claude-code/src/utils/context.ts

// biome-ignore-all assist/source/organizeImports: ANT-ONLY import markers must not be reordered
import { CONTEXT_1M_BETA_HEADER } from '../constants/betas.js'
import { getGlobalConfig } from './config.js'
import { isEnvTruthy } from './envUtils.js'
import { getCanonicalName } from './model/model.js'
import { resolveAntModel } from './model/antModels.js'
import { getModelCapability } from './model/modelCapabilities.js'

// Model context window size (200k tokens for all models right now)
export const MODEL_CONTEXT_WINDOW_DEFAULT = 200_000

// Maximum output tokens for compact operations
export const COMPACT_MAX_OUTPUT_TOKENS = 20_000

// Default max output tokens
const MAX_OUTPUT_TOKENS_DEFAULT = 32_000
const MAX_OUTPUT_TOKENS_UPPER_LIMIT = 64_000

// Capped default for slot-reservation optimization. BQ p99 output = 4,911
// tokens, so 32k/64k defaults over-reserve 8-16× slot capacity. With the cap
// enabled, <1% of requests hit the limit; those get one clean retry at 64k
// (see query.ts max_output_tokens_escalate). Cap is applied in
// claude.ts:getMaxOutputTokensForModel to avoid the growthbook→betas→context
// import cycle.
export const CAPPED_DEFAULT_MAX_TOKENS = 8_000
export const ESCALATED_MAX_TOKENS = 64_000

/**
 * Check if 1M context is disabled via environment variable.
 * Used by C4E admins to disable 1M context for HIPAA compliance.
 */
export function is1mContextDisabled(): boolean {
  return isEnvTruthy(process.env.CLAUDE_CODE_DISABLE_1M_CONTEXT)
}

export function has1mContext(model: string): boolean {
  if (is1mContextDisabled()) {
    return false
  }
  return /\[1m\]/i.test(model)
}

// @[MODEL LAUNCH]: Update this pattern if the new model supports 1M context
export function modelSupports1M(model: string): boolean {
  if (is1mContextDisabled()) {
    return false
  }
  const canonical = getCanonicalName(model)
  return canonical.includes('claude-sonnet-4') || canonical.includes('opus-4-6')
}

export function getContextWindowForModel(
  model: string,
  betas?: string[],
): number {
  // Allow override via environment variable (ant-only)
  // This takes precedence over all other context window resolution, including 1M detection,
  // so users can cap the effective context window for local decisions (auto-compact, etc.)
  // while still using a 1M-capable endpoint.
  if (
    process.env.USER_TYPE === 'ant' &&
    process.env.CLAUDE_CODE_MAX_CONTEXT_TOKENS
  ) {
    const override = parseInt(process.env.CLAUDE_CODE_MAX_CONTEXT_TOKENS, 10)
    if (!isNaN(override) && override > 0) {
      return override
    }
  }

  // [1m] suffix — explicit client-side opt-in, respected over all detection
  if (has1mContext(model)) {
    return 1_000_000
  }

  const cap = getModelCapability(model)
  if (cap?.max_input_tokens && cap.max_input_tokens >= 100_000) {
    if (
      cap.max_input_tokens > MODEL_CONTEXT_WINDOW_DEFAULT &&
      is1mContextDisabled()
    ) {
      return MODEL_CONTEXT_WINDOW_DEFAULT
    }
    return cap.max_input_tokens
  }

  if (betas?.includes(CONTEXT_1M_BETA_HEADER) && modelSupports1M(model)) {
    return 1_000_000
  }
  if (getSonnet1mExpTreatmentEnabled(model)) {
    return 1_000_000
  }
  if (process.env.USER_TYPE === 'ant') {
    const antModel = resolveAntModel(model)
    if (antModel?.contextWindow) {
      return antModel.contextWindow
    }
  }
  return MODEL_CONTEXT_WINDOW_DEFAULT
}

export function getSonnet1mExpTreatmentEnabled(model: string): boolean {
  if (is1mContextDisabled()) {
    return false
  }
  // Only applies to sonnet 4.6 without an explicit [1m] suffix
  if (has1mContext(model)) {
    return false
  }
  if (!getCanonicalName(model).includes('sonnet-4-6')) {
    return false
  }
  return getGlobalConfig().clientDataCache?.['coral_reef_sonnet'] === 'true'
}

/**
 * Calculate context window usage percentage from token usage data.
 * Returns used and remaining percentages, or null values if no usage data.
 */
export function calculateContextPercentages(
  currentUsage: {
    input_tokens: number
    cache_creation_input_tokens: number
    cache_read_input_tokens: number
  } | null,
  contextWindowSize: number,
): { used: number | null; remaining: number | null } {
  if (!currentUsage) {
    return { used: null, remaining: null }
  }

  const totalInputTokens =
    currentUsage.input_tokens +
    currentUsage.cache_creation_input_tokens +
    currentUsage.cache_read_input_tokens

  // Treat zero input tokens the same as no usage data — avoids flashing
  // "ctx:0%" when a third-party API omits usage from message_start.
  if (totalInputTokens === 0) {
    return { used: null, remaining: null }
  }

  const usedPercentage = Math.round(
    (totalInputTokens / contextWindowSize) * 100,
  )
  const clampedUsed = Math.min(100, Math.max(0, usedPercentage))

  return {
    used: clampedUsed,
    remaining: 100 - clampedUsed,
  }
}

/**
 * Returns the model's default and upper limit for max output tokens.
 */
export function getModelMaxOutputTokens(model: string): {
  default: number
  upperLimit: number
} {
  let defaultTokens: number
  let upperLimit: number

  if (process.env.USER_TYPE === 'ant') {
    const antModel = resolveAntModel(model.toLowerCase())
    if (antModel) {
      defaultTokens = antModel.defaultMaxTokens ?? MAX_OUTPUT_TOKENS_DEFAULT
      upperLimit = antModel.upperMaxTokensLimit ?? MAX_OUTPUT_TOKENS_UPPER_LIMIT
      return { default: defaultTokens, upperLimit }
    }
  }

  const m = getCanonicalName(model)

  if (m.includes('opus-4-6')) {
    defaultTokens = 64_000
    upperLimit = 128_000
  } else if (m.includes('sonnet-4-6')) {
    defaultTokens = 32_000
    upperLimit = 128_000
  } else if (
    m.includes('opus-4-5') ||
    m.includes('sonnet-4') ||
    m.includes('haiku-4')
  ) {
    defaultTokens = 32_000
    upperLimit = 64_000
  } else if (m.includes('opus-4-1') || m.includes('opus-4')) {
    defaultTokens = 32_000
    upperLimit = 32_000
  } else if (m.includes('claude-3-opus')) {
    defaultTokens = 4_096
    upperLimit = 4_096
  } else if (m.includes('claude-3-sonnet')) {
    defaultTokens = 8_192
    upperLimit = 8_192
  } else if (m.includes('claude-3-haiku')) {
    defaultTokens = 4_096
    upperLimit = 4_096
  } else if (m.includes('3-5-sonnet') || m.includes('3-5-haiku')) {
    defaultTokens = 8_192
    upperLimit = 8_192
  } else if (m.includes('3-7-sonnet')) {
    defaultTokens = 32_000
    upperLimit = 64_000
  } else {
    defaultTokens = MAX_OUTPUT_TOKENS_DEFAULT
    upperLimit = MAX_OUTPUT_TOKENS_UPPER_LIMIT
  }

  const cap = getModelCapability(model)
  if (cap?.max_tokens && cap.max_tokens >= 4_096) {
    upperLimit = cap.max_tokens
    defaultTokens = Math.min(defaultTokens, upperLimit)
  }

  return { default: defaultTokens, upperLimit }
}

/**
 * Returns the max thinking budget tokens for a given model. The max
 * thinking tokens should be strictly less than the max output tokens.
 *
 * Deprecated since newer models use adaptive thinking rather than a
 * strict thinking token budget.
 */
export function getMaxThinkingTokensForModel(model: string): number {
  return getModelMaxOutputTokens(model).upperLimit - 1
}