diff --git a/transports/bifrost-http/handlers/mcp.go b/transports/bifrost-http/handlers/mcp.go
index 30380e5d81a..08d3b9ba823 100644
--- a/transports/bifrost-http/handlers/mcp.go
+++ b/transports/bifrost-http/handlers/mcp.go
@@ -2143,6 +2143,27 @@ func (h *MCPHandler) updateMCPClient(ctx *fasthttp.RequestCtx) {
 		redactedExisting := h.store.RedactMCPClientConfig(existingConfig)
 		headers = mergeMCPHeaders(req.Headers, existingConfig.Headers, redactedExisting.Headers)
 	}
+	// A real change to the static headers has to be applied to the live
+	// connection, not just to the stored config: on a sticky client the
+	// credential is baked onto the transport at dial time, so updating the
+	// config alone would leave the open connection talking to the upstream
+	// with the header the admin just replaced. Diffed against the resolved
+	// (post-redaction-merge) value so a caller that round-trips the map
+	// unchanged doesn't force a needless reconnect. Only shared auth types
+	// carry a connection-level header credential — per-user values are
+	// supplied per caller and never baked into a shared transport. HTTP only,
+	// matching the transport VerifyHeadersConnection builds for the
+	// pre-flight below.
+	// Skipped for a disabled client: there is no live connection to protect,
+	// and refusing the edit because a deliberately-unreachable upstream can't
+	// be dialed would make a disabled client's credentials uneditable. It is
+	// verified on enable instead, which dials for real.
+	staticHeadersChanged := (existingConfig.AuthType == schemas.MCPAuthTypeHeaders || existingConfig.AuthType == schemas.MCPAuthTypeNone) &&
+		existingConfig.ConnectionType == schemas.MCPConnectionTypeHTTP &&
+		!disabled &&
+		req.Headers != nil && !mcpHeadersEqual(existingConfig.Headers, headers)
+	headersChanged := staticHeadersChanged && !existingConfig.Disabled
+
 	// TLSConfig: if omitted keep existing; if provided, restore raw CACertPEM when the
 	// incoming value is the redacted placeholder returned by the API.
 	tlsConfig := existingConfig.TLSConfig
@@ -2398,6 +2419,45 @@ func (h *MCPHandler) updateMCPClient(ctx *fasthttp.RequestCtx) {
 		SendError(ctx, fasthttp.StatusBadRequest, "oauth credentials cannot be rotated while disabling a client; send these as two separate requests")
 		return
 	}
+	// Pre-flight the new static headers against the upstream before anything
+	// is written. VerifyHeadersConnection dials its own ephemeral transport
+	// and closes it, touching neither the stored row nor the live connection,
+	// so a rejected credential leaves the client exactly as it was — still
+	// serving on the headers that work. Committing first and reconnecting
+	// afterwards cannot offer that: the failed dial drops the live connection
+	// (leaving the client unusable with "no active connection") while the bad
+	// headers are already persisted, so the connection checker has nothing
+	// good to retry with. Same verify-then-persist order the create path uses
+	// for per-user headers.
+	if staticHeadersChanged {
+		verifyConfig := *existingConfig
+		verifyConfig.Headers = headers
+		verifyConfig.TLSConfig = tlsConfig
+		// Only Authorization goes in this map. VerifyHeadersConnection layers
+		// StaticConfigHeaders(verifyConfig) in itself, which already carries
+		// every other header on the config; Authorization is the one entry
+		// that set deliberately withholds (so plugins never observe the
+		// bearer), and it gets applied after the plugin gate instead. Passing
+		// exactly that one header here reproduces the header set a real
+		// sticky dial builds, since sharedHeadersResolver.ConnectionHeaders
+		// resolves only Authorization too — including its first-match-wins
+		// behavior if the map somehow holds two casings of the name.
+		verifyHeaders := make(map[string]string, 1)
+		for key, value := range headers {
+			if strings.EqualFold(key, "Authorization") {
+				verifyHeaders["Authorization"] = value.GetValue()
+				break
+			}
+		}
+		bifrostCtx, cancel := lib.ConvertToBifrostContext(ctx, h.store)
+		_, _, verifyErr := h.mcpManager.VerifyHeadersConnection(bifrostCtx, &verifyConfig, verifyHeaders)
+		cancel()
+		if verifyErr != nil {
+			SendError(ctx, fasthttp.StatusUnprocessableEntity, fmt.Sprintf("The new headers were rejected by the MCP server, so nothing was changed: %v", verifyErr))
+			return
+		}
+	}
+
 	// Rotation is deferred until after the DB and in-memory client updates
 	// below both succeed (see the call site further down): RotateMCPOAuthConfig
 	// opens its own transaction and, once it commits, cascades every existing
@@ -2557,6 +2617,29 @@ func (h *MCPHandler) updateMCPClient(ctx *fasthttp.RequestCtx) {
 		}
 	}
 
+	// Swap the verified headers onto the live connection. Only a client that
+	// was and remains sticky needs this: it holds an open transport with the
+	// old header baked in, and UpdateMCPClientCredentials is the only thing
+	// that replaces it. Every other combination is already handled —
+	// UpdateMCPClient above replaced ExecutionConfig (all a per-call client
+	// needs, since it reads the current config on every dial) and itself
+	// re-dialed on a per-call->sticky flip, so re-dialing again here would
+	// just be a second connect with the same credentials.
+	//
+	// The same credentials already completed a full connect during the
+	// pre-flight above, so a failure here is a transient dial problem rather
+	// than a bad credential — and UpdateClientCredentials restores the
+	// previous ExecutionConfig on failure, leaving the connection checker to
+	// retry. Reported as a partial success for that reason, not a hard
+	// failure: every other effect of this request already committed.
+	if headersChanged && sharedConnectErr == nil && !wasPerCallConnection && !isPerCallConnection {
+		if err := h.updateMCPClientCredentialsWithRetry(ctx, id, schemasConfig); err != nil &&
+			!errors.Is(err, schemas.ErrMCPReconnectNotApplicable) {
+			logger.Error(fmt.Sprintf("MCP client %s updated, but reconnecting with the new headers failed: %v", id, err))
+			sharedConnectErr = err
+		}
+	}
+
 	// Rotate OAuth credentials only now that both the DB row and the runtime
 	// config update above have succeeded — see the comment where
 	// shouldRotateOAuthConfig was computed for why this can't run earlier.
@@ -2942,6 +3025,23 @@ func (h *MCPHandler) updateMCPClientWithRetry(ctx context.Context, id string, co
 	return lastErr
 }
 
+// mcpHeadersEqual reports whether two resolved static header maps carry the
+// same credentials. Compared on the post-merge values (mergeMCPHeaders has
+// already restored any unchanged redacted entry to its stored raw value), so
+// a caller round-tripping the redacted map it was served reads as unchanged.
+func mcpHeadersEqual(a, b map[string]schemas.SecretVar) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for key, aVal := range a {
+		bVal, ok := b[key]
+		if !ok || !aVal.Equals(&bVal) {
+			return false
+		}
+	}
+	return true
+}
+
 // updateMCPClientCredentialsWithRetry calls mcpManager.UpdateMCPClientCredentials with a short retry loop.
 func (h *MCPHandler) updateMCPClientCredentialsWithRetry(ctx context.Context, id string, config *schemas.MCPClientConfig) error {
 	const maxAttempts = 3
diff --git a/transports/bifrost-http/handlers/mcp_disabled_to_enabled_verifyheaders_test.go b/transports/bifrost-http/handlers/mcp_disabled_to_enabled_verifyheaders_test.go
new file mode 100644
index 00000000000..9e7914074ae
--- /dev/null
+++ b/transports/bifrost-http/handlers/mcp_disabled_to_enabled_verifyheaders_test.go
@@ -0,0 +1,126 @@
+package handlers
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"testing"
+
+	"github.com/maximhq/bifrost/core/schemas"
+	"github.com/maximhq/bifrost/framework/configstore"
+	configstoreTables "github.com/maximhq/bifrost/framework/configstore/tables"
+	"github.com/maximhq/bifrost/transports/bifrost-http/lib"
+	"github.com/valyala/fasthttp"
+)
+
+// fakeMCPManagerVerifyOnly is a minimal MCPManager test double for this path.
+// It records VerifyHeadersConnection and UpdateMCPClient calls so the test can
+// assert pre-flight verification ran and no live update happened on failure.
+type fakeMCPManagerVerifyOnly struct {
+	verifyCalls int
+	updateCalls int
+}
+
+func (m *fakeMCPManagerVerifyOnly) AddMCPClient(_ context.Context, _ *schemas.MCPClientConfig) error {
+	return nil
+}
+func (m *fakeMCPManagerVerifyOnly) RemoveMCPClient(_ context.Context, _ string) error { return nil }
+func (m *fakeMCPManagerVerifyOnly) UpdateMCPClient(_ context.Context, _ string, _ *schemas.MCPClientConfig) error {
+	m.updateCalls++
+	return nil
+}
+func (m *fakeMCPManagerVerifyOnly) UpdateMCPClientCredentials(_ context.Context, _ string, _ *schemas.MCPClientConfig) error {
+	return nil
+}
+func (m *fakeMCPManagerVerifyOnly) ReconnectMCPClient(_ context.Context, _ string) error { return nil }
+func (m *fakeMCPManagerVerifyOnly) CloseAndMarkNeedsReauth(_ context.Context, _ string) error {
+	return nil
+}
+func (m *fakeMCPManagerVerifyOnly) DisableMCPClient(_ context.Context, _ string) error { return nil }
+func (m *fakeMCPManagerVerifyOnly) EnableMCPClient(_ context.Context, _ string) error  { return nil }
+func (m *fakeMCPManagerVerifyOnly) VerifyPerUserOAuthConnection(_ context.Context, _ *schemas.MCPClientConfig, _ string) (map[string]schemas.ChatTool, map[string]string, error) {
+	return nil, nil, nil
+}
+func (m *fakeMCPManagerVerifyOnly) VerifyHeadersConnection(_ context.Context, _ *schemas.MCPClientConfig, _ map[string]string) (map[string]schemas.ChatTool, map[string]string, error) {
+	m.verifyCalls++
+	return nil, nil, errors.New("rejected by upstream")
+}
+func (m *fakeMCPManagerVerifyOnly) SetClientTools(_ string, _ map[string]schemas.ChatTool, _ map[string]string) {
+}
+func (m *fakeMCPManagerVerifyOnly) RequiresPerCallConnection(_ *schemas.MCPClientConfig) bool {
+	return false
+}
+
+// mockUpdateConfigStore embeds the interface so unimplemented methods panic if called.
+// The test asserts UpdateMCPClientConfig is NOT called when verification fails.
+type mockUpdateConfigStore struct {
+	configstore.ConfigStore
+	updates int
+}
+
+func (m *mockUpdateConfigStore) GetMCPClientByID(_ context.Context, id string) (*configstoreTables.TableMCPClient, error) {
+	return &configstoreTables.TableMCPClient{ClientID: id}, nil
+}
+
+func (m *mockUpdateConfigStore) GetClientConfig(_ context.Context) (*configstore.ClientConfig, error) {
+	return nil, nil
+}
+
+func (m *mockUpdateConfigStore) UpdateMCPClientConfig(_ context.Context, _ string, _ *configstoreTables.TableMCPClient) error {
+	m.updates++
+	return nil
+}
+
+func TestUpdateMCPClient_DisabledToEnabled_WithInvalidReplacementHeaders_PreflightRejects(t *testing.T) {
+	SetLogger(&mockLogger{})
+	plain := func(v string) schemas.SecretVar { return *schemas.NewSecretVar(v) }
+
+	// Existing client is disabled with some stored headers.
+	existing := &schemas.MCPClientConfig{
+		ID:                "client-1",
+		Name:              "Test",
+		ConnectionType:    schemas.MCPConnectionTypeHTTP,
+		AuthType:          schemas.MCPAuthTypeHeaders,
+		Disabled:          true,
+		Headers:           map[string]schemas.SecretVar{"Authorization": plain("Bearer old")},
+		PerUserHeaderKeys: nil,
+	}
+	store := &lib.Config{MCPConfig: &schemas.MCPConfig{ClientConfigs: []*schemas.MCPClientConfig{existing}}}
+	store.ClientConfig = &configstore.ClientConfig{} // avoid nil deref in ConvertToBifrostContext
+	cfgStore := &mockUpdateConfigStore{}
+	store.ConfigStore = cfgStore
+	mgr := &fakeMCPManagerVerifyOnly{}
+	h := &MCPHandler{store: store, mcpManager: mgr}
+
+	// Build request body: enable the client and set replacement headers.
+	disabled := false
+	body, err := json.Marshal(MCPClientUpdateRequest{
+		Disabled: &disabled,
+		Headers:  map[string]schemas.SecretVar{"Authorization": plain("Bearer new-invalid")},
+	})
+	if err != nil {
+		t.Fatalf("marshal: %v", err)
+	}
+	ctx := &fasthttp.RequestCtx{}
+	ctx.SetUserValue("id", existing.ID)
+	ctx.Request.SetBody(body)
+
+	// Exercise handler.
+	h.updateMCPClient(ctx)
+
+	if code := ctx.Response.StatusCode(); code != fasthttp.StatusUnprocessableEntity {
+		t.Fatalf("expected 422, got %d: %s", code, string(ctx.Response.Body()))
+	}
+	if mgr.verifyCalls != 1 {
+		t.Fatalf("expected VerifyHeadersConnection to run once, got %d", mgr.verifyCalls)
+	}
+	if mgr.updateCalls != 0 {
+		t.Fatalf("expected no live UpdateMCPClient on pre-flight failure, got %d", mgr.updateCalls)
+	}
+	if cfgStore.updates != 0 {
+		t.Fatalf("expected no DB UpdateMCPClientConfig on pre-flight failure, got %d", cfgStore.updates)
+	}
+	if !existing.Disabled {
+		t.Fatalf("expected in-memory config to remain disabled after rejection, got Disabled=false")
+	}
+}
diff --git a/transports/bifrost-http/handlers/mcp_headers_changed_test.go b/transports/bifrost-http/handlers/mcp_headers_changed_test.go
new file mode 100644
index 00000000000..82c5dc215ff
--- /dev/null
+++ b/transports/bifrost-http/handlers/mcp_headers_changed_test.go
@@ -0,0 +1,93 @@
+package handlers
+
+import (
+	"testing"
+
+	"github.com/maximhq/bifrost/core/schemas"
+)
+
+// TestMCPHeadersEqual pins the diff that decides whether a header edit has to
+// re-dial the upstream connection. A sticky client bakes its credential onto
+// the transport at connect time, so a false negative here leaves it talking to
+// the upstream with the header the admin just replaced; a false positive
+// cycles a live connection for an edit that changed nothing.
+func TestMCPHeadersEqual(t *testing.T) {
+	plain := func(v string) schemas.SecretVar { return *schemas.NewSecretVar(v) }
+
+	tests := []struct {
+		name string
+		a    map[string]schemas.SecretVar
+		b    map[string]schemas.SecretVar
+		want bool
+	}{
+		{
+			name: "both empty",
+			want: true,
+		},
+		{
+			name: "identical single header",
+			a:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			b:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			want: true,
+		},
+		{
+			name: "changed value",
+			a:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			b:    map[string]schemas.SecretVar{"Authorization": plain("Bearer two")},
+			want: false,
+		},
+		{
+			name: "added header",
+			a:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			b:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one"), "X-Tenant": plain("acme")},
+			want: false,
+		},
+		{
+			name: "removed header",
+			a:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one"), "X-Tenant": plain("acme")},
+			b:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			want: false,
+		},
+		{
+			name: "renamed key with same value",
+			a:    map[string]schemas.SecretVar{"X-Api-Key": plain("secret")},
+			b:    map[string]schemas.SecretVar{"X-Other-Key": plain("secret")},
+			want: false,
+		},
+		{
+			// Header names are case-sensitive in Go maps and the resolvers
+			// compare them case-insensitively, but the stored map is what gets
+			// baked onto the transport verbatim — a case change is a real
+			// change to what is persisted, so re-dialing is the safe answer.
+			name: "case-differing key",
+			a:    map[string]schemas.SecretVar{"X-Api-Key": plain("secret")},
+			b:    map[string]schemas.SecretVar{"x-api-key": plain("secret")},
+			want: false,
+		},
+		{
+			name: "empty vs populated",
+			a:    map[string]schemas.SecretVar{},
+			b:    map[string]schemas.SecretVar{"Authorization": plain("Bearer one")},
+			want: false,
+		},
+		{
+			name: "nil vs empty are both no headers",
+			a:    nil,
+			b:    map[string]schemas.SecretVar{},
+			want: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := mcpHeadersEqual(tt.a, tt.b); got != tt.want {
+				t.Errorf("mcpHeadersEqual() = %v, want %v", got, tt.want)
+			}
+			// The comparison must not depend on argument order: the caller
+			// passes (stored, resolved) and either side can be the larger map.
+			if got := mcpHeadersEqual(tt.b, tt.a); got != tt.want {
+				t.Errorf("mcpHeadersEqual() reversed = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}