Cut Claude API Spend from Your Terminal with HTTP
A curl request you can inspect before paying
When an editor integration starts burning through credits, I want the smallest reproducible request. A plain HTTP client makes the expensive parts visible: the model, the conversation, the output limit, and the context sent again on every turn. Start there before adding an SDK, an agent loop, or automatic retries.
The Anthropic Messages API uses POST /v1/messages. With Fluxo, the base URL is https://api.fluxorelay.com. Set FLUXO_API_KEY locally, then set FLUXO_MODEL to the exact Messages API model identifier shown for your chosen model. Display names and request identifiers are not necessarily interchangeable.
This is a minimal terminal request, assuming a shell with environment-variable expansion:
curl --fail-with-body --silent --show-error https://api.fluxorelay.com/v1/messages -H "x-api-key: $FLUXO_API_KEY" -H 'anthropic-version: 2023-06-01' -H 'content-type: application/json' --data "{\"model\":\"$FLUXO_MODEL\",\"max_tokens\":160,\"messages\":[{\"role\":\"user\",\"content\":\"Explain this error in three sentences: connection refused at localhost:5432.\"}]}"
Keep the key out of committed scripts and captured terminal sessions. The version header selects the API contract; it does not select the model. Save the response body while experimenting so you can inspect both the answer and its usage metadata.
Make max_tokens match the job in your editor
For a short error explanation, 160 output tokens is a useful starting budget. For a patch, it may be too restrictive. max_tokens caps generated output; it does not shrink the input or reserve a fixed charge. A response stopped by the limit may need another request, wiping out the intended saving.
Try Claude Haiku 4.5 for bounded tasks such as classifying errors or extracting fields. Use Claude Sonnet 5.5 when a representative test shows the harder reasoning earns its extra cost. Compare total spend per accepted result, including retries and repairs, rather than comparing one successful response from each.
- Send the failing function and relevant stack frames instead of the entire repository.
- Ask for one actionable diagnosis before requesting a complete implementation.
- Check stop_reason before treating a shortened answer as a finished response.
Reuse stable prefixes with explicit prompt caching
Repeated repository instructions are a good caching candidate. Put stable material first and the changing question last. In Anthropic's structured content format, a text block can carry a cache marker: {"type":"text","text":"Your stable repository instructions...","cache_control":{"type":"ephemeral"}}. Use this only where the selected model and relay route support prompt caching.
A marker does not guarantee a cache hit. Minimum prefix lengths, cache lifetime, and model support matter. Editing an early instruction can invalidate reuse of the prefix that follows it. Keep timestamps, request identifiers, and changing diagnostics outside the stable portion.
Inspect usage fields such as cache_creation_input_tokens and cache_read_input_tokens when returned. Cache writes have a cost, and reads have a cost. Fluxo bills actual token usage, including cache reads and writes, so measure repeated requests before declaring caching a win. A large prefix used once may be a poor candidate.
Stop conversation history and retries from multiplying cost
The Messages API is stateless: your client supplies the conversation needed for each request. Appending every previous exchange means paying to process an expanding input. Keep recent evidence, summarize resolved work, and remove obsolete logs. Preserve exact code where correctness depends on it.
Retries deserve the same discipline. A timeout does not prove the upstream model did no work. Avoid automatic retry loops during initial testing. For production, use bounded retries, backoff, and response identifiers in your logs; never assume repeating a POST is free.
Track accepted answers across your terminal tools
Fluxo provides one key and one base URL for Claude, GPT, Gemini, DeepSeek, Kimi, GLM, Qwen, Grok, and more, with no monthly fee. It works with Claude Code, Codex, Gemini CLI, and any OpenAI SDK; those clients still need their appropriate protocol configuration. This curl request specifically uses the Anthropic Messages format.
If you want to try this workflow, create a Fluxo account and start with a small, repeatable task. Log model, usage, latency, and whether you accepted the answer. Users also earn a referral share when people they invite pay. Keep that separate from your engineering benchmark: the useful number is what a completed task actually costs.