diff --git a/ErsatzTV.Tests/Controllers/OpenApiSerializerContractTests.cs b/ErsatzTV.Tests/Controllers/OpenApiSerializerContractTests.cs
new file mode 100644
index 000000000..7bd4113de
--- /dev/null
+++ b/ErsatzTV.Tests/Controllers/OpenApiSerializerContractTests.cs
@@ -0,0 +1,188 @@
+using System.Text.Json;
+using ErsatzTV.Application.Artworks;
+using ErsatzTV.Application.Channels;
+using ErsatzTV.Application.Watermarks;
+using ErsatzTV.Core.Api.Channels;
+using ErsatzTV.Core.Api.MediaItems;
+using ErsatzTV.Core.Api.Settings;
+using ErsatzTV.Serialization;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Converters;
+using Newtonsoft.Json.Linq;
+using NUnit.Framework;
+using Shouldly;
+
+namespace ErsatzTV.Tests.Controllers;
+
+/// <summary>
+/// Guards that the generated OpenAPI document's property names for a set of DTOs exactly match the
+/// JSON keys the runtime MVC serializer (Newtonsoft, via <see cref="CustomContractResolver" /> +
+/// <see cref="StringEnumConverter" />) actually emits. The spec is generated from System.Text.Json
+/// metadata, whose camelCase can drift from Newtonsoft's (e.g. "ffmpegProfileId" special case, or a
+/// [JsonProperty] override). See issue #198 — a schema transformer now mirrors the runtime resolver,
+/// and this test fails if that mirroring is ever removed or broken.
+/// </summary>
+[TestFixture]
+public class OpenApiSerializerContractTests
+{
+    // Mirrors Startup.ConfigureServices -> AddNewtonsoftJson exactly.
+    private static readonly JsonSerializerSettings RuntimeSettings = new()
+    {
+        NullValueHandling = NullValueHandling.Ignore,
+        ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
+        ContractResolver = new CustomContractResolver(),
+        Converters = { new StringEnumConverter() }
+    };
+
+    private static IEnumerable<TestCaseData> Cases()
+    {
+        yield return new TestCaseData(FullyPopulatedChannel(), "ChannelViewModel").SetName("ChannelViewModel");
+        yield return new TestCaseData(FullyPopulatedFFmpegSettings(), "FFmpegSettingsResponseModel")
+            .SetName("FFmpegSettingsResponseModel");
+        yield return new TestCaseData(FullyPopulatedWatermark(), "WatermarkViewModel").SetName("WatermarkViewModel");
+        yield return new TestCaseData(FullyPopulatedMediaItemInfo(), "MediaItemInfoResponseModel")
+            .SetName("MediaItemInfoResponseModel");
+
+        // The only DTO with a [JsonProperty] override (FFmpegProfile -> "ffmpegProfile") — covers
+        // the attribute path of NewtonsoftSchemaNamingTransformer, which the cases above don't.
+        yield return new TestCaseData(FullyPopulatedChannelSummary(), "ChannelResponseModel")
+            .SetName("ChannelResponseModel");
+    }
+
+    [TestCaseSource(nameof(Cases))]
+    public void Runtime_Serialized_Keys_Should_Match_OpenApi_Schema_Properties(object dto, string schemaName)
+    {
+        // Every member of dto is non-null, so NullValueHandling.Ignore drops nothing: the emitted
+        // top-level keys are the complete runtime property set for this type.
+        var serialized = JObject.Parse(JsonConvert.SerializeObject(dto, RuntimeSettings));
+        List<string> runtimeKeys = serialized.Properties().Select(p => p.Name).OrderBy(n => n).ToList();
+
+        using JsonDocument document = JsonDocument.Parse(File.ReadAllText(FindOpenApiDocument()));
+        JsonElement properties = document.RootElement
+            .GetProperty("components")
+            .GetProperty("schemas")
+            .GetProperty(schemaName)
+            .GetProperty("properties");
+
+        List<string> schemaKeys = properties.EnumerateObject().Select(p => p.Name).OrderBy(n => n).ToList();
+
+        runtimeKeys.ShouldBe(
+            schemaKeys,
+            $"OpenAPI schema '{schemaName}' property names must match the runtime Newtonsoft JSON keys.");
+    }
+
+    private static ChannelViewModel FullyPopulatedChannel() => new(
+        1,
+        "1",
+        "Name",
+        "Group",
+        "Categories",
+        1,
+        1.0,
+        new ArtworkContentTypeModel("path", "image/png"),
+        default,
+        "selector",
+        "en",
+        "Audio Title",
+        default,
+        default,
+        1,
+        TimeSpan.Zero,
+        default,
+        1,
+        1,
+        1,
+        "en",
+        default,
+        default,
+        "template",
+        default,
+        default,
+        default,
+        true,
+        true);
+
+    private static FFmpegSettingsResponseModel FullyPopulatedFFmpegSettings() => new(
+        "/usr/bin/ffmpeg",
+        "/usr/bin/ffprobe",
+        1,
+        "en",
+        true,
+        true,
+        true,
+        true,
+        1,
+        1,
+        1,
+        1,
+        1,
+        default,
+        "script");
+
+    private static WatermarkViewModel FullyPopulatedWatermark() => new(
+        1,
+        new ArtworkContentTypeModel("path", "image/png"),
+        "Name",
+        default,
+        default,
+        default,
+        default,
+        1.0,
+        1.0,
+        1.0,
+        1,
+        1,
+        1,
+        true,
+        "expression",
+        1);
+
+    private static MediaItemInfoResponseModel FullyPopulatedMediaItemInfo() => new(
+        1,
+        "Title",
+        "Movie",
+        "Local",
+        "Server",
+        "Library",
+        default,
+        TimeSpan.Zero,
+        "1:1",
+        "16:9",
+        "30/1",
+        default,
+        1.0,
+        1,
+        1,
+        [],
+        []);
+
+    private static ChannelResponseModel FullyPopulatedChannelSummary() => new(
+        1,
+        "1",
+        1.0,
+        "Name",
+        "Group",
+        "Categories",
+        "1080p H.264",
+        "en",
+        "TransportStream",
+        true,
+        true);
+
+    private static string FindOpenApiDocument()
+    {
+        DirectoryInfo? directory = new(TestContext.CurrentContext.TestDirectory);
+        while (directory is not null)
+        {
+            string candidate = Path.Combine(directory.FullName, "ErsatzTV", "wwwroot", "openapi", "v1.json");
+            if (File.Exists(candidate))
+            {
+                return candidate;
+            }
+
+            directory = directory.Parent;
+        }
+
+        throw new FileNotFoundException("Could not find ErsatzTV/wwwroot/openapi/v1.json");
+    }
+}
diff --git a/ErsatzTV/Serialization/NewtonsoftSchemaNamingTransformer.cs b/ErsatzTV/Serialization/NewtonsoftSchemaNamingTransformer.cs
new file mode 100644
index 000000000..464db31e2
--- /dev/null
+++ b/ErsatzTV/Serialization/NewtonsoftSchemaNamingTransformer.cs
@@ -0,0 +1,99 @@
+using System.Reflection;
+using Microsoft.AspNetCore.OpenApi;
+using Microsoft.OpenApi;
+using Newtonsoft.Json.Serialization;
+
+namespace ErsatzTV.Serialization;
+
+/// <summary>
+/// OpenAPI schema transformer that renames each schema property to the exact JSON key the runtime
+/// Newtonsoft serializer (configured with <see cref="CustomContractResolver" />) would actually emit.
+/// The OpenAPI document is generated from System.Text.Json metadata, whose camelCase naming can drift
+/// from Newtonsoft's — e.g. STJ emits "fFmpegProfileId" while the MVC pipeline emits "ffmpegProfileId"
+/// (the <see cref="CustomNamingStrategy" /> special case). Mirroring the real contract resolver keeps
+/// the spec in lockstep with the wire format by construction, so future [JsonProperty] renames or
+/// naming-strategy special cases cannot drift. See issue #198.
+/// </summary>
+public static class NewtonsoftSchemaNamingTransformer
+{
+    private static readonly CustomContractResolver ContractResolver = new();
+
+    public static Task TransformAsync(
+        OpenApiSchema schema,
+        OpenApiSchemaTransformerContext context,
+        CancellationToken cancellationToken)
+    {
+        if (schema.Properties is not { Count: > 0 } properties)
+        {
+            return Task.CompletedTask;
+        }
+
+        Type clrType = context.JsonTypeInfo.Type;
+        if (ContractResolver.ResolveContract(clrType) is not JsonObjectContract contract)
+        {
+            return Task.CompletedTask;
+        }
+
+        // CLR member name -> Newtonsoft-emitted JSON property name.
+        var memberToNewtonsoftName = new Dictionary<string, string>(StringComparer.Ordinal);
+        foreach (JsonProperty jsonProperty in contract.Properties)
+        {
+            if (jsonProperty.UnderlyingName is { } underlyingName && jsonProperty.PropertyName is { } propertyName)
+            {
+                memberToNewtonsoftName[underlyingName] = propertyName;
+            }
+        }
+
+        // Current schema key (STJ name) -> desired key (Newtonsoft name), only where they differ.
+        var renames = new Dictionary<string, string>(StringComparer.Ordinal);
+        foreach (var jsonPropertyInfo in context.JsonTypeInfo.Properties)
+        {
+            string schemaKey = jsonPropertyInfo.Name;
+            if (!properties.ContainsKey(schemaKey))
+            {
+                continue;
+            }
+
+            if (jsonPropertyInfo.AttributeProvider is MemberInfo member &&
+                memberToNewtonsoftName.TryGetValue(member.Name, out string newtonsoftName) &&
+                !string.Equals(newtonsoftName, schemaKey, StringComparison.Ordinal))
+            {
+                renames[schemaKey] = newtonsoftName;
+            }
+        }
+
+        if (renames.Count == 0)
+        {
+            return Task.CompletedTask;
+        }
+
+        // Rebuild Properties preserving insertion order. A rename colliding with an existing key
+        // would silently drop a property from the spec — fail loudly instead (near-unreachable,
+        // but the generator must never emit a lossy document).
+        var renamedProperties = new Dictionary<string, IOpenApiSchema>(properties.Count, StringComparer.Ordinal);
+        foreach ((string key, IOpenApiSchema value) in properties)
+        {
+            string finalKey = renames.TryGetValue(key, out string newKey) ? newKey : key;
+            if (!renamedProperties.TryAdd(finalKey, value))
+            {
+                throw new InvalidOperationException(
+                    $"OpenAPI schema property rename collision on '{clrType.FullName}': renaming '{key}' to '{finalKey}' would overwrite an existing property.");
+            }
+        }
+
+        schema.Properties = renamedProperties;
+
+        if (schema.Required is { Count: > 0 } required)
+        {
+            var renamedRequired = new System.Collections.Generic.HashSet<string>(required.Count, StringComparer.Ordinal);
+            foreach (string key in required)
+            {
+                renamedRequired.Add(renames.TryGetValue(key, out string newKey) ? newKey : key);
+            }
+
+            schema.Required = renamedRequired;
+        }
+
+        return Task.CompletedTask;
+    }
+}
diff --git a/ErsatzTV/Startup.cs b/ErsatzTV/Startup.cs
index 8edf58221..c90399a8d 100644
--- a/ErsatzTV/Startup.cs
+++ b/ErsatzTV/Startup.cs
@@ -180,6 +180,7 @@ public class Startup
             options =>
             {
                 options.ShouldInclude += a => a.GroupName == "general";
+                options.AddSchemaTransformer(NewtonsoftSchemaNamingTransformer.TransformAsync);
                 options.AddDocumentTransformer((document, _, _) =>
                 {
                     UseStringEnumSchemas(document);
@@ -189,13 +190,18 @@ public class Startup
 
         services.AddOpenApi(
             "scripted-schedule-tagged",
-            options => { options.ShouldInclude += a => a.GroupName == "scripted-schedule"; });
+            options =>
+            {
+                options.ShouldInclude += a => a.GroupName == "scripted-schedule";
+                options.AddSchemaTransformer(NewtonsoftSchemaNamingTransformer.TransformAsync);
+            });
 
         services.AddOpenApi(
             "scripted-schedule",
             options =>
             {
                 options.ShouldInclude += a => a.GroupName == "scripted-schedule";
+                options.AddSchemaTransformer(NewtonsoftSchemaNamingTransformer.TransformAsync);
                 var tag = new OpenApiTag { Name = "ScriptedSchedule" };
                 var tagReference = new OpenApiTagReference("ScriptedSchedule");
                 options.AddOperationTransformer((operation, _, _) =>
diff --git a/ErsatzTV/wwwroot/openapi/v1.json b/ErsatzTV/wwwroot/openapi/v1.json
index 669f39879..6696380b7 100644
--- a/ErsatzTV/wwwroot/openapi/v1.json
+++ b/ErsatzTV/wwwroot/openapi/v1.json
@@ -14225,7 +14225,7 @@
           "name",
           "group",
           "categories",
-          "fFmpegProfile",
+          "ffmpegProfile",
           "language",
           "streamingMode",
           "isEnabled",
@@ -14253,7 +14253,7 @@
           "categories": {
             "type": "string"
           },
-          "fFmpegProfile": {
+          "ffmpegProfile": {
             "type": "string"
           },
           "language": {
@@ -14332,7 +14332,7 @@
           "description",
           "isSystem",
           "isDefault",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "watermarkId",
           "fallbackFillerId",
           "preRollFillerId",
@@ -14374,7 +14374,7 @@
           "isDefault": {
             "type": "boolean"
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
@@ -14494,7 +14494,7 @@
           "name",
           "group",
           "categories",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "slugSeconds",
           "logo",
           "streamSelectorMode",
@@ -14549,7 +14549,7 @@
               "string"
             ]
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
@@ -14810,7 +14810,7 @@
               }
             ]
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": [
               "null",
               "integer"
@@ -15153,7 +15153,7 @@
           "number",
           "group",
           "categories",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "slugSeconds",
           "logo",
           "streamSelectorMode",
@@ -15203,7 +15203,7 @@
               "string"
             ]
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
@@ -15314,7 +15314,7 @@
         "required": [
           "name",
           "description",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "watermarkId",
           "fallbackFillerId",
           "preRollFillerId",
@@ -15346,7 +15346,7 @@
           "description": {
             "type": "string"
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
@@ -21094,7 +21094,7 @@
           "number",
           "group",
           "categories",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "slugSeconds",
           "logo",
           "streamSelectorMode",
@@ -21144,7 +21144,7 @@
               "string"
             ]
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
@@ -21255,7 +21255,7 @@
         "required": [
           "name",
           "description",
-          "fFmpegProfileId",
+          "ffmpegProfileId",
           "watermarkId",
           "fallbackFillerId",
           "preRollFillerId",
@@ -21287,7 +21287,7 @@
           "description": {
             "type": "string"
           },
-          "fFmpegProfileId": {
+          "ffmpegProfileId": {
             "type": "integer",
             "format": "int32"
           },
diff --git a/docs/api-conventions.md b/docs/api-conventions.md
index 33c68a2d8..2a89fe5b0 100644
--- a/docs/api-conventions.md
+++ b/docs/api-conventions.md
@@ -121,6 +121,31 @@ gets this wrong. The SPA works around it with a manual override type; see `web/s
 `PlayoutAlternateSchedule`, `PlayoutTemplate`, and their request types). Copy this pattern for any
 new DTO with a `DayOfWeek` (or `DayOfWeek[]`) member — don't trust the generated numeric type.
 
+### 5a. Runtime JSON casing vs the generated spec (the `ffmpegProfileId` wart)
+
+Runtime `/api/*` JSON is serialized by **Newtonsoft** (`AddNewtonsoftJson` in `Startup.cs`), using
+`ErsatzTV/Serialization/CustomContractResolver.cs` → `CustomNamingStrategy` (camelCase **plus** a
+special case mapping any `FFmpegProfileId` member to `"ffmpegProfileId"`, and honoring any
+`[JsonProperty("...")]` attribute, e.g. `ChannelResponseModel.FFmpegProfile` →
+`[JsonProperty("ffmpegProfile")]`). The OpenAPI document, however, is generated from
+**System.Text.Json** metadata, whose camelCase can differ (it emitted `fFmpegProfileId` /
+`fFmpegProfile`). That drift silently gave the SPA the wrong key to read (issue #198).
+
+Fix (do not remove): `ErsatzTV/Serialization/NewtonsoftSchemaNamingTransformer.cs` is an OpenAPI
+**schema transformer** registered on all three documents (`options.AddSchemaTransformer(...)` in
+`Startup.cs`). For each object schema it resolves the CLR type's Newtonsoft `JsonObjectContract`
+through the *same* `CustomContractResolver` the runtime uses and renames `schema.Properties` (and
+`schema.Required`) keys to the exact names Newtonsoft would emit. This mirrors the wire format **by
+construction**, so future naming-strategy special cases or `[JsonProperty]` renames can't drift.
+
+Guard: `ErsatzTV.Tests/Controllers/OpenApiSerializerContractTests.cs` serializes fully-populated
+DTOs (ChannelViewModel, FFmpegSettingsResponseModel, WatermarkViewModel,
+MediaItemInfoResponseModel) through the runtime Newtonsoft settings and asserts the emitted top-level
+keys equal the corresponding `v1.json` schema's property set. It fails if spec generation ever drifts
+from the MVC serializer again. Note: only exact-match `FFmpegProfileId` gets the special case —
+`DefaultFFmpegProfileId` stays `defaultFFmpegProfileId` under both serializers, and non-acronym or
+single-leading-cap names (`fFmpegPath`, `fFprobePath`, `zIndex`, `rFrameRate`) already agree.
+
 ## 6. Tests
 
 - **Controller tests**: `ErsatzTV.Tests/Controllers/<Domain>ControllerTests.cs`. NUnit + Shouldly +
diff --git a/docs/decisions.md b/docs/decisions.md
index cb237a70f..2242b9ccc 100644
--- a/docs/decisions.md
+++ b/docs/decisions.md
@@ -127,3 +127,19 @@ Sample** (alongside Download Results) while a troubleshooting session is startin
 only gated Download Results. Both downloads compete with the live transcode for I/O and the sample
 archiver reads the same media file, so gating both during a session is strictly safer and costs
 nothing (sessions are short).
+
+## 2026-07-09 — OpenAPI spec mirrors the runtime Newtonsoft serializer (#198)
+
+The generated OpenAPI document is made to follow the **runtime** JSON contract, not the reverse. Runtime
+`/api/*` responses are serialized by Newtonsoft via `CustomContractResolver`/`CustomNamingStrategy`
+(camelCase + a `FFmpegProfileId`→`ffmpegProfileId` special case + `[JsonProperty]` overrides such as
+`ChannelResponseModel.FFmpegProfile`→`ffmpegProfile`), while `Microsoft.AspNetCore.OpenApi` generates the
+spec from System.Text.Json metadata, whose camelCase drifted (`fFmpegProfileId`, `fFmpegProfile`). That
+drift fed the SPA the wrong key. Rather than hand-patch the spec or change the wire format (breaking clients),
+we added `NewtonsoftSchemaNamingTransformer` — an OpenAPI schema transformer registered on all three
+documents that renames each schema property through the *same* Newtonsoft contract resolver the runtime uses,
+so the spec matches the wire format by construction. A contract test
+(`OpenApiSerializerContractTests`) serializes representative DTOs through the real runtime settings and pins
+the spec property sets to them. Decision: **the wire format is the source of truth; the spec follows it via the
+real contract resolver.** This also fixed a latent SPA bug (the channel-list "FFmpeg profile" column read
+`fFmpegProfile` and always showed "Unassigned"). Issue #198.
diff --git a/docs/spa-conventions.md b/docs/spa-conventions.md
index 426f53fa7..ffe2d810b 100644
--- a/docs/spa-conventions.md
+++ b/docs/spa-conventions.md
@@ -76,6 +76,15 @@ One file per domain in `web/src/api/`, e.g. `logs.ts`, `blocks.ts`, `playouts.ts
 - `web/src/api/index.ts` re-exports everything so screens import from `'../api'`, not from the
   individual domain file directly.
 
+**Trust the generated key casing — it mirrors the runtime.** Since #198 the OpenAPI spec is generated
+to match the runtime Newtonsoft serializer exactly (a schema transformer runs the same contract
+resolver; see `api-conventions.md` §5a), so the generated types carry the real wire keys — including
+Newtonsoft's acronym quirks like `ffmpegProfileId` (channel FFmpeg-profile id) and `ffmpegProfile`
+(channel FFmpeg-profile display name). **Do not** hand-cast responses to "fix" a key or dual-read a
+spec-cased vs runtime-cased key (the old `PlaybackTroubleshootingScreen` `#198` escape hatch that read
+`data.channel.fFmpegProfileId` has been removed — read `ffmpegProfileId` straight off the typed
+response). When you mock an API response in a test, use the generated (runtime) casing.
+
 ## 5. Artwork rendering
 
 Render `item.artwork` / `item.poster` (or whatever the DTO field is named) **directly as an `<img
diff --git a/web/src/App.test.tsx b/web/src/App.test.tsx
index 2c7d36b92..47aa024da 100644
--- a/web/src/App.test.tsx
+++ b/web/src/App.test.tsx
@@ -320,7 +320,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           id: 1,
           language: 'en',
           name: 'Retro Cartoons',
@@ -328,7 +328,7 @@ describe('ChicoryTV SPA scaffold', () => {
           streamingMode: 'HLS Direct'
         },
         {
-          fFmpegProfile: 'MPEG-TS',
+          ffmpegProfile: 'MPEG-TS',
           id: 2,
           language: 'fr',
           name: 'News 24',
@@ -426,7 +426,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -438,7 +438,7 @@ describe('ChicoryTV SPA scaffold', () => {
           streamingMode: 'HLS Direct'
         },
         {
-          fFmpegProfile: 'MPEG-TS',
+          ffmpegProfile: 'MPEG-TS',
           group: 'News',
           id: 2,
           isEnabled: false,
@@ -500,7 +500,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -535,7 +535,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -562,7 +562,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -574,7 +574,7 @@ describe('ChicoryTV SPA scaffold', () => {
           streamingMode: 'HLS Direct'
         },
         {
-          fFmpegProfile: 'MPEG-TS',
+          ffmpegProfile: 'MPEG-TS',
           group: 'News',
           id: 2,
           isEnabled: false,
@@ -610,7 +610,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -641,7 +641,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -691,7 +691,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -703,7 +703,7 @@ describe('ChicoryTV SPA scaffold', () => {
           streamingMode: 'HLS Direct'
         },
         {
-          fFmpegProfile: 'MPEG-TS',
+          ffmpegProfile: 'MPEG-TS',
           group: 'News',
           id: 2,
           isEnabled: false,
@@ -746,7 +746,7 @@ describe('ChicoryTV SPA scaffold', () => {
     mockDashboardApi({
       channels: [
         {
-          fFmpegProfile: 'HLS Direct',
+          ffmpegProfile: 'HLS Direct',
           group: 'Kids',
           id: 1,
           isEnabled: true,
@@ -758,7 +758,7 @@ describe('ChicoryTV SPA scaffold', () => {
           streamingMode: 'HLS Direct'
         },
         {
-          fFmpegProfile: 'MPEG-TS',
+          ffmpegProfile: 'MPEG-TS',
           group: 'News',
           id: 2,
           isEnabled: true,
@@ -3239,7 +3239,7 @@ function omitNullKeys(fixture: Record<string, unknown>): Record<string, unknown>
 function channelSummary(overrides: Record<string, unknown> = {}): Record<string, unknown> {
   return {
     categories: '',
-    fFmpegProfile: '1080p H.264',
+    ffmpegProfile: '1080p H.264',
     group: 'ChicoryTV',
     id: 1,
     isEnabled: true,
@@ -3259,7 +3259,7 @@ function channelSummary(overrides: Record<string, unknown> = {}): Record<string,
 function channelTemplate(overrides: Record<string, unknown> = {}): Record<string, unknown> {
   return omitNullKeys({
     description: 'General-purpose 1080p H.264.',
-    fFmpegProfileId: 100,
+    ffmpegProfileId: 100,
     fixedStartTimeBehavior: 'Strict',
     id: 10,
     idleBehavior: 'StopOnDisconnect',
diff --git a/web/src/App.tsx b/web/src/App.tsx
index 092942e5f..d6e75683c 100644
--- a/web/src/App.tsx
+++ b/web/src/App.tsx
@@ -1564,7 +1564,7 @@ function ChannelTableRow({
         )}
       </td>
       <td><Badge tone={streamingTone}>{channel.streamingMode}</Badge></td>
-      <td className="ctv-channel-ffmpeg">{channel.fFmpegProfile || 'Unassigned'}</td>
+      <td className="ctv-channel-ffmpeg">{channel.ffmpegProfile || 'Unassigned'}</td>
       <td>
         <div className="ctv-channel-actions">
           <IconButton disabled size="sm" title={`Preview unavailable for ${channel.name}`}>
diff --git a/web/src/api/channels.test.ts b/web/src/api/channels.test.ts
index 0b005762b..81b73e8d6 100644
--- a/web/src/api/channels.test.ts
+++ b/web/src/api/channels.test.ts
@@ -7,7 +7,7 @@ const sampleChannel = {
   name: 'Cartoons',
   group: 'ChicoryTV',
   categories: '',
-  fFmpegProfileId: 1,
+  ffmpegProfileId: 1,
   slugSeconds: null,
   logo: { path: '', contentType: '' },
   streamSelectorMode: 'Default',
diff --git a/web/src/api/generated/v1.d.ts b/web/src/api/generated/v1.d.ts
index 07d8940be..9896c2f9f 100644
--- a/web/src/api/generated/v1.d.ts
+++ b/web/src/api/generated/v1.d.ts
@@ -157,7 +157,7 @@ export interface components {
     "name": string;
     "group": string;
     "categories": string;
-    "fFmpegProfile": string;
+    "ffmpegProfile": string;
     "language": string;
     "streamingMode": string;
     "isEnabled": boolean;
@@ -178,7 +178,7 @@ export interface components {
     "description": string;
     "isSystem": boolean;
     "isDefault": boolean;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "watermarkId": null | number;
     "fallbackFillerId": null | number;
     "preRollFillerId": null | number;
@@ -209,7 +209,7 @@ export interface components {
     "name": null | string;
     "group": null | string;
     "categories": null | string;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "slugSeconds": null | number;
     "logo": components["schemas"]["ArtworkContentTypeModel"];
     "streamSelectorMode": components["schemas"]["ChannelStreamSelectorMode"];
@@ -259,7 +259,7 @@ export interface components {
   };
     "CreateChannelFromLineupAdvancedOptionsRequest": {
     "playbackOrder"?: null | components["schemas"]["PlaybackOrder"];
-    "fFmpegProfileId"?: null | number;
+    "ffmpegProfileId"?: null | number;
     "watermarkId"?: null | number;
     "fallbackFillerId"?: null | number;
     "preRollFillerId"?: null | number;
@@ -316,7 +316,7 @@ export interface components {
     "number": null | string;
     "group": null | string;
     "categories": null | string;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "slugSeconds": null | number;
     "logo": components["schemas"]["ArtworkContentTypeModel"];
     "streamSelectorMode": components["schemas"]["ChannelStreamSelectorMode"];
@@ -343,7 +343,7 @@ export interface components {
     "CreateChannelTemplateRequest": {
     "name": string;
     "description": string;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "watermarkId": null | number;
     "fallbackFillerId": null | number;
     "preRollFillerId": null | number;
@@ -1432,7 +1432,7 @@ export interface components {
     "number": null | string;
     "group": null | string;
     "categories": null | string;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "slugSeconds": null | number;
     "logo": components["schemas"]["ArtworkContentTypeModel"];
     "streamSelectorMode": components["schemas"]["ChannelStreamSelectorMode"];
@@ -1459,7 +1459,7 @@ export interface components {
     "UpdateChannelTemplateRequest": {
     "name": string;
     "description": string;
-    "fFmpegProfileId": number;
+    "ffmpegProfileId": number;
     "watermarkId": null | number;
     "fallbackFillerId": null | number;
     "preRollFillerId": null | number;
diff --git a/web/src/builder/ChannelBuilder.tsx b/web/src/builder/ChannelBuilder.tsx
index aad213d87..85a2b73e1 100644
--- a/web/src/builder/ChannelBuilder.tsx
+++ b/web/src/builder/ChannelBuilder.tsx
@@ -647,7 +647,7 @@ function templatePlaybackOrder(template: ChannelTemplate): PlaybackOrder {
 // Advanced field keys wired into request.advanced (playbackOrder + playoutMode
 // live in dedicated state and are ALWAYS sent, so they are excluded here).
 const ADVANCED_KEYS = [
-  'fFmpegProfileId',
+  'ffmpegProfileId',
   'watermarkId',
   'fallbackFillerId',
   'preRollFillerId',
@@ -1091,7 +1091,7 @@ function ChannelBuilder({
       const requestBody: CreateChannelTemplateRequest = {
         name: saveName.trim(),
         description: saveDesc.trim(),
-        fFmpegProfileId: eff('fFmpegProfileId'),
+        ffmpegProfileId: eff('ffmpegProfileId'),
         watermarkId: eff('watermarkId'),
         fallbackFillerId: eff('fallbackFillerId'),
         preRollFillerId: eff('preRollFillerId'),
@@ -1768,7 +1768,7 @@ function templateChips(
 ): string[] {
   const chips: string[] = [];
   chips.push(STREAMING_MODE_LABELS[template.streamingMode as StreamingMode] ?? template.streamingMode);
-  const profile = ffmpegProfiles.find((candidate) => candidate.id === template.fFmpegProfileId);
+  const profile = ffmpegProfiles.find((candidate) => candidate.id === template.ffmpegProfileId);
   if (profile?.name) {
     chips.push(profile.name);
   }
@@ -1956,15 +1956,15 @@ function AdvancedPanel({
                 <Select
                   size="sm"
                   label="FFmpeg profile"
-                  value={selValue('fFmpegProfileId')}
+                  value={selValue('ffmpegProfileId')}
                   options={[
                     inheritOption(
-                      ffmpegProfiles.find((p) => p.id === template.fFmpegProfileId)?.name ??
-                        `#${template.fFmpegProfileId}`
+                      ffmpegProfiles.find((p) => p.id === template.ffmpegProfileId)?.name ??
+                        `#${template.ffmpegProfileId}`
                     ),
                     ...ffmpegProfiles.map((profile) => ({ value: String(profile.id), label: profile.name ?? `#${profile.id}` }))
                   ]}
-                  onChange={onSelect('fFmpegProfileId', Number)}
+                  onChange={onSelect('ffmpegProfileId', Number)}
                 />
                 <Select
                   size="sm"
@@ -2153,7 +2153,7 @@ function AdvancedPanel({
           ) : (
             <>
               <AdvGroup label="Streaming">
-                <ReadOnlyField label="FFmpeg profile" value={ffmpegProfiles.find((p) => p.id === template.fFmpegProfileId)?.name ?? `#${template.fFmpegProfileId}`} />
+                <ReadOnlyField label="FFmpeg profile" value={ffmpegProfiles.find((p) => p.id === template.ffmpegProfileId)?.name ?? `#${template.ffmpegProfileId}`} />
                 <ReadOnlyField label="Streaming mode" value={STREAMING_MODE_LABELS[template.streamingMode as StreamingMode] ?? template.streamingMode} />
                 <ReadOnlyField label="Transcode mode" value={template.transcodeMode} />
               </AdvGroup>
diff --git a/web/src/screens/ChannelEditScreen.test.tsx b/web/src/screens/ChannelEditScreen.test.tsx
index afa5ea441..e12e0f46c 100644
--- a/web/src/screens/ChannelEditScreen.test.tsx
+++ b/web/src/screens/ChannelEditScreen.test.tsx
@@ -8,7 +8,7 @@ const channel = {
   name: 'Cartoons',
   group: 'ChicoryTV',
   categories: 'Kids',
-  fFmpegProfileId: 1,
+  ffmpegProfileId: 1,
   slugSeconds: null,
   logo: { path: '', contentType: '' },
   streamSelectorMode: 'Default',
diff --git a/web/src/screens/ChannelEditScreen.tsx b/web/src/screens/ChannelEditScreen.tsx
index 44da62e7a..3d1904cb3 100644
--- a/web/src/screens/ChannelEditScreen.tsx
+++ b/web/src/screens/ChannelEditScreen.tsx
@@ -119,7 +119,7 @@ function draftFromChannel(channel: Channel): UpdateChannelRequest {
     number: channel.number,
     group: channel.group,
     categories: channel.categories,
-    fFmpegProfileId: channel.fFmpegProfileId,
+    ffmpegProfileId: channel.ffmpegProfileId,
     slugSeconds: channel.slugSeconds,
     logo: channel.logo,
     streamSelectorMode: channel.streamSelectorMode,
@@ -407,13 +407,13 @@ function StreamingPane({
           <Select
             disabled={hlsDirect}
             fullWidth
-            onChange={(event) => set({ fFmpegProfileId: Number(event.target.value) })}
+            onChange={(event) => set({ ffmpegProfileId: Number(event.target.value) })}
             options={data.ffmpegProfiles.map((profile) => ({
               label: profile.name ?? `Profile ${profile.id}`,
               value: String(profile.id)
             }))}
             size="sm"
-            value={String(draft.fFmpegProfileId)}
+            value={String(draft.ffmpegProfileId)}
           />
         </Row>
         <Row help="Black video / silent audio inserted between every playout item." label="Slug seconds">
diff --git a/web/src/screens/PlaybackTroubleshootingScreen.test.tsx b/web/src/screens/PlaybackTroubleshootingScreen.test.tsx
index 656b0c05c..63f02ed52 100644
--- a/web/src/screens/PlaybackTroubleshootingScreen.test.tsx
+++ b/web/src/screens/PlaybackTroubleshootingScreen.test.tsx
@@ -68,9 +68,10 @@ function installFetch(statusRef: { current: Status }) {
       );
     }
     if (url.startsWith('/api/channels/')) {
-      // Pin the RUNTIME shape, not the OpenAPI-spec shape: the server serializes with Newtonsoft,
-      // so the profile key is "ffmpegProfileId" (the generated types wrongly say "fFmpegProfileId"
-      // — see #198). streamSelectorMode/streamSelector match the spec (no leading acronym).
+      // Pin the runtime shape: the server serializes with Newtonsoft, so the profile key is
+      // "ffmpegProfileId". Since #198 the spec generator mirrors the runtime contract resolver, so
+      // the generated types now agree ("ffmpegProfileId"); this mock stays runtime-shaped to guard
+      // the fix. streamSelectorMode/streamSelector match too (no leading acronym).
       return Promise.resolve(
         json({ id: 7, name: 'Channel Seven', ffmpegProfileId: 2, streamSelectorMode: 'Default', streamSelector: null })
       );
@@ -173,8 +174,9 @@ describe('PlaybackTroubleshootingScreen', () => {
 
     expect(hlsMock.loadSource).toHaveBeenCalledTimes(1);
     const params = new URLSearchParams(String(hlsMock.loadSource.mock.calls[0][0]).split('?')[1]);
-    // The regression this pins: the runtime channel JSON key is ffmpegProfileId (#198); reading the
-    // spec-cased fFmpegProfileId left the profile null and the URL fell back to ffmpegProfile=0.
+    // The regression this pins: the runtime channel JSON key is ffmpegProfileId (#198). Before the
+    // spec was aligned, reading the spec-cased fFmpegProfileId left the profile null and the URL
+    // fell back to ffmpegProfile=0.
     expect(params.get('ffmpegProfile')).toBe('2');
     expect(params.get('channel')).toBe('7');
     expect(params.get('start')).toBe(new Date('2026-07-09T20:00').toISOString());
diff --git a/web/src/screens/PlaybackTroubleshootingScreen.tsx b/web/src/screens/PlaybackTroubleshootingScreen.tsx
index c9782d949..4fd518aee 100644
--- a/web/src/screens/PlaybackTroubleshootingScreen.tsx
+++ b/web/src/screens/PlaybackTroubleshootingScreen.tsx
@@ -302,13 +302,7 @@ export function PlaybackTroubleshootingScreen() {
         // LoadChannel logic).
         let defaultProfileId: null | number = data.profiles[0]?.id ?? null;
         if (mode.kind === 'channel' && data.channel) {
-          // Runtime JSON is Newtonsoft-cased ("ffmpegProfileId"); generated types say
-          // "fFmpegProfileId" — see #198. Read the runtime key first, fall back to the spec key,
-          // then to the first profile; never let this silently become 0.
-          // (streamSelectorMode / streamSelector below have no leading acronym, so their runtime
-          // keys match the generated types — verified against a live GET /api/channels/{id}.)
-          const rawChannel = data.channel as typeof data.channel & { ffmpegProfileId?: null | number };
-          defaultProfileId = rawChannel.ffmpegProfileId ?? data.channel.fFmpegProfileId ?? defaultProfileId;
+          defaultProfileId = data.channel.ffmpegProfileId ?? defaultProfileId;
         }
 
         const isRemoteStream = (data.rawKind ?? '').toLowerCase() === 'remotestream';