revert: stop forwarding the Small Model override into the managed OpenCode config

Reverts #2687. In real use the injected small_model behaves poorly with
OpenCode: its internal small-model consumers and OpenChamber's own small
model are different things and must stay configured separately.

packages/web/server/index.js

@@ -76,7 +76,6 @@ import { configureOpenCodeRuntimeProviders, resetOpenCodeRuntimeProviders } from
 import { createOpenCodeWatcherRuntime } from './lib/opencode/watcher.js';
 import { createSessionAssistRuntime } from './lib/session-assist/runtime.js';
 import { createSessionGoalRuntime } from './lib/session-goal/runtime.js';
-import { applySmallModelOverrideToOpenCodeConfig } from './lib/small-model/config-injection.js';
 import { createContextObligatoryRuntime } from './lib/context-obligatory/runtime.js';
 import { createSessionKnowledgeRuntime } from './lib/session-knowledge/runtime.js';
 import { createScheduledTasksRuntime } from './lib/scheduled-tasks/runtime.js';
@@ -1205,25 +1204,11 @@ const openCodeLifecycleRuntime = createOpenCodeLifecycleRuntime({
     const managedEnv = includeControl || includeWeb || includeMemory
       ? await (agentToolRuntime?.prepareManagedOpenCodeEnv({ includeControl, includeWeb, includeMemory }) || {})
       : {};
-    const envWithSystemPrompt = settings?.optimizeSystemPrompt === true
-      ? {
-          ...managedEnv,
-          ...(await systemPromptRuntime.prepareManagedOpenCodeEnv(
-            managedEnv.OPENCODE_CONFIG_CONTENT ?? process.env.OPENCODE_CONFIG_CONTENT,
-          )),
-        }
-      : managedEnv;
+    if (settings?.optimizeSystemPrompt !== true) return managedEnv;
 
-    // Apply the explicit Small Model override to the managed OpenCode config
-    // so OpenCode's own title/summary generation uses the user's chosen model.
-    const configContent = envWithSystemPrompt.OPENCODE_CONFIG_CONTENT ?? process.env.OPENCODE_CONFIG_CONTENT;
-    const withSmallModel = applySmallModelOverrideToOpenCodeConfig({
-      configContent,
-      smallModelUseDefault: settings?.smallModelUseDefault,
-      smallModelOverride: settings?.smallModelOverride,
-    });
-    if (withSmallModel === configContent) return envWithSystemPrompt;
-    return { ...envWithSystemPrompt, OPENCODE_CONFIG_CONTENT: withSmallModel };
+    const configContent = managedEnv.OPENCODE_CONFIG_CONTENT ?? process.env.OPENCODE_CONFIG_CONTENT;
+    const systemPromptEnv = await systemPromptRuntime.prepareManagedOpenCodeEnv(configContent);
+    return { ...managedEnv, ...systemPromptEnv };
   },
 });
 

packages/web/server/lib/small-model/DOCUMENTATION.md

@@ -137,20 +137,6 @@ other runtime API.
 - `routes.js` — `GET /api/small-model` (resolution preview) and
   `POST /api/small-model/generate` (`{ prompt, system?, maxOutputTokens?,
   model?, directory? }` → `{ text, providerID, modelID, source }`).
-- `config-injection.js` — applies the Settings → Chat → Small Model override
-  to the config injected into the **managed OpenCode process**
-  (`OPENCODE_CONFIG_CONTENT`), so OpenCode's own internal `small_model`
-  consumers — session title and summary generation — use the user's explicit
-  choice instead of OpenCode's fallback chain. Only an explicit override
-  (`smallModelUseDefault === false` with a non-empty `smallModelOverride`) is
-  injected; "use default" leaves the config untouched so OpenCode's own
-  resolution stays authoritative. Wired into `getManagedOpenCodeEnv` in
-  `server/index.js`; the pure helper is unit-tested in
-  `config-injection.test.js`. External OpenCode servers are unaffected (they
-  are not launched with this env). The injected `small_model` is baked into
-  `OPENCODE_CONFIG_CONTENT` when the managed process spawns, so changing the
-  override in Settings applies on the next managed OpenCode restart, not to
-  the process already running.
 
 ## Which providers the pickers may offer
 

packages/web/server/lib/small-model/config-injection.js

@@ -1,51 +0,0 @@
-/**
- * Applies the user's explicit Small Model override (Settings → Chat → Small
- * Model) to the configuration injected into the managed OpenCode process.
- *
- * OpenCode's own session-title and summary generation reads `small_model`
- * from its config layers. Previously the OpenChamber settings override only
- * fed OpenChamber's own `/api/small-model/generate` utility service, so a
- * configured Small Model never reached OpenCode's title generation and
- * sessions kept their fallback/untitled state. Injecting the override as
- * `small_model` in the managed `OPENCODE_CONFIG_CONTENT` closes that gap for
- * the managed server.
- *
- * Only an explicit override applies (`smallModelUseDefault === false` with a
- * non-empty `smallModelOverride`). "Use default" leaves the config untouched,
- * so OpenCode's own resolution chain (config `small_model`, then its family
- * scan) stays authoritative — this mirrors the precedence documented in
- * `packages/web/server/lib/small-model/DOCUMENTATION.md`.
- *
- * Malformed user config is left untouched rather than rewritten: OpenCode's
- * own loader is the right place to surface it, and silently rewriting it
- * would hide the error.
- */
-export const applySmallModelOverrideToOpenCodeConfig = ({
-  configContent,
-  smallModelUseDefault,
-  smallModelOverride,
-}) => {
-  if (smallModelUseDefault !== false) {
-    return configContent;
-  }
-  const override = typeof smallModelOverride === 'string' ? smallModelOverride.trim() : '';
-  if (!override) {
-    return configContent;
-  }
-
-  const current = (() => {
-    if (typeof configContent !== 'string' || configContent.trim().length === 0) {
-      return {};
-    }
-    try {
-      return JSON.parse(configContent);
-    } catch {
-      return null;
-    }
-  })();
-  if (current === null || typeof current !== 'object' || Array.isArray(current)) {
-    return configContent;
-  }
-
-  return JSON.stringify({ ...current, small_model: override });
-};

packages/web/server/lib/small-model/config-injection.test.js

@@ -1,90 +0,0 @@
-import { describe, expect, it } from 'vitest';
-import { applySmallModelOverrideToOpenCodeConfig } from './config-injection.js';
-
-describe('applySmallModelOverrideToOpenCodeConfig', () => {
-  it('leaves config unchanged when use-default is not explicitly disabled', () => {
-    const config = '{"model":"anthropic/claude-sonnet-4-5"}';
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: config,
-        smallModelUseDefault: true,
-        smallModelOverride: 'anthropic/claude-haiku-4-5',
-      }),
-    ).toBe(config);
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: config,
-        smallModelUseDefault: undefined,
-        smallModelOverride: 'anthropic/claude-haiku-4-5',
-      }),
-    ).toBe(config);
-  });
-
-  it('leaves config unchanged when the override is empty or whitespace', () => {
-    const config = '{"model":"anthropic/claude-sonnet-4-5"}';
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: config,
-        smallModelUseDefault: false,
-        smallModelOverride: '   ',
-      }),
-    ).toBe(config);
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: config,
-        smallModelUseDefault: false,
-        smallModelOverride: undefined,
-      }),
-    ).toBe(config);
-  });
-
-  it('injects small_model into an empty config', () => {
-    const result = applySmallModelOverrideToOpenCodeConfig({
-      configContent: undefined,
-      smallModelUseDefault: false,
-      smallModelOverride: 'anthropic/claude-haiku-4-5',
-    });
-    expect(JSON.parse(result)).toEqual({ small_model: 'anthropic/claude-haiku-4-5' });
-  });
-
-  it('injects small_model while preserving existing config keys and plugins', () => {
-    const result = applySmallModelOverrideToOpenCodeConfig({
-      configContent: '{"model":"anthropic/claude-sonnet-4-5","plugin":["file:///tool.js"]}',
-      smallModelUseDefault: false,
-      smallModelOverride: 'google/gemini-2.5-flash',
-    });
-    expect(JSON.parse(result)).toEqual({
-      model: 'anthropic/claude-sonnet-4-5',
-      plugin: ['file:///tool.js'],
-      small_model: 'google/gemini-2.5-flash',
-    });
-  });
-
-  it('replaces an existing small_model with the override', () => {
-    const result = applySmallModelOverrideToOpenCodeConfig({
-      configContent: '{"small_model":"anthropic/claude-haiku-4-5"}',
-      smallModelUseDefault: false,
-      smallModelOverride: 'google/gemini-2.5-flash',
-    });
-    expect(JSON.parse(result)).toEqual({ small_model: 'google/gemini-2.5-flash' });
-  });
-
-  it('leaves malformed config untouched instead of rewriting it', () => {
-    const config = '{not-valid-json';
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: config,
-        smallModelUseDefault: false,
-        smallModelOverride: 'anthropic/claude-haiku-4-5',
-      }),
-    ).toBe(config);
-    const arrayConfig = '["not","an","object"]';
-    expect(
-      applySmallModelOverrideToOpenCodeConfig({
-        configContent: arrayConfig,
-        smallModelUseDefault: false,
-        smallModelOverride: 'anthropic/claude-haiku-4-5',
-      }),
-    ).toBe(arrayConfig);
-  });
-});