feat(chat): surface per-model reasoning capabilities (#946) (#951)

Add ModelCapabilities (capabilities: Map<String, ModelCapabilities>?)
to ModelProvider matching backend /api/model/options shape
{model: {fast, reasoning, can_disable_reasoning}}. Nullable/defaulted
for backward compat with old backends (ignoreUnknownKeys+SnakeCase).

Chat composer: gate reasoning dropdown on can_disable_reasoning and
supportsReasoning — "None" disabled with "reasoning always on" hint
when can_disable==false, chip disabled with "No reasoning" when
reasoning==false. Missing keys offer full scale.

Sync currentModelCapabilities from cachedModelOptions on
SessionInfo, resume, preload/refresh, and optimistic /model swap;
clear on resetSessionState. Used by ComposerToolbar via ChatScreen.

Model picker: surface same hints in ModelPickerDialog (pinned+all)
and ModelScreen ProviderCard.

Verified: ktlintCheck OK, compileDebugKotlin OK (rerun-tasks).

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatScreen.kt

@@ -760,6 +760,8 @@ fun ChatScreen(
                 reasoningLevel = state.reasoningLevel,
                 onModelTap = { viewModel.openModelPicker() },
                 onReasoningTap = { level -> viewModel.setReasoningLevel(level) },
+                canDisableReasoning = state.currentModelCapabilities?.can_disable_reasoning,
+                supportsReasoning = state.currentModelCapabilities?.reasoning,
             )
         }
 

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatViewModel.kt

@@ -12,6 +12,7 @@ import com.m57.hermescontrol.data.local.HermesDatabase
 import com.m57.hermescontrol.data.local.SlashUsageStore
 import com.m57.hermescontrol.data.model.Attachment
 import com.m57.hermescontrol.data.model.AttachmentSource
+import com.m57.hermescontrol.data.model.ModelCapabilities
 import com.m57.hermescontrol.data.model.ModelProvider
 import com.m57.hermescontrol.data.model.PinnedModel
 import com.m57.hermescontrol.data.model.SessionMessage
@@ -291,6 +292,9 @@ data class ChatUiState(
     val modelPickerLoading: Boolean = false,
     // Current session's active model label (provider/model), shown in the chip
     val currentSessionModel: String? = null,
+    // Per-model reasoning capabilities for the current session's model
+    // (issue #946). Null when unknown — UI offers full scale.
+    val currentModelCapabilities: ModelCapabilities? = null,
     // Reasoning effort level for the current session
     val reasoningLevel: String? = null,
     val terminalBackend: String? = null,
@@ -810,6 +814,7 @@ class ChatViewModel(
                             fullContextTokens = if (modelSwapped) null else state.fullContextTokens,
                         )
                     }
+                    syncCurrentModelCapabilities()
                     if (modelSwapped) {
                         // Issue #817: after a swap the REST model/info window is
                         // PROFILE-scoped and may describe the old model (e.g. a
@@ -1070,6 +1075,7 @@ class ChatViewModel(
                         terminalBackend = terminalBackend ?: it.terminalBackend,
                     )
                 }
+                syncCurrentModelCapabilities()
                 // Mirror the active runtime session id app-wide (issue #532).
                 ActiveSessionHolder.set(runtimeSessionId ?: sessionId, sessionId)
                 addSystemMessage("Session resumed")
@@ -1836,6 +1842,7 @@ class ChatViewModel(
             if (result is NetworkResult.Success) {
                 cachedModelOptions = result.data.providers.orEmpty()
                 _uiState.update { it.copy(modelPickerPinned = AuthManager.getPinnedModels()) }
+                syncCurrentModelCapabilities()
             }
         }
     }
@@ -1878,6 +1885,7 @@ class ChatViewModel(
                             modelPickerLoading = false,
                         )
                     }
+                    syncCurrentModelCapabilities()
                 }
 
                 is NetworkResult.Failure -> {
@@ -1932,6 +1940,7 @@ class ChatViewModel(
                 currentSessionModel = "$provider/$model",
             )
         }
+        syncCurrentModelCapabilities()
         // Model switch changes the context-window denominator — refetch it.
         fetchContextUsage()
         handleSlashCommand("/model $model --provider $provider --session")
@@ -1963,6 +1972,40 @@ class ChatViewModel(
         }
     }
 
+    fun getModelCapabilities(
+        providerSlug: String,
+        modelName: String,
+    ): ModelCapabilities? = cachedModelOptions.find { it.slug == providerSlug }?.capabilities?.get(modelName)
+
+    fun getCurrentModelCapabilities(): ModelCapabilities? {
+        val label = _uiState.value.currentSessionModel ?: return null
+        val idx = label.indexOf('/')
+        if (idx <= 0) return null
+        val provider = label.substring(0, idx)
+        val model = label.substring(idx + 1)
+        return getModelCapabilities(provider, model)
+    }
+
+    private fun syncCurrentModelCapabilities() {
+        val label = _uiState.value.currentSessionModel
+        val caps =
+            if (label == null) {
+                null
+            } else {
+                val idx = label.indexOf('/')
+                if (idx <= 0) {
+                    null
+                } else {
+                    val provider = label.substring(0, idx)
+                    val model = label.substring(idx + 1)
+                    cachedModelOptions.find { it.slug == provider }?.capabilities?.get(model)
+                }
+            }
+        _uiState.update { state ->
+            if (state.currentModelCapabilities != caps) state.copy(currentModelCapabilities = caps) else state
+        }
+    }
+
     fun switchSession(sessionId: String) {
         if (sessionId == _uiState.value.currentSessionId) return
 
@@ -2167,6 +2210,7 @@ class ChatViewModel(
                 showModelPicker = false,
                 modelPickerLoading = false,
                 currentSessionModel = null,
+                currentModelCapabilities = null,
                 reasoningLevel = null,
                 terminalBackend = null,
                 usedContextTokens = null,

app/src/main/java/com/m57/hermescontrol/ui/chat/components/ChatComposer.kt

@@ -89,6 +89,8 @@ fun ChatInputBar(
     reasoningLevel: String? = null,
     onModelTap: () -> Unit = {},
     onReasoningTap: (String?) -> Unit = {},
+    canDisableReasoning: Boolean? = null,
+    supportsReasoning: Boolean? = null,
 ) {
     // Allow sending while the agent is mid-turn or awaiting approval: the
     // gateway's prompt.submit busy-input policy queues it as the next turn
@@ -319,6 +321,8 @@ fun ChatInputBar(
                     onReasoningSelected = onReasoningTap,
                     onMicTap = onMicTap,
                     modifier = Modifier.testTag("chat_composer_toolbar"),
+                    canDisableReasoning = canDisableReasoning,
+                    supportsReasoning = supportsReasoning,
                 )
 
                 // Attachment dropdown (anchored to the attach button in ComposerToolbar)

app/src/main/java/com/m57/hermescontrol/ui/chat/components/ComposerToolbar.kt

@@ -41,6 +41,11 @@ import com.m57.hermescontrol.R
  * Layout: [📎 attach] [model chip] [←spacer→] [🧠 reasoning] [🎙 mic]
  *
  * The reasoning chip opens a dropdown menu to pick a level (instead of cycling).
+ * When [canDisableReasoning] is false the "None" level is disabled with a
+ * "reasoning always on" hint (issue #946). Absent key (null) means no
+ * restriction is known — full scale offered.
+ * When [supportsReasoning] is false the model takes no reasoning parameter
+ * and the chip is disabled.
  */
 @Composable
 fun ComposerToolbar(
@@ -53,8 +58,12 @@ fun ComposerToolbar(
     onReasoningSelected: (String?) -> Unit,
     onMicTap: () -> Unit,
     modifier: Modifier = Modifier,
+    canDisableReasoning: Boolean? = null,
+    supportsReasoning: Boolean? = null,
 ) {
     var showReasoningMenu by remember { mutableStateOf(false) }
+    val reasoningDisabledForModel = supportsReasoning == false
+    val canDisable = canDisableReasoning
 
     Row(
         modifier =
@@ -105,9 +114,15 @@ fun ComposerToolbar(
             FilterChip(
                 selected = reasoningLevel != null,
                 onClick = { showReasoningMenu = true },
+                enabled = !reasoningDisabledForModel,
                 label = {
                     Text(
-                        text = buildReasoningLabel(reasoningLevel),
+                        text =
+                            if (reasoningDisabledForModel) {
+                                "No reasoning"
+                            } else {
+                                buildReasoningLabel(reasoningLevel)
+                            },
                         style = MaterialTheme.typography.bodySmall,
                         maxLines = 1,
                         overflow = TextOverflow.Ellipsis,
@@ -129,6 +144,22 @@ fun ComposerToolbar(
                     color = MaterialTheme.colorScheme.onSurfaceVariant,
                     modifier = Modifier.padding(horizontal = 12.dp, vertical = 6.dp),
                 )
+                if (canDisable == false) {
+                    Text(
+                        text = "reasoning always on",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = 0.7f),
+                        modifier = Modifier.padding(horizontal = 12.dp, vertical = 2.dp),
+                    )
+                }
+                if (reasoningDisabledForModel) {
+                    Text(
+                        text = "no reasoning parameter for this model",
+                        style = MaterialTheme.typography.labelSmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = 0.7f),
+                        modifier = Modifier.padding(horizontal = 12.dp, vertical = 2.dp),
+                    )
+                }
                 HorizontalDivider()
                 val allLevels =
                     listOf(
@@ -142,6 +173,8 @@ fun ComposerToolbar(
                         "ultra" to "Ultra",
                     )
                 allLevels.forEach { (level, label) ->
+                    val isNone = level == "none"
+                    val noneDisabled = isNone && (canDisable == false || reasoningDisabledForModel)
                     DropdownMenuItem(
                         text = {
                             Text(
@@ -153,10 +186,10 @@ fun ComposerToolbar(
                                         null
                                     },
                                 color =
-                                    if (reasoningLevel == level) {
-                                        MaterialTheme.colorScheme.primary
-                                    } else {
-                                        MaterialTheme.colorScheme.onSurface
+                                    when {
+                                        noneDisabled -> MaterialTheme.colorScheme.onSurface.copy(alpha = 0.38f)
+                                        reasoningLevel == level -> MaterialTheme.colorScheme.primary
+                                        else -> MaterialTheme.colorScheme.onSurface
                                     },
                             )
                         },
@@ -164,6 +197,7 @@ fun ComposerToolbar(
                             showReasoningMenu = false
                             onReasoningSelected(level)
                         },
+                        enabled = !noneDisabled && !reasoningDisabledForModel,
                     )
                 }
             }

app/src/main/java/com/m57/hermescontrol/ui/model/ModelScreen.kt

@@ -782,6 +782,7 @@ private fun ProviderCard(
                             val isActive =
                                 activeProfile?.provider == provider.slug &&
                                     activeProfile.model == model
+                            val caps = provider.capabilities?.get(model)
                             Card(
                                 onClick = { onModelClick(provider.slug, model) },
                                 modifier = Modifier.fillMaxWidth().padding(vertical = 4.dp),
@@ -810,21 +811,37 @@ private fun ProviderCard(
                                     horizontalArrangement = Arrangement.SpaceBetween,
                                     verticalAlignment = Alignment.CenterVertically,
                                 ) {
-                                    Text(
-                                        text = model,
-                                        style = MaterialTheme.typography.bodyMedium,
-                                        fontWeight = if (isActive) FontWeight.Bold else FontWeight.Normal,
-                                        color =
-                                            if (isActive) {
-                                                MaterialTheme.colorScheme.onPrimaryContainer
-                                            } else {
-                                                MaterialTheme.colorScheme.onSurface
-                                            },
-                                        // Weight + wrap: a long model name grows
-                                        // the row vertically instead of pushing
-                                        // the check/pin buttons off-screen.
+                                    Column(
                                         modifier = Modifier.weight(1f),
-                                    )
+                                    ) {
+                                        Text(
+                                            text = model,
+                                            style = MaterialTheme.typography.bodyMedium,
+                                            fontWeight = if (isActive) FontWeight.Bold else FontWeight.Normal,
+                                            color =
+                                                if (isActive) {
+                                                    MaterialTheme.colorScheme.onPrimaryContainer
+                                                } else {
+                                                    MaterialTheme.colorScheme.onSurface
+                                                },
+                                            // Weight + wrap: a long model name grows
+                                            // the row vertically instead of pushing
+                                            // the check/pin buttons off-screen.
+                                        )
+                                        val hint =
+                                            when {
+                                                caps?.reasoning == false -> "no reasoning"
+                                                caps?.can_disable_reasoning == false -> "reasoning always on"
+                                                else -> null
+                                            }
+                                        if (hint != null) {
+                                            Text(
+                                                text = hint,
+                                                style = MaterialTheme.typography.labelSmall,
+                                                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                                            )
+                                        }
+                                    }
                                     Row(
                                         verticalAlignment = Alignment.CenterVertically,
                                         horizontalArrangement = Arrangement.spacedBy(8.dp),

app/src/main/java/com/m57/hermescontrol/ui/model/components/ModelPickerDialog.kt

@@ -50,6 +50,9 @@ import com.m57.hermescontrol.ui.common.SearchBar
  * [pinnedModels] renders a pinned section at the top (mirrors the global model
  * screen's pin section) so frequently-used models are one tap away.
  * [onPinToggle] allows pinning and unpinning models directly inside the dialog.
+ * Per-model reasoning capabilities (issue #946) are surfaced as a small hint
+ * when `can_disable_reasoning == false` ("reasoning always on") or
+ * `reasoning == false` ("no reasoning").
  */
 @Composable
 fun ModelPickerDialog(
@@ -123,6 +126,11 @@ fun ModelPickerDialog(
                             pinnedModels.map { "${it.providerSlug}:${it.modelName}" }.toSet()
                         }
 
+                    val providerBySlug =
+                        remember(providers) {
+                            providers.associateBy { it.slug }
+                        }
+
                     val filteredProvidersWithModels =
                         remember(pickerQuery, providers) {
                             providers.mapNotNull { provider ->
@@ -178,6 +186,7 @@ fun ModelPickerDialog(
                                 filteredPinned,
                                 key = { "pinned:${it.providerSlug}:${it.modelName}" },
                             ) { pinned ->
+                                val caps = providerBySlug[pinned.providerSlug]?.capabilities?.get(pinned.modelName)
                                 ModelItemCard(
                                     modelName = pinned.modelName,
                                     isPinned = true,
@@ -188,6 +197,8 @@ fun ModelPickerDialog(
                                             null
                                         },
                                     onClick = { onSelect(pinned.providerSlug, pinned.modelName) },
+                                    canDisableReasoning = caps?.can_disable_reasoning,
+                                    supportsReasoning = caps?.reasoning,
                                 )
                             }
                         }
@@ -219,6 +230,7 @@ fun ModelPickerDialog(
                                 key = { model -> "${provider.slug}:$model" },
                             ) { model ->
                                 val isPinned = "${provider.slug}:$model" in pinnedSet
+                                val caps = provider.capabilities?.get(model)
                                 ModelItemCard(
                                     modelName = model,
                                     isPinned = isPinned,
@@ -229,6 +241,8 @@ fun ModelPickerDialog(
                                             null
                                         },
                                     onClick = { onSelect(provider.slug, model) },
+                                    canDisableReasoning = caps?.can_disable_reasoning,
+                                    supportsReasoning = caps?.reasoning,
                                 )
                             }
                         }
@@ -247,6 +261,8 @@ private fun ModelItemCard(
     onPinToggle: (() -> Unit)?,
     onClick: () -> Unit,
     modifier: Modifier = Modifier,
+    canDisableReasoning: Boolean? = null,
+    supportsReasoning: Boolean? = null,
 ) {
     Surface(
         modifier =
@@ -267,15 +283,31 @@ private fun ModelItemCard(
             modifier = Modifier.padding(start = 12.dp, end = 4.dp, top = 4.dp, bottom = 4.dp),
             verticalAlignment = Alignment.CenterVertically,
         ) {
-            Text(
-                text = modelName,
-                style = MaterialTheme.typography.bodyMedium,
-                fontWeight = FontWeight.Medium,
-                color = MaterialTheme.colorScheme.onSurface,
-                // No maxLines/ellipsis: a long model name wraps so the full
-                // name stays readable while the pin button keeps its spot.
+            Column(
                 modifier = Modifier.weight(1f),
-            )
+            ) {
+                Text(
+                    text = modelName,
+                    style = MaterialTheme.typography.bodyMedium,
+                    fontWeight = FontWeight.Medium,
+                    color = MaterialTheme.colorScheme.onSurface,
+                    // No maxLines/ellipsis: a long model name wraps so the full
+                    // name stays readable while the pin button keeps its spot.
+                )
+                val hint =
+                    when {
+                        supportsReasoning == false -> "no reasoning"
+                        canDisableReasoning == false -> "reasoning always on"
+                        else -> null
+                    }
+                if (hint != null) {
+                    Text(
+                        text = hint,
+                        style = MaterialTheme.typography.labelSmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+            }
             if (onPinToggle != null) {
                 IconButton(
                     onClick = onPinToggle,