Scarf v2.18.1

Scarf v2.18.1

A fast follow to v2.18.0 with one theme: power settings for Hermes 0.20's best new knobs — compression tuning, per-model reasoning effort, and provider exclusions — every key verified against Hermes source, and the YAML-writing machinery behind them hardened by an adversarial audit before shipping.

New: compression tuning

Hermes 0.20 overhauled context compression and exposed real controls. Four of them now live beside the existing threshold slider (on 0.20 hosts):

• Absolute token threshold (compression.threshold_tokens) — trigger compression at a fixed token count instead of a context-ratio; Hermes uses the lower of the two when both are set. Setting 0 turns it off — a round-trip we verified is lossless against Hermes's own coercion logic.
• Guaranteed conversation tail (compression.min_tail_user_messages) — your N most recent user messages always survive compaction.
• Idle compaction (compression.idle_compact_after_seconds) — compact proactively while the session sits idle instead of pausing mid-conversation.
• Progress notices (compression.progress_notices) — see when compression runs instead of wondering about the pause.

New: per-model reasoning effort

A Per-Model Reasoning table in the Agent tab: pin reasoning effort per model — your heavyweight model thinks at max or ultra (the new 0.20 tiers, now in the pickers on 0.20 hosts) while your fast model stays at low. Matching follows Hermes's own resolver — exact names or common spelling variants (dots/dashes, optional provider prefix), first match wins, overrides beat the global setting.

Under the hood this writes the agent.reasoning_overrides dictionary — a key Hermes's own config set can't write (dots in model names) — via Scarf's surgical YAML editor: your comments and unknown keys elsewhere in config.yaml are preserved byte-for-byte, and removing the last row removes the key entirely.

New: excluded providers

A list editor in the Model section for model_catalog.excluded_providers — providers you never use disappear from every model picker and from built-in resolution. Free-text entry with suggestions from your live provider catalog; any capitalization works (Hermes lowercases on match — verified).

Hardened: the YAML writer, adversarially audited

Before cutting this release we ran a fresh-eyes audit against the new write paths and fixed everything it found — including two corruption-class bugs that never shipped:

• Inline flow syntax is now understood. The stock Hermes example config ships reasoning_overrides: {} inline — the writer previously would have appended a duplicate key instead of replacing that line, and a hand-written inline dict was invisible to the UI while staying silently active. Both fixed: inline dicts/lists are replaced in place and flat inline content is read back into the editor.
• Section headers with trailing comments and CRLF files are safe. Either could previously trick the writer into appending a duplicate top-level section — which YAML's last-wins rule would resolve by discarding your entire original section. Fixed in the shared locator, which also hardens the pre-existing gateway allowlist write path; line endings are preserved on output.
• Hermes's disable aliases are honored. A hand-edited disabled/false/off effort value is preserved verbatim instead of silently blocking all edits to the section, and any rejected write now shows an error instead of doing nothing.

Every fix carries a regression test; writer output was cross-validated by loading it with PyYAML — the same parser Hermes uses.

Under the hood

• 25 new tests this release (settings round-trips, quoted-key YAML, flow-dict handling, CRLF, alias values); the suite now runs 1,090.
• All three new surfaces are capability-gated on Hermes v0.20 — on older hosts, Settings renders exactly as v2.18.0.

Upgrade notes

• Sparkle will offer the update automatically, or use Scarf → Check for Updates. macOS 14.6+ deployment target unchanged.
• Hermes target unchanged: v0.20.0 (v2026.8.3), minimum v0.6.0. The new settings appear only against 0.20+ hosts.
• One known limitation: hand-written comments inside an existing reasoning_overrides block are not preserved when you edit the table (comments everywhere else in config.yaml are untouched).