[anhnh2002]

LLM-generated flowchart labels such as C{msg.error()?} can fail rendering and repeat the same error during agent retries. Add syntax guidance across generation/update prompts and the MCP skill, and repair unquoted classic rectangle/diamond labels only after a confirmed delimiter error and successful revalidation. Persist verified replacements and return the saved text; keep repairs within the original edit's undo history.

Validation now distinguishes confirmed syntax failures from unavailable validation. Check HTTP responses explicitly for pinned mermaid-py 0.8.0 (which does not raise on failed requests), handle newer exception-based versions, and retain complete parser diagnostics. Disabled validation, timeouts, and renderer outages warn without claiming syntax success or requesting syntax fixes.

Parent/repository overviews use the same validation before saving, with one correction attempt for remaining syntax errors. Unavailable validation continues with a warning. Automatic repair is limited to clear, single-line rectangle/diamond labels; ambiguous syntax is left for the agent.

The repair fixtures include the issue’s exact reproduction with an inline -- no --> edge, preserving the edge text while quoting its target label. Toolkit unit tests also cover CI environments without the CLI SDK by stubbing only SDK registration and executing the real editor implementation.

The syntax guidance reflects Mermaid 11.9.0: function calls, braces, brackets, commas, and double dashes are valid in sequence-message text; literal semicolons require #59;, and backticks do not escape them. Add a locked development-only Mermaid/jsdom harness and CI job to verify these cases with the viewer's actual parser version.

Validation:

• Clean staged checkout: 471 Python tests passed (83 new regression cases).
• All 83 focused regressions passed with both mermaid-py 0.8.0 and 0.8.4.
• 37 shared fixtures passed against Mermaid 11.9.0.
• Ruff lint and Ruff format checks passed on all 10 changed Python files; git diff --check passed.

Fixes #141