

internal/adapter/common/mcp_test.go

@@ -0,0 +1,110 @@
+package common
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+func reg(servers ...canonical.MCPServer) *canonical.MCPRegistry {
+	return &canonical.MCPRegistry{Servers: servers}
+}
+
+func TestBuildMCPMapStyledClaudeStyle(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Args: []string{"--flag"}, Transport: "stdio"})
+	out := BuildMCPMapStyled(r, MCPClaudeStyle)
+	require.Contains(t, out, "fp")
+	e := out["fp"].(map[string]any)
+	assert.Equal(t, "/bin/fp", e["command"])
+	assert.Equal(t, []string{"--flag"}, e["args"])
+	assert.Equal(t, "stdio", e["transport"])
+	assert.NotContains(t, e, "type")
+}
+
+func TestBuildMCPMapStyledClaudeStyleURL(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "remote", URL: "https://example.com"})
+	out := BuildMCPMapStyled(r, MCPClaudeStyle)
+	e := out["remote"].(map[string]any)
+	assert.Equal(t, "https://example.com", e["url"])
+	assert.NotContains(t, e, "type")
+}
+
+func TestBuildMCPMapStyledCrushStdio(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Args: []string{"-x"}})
+	out := BuildMCPMapStyled(r, MCPCrushStyle)
+	e := out["fp"].(map[string]any)
+	assert.Equal(t, "stdio", e["type"])
+	assert.Equal(t, "/bin/fp", e["command"])
+	assert.Equal(t, []string{"-x"}, e["args"])
+}
+
+func TestBuildMCPMapStyledCrushHTTP(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "remote", URL: "https://example.com", Transport: "sse"})
+	out := BuildMCPMapStyled(r, MCPCrushStyle)
+	e := out["remote"].(map[string]any)
+	assert.Equal(t, "sse", e["type"])
+	assert.Equal(t, "https://example.com", e["url"])
+}
+
+func TestBuildMCPMapStyledCrushHTTPDefaultType(t *testing.T) {
+	// No transport set → default to "http"
+	r := reg(canonical.MCPServer{Name: "remote", URL: "https://example.com"})
+	out := BuildMCPMapStyled(r, MCPCrushStyle)
+	e := out["remote"].(map[string]any)
+	assert.Equal(t, "http", e["type"])
+}
+
+func TestBuildMCPMapStyledOpencodeLocal(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Args: []string{"--flag"}})
+	out := BuildMCPMapStyled(r, MCPOpencodeStyle)
+	e := out["fp"].(map[string]any)
+	assert.Equal(t, "local", e["type"])
+	assert.Equal(t, true, e["enabled"])
+	cmd := e["command"].([]string)
+	assert.Equal(t, []string{"/bin/fp", "--flag"}, cmd)
+	assert.NotContains(t, e, "environment")
+}
+
+func TestBuildMCPMapStyledOpencodeRemote(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "r", URL: "https://example.com"})
+	out := BuildMCPMapStyled(r, MCPOpencodeStyle)
+	e := out["r"].(map[string]any)
+	assert.Equal(t, "remote", e["type"])
+	assert.Equal(t, true, e["enabled"])
+	assert.Equal(t, "https://example.com", e["url"])
+}
+
+func TestBuildMCPMapStyledOpencodeEnv(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Env: map[string]string{"K": "V"}})
+	out := BuildMCPMapStyled(r, MCPOpencodeStyle)
+	e := out["fp"].(map[string]any)
+	assert.Equal(t, map[string]string{"K": "V"}, e["environment"])
+}
+
+func TestBuildMCPMapStyledZedStdio(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "fp", Command: "/bin/fp", Args: []string{"-x"}})
+	out := BuildMCPMapStyled(r, MCPZedStyle)
+	e := out["fp"].(map[string]any)
+	assert.Equal(t, true, e["enabled"])
+	assert.Equal(t, "custom", e["source"])
+	assert.Equal(t, "/bin/fp", e["command"])
+	assert.Equal(t, []string{"-x"}, e["args"])
+}
+
+func TestBuildMCPMapStyledZedURL(t *testing.T) {
+	r := reg(canonical.MCPServer{Name: "r", URL: "https://example.com"})
+	out := BuildMCPMapStyled(r, MCPZedStyle)
+	e := out["r"].(map[string]any)
+	assert.Equal(t, true, e["enabled"])
+	assert.Equal(t, "https://example.com", e["url"])
+	assert.NotContains(t, e, "source")
+}
+
+func TestBuildMCPMapStyledNilReg(t *testing.T) {
+	out := BuildMCPMapStyled(nil, MCPClaudeStyle)
+	assert.NotNil(t, out)
+	assert.Len(t, out, 0)
+}

internal/adapter/common/yamlmerge.go

@@ -0,0 +1,29 @@
+package common
+
+import "gopkg.in/yaml.v3"
+
+// MergeYAMLKeys reads existing YAML body, overlays the given top-level keys
+// (replacing values for listed keys, preserving every other key), and returns
+// the merged YAML. If existing is empty or invalid YAML, the function returns
+// just the overlay encoded fresh (with 2-space indent + trailing \n).
+// An overlay value of nil deletes the key from the base.
+func MergeYAMLKeys(existing []byte, overlay map[string]any) ([]byte, error) {
+	base := map[string]any{}
+	if len(existing) > 0 {
+		if err := yaml.Unmarshal(existing, &base); err != nil {
+			base = map[string]any{}
+		}
+	}
+	for k, v := range overlay {
+		if v == nil {
+			delete(base, k)
+			continue
+		}
+		base[k] = v
+	}
+	out, err := yaml.Marshal(base)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}

internal/adapters/cagent/cagent.go

@@ -0,0 +1,118 @@
+// Package cagent is the cagent harness adapter.
+//
+// cagent is per-run (no persistent agent state). v1 renders a starter
+// ~/.config/cagent/default.yaml with a single default agent pointing at the
+// gateway. Import always returns an empty result.
+package cagent
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+
+	"gopkg.in/yaml.v3"
+)
+
+const name = "cagent"
+
+// Adapter implements adapter.Adapter for the cagent harness.
+type Adapter struct{ home string }
+
+// Option configures an Adapter.
+type Option func(*Adapter)
+
+// WithHome overrides the home directory (defaults to os.UserHomeDir).
+func WithHome(h string) Option { return func(a *Adapter) { a.home = h } }
+
+// New returns a new Adapter with the given options applied.
+func New(opts ...Option) *Adapter {
+	a := &Adapter{home: defaultHome()}
+	for _, o := range opts {
+		o(a)
+	}
+	return a
+}
+
+func defaultHome() string {
+	h, err := os.UserHomeDir()
+	if err != nil {
+		return ""
+	}
+	return h
+}
+
+// Name returns the harness identifier.
+func (a *Adapter) Name() string { return name }
+
+// Detect returns true when ~/.config/cagent/ exists.
+func (a *Adapter) Detect() bool {
+	_, err := os.Stat(filepath.Join(a.home, ".config", "cagent"))
+	return err == nil
+}
+
+// Render produces a starter default.yaml for cagent.
+func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
+	fs := adapter.NewFileSet()
+	cfgPath := filepath.Join(a.home, ".config", "cagent", "default.yaml")
+
+	instructions := b.Instructions.Global
+	if override, ok := b.Instructions.PerHarness[name]; ok && override != "" {
+		instructions = override
+	}
+
+	mcps := map[string]any{}
+	for _, s := range b.MCP.Servers {
+		e := map[string]any{}
+		if s.Command != "" {
+			e["command"] = s.Command
+		}
+		args := s.Args
+		if args == nil {
+			args = []string{}
+		}
+		e["args"] = args
+		mcps[s.Name] = e
+	}
+
+	cfg := map[string]any{
+		"version": 8,
+		"metadata": map[string]any{
+			"name": "harness-sync",
+		},
+		"agents": map[string]any{
+			"default": map[string]any{
+				"model":       "gateway/" + b.Profile.Gateway.DefaultModel,
+				"instruction": instructions,
+			},
+		},
+		"models": map[string]any{
+			"gateway": map[string]any{
+				"provider": "openai", // cagent gateway via openai-compat
+				"base_url": b.Profile.Gateway.URL,
+			},
+		},
+	}
+	if len(mcps) > 0 {
+		cfg["mcps"] = mcps
+	}
+
+	body, err := yaml.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	fs.Add(adapter.File{
+		Dest:    cfgPath,
+		Kind:    adapter.RenderedFile,
+		Content: body,
+	})
+
+	return fs, nil
+}
+
+// Import returns an empty result — cagent has no persistent state to import.
+func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
+	return &adapter.ImportResult{}, nil
+}

internal/adapters/cagent/cagent_test.go

@@ -0,0 +1,98 @@
+package cagent
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+func bundle() *canonical.Bundle {
+	return &canonical.Bundle{
+		Root: "/canon",
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{
+				URL:          "https://gw",
+				DefaultModel: "claude-sonnet-4-6",
+			},
+		},
+		Instructions: canonical.Instructions{Global: "# global instruction"},
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "filepuff", Command: "/bin/filepuff", Args: []string{"--serve"}},
+		}},
+	}
+}
+
+func TestCagentRenderProducesExpectedTargets(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	fs, err := ad.Render(bundle())
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "cagent", "default.yaml")
+	require.Contains(t, seen, cfgDest)
+	assert.Equal(t, adapter.RenderedFile, seen[cfgDest].Kind)
+
+	var parsed map[string]any
+	require.NoError(t, yaml.Unmarshal(seen[cfgDest].Content, &parsed))
+
+	assert.Equal(t, 8, parsed["version"])
+
+	agents := parsed["agents"].(map[string]any)
+	def := agents["default"].(map[string]any)
+	assert.Equal(t, "gateway/claude-sonnet-4-6", def["model"])
+	assert.Contains(t, def["instruction"], "# global instruction")
+
+	models := parsed["models"].(map[string]any)
+	gw := models["gateway"].(map[string]any)
+	assert.Equal(t, "openai", gw["provider"])
+	assert.Equal(t, "https://gw", gw["base_url"])
+
+	mcps := parsed["mcps"].(map[string]any)
+	fp := mcps["filepuff"].(map[string]any)
+	assert.Equal(t, "/bin/filepuff", fp["command"])
+}
+
+func TestCagentRenderNoMCP(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{URL: "https://gw", DefaultModel: "sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "cagent", "default.yaml")
+	var parsed map[string]any
+	require.NoError(t, yaml.Unmarshal(seen[cfgDest].Content, &parsed))
+	assert.NotContains(t, parsed, "mcps")
+}
+
+func TestCagentImportReturnsEmpty(t *testing.T) {
+	ad := New(WithHome(t.TempDir()))
+	res, err := ad.Import(t.TempDir())
+	require.NoError(t, err)
+	assert.NotNil(t, res)
+	assert.Empty(t, res.MCP)
+	assert.Empty(t, res.Skills)
+	assert.Empty(t, res.Agents)
+}
+
+func TestCagentDetect(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	assert.False(t, ad.Detect())
+}

internal/adapters/claudecode/claudecode.go

@@ -8,7 +8,6 @@ import (
 	"github.com/lukaszraczylo/harness-sync/internal/adapter"
 	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
 	"github.com/lukaszraczylo/harness-sync/internal/canonical"
-	"github.com/lukaszraczylo/harness-sync/internal/render"
 )
 
 const name = "claude-code"
@@ -51,6 +50,9 @@ func (a *Adapter) Detect() bool {
 }
 
 // Render produces the FileSet that applies the canonical bundle to claude-code.
+// settings.json is MERGED into any existing file so user-managed keys
+// settings.json is MERGED into any existing file so user-managed keys
+// (hooks, permissions, env, …) are preserved.
 func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 	fs := adapter.NewFileSet()
 	base := filepath.Join(a.home, ".claude")
@@ -76,25 +78,24 @@ func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 		Content: []byte(instructions),
 	})
 
-	settings, err := renderSettings(b)
+	settingsPath := filepath.Join(base, "settings.json")
+	existing, _ := os.ReadFile(settingsPath)
+	overlay := map[string]any{
+		"mcpServers": common.BuildMCPMapStyled(&b.MCP, common.MCPClaudeStyle),
+	}
+	merged, err := common.MergeJSONKeys(existing, overlay)
 	if err != nil {
 		return nil, err
 	}
 	fs.Add(adapter.File{
-		Dest:    filepath.Join(base, "settings.json"),
+		Dest:    settingsPath,
 		Kind:    adapter.RenderedFile,
-		Content: settings,
+		Content: merged,
 	})
 
 	return fs, nil
 }
 
-func renderSettings(b *canonical.Bundle) ([]byte, error) {
-	return render.JSON(map[string]any{
-		"mcpServers": common.BuildMCPMap(&b.MCP),
-	})
-}
-
 // Import reads claude-code config from home and returns a canonical ImportResult.
 func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
 	return importFrom(home)

internal/adapters/claudecode/claudecode_test.go

@@ -48,6 +48,48 @@ func TestRenderProducesExpectedTargets(t *testing.T) {
 	assert.Contains(t, settingsBody, "filepuff")
 	assert.Contains(t, settingsBody, "/bin/filepuff")
 }
+func TestRenderMergesExistingSettings(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".claude")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	// Existing settings.json with user-managed keys.
+	existing := map[string]any{
+		"hooks":       map[string]any{"preToolUse": []string{"/bin/hook"}},
+		"permissions": map[string]any{"allow": []string{"Bash"}},
+		"env":         map[string]any{"ANTHROPIC_DEFAULT_MODEL": "opus"},
+	}
+	body, _ := json.Marshal(existing)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "settings.json"), body, 0o600))
+
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Root: "/canon",
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "filepuff", Command: "/bin/filepuff"},
+		}},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	settingsDest := filepath.Join(base, "settings.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[settingsDest].Content, &parsed))
+
+	// User keys preserved.
+	assert.Contains(t, parsed, "hooks")
+	assert.Contains(t, parsed, "permissions")
+	assert.Contains(t, parsed, "env")
+	// MCP updated.
+	mcp := parsed["mcpServers"].(map[string]any)
+	assert.Contains(t, mcp, "filepuff")
+	// MCP entries must NOT have a "type" field (claude-code style).
+	fp := mcp["filepuff"].(map[string]any)
+	assert.NotContains(t, fp, "type")
+}
 
 func TestImport(t *testing.T) {
 	home := t.TempDir()

internal/adapters/crush/crush.go

@@ -8,7 +8,6 @@ import (
 	"github.com/lukaszraczylo/harness-sync/internal/adapter"
 	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
 	"github.com/lukaszraczylo/harness-sync/internal/canonical"
-	"github.com/lukaszraczylo/harness-sync/internal/render"
 )
 
 const name = "crush"
@@ -49,6 +48,8 @@ func (a *Adapter) Detect() bool {
 }
 
 // Render produces the FileSet that applies the canonical bundle to crush.
+// crush.json is MERGED so user-managed keys ($schema, lsp, options, permissions) are preserved.
+// MCP key is "mcp" (not "mcpServers"); entries include a "type" field.
 func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 	fs := adapter.NewFileSet()
 	base := filepath.Join(a.home, ".config", "crush")
@@ -59,30 +60,28 @@ func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 		SymlinkTarget: filepath.Join(b.Root, "skills"),
 	})
 
-	cfg, err := renderConfig(b)
+	cfgPath := filepath.Join(base, "crush.json")
+	existing, _ := os.ReadFile(cfgPath)
+	overlay := map[string]any{
+		"providers":     common.BuildProviders(&b.Profile),
+		"default_model": b.Profile.Gateway.DefaultModel,
+	}
+	if mcp := common.BuildMCPMapStyled(&b.MCP, common.MCPCrushStyle); len(mcp) > 0 {
+		overlay["mcp"] = mcp
+	}
+	merged, err := common.MergeJSONKeys(existing, overlay)
 	if err != nil {
 		return nil, err
 	}
 	fs.Add(adapter.File{
-		Dest:    filepath.Join(base, "crush.json"),
+		Dest:    cfgPath,
 		Kind:    adapter.RenderedFile,
-		Content: cfg,
+		Content: merged,
 	})
 
 	return fs, nil
 }
 
-func renderConfig(b *canonical.Bundle) ([]byte, error) {
-	out := map[string]any{
-		"providers":     common.BuildProviders(&b.Profile),
-		"default_model": b.Profile.Gateway.DefaultModel,
-	}
-	if mcp := common.BuildMCPMap(&b.MCP); len(mcp) > 0 {
-		out["mcpServers"] = mcp
-	}
-	return render.JSON(out)
-}
-
 // Import reads crush config from home and returns a canonical ImportResult.
 func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
 	return importFrom(home)

internal/adapters/crush/crush_test.go

@@ -40,9 +40,71 @@ func TestCrushRenderProducesExpectedTargets(t *testing.T) {
 	// Parse rendered JSON to verify structure.
 	var parsed map[string]any
 	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
-	assert.NotNil(t, parsed) // at least it's valid JSON
+	assert.NotNil(t, parsed)
+	// Must use "default_model", not "model".
+	assert.Contains(t, parsed, "default_model")
+	// Must not write "mcpServers" — crush uses "mcp".
+	assert.NotContains(t, parsed, "mcpServers")
 }
 
+func TestCrushRenderMCPHasType(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Root: "/canon",
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "sonnet"},
+		},
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "fp", Command: "/bin/fp"},
+		}},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "crush", "crush.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	mcp := parsed["mcp"].(map[string]any)
+	fp := mcp["fp"].(map[string]any)
+	// Each MCP entry must have a "type" field.
+	assert.Equal(t, "stdio", fp["type"])
+}
+
+func TestCrushRenderMergesExistingKeys(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "crush")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	existing := map[string]any{
+		"$schema":     "https://crush.schema/v1",
+		"lsp":         []string{"gopls"},
+		"permissions": map[string]any{"allow": []string{"Bash"}},
+	}
+	body, _ := json.Marshal(existing)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "crush.json"), body, 0o600))
+
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(base, "crush.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	// Unrelated user keys preserved.
+	assert.Equal(t, "https://crush.schema/v1", parsed["$schema"])
+	assert.Contains(t, parsed, "lsp")
+	assert.Contains(t, parsed, "permissions")
+}
 func TestCrushImportRoundtrip(t *testing.T) {
 	home := t.TempDir()
 	base := filepath.Join(home, ".config", "crush")

internal/adapters/crush/import.go

@@ -9,7 +9,7 @@ import (
 
 func importFrom(home string) (*adapter.ImportResult, error) {
 	cfgPath := filepath.Join(home, ".config", "crush", "crush.json")
-	servers, err := common.ImportMCPFromJSONFile(cfgPath, "mcpServers")
+	servers, err := common.ImportMCPFromJSONFile(cfgPath, "mcp")
 	if err != nil {
 		return nil, err
 	}

internal/adapters/goose/goose.go

@@ -0,0 +1,135 @@
+// Package goose is the Goose (Block/square) harness adapter.
+//
+// Goose uses ~/.config/goose/config.yaml with a flat top-level structure.
+// MCP-equivalent servers go under "extensions" (not "mcp").
+// Model is split into GOOSE_PROVIDER + GOOSE_MODEL.
+//
+// Custom provider files (~/.config/goose/custom_providers/<name>.yaml) are
+// out of v1 scope. If a gateway URL is configured we set GOOSE_PROVIDER to
+// signal the intent; the user must hand-write the custom_providers file.
+package goose
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+const name = "goose"
+
+// Adapter implements adapter.Adapter for the Goose harness.
+type Adapter struct{ home string }
+
+// Option configures an Adapter.
+type Option func(*Adapter)
+
+// WithHome overrides the home directory (defaults to os.UserHomeDir).
+func WithHome(h string) Option { return func(a *Adapter) { a.home = h } }
+
+// New returns a new Adapter with the given options applied.
+func New(opts ...Option) *Adapter {
+	a := &Adapter{home: defaultHome()}
+	for _, o := range opts {
+		o(a)
+	}
+	return a
+}
+
+func defaultHome() string {
+	h, err := os.UserHomeDir()
+	if err != nil {
+		return ""
+	}
+	return h
+}
+
+// Name returns the harness identifier.
+func (a *Adapter) Name() string { return name }
+
+// Detect returns true when ~/.config/goose/ exists.
+func (a *Adapter) Detect() bool {
+	_, err := os.Stat(filepath.Join(a.home, ".config", "goose"))
+	return err == nil
+}
+
+// Render produces the FileSet that applies the canonical bundle to goose.
+// config.yaml is MERGED; only GOOSE_PROVIDER, GOOSE_MODEL, and the
+// managed extension entries are overlaid.
+func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
+	fs := adapter.NewFileSet()
+	cfgPath := filepath.Join(a.home, ".config", "goose", "config.yaml")
+
+	existing, _ := os.ReadFile(cfgPath)
+
+	provider, model := splitProviderModel(b.Profile.Gateway.DefaultModel)
+	if b.Profile.Gateway.URL != "" {
+		// Custom gateway: signal with provider name. User must create
+		// ~/.config/goose/custom_providers/harness-sync.yaml manually.
+		provider = "harness-sync"
+	}
+
+	overlay := map[string]any{
+		"GOOSE_PROVIDER": provider,
+		"GOOSE_MODEL":    model,
+	}
+
+	if len(b.MCP.Servers) > 0 {
+		extensions := buildExtensions(b.MCP.Servers)
+		overlay["extensions"] = extensions
+	}
+
+	merged, err := common.MergeYAMLKeys(existing, overlay)
+	if err != nil {
+		return nil, err
+	}
+
+	fs.Add(adapter.File{
+		Dest:    cfgPath,
+		Kind:    adapter.RenderedFile,
+		Content: merged,
+	})
+
+	return fs, nil
+}
+
+// buildExtensions converts canonical MCP servers to goose extension entries.
+func buildExtensions(servers []canonical.MCPServer) map[string]any {
+	out := map[string]any{}
+	for _, s := range servers {
+		e := map[string]any{
+			"enabled": true,
+			"type":    "stdio",
+		}
+		if s.Command != "" {
+			e["cmd"] = s.Command
+		}
+		args := s.Args
+		if args == nil {
+			args = []string{}
+		}
+		e["args"] = args
+		if len(s.Env) > 0 {
+			e["env"] = s.Env
+		}
+		out[s.Name] = e
+	}
+	return out
+}
+
+// splitProviderModel splits "provider/model" into its parts.
+// If no slash, provider is "anthropic" and the whole string is the model.
+func splitProviderModel(s string) (string, string) {
+	if idx := strings.IndexByte(s, '/'); idx >= 0 {
+		return s[:idx], s[idx+1:]
+	}
+	return "anthropic", s
+}
+
+// Import reads goose config from home and returns a canonical ImportResult.
+func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
+	return importFrom(home)
+}

internal/adapters/goose/goose_test.go

@@ -0,0 +1,145 @@
+package goose
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+func bundle() *canonical.Bundle {
+	return &canonical.Bundle{
+		Root: "/canon",
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "anthropic/claude-sonnet-4-6"},
+		},
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "filepuff", Command: "/bin/filepuff", Args: []string{"--serve"}},
+		}},
+	}
+}
+
+func TestGooseRenderProducesExpectedTargets(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	fs, err := ad.Render(bundle())
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "goose", "config.yaml")
+	require.Contains(t, seen, cfgDest)
+	assert.Equal(t, adapter.RenderedFile, seen[cfgDest].Kind)
+
+	var parsed map[string]any
+	require.NoError(t, yaml.Unmarshal(seen[cfgDest].Content, &parsed))
+	assert.Equal(t, "anthropic", parsed["GOOSE_PROVIDER"])
+	assert.Equal(t, "claude-sonnet-4-6", parsed["GOOSE_MODEL"])
+	assert.Contains(t, parsed, "extensions")
+
+	exts := parsed["extensions"].(map[string]any)
+	fp := exts["filepuff"].(map[string]any)
+	assert.Equal(t, "stdio", fp["type"])
+	assert.Equal(t, "/bin/filepuff", fp["cmd"])
+}
+
+func TestGooseRenderMergesExistingKeys(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "goose")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+	require.NoError(t, os.WriteFile(filepath.Join(base, "config.yaml"),
+		[]byte("GOOSE_TEMPERATURE: \"0.7\"\nGOOSE_PROVIDER: old\n"), 0o600))
+
+	ad := New(WithHome(home))
+	fs, err := ad.Render(bundle())
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	var parsed map[string]any
+	require.NoError(t, yaml.Unmarshal(seen[filepath.Join(base, "config.yaml")].Content, &parsed))
+	// Existing unrelated key preserved.
+	assert.Equal(t, "0.7", parsed["GOOSE_TEMPERATURE"])
+	// Provider updated.
+	assert.Equal(t, "anthropic", parsed["GOOSE_PROVIDER"])
+}
+
+func TestGooseRenderGatewayURL(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{URL: "https://gw", DefaultModel: "sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "goose", "config.yaml")
+	var parsed map[string]any
+	require.NoError(t, yaml.Unmarshal(seen[cfgDest].Content, &parsed))
+	// Custom gateway → provider is "harness-sync" (user must write custom_providers file).
+	assert.Equal(t, "harness-sync", parsed["GOOSE_PROVIDER"])
+}
+
+func TestGooseImport(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "goose")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	cfg := map[string]any{
+		"GOOSE_PROVIDER": "anthropic",
+		"GOOSE_MODEL":    "claude-sonnet-4-6",
+		"extensions": map[string]any{
+			"filepuff": map[string]any{
+				"type":    "stdio",
+				"cmd":     "/bin/filepuff",
+				"args":    []string{"--serve"},
+				"enabled": true,
+			},
+		},
+	}
+	body, err := yaml.Marshal(cfg)
+	require.NoError(t, err)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "config.yaml"), body, 0o600))
+
+	ad := New(WithHome(home))
+	res, err := ad.Import(home)
+	require.NoError(t, err)
+	require.NotNil(t, res)
+	require.Len(t, res.MCP, 1)
+	assert.Equal(t, "filepuff", res.MCP[0].Name)
+	assert.Equal(t, "/bin/filepuff", res.MCP[0].Command)
+}
+
+func TestGooseImportMissing(t *testing.T) {
+	ad := New(WithHome(t.TempDir()))
+	res, err := ad.Import(t.TempDir())
+	require.NoError(t, err)
+	assert.NotNil(t, res)
+	assert.Empty(t, res.MCP)
+}
+
+func TestSplitProviderModel(t *testing.T) {
+	t.Run("with slash", func(t *testing.T) {
+		p, m := splitProviderModel("anthropic/claude-sonnet-4-6")
+		assert.Equal(t, "anthropic", p)
+		assert.Equal(t, "claude-sonnet-4-6", m)
+	})
+	t.Run("no slash", func(t *testing.T) {
+		p, m := splitProviderModel("claude-sonnet")
+		assert.Equal(t, "anthropic", p)
+		assert.Equal(t, "claude-sonnet", m)
+	})
+}

internal/adapters/goose/import.go

@@ -0,0 +1,67 @@
+package goose
+
+import (
+	"os"
+	"path/filepath"
+
+	"gopkg.in/yaml.v3"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+func importFrom(home string) (*adapter.ImportResult, error) {
+	cfgPath := filepath.Join(home, ".config", "goose", "config.yaml")
+	body, err := os.ReadFile(cfgPath)
+	if os.IsNotExist(err) {
+		return &adapter.ImportResult{}, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	var raw map[string]any
+	if err := yaml.Unmarshal(body, &raw); err != nil {
+		return &adapter.ImportResult{}, nil
+	}
+
+	res := &adapter.ImportResult{}
+
+	// Reconstruct MCP servers from extensions entries with type: stdio.
+	if exts, ok := raw["extensions"]; ok {
+		if extMap, ok := exts.(map[string]any); ok {
+			for name, v := range extMap {
+				entry, ok := v.(map[string]any)
+				if !ok {
+					continue
+				}
+				t, _ := entry["type"].(string)
+				if t != "stdio" {
+					continue
+				}
+				s := canonical.MCPServer{Name: name}
+				if cmd, ok := entry["cmd"].(string); ok {
+					s.Command = cmd
+				}
+				if args, ok := entry["args"].([]any); ok {
+					for _, a := range args {
+						if str, ok := a.(string); ok {
+							s.Args = append(s.Args, str)
+						}
+					}
+				}
+				if envRaw, ok := entry["env"].(map[string]any); ok {
+					s.Env = make(map[string]string, len(envRaw))
+					for k, val := range envRaw {
+						if str, ok := val.(string); ok {
+							s.Env[k] = str
+						}
+					}
+				}
+				res.MCP = append(res.MCP, s)
+			}
+		}
+	}
+
+	return res, nil
+}

internal/adapters/kilo/kilo.go

@@ -8,7 +8,6 @@ import (
 	"github.com/lukaszraczylo/harness-sync/internal/adapter"
 	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
 	"github.com/lukaszraczylo/harness-sync/internal/canonical"
-	"github.com/lukaszraczylo/harness-sync/internal/render"
 )
 
 const name = "kilo"
@@ -51,6 +50,10 @@ func (a *Adapter) Detect() bool {
 }
 
 // Render produces the FileSet that applies the canonical bundle to kilo.
+// kilo.json is MERGED to preserve user-managed keys ($schema, small_model,
+// instructions, permission, compaction, watcher, formatter, skills).
+// Key "model" is a plain string; MCP uses "mcp" with local/remote type entries.
+// No "providers" key — kilo has no such concept.
 func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 	fs := adapter.NewFileSet()
 	base := filepath.Join(a.home, ".config", "kilo")
@@ -61,30 +64,27 @@ func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 		SymlinkTarget: filepath.Join(b.Root, "agents"),
 	})
 
-	cfg, err := renderConfig(b)
+	cfgPath := filepath.Join(base, "kilo.json")
+	existing, _ := os.ReadFile(cfgPath)
+	overlay := map[string]any{
+		"model": b.Profile.Gateway.DefaultModel,
+	}
+	if mcp := common.BuildMCPMapStyled(&b.MCP, common.MCPOpencodeStyle); len(mcp) > 0 {
+		overlay["mcp"] = mcp
+	}
+	merged, err := common.MergeJSONKeys(existing, overlay)
 	if err != nil {
 		return nil, err
 	}
 	fs.Add(adapter.File{
-		Dest:    filepath.Join(base, "kilo.json"),
+		Dest:    cfgPath,
 		Kind:    adapter.RenderedFile,
-		Content: cfg,
+		Content: merged,
 	})
 
 	return fs, nil
 }
 
-func renderConfig(b *canonical.Bundle) ([]byte, error) {
-	out := map[string]any{
-		"model":     b.Profile.Gateway.DefaultModel,
-		"providers": common.BuildProviders(&b.Profile),
-	}
-	if mcp := common.BuildMCPMap(&b.MCP); len(mcp) > 0 {
-		out["mcp"] = mcp
-	}
-	return render.JSON(out)
-}
-
 // Import reads kilo config from home and returns a canonical ImportResult.
 func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
 	return importFrom(home)

internal/adapters/kilo/kilo_test.go

@@ -46,8 +46,50 @@ func TestKiloRender(t *testing.T) {
 	assert.Contains(t, parsed, "mcp")
 	assert.NotContains(t, parsed, "default_model")
 	assert.NotContains(t, parsed, "mcpServers")
+	// kilo has no "providers" concept.
+	assert.NotContains(t, parsed, "providers")
+	// MCP entries use local/remote type (MCPOpencodeStyle).
+	mcp := parsed["mcp"].(map[string]any)
+	fp := mcp["filepuff"].(map[string]any)
+	assert.Equal(t, "local", fp["type"])
+	cmd, _ := fp["command"].([]any)
+	assert.Equal(t, "/bin/filepuff", cmd[0])
 }
 
+func TestKiloRenderMergesExistingKeys(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "kilo")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	existing := map[string]any{
+		"$schema":     "https://kilo.schema/v1",
+		"small_model": "claude-haiku",
+		"compaction":  map[string]any{"enabled": true},
+	}
+	body, _ := json.Marshal(existing)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "kilo.json"), body, 0o600))
+
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(base, "kilo.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	// User keys preserved.
+	assert.Equal(t, "https://kilo.schema/v1", parsed["$schema"])
+	assert.Equal(t, "claude-haiku", parsed["small_model"])
+	assert.Contains(t, parsed, "compaction")
+	// Model updated.
+	assert.Equal(t, "sonnet", parsed["model"])
+}
 func TestKiloImport(t *testing.T) {
 	home := t.TempDir()
 	base := filepath.Join(home, ".config", "kilo")

internal/adapters/opencode/import.go

@@ -16,7 +16,7 @@ func importFrom(home string) (*adapter.ImportResult, error) {
 		return nil, err
 	}
 	if cfgBody != "" {
-		mcpServers, mcpErr := common.ParseMCPFromJSON([]byte(cfgBody), "mcpServers")
+		mcpServers, mcpErr := common.ParseMCPFromJSON([]byte(cfgBody), "mcp")
 		if mcpErr != nil {
 			return nil, mcpErr
 		}

internal/adapters/opencode/opencode.go

@@ -8,7 +8,6 @@ import (
 	"github.com/lukaszraczylo/harness-sync/internal/adapter"
 	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
 	"github.com/lukaszraczylo/harness-sync/internal/canonical"
-	"github.com/lukaszraczylo/harness-sync/internal/render"
 )
 
 const name = "opencode"
@@ -49,18 +48,30 @@ func (a *Adapter) Detect() bool {
 }
 
 // Render produces the FileSet that applies the canonical bundle to opencode.
+// opencode.jsonc is MERGED to preserve user-managed keys ($schema, agent,
+// instructions, …). Correct keys: "provider" (singular, map), "model" (string),
+// "mcp" (map with type: local|remote entries).
 func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 	fs := adapter.NewFileSet()
 	base := filepath.Join(a.home, ".config", "opencode")
 
-	cfg, err := renderConfig(b)
+	cfgPath := filepath.Join(base, "opencode.jsonc")
+	existing, _ := os.ReadFile(cfgPath)
+	overlay := map[string]any{
+		"provider": common.ProvidersAsMap(&b.Profile),
+		"model":    b.Profile.Gateway.DefaultModel,
+	}
+	if mcp := common.BuildMCPMapStyled(&b.MCP, common.MCPOpencodeStyle); len(mcp) > 0 {
+		overlay["mcp"] = mcp
+	}
+	merged, err := common.MergeJSONKeys(existing, overlay)
 	if err != nil {
 		return nil, err
 	}
 	fs.Add(adapter.File{
-		Dest:    filepath.Join(base, "opencode.jsonc"),
+		Dest:    cfgPath,
 		Kind:    adapter.RenderedFile,
-		Content: cfg,
+		Content: merged,
 	})
 
 	instructions := b.Instructions.Global
@@ -76,17 +87,6 @@ func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
 	return fs, nil
 }
 
-func renderConfig(b *canonical.Bundle) ([]byte, error) {
-	out := map[string]any{
-		"providers":     common.BuildProviders(&b.Profile),
-		"default_model": b.Profile.Gateway.DefaultModel,
-	}
-	if mcp := common.BuildMCPMap(&b.MCP); len(mcp) > 0 {
-		out["mcpServers"] = mcp
-	}
-	return render.JSON(out)
-}
-
 // Import reads opencode config from home and returns a canonical ImportResult.
 func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
 	return importFrom(home)

internal/adapters/opencode/opencode_test.go

@@ -34,12 +34,81 @@ func TestOpencodeRender(t *testing.T) {
 	assert.Equal(t, adapter.RenderedFile, seen[cfgDest].Kind)
 	var parsed map[string]any
 	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	// Correct key is "provider" (singular map), not "providers" (slice).
+	assert.Contains(t, parsed, "provider")
+	assert.NotContains(t, parsed, "providers")
+	// Correct key is "model", not "default_model".
+	assert.Contains(t, parsed, "model")
+	assert.NotContains(t, parsed, "default_model")
+	// No "mcpServers" — opencode uses "mcp".
+	assert.NotContains(t, parsed, "mcpServers")
 
 	agentsDest := filepath.Join(home, ".config", "opencode", "AGENTS.md")
 	assert.Equal(t, adapter.RenderedFile, seen[agentsDest].Kind)
 	assert.Contains(t, string(seen[agentsDest].Content), "# global")
 }
 
+func TestOpencodeRenderWithMCP(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "sonnet"},
+		},
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "fp", Command: "/bin/fp"},
+		}},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "opencode", "opencode.jsonc")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	mcp := parsed["mcp"].(map[string]any)
+	fp := mcp["fp"].(map[string]any)
+	// MCPOpencodeStyle: type local, command as array, enabled true.
+	assert.Equal(t, "local", fp["type"])
+	assert.Equal(t, true, fp["enabled"])
+	cmd, _ := fp["command"].([]any)
+	assert.Equal(t, "/bin/fp", cmd[0])
+}
+
+func TestOpencodeRenderMergesExistingKeys(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "opencode")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	existing := map[string]any{
+		"$schema": "https://opencode.schema/v1",
+		"agent":   map[string]any{"maxTokens": 8192},
+	}
+	body, _ := json.Marshal(existing)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "opencode.jsonc"), body, 0o600))
+
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(base, "opencode.jsonc")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	// User keys preserved.
+	assert.Equal(t, "https://opencode.schema/v1", parsed["$schema"])
+	assert.Contains(t, parsed, "agent")
+	// Managed keys overlaid.
+	assert.Contains(t, parsed, "model")
+	assert.Contains(t, parsed, "provider")
+}
 func TestOpencodeImportStripsComments(t *testing.T) {
 	home := t.TempDir()
 	base := filepath.Join(home, ".config", "opencode")

internal/adapters/zed/import.go

@@ -0,0 +1,19 @@
+package zed
+
+import (
+	"path/filepath"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
+)
+
+func importFrom(home string) (*adapter.ImportResult, error) {
+	cfgPath := filepath.Join(home, ".config", "zed", "settings.json")
+	// context_servers entries use source:"custom" for stdio; the MCP command
+	// field maps directly to canonical MCPServer.Command.
+	servers, err := common.ImportMCPFromJSONFile(cfgPath, "context_servers")
+	if err != nil {
+		return nil, err
+	}
+	return &adapter.ImportResult{MCP: servers}, nil
+}

internal/adapters/zed/zed.go

@@ -0,0 +1,102 @@
+// Package zed is the Zed editor harness adapter.
+//
+// Zed uses ~/.config/zed/settings.json with many user-managed keys.
+// We MERGE only "agent" and "context_servers"; all other keys are preserved.
+// MCP servers become context_servers entries with source: "custom".
+package zed
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/adapter/common"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+const name = "zed"
+
+// Adapter implements adapter.Adapter for the Zed harness.
+type Adapter struct{ home string }
+
+// Option configures an Adapter.
+type Option func(*Adapter)
+
+// WithHome overrides the home directory (defaults to os.UserHomeDir).
+func WithHome(h string) Option { return func(a *Adapter) { a.home = h } }
+
+// New returns a new Adapter with the given options applied.
+func New(opts ...Option) *Adapter {
+	a := &Adapter{home: defaultHome()}
+	for _, o := range opts {
+		o(a)
+	}
+	return a
+}
+
+func defaultHome() string {
+	h, err := os.UserHomeDir()
+	if err != nil {
+		return ""
+	}
+	return h
+}
+
+// Name returns the harness identifier.
+func (a *Adapter) Name() string { return name }
+
+// Detect returns true when ~/.config/zed/ exists.
+func (a *Adapter) Detect() bool {
+	_, err := os.Stat(filepath.Join(a.home, ".config", "zed"))
+	return err == nil
+}
+
+// Render produces the FileSet that applies the canonical bundle to Zed.
+// settings.json is MERGED to preserve all user-managed Zed configuration.
+// Only "agent" (default_model) and "context_servers" (MCP) are overlaid.
+func (a *Adapter) Render(b *canonical.Bundle) (*adapter.FileSet, error) {
+	fs := adapter.NewFileSet()
+	cfgPath := filepath.Join(a.home, ".config", "zed", "settings.json")
+	existing, _ := os.ReadFile(cfgPath)
+
+	overlay := map[string]any{
+		"context_servers": common.BuildMCPMapStyled(&b.MCP, common.MCPZedStyle),
+	}
+
+	if dm := b.Profile.Gateway.DefaultModel; dm != "" {
+		provider, model := splitProviderModel(dm)
+		overlay["agent"] = map[string]any{
+			"default_model": map[string]any{
+				"provider": provider,
+				"model":    model,
+			},
+		}
+	}
+
+	merged, err := common.MergeJSONKeys(existing, overlay)
+	if err != nil {
+		return nil, err
+	}
+	fs.Add(adapter.File{
+		Dest:    cfgPath,
+		Kind:    adapter.RenderedFile,
+		Content: merged,
+	})
+
+	return fs, nil
+}
+
+// Import reads context_servers from Zed settings.json back to MCP servers.
+func (a *Adapter) Import(home string) (*adapter.ImportResult, error) {
+	return importFrom(home)
+}
+
+// splitProviderModel splits "provider/model" at the first slash.
+// If no slash, provider is "anthropic".
+func splitProviderModel(s string) (string, string) {
+	if idx := strings.IndexByte(s, '/'); idx >= 0 {
+		return s[:idx], s[idx+1:]
+	}
+	return "anthropic", s
+}

internal/adapters/zed/zed_test.go

@@ -0,0 +1,165 @@
+package zed
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/lukaszraczylo/harness-sync/internal/adapter"
+	"github.com/lukaszraczylo/harness-sync/internal/canonical"
+)
+
+func bundle() *canonical.Bundle {
+	return &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "anthropic/claude-sonnet-4-6"},
+		},
+		MCP: canonical.MCPRegistry{Servers: []canonical.MCPServer{
+			{Name: "filepuff", Command: "/bin/filepuff", Args: []string{"--serve"}},
+		}},
+	}
+}
+
+func TestZedRenderProducesExpectedTargets(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	fs, err := ad.Render(bundle())
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "zed", "settings.json")
+	require.Contains(t, seen, cfgDest)
+	assert.Equal(t, adapter.RenderedFile, seen[cfgDest].Kind)
+
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+
+	// Agent default_model is an object.
+	agent := parsed["agent"].(map[string]any)
+	dm := agent["default_model"].(map[string]any)
+	assert.Equal(t, "anthropic", dm["provider"])
+	assert.Equal(t, "claude-sonnet-4-6", dm["model"])
+
+	// context_servers.
+	cs := parsed["context_servers"].(map[string]any)
+	fp := cs["filepuff"].(map[string]any)
+	assert.Equal(t, true, fp["enabled"])
+	assert.Equal(t, "custom", fp["source"])
+	assert.Equal(t, "/bin/filepuff", fp["command"])
+}
+
+func TestZedRenderMergesExistingKeys(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "zed")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	// Existing settings with unrelated user config.
+	existing := map[string]any{
+		"theme":     "One Dark",
+		"font_size": 16,
+		"vim_mode":  true,
+	}
+	body, _ := json.Marshal(existing)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "settings.json"), body, 0o600))
+
+	ad := New(WithHome(home))
+	fs, err := ad.Render(bundle())
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(base, "settings.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+
+	// Unrelated keys preserved.
+	assert.Equal(t, "One Dark", parsed["theme"])
+	assert.Equal(t, float64(16), parsed["font_size"])
+	assert.Equal(t, true, parsed["vim_mode"])
+	// Managed keys present.
+	assert.Contains(t, parsed, "agent")
+	assert.Contains(t, parsed, "context_servers")
+}
+
+func TestZedRenderNoMCP(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	b := &canonical.Bundle{
+		Profile: canonical.Profile{
+			Gateway: canonical.Gateway{DefaultModel: "anthropic/sonnet"},
+		},
+	}
+	fs, err := ad.Render(b)
+	require.NoError(t, err)
+
+	seen := map[string]adapter.File{}
+	fs.ForEach(func(f adapter.File) { seen[f.Dest] = f })
+
+	cfgDest := filepath.Join(home, ".config", "zed", "settings.json")
+	var parsed map[string]any
+	require.NoError(t, json.Unmarshal(seen[cfgDest].Content, &parsed))
+	// context_servers key present but empty map.
+	cs, ok := parsed["context_servers"]
+	assert.True(t, ok)
+	assert.Empty(t, cs)
+}
+
+func TestZedImport(t *testing.T) {
+	home := t.TempDir()
+	base := filepath.Join(home, ".config", "zed")
+	require.NoError(t, os.MkdirAll(base, 0o750))
+
+	settings := map[string]any{
+		"context_servers": map[string]any{
+			"filepuff": map[string]any{
+				"enabled": true,
+				"source":  "custom",
+				"command": "/bin/filepuff",
+				"args":    []string{"--serve"},
+			},
+		},
+	}
+	body, _ := json.Marshal(settings)
+	require.NoError(t, os.WriteFile(filepath.Join(base, "settings.json"), body, 0o600))
+
+	ad := New(WithHome(home))
+	res, err := ad.Import(home)
+	require.NoError(t, err)
+	require.NotNil(t, res)
+	require.Len(t, res.MCP, 1)
+	assert.Equal(t, "filepuff", res.MCP[0].Name)
+	assert.Equal(t, "/bin/filepuff", res.MCP[0].Command)
+}
+
+func TestZedImportMissing(t *testing.T) {
+	ad := New(WithHome(t.TempDir()))
+	res, err := ad.Import(t.TempDir())
+	require.NoError(t, err)
+	assert.NotNil(t, res)
+}
+
+func TestZedDetect(t *testing.T) {
+	home := t.TempDir()
+	ad := New(WithHome(home))
+	assert.False(t, ad.Detect())
+}
+
+func TestSplitProviderModel(t *testing.T) {
+	t.Run("with slash", func(t *testing.T) {
+		p, m := splitProviderModel("anthropic/claude-sonnet-4-6")
+		assert.Equal(t, "anthropic", p)
+		assert.Equal(t, "claude-sonnet-4-6", m)
+	})
+	t.Run("no slash", func(t *testing.T) {
+		p, m := splitProviderModel("claude-sonnet")
+		assert.Equal(t, "anthropic", p)
+		assert.Equal(t, "claude-sonnet", m)
+	})
+}