Release v6.8.3: malformed tool-call JSON repair

[code-crusher]

Summary

Release 6.8.3 — resilient tool-call argument handling plus a model picker fix.

Fixed

• Model picker now updates the header row's MODEL line. Selecting a model updated settings and the agent, but the header row's modelName was a stale snapshot — the MODEL/WORKSPACE line only refreshed on /new or /resume. switchModel now patches the header row in place.

Changed

• Malformed tool-call JSON is now repaired instead of rejected. Models that emit almost-JSON — unquoted strings ("file_pattern": *.tsx), unquoted keys, single quotes, trailing commas, Python literals (True/None), comments, XML-style tags interleaved where punctuation belongs ("offset</longcat_arg_key>), keys with dropped closing quotes ("offset: 600), or output truncated mid-call — no longer burn a round trip on a corrective error (weaker models repeated the same mistake on retry). A best-effort repair pass (src/utils/jsonRepair.ts) recovers the intended arguments, the tool executes with them, and a note on the tool result tells the model what actually ran; only truly unrecoverable arguments still return the corrective error. Session replay and the AI SDK history path use the same repair so the model sees its own repaired calls.
• search_files numeric limits clamp instead of failing. max_results and context_lines values that are fractional, out of range, or numeric strings now clamp to the nearest bound (or fall back to the default when non-numeric) instead of failing the whole search — e.g. context_lines: 3 runs with 2.

Test plan

• npm run test:json-repair — 13 tests: strict pass-through, unquoted values/keys, single quotes, Python literals, comments, truncation, XML tag stripping, dropped key quotes, boundary cases (valid JSON untouched, tags-in-strings preserved, unrecoverable → null)
• npm run test:search — 11 tests, clamping assertions updated
• npx tsx --test test/files.test.ts — 2 tests (read_file defaults)
• npx tsc --noEmit clean
• test/models.test.ts failures verified pre-existing on origin/main (Axon model retirement, unrelated)

[matterai-app]

🧪 PR Review is completed: Well-built JSON repair pipeline with thorough test coverage; the agent-side repair-note plumbing and graceful search-limit clamping are solid. Two hardening gaps in the new parser: removed falsy-guards on tool-call arguments make it crash-prone on session-restored data, and invalid escape sequences (un-escaped Windows paths) defeat the repair. Reviewed src/core/agent.ts (repair-note plumbing, transcript repair): no issues found. Reviewed src/ui/App.tsx: no issues found. Reviewed src/tools/executors/searchFiles/types.ts: no issues found. Reviewed src/api/aiSdkClient.ts: no issues found. Reviewed test/json-repair.test.ts: no issues found. Reviewed test/search-files.test.ts: no issues found. Reviewed package.json: no issues found.

Skipped files

• CHANGELOG.md: Skipped file pattern

⬇️ Low Priority Suggestions (2)

src/utils/jsonRepair.ts (2 suggestions)

Location: src/utils/jsonRepair.ts (Lines 23-26)

🟡 Null Safety

Issue: The old call sites guarded against missing arguments — agent.ts used JSON.parse(call.function.arguments || "{}") for transcript building and toolCall.arguments ? JSON.parse(...) : {} in handleToolCall. This PR passes the value straight into parseToolCallArguments, so a tool_call restored from a session file (or a provider payload) with arguments absent hits raw.trim() and throws a TypeError — crashing transcript/history replay on session resume, where the old code safely produced {}.

Fix: Accept undefined/null at the module boundary and treat them as empty input. This single-point hardening restores the old defensive behavior for every caller (agent.ts:305, agent.ts:1216) without touching call sites.

Impact: Prevents a crash during session resume when stored tool_calls lack an arguments field.

-  export function parseToolCallArguments(
-    raw: string,
-  ): ParsedToolCallArguments | null {
-    const trimmed = raw.trim();
+  export function parseToolCallArguments(
+    raw: string | undefined | null,
+  ): ParsedToolCallArguments | null {
+    const trimmed = (raw ?? "").trim();

Location: src/utils/jsonRepair.ts (Lines 201-201)

🟡 Robustness

Issue: When an intact quoted string is copied verbatim (line 201), invalid escape sequences survive the repair. E.g. {"path": "C:\Users\x", "file_pattern": *.ts} fails strict parse, but the repair re-emits "C:\Users\x" unchanged, so the final JSON.parse still fails and the entire call is rejected as unrecoverable. Un-escaped Windows paths are one of the most common LLM JSON malformations for file-oriented tools, and the truncated-string path (line 198, via quoteAsJsonString) already handles them — only this intact-string path does not.

Fix: When re-emitting an intact string, escape lone backslashes that are not part of a valid JSON escape sequence (leaving valid \, , \", \u… sequences untouched).

Impact: Repairs a common malformation class instead of dead-ending the tool call with a re-issue request.

-          out += source.slice(index, end + 1);
+          out += `"${content.replace(/\\\\|\\(?!["\\\\/bfnrtu])/g, (m) => (m.length === 2 ? m : "\\\\"))}"`;