diff --git a/.changeset/ignore-obsolete-experiments.md b/.changeset/ignore-obsolete-experiments.md
new file mode 100644
index 000000000..d0b206f7d
--- /dev/null
+++ b/.changeset/ignore-obsolete-experiments.md
@@ -0,0 +1,6 @@
+---
+"@moonshot-ai/agent-core": patch
+"@moonshot-ai/kimi-code": patch
+---
+
+Allow obsolete experimental config entries to remain without blocking startup.
diff --git a/packages/agent-core/src/config/schema.ts b/packages/agent-core/src/config/schema.ts
index 11c6500c7..094239b73 100644
--- a/packages/agent-core/src/config/schema.ts
+++ b/packages/agent-core/src/config/schema.ts
@@ -1,7 +1,6 @@
 import { HOOK_EVENT_TYPES } from '../session/hooks/types';
 import { parsePattern } from '#/agent/permission/matches-rule';
 import { ErrorCodes, KimiError } from '#/errors';
-import { FLAG_DEFINITIONS, type FlagId } from '#/flags/registry';
 import { z } from 'zod';
 
 export const ProviderTypeSchema = z.enum([
@@ -105,20 +104,7 @@ export const BackgroundConfigSchema = z.object({
 
 export type BackgroundConfig = z.infer<typeof BackgroundConfigSchema>;
 
-const ExperimentalFlagIdSet = new Set<string>(FLAG_DEFINITIONS.map((def) => def.id));
-
-export const ExperimentalConfigSchema = z
-  .record(z.string(), z.boolean())
-  .superRefine((config, ctx) => {
-    for (const key of Object.keys(config)) {
-      if (ExperimentalFlagIdSet.has(key)) continue;
-      ctx.addIssue({
-        code: 'custom',
-        path: [key],
-        message: `Unknown experimental feature "${key}".`,
-      });
-    }
-  }) as z.ZodType<Partial<Record<FlagId, boolean>>>;
+export const ExperimentalConfigSchema = z.record(z.string(), z.boolean());
 
 export type ExperimentalConfig = z.infer<typeof ExperimentalConfigSchema>;
 
diff --git a/packages/agent-core/test/config/configs.test.ts b/packages/agent-core/test/config/configs.test.ts
index 551980f9d..dd3bb2eb8 100644
--- a/packages/agent-core/test/config/configs.test.ts
+++ b/packages/agent-core/test/config/configs.test.ts
@@ -279,18 +279,27 @@ micro_compaction = false
     expect(parseConfigString(text, configPath).experimental).toEqual(config.experimental);
   });
 
-  it('rejects unknown experimental feature keys', () => {
-    expectKimiErrorCode(
-      () =>
-        parseConfigString(
-          `
+  it('accepts obsolete experimental feature keys as inert config', async () => {
+    const dir = makeTempDir();
+    const configPath = join(dir, 'obsolete-experimental.toml');
+    const toml = `
 [experimental]
-not_registered = true
-`,
-          'unknown-experimental.toml',
-        ),
-      ErrorCodes.CONFIG_INVALID,
-    );
+legacy_feature = true
+obsolete_feature = false
+removed_flag = true
+`;
+
+    const config = parseConfigString(toml, configPath);
+
+    expect(config.experimental).toEqual({
+      'legacy_feature': true,
+      'obsolete_feature': false,
+      'removed_flag': true,
+    });
+
+    await writeConfigFile(configPath, config);
+    const text = await readFile(configPath, 'utf-8');
+    expect(parseConfigString(text, configPath).experimental).toEqual(config.experimental);
   });
 
   it('loads defaults for absent files and writes typed fields without dropping raw sections', async () => {
diff --git a/packages/agent-core/test/flags/resolver.test.ts b/packages/agent-core/test/flags/resolver.test.ts
index d6bbb698e..85cc6e1e5 100644
--- a/packages/agent-core/test/flags/resolver.test.ts
+++ b/packages/agent-core/test/flags/resolver.test.ts
@@ -106,6 +106,25 @@ describe('FlagResolver', () => {
     expect(resolver.enabled('b-off-default' as FlagId)).toBe(true);
   });
 
+  it('ignores obsolete config override ids outside the registry', () => {
+    const resolver = new FlagResolver({}, DEFS, {
+      'a-on-default': false,
+      'legacy_feature': true,
+    } as never);
+
+    expect(resolver.enabled('a-on-default' as FlagId)).toBe(false);
+    expect(resolver.enabled('legacy_feature' as FlagId)).toBe(false);
+    expect(resolver.snapshot()).toEqual({
+      'a-on-default': false,
+      'b-off-default': false,
+    });
+    expect(resolver.enabledIds()).toEqual([]);
+    expect(resolver.explainAll().map((feature) => feature.id)).toEqual([
+      'a-on-default',
+      'b-off-default',
+    ]);
+  });
+
   it('keeps env precedence above config overrides', () => {
     const resolver = new FlagResolver(
       {