diff --git a/client/embedding_cache.go b/client/embedding_cache.go
index 8689e2b..9fdaaec 100644
--- a/client/embedding_cache.go
+++ b/client/embedding_cache.go
@@ -45,6 +45,7 @@ func DefaultSemanticCacheConfig() SemanticCacheConfig {
 // semanticEntry holds a cached response keyed by its request embedding.
 type semanticEntry struct {
 	vector    []float32
+	model     string // embedding model that produced vector; gates cross-model reuse
 	response  *EyrieResponse
 	createdAt time.Time
 
@@ -213,6 +214,12 @@ func (sp *EmbeddingCachedProvider) lookup(vec []float32) (*EyrieResponse, bool)
 		if now.Sub(e.createdAt) > sp.maxAge {
 			continue
 		}
+		// Never compare across embedding models: vectors from a different model
+		// live in an incompatible space, so the cosine score would be meaningless
+		// (and on a same-dimension model swap could serve a wrong response).
+		if e.model != sp.model {
+			continue
+		}
 		sim := cosineSimilarity(vec, e.vector)
 		if sim >= bestSim {
 			bestSim = sim
@@ -241,6 +248,7 @@ func (sp *EmbeddingCachedProvider) store(vec []float32, resp *EyrieResponse) {
 
 	e := &semanticEntry{
 		vector:    vec,
+		model:     sp.model,
 		response:  copyResponse(resp),
 		createdAt: time.Now(),
 	}
diff --git a/client/embedding_cache_test.go b/client/embedding_cache_test.go
index ffaeca4..ed8767f 100644
--- a/client/embedding_cache_test.go
+++ b/client/embedding_cache_test.go
@@ -104,6 +104,44 @@ func (errEmbedder) CreateEmbedding(_ context.Context, _ EmbeddingRequest) (*Embe
 	return nil, errEmptyEmbedding
 }
 
+// TestEmbeddingCache_ModelIsolation pins fix C: an entry stored under one
+// embedding model must NOT be served to a request embedded by a different model,
+// even when the vectors are identical — they live in incompatible spaces.
+func TestEmbeddingCache_ModelIsolation(t *testing.T) {
+	mock := NewMockProvider(MockModeEcho)
+	cfg := DefaultSemanticCacheConfig()
+	cfg.EmbeddingModel = "model-A"
+	sp := NewEmbeddingCachedProvider(mock, stubEmbedder{}, cfg)
+	ctx := context.Background()
+
+	// Warm the cache under model-A.
+	if _, err := sp.Chat(ctx, userMsg("what is the weather today"), ChatOptions{}); err != nil {
+		t.Fatalf("warm: %v", err)
+	}
+	if mock.CallCount() != 1 {
+		t.Fatalf("setup expected 1 inner call, got %d", mock.CallCount())
+	}
+
+	// Simulate the embedding model being swapped under the same cache. The prior
+	// entry (tagged model-A) must be skipped, forcing a fresh inner call rather
+	// than a cross-model false hit.
+	sp.model = "model-B"
+	if _, err := sp.Chat(ctx, userMsg("give me the weather please"), ChatOptions{}); err != nil {
+		t.Fatalf("post-swap: %v", err)
+	}
+	if mock.CallCount() != 2 {
+		t.Errorf("model swap must invalidate cross-model reuse; expected 2 inner calls, got %d", mock.CallCount())
+	}
+
+	// Requests under model-B should now cache and hit among themselves.
+	if _, err := sp.Chat(ctx, userMsg("weather report now"), ChatOptions{}); err != nil {
+		t.Fatalf("model-B hit: %v", err)
+	}
+	if mock.CallCount() != 2 {
+		t.Errorf("expected a within-model-B hit (still 2 inner calls), got %d", mock.CallCount())
+	}
+}
+
 func TestCosineSimilarity(t *testing.T) {
 	if got := cosineSimilarity([]float32{1, 0}, []float32{1, 0}); got < 0.999 {
 		t.Errorf("identical vectors should be ~1, got %f", got)
diff --git a/client/extract.go b/client/extract.go
new file mode 100644
index 0000000..1ec8d31
--- /dev/null
+++ b/client/extract.go
@@ -0,0 +1,146 @@
+package client
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// Relationship is a subject-predicate-object triple extracted from text. It is
+// the unit of a knowledge graph: subject and object are entities (nouns), and
+// predicate is the typed relation between them.
+//
+// This mirrors the typed-extraction pattern popularized by CocoIndex's
+// ExtractByLlm(output_type=list[Relationship]) — instead of free-form text, the
+// model is constrained to emit a list of these triples, validated against a JSON
+// schema with automatic retry.
+type Relationship struct {
+	// Subject is the entity the relation originates from. A noun/noun phrase.
+	Subject string `json:"subject"`
+	// Predicate is the typed relation (e.g. "depends_on", "authored_by").
+	Predicate string `json:"predicate"`
+	// Object is the entity the relation points to. A noun/noun phrase.
+	Object string `json:"object"`
+}
+
+// ExtractOptions configures triple extraction. The zero value is valid and uses
+// sensible defaults (noun-constrained entities, 2 validation retries).
+type ExtractOptions struct {
+	// Chat carries provider/model/temperature for the extraction call. If Model
+	// is empty the provider default is used.
+	Chat ChatOptions
+	// Instruction overrides the default extraction instruction. Use it to scope
+	// what relations to extract (e.g. "extract only code dependency relations").
+	// When empty, a general noun-constrained instruction is used.
+	Instruction string
+	// AllowedPredicates, when non-empty, constrains the predicate vocabulary —
+	// the model is told to use only these relation types, and triples with other
+	// predicates are dropped after extraction. This is the lightweight analogue
+	// of CocoIndex's EntityTypeConfig schema constraint.
+	AllowedPredicates []string
+	// MaxRetries is the schema-validation retry budget. Defaults to 2.
+	MaxRetries int
+}
+
+// relationshipSchema is the JSON schema for a list of Relationship triples,
+// passed to ChatWithStructuredOutput for validation + retry.
+func relationshipSchema() map[string]interface{} {
+	return map[string]interface{}{
+		"type": "object",
+		"properties": map[string]interface{}{
+			"relationships": map[string]interface{}{
+				"type": "array",
+				"items": map[string]interface{}{
+					"type": "object",
+					"properties": map[string]interface{}{
+						"subject":   map[string]interface{}{"type": "string"},
+						"predicate": map[string]interface{}{"type": "string"},
+						"object":    map[string]interface{}{"type": "string"},
+					},
+					"required": []interface{}{"subject", "predicate", "object"},
+				},
+			},
+		},
+		"required": []interface{}{"relationships"},
+	}
+}
+
+const defaultExtractInstruction = `Extract the relationships expressed in the text as subject-predicate-object triples.
+
+Rules:
+- subject and object MUST be nouns or noun phrases naming concrete entities (people, systems, concepts) — never verbs, sentences, or pronouns.
+- predicate is a short typed relation in snake_case (e.g. depends_on, authored_by, part_of).
+- Extract only relationships actually stated or clearly implied; do not invent facts.
+- Deduplicate: emit each distinct triple at most once.`
+
+// ExtractRelationships extracts subject-predicate-object triples from text using
+// schema-validated structured output with retry. It is a typed convenience layer
+// over ChatWithStructuredOutput, modeled on CocoIndex's ExtractByLlm; yaad and
+// other knowledge-graph consumers can call it instead of hand-rolling extraction
+// prompts and JSON parsing.
+func (c *EyrieClient) ExtractRelationships(ctx context.Context, text string, opts ExtractOptions) ([]Relationship, error) {
+	if strings.TrimSpace(text) == "" {
+		return nil, fmt.Errorf("eyrie: extract: text must not be empty")
+	}
+
+	instruction := opts.Instruction
+	if instruction == "" {
+		instruction = defaultExtractInstruction
+	}
+	if len(opts.AllowedPredicates) > 0 {
+		instruction += "\n\nUse ONLY these predicates: " + strings.Join(opts.AllowedPredicates, ", ") + "."
+	}
+
+	maxRetries := opts.MaxRetries
+	if maxRetries <= 0 {
+		maxRetries = 2
+	}
+
+	messages := []EyrieMessage{
+		{Role: "system", Content: instruction},
+		{Role: "user", Content: text},
+	}
+
+	schema := relationshipSchema()
+	resp, err := c.ChatWithStructuredOutput(ctx, messages, opts.Chat, SchemaValidation{
+		Schema:     schema,
+		MaxRetries: maxRetries,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("eyrie: extract relationships: %w", err)
+	}
+
+	var parsed struct {
+		Relationships []Relationship `json:"relationships"`
+	}
+	if err := json.Unmarshal([]byte(resp.Content), &parsed); err != nil {
+		return nil, fmt.Errorf("eyrie: extract relationships: decode: %w", err)
+	}
+
+	return filterRelationships(parsed.Relationships, opts.AllowedPredicates), nil
+}
+
+// filterRelationships drops empty triples and, when a predicate allowlist is
+// given, any triple whose predicate is not in it. Predicate matching is
+// case-insensitive to tolerate model casing drift.
+func filterRelationships(rels []Relationship, allowed []string) []Relationship {
+	allowSet := make(map[string]struct{}, len(allowed))
+	for _, p := range allowed {
+		allowSet[strings.ToLower(strings.TrimSpace(p))] = struct{}{}
+	}
+
+	out := make([]Relationship, 0, len(rels))
+	for _, r := range rels {
+		if strings.TrimSpace(r.Subject) == "" || strings.TrimSpace(r.Predicate) == "" || strings.TrimSpace(r.Object) == "" {
+			continue
+		}
+		if len(allowSet) > 0 {
+			if _, ok := allowSet[strings.ToLower(strings.TrimSpace(r.Predicate))]; !ok {
+				continue
+			}
+		}
+		out = append(out, r)
+	}
+	return out
+}
diff --git a/client/extract_test.go b/client/extract_test.go
new file mode 100644
index 0000000..26e7fef
--- /dev/null
+++ b/client/extract_test.go
@@ -0,0 +1,59 @@
+package client
+
+import (
+	"context"
+	"testing"
+)
+
+func TestFilterRelationships_DropsEmpty(t *testing.T) {
+	in := []Relationship{
+		{Subject: "eyrie", Predicate: "part_of", Object: "hawk-eco"},
+		{Subject: "", Predicate: "x", Object: "y"},   // empty subject
+		{Subject: "a", Predicate: "  ", Object: "b"}, // blank predicate
+		{Subject: "c", Predicate: "rel", Object: ""}, // empty object
+	}
+	out := filterRelationships(in, nil)
+	if len(out) != 1 || out[0].Subject != "eyrie" {
+		t.Fatalf("expected only the complete triple, got %#v", out)
+	}
+}
+
+func TestFilterRelationships_PredicateAllowlist(t *testing.T) {
+	in := []Relationship{
+		{Subject: "a", Predicate: "depends_on", Object: "b"},
+		{Subject: "a", Predicate: "Depends_On", Object: "c"},  // case-insensitive match
+		{Subject: "a", Predicate: "authored_by", Object: "d"}, // not allowed
+	}
+	out := filterRelationships(in, []string{"depends_on"})
+	if len(out) != 2 {
+		t.Fatalf("expected 2 depends_on triples (case-insensitive), got %d: %#v", len(out), out)
+	}
+}
+
+func TestExtractRelationships_EmptyText(t *testing.T) {
+	c := &EyrieClient{}
+	_, err := c.ExtractRelationships(context.Background(), "   ", ExtractOptions{})
+	if err == nil {
+		t.Fatal("expected error for empty text")
+	}
+}
+
+func TestRelationshipSchema_Shape(t *testing.T) {
+	s := relationshipSchema()
+	props, ok := s["properties"].(map[string]interface{})
+	if !ok {
+		t.Fatal("schema missing properties")
+	}
+	rels, ok := props["relationships"].(map[string]interface{})
+	if !ok || rels["type"] != "array" {
+		t.Fatalf("relationships should be an array, got %#v", rels)
+	}
+	items, ok := rels["items"].(map[string]interface{})
+	if !ok {
+		t.Fatal("array missing items schema")
+	}
+	req, ok := items["required"].([]interface{})
+	if !ok || len(req) != 3 {
+		t.Fatalf("each triple should require subject/predicate/object, got %#v", req)
+	}
+}