agent: a catalog sync or a model pick keeps the keys a user or another tool added to magpie's provider block (Pi's providers.magpie.compat.sendSessionAffinityHeaders from pi-cache-optimizer) instead of writing the block whole (#1103)

syncJSON and Pi's writeMagpie set providers.magpie to a freshly built
object, so a key magpie doesn't write there was dropped on every sync.
theirsKept now merges magpie's block into what the file holds: keys magpie
writes are its own, objects in both are merged key by key, and anything
else (compat, an options key, Crush's extra_headers) stays. The model list
is still magpie's whole, so a model gone from the catalog leaves it, and a
sync with nothing new writes nothing.

The same goes for every agent that writes the block whole: Pi and OmO,
Aside, Pencil, OpenCode (and the agents built on it), OpenChamber, Crush
and Command Code.

Verified: TestPiKeepsTheirKeysInMagpiesProvider (the reporter's
compat.sendSessionAffinityHeaders: true in Pi's models.json, through
SyncCatalog and a pick) and TestOpenCodeAndCrushKeepTheirKeysInMagpiesProvider
fail without the change ("compat.sendSessionAffinityHeaders dropped by the
sync", "opencode sync") and pass with it. go test -race ./internal/agent
and go vet ./... pass in a sandbox HOME.

internal/agent/agents.go

@@ -578,7 +578,7 @@ func openCodeLike(at place, id, name, icon, bin, dir, auth string, ua []string,
 			break
 		}
 	}
-	provider := func() any { return magpieProviderJSONAt("opencode", id, at.gw()) }
+	provider := theirsKept(path, "provider."+magpieID, func() any { return magpieProviderJSONAt("opencode", id, at.gw()) }, "models")
 	opts := func(key string) func(map[string]string) []Option {
 		return func(cur map[string]string) []Option {
 			return append(ownOptions(auth, cur[key]), viaMagpie(id, magpieID+"/")...)
@@ -654,7 +654,8 @@ func openCodeRefAt(at place, path, id, v string) (string, error) {
 	if own := ownGatewayProvider(path, ref, at.v1()); own != "" {
 		return own + "/" + ref, nil
 	}
-	return v, edit.SetJSON(path, edit.KV{Path: "provider." + magpieID, Value: magpieProviderJSONAt("opencode", id, at.gw())})
+	provider := theirsKept(path, "provider."+magpieID, func() any { return magpieProviderJSONAt("opencode", id, at.gw()) }, "models")
+	return v, edit.SetJSON(path, edit.KV{Path: "provider." + magpieID, Value: provider()})
 }
 
 // ownGatewayProvider is the provider in an OpenCode config, other than
@@ -797,8 +798,9 @@ func piLike(at place, id, name, dir string) *Agent {
 	pair := pairSet(set, "defaultProvider", "defaultModel")
 	// the model a new session starts on, as the model field shows it
 	startup := func() string { return piStartup(path, pairGet(get, "defaultProvider", "defaultModel")()) }
+	block := theirsKept(modelsPath, "providers."+magpieID, func() any { return magpieProviderJSONAt("pi", id, at.gw()) }, "models")
 	writeMagpie := func() error {
-		return edit.SetJSON(modelsPath, edit.KV{Path: "providers." + magpieID, Value: magpieProviderJSONAt("pi", id, at.gw())})
+		return edit.SetJSON(modelsPath, edit.KV{Path: "providers." + magpieID, Value: block()})
 	}
 	return &Agent{
 		ID: id, Name: name, Icon: id, Bin: id, Dir: dir, Path: path, Spelled: prefixed,
@@ -810,7 +812,7 @@ func piLike(at place, id, name, dir string) *Agent {
 				"baseUrl", at.v1(), "apiKey", at.gwKey())
 		},
 		Sync: func() error {
-			return syncJSON(modelsPath, "providers."+magpieID, func() any { return magpieProviderJSONAt("pi", id, at.gw()) })
+			return syncJSON(modelsPath, "providers."+magpieID, block)
 		},
 		Fields: []Field{
 			{
@@ -1078,7 +1080,7 @@ func crushIn(at place) *Agent {
 // crushAt is Crush with its config at path and its data file at data,
 // reaching the gateway as at does.
 func crushAt(at place, path, data string) *Agent {
-	provider := func() any { return magpieProviderJSONAt("crush", "crush", at.gw()) }
+	provider := theirsKept(path, "providers."+magpieID, func() any { return magpieProviderJSONAt("crush", "crush", at.gw()) }, "models")
 	get := func(k string) (string, bool) { return edit.GetJSON(path, k) }
 	set := func(kvs ...edit.KV) error { return edit.SetJSON(path, kvs...) }
 	pick := func(k string) (string, bool) {

internal/agent/aside_native.go

@@ -328,9 +328,9 @@ func (c *asideConnection) connectLocked() error {
 		return fmt.Errorf("%s", detail)
 	}
 	if status == "connected" {
-		return syncJSON(c.models, "providers.magpie", c.block)
+		return syncJSON(c.models, "providers.magpie", c.kept())
 	}
-	return edit.SetJSON(c.models, edit.KV{Path: "providers.magpie", Value: c.block()})
+	return edit.SetJSON(c.models, edit.KV{Path: "providers.magpie", Value: c.kept()()})
 }
 
 func (c *asideConnection) sync() error {
@@ -340,7 +340,13 @@ func (c *asideConnection) sync() error {
 	if status != "connected" {
 		return nil
 	}
-	return syncJSON(c.models, "providers.magpie", c.block)
+	return syncJSON(c.models, "providers.magpie", c.kept())
+}
+
+// kept is the block with what else Aside's providers.magpie holds kept
+// (theirsKept).
+func (c *asideConnection) kept() func() any {
+	return theirsKept(c.models, "providers.magpie", c.block, "models")
 }
 
 func (c *asideConnection) state() NativeState {

internal/agent/commandcode.go

@@ -43,7 +43,7 @@ func commandCodeIn(at place) *Agent {
 		UA:  []string{"command-code", "commandcode"},
 		Bin: "command-code", Dir: dir, Path: path,
 		Sync: func() error {
-			return syncJSON(providers, "provider."+magpieID, func() any { return ccProviderJSON() })
+			return syncJSON(providers, "provider."+magpieID, theirsKept(providers, "provider."+magpieID, ccProviderJSON, "models"))
 		},
 		Notice: func() string {
 			notes := []string{"Command Code wants its own sign-in (cmd login) even for models through magpie."}
@@ -77,7 +77,7 @@ func commandCodeIn(at place) *Agent {
 					return dropMagpie()
 				}
 				if ref, ok := strings.CutPrefix(v, magpieID+"/"); ok && isMagpie(ref) {
-					if err := edit.SetJSON(providers, edit.KV{Path: "provider." + magpieID, Value: ccProviderJSON()}); err != nil {
+					if err := edit.SetJSON(providers, edit.KV{Path: "provider." + magpieID, Value: theirsKept(providers, "provider."+magpieID, ccProviderJSON, "models")()}); err != nil {
 						return err
 					}
 					return edit.SetJSON(path, edit.KV{Path: "model", Value: v}, edit.KV{Path: "modelProvider", Value: magpieID})

internal/agent/openchamber.go

@@ -165,7 +165,7 @@ func openChamber(home, cfg string) *Agent {
 	oc := opencode(home, cfg)
 	ocPath := oc.Path
 	auth := filepath.Join(home, ".local", "share", "opencode", "auth.json")
-	provider := func() any { return magpieProviderJSONFor("opencode", "opencode") }
+	provider := theirsKept(ocPath, "provider."+magpieID, func() any { return magpieProviderJSONFor("opencode", "opencode") }, "models")
 	opts := func(key string) func(map[string]string) []Option {
 		return func(cur map[string]string) []Option {
 			return append(ownOptions(auth, cur[key]), viaMagpie("opencode", magpieID+"/")...)

internal/agent/pencil.go

@@ -50,7 +50,7 @@ func pencil(home string) *Agent {
 			return ""
 		},
 		Sync: func() error {
-			return syncJSON(path, key, func() any { return pencilProviderJSON(gateway.URL()) })
+			return syncJSON(path, key, theirsKept(path, key, func() any { return pencilProviderJSON(gateway.URL()) }, "models"))
 		},
 		Fields: []Field{{
 			Key: "provider", Label: "provider",
@@ -64,7 +64,7 @@ func pencil(home string) *Agent {
 				if v == "" {
 					return edit.DelJSON(path, key)
 				}
-				return edit.SetJSON(path, edit.KV{Path: key, Value: pencilProviderJSON(gateway.URL())})
+				return edit.SetJSON(path, edit.KV{Path: key, Value: theirsKept(path, key, func() any { return pencilProviderJSON(gateway.URL()) }, "models")()})
 			},
 			Options: func(map[string]string) []Option {
 				return []Option{{Value: magpieID, Label: "magpie", Icon: "magpie", Note: "every magpie model in Pencil's model picker"}}

internal/agent/sync.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"io"
 	"reflect"
+	"slices"
 	"strings"
 	"sync"
 
@@ -76,6 +77,56 @@ func syncJSON(path, key string, value func() any) error {
 	return edit.SetJSON(path, edit.KV{Path: key, Value: v})
 }
 
+// theirsKept is value, magpie's provider block for the agent, with what
+// else the block at key of the JSON file holds kept: a key magpie doesn't
+// write there, at any depth, is the user's or another tool's (Pi's
+// providers.magpie.compat.sendSessionAffinityHeaders, which
+// pi-cache-optimizer adds, #1103) and stays. The keys named in whole (the
+// model list) are magpie's alone, so a model gone from the catalog leaves
+// the agent's list.
+func theirsKept(path, key string, value func() any, whole ...string) func() any {
+	return func() any {
+		v := value()
+		cur, ok := edit.GetJSON(path, key)
+		if !ok {
+			return v
+		}
+		var have, want map[string]json.RawMessage
+		b, err := json.Marshal(v)
+		if err != nil || json.Unmarshal([]byte(cur), &have) != nil || have == nil || json.Unmarshal(b, &want) != nil || want == nil {
+			return v
+		}
+		return mergeTheirs(have, want, whole)
+	}
+}
+
+// mergeTheirs is want with each key of have that want lacks, objects in
+// both merged alike; a key named in whole is want's as it is.
+func mergeTheirs(have, want map[string]json.RawMessage, whole []string) map[string]json.RawMessage {
+	out := make(map[string]json.RawMessage, len(have)+len(want))
+	for k, w := range want {
+		out[k] = w
+	}
+	for k, h := range have {
+		w, ok := want[k]
+		if !ok {
+			out[k] = h
+			continue
+		}
+		if slices.Contains(whole, k) {
+			continue
+		}
+		var hm, wm map[string]json.RawMessage
+		if json.Unmarshal(h, &hm) != nil || hm == nil || json.Unmarshal(w, &wm) != nil || wm == nil {
+			continue
+		}
+		if b, err := json.Marshal(mergeTheirs(hm, wm, nil)); err == nil {
+			out[k] = b
+		}
+	}
+	return out
+}
+
 // syncJSONInOrder is syncJSON for a block whose keys' order the agent reads
 // (OpenCode lists a model's variants in theirs): one that says the same in
 // another order is rewritten too, as an older magpie wrote the variants

internal/agent/sync_keep_test.go

@@ -0,0 +1,120 @@
+package agent
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// providerAt is the object at providers.<id> (or provider.<id>) of a JSON
+// file, decoded.
+func providerAt(t *testing.T, path, top string) map[string]any {
+	t.Helper()
+	var f map[string]json.RawMessage
+	var ps map[string]map[string]any
+	if err := json.Unmarshal([]byte(readFile(path)), &f); err != nil || json.Unmarshal(f[top], &ps) != nil {
+		t.Fatalf("%s: %v\n%s", path, err, readFile(path))
+	}
+	return ps[magpieID]
+}
+
+// #1103: pi-cache-optimizer's /cache-optimizer fix adds
+// providers.magpie.compat.sendSessionAffinityHeaders to Pi's models.json.
+// A catalog sync, and a pick of a magpie model in Pi, keep it; the model
+// list is still magpie's, so a model gone from the catalog leaves it, and
+// a sync with nothing new writes nothing.
+func TestPiKeepsTheirKeysInMagpiesProvider(t *testing.T) {
+	home := syncHome(t)
+	piModels := filepath.Join(home, ".pi", "agent", "models.json")
+	// the block as magpie wrote it, with the optimizer's key added
+	writeFile(t, piModels, `{
+  "providers": {
+    "magpie": {
+      "api": "openai-completions",
+      "apiKey": "magpie",
+      "baseUrl": "http://127.0.0.1:3425/v1",
+      "compat": {
+        "sendSessionAffinityHeaders": true
+      },
+      "models": [
+        {
+          "id": "gone/old-model",
+          "name": "Old"
+        }
+      ],
+      "name": "magpie"
+    }
+  }
+}
+`)
+	SyncCatalog()
+	p := providerAt(t, piModels, "providers")
+	compat, _ := p["compat"].(map[string]any)
+	if compat["sendSessionAffinityHeaders"] != true {
+		t.Fatalf("compat.sendSessionAffinityHeaders dropped by the sync:\n%s", readFile(piModels))
+	}
+	ms, _ := json.Marshal(p["models"])
+	if strings.Contains(string(ms), "gone/old-model") || !strings.Contains(string(ms), "relay/glm-4.6") {
+		t.Fatalf("models not magpie's list: %s", ms)
+	}
+
+	// synced already: the next sync writes nothing
+	st, _ := os.Stat(piModels)
+	old := st.ModTime().Add(-1e12)
+	os.Chtimes(piModels, old, old)
+	SyncCatalog()
+	if now, _ := os.Stat(piModels); !now.ModTime().Equal(old) {
+		t.Errorf("models.json rewritten though nothing changed:\n%s", readFile(piModels))
+	}
+
+	// picking a magpie model in Pi writes the block too
+	if err := pi(home).Fields[0].Set("magpie/relay/glm-4.6"); err != nil {
+		t.Fatal(err)
+	}
+	compat, _ = providerAt(t, piModels, "providers")["compat"].(map[string]any)
+	if compat["sendSessionAffinityHeaders"] != true {
+		t.Fatalf("compat.sendSessionAffinityHeaders dropped by a pick:\n%s", readFile(piModels))
+	}
+}
+
+// The same for OpenCode's provider.magpie (an options key of the user's
+// own) and Crush's providers.magpie.
+func TestOpenCodeAndCrushKeepTheirKeysInMagpiesProvider(t *testing.T) {
+	home := syncHome(t)
+	cfg := filepath.Join(home, ".config", "opencode", "opencode.json")
+	writeFile(t, cfg, `{"model":"magpie/relay/glm-4.6","provider":{"magpie":{"name":"magpie","npm":"@ai-sdk/openai-compatible","options":{"baseURL":"http://127.0.0.1:3425/v1","apiKey":"magpie","setCacheKey":true},"models":{"gone/old-model":{"name":"Old"}}}}}`)
+	oc := opencode(home, filepath.Join(home, ".config"))
+	if err := oc.Sync(); err != nil {
+		t.Fatal(err)
+	}
+	p := providerAt(t, cfg, "provider")
+	opts, _ := p["options"].(map[string]any)
+	ms, _ := p["models"].(map[string]any)
+	if opts["setCacheKey"] != true || ms["gone/old-model"] != nil || ms["relay/glm-4.6"] == nil {
+		t.Fatalf("opencode sync:\n%s", readFile(cfg))
+	}
+	if err := oc.Fields[0].Set("magpie/relay/glm-4.6"); err != nil {
+		t.Fatal(err)
+	}
+	if opts, _ := providerAt(t, cfg, "provider")["options"].(map[string]any); opts["setCacheKey"] != true {
+		t.Fatalf("opencode pick:\n%s", readFile(cfg))
+	}
+
+	cr := filepath.Join(home, ".config", "crush", "crush.json")
+	writeFile(t, cr, `{"providers":{"magpie":{"type":"openai","name":"magpie","base_url":"http://127.0.0.1:3425/v1","api_key":"magpie","extra_headers":{"X-Mine":"1"},"models":[]}}}`)
+	c := crushAt(here(home), cr, filepath.Join(home, ".local", "share", "crush", "crush.json"))
+	if err := c.Sync(); err != nil {
+		t.Fatal(err)
+	}
+	if h, _ := providerAt(t, cr, "providers")["extra_headers"].(map[string]any); h["X-Mine"] != "1" {
+		t.Fatalf("crush sync:\n%s", readFile(cr))
+	}
+	if err := c.Fields[0].Set("magpie/relay/glm-4.6"); err != nil {
+		t.Fatal(err)
+	}
+	if h, _ := providerAt(t, cr, "providers")["extra_headers"].(map[string]any); h["X-Mine"] != "1" {
+		t.Fatalf("crush pick:\n%s", readFile(cr))
+	}
+}