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* Sync claude-api skill with latest upstream updates - Add token-counting.md and SKILL.md trigger description update - Add auth guidance: env credential resolution, ant auth login, OAuth/WIF doc links, 401 causes - Add mid-conversation system messages (beta) to prompt-caching, agent-design, SKILL.md, Python/TS READMEs - Add cache pre-warming (max_tokens: 0) section to prompt-caching - Add Managed Agents pre-flight viability check to onboarding and overview - Add Bedrock model-ID section to model-migration; add Bedrock row to live-sources - Add /claude-api migrate subcommand row and migrate-entry callout - Fix MA networking config: limited type with allow_package_managers/allow_mcp_servers - Bump MA create-operations rate limit to 300 RPM - Fix MA SDK drift: sessions.events.stream(), event.name, typed event arrays - Add SDK coverage: stop_details, error .type, C# tool runner + MA support, Go model constants, Java 2.34.0, client config, response helpers, auto-pagination, advisor tool - Move Sonnet 4 / Opus 4 to deprecated in models.md * Add Anthropic CLI and Claude Platform on AWS docs to claude-api skill - Add shared/anthropic-cli.md: install, auth profiles, OAuth scopes, command structure, version-controlled Managed Agents resources, credential traps - Add shared/claude-platform-on-aws.md: AnthropicAWS clients, SigV4 auth, workspace_id, regions, feature availability - Restore cross-references to both files throughout SKILL.md and the managed-agents docs (previously rewritten to live-sources.md pointers) - Restore Claude Platform on AWS provider taxonomy in SKILL.md, the migration-guide section, and live-sources rows
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Token Counting
Use the count_tokens endpoint (POST /v1/messages/count_tokens) for accurate
token counts against Claude models. Token counts are model-specific — pass
the same model ID you'll use for inference.
Do not use tiktoken. It's OpenAI's tokenizer. It undercounts Claude
tokens by ~15–20% on typical text, and by much more on code or non-English
input. Any estimate from tiktoken, gpt-tokenizer, or similar is wrong for
Claude.
Count a file or string
from anthropic import Anthropic
client = Anthropic()
resp = client.messages.count_tokens(
model="claude-opus-4-8",
messages=[{"role": "user", "content": open("CLAUDE.md").read()}],
)
print(resp.input_tokens)
TypeScript: await client.messages.countTokens({model, messages}) →
.input_tokens. See {lang}/claude-api/README.md for other SDKs.
CLI
ant messages count-tokens --model claude-opus-4-8 \
--message '{role: user, content: "@./CLAUDE.md"}' \
--transform input_tokens -r
Diffing a file across two versions
The endpoint is stateless — count each version separately and subtract:
from anthropic import Anthropic
import subprocess
client = Anthropic()
def count(text: str) -> int:
return client.messages.count_tokens(
model="claude-opus-4-8",
messages=[{"role": "user", "content": text}],
).input_tokens
before = subprocess.check_output(["git", "show", "HEAD:CLAUDE.md"], text=True)
after = open("CLAUDE.md").read()
print(count(after) - count(before))
Full docs: see the Token Counting entry in shared/live-sources.md.