ToolCallBuffer

The tool name, once a chunk has supplied it.

The tool-call id, once a chunk has supplied it.

A fully materialized arguments value delivered by a single chunk (dict or, rarely, a scalar). Mutually exclusive with args_parts (see __post_init__ and ingest).

JSON string fragments accumulated across chunks, reassembled by parse_args once the payload looks complete. Mutually exclusive with args (see __post_init__ and ingest).

Append to this list or rebind it wholesale; do not mutate entries in place. The _args_* fields hold a JSON lexer folded over the fragments scanned so far, and _sync_args_fragment_state detects a rebind or a truncation but cannot detect an edit that leaves the list's identity and length unchanged (e.g. pop() then append()), which would leave the scan stale and yield another payload's args. Detecting that would cost a per-chunk rescan, which is the quadratic behavior this state exists to remove.

One-shot latch guarding the single "Calling tool" console line (used only by the headless surface).

One-shot latch for an irrecoverably invalid payload.

Serves two roles. It keeps the warning to one line per payload, even though parse_args re-runs on every later chunk for the retained buffer. It also short-circuits parse_args itself: every condition that sets it is permanent (see _warn_invalid_args), so re-running json.loads per fragment could only fail again — which is what made the pre-incremental version quadratic on a malformed payload.

That second role means the latch now gates data, not just logging: keep it private to _warn_invalid_args, since setting it for any other reason would silently drop a valid tool call. Its lifetime must match the payload whose parse it blocks, so _reset_args_fragment_state clears it alongside the fragment state.

Fold one streamed tool-call chunk's fields into the buffer.

A dict args replaces any accumulated fragments (the provider delivered the whole value at once); a string args is appended as a fragment; any other non-None value is stored as-is.

Return the tool-call args once enough data has arrived, else None.

A non-object JSON value (a bare scalar or list — rare for tool calls) is wrapped as {"value": ...} so a caller's tool_args is always an object.

The returned dict is cached and handed back by identity on a re-run, so callers must treat it as read-only.