Large-file threshold was defined in two places (1 MB vs 100 MB), causing inconsistent handling #2540

Summary

The "large file" threshold — which decides whether a file loads eagerly (full line index, LSP, exact scrollbar) or lazily (chunked, no line index → byte-offset gutter/status, LSP skipped) — was defined by two competing constants with different values, and several sites didn't honor the user setting. As a result the effective threshold depended on which code path you hit.

Symptom

Opening a file between the two thresholds — e.g. jumping to a definition inside slangd's dumped core builtin module (~2.1 MB) — put the buffer into large-file mode: the gutter and status bar showed byte offsets instead of line numbers ("Byte 126437" rather than "Ln 4262, Col 25"), and LSP was disabled, even though 2 MB is a perfectly reasonable "small" file.

Root cause

Plus:

• check_large_file_encoding was a pub fn with no production caller (only a test) that carried the 100 MB value; the real encoding-confirmation flow is driven by load_large_file_internal.
• composite_buffer_actions passed the constant instead of the config value.
• wasm had its own third 100 MB copy.
• highlighter::MAX_PARSE_BYTES (a viewport parse budget — a distinct concern) borrowed the file-threshold constant.

So editor.large_file_threshold_bytes did not actually control the whole chain, and the default was an aggressively low 1 MB.

Fix

Consolidated to a single source of truth: editor.large_file_threshold_bytes, whose only constant is its default, raised to 10 MB. Removed the 100 MB duplicate, the == 0 fallback, and the dead check_large_file_encoding; routed the production bypass through the config value; gave the highlighter its own budget constant; regenerated plugins/config-schema.json.

Verified: go-to-definition into the 2.1 MB core builtin now opens with line numbers ("Ln 4262, Col 25").

Fixed on branch claude/slangd-lsp-testing-372g8o (commits 6e24fab, 57338e2).

Follow-up

The large_file_threshold parameter is still threaded through in-memory constructors that ignore it — tracked separately as tech debt.