Widen model config to use JSON primitive

CHANGELOG.md

@@ -34,6 +34,7 @@ changes accumulate. Track in-flight protocol changes via PRs touching
 ### Changed
 
 - `ConfigPropertySchema.enum` now accepts `JsonPrimitive[]` instead of `string[]`, allowing numeric, boolean, and null enum values.
+- `ModelSelection.config` values are now `JsonPrimitive` (`string | number | boolean | null`) instead of `string`, allowing numeric, boolean, and null configuration values.
 
 ## [0.5.0] — Unreleased
 

clients/go/CHANGELOG.md

@@ -25,6 +25,8 @@ tag whose matching `## [X.Y.Z]` heading is missing from this file.
 
 - `ConfigPropertySchema.Enum` field is now `[]json.RawMessage` instead of `[]string`,
   allowing numeric, boolean, and null enum values.
+- `ModelSelection.Config` values are now `json.RawMessage` instead of `string`,
+  allowing numeric, boolean, and null configuration values.
 
 ## [0.4.0] — 2026-06-19
 

clients/go/ahptypes/state.generated.go

@@ -564,8 +564,10 @@ type SessionModelInfo struct {
 type ModelSelection struct {
 	// Model identifier
 	Id string `json:"id"`
-	// Model-specific configuration values
-	Config map[string]string `json:"config,omitempty"`
+	// Model-specific configuration values. Values are JSON primitives: most
+	// pickers produce strings, but some (e.g. a numeric context-size picker)
+	// produce numbers or booleans, which are carried through as-is.
+	Config map[string]json.RawMessage `json:"config,omitempty"`
 }
 
 // A selected custom agent for a session.

clients/kotlin/CHANGELOG.md

@@ -26,6 +26,8 @@ versions (`*-SNAPSHOT`) are explicitly rejected by the publish pipeline; bump
 
 - `ConfigPropertySchema.enum` field is now `List<JsonElement>?` instead of
   `List<String>?`, allowing numeric, boolean, and null enum values.
+- `ModelSelection.config` values are now `JsonElement` instead of `String`,
+  allowing numeric, boolean, and null configuration values.
 
 ## [0.4.0] — 2026-06-19
 

clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/State.generated.kt

@@ -933,9 +933,11 @@ data class ModelSelection(
      */
     val id: String,
     /**
-     * Model-specific configuration values
+     * Model-specific configuration values. Values are JSON primitives: most
+     * pickers produce strings, but some (e.g. a numeric context-size picker)
+     * produce numbers or booleans, which are carried through as-is.
      */
-    val config: Map<String, String>? = null
+    val config: Map<String, JsonElement>? = null
 )
 
 @Serializable

clients/rust/CHANGELOG.md

@@ -34,6 +34,8 @@ matching `## [X.Y.Z]` heading is missing from this file.
   on `ahp-ws` with `default-features = false, features = ["native-tls"]`.
 - `ConfigPropertySchema.enum` field is now `Option<Vec<AnyValue>>` instead of
   `Option<Vec<String>>`, allowing numeric, boolean, and null enum values.
+- `ModelSelection.config` values are now `AnyValue` instead of `String`,
+  allowing numeric, boolean, and null configuration values.
 
 ## [0.4.0] — 2026-06-19
 

clients/rust/crates/ahp-types/src/state.rs

@@ -783,9 +783,11 @@ pub struct SessionModelInfo {
 pub struct ModelSelection {
     /// Model identifier
     pub id: String,
-    /// Model-specific configuration values
+    /// Model-specific configuration values. Values are JSON primitives: most
+    /// pickers produce strings, but some (e.g. a numeric context-size picker)
+    /// produce numbers or booleans, which are carried through as-is.
     #[serde(default, skip_serializing_if = "Option::is_none")]
-    pub config: Option<std::collections::HashMap<String, String>>,
+    pub config: Option<std::collections::HashMap<String, AnyValue>>,
 }
 
 /// A selected custom agent for a session.

clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/State.generated.swift

@@ -655,12 +655,14 @@ public struct SessionModelInfo: Codable, Sendable {
 public struct ModelSelection: Codable, Sendable {
     /// Model identifier
     public var id: String
-    /// Model-specific configuration values
-    public var config: [String: String]?
+    /// Model-specific configuration values. Values are JSON primitives: most
+    /// pickers produce strings, but some (e.g. a numeric context-size picker)
+    /// produce numbers or booleans, which are carried through as-is.
+    public var config: [String: AnyCodable]?
 
     public init(
         id: String,
-        config: [String: String]? = nil
+        config: [String: AnyCodable]? = nil
     ) {
         self.id = id
         self.config = config

clients/swift/CHANGELOG.md

@@ -28,6 +28,8 @@ the tag matches the version pinned in [`VERSION`](VERSION).
 
 - `ConfigPropertySchema.enum` field is now `[AnyCodable]?` instead of
   `[String]?`, allowing numeric, boolean, and null enum values.
+- `ModelSelection.config` values are now `AnyCodable` instead of `String`,
+  allowing numeric, boolean, and null configuration values.
 
 ## [0.4.0] — 2026-06-19
 

clients/typescript/CHANGELOG.md

@@ -32,6 +32,8 @@ hotfix escape hatch.
 
 - `ConfigPropertySchema.enum` field is now `JsonPrimitive[]` instead of
   `string[]`, allowing numeric, boolean, and null enum values.
+- `ModelSelection.config` values are now `JsonPrimitive` instead of `string`,
+  allowing numeric, boolean, and null configuration values.
 
 ### Fixed
 

schema/actions.schema.json

@@ -2484,9 +2484,9 @@
         "config": {
           "type": "object",
           "additionalProperties": {
-            "type": "string"
+            "$ref": "#/$defs/JsonPrimitive"
           },
-          "description": "Model-specific configuration values"
+          "description": "Model-specific configuration values. Values are JSON primitives: most\npickers produce strings, but some (e.g. a numeric context-size picker)\nproduce numbers or booleans, which are carried through as-is."
         }
       },
       "required": [

schema/commands.schema.json

@@ -1822,9 +1822,9 @@
         "config": {
           "type": "object",
           "additionalProperties": {
-            "type": "string"
+            "$ref": "#/$defs/JsonPrimitive"
           },
-          "description": "Model-specific configuration values"
+          "description": "Model-specific configuration values. Values are JSON primitives: most\npickers produce strings, but some (e.g. a numeric context-size picker)\nproduce numbers or booleans, which are carried through as-is."
         }
       },
       "required": [

schema/errors.schema.json

@@ -674,9 +674,9 @@
         "config": {
           "type": "object",
           "additionalProperties": {
-            "type": "string"
+            "$ref": "#/$defs/JsonPrimitive"
           },
-          "description": "Model-specific configuration values"
+          "description": "Model-specific configuration values. Values are JSON primitives: most\npickers produce strings, but some (e.g. a numeric context-size picker)\nproduce numbers or booleans, which are carried through as-is."
         }
       },
       "required": [

schema/notifications.schema.json

@@ -808,9 +808,9 @@
         "config": {
           "type": "object",
           "additionalProperties": {
-            "type": "string"
+            "$ref": "#/$defs/JsonPrimitive"
           },
-          "description": "Model-specific configuration values"
+          "description": "Model-specific configuration values. Values are JSON primitives: most\npickers produce strings, but some (e.g. a numeric context-size picker)\nproduce numbers or booleans, which are carried through as-is."
         }
       },
       "required": [

schema/state.schema.json

@@ -585,9 +585,9 @@
         "config": {
           "type": "object",
           "additionalProperties": {
-            "type": "string"
+            "$ref": "#/$defs/JsonPrimitive"
           },
-          "description": "Model-specific configuration values"
+          "description": "Model-specific configuration values. Values are JSON primitives: most\npickers produce strings, but some (e.g. a numeric context-size picker)\nproduce numbers or booleans, which are carried through as-is."
         }
       },
       "required": [

types/channels-root/state.ts

@@ -6,6 +6,7 @@
 
 import type {
   ConfigSchema,
+  JsonPrimitive,
   ProtectedResourceMetadata,
 } from '../common/state.js';
 import type { TerminalInfo } from '../channels-terminal/state.js';
@@ -131,8 +132,12 @@ export interface SessionModelInfo {
 export interface ModelSelection {
   /** Model identifier */
   id: string;
-  /** Model-specific configuration values */
-  config?: Record<string, string>;
+  /**
+   * Model-specific configuration values. Values are JSON primitives: most
+   * pickers produce strings, but some (e.g. a numeric context-size picker)
+   * produce numbers or booleans, which are carried through as-is.
+   */
+  config?: Record<string, JsonPrimitive>;
 }
 
 // ─── Root Config Types ───────────────────────────────────────────────────────