fix(codex): preview joined migration TOML repair

Closes #1635

tests/unit/shared/toml-object.test.ts

@@ -0,0 +1,123 @@
+import { describe, expect, it } from 'bun:test';
+
+import {
+  parseTomlObject,
+  proposeJoinedCodexModelMigrationRepair,
+} from '../../../src/shared/toml-object';
+
+describe('joined Codex model migration TOML recovery', () => {
+  it('proposes the exact one-newline repair for a joined following table header', () => {
+    const rawText = `model = "gpt-5.4"
+
+[notice.model_migrations]
+"gpt-5.3-codex" = "gpt-5.4"[agents.code_simplifier]
+description = "Keep this exact text"
+`;
+
+    const proposal = proposeJoinedCodexModelMigrationRepair(rawText);
+    const insertionOffset = rawText.indexOf('[agents.code_simplifier]');
+
+    expect(proposal).toEqual({
+      repairedText: `${rawText.slice(0, insertionOffset)}\n${rawText.slice(insertionOffset)}`,
+      insertionOffset,
+    });
+    expect(() => parseTomlObject(proposal?.repairedText ?? '')).not.toThrow();
+  });
+
+  it('preserves a UTF-8 BOM, CRLF endings, comments, spacing, and quoting', () => {
+    const rawText =
+      "\uFEFF# exact comment\r\n[notice.model_migrations]\r\n  'gpt-5.3-codex' = 'gpt-5.4'[[agents]]\r\nname = \"one\"\r\n";
+
+    const proposal = proposeJoinedCodexModelMigrationRepair(rawText);
+    const insertionOffset = rawText.indexOf('[[agents]]');
+
+    expect(proposal?.repairedText).toBe(
+      `${rawText.slice(0, insertionOffset)}\r\n${rawText.slice(insertionOffset)}`
+    );
+    expect(proposal?.insertionOffset).toBe(insertionOffset);
+  });
+
+  it('does not propose a repair for valid TOML', () => {
+    const rawText = `[notice.model_migrations]
+"gpt-5.3-codex" = "gpt-5.4"
+
+[agents.code_simplifier]
+description = "valid"
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not generically repair a joined boundary outside the migration table', () => {
+    const rawText = `model = "gpt-5.4"[agents.code_simplifier]
+description = "invalid"
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('ignores a migration table lookalike inside a multiline TOML string', () => {
+    const rawText = `description = """
+[notice.model_migrations]
+"""
+"old" = "new"[agents.outside]
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not propose a repair for unrelated invalid TOML', () => {
+    expect(proposeJoinedCodexModelMigrationRepair('model = "gpt-5.4"\n[features\n')).toBeNull();
+  });
+
+  it('requires a quoted string-to-string migration mapping', () => {
+    const rawText = `[notice.model_migrations]
+gpt-5 = 54[agents.code_simplifier]
+description = "invalid"
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not propose a repair when the following text is not a valid table header', () => {
+    const rawText = `[notice.model_migrations]
+"gpt-5.3-codex" = "gpt-5.4"[agents.code_simplifier
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not propose a repair when another syntax error would remain', () => {
+    const rawText = `[notice.model_migrations]
+"gpt-5.3-codex" = "gpt-5.4"[agents.code_simplifier]
+description = "valid"
+[features
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not propose an ambiguous repair when multiple joined boundaries match', () => {
+    const rawText = `[notice.model_migrations]
+"gpt-5.2" = "gpt-5.3"[agents.first]
+name = "first"
+
+[notice.model_migrations]
+"gpt-5.3" = "gpt-5.4"[agents.second]
+name = "second"
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+
+  it('does not treat a joined-looking string inside a multiline value as a repair candidate', () => {
+    const rawText = `[notice.model_migrations]
+note = """
+"gpt-5.3-codex" = "gpt-5.4"[agents.code_simplifier]
+"""
+[features
+`;
+
+    expect(proposeJoinedCodexModelMigrationRepair(rawText)).toBeNull();
+  });
+});