Unnecessary structuredClone on small, single-use config objects

[s2x]

Description

The clone() helper in models.config.mjs:116-118 uses structuredClone() and is called in every getter function:

export function clone(value) {
  return value === undefined ? undefined : structuredClone(value);
}

Called from:

• getModelLimit() (line 131) — clones { context: N, output: N }
• getModelCost() (line 152, 156) — clones { input: N, output: N, cache_read: N, cache_write: N }
• getModelVariants() (line 163) — clones variant objects
• getModelOptions() (line 170) — clones { reasoningEffort: "none" }

Analysis

structuredClone() is designed for deep-cloning complex objects with circular references, typed arrays, Maps, Sets, etc. Here it's used on flat objects with 2-5 numeric/string fields.

In processModels(), these cloned objects are immediately assigned to models[displayName] and never mutated afterwards. The clone exists purely as defensive programming against a mutation that never happens.

Impact

• structuredClone() is ~10-50x slower than object spread for small flat objects.
• With 15+ supported models, that's 60+ unnecessary structuredClone calls per run.
• In practice, the total wall-clock impact is sub-millisecond, so this is a code quality issue, not a performance bottleneck.

Proposed fix

Option A: Replace structuredClone with spread for flat objects:

export function clone(value) {
  return value === undefined ? undefined : { ...value };
}

Option B: Remove clone() entirely — the objects from SUPPORTED_MODELS are literals that are never mutated:

export function getModelLimit(displayName, apiModel = null) {
  const config = getModelConfig(displayName);
  if (config?.limit) return config.limit;
  // ...
}

Option C: Keep clone() but document why defensive copying is needed (if there's a downstream mutation scenario I'm not seeing).

Acceptance criteria

• structuredClone() is replaced with a lighter-weight approach or removed.
• All existing unit tests pass without modification.
• SUPPORTED_MODELS values are not mutated by any code path (verify or add a freeze-based test).

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