Claude Haiku 5.5 (effort default (no --effort flag) · thinking on) on Run business WhatsApp customer messages with an agent

AClaude Haiku 5.5default · thinking on · Claude Code 2.1.299 (headless -p) · cloud · 2026-10-16 · by @bobsiopener

Trust 80%Fully autonomoussuccess · first tryCompare

Estimated cost: $0.0052
Wall time: 21s
Human step-ins: 0
Outcome: Pass

Compare with other models on this task →

Exact prompt

You are a customer-messaging agent for a mock business (no real WhatsApp). Process each message in inbox.jsonl using only facts from kb.md and availability in slots.json. Write replies.jsonl (one JSON per line: {"to": phone, "text": reply}) in the same order, update slots.json for bookings/cancellations (value = customer name, null = free), and write log.csv with header phone,name,intent,action for every message. If a requested slot is taken, offer the nearest free slot instead of booking.

Task prompt given to the agent (headless, offline, synthetic fixture inputs): You are a customer-messaging agent for a mock business (no real WhatsApp). Process each message in inbox.jsonl using only facts from kb.md and availability in slots.json. Write replies.jsonl (one JSON per line: {"to": phone, "text": reply}) in the same order, update slots.json for bookings/cancellations (value = customer name, null = free), and write log.csv with header phone,name,intent,action for every message. If a requested slot is taken, offer the nearest free slot instead of booking. Inspired by https://agentusecases.ai (listing: 'Run business WhatsApp customer messages with an agent', X source) (unverified; not checked with the author). This is an independent re-run on a reproducible synthetic task; it does not report or reproduce the original post's numbers. Cost shown is a list-price API-equivalent estimate (run on a Claude Pro subscription, not billed).

Success criteria: All automated rubric checks pass: 6 replies to the right numbers; Tom: $120 and Aetna accepted; Lena booked Oct19 9:00; Ravi not double-booked, offered alternative; Rita's slot freed; Omar: closed Sunday + MetLife not accepted; Jess: $350 and booked Sat Oct24 9:00; Oct19 10:00 & Oct20 14:00 still free; log.csv header + 6 rows.

Setup notes: Cost is an ESTIMATE: Claude Code's list-price API-equivalent figure. The run used a Claude Pro subscription, so nothing was billed. input_tokens = all input incl. cache-creation and cache-read tokens; cached_tokens = cache reads (subset of input). Claude Code's cost bills cache writes at the 1h cache-write premium, so it can differ from a flat input-price recompute. Web disabled; tools Read/Write/Edit/Glob/Grep/Bash; single run; scored automatically (9/9 checks).

Estimated cost List-price estimate; not actually billed.

Metrics

Estimated cost: $0.0052
Wall time: 21s
Human step-ins: 0
Turns: 6

Model usage
Model	Input tok	Output tok	Cost
AClaude Haiku 5.5anthropic/claude-haiku-5.5effort default (no --effort flag) · thinking on	85,883	4,408	$0.0052

Reproduce this run

Use the use case prompt on the use case page.
Same setup: Claude Haiku 5.5 (anthropic/claude-haiku-5.5, effort default (no --effort flag) · thinking on) via Claude Code 2.1.299 (headless -p), cloud.
It counts as a success only if it meets every success criterion: All automated rubric checks pass: 6 replies to the right numbers; Tom: $120 and Aetna accepted; Lena booked Oct19 9:00; Ravi not double-booked, offered alternative; Rita's slot freed; Omar: closed Sunday + MetLife not accepted; Jess: $350 and booked Sat Oct24 9:00; Oct19 10:00 & Oct20 14:00 still free; log.csv header + 6 rows.
Log model, tokens, wall time, human step-ins and the evidence log, then submit it as a reproduction. A different model? Submit a head-to-head rerun.

How runs are scored: Methodology.

Was this useful?

⇄ Rerun on another model

Automated checks

Trust 80% comes from these checks (how Trust % works).

Run date is not in the future : passed
Model is in the dated pricing table : passed
Cost recomputed from tokens matches : passed
Cached tokens are consistent : passed
Output throughput is plausible : passed
Autonomy matches step-ins : passed
Step-ins do not exceed turns : passed
Retries agree with first-try result : passed
Evidence log SHA-256 matches : passed
Evidence log is substantial : passed

Evidence log

{
 "duration_api_ms": 19276,
 "stop_reason": "end_turn",
 "session_id": "[REDACTED]",
 "total_cost_usd": 0.00521378,
 "usage": {
  "input_tokens": 8,
  "cache_creation_input_tokens": 11317,
  "cache_read_input_tokens": 74558,
  "output_tokens": 4408,
  "output_tokens_details": {
   "thinking_tokens": 2250
  },
  "server_tool_use": {
   "web_search_requests": 0,
   "web_fetch_requests": 0
  },
  "service_tier": "standard",
  "cache_creation": {
   "ephemeral_1h_input_tokens": 11317,
   "ephemeral_5m_input_tokens": 0
  },
  "inference_geo": "global",
  "iterations": [
   {
    "input_tokens": 2,
    "output_tokens": 565,
    "cache_read_input_tokens": 23461,
    "cache_creation_input_tokens": 395,
    "cache_creation": {
     "ephemeral_5m_input_tokens": 0,
     "ephemeral_1h_input_tokens": 395
    },
    "type": "message"
   }
  ],
  "speed": "standard",
  "fallback_credit": null
 },
 "modelUsage": {
  "claude-haiku-5-5": {
   "inputTokens": 8,
   "outputTokens": 4408,
   "cacheReadInputTokens": 74558,
   "cacheCreationInputTokens": 11317,
   "webSearchRequests": 0,
   "costUSD": 0.00521378,
   "contextWindow": 1000000,
   "maxOutputTokens": 128000,
   "thinkingTokens": 2250,
   "canonicalModel": "claude-haiku-5-5",
   "provider": "firstParty",
   "costBasis": "list"
  }
 },
 "permission_denials": [],
 "terminal_reason": "completed",
 "fast_mode_state": "off",
 "fast_mode_disabled_reason": "sdk_opt_in_required",
 "subagent_stats": {
  "spawned": 0,
  "requested": {
   "background": 0,
   "foreground": 0,
   "unset": 0
  },
  "started_in_background": 0,
  "max_depth": 0,
  "spawned_by_subagents": 0,
  "completed": 0,
  "failed": 0,
  "killed": {
   "parent": 0,
   "user": 0,
   "system": 0
  },
  "refused": {
   "depth_limit": 0,
   "concurrency_limit": 0,
   "budget": 0
  },
  "by_type": {}
 },
 "safety_stops": 0,
 "is_error": false,
 "num_turns": 6,
 "subtype": "success",
 "api_error_status": null,
 "result": "All six messages are processed. I wrote `replies.jsonl`, updated `slots.json`, and wrote `log.csv` (one row per message). The output files parse correctly: 6 replies, 6 log rows, 4 columns each.\n\n| Customer | Request | Outcome |\n|---|---|---|\n| Tom Hale | Cleaning price, Aetna? | Answered: $120, Aetna accepted. |\n| Lena Park | New-patient exam, Mon Oct 19 9am | Booked `2026-10-19T09:00`. |\n| Ravi Shah | Cleaning, Mon Oct 19 11am | 11am was taken, so I offered the nearest free slot, Mon Oct 19 10am. Not booked; the slot is still free. |\n| Rita Gomez | Cancel Sat Oct 24 10am | Cancelled. `2026-10-24T10:00` is now free. |\n| Omar Ali | Open Sunday? MetLife? | Closed Sundays, MetLife not accepted. Listed the accepted insurers. |\n| Jess Wu | Whitening price, earliest free Saturday | Whitening $350. Booked the earliest free Saturday, `2026-10-24T09:00`. |\n\nChoices I made:\n- **Ravi's alternative:** I took \"nearest\" as the closest free time on the same day, 10am. The reply asks him to confirm before anything is booked, since the instructions said to offer rather than book.\n- **Jess's slot:** Saturday 9am was free and earlier than the 10am slot Rita is releasing, so it was the earliest.\n- **Lena's reply:** I added the $95 new-patient exam fee from the knowledge base.",
 "ttft_ms": 1423,
 "type": "result",
 "duration_ms": 19670,
 "uuid": "[REDACTED]",
 "ttft_stream_ms": 1258,
 "time_to_request_ms": 253,
 "first_content_frame_ms": 1258,
 "queued_turn_count": 0,
 "result_index": 0
}