Training Details
- Base Model:
Qwen/Qwen3.5-4B
- Training Framework: Tinker Supervised LoRA Training
- Training Set: 540 diverse synthetic emails curated to reflect realistic email structures, edge cases, urgent requests, and newsletters
- Adapter Configuration: Rank r=32, Alpha α=32, targeting
all-linear modules
Classification Labels & Schema
The model classifies an email into one of four labels:
must_act: Immediate action required (bills, account suspension notices, security alerts, calendar invitations with impending deadlines).
worth_a_look: High-value personal opportunities, relevant technical releases, developer meetups, or beta invites.
fyi: Informational notifications requiring no action (receipts, change password confirmations, closed issue updates).
noise: Marketing blasts, promotional discounts, routine automated newsletters, and social clutter.
{ "label": "<must_act | worth_a_look | fyi | noise>", "why": "<under 10 words explanation>", "deadline": "<YYYY-MM-DD or null>", "summary": "<concise one-line summary>"}
Evaluation Benchmark
Evaluated on data/val.jsonl (60 held-out synthetic emails, 28 containing non-null gold deadlines). Latency was benchmarked in parallel with concurrency 10.
Table with columns: Variant, Label Accuracy, Macro-F1, JSON Validity, Deadline Exact-Match, p50 Latency, Cost / 1k Emails| Variant | Label Accuracy | Macro-F1 | JSON Validity | Deadline Exact-Match | p50 Latency | Cost / 1k Emails |
|---|
| Base Qwen3.5-4B (0-shot) | 52/60 (86.67%) | 0.8645 | 60/60 (100.00%) | 23/28 (82.14%) | 2.58s | $0.1569 |
| Base Qwen3.5-4B (3-shot) | 56/60 (93.33%) | 0.9328 | 60/60 (100.00%) | 25/28 (89.29%) |
Fine-Tuned Per-Label Breakdown
- must_act: Precision 1.0000 | Recall 1.0000 | F1: 1.0000
- worth_a_look: Precision 0.9333 | Recall 0.9333 | F1: 0.9333
- fyi: Precision 1.0000 | Recall 0.9333 | F1: 0.9655
- noise: Precision 0.9375 | Recall 1.0000 | F1: 0.9677
Honest Limitations
- Synthetic Training Distribution: The 540 training emails and 60 validation emails are synthetically generated. While designed with realistic edge cases and varied phrasing, performance on real-world email distributions with noisy formatting or multipart HTML may vary.
- Untested on Production Inboxes: The pipeline and fine-tuned model have not yet been evaluated on real-world corporate or personal inboxes due to privacy considerations.
- Inference Pricing Assumption: The official Tinker pricing documentation lists base Qwen3.5-4B rates (0.33/Mprompttokens,1.005/M completion tokens) but does not provide a distinct rate for sampling fine-tuned checkpoints. The reported cost per 1,000 emails ($0.1412) assumes base model pricing.