diff --git a/scarf/Packages/ScarfCore/Sources/ScarfCore/Services/ModelCatalogService.swift b/scarf/Packages/ScarfCore/Sources/ScarfCore/Services/ModelCatalogService.swift
index 1785e11..6cf3834 100644
--- a/scarf/Packages/ScarfCore/Sources/ScarfCore/Services/ModelCatalogService.swift
+++ b/scarf/Packages/ScarfCore/Sources/ScarfCore/Services/ModelCatalogService.swift
@@ -285,6 +285,75 @@ public struct ModelCatalogService: Sendable {
         )
     }
 
+    /// Result of validating a user-entered model ID against the
+    /// selected provider. See `validateModel(_:for:)`.
+    public enum ModelValidation: Equatable, Sendable {
+        /// Accept the save — the model is in the provider's catalog
+        /// (or the provider is overlay-only, where a free-form model
+        /// name is the normal path).
+        case valid
+        /// Accept with a warning — we don't have a catalog entry for
+        /// the provider at all, so can't check. Usually means the
+        /// user is offline or the local cache is missing. Save but
+        /// surface an advisory.
+        case unknownProvider(providerID: String)
+        /// Block the save — the provider exists but doesn't serve
+        /// that model. Includes a handful of close-by suggestions
+        /// for the UI to render as "did you mean…".
+        case invalid(providerName: String, suggestions: [String])
+    }
+
+    /// Validate `modelID` against `providerID` before persisting it as
+    /// `model.default` in `config.yaml`. Centralises the logic so both
+    /// Mac's ModelPickerSheet and ScarfGo's scoped settings editor
+    /// (Phase 4.3) use the same check. Pass-1 found that you could
+    /// save `claude-haiku-4-5-20251001` under provider `nous` —
+    /// Nous's catalog has no such model and Hermes later failed with
+    /// HTTP 404 at runtime. Catch that at save time, not 6 hours later.
+    public func validateModel(_ modelID: String, for providerID: String) -> ModelValidation {
+        let trimmed = modelID.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty else {
+            return .invalid(providerName: providerID, suggestions: [])
+        }
+
+        // Overlay-only providers (Nous Portal, OpenAI Codex, Qwen
+        // OAuth, …) serve their own catalogs that aren't mirrored to
+        // models.dev, so we don't have a reliable way to check model
+        // IDs locally. Treat any non-empty value as provisionally
+        // valid — the worst case is the runtime 404 we hit in pass-1,
+        // but the UI has the error banner now (M7 #2) to surface that
+        // cleanly.
+        //
+        // Exception: if an overlay-only provider DOES appear in the
+        // models.dev cache (unlikely but possible as catalogs evolve),
+        // we fall through to the real check below.
+        let models = loadModels(for: providerID)
+        if models.isEmpty {
+            if Self.overlayOnlyProviders[providerID] != nil {
+                return .valid
+            }
+            return .unknownProvider(providerID: providerID)
+        }
+
+        if models.contains(where: { $0.modelID == trimmed }) {
+            return .valid
+        }
+
+        // No exact match — offer the closest names (by prefix) as
+        // suggestions. Up to 5, ordered by release date (newest
+        // first — already the sort order of loadModels).
+        let lowerTrimmed = trimmed.lowercased()
+        let byPrefix = models
+            .filter { $0.modelID.lowercased().hasPrefix(String(lowerTrimmed.prefix(3))) }
+            .prefix(5)
+            .map(\.modelID)
+        let suggestions = byPrefix.isEmpty
+            ? Array(models.prefix(5).map(\.modelID))
+            : Array(byPrefix)
+        let providerName = providerByID(providerID)?.providerName ?? providerID
+        return .invalid(providerName: providerName, suggestions: suggestions)
+    }
+
     // MARK: - Decoding
 
     private func loadCatalog() -> [String: ProviderEntry]? {
diff --git a/scarf/Packages/ScarfCore/Tests/ScarfCoreTests/M0cServicesTests.swift b/scarf/Packages/ScarfCore/Tests/ScarfCoreTests/M0cServicesTests.swift
index 2657c07..a4ebff6 100644
--- a/scarf/Packages/ScarfCore/Tests/ScarfCoreTests/M0cServicesTests.swift
+++ b/scarf/Packages/ScarfCore/Tests/ScarfCoreTests/M0cServicesTests.swift
@@ -207,6 +207,94 @@ import Foundation
         #expect(bad.loadProviders().isEmpty)
     }
 
+    @Test func validateModelAcceptsCatalogHit() throws {
+        let tmp = FileManager.default.temporaryDirectory.appendingPathComponent("scarf-catalog-\(UUID().uuidString).json")
+        defer { try? FileManager.default.removeItem(at: tmp) }
+        let json = #"""
+        {
+          "deepseek": {
+            "id": "deepseek",
+            "name": "DeepSeek",
+            "models": {
+              "deepseek-v4-flash": {"name": "DeepSeek v4 Flash"},
+              "deepseek-v4-pro": {"name": "DeepSeek v4 Pro"}
+            }
+          }
+        }
+        """#
+        try json.write(to: tmp, atomically: true, encoding: .utf8)
+        let svc = ModelCatalogService(path: tmp.path)
+        #expect(svc.validateModel("deepseek-v4-flash", for: "deepseek") == .valid)
+    }
+
+    @Test func validateModelRejectsMissingModelWithSuggestions() throws {
+        let tmp = FileManager.default.temporaryDirectory.appendingPathComponent("scarf-catalog-\(UUID().uuidString).json")
+        defer { try? FileManager.default.removeItem(at: tmp) }
+        let json = #"""
+        {
+          "deepseek": {
+            "id": "deepseek",
+            "name": "DeepSeek",
+            "models": {
+              "deepseek-v4-flash": {"name": "DeepSeek v4 Flash"},
+              "deepseek-v4-pro": {"name": "DeepSeek v4 Pro"}
+            }
+          }
+        }
+        """#
+        try json.write(to: tmp, atomically: true, encoding: .utf8)
+        let svc = ModelCatalogService(path: tmp.path)
+        // The exact bug from pass-1: Anthropic-style model ID under
+        // deepseek provider.
+        let result = svc.validateModel("claude-haiku-4-5-20251001", for: "deepseek")
+        guard case let .invalid(providerName, suggestions) = result else {
+            Issue.record("Expected .invalid, got \(result)")
+            return
+        }
+        #expect(providerName == "DeepSeek")
+        // No prefix match on "cla" so we fall through to the first-5
+        // suggestion fallback; both entries are present.
+        #expect(suggestions.count == 2)
+    }
+
+    @Test func validateModelReportsUnknownProviderWhenNoCatalogEntry() throws {
+        let tmp = FileManager.default.temporaryDirectory.appendingPathComponent("scarf-catalog-\(UUID().uuidString).json")
+        defer { try? FileManager.default.removeItem(at: tmp) }
+        // Empty catalog — provider "openai" won't be found + isn't
+        // overlay-only, so should return .unknownProvider.
+        try "{}".write(to: tmp, atomically: true, encoding: .utf8)
+        let svc = ModelCatalogService(path: tmp.path)
+        let result = svc.validateModel("gpt-5", for: "openai")
+        if case .unknownProvider(let pid) = result {
+            #expect(pid == "openai")
+        } else {
+            Issue.record("Expected .unknownProvider, got \(result)")
+        }
+    }
+
+    @Test func validateModelAcceptsOverlayProvidersWithoutCatalog() throws {
+        let tmp = FileManager.default.temporaryDirectory.appendingPathComponent("scarf-catalog-\(UUID().uuidString).json")
+        defer { try? FileManager.default.removeItem(at: tmp) }
+        try "{}".write(to: tmp, atomically: true, encoding: .utf8)
+        let svc = ModelCatalogService(path: tmp.path)
+        // Nous is an overlay-only provider — any non-empty string is
+        // accepted because the overlay has no local catalog mirror.
+        #expect(svc.validateModel("deepseek/deepseek-v4-flash", for: "nous") == .valid)
+    }
+
+    @Test func validateModelRejectsEmptyInput() throws {
+        let tmp = FileManager.default.temporaryDirectory.appendingPathComponent("scarf-catalog-\(UUID().uuidString).json")
+        defer { try? FileManager.default.removeItem(at: tmp) }
+        try "{}".write(to: tmp, atomically: true, encoding: .utf8)
+        let svc = ModelCatalogService(path: tmp.path)
+        let result = svc.validateModel("", for: "nous")
+        if case .invalid = result {
+            // expected
+        } else {
+            Issue.record("Expected .invalid for empty input, got \(result)")
+        }
+    }
+
     // MARK: - ProjectDashboardService
 
     @Test func projectDashboardServiceRegistryRoundTrip() throws {
diff --git a/scarf/scarf/Features/Settings/Views/Components/ModelPickerSheet.swift b/scarf/scarf/Features/Settings/Views/Components/ModelPickerSheet.swift
index bf4b28d..f66b447 100644
--- a/scarf/scarf/Features/Settings/Views/Components/ModelPickerSheet.swift
+++ b/scarf/scarf/Features/Settings/Views/Components/ModelPickerSheet.swift
@@ -40,6 +40,12 @@ struct ModelPickerSheet: View {
     /// "Sign in to Nous Portal" button in the subscription summary.
     @State private var showNousSignIn: Bool = false
 
+    /// Validation failure surfaced on Select when the typed / selected
+    /// model isn't in the chosen provider's catalog. Pass-1 M7 #5
+    /// cross-platform fix — previously Scarf let you save any string
+    /// and the failure only appeared hours later at runtime.
+    @State private var validationIssue: ModelValidationIssue?
+
     @Environment(\.serverContext) private var serverContext
     private var catalog: ModelCatalogService { ModelCatalogService(context: serverContext) }
     private var subscriptionService: NousSubscriptionService { NousSubscriptionService(context: serverContext) }
@@ -76,6 +82,27 @@ struct ModelPickerSheet: View {
                 subscription = subscriptionService.loadState()
             }
         }
+        .alert(item: $validationIssue) { issue in
+            Alert(
+                title: Text("Model not available"),
+                message: Text(validationMessage(for: issue)),
+                primaryButton: .default(Text("Pick from catalog")) {
+                    validationIssue = nil
+                    customMode = false
+                },
+                secondaryButton: .cancel(Text("Edit"))
+            )
+        }
+    }
+
+    private func validationMessage(for issue: ModelValidationIssue) -> String {
+        var msg = "\(issue.modelID) isn't in \(issue.providerName)'s catalog."
+        if !issue.suggestions.isEmpty {
+            msg += " Did you mean one of:\n• " + issue.suggestions.joined(separator: "\n• ")
+        } else {
+            msg += " Pick one from the catalog or double-check the spelling."
+        }
+        return msg
     }
 
     private var header: some View {
@@ -423,15 +450,30 @@ struct ModelPickerSheet: View {
     }
 
     private func submitSelection() {
+        let (model, provider): (String, String)
         if customMode {
-            let model = customModelID.trimmingCharacters(in: .whitespaces)
-            let provider = resolvedCustomProvider()
-            onSelect(model, provider)
+            model = customModelID.trimmingCharacters(in: .whitespaces)
+            provider = resolvedCustomProvider()
         } else if isSelectedProviderOverlay {
-            let model = overlayModelID.trimmingCharacters(in: .whitespaces)
-            onSelect(model, selectedProviderID)
+            model = overlayModelID.trimmingCharacters(in: .whitespaces)
+            provider = selectedProviderID
         } else {
-            onSelect(selectedModelID, selectedProviderID)
+            model = selectedModelID
+            provider = selectedProviderID
+        }
+
+        // Block unknown models before they land in config.yaml.
+        // Overlay-only providers short-circuit to .valid inside the
+        // validator because their catalogs aren't in models.dev.
+        switch catalog.validateModel(model, for: provider) {
+        case .valid, .unknownProvider:
+            onSelect(model, provider)
+        case .invalid(let providerName, let suggestions):
+            validationIssue = ModelValidationIssue(
+                modelID: model,
+                providerName: providerName,
+                suggestions: suggestions
+            )
         }
     }
 
@@ -445,3 +487,12 @@ struct ModelPickerSheet: View {
             .clipShape(Capsule())
     }
 }
+
+/// Carrier for the catalog-validation alert. Identifiable so SwiftUI's
+/// `.alert(item:)` can key off each unique issue.
+private struct ModelValidationIssue: Identifiable {
+    let id = UUID()
+    let modelID: String
+    let providerName: String
+    let suggestions: [String]
+}
diff --git a/scarf/scarf/Localizable.xcstrings b/scarf/scarf/Localizable.xcstrings
index cc3836d..da98134 100644
--- a/scarf/scarf/Localizable.xcstrings
+++ b/scarf/scarf/Localizable.xcstrings
@@ -906,6 +906,7 @@
       "isCommentAutoGenerated" : true
     },
     "7 Days" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -949,6 +950,7 @@
 
     },
     "30 Days" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -989,6 +991,7 @@
       }
     },
     "90 Days" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -2043,10 +2046,15 @@
         }
       }
     },
+    "agent key · %@" : {
+      "comment" : "A label that shows the age of the agent key.",
+      "isCommentAutoGenerated" : true
+    },
     "Agent-specific instructions (optional)" : {
 
     },
     "All" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -2207,6 +2215,7 @@
       }
     },
     "All Time" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -8181,6 +8190,7 @@
       }
     },
     "Errors" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -8301,6 +8311,7 @@
       }
     },
     "Execute" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -8420,6 +8431,14 @@
         }
       }
     },
+    "expired" : {
+      "comment" : "A label for a credential that has expired.",
+      "isCommentAutoGenerated" : true
+    },
+    "expires in %lldd" : {
+      "comment" : "A badge that shows the number of days remaining until a credential expires.",
+      "isCommentAutoGenerated" : true
+    },
     "Export \"%@\" as Template" : {
       "comment" : "A title for the export form, showing the name of the project being exported.",
       "isCommentAutoGenerated" : true
@@ -8724,6 +8743,7 @@
 
     },
     "Fetch" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -10934,6 +10954,10 @@
         }
       }
     },
+    "Launch Dashboard" : {
+      "comment" : "A button that launches a web dashboard.",
+      "isCommentAutoGenerated" : true
+    },
     "Layout" : {
       "localizations" : {
         "de" : {
@@ -13837,6 +13861,10 @@
         }
       }
     },
+    "not running" : {
+      "comment" : "A label displayed when the web dashboard is not running.",
+      "isCommentAutoGenerated" : true
+    },
     "Not signed in yet." : {
       "comment" : "A description of a model picker sheet's subscription",
       "isCommentAutoGenerated" : true
@@ -14551,6 +14579,7 @@
       }
     },
     "Other" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -16187,6 +16216,7 @@
       }
     },
     "Read" : {
+      "extractionState" : "stale",
       "localizations" : {
         "de" : {
           "stringUnit" : {
@@ -23736,6 +23766,14 @@
       "comment" : "A description of the process of adding a credential via the Nous Portal.",
       "isCommentAutoGenerated" : true
     },
+    "Web Dashboard" : {
+      "comment" : "A label for the web dashboard.",
+      "isCommentAutoGenerated" : true
+    },
+    "Web Dashboard on :%lld" : {
+      "comment" : "A label displaying the port number of the web dashboard.",
+      "isCommentAutoGenerated" : true
+    },
     "Web Extract" : {
       "localizations" : {
         "de" : {