make session config authoritative on reconnect

Author: charlesvien

packages/agent/src/adapters/claude/claude-agent.resume-model.test.ts

@@ -317,6 +317,59 @@ describe("ClaudeAcpAgent session creation", () => {
     },
   );
 
+  // The shared claude settings file is cross-session state: the session's own
+  // pick must win over it, with the file only as a fallback.
+  it.each([
+    {
+      name: "prefers meta.model over the settings file model",
+      sessionId: "0197a000-0000-7000-8000-000000000011",
+      settingsModel: "claude-opus-4-8",
+      model: "claude-fable-5",
+      expectedSetModel: "claude-fable-5",
+      expectedCurrentValue: "claude-fable-5",
+    },
+    {
+      name: "falls back to the settings file model without meta.model",
+      sessionId: "0197a000-0000-7000-8000-000000000012",
+      settingsModel: "claude-fable-5",
+      model: undefined,
+      expectedSetModel: "claude-fable-5",
+      expectedCurrentValue: "claude-fable-5",
+    },
+  ])(
+    "$name",
+    async ({
+      sessionId,
+      settingsModel,
+      model,
+      expectedSetModel,
+      expectedCurrentValue,
+    }) => {
+      const settingsPath = path.join(configDir, "settings.json");
+      writeFileSync(settingsPath, JSON.stringify({ model: settingsModel }));
+      try {
+        const agent = makeAgent();
+
+        const response = await agent.resumeSession({
+          sessionId,
+          cwd,
+          mcpServers: [],
+          _meta: { taskRunId: "run-1", ...(model ? { model } : {}) },
+        });
+
+        expect(createdQueries).toHaveLength(1);
+        expect(createdQueries[0].setModel).toHaveBeenCalledWith(
+          expectedSetModel,
+        );
+        expect(getModelConfigOption(response)?.currentValue).toBe(
+          expectedCurrentValue,
+        );
+      } finally {
+        rmSync(settingsPath, { force: true });
+      }
+    },
+  );
+
   // New sessions pass the model to the SDK at spawn, never via setModel. The
   // Codex-model row guards the desync that surfaced as "picked gpt-5.5, session
   // ran Opus": a non-Anthropic id on the Claude adapter must fall back to the

packages/agent/src/adapters/claude/claude-agent.ts

@@ -1963,8 +1963,10 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
     const settingsManager = new SettingsManager(cwd);
     await settingsManager.initialize();
 
+    // The session's explicit pick outranks the shared claude settings file:
+    // that file is cross-session state and must only ever be a fallback.
     const earlyModelId =
-      settingsManager.getSettings().model || meta?.model || "";
+      meta?.model || settingsManager.getSettings().model || "";
 
     // Register the in-process general local-tools MCP server. Tools self-gate
     // via the registry (e.g. signed-commit is cloud-only and needs a GH token),
@@ -2198,7 +2200,7 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
 
     const [rawModelOptions] = await Promise.all([
       this.getModelConfigOptions(
-        settingsManager.getSettings().model || meta?.model || undefined,
+        meta?.model || settingsManager.getSettings().model || undefined,
         this.options?.gatewayEnv?.anthropicBaseUrl,
         this.options?.gatewayEnv?.anthropicAuthToken,
       ),
@@ -2263,8 +2265,8 @@ export class ClaudeAcpAgent extends BaseAcpAgent {
     }
 
     const resolvedModelId = resolveInitialModelId(modelOptions, [
-      settingsManager.getSettings().model,
       meta?.model,
+      settingsManager.getSettings().model,
     ]);
     session.modelId = resolvedModelId;
     session.lastContextWindowSize =

packages/core/src/sessions/sessionService.ts

@@ -49,6 +49,10 @@ import {
   type Task,
 } from "@posthog/shared/domain-types";
 import type { SpeechKind, SpeechSource } from "../speech/identifiers";
+import {
+  CONTEXT_WINDOW_OPTION_CATEGORY,
+  FAST_MODE_OPTION_CATEGORY,
+} from "../task-detail/previewConfig";
 import {
   isNotification,
   POSTHOG_NOTIFICATIONS,
@@ -2002,6 +2006,33 @@ export class SessionService {
       const persistedModel =
         modelOpt?.type === "select" ? modelOpt.currentValue : undefined;
 
+      // Same for effort, context window and fast mode: the session's own
+      // persisted config is authoritative on resume.
+      const effortOpt = getConfigOptionByCategory(
+        persistedConfigOptions,
+        "thought_level",
+      );
+      const persistedEffort =
+        effortOpt?.type === "select" &&
+        effortLevelSchema.safeParse(effortOpt.currentValue).success
+          ? (effortOpt.currentValue as EffortLevel)
+          : undefined;
+      const contextOpt = getConfigOptionByCategory(
+        persistedConfigOptions,
+        CONTEXT_WINDOW_OPTION_CATEGORY,
+      );
+      const persistedContextWindow =
+        contextOpt?.type === "select" &&
+        (contextOpt.currentValue === "200k" || contextOpt.currentValue === "1m")
+          ? contextOpt.currentValue
+          : undefined;
+      const fastOpt = getConfigOptionByCategory(
+        persistedConfigOptions,
+        FAST_MODE_OPTION_CATEGORY,
+      );
+      const persistedFastMode =
+        fastOpt?.type === "select" ? fastOpt.currentValue === "on" : undefined;
+
       this.d.trpc.workspace.verify
         .query({ taskId })
         .then((workspaceResult) => {
@@ -2037,6 +2068,9 @@ export class SessionService {
         adapter: resolvedAdapter,
         permissionMode: persistedMode,
         model: persistedModel,
+        effort: persistedEffort,
+        contextWindow: persistedContextWindow,
+        fastMode: persistedFastMode,
         customInstructions: customInstructions || undefined,
       });
 

packages/workspace-server/src/services/agent/schemas.ts

@@ -231,6 +231,8 @@ export const reconnectSessionInput = z.object({
   model: z.string().optional(),
   customInstructions: customInstructionsField,
   effort: effortLevelSchema.optional(),
+  contextWindow: z.enum(["200k", "1m"]).optional(),
+  fastMode: z.boolean().optional(),
   jsonSchema: z.record(z.string(), z.unknown()).nullish(),
   /** See startSessionInput.rtkEnabled. */
   rtkEnabled: z.boolean().optional(),