diff --git a/src/lib/config/services/project.test.ts b/src/lib/config/services/project.test.ts
index 5618d899..cef14531 100644
--- a/src/lib/config/services/project.test.ts
+++ b/src/lib/config/services/project.test.ts
@@ -56,4 +56,43 @@ describe('loadProjectConfig', () => {
       expect(config.service.endpoint).toBe('http://localhost:11434')
     }
   })
+
+  it('warns instead of throwing when the merged config fails validation', () => {
+    // Reproduces the user-reported crash: the merged config has fields
+    // the schema rejects (often inherited from a stale XDG / git
+    // config layer), and the previous behavior threw, taking down
+    // every coco command. The fix surfaces a warning so the user
+    // can fix the offending field but keeps the merge so the rest
+    // of the tool stays usable.
+    mockFs.existsSync.mockReturnValue(true)
+    // Project file has a valid local override (conventionalCommits)
+    // but the merged result will inherit an invalid service shape
+    // from the incoming `config` argument.
+    mockFs.readFileSync.mockReturnValue(
+      JSON.stringify({ conventionalCommits: true })
+    )
+
+    const invalidIncoming = {
+      service: {
+        // Missing required fields + extra unknown field — guaranteed
+        // to fail any anyOf branch in the service schema.
+        provider: 'openai',
+        model: 'gpt-4o',
+        unknownDriftField: 'something',
+      },
+    } as unknown as Config
+
+    const warnSpy = jest.spyOn(console, 'warn').mockImplementation(() => {})
+
+    expect(() => loadProjectJsonConfig(invalidIncoming)).not.toThrow()
+
+    const result = loadProjectJsonConfig(invalidIncoming)
+    // Local override still merged in despite validation failure —
+    // the tool keeps working with the user's intent applied.
+    expect((result as unknown as { conventionalCommits?: boolean }).conventionalCommits).toBe(true)
+    expect(warnSpy).toHaveBeenCalled()
+    expect(warnSpy.mock.calls[0][0]).toContain('config validation issues detected')
+
+    warnSpy.mockRestore()
+  })
 })
diff --git a/src/lib/config/services/project.ts b/src/lib/config/services/project.ts
index 6377a30c..0566a7c2 100644
--- a/src/lib/config/services/project.ts
+++ b/src/lib/config/services/project.ts
@@ -45,12 +45,46 @@ export function loadProjectJsonConfig<ConfigType = Config>(
       fs.readFileSync(resolvedPath, 'utf-8')
     ) as Partial<Config> & { $schema: string }
 
-    config = { ...config, ...projectConfig } as Config
+    const merged = { ...config, ...projectConfig } as Config
 
-    const isProjectConfigValid = validate(config)
+    // Validate the merged result, but DON'T throw on failure.
+    // Reasons:
+    //
+    //   1. Throwing turns "you have a stale field somewhere in your
+    //      config" into "the whole tool fails to boot" — every coco
+    //      command that loads config crashes. That's a brutal
+    //      regression cost for what's almost always a recoverable
+    //      situation.
+    //
+    //   2. The validation runs on the MERGED config, so the actual
+    //      offending file might be the XDG / git / env layer, not
+    //      the local project file we're nominally loading. Pinning
+    //      the error to "project config" was actively misleading.
+    //
+    //   3. We have sane defaults. A drifted service shape can fall
+    //      back to the default service and the rest of the tool
+    //      keeps working — the user still gets their commits, their
+    //      changelogs, their PR flows, etc.
+    //
+    // Instead: warn loudly to stderr (with the file path AND the
+    // specific schema errors) so the user knows exactly what to fix,
+    // and apply the merge so the user's intent still flows through.
+    // If a downstream component genuinely can't operate without a
+    // valid service shape, it can guard against that locally with a
+    // clear error rather than blowing up at config-load time.
+    const isProjectConfigValid = validate(merged)
     if (!isProjectConfigValid) {
-      throw new Error('Invalid project config', { cause: ajv.errorsText(validate.errors) })
+      const errors = ajv.errorsText(validate.errors)
+      console.warn(
+        `[coco] Warning: config validation issues detected (continuing with merged config).\n` +
+        `  Local file:   ${resolvedPath}\n` +
+        `  Schema issues: ${errors}\n` +
+        `  Fix the offending fields to silence this warning. The validation runs ` +
+        `against the merged result of every config source (defaults, XDG, git, project, env) ` +
+        `— the issue may be in any of those, not necessarily this file.`
+      )
     }
+    config = merged
   }
 
   if (opts?.returnSource) {