cmd/mavend/mail.go

@@ -27,7 +27,6 @@ import (
 	"github.com/kami/maven/internal/config"
 	"github.com/kami/maven/internal/email"
 	"github.com/kami/maven/internal/ipc"
-	"github.com/kami/maven/internal/llm"
 	"github.com/kami/maven/internal/phraser"
 	"github.com/kami/maven/internal/store"
 )
@@ -66,7 +65,7 @@ func newMailIntake(st *store.Store, phr phraser.Phraser, cfg *config.Config) *ma
 	if timeout <= 0 {
 		timeout = config.DefaultEmailTimeout
 	}
-	ex := email.NewExtractor(llm.New(lp.BaseURL(), timeout), cfg.Email.MaxTasks, contextBlockFn(cfg, time.Now))
+	ex := email.NewExtractor(llmClientFor(lp, timeout), cfg.Email.MaxTasks, contextBlockFn(cfg, time.Now))
 	log.Printf("mail intake: enabled (max %d candidates per message, timeout %s)", cfg.Email.MaxTasks, timeout)
 	return &mailIntake{st: st, ex: ex, timeout: timeout, now: time.Now}
 }

cmd/mavend/main.go

@@ -329,6 +329,7 @@ func run(args []string) error {
 	// ipc.MethodIngestMail reports ErrUnknownMethod.
 	if !locked {
 		wireMailIntake(srv, st, phr, cfg)
+		wireModelSwap(srv, phr, cfg)
 	}
 
 	// WrapKeyFn — wraps the env key with a passkey credential public key and
@@ -471,6 +472,7 @@ func run(args []string) error {
 			srv.SetAPI(newAPI)
 			srv.Check = (&auth.Gate{Enrollment: auth.NewFloorEnrollment(), Session: passkeySess}).Check
 			wireMailIntake(srv, st, phr, cfg)
+			wireModelSwap(srv, phr, cfg)
 
 			// Start voice server.
 			if voiceW != nil {

cmd/mavend/memoryeval.go

@@ -16,7 +16,6 @@ import (
 	"time"
 
 	"github.com/kami/maven/internal/config"
-	"github.com/kami/maven/internal/llm"
 	"github.com/kami/maven/internal/memeval"
 	"github.com/kami/maven/internal/phraser"
 	"github.com/kami/maven/internal/store"
@@ -50,7 +49,7 @@ func newMemoryEvalWorker(st *store.Store, phr phraser.Phraser, cfg *config.Confi
 	}
 	// A generous per-request timeout: this is a long prompt to a Thinking model
 	// and nobody is waiting on the answer.
-	client := llm.New(lp.BaseURL(), 5*time.Minute)
+	client := llmClientFor(lp, 5*time.Minute)
 	ev := memeval.NewEvaluator(st, st, client, memeval.Config{
 		MaxItems:      cfg.MemoryEval.MaxItems,
 		MinConfidence: cfg.MemoryEval.MinConfidence,

cmd/mavend/modelswap.go

@@ -0,0 +1,113 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"path/filepath"
+	"time"
+
+	"github.com/kami/maven/internal/config"
+	"github.com/kami/maven/internal/ipc"
+	"github.com/kami/maven/internal/llm"
+	"github.com/kami/maven/internal/phraser"
+)
+
+// Swapping the resident model while the daemon runs (Vikunja #250).
+//
+// Off unless configured: with no phraser.swap_models allowlist the two IPC
+// methods are never wired, so they answer ErrUnknownMethod. When it is wired the
+// swap method is AuthStepUp (internal/auth), which means an authed human surface
+// only — there is no act, no intent and no timer that reaches it. The daemon
+// never decides to change its own brain.
+//
+// The allowlist is exact-match against paths a human wrote in mavend.json. The
+// request carries a path and llama-server is started with it as `-m`, so
+// anything looser would turn "swap the model" into "load any file on my disk".
+func wireModelSwap(srv *ipc.Server, phr phraser.Phraser, cfg *config.Config) {
+	if cfg.Phraser == nil || len(cfg.Phraser.SwapModels) == 0 {
+		return
+	}
+	lp, ok := phr.(*phraser.LLMPhraser)
+	if !ok {
+		log.Printf("model swap: phraser.swap_models is set but there is no llama-server phraser — swap disabled")
+		return
+	}
+	allowed := map[string]bool{}
+	for _, m := range cfg.Phraser.SwapModels {
+		allowed[filepath.Clean(m)] = true
+	}
+	// The configured model is always swappable back to, listed or not: the way
+	// out of a bad swap must not depend on remembering to allowlist the model
+	// you are already running.
+	allowed[filepath.Clean(cfg.Phraser.ModelPath)] = true
+
+	srv.SwapModelFn = func(ctx context.Context, req ipc.SwapModelReq) (ipc.SwapModelResp, error) {
+		path := filepath.Clean(req.ModelPath)
+		if !allowed[path] {
+			log.Printf("model swap: REFUSED %q — not in phraser.swap_models", req.ModelPath)
+			return ipc.SwapModelResp{}, fmt.Errorf("%w: %q is not in phraser.swap_models", ipc.ErrForbidden, req.ModelPath)
+		}
+		res, err := lp.Swap(ctx, phraser.SwapSpec{
+			ModelPath:  path,
+			NGpuLayers: req.NGpuLayers,
+			NCtx:       req.NCtx,
+		})
+		resp := ipc.SwapModelResp{
+			Model:      res.Model,
+			ModelPath:  res.ModelPath,
+			BaseURL:    res.BaseURL,
+			RolledBack: res.RolledBack,
+			TookMs:     res.Took.Milliseconds(),
+		}
+		if err != nil {
+			// A rolled-back swap is a failure that left a working daemon behind.
+			// Both halves matter to the caller, so the response is filled in even
+			// though the error is returned.
+			log.Printf("model swap: %v", err)
+			return resp, err
+		}
+		return resp, nil
+	}
+
+	srv.ModelStatusFn = func(ctx context.Context) (ipc.ModelStatusResp, error) {
+		path, ngl, nctx := lp.LiveModel()
+		base := lp.BaseURL()
+		resp := ipc.ModelStatusResp{
+			ModelPath:  path,
+			BaseURL:    base,
+			NGpuLayers: ngl,
+			NCtx:       nctx,
+			Swappable:  cfg.Phraser.SwapModels,
+		}
+		if base == "" {
+			resp.Model = llm.UnknownModel
+			return resp, nil
+		}
+		id, err := llm.ModelID(ctx, base)
+		if err != nil {
+			// Report the honest "I could not confirm it" rather than echoing the
+			// configured filename as if the server had said it.
+			resp.Model = llm.UnknownModel
+			return resp, nil
+		}
+		resp.Model = id
+		return resp, nil
+	}
+
+	log.Printf("model swap: enabled, %d allowlisted model(s) — step-up required", len(cfg.Phraser.SwapModels))
+}
+
+// llmClientFor builds a completion client on the phraser's llama-server and
+// keeps it pointed at the right one across a model swap.
+//
+// Without the OnSwap registration every holder of a base URL — the LLM router,
+// the replier, the mail extractor, the memory evaluator — would keep talking to
+// the port of a server that no longer exists, and the daemon would degrade to
+// the classifier permanently after the first swap. The client is re-pointed, not
+// rebuilt, so nothing that holds it has to know a swap happened.
+func llmClientFor(lp *phraser.LLMPhraser, timeout time.Duration) *llm.Client {
+	c := llm.New(lp.BaseURL(), timeout)
+	lp.OnSwap(func(base string) { c.SetBaseURL(base) })
+	return c
+}

cmd/mavend/voicewire.go

@@ -148,7 +148,9 @@ func wireVoice(cfg *config.Config, coreAPI ipc.CoreAPI, phr phraser.Phraser, mem
 	// The replier uses the same llama-server as the phraser.
 	var llmClient *llm.Client
 	if lp, ok := phr.(*phraser.LLMPhraser); ok {
-		llmClient = llm.New(lp.BaseURL(), 60*time.Second)
+		// llmClientFor, not llm.New: this client must follow the phraser onto
+		// the new llama-server when the resident model is swapped (Vikunja #250).
+		llmClient = llmClientFor(lp, 60*time.Second)
 	}
 	// ----- router (the cascade; floor examples seed the classifier) -----
 	// The act matcher's allowlist is exactly the enabled tool names — the

cmd/mavweb/main.go

@@ -124,6 +124,7 @@ var sidebarSections = []struct {
 		Label: "Settings",
 		Pages: []struct{ Label, URL, Key string }{
 			{Label: "Tools", URL: "/tools", Key: "tools"},
+			{Label: "Model", URL: "/models", Key: "models"},
 			{Label: "Passkey", URL: "/auth/passkey", Key: "passkey"},
 		},
 	},
@@ -191,6 +192,8 @@ func pageIcon(key string) string {
 		return `<svg class=icon width="14" height="14"><use href="/ethos-icons.svg#i-grid"/></svg>`
 	case "tools":
 		return `<svg class=icon width="14" height="14"><use href="/ethos-icons.svg#i-settings"/></svg>`
+	case "models":
+		return `<svg class=icon width="14" height="14"><use href="/ethos-icons.svg#i-wave"/></svg>`
 	case "passkey":
 		return `<svg class=icon width="14" height="14"><use href="/ethos-icons.svg#i-lock"/></svg>`
 	default:
@@ -225,6 +228,8 @@ func pageTitle(key string) string {
 		return "Ecosystem"
 	case "tools":
 		return "Tools"
+	case "models":
+		return "Resident Model"
 	case "passkey":
 		return "Passkey"
 	default:
@@ -479,6 +484,12 @@ func main() {
 	mux.HandleFunc("/routines", func(w http.ResponseWriter, r *http.Request) {
 		handleRoutines(w, r, core, stepUpSession, *requireStepUp)
 	})
+	// /models — the resident-model surface (Vikunja #250). Same step-up gate as
+	// /tools, and for a comparable reason: which model is loaded decides how every
+	// utterance is routed and how every reply is worded. GET is read-only.
+	mux.HandleFunc("/models", func(w http.ResponseWriter, r *http.Request) {
+		handleModels(w, r, core, stepUpSession, *requireStepUp)
+	})
 
 	// State-changing routes on this server, and their gate (Vikunja #317):
 	//

cmd/mavweb/models.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"html/template"
+	"log"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"github.com/kami/maven/internal/ipc"
+	"github.com/kami/maven/internal/webauthn"
+)
+
+// The resident-model surface (Vikunja #250).
+//
+// GET shows which model llama-server actually has loaded and which files the
+// daemon is configured to allow. POST swaps to one of them, behind the same
+// step-up gate as POST /tools: the loaded model decides how every utterance is
+// routed and how every reply is worded, so it is an owner action.
+//
+// There is nothing on this page Maven can press. The swap is an IPC method rated
+// AuthStepUp in internal/auth, unreachable from an act, an intent or a timer.
+
+// modelController — the two non-CoreAPI methods this page needs. *ipc.Client
+// satisfies it; a core without a swap allowlist answers ErrUnknownMethod, which
+// the page renders as "not configured" rather than an error.
+type modelController interface {
+	ModelStatus(ctx context.Context) (ipc.ModelStatusResp, error)
+	SwapModel(ctx context.Context, req ipc.SwapModelReq) (ipc.SwapModelResp, error)
+}
+
+var modelsTmpl = template.Must(template.New("models").Funcs(shellFuncs()).Parse(shellTopHTML + modelsHTML + shellBottomHTML))
+
+const modelsHTML = `{{template "shellTop" "models"}}
+<h1>Resident model</h1>
+<p class=hint>swapping requires step-up — <a href=/auth/passkey>assert a passkey</a> first. The old model is unloaded before the new one is loaded (one model fits the iGPU at a time), so turns during the load are refused and fall back to the classifier.</p>
+{{if .Msg}}<div class="msg msg-ok">{{.Msg}}</div>{{end}}
+{{if .Err}}<div class="msg msg-err">{{.Err}}</div>{{end}}
+{{if .Off}}
+<section class=card>
+<h2 class=card-title>swap not configured</h2>
+<p class=hint>this core has no <code>phraser.swap_models</code> allowlist, so there is nothing to swap to. Add the gguf paths you allow to <code>deploy/mavend.json</code> and restart once.</p>
+</section>
+{{else}}
+<section class=card>
+<h2 class=card-title>loaded now</h2>
+<div class=scroll><table>
+<tr><th>model</th><td><code>{{.Status.Model}}</code></td></tr>
+<tr><th>file</th><td><code>{{.Status.ModelPath}}</code></td></tr>
+<tr><th>server</th><td><code>{{.Status.BaseURL}}</code></td></tr>
+<tr><th>n_ctx</th><td>{{.Status.NCtx}}</td></tr>
+<tr><th>n_gpu_layers</th><td>{{.Status.NGpuLayers}}</td></tr>
+</table></div>
+<p class=hint>the model name is what llama-server reports for itself, not what the config says it should be.</p>
+</section>
+<section class=card>
+<h2 class=card-title>allowed models <span class=badge>{{len .Status.Swappable}}</span></h2>
+{{if .Status.Swappable}}<div class=scroll><table><tr><th>file</th><th></th></tr>
+{{range .Status.Swappable}}<tr><td><code>{{.}}</code></td>
+<td><form method=post action=/models class=inline-form>
+<input type=hidden name=model_path value="{{.}}">
+<button class=btn>load this one</button></form></td></tr>{{end}}
+</table></div>
+{{else}}<div class=empty><div>no models allowlisted</div></div>{{end}}
+</section>
+{{end}}
+{{template "shellBottom"}}`
+
+type modelsPage struct {
+	Msg    string
+	Err    string
+	Off    bool
+	Status ipc.ModelStatusResp
+}
+
+// handleModels renders the model surface (GET) and applies a swap (POST).
+//
+// A failed swap is reported as a failure with the model that is still serving
+// named, because that is the state the operator needs: the daemon rolled back
+// and is answering turns, it just is not answering them with what he asked for.
+func handleModels(w http.ResponseWriter, r *http.Request, core ipc.CoreAPI, session *webauthn.PasskeySession, requireStepUp bool) {
+	if core == nil {
+		http.Error(w, "models disabled (no -core)", http.StatusServiceUnavailable)
+		return
+	}
+	mc, ok := core.(modelController)
+	if !ok {
+		http.Error(w, "models unavailable: core connection does not support model swap", http.StatusServiceUnavailable)
+		return
+	}
+	ctx := r.Context()
+	page := modelsPage{}
+
+	if r.Method == http.MethodPost {
+		if !stepUpOK(session, requireStepUp) {
+			http.Error(w, "step-up required: assert a passkey first", http.StatusForbidden)
+			return
+		}
+		path := strings.TrimSpace(r.FormValue("model_path"))
+		if path == "" {
+			http.Error(w, "model_path required", http.StatusBadRequest)
+			return
+		}
+		req := ipc.SwapModelReq{ModelPath: path}
+		if v, err := strconv.Atoi(r.FormValue("n_ctx")); err == nil {
+			req.NCtx = v
+		}
+		res, err := mc.SwapModel(ctx, req)
+		switch {
+		case err == nil:
+			page.Msg = "loaded " + res.Model + " (" + strconv.FormatInt(res.TookMs, 10) + "ms)"
+			log.Printf("models: swapped to %s (%s) in %dms", res.ModelPath, res.Model, res.TookMs)
+		case errors.Is(err, ipc.ErrForbidden):
+			http.Error(w, "refused: that model is not in phraser.swap_models, or step-up was not asserted", http.StatusForbidden)
+			return
+		case errors.Is(err, ipc.ErrUnknownMethod):
+			http.Error(w, "swap not configured on this core", http.StatusServiceUnavailable)
+			return
+		case res.RolledBack:
+			page.Err = "swap failed, rolled back to " + res.Model + " — she is still answering, with the old model"
+			log.Printf("models: swap to %s failed, rolled back: %v", path, err)
+		default:
+			page.Err = "swap failed: " + err.Error()
+			log.Printf("models: swap to %s failed: %v", path, err)
+		}
+	}
+
+	st, err := mc.ModelStatus(ctx)
+	if err != nil {
+		if errors.Is(err, ipc.ErrUnknownMethod) {
+			page.Off = true
+		} else {
+			log.Printf("models: status: %v", err)
+			http.Error(w, "core read failed", http.StatusBadGateway)
+			return
+		}
+	}
+	page.Status = st
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	if err := modelsTmpl.Execute(w, page); err != nil {
+		log.Printf("models render: %v", err)
+	}
+}

cmd/mavweb/models_test.go

@@ -0,0 +1,150 @@
+package main
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/kami/maven/internal/ipc"
+	"github.com/kami/maven/internal/webauthn"
+)
+
+// fakeModelCore is a core that supports the two model methods. It records what
+// the page asked for, so the tests can assert the gate rather than the HTML.
+type fakeModelCore struct {
+	ipc.UnimplementedCoreAPI
+
+	status    ipc.ModelStatusResp
+	statusErr error
+
+	swapResp ipc.SwapModelResp
+	swapErr  error
+	swapped  []ipc.SwapModelReq
+}
+
+func (f *fakeModelCore) ModelStatus(ctx context.Context) (ipc.ModelStatusResp, error) {
+	return f.status, f.statusErr
+}
+
+func (f *fakeModelCore) SwapModel(ctx context.Context, req ipc.SwapModelReq) (ipc.SwapModelResp, error) {
+	f.swapped = append(f.swapped, req)
+	return f.swapResp, f.swapErr
+}
+
+func modelsGET(t *testing.T, core ipc.CoreAPI) *httptest.ResponseRecorder {
+	t.Helper()
+	w := httptest.NewRecorder()
+	handleModels(w, httptest.NewRequest(http.MethodGet, "/models", nil), core, nil, false)
+	return w
+}
+
+func modelsPOST(t *testing.T, core ipc.CoreAPI, session *webauthn.PasskeySession, requireStepUp bool, path string) *httptest.ResponseRecorder {
+	t.Helper()
+	r := httptest.NewRequest(http.MethodPost, "/models", strings.NewReader("model_path="+path))
+	r.Header.Set("Content-Type", "application/x-www-form-urlencoded")
+	w := httptest.NewRecorder()
+	handleModels(w, r, core, session, requireStepUp)
+	return w
+}
+
+func TestModels_GETShowsTheLoadedModelAndTheAllowlist(t *testing.T) {
+	core := &fakeModelCore{status: ipc.ModelStatusResp{
+		Model:     "Qwen3-1.7B-UD-Q4_K_XL",
+		ModelPath: "/opt/maven/models/llm/qwen3.gguf",
+		BaseURL:   "http://127.0.0.1:18099",
+		NCtx:      4096,
+		Swappable: []string{"/opt/maven/models/llm/qwen3.gguf", "/opt/maven/models/llm/qwen3-cpt.gguf"},
+	}}
+	w := modelsGET(t, core)
+	if w.Code != http.StatusOK {
+		t.Fatalf("GET /models = %d; want 200", w.Code)
+	}
+	body := w.Body.String()
+	for _, want := range []string{"Qwen3-1.7B-UD-Q4_K_XL", "qwen3-cpt.gguf", "4096"} {
+		if !strings.Contains(body, want) {
+			t.Errorf("page does not mention %q", want)
+		}
+	}
+	if len(core.swapped) != 0 {
+		t.Errorf("a GET swapped the model: %v", core.swapped)
+	}
+}
+
+func TestModels_POSTRequiresStepUpWhenFailingClosed(t *testing.T) {
+	// No WebAuthn configured (nil session) + -require-stepup ⇒ deny, exactly
+	// like POST /tools. Nothing reaches core.
+	core := &fakeModelCore{}
+	w := modelsPOST(t, core, nil, true, "/opt/maven/models/llm/qwen3.gguf")
+	if w.Code != http.StatusForbidden {
+		t.Fatalf("POST /models without assertable step-up = %d; want 403", w.Code)
+	}
+	if len(core.swapped) != 0 {
+		t.Fatalf("a denied POST still called SwapModel: %v", core.swapped)
+	}
+}
+
+func TestModels_POSTSwapsAndReportsTheModelThatAnswered(t *testing.T) {
+	core := &fakeModelCore{
+		swapResp: ipc.SwapModelResp{Model: "qwen3-cpt", ModelPath: "/m/cpt.gguf", TookMs: 4200},
+		status:   ipc.ModelStatusResp{Model: "qwen3-cpt", ModelPath: "/m/cpt.gguf"},
+	}
+	w := modelsPOST(t, core, nil, false, "/m/cpt.gguf")
+	if w.Code != http.StatusOK {
+		t.Fatalf("POST /models = %d; want 200", w.Code)
+	}
+	if len(core.swapped) != 1 || core.swapped[0].ModelPath != "/m/cpt.gguf" {
+		t.Fatalf("SwapModel calls = %v; want one for /m/cpt.gguf", core.swapped)
+	}
+	if !strings.Contains(w.Body.String(), "loaded qwen3-cpt") {
+		t.Errorf("page does not report which model was loaded:\n%s", w.Body.String())
+	}
+}
+
+func TestModels_RolledBackSwapSaysSheIsStillAnswering(t *testing.T) {
+	core := &fakeModelCore{
+		swapResp: ipc.SwapModelResp{Model: "qwen3", ModelPath: "/m/old.gguf", RolledBack: true},
+		swapErr:  errBrokenModel{},
+		status:   ipc.ModelStatusResp{Model: "qwen3", ModelPath: "/m/old.gguf"},
+	}
+	w := modelsPOST(t, core, nil, false, "/m/cpt.gguf")
+	if w.Code != http.StatusOK {
+		t.Fatalf("POST /models after a rollback = %d; want 200 with the failure rendered", w.Code)
+	}
+	body := w.Body.String()
+	if !strings.Contains(body, "rolled back to qwen3") {
+		t.Errorf("page does not say it rolled back:\n%s", body)
+	}
+}
+
+func TestModels_RefusedPathIs403(t *testing.T) {
+	core := &fakeModelCore{swapErr: ipc.ErrForbidden}
+	w := modelsPOST(t, core, nil, false, "/etc/passwd")
+	if w.Code != http.StatusForbidden {
+		t.Fatalf("POST /models with a non-allowlisted path = %d; want 403", w.Code)
+	}
+}
+
+func TestModels_UnconfiguredCoreRendersOff(t *testing.T) {
+	core := &fakeModelCore{statusErr: ipc.ErrUnknownMethod}
+	w := modelsGET(t, core)
+	if w.Code != http.StatusOK {
+		t.Fatalf("GET /models against a core without the swap = %d; want 200", w.Code)
+	}
+	if !strings.Contains(w.Body.String(), "swap not configured") {
+		t.Errorf("page does not say the capability is off:\n%s", w.Body.String())
+	}
+}
+
+func TestModels_CoreWithoutTheMethodsIs503(t *testing.T) {
+	// An in-process CoreAPI (no swap methods) must not 500 the page.
+	w := modelsGET(t, ipc.UnimplementedCoreAPI{})
+	if w.Code != http.StatusServiceUnavailable {
+		t.Fatalf("GET /models on a core without the methods = %d; want 503", w.Code)
+	}
+}
+
+type errBrokenModel struct{}
+
+func (errBrokenModel) Error() string { return "llm: server did not start" }

internal/auth/auth_test.go

@@ -393,3 +393,26 @@ func mustWriteFactParams(source string) []byte {
 	}
 	return b
 }
+
+// TestRequirement_SwapModel — loading a different resident model is an owner
+// action at the same rung as mutating the tool allowlist: it decides how every
+// utterance is routed and how every reply is worded. The read side is not.
+func TestRequirement_SwapModel(t *testing.T) {
+	if got := Requirement(ipc.MethodSwapModel); got != AuthStepUp {
+		t.Errorf("SwapModel authority = %v; want AuthStepUp", got)
+	}
+	if got := Requirement(ipc.MethodModelStatus); got != AuthRead {
+		t.Errorf("ModelStatus authority = %v; want AuthRead", got)
+	}
+	// A surface that cannot carry a passkey gesture cannot swap the model, no
+	// matter what it is enrolled as — this is the "never through voice" property.
+	voice := Scope{Surface: SurfaceVoice, Module: "voice", SourceScope: []string{"*"}}
+	if err := Can(ipc.MethodSwapModel, voice, nil); !errors.Is(err, ErrForbidden) {
+		t.Errorf("voice swapping the model = %v; want ErrForbidden", err)
+	}
+	// And with no step-up session asserted, the gate refuses even a capable surface.
+	noSession := &Gate{Enrollment: NewFloorEnrollment()}
+	if err := noSession.Check(context.Background(), ipc.MethodSwapModel, nil); !errors.Is(err, ipc.ErrForbidden) {
+		t.Errorf("SwapModel with no asserted step-up = %v; want ErrForbidden", err)
+	}
+}

internal/auth/policy.go

@@ -53,6 +53,13 @@ func Requirement(m ipc.Method) Authority {
 		// asserted — never a module or the voice/chat path. maven can propose
 		// (MethodProposeTool, no step-up: she has no passkey) but never en/disable.
 		return AuthStepUp
+	case ipc.MethodSwapModel:
+		// Swapping the resident model changes what routes every utterance and
+		// what words every reply. It is the owner's call, from a surface that can
+		// carry a passkey gesture — the same rung as mutating the tool allowlist,
+		// and for the same reason: nothing Maven says or does may reach it.
+		// MethodModelStatus is only the read side, so it stays at AuthRead.
+		return AuthStepUp
 	case ipc.MethodWriteFact:
 		return AuthWrite
 	case ipc.MethodAssertStepUp:
@@ -79,7 +86,10 @@ func Requirement(m ipc.Method) Authority {
 		// produce: candidate tasks and nothing else. It cannot write a fact, set a
 		// reminder, or touch the tool allowlist, so a compromised mail reader can
 		// at worst put junk on a review page he clears in one click.
-		ipc.MethodIngestMail:
+		ipc.MethodIngestMail,
+		// The read side of the model swap: which model is resident, which ones are
+		// allowlisted. It loads nothing and changes nothing.
+		ipc.MethodModelStatus:
 		return AuthRead
 	}
 	// Unknown method ⇒ AuthRead, but ipc.dispatch returns ErrUnknownMethod

internal/config/config.go

@@ -579,6 +579,21 @@ type PhraserConfig struct {
 	// persona and invented units). Chat, query and reminder phrasing always go
 	// through the model regardless. See phraser.Config.LLMNudges.
 	LLMNudges bool `json:"llm_nudges,omitempty"`
+
+	// SwapModels — the gguf files the running daemon is allowed to swap to
+	// without a restart (Vikunja #250). Empty (the default) means the swap
+	// capability does not exist: ipc.MethodSwapModel answers ErrUnknownMethod,
+	// exactly like an unconfigured weather or telegram block.
+	//
+	// It is an allowlist and not a directory on purpose. The request carries a
+	// path, and llama-server is started with it as `-m`; anything short of an
+	// exact match against a list a human wrote in this file would make "swap the
+	// model" mean "load a file of your choosing off my disk". ModelPath is
+	// always swappable back to whether or not it is listed.
+	//
+	// Paths must be absolute — the daemon's working directory is not the
+	// operator's, and a relative path here would resolve somewhere surprising.
+	SwapModels []string `json:"swap_models,omitempty"`
 }
 
 // EmbedderConfig — paths for the ONNX multilingual embedder. The daemon
@@ -820,6 +835,14 @@ func (c *Config) validate() error {
 		if c.Phraser.ModelPath == "" {
 			return errors.New("phraser.model_path is required")
 		}
+		// A relative entry in the swap allowlist would resolve against the
+		// daemon's working directory, so the path a human reads in this file
+		// would not be the path llama-server is handed. Fail at startup.
+		for _, m := range c.Phraser.SwapModels {
+			if !filepath.IsAbs(m) {
+				return fmt.Errorf("phraser.swap_models: %q must be an absolute path", m)
+			}
+		}
 	}
 	if c.Voice != nil && c.Voice.Enabled {
 		if c.Voice.Bind == "" {

internal/config/config_test.go

@@ -293,3 +293,35 @@ func TestPatternProposalNotifyDefaultsOff(t *testing.T) {
 		t.Errorf("cooldown = %v, want 6h", c.PatternProposals.Cooldown)
 	}
 }
+
+// TestSwapModelsAbsentMeansOff — the swap capability does not exist unless the
+// operator lists the models he allows (Vikunja #250).
+func TestSwapModelsAbsentMeansOff(t *testing.T) {
+	c, err := Load(writeConfig(t, `{"phraser": {"model_path": "/m/qwen.gguf"}}`))
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(c.Phraser.SwapModels) != 0 {
+		t.Errorf("swap_models = %v; want empty when unconfigured", c.Phraser.SwapModels)
+	}
+}
+
+func TestSwapModelsParsedAndMustBeAbsolute(t *testing.T) {
+	c, err := Load(writeConfig(t, `{"phraser": {
+		"model_path": "/m/qwen.gguf",
+		"swap_models": ["/m/qwen.gguf", "/m/qwen-cpt.gguf"]
+	}}`))
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	if len(c.Phraser.SwapModels) != 2 {
+		t.Fatalf("swap_models = %v; want 2 entries", c.Phraser.SwapModels)
+	}
+	// A relative entry would resolve against the daemon's cwd, not the operator's.
+	if _, err := Load(writeConfig(t, `{"phraser": {
+		"model_path": "/m/qwen.gguf",
+		"swap_models": ["models/llm/qwen.gguf"]
+	}}`)); err == nil {
+		t.Error("Load accepted a relative swap_models entry; want a startup failure")
+	}
+}

internal/ipc/api.go

@@ -176,6 +176,50 @@ type IngestMailResp struct {
 	Skipped bool    `json:"skipped,omitempty"`
 }
 
+// SwapModelReq — load another resident model without restarting the daemon
+// (Vikunja #250). ModelPath must be one of the paths in phraser.swap_models;
+// anything else is ErrForbidden, and an unconfigured allowlist makes the whole
+// method ErrUnknownMethod.
+//
+// NGpuLayers and NCtx are zero for "keep what is loaded now", which is the
+// normal case — the same laptop iGPU, a different gguf.
+//
+// This is an owner action. It is AuthStepUp in the authority table, it is not on
+// CoreAPI, and no act, intent or timer can reach it: swapping the model is not
+// something Maven does to herself.
+type SwapModelReq struct {
+	ModelPath  string `json:"model_path"`
+	NGpuLayers int    `json:"n_gpu_layers,omitempty"`
+	NCtx       int    `json:"n_ctx,omitempty"`
+}
+
+// SwapModelResp — what the daemon ended up serving. Model is the identity the
+// new llama-server reported for itself, not an echo of the request: if the file
+// was not the model the operator thought it was, this is where it shows.
+//
+// RolledBack is true when the requested model failed to load or would not answer
+// and the previous one was put back. In that case the call also returns an error
+// — the swap did not happen — and Model names the model still serving.
+type SwapModelResp struct {
+	Model      string `json:"model"`
+	ModelPath  string `json:"model_path"`
+	BaseURL    string `json:"base_url"`
+	RolledBack bool   `json:"rolled_back,omitempty"`
+	TookMs     int64  `json:"took_ms"`
+}
+
+// ModelStatusResp — which model is resident and which ones may be swapped in.
+// Read-only; the authed page renders it. Swappable is the configured allowlist,
+// so an empty list means the capability is off.
+type ModelStatusResp struct {
+	Model      string   `json:"model"`
+	ModelPath  string   `json:"model_path"`
+	BaseURL    string   `json:"base_url"`
+	NGpuLayers int      `json:"n_gpu_layers"`
+	NCtx       int      `json:"n_ctx"`
+	Swappable  []string `json:"swappable,omitempty"`
+}
+
 type listTasksReq struct {
 	Status string `json:"status"` // "" all | "live" | candidate|open|done|dropped
 }

internal/ipc/client.go

@@ -459,6 +459,28 @@ func (c *Client) IngestMail(ctx context.Context, req IngestMailReq) (IngestMailR
 	return r, nil
 }
 
+// SwapModel asks core to load another resident model (Vikunja #250).
+// ErrUnknownMethod means core has no phraser.swap_models allowlist configured;
+// ErrForbidden means the path is not on it, or step-up was not asserted. A
+// non-nil error with RolledBack set means nothing changed — the old model is
+// still serving.
+func (c *Client) SwapModel(ctx context.Context, req SwapModelReq) (SwapModelResp, error) {
+	var r SwapModelResp
+	if err := c.call(ctx, MethodSwapModel, req, &r); err != nil {
+		return SwapModelResp{}, err
+	}
+	return r, nil
+}
+
+// ModelStatus reports the resident model and the swap allowlist. Read-only.
+func (c *Client) ModelStatus(ctx context.Context) (ModelStatusResp, error) {
+	var r ModelStatusResp
+	if err := c.call(ctx, MethodModelStatus, nil, &r); err != nil {
+		return ModelStatusResp{}, err
+	}
+	return r, nil
+}
+
 func (c *Client) DismissProposedRoutine(ctx context.Context, id int64) error {
 	return c.call(ctx, MethodDismissProposedRoutine, dismissProposedRoutineReq{ID: id}, nil)
 }

internal/ipc/ipc_test.go

@@ -6,6 +6,7 @@ import (
 	"encoding/binary"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"os"
@@ -598,3 +599,44 @@ func TestIngestMail_Hook(t *testing.T) {
 		t.Errorf("req across the wire = %+v", got)
 	}
 }
+
+// TestSwapModel_OffUnlessConfigured — no allowlist in the config means the
+// daemon never sets the hook, and the method does not exist. That is what "off
+// unless configured" looks like at the wire for the model swap (Vikunja #250).
+func TestSwapModel_OffUnlessConfigured(t *testing.T) {
+	_, _, cli, _ := newServerWithStore(t)
+	if _, err := cli.SwapModel(context.Background(), SwapModelReq{ModelPath: "/m/x.gguf"}); !errors.Is(err, ErrUnknownMethod) {
+		t.Fatalf("SwapModel error = %v, want ErrUnknownMethod", err)
+	}
+	if _, err := cli.ModelStatus(context.Background()); !errors.Is(err, ErrUnknownMethod) {
+		t.Fatalf("ModelStatus error = %v, want ErrUnknownMethod", err)
+	}
+}
+
+// TestSwapModel_Hook — the request crosses the boundary intact and the reported
+// identity comes back. A refusal from the daemon's allowlist arrives as
+// ErrForbidden, which is what a caller keys its error message off.
+func TestSwapModel_Hook(t *testing.T) {
+	_, srv, cli, _ := newServerWithStore(t)
+	var got SwapModelReq
+	srv.SwapModelFn = func(_ context.Context, req SwapModelReq) (SwapModelResp, error) {
+		got = req
+		if req.ModelPath != "/m/allowed.gguf" {
+			return SwapModelResp{}, fmt.Errorf("%w: not allowlisted", ErrForbidden)
+		}
+		return SwapModelResp{Model: "allowed", ModelPath: req.ModelPath, BaseURL: "http://127.0.0.1:9", TookMs: 12}, nil
+	}
+	resp, err := cli.SwapModel(context.Background(), SwapModelReq{ModelPath: "/m/allowed.gguf", NCtx: 4096})
+	if err != nil {
+		t.Fatalf("SwapModel: %v", err)
+	}
+	if resp.Model != "allowed" || resp.TookMs != 12 {
+		t.Errorf("resp = %+v", resp)
+	}
+	if got.NCtx != 4096 {
+		t.Errorf("req across the wire = %+v", got)
+	}
+	if _, err := cli.SwapModel(context.Background(), SwapModelReq{ModelPath: "/etc/shadow"}); !errors.Is(err, ErrForbidden) {
+		t.Fatalf("swap to a non-allowlisted path = %v; want ErrForbidden", err)
+	}
+}

internal/ipc/server.go

@@ -432,6 +432,19 @@ type Server struct {
 	// every CoreAPI implementation has to carry.
 	IngestMailFn IngestMailFunc
 
+	// SwapModelFn / ModelStatusFn — the on-the-fly resident model swap (Vikunja
+	// #250) and its read side. Set by the daemon only when phraser.swap_models
+	// lists at least one model AND the phraser owns a llama-server; nil ⇒ both
+	// methods answer ErrUnknownMethod, which is what "off unless configured"
+	// looks like at the wire.
+	//
+	// They bypass CoreAPI for the same reason IngestMailFn does: this is not a
+	// store operation, it needs the daemon's llama-server, and no other CoreAPI
+	// implementation should have to carry it. MethodSwapModel is AuthStepUp in
+	// internal/auth — owner-triggered, never an act and never a timer.
+	SwapModelFn   SwapModelFunc
+	ModelStatusFn ModelStatusFunc
+
 	// UnlockFn — unwraps the store encryption key from the wrapped blob using
 	// the passkey credential public key, opens the encrypted store, and wires
 	// the rest of the daemon (voice, loop, delivery). Set by the daemon when
@@ -450,6 +463,12 @@ type WrapKeyFunc func(ctx context.Context, publicKey []byte) error
 // public key and completes daemon initialization.
 type UnlockFunc func(ctx context.Context, publicKey []byte) error
 
+// SwapModelFunc — loads another resident model in place of the live one.
+type SwapModelFunc func(ctx context.Context, req SwapModelReq) (SwapModelResp, error)
+
+// ModelStatusFunc — reports the resident model and the swap allowlist.
+type ModelStatusFunc func(ctx context.Context) (ModelStatusResp, error)
+
 // IngestMailFunc — core-side mail extraction. Returns what was captured.
 type IngestMailFunc func(ctx context.Context, req IngestMailReq) (IngestMailResp, error)
 
@@ -620,8 +639,9 @@ func withoutParams[R any](fn func(ctx context.Context, api CoreAPI) (R, error))
 // existed) as an argument — so SetAPI's runtime swap (the unlock transition)
 // is still honored on the very next request with no extra plumbing here.
 //
-// MethodAssertStepUp, MethodStoreEncryptionKey, MethodUnlock and
-// MethodIngestMail are NOT in this table: they bypass CoreAPI entirely
+// MethodAssertStepUp, MethodStoreEncryptionKey, MethodUnlock,
+// MethodIngestMail, MethodSwapModel and MethodModelStatus are NOT in this
+// table: they bypass CoreAPI entirely
 // (s.StepUp / s.WrapKeyFn / s.UnlockFn / s.IngestMailFn), so dispatch
 // special-cases them before consulting the table.
 var methodTable = map[Method]handlerFunc{
@@ -874,6 +894,30 @@ func (s *Server) dispatch(ctx context.Context, req Request) (json.RawMessage, er
 			return marshalResult(resp), nil
 		}
 		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
+	case MethodSwapModel:
+		if s.SwapModelFn != nil {
+			var p SwapModelReq
+			if err := unmarshalParams(req.Params, &p); err != nil {
+				return nil, err
+			}
+			resp, err := s.SwapModelFn(ctx, p)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
+
+	case MethodModelStatus:
+		if s.ModelStatusFn != nil {
+			resp, err := s.ModelStatusFn(ctx)
+			if err != nil {
+				return nil, err
+			}
+			return marshalResult(resp), nil
+		}
+		return nil, fmt.Errorf("%w: %s", ErrUnknownMethod, req.Method)
 	}
 
 	h, ok := methodTable[req.Method]

internal/ipc/wire.go

@@ -51,6 +51,8 @@ const (
 	MethodListTasks              Method = "list_tasks"
 	MethodSetTaskStatus          Method = "set_task_status"
 	MethodIngestMail             Method = "ingest_mail"
+	MethodSwapModel              Method = "swap_model"
+	MethodModelStatus            Method = "model_status"
 )
 
 // Request — one frame from module to core. Params is the JSON-encoded argument

internal/llm/client.go

@@ -10,10 +10,17 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"sync"
 	"time"
 )
 
 type Client struct {
+	// mu guards base only. The base URL changes when the daemon swaps the
+	// resident model (Vikunja #250): llama-server is relaunched on a fresh
+	// port, and every holder of this client — the LLM router, the replier, the
+	// mail extractor — must follow without being rebuilt. One mutexed field is
+	// the whole mechanism; a swap re-points the client, it does not replace it.
+	mu   sync.RWMutex
 	base string
 	http *http.Client
 }
@@ -22,6 +29,25 @@ func New(baseURL string, timeout time.Duration) *Client {
 	return &Client{base: baseURL, http: &http.Client{Timeout: timeout}}
 }
 
+// SetBaseURL re-points the client at another llama-server. Safe to call while
+// requests are in flight: a request that already read the old base finishes
+// against the old base (or fails, and every caller of Complete has a fallback),
+// and the next one uses the new base. It is deliberately NOT a queue-and-retry —
+// the phraser quiesces around a swap, so the window is small and a lost turn
+// degrades to the classifier rather than hanging.
+func (c *Client) SetBaseURL(base string) {
+	c.mu.Lock()
+	c.base = base
+	c.mu.Unlock()
+}
+
+// BaseURL is the server this client currently talks to.
+func (c *Client) BaseURL() string {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return c.base
+}
+
 type Req struct {
 	System    string
 	User      string
@@ -63,7 +89,7 @@ func (c *Client) Complete(ctx context.Context, r Req) (string, error) {
 		RepeatPenalty: r.RepeatPenalty,
 		Stop:          r.Stop,
 	})
-	req, err := http.NewRequestWithContext(ctx, "POST", c.base+"/v1/chat/completions", bytes.NewReader(b))
+	req, err := http.NewRequestWithContext(ctx, "POST", c.BaseURL()+"/v1/chat/completions", bytes.NewReader(b))
 	if err != nil {
 		return "", err
 	}

internal/llm/client_test.go

@@ -57,3 +57,37 @@ func TestComplete(t *testing.T) {
 		t.Errorf("got %q, want %q", got, "ok")
 	}
 }
+
+// TestSetBaseURL — a model swap re-points every holder of the client rather than
+// rebuilding the router, the replier and the extractors (Vikunja #250).
+func TestSetBaseURL(t *testing.T) {
+	var hit string
+	srvA := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hit = "A"
+		w.Write([]byte(`{"choices":[{"message":{"content":"a"}}]}`))
+	}))
+	defer srvA.Close()
+	srvB := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		hit = "B"
+		w.Write([]byte(`{"choices":[{"message":{"content":"b"}}]}`))
+	}))
+	defer srvB.Close()
+
+	c := New(srvA.URL, 5*time.Second)
+	if _, err := c.Complete(context.Background(), Req{User: "x"}); err != nil {
+		t.Fatalf("Complete against A: %v", err)
+	}
+	if hit != "A" {
+		t.Fatalf("first request went to %q; want A", hit)
+	}
+	c.SetBaseURL(srvB.URL)
+	if got := c.BaseURL(); got != srvB.URL {
+		t.Errorf("BaseURL = %q; want %q", got, srvB.URL)
+	}
+	if _, err := c.Complete(context.Background(), Req{User: "x"}); err != nil {
+		t.Fatalf("Complete against B: %v", err)
+	}
+	if hit != "B" {
+		t.Errorf("request after the swap went to %q; want B", hit)
+	}
+}

internal/phraser/llmphraser.go

@@ -27,14 +27,46 @@ var listenRE = regexp.MustCompile(`listening on (https?://\S+)`)
 type LLMPhraser struct {
 	cfg    Config
 	client *http.Client
-	port   string
-	cmd    *exec.Cmd
-	cancel context.CancelFunc
-	wg     sync.WaitGroup
 
 	// tmpl — the hand-written Russian nudges. Default path for nudges; see
 	// Config.LLMNudges. nil only if the template file failed to load.
 	tmpl *NudgeTemplates
+
+	// spawnCtx — the parent of every llama-server this phraser starts, i.e. the
+	// daemon's own context. Deliberately NOT the per-request context of the call
+	// that asked for a model swap: that one is cancelled the moment the request
+	// returns, which would kill the model it had just loaded.
+	spawnCtx context.Context
+	cancel   context.CancelFunc
+
+	// launch / probe — the two side effects of a swap, injectable so the swap
+	// logic is testable without a real llama-server and a real model file.
+	// launch is nil when this phraser does not own its server (NewLLMPhraserAt),
+	// which is also what makes Swap refuse there.
+	launch func(ctx context.Context, cfg Config) (backend, error)
+	probe  func(ctx context.Context, base string) (string, error)
+
+	// swapMu — single-flight around Swap. Held for the whole swap, including the
+	// model load, so two concurrent swap requests can never both be loading.
+	swapMu sync.Mutex
+
+	// mu guards everything below: the live backend, the swap gate and the
+	// in-flight request count. See acquire/quiesce in swap.go.
+	mu        sync.Mutex
+	be        backend
+	live      liveModel
+	swapping  bool
+	inflight  int
+	observers []func(baseURL string)
+}
+
+// liveModel — what is actually loaded right now. Distinct from Config, which
+// stays immutable after construction: a swap changes these three fields and
+// nothing else, so no reader of cfg (prompts, grammar, timeouts) races a swap.
+type liveModel struct {
+	ModelPath  string
+	NGpuLayers int
+	NCtx       int
 }
 
 type Config struct {
@@ -85,15 +117,21 @@ func DefaultConfig(modelPath string) Config {
 func NewLLMPhraser(ctx context.Context, cfg Config) (*LLMPhraser, error) {
 	ctx, cancel := context.WithCancel(ctx)
 	p := &LLMPhraser{
-		cfg:    cfg,
-		client: &http.Client{Timeout: cfg.Timeout},
-		cancel: cancel,
-		tmpl:   loadNudgeTemplates(),
+		cfg:      cfg,
+		client:   &http.Client{Timeout: cfg.Timeout},
+		tmpl:     loadNudgeTemplates(),
+		spawnCtx: ctx,
+		cancel:   cancel,
+		launch:   spawnLlamaServer,
+		probe:    defaultProbe,
+		live:     liveModel{ModelPath: cfg.ModelPath, NGpuLayers: cfg.NGpuLayers, NCtx: cfg.NCtx},
 	}
-	if err := p.start(ctx); err != nil {
+	be, err := p.launch(ctx, cfg)
+	if err != nil {
 		cancel()
 		return nil, err
 	}
+	p.be = be
 	return p, nil
 }
 
@@ -106,11 +144,17 @@ func NewLLMPhraser(ctx context.Context, cfg Config) (*LLMPhraser, error) {
 // still uses NewLLMPhraser and still owns its own child process.
 func NewLLMPhraserAt(baseURL string, cfg Config) *LLMPhraser {
 	return &LLMPhraser{
-		cfg:    cfg,
-		client: &http.Client{Timeout: cfg.Timeout},
-		port:   strings.TrimSuffix(baseURL, "/"),
-		cancel: func() {},
-		tmpl:   loadNudgeTemplates(),
+		cfg:      cfg,
+		client:   &http.Client{Timeout: cfg.Timeout},
+		tmpl:     loadNudgeTemplates(),
+		spawnCtx: context.Background(),
+		cancel:   func() {},
+		probe:    defaultProbe,
+		// launch stays nil: we did not start this server, so we must not stop it.
+		// Swap therefore refuses here (ErrSwapNotOwned) instead of killing a
+		// server another process depends on.
+		be:   borrowedBackend(strings.TrimSuffix(baseURL, "/")),
+		live: liveModel{ModelPath: cfg.ModelPath, NGpuLayers: cfg.NGpuLayers, NCtx: cfg.NCtx},
 	}
 }
 
@@ -126,16 +170,66 @@ func loadNudgeTemplates() *NudgeTemplates {
 	return nt
 }
 
-func (p *LLMPhraser) start(ctx context.Context) error {
+// backend — one llama-server this phraser talks to. Two implementations: a
+// llamaProc we spawned and must reap, and a borrowedBackend someone else owns.
+type backend interface {
+	BaseURL() string
+	Close() error
+}
+
+// borrowedBackend — a server started and owned by someone else (the phrasing
+// scorer's shared llama-server). Closing it is a no-op by construction.
+type borrowedBackend string
+
+func (b borrowedBackend) BaseURL() string { return string(b) }
+func (b borrowedBackend) Close() error    { return nil }
+
+// llamaProc — a llama-server child process plus the goroutine reading its
+// stderr. Close kills and reaps it; see the Pdeathsig note in spawnLlamaServer.
+type llamaProc struct {
+	base   string
+	cmd    *exec.Cmd
+	cancel context.CancelFunc
+	wg     sync.WaitGroup
+}
+
+func (l *llamaProc) BaseURL() string { return l.base }
+
+func (l *llamaProc) Close() error {
+	l.cancel()
+	if l.cmd != nil && l.cmd.Process != nil {
+		_ = l.cmd.Process.Kill()
+		_ = l.cmd.Wait() // reap the process — without Wait, the child becomes a zombie
+	}
+	l.wg.Wait()
+	return nil
+}
+
+// spawnLlamaServer starts one llama-server for cfg and waits until it says which
+// address it is listening on. ctx owns the process lifetime, so it must be the
+// daemon's context, not a request's.
+func spawnLlamaServer(ctx context.Context, cfg Config) (backend, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	p, err := startLlamaProc(ctx, cfg)
+	if err != nil {
+		cancel()
+		return nil, err
+	}
+	p.cancel = cancel
+	return p, nil
+}
+
+func startLlamaProc(ctx context.Context, cfg Config) (*llamaProc, error) {
+	p := &llamaProc{}
 	args := []string{
-		"-m", p.cfg.ModelPath,
+		"-m", cfg.ModelPath,
 		"--host", "127.0.0.1",
-		"--port", extractPort(p.cfg.Listen),
-		"-c", fmt.Sprintf("%d", p.cfg.NCtx),
-		"-ngl", fmt.Sprintf("%d", p.cfg.NGpuLayers),
+		"--port", extractPort(cfg.Listen),
+		"-c", fmt.Sprintf("%d", cfg.NCtx),
+		"-ngl", fmt.Sprintf("%d", cfg.NGpuLayers),
 		"--no-webui",
 	}
-	cmd := exec.CommandContext(ctx, p.cfg.BinPath, args...)
+	cmd := exec.CommandContext(ctx, cfg.BinPath, args...)
 	// Pdeathsig: the kernel SIGKILLs llama-server the moment mavend dies — by
 	// ANY means, including SIGKILL/OOM/panic where our Close() never runs. Without
 	// it a hard-killed mavend orphans its llama-server (reparented to init, keeps
@@ -148,12 +242,12 @@ func (p *LLMPhraser) start(ctx context.Context) error {
 
 	stderr, err := cmd.StderrPipe()
 	if err != nil {
-		return fmt.Errorf("llm: stderr pipe: %w", err)
+		return nil, fmt.Errorf("llm: stderr pipe: %w", err)
 	}
 
 	if err := cmd.Start(); err != nil {
 		stderr.Close()
-		return fmt.Errorf("llm: start: %w", err)
+		return nil, fmt.Errorf("llm: start: %w", err)
 	}
 
 	portCh := make(chan string, 1)
@@ -186,32 +280,44 @@ func (p *LLMPhraser) start(ctx context.Context) error {
 
 	select {
 	case addr := <-portCh:
-		p.port = addr
-		return nil
+		p.base = addr
+		return p, nil
 	case err := <-errCh:
 		_ = cmd.Process.Kill()
 		_ = cmd.Wait()
-		return fmt.Errorf("llm: server output: %w", err)
+		return nil, fmt.Errorf("llm: server output: %w", err)
 	case <-ctx.Done():
 		_ = cmd.Process.Kill()
 		_ = cmd.Wait()
-		return ctx.Err()
+		return nil, ctx.Err()
 	case <-time.After(60 * time.Second):
 		_ = cmd.Process.Kill()
 		_ = cmd.Wait()
-		return fmt.Errorf("llm: server did not start within 60s")
+		return nil, fmt.Errorf("llm: server did not start within 60s")
 	}
 }
 
-func (p *LLMPhraser) BaseURL() string { return p.port }
+// BaseURL is the llama-server this phraser talks to right now. It changes when
+// the model is swapped, so callers that cache it must register an observer
+// (OnSwap) rather than keeping the string forever.
+func (p *LLMPhraser) BaseURL() string {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.be == nil {
+		return ""
+	}
+	return p.be.BaseURL()
+}
 
 func (p *LLMPhraser) Close() error {
 	p.cancel()
-	if p.cmd != nil && p.cmd.Process != nil {
-		_ = p.cmd.Process.Kill()
-		_ = p.cmd.Wait() // reap the process — without Wait, the child becomes a zombie
+	p.mu.Lock()
+	be := p.be
+	p.be = nil
+	p.mu.Unlock()
+	if be != nil {
+		return be.Close()
 	}
-	p.wg.Wait()
 	return nil
 }
 
@@ -350,6 +456,11 @@ func chatSystemPrompt(block func() string) string {
 // the LLM completion endpoint. Like chatWithSystem but for an arbitrary message
 // slice — the caller owns the system prompt placement.
 func (p *LLMPhraser) chatWithMessages(ctx context.Context, msgs []chatMsg, maxTokens int) (string, error) {
+	base, release, err := p.acquire()
+	if err != nil {
+		return "", err
+	}
+	defer release()
 	req := chatReq{
 		Messages:    msgs,
 		Temperature: 0.7,
@@ -360,7 +471,7 @@ func (p *LLMPhraser) chatWithMessages(ctx context.Context, msgs []chatMsg, maxTo
 	if err != nil {
 		return "", fmt.Errorf("llm: marshal: %w", err)
 	}
-	httpReq, err := http.NewRequestWithContext(ctx, "POST", p.port+"/v1/chat/completions", bytes.NewReader(body))
+	httpReq, err := http.NewRequestWithContext(ctx, "POST", base+"/v1/chat/completions", bytes.NewReader(body))
 	if err != nil {
 		return "", fmt.Errorf("llm: request: %w", err)
 	}
@@ -493,6 +604,11 @@ func (p *LLMPhraser) chat(ctx context.Context, userPrompt string) (string, error
 }
 
 func (p *LLMPhraser) chatWithSystem(ctx context.Context, system, user string, maxTokens int) (string, error) {
+	base, release, err := p.acquire()
+	if err != nil {
+		return "", err
+	}
+	defer release()
 	req := chatReq{
 		Messages: []chatMsg{
 			{Role: "system", Content: system},
@@ -507,7 +623,7 @@ func (p *LLMPhraser) chatWithSystem(ctx context.Context, system, user string, ma
 		return "", fmt.Errorf("llm: marshal: %w", err)
 	}
 
-	httpReq, err := http.NewRequestWithContext(ctx, "POST", p.port+"/v1/chat/completions", bytes.NewReader(body))
+	httpReq, err := http.NewRequestWithContext(ctx, "POST", base+"/v1/chat/completions", bytes.NewReader(body))
 	if err != nil {
 		return "", fmt.Errorf("llm: request: %w", err)
 	}

internal/phraser/swap.go

@@ -0,0 +1,330 @@
+package phraser
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/kami/maven/internal/llm"
+)
+
+// Swapping the resident model without restarting the daemon (Vikunja #250).
+//
+// Three properties this file exists to hold, in order of importance:
+//
+//  1. NEVER two models resident at once. The deploy target is a laptop iGPU
+//     with the whole 1.7B offloaded to it (`n_gpu_layers: 99`); loading a second
+//     model beside the first is how you OOM the box, and a blue/green swap that
+//     "keeps the old one warm until the new one answers" does exactly that. So
+//     the old server is killed FIRST and the new one loaded after. The cost of
+//     that ordering is a window with no model at all, which is why:
+//
+//  2. A swap is atomic from a turn's point of view. An in-flight turn finishes
+//     on the old model — Swap waits for the last one to return before killing
+//     anything. A turn that arrives during the swap is REFUSED immediately with
+//     ErrSwapping rather than blocked: every phrasing path already has a
+//     fallback (templates, "вот что я нашла", the classifier for routing), so a
+//     fast refusal degrades one turn instead of hanging it for the length of a
+//     model load. No turn ever gets half of one model and half of another.
+//
+//  3. A failed load rolls back to the model that was working. The new server is
+//     probed (it must say which model it loaded) before it is published; if the
+//     launch or the probe fails, the previous config is relaunched and the
+//     phraser goes back to serving. Only if the rollback ALSO fails is the
+//     phraser left without a backend, and then it says so loudly and every turn
+//     degrades rather than breaks.
+//
+// Not here, deliberately: nothing calls Swap on a timer, and no act or intent can
+// reach it. It is an IPC method behind the step-up gate, i.e. owner-triggered.
+
+var (
+	// ErrSwapping — a turn arrived while the model was being swapped. Callers
+	// treat it like any other LLM error and use their fallback.
+	ErrSwapping = errors.New("phraser: model swap in progress")
+
+	// ErrSwapNotOwned — this phraser did not start its llama-server, so it must
+	// not stop one (NewLLMPhraserAt: the eval harness shares a server).
+	ErrSwapNotOwned = errors.New("phraser: llama-server is not ours to swap")
+
+	// ErrNoBackend — no model is loaded at all. Only reachable after a failed
+	// swap whose rollback also failed.
+	ErrNoBackend = errors.New("phraser: no llama-server loaded")
+
+	// ErrSwapBusy — a turn was still running when the drain deadline expired, so
+	// the swap was abandoned. Nothing was killed; ask again.
+	ErrSwapBusy = errors.New("phraser: turns still in flight, swap abandoned")
+)
+
+// SwapSpec — what to load. Zero NGpuLayers/NCtx keep whatever is live, so the
+// common case ("same settings, different gguf") is one field.
+type SwapSpec struct {
+	ModelPath  string
+	NGpuLayers int
+	NCtx       int
+}
+
+// SwapResult — what happened. Model is the identity the NEW server reported, so
+// it is evidence rather than an echo of the request: if the file at ModelPath is
+// not what the operator thought it was, this is where that shows up.
+type SwapResult struct {
+	Model      string
+	BaseURL    string
+	ModelPath  string
+	RolledBack bool
+	Took       time.Duration
+}
+
+// drainTimeout — how long Swap waits for in-flight turns before giving up. A
+// turn is at most Config.Timeout (30s in deploy) plus the model's own latency;
+// 90s covers a slow Thinking generation without wedging the caller forever.
+const drainTimeout = 90 * time.Second
+
+// probeTimeout — how long the new server gets to answer "which model do you
+// have". The load itself is bounded by spawnLlamaServer's own 60s wait.
+const probeTimeout = 30 * time.Second
+
+// defaultProbe asks the server which model it has loaded. This is the health
+// check: a server that answers /v1/models has finished loading weights and is
+// serving, and its answer is the identity we report back.
+func defaultProbe(ctx context.Context, base string) (string, error) {
+	return llm.ModelID(ctx, base)
+}
+
+// OnSwap registers a callback fired with the new base URL every time the live
+// backend changes, including after a rollback. Holders of an *llm.Client (the
+// LLM router, the replier, the mail extractor) register SetBaseURL here so a
+// swap re-points them without rebuilding the router or the handler.
+//
+// Callbacks run with no lock held, in registration order.
+func (p *LLMPhraser) OnSwap(fn func(baseURL string)) {
+	if fn == nil {
+		return
+	}
+	p.mu.Lock()
+	p.observers = append(p.observers, fn)
+	p.mu.Unlock()
+}
+
+// LiveModel is the model file currently loaded (and its load settings). Empty
+// ModelPath means no model is loaded.
+func (p *LLMPhraser) LiveModel() (path string, nGpuLayers, nCtx int) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.live.ModelPath, p.live.NGpuLayers, p.live.NCtx
+}
+
+// acquire reserves a slot for one request and returns the base URL to use.
+// Every request path must call it and must call the returned release exactly
+// once — that count is what Swap drains.
+func (p *LLMPhraser) acquire() (string, func(), error) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.swapping {
+		return "", nil, ErrSwapping
+	}
+	if p.be == nil {
+		return "", nil, ErrNoBackend
+	}
+	p.inflight++
+	base := p.be.BaseURL()
+	var once bool
+	return base, func() {
+		p.mu.Lock()
+		if !once {
+			once = true
+			p.inflight--
+		}
+		p.mu.Unlock()
+	}, nil
+}
+
+// Swap loads another model in place of the live one. See the file comment for
+// the properties it guarantees. Returns the new model's reported identity, or
+// an error plus RolledBack=true when the old model was put back.
+//
+// ctx bounds the drain and the probe. It does NOT own the new server's lifetime
+// — that is the daemon's context, captured at construction — so a swap survives
+// the request that asked for it.
+func (p *LLMPhraser) Swap(ctx context.Context, spec SwapSpec) (SwapResult, error) {
+	if spec.ModelPath == "" {
+		return SwapResult{}, fmt.Errorf("phraser: swap needs a model path")
+	}
+	p.swapMu.Lock()
+	defer p.swapMu.Unlock()
+
+	if p.launch == nil {
+		return SwapResult{}, ErrSwapNotOwned
+	}
+
+	started := time.Now()
+	oldLive := p.liveSnapshot()
+	newLive := liveModel{
+		ModelPath:  spec.ModelPath,
+		NGpuLayers: pickInt(spec.NGpuLayers, oldLive.NGpuLayers),
+		NCtx:       pickInt(spec.NCtx, oldLive.NCtx),
+	}
+	if newLive == oldLive && p.BaseURL() != "" {
+		// Already serving exactly this. Report the live identity rather than
+		// pointlessly unloading and reloading the same weights.
+		base := p.BaseURL()
+		id, err := p.probeWith(ctx, base)
+		if err != nil {
+			return SwapResult{}, err
+		}
+		return SwapResult{Model: id, BaseURL: base, ModelPath: oldLive.ModelPath, Took: time.Since(started)}, nil
+	}
+
+	if err := p.quiesce(ctx); err != nil {
+		return SwapResult{}, err
+	}
+	defer p.resume()
+
+	// Property 1: the old model leaves the GPU before the new one arrives.
+	p.mu.Lock()
+	old := p.be
+	p.be = nil
+	p.mu.Unlock()
+	if old != nil {
+		_ = old.Close()
+	}
+
+	be, err := p.loadAndProbe(ctx, newLive)
+	if err != nil {
+		log.Printf("phraser: swap to %s FAILED (%v) — rolling back to %s", newLive.ModelPath, err, oldLive.ModelPath)
+		rb, rbErr := p.loadAndProbe(ctx, oldLive)
+		if rbErr != nil {
+			log.Printf("phraser: ROLLBACK to %s ALSO FAILED (%v) — no model is loaded, every phrasing path is on its fallback and routing is on the classifier until the daemon is restarted", oldLive.ModelPath, rbErr)
+			return SwapResult{RolledBack: true, Took: time.Since(started)},
+				fmt.Errorf("phraser: swap failed (%w) and rollback failed too: %v", err, rbErr)
+		}
+		p.publish(rb, oldLive)
+		return SwapResult{
+				Model: rb.id, BaseURL: rb.be.BaseURL(), ModelPath: oldLive.ModelPath,
+				RolledBack: true, Took: time.Since(started),
+			},
+			fmt.Errorf("phraser: swap to %s failed, rolled back to %s: %w", newLive.ModelPath, oldLive.ModelPath, err)
+	}
+	p.publish(be, newLive)
+	log.Printf("phraser: model swapped to %s (%s) at %s in %s", newLive.ModelPath, be.id, be.be.BaseURL(), time.Since(started).Round(time.Millisecond))
+	return SwapResult{
+		Model: be.id, BaseURL: be.be.BaseURL(), ModelPath: newLive.ModelPath,
+		Took: time.Since(started),
+	}, nil
+}
+
+// loaded — a started server plus the identity it reported.
+type loaded struct {
+	be backend
+	id string
+}
+
+// loadAndProbe starts a server for lm and verifies it answers. A server that
+// starts but will not say what it loaded is treated as a failed load and is
+// killed here — publishing it would hand every turn to a backend we could not
+// confirm.
+func (p *LLMPhraser) loadAndProbe(ctx context.Context, lm liveModel) (loaded, error) {
+	cfg := p.cfg
+	cfg.ModelPath = lm.ModelPath
+	cfg.NGpuLayers = lm.NGpuLayers
+	cfg.NCtx = lm.NCtx
+	// p.spawnCtx, not ctx: the process must outlive the request asking for it.
+	be, err := p.launch(p.spawnCtx, cfg)
+	if err != nil {
+		return loaded{}, err
+	}
+	id, err := p.probeWith(ctx, be.BaseURL())
+	if err != nil {
+		_ = be.Close()
+		return loaded{}, fmt.Errorf("phraser: %s started but would not answer: %w", lm.ModelPath, err)
+	}
+	return loaded{be: be, id: id}, nil
+}
+
+func (p *LLMPhraser) probeWith(ctx context.Context, base string) (string, error) {
+	probe := p.probe
+	if probe == nil {
+		probe = defaultProbe
+	}
+	pctx, cancel := context.WithTimeout(ctx, probeTimeout)
+	defer cancel()
+	return probe(pctx, base)
+}
+
+// quiesce closes the door on new turns and waits for the ones already running.
+// Polling rather than a sync.Cond: the wait happens once per swap, a 25ms poll
+// is invisible next to a model load, and a poll cannot deadlock on a release
+// path that panicked.
+func (p *LLMPhraser) quiesce(ctx context.Context) error {
+	p.mu.Lock()
+	if p.swapping {
+		p.mu.Unlock()
+		return ErrSwapping
+	}
+	p.swapping = true
+	inflight := p.inflight
+	p.mu.Unlock()
+	if inflight == 0 {
+		return nil
+	}
+
+	deadline := time.Now().Add(drainTimeout)
+	for {
+		select {
+		case <-ctx.Done():
+			p.resume()
+			return ctx.Err()
+		case <-time.After(25 * time.Millisecond):
+		}
+		p.mu.Lock()
+		inflight = p.inflight
+		p.mu.Unlock()
+		if inflight == 0 {
+			return nil
+		}
+		if time.Now().After(deadline) {
+			// Nothing has been killed yet, so abandoning is free: reopen the door
+			// and let the operator try again rather than cutting a live turn off
+			// mid-generation.
+			p.resume()
+			return fmt.Errorf("%w (%d still running after %s)", ErrSwapBusy, inflight, drainTimeout)
+		}
+	}
+}
+
+func (p *LLMPhraser) resume() {
+	p.mu.Lock()
+	p.swapping = false
+	p.mu.Unlock()
+}
+
+// publish makes l the live backend and tells everyone holding a base URL.
+func (p *LLMPhraser) publish(l loaded, lm liveModel) {
+	p.mu.Lock()
+	p.be = l.be
+	p.live = lm
+	obs := make([]func(string), len(p.observers))
+	copy(obs, p.observers)
+	p.mu.Unlock()
+	base := l.be.BaseURL()
+	for _, fn := range obs {
+		fn(base)
+	}
+}
+
+func (p *LLMPhraser) liveSnapshot() liveModel {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	return p.live
+}
+
+// pickInt returns v when the caller set it, and fallback otherwise. 0 is the
+// "unset" value: -1 already means "offload every layer" and deploy uses 99, so
+// nothing legitimate asks for exactly zero GPU layers through this path.
+func pickInt(v, fallback int) int {
+	if v == 0 {
+		return fallback
+	}
+	return v
+}

internal/phraser/swap_test.go

@@ -0,0 +1,311 @@
+package phraser
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+// fakeModel — a stand-in llama-server. It answers /v1/models with its own name
+// and /v1/chat/completions with a phrasing-contract reply that names itself, so
+// a test can tell WHICH model answered a turn — the property the swap is about.
+type fakeModel struct {
+	srv    *httptest.Server
+	name   string
+	closed atomic.Bool
+}
+
+func newFakeModel(t *testing.T, name string) *fakeModel {
+	t.Helper()
+	f := &fakeModel{name: name}
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/models", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(`{"data":[{"id":"/models/` + name + `.gguf"}]}`))
+	})
+	mux.HandleFunc("/v1/chat/completions", func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(`{"choices":[{"message":{"content":"{\"response\":\"` + name + `\",\"mood\":\"neutral\"}"}}]}`))
+	})
+	f.srv = httptest.NewServer(mux)
+	t.Cleanup(f.srv.Close)
+	return f
+}
+
+func (f *fakeModel) BaseURL() string { return f.srv.URL }
+func (f *fakeModel) Close() error    { f.closed.Store(true); return nil }
+
+// fakeFleet is the injected launcher: it hands out a prepared fakeModel per
+// model path, and refuses paths the test did not prepare (that is what a bad
+// gguf looks like from here). It also asserts the invariant that matters on a
+// laptop iGPU: never two servers alive at the same time.
+type fakeFleet struct {
+	mu      sync.Mutex
+	models  map[string]string // model path → fake name
+	live    int
+	maxLive int
+	launch  int
+}
+
+func (fl *fakeFleet) launcher(t *testing.T) func(context.Context, Config) (backend, error) {
+	return func(ctx context.Context, cfg Config) (backend, error) {
+		fl.mu.Lock()
+		name, ok := fl.models[cfg.ModelPath]
+		fl.launch++
+		if !ok {
+			fl.mu.Unlock()
+			return nil, errors.New("no such model file: " + cfg.ModelPath)
+		}
+		fl.live++
+		if fl.live > fl.maxLive {
+			fl.maxLive = fl.live
+		}
+		fl.mu.Unlock()
+		f := newFakeModel(t, name)
+		return &fleetBackend{fleet: fl, model: f}, nil
+	}
+}
+
+type fleetBackend struct {
+	fleet *fakeFleet
+	model *fakeModel
+	once  sync.Once
+}
+
+func (b *fleetBackend) BaseURL() string { return b.model.BaseURL() }
+func (b *fleetBackend) Close() error {
+	b.once.Do(func() {
+		b.fleet.mu.Lock()
+		b.fleet.live--
+		b.fleet.mu.Unlock()
+	})
+	return b.model.Close()
+}
+
+// newSwapPhraser builds an LLMPhraser with an injected launcher, so the swap
+// path is exercised without a gguf or a GPU.
+func newSwapPhraser(t *testing.T, fl *fakeFleet, modelPath string) *LLMPhraser {
+	t.Helper()
+	cfg := DefaultConfig(modelPath)
+	cfg.Timeout = 5 * time.Second
+	p := &LLMPhraser{
+		cfg:      cfg,
+		client:   &http.Client{Timeout: cfg.Timeout},
+		spawnCtx: context.Background(),
+		cancel:   func() {},
+		launch:   fl.launcher(t),
+		probe:    defaultProbe,
+		live:     liveModel{ModelPath: modelPath, NGpuLayers: cfg.NGpuLayers, NCtx: cfg.NCtx},
+	}
+	be, err := p.launch(p.spawnCtx, cfg)
+	if err != nil {
+		t.Fatalf("initial launch: %v", err)
+	}
+	p.be = be
+	t.Cleanup(func() { p.Close() })
+	return p
+}
+
+func TestSwap_LoadsNewModelAndRepointsHolders(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old", "/m/new.gguf": "new"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+
+	// A holder of the base URL (the LLM router's client, in the daemon).
+	var seen []string
+	p.OnSwap(func(base string) { seen = append(seen, base) })
+
+	before, err := p.PhraseChat(context.Background(), "привет", nil)
+	if err != nil || before != "old" {
+		t.Fatalf("before swap: %q, %v; want the old model to answer", before, err)
+	}
+
+	res, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/new.gguf"})
+	if err != nil {
+		t.Fatalf("Swap: %v", err)
+	}
+	if res.Model != "new" {
+		t.Errorf("res.Model = %q; want the identity the NEW server reported (%q)", res.Model, "new")
+	}
+	if res.RolledBack {
+		t.Errorf("res.RolledBack = true on a successful swap")
+	}
+	after, err := p.PhraseChat(context.Background(), "привет", nil)
+	if err != nil || after != "new" {
+		t.Fatalf("after swap: %q, %v; want the new model to answer", after, err)
+	}
+	if path, _, _ := p.LiveModel(); path != "/m/new.gguf" {
+		t.Errorf("LiveModel = %q; want /m/new.gguf", path)
+	}
+	if len(seen) != 1 || seen[0] != p.BaseURL() {
+		t.Errorf("observers saw %v; want exactly one call with the new base %q", seen, p.BaseURL())
+	}
+	if fl.maxLive > 1 {
+		t.Errorf("%d servers were alive at once; the iGPU only fits one model", fl.maxLive)
+	}
+}
+
+func TestSwap_FailedLoadRollsBackToTheWorkingModel(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+
+	res, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/broken.gguf"})
+	if err == nil {
+		t.Fatal("Swap to a model that will not load returned nil error")
+	}
+	if !res.RolledBack {
+		t.Errorf("res.RolledBack = false; a failed swap must say it rolled back")
+	}
+	if res.Model != "old" {
+		t.Errorf("res.Model = %q; want the old model back", res.Model)
+	}
+	// The point of the rollback: turns keep working.
+	got, err := p.PhraseChat(context.Background(), "привет", nil)
+	if err != nil || got != "old" {
+		t.Fatalf("after rollback: %q, %v; want the old model serving again", got, err)
+	}
+	if path, _, _ := p.LiveModel(); path != "/m/old.gguf" {
+		t.Errorf("LiveModel = %q; want the old model", path)
+	}
+	if fl.maxLive > 1 {
+		t.Errorf("%d servers alive at once during a rollback", fl.maxLive)
+	}
+}
+
+func TestSwap_ProbeFailureIsTreatedAsAFailedLoad(t *testing.T) {
+	// A server that starts but will not say what it loaded must never be
+	// published — we would be serving turns from a backend we cannot confirm.
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old", "/m/mute.gguf": "mute"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+	// Fail the probe once — for the newly launched server — and let the
+	// rollback's probe through.
+	calls := 0
+	p.probe = func(ctx context.Context, base string) (string, error) {
+		calls++
+		if calls == 1 {
+			return "", errors.New("no answer from the new server")
+		}
+		return defaultProbe(ctx, base)
+	}
+
+	_, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/mute.gguf"})
+	if err == nil {
+		t.Fatal("Swap published a server that failed its probe")
+	}
+	if path, _, _ := p.LiveModel(); path != "/m/old.gguf" {
+		t.Errorf("LiveModel = %q; want the old model after a failed probe", path)
+	}
+}
+
+func TestSwap_RollbackFailureLeavesNoBackendAndDegrades(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+	// Make the rollback fail too: the old file "disappears" mid-swap.
+	fl.mu.Lock()
+	delete(fl.models, "/m/old.gguf")
+	fl.mu.Unlock()
+
+	_, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/broken.gguf"})
+	if err == nil {
+		t.Fatal("Swap returned nil when both the load and the rollback failed")
+	}
+	// Nothing is loaded, and the request path says so rather than panicking.
+	if _, _, aerr := p.acquire(); !errors.Is(aerr, ErrNoBackend) {
+		t.Errorf("acquire error = %v; want ErrNoBackend", aerr)
+	}
+	// Phrasing degrades to its fallback instead of failing the turn.
+	got, err := p.PhraseChat(context.Background(), "привет", nil)
+	if err != nil {
+		t.Fatalf("PhraseChat after a total failure returned an error: %v", err)
+	}
+	if got == "" {
+		t.Error("PhraseChat returned empty; the fallback must still say something")
+	}
+}
+
+func TestSwap_WaitsForInFlightTurnAndRefusesNewOnes(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old", "/m/new.gguf": "new"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+
+	// Hold one turn open by taking a slot directly — the same slot every
+	// request path takes.
+	base, release, err := p.acquire()
+	if err != nil {
+		t.Fatalf("acquire: %v", err)
+	}
+	if base == "" {
+		t.Fatal("acquire returned an empty base URL")
+	}
+
+	swapped := make(chan error, 1)
+	go func() { _, e := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/new.gguf"}); swapped <- e }()
+
+	// While the swap waits to drain, a NEW turn is refused immediately rather
+	// than blocked for the length of a model load.
+	deadline := time.Now().Add(2 * time.Second)
+	for {
+		_, rel, aerr := p.acquire()
+		if rel != nil {
+			rel()
+		}
+		if errors.Is(aerr, ErrSwapping) {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("new turns were never refused during a swap (last error: %v)", aerr)
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	// The swap cannot have completed while our turn was still in flight.
+	select {
+	case e := <-swapped:
+		t.Fatalf("Swap finished before the in-flight turn released: %v", e)
+	case <-time.After(50 * time.Millisecond):
+	}
+
+	release()
+	if e := <-swapped; e != nil {
+		t.Fatalf("Swap after drain: %v", e)
+	}
+	got, err := p.PhraseChat(context.Background(), "привет", nil)
+	if err != nil || got != "new" {
+		t.Fatalf("after swap: %q, %v; want the new model", got, err)
+	}
+}
+
+func TestSwap_RefusedWhenWeDoNotOwnTheServer(t *testing.T) {
+	// NewLLMPhraserAt points at a shared server the eval harness owns. Swapping
+	// there would kill a server another process depends on.
+	p := NewLLMPhraserAt("http://127.0.0.1:1/", DefaultConfig("/m/old.gguf"))
+	if _, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/new.gguf"}); !errors.Is(err, ErrSwapNotOwned) {
+		t.Fatalf("Swap on a borrowed server = %v; want ErrSwapNotOwned", err)
+	}
+}
+
+func TestSwap_SameModelIsANoOp(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+	launchesBefore := fl.launch
+
+	res, err := p.Swap(context.Background(), SwapSpec{ModelPath: "/m/old.gguf"})
+	if err != nil {
+		t.Fatalf("Swap to the live model: %v", err)
+	}
+	if res.Model != "old" {
+		t.Errorf("res.Model = %q; want old", res.Model)
+	}
+	if fl.launch != launchesBefore {
+		t.Errorf("%d extra launches; swapping to the live model must not reload weights", fl.launch-launchesBefore)
+	}
+}
+
+func TestSwap_EmptyModelPathRefused(t *testing.T) {
+	fl := &fakeFleet{models: map[string]string{"/m/old.gguf": "old"}}
+	p := newSwapPhraser(t, fl, "/m/old.gguf")
+	if _, err := p.Swap(context.Background(), SwapSpec{}); err == nil {
+		t.Fatal("Swap with no model path returned nil error")
+	}
+}