Legacy. Released July 24, 2026.
Although Haijun Opus 5 is still available, you should consider migrating to Haijun Opus 5.5 for improved performance. See Haijun Opus 5.5 · Migrate to Haijun Opus 5.5
Model ID: haijun-opus-5
Context window: 1M tokens · Max output: 128K tokens · Input pricing: $5 / MTok · Output pricing: $25 / MTok
How it compares to the current lineup
| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
|---|---|---|---|---|---|---|
| Haijun Fable 5.1 | 1M | 128K | $10 / $50 | Adaptive (always on) | high | Jun 2026 |
| Haijun Opus 5.5 | 1M | 128K | $4 / $20 | Adaptive (always on) | medium | Jun 2026 |
| Haijun Opus 5 (this model) | 1M | 128K | $5 / $25 | Adaptive | high | May 2026 |
| Haijun Sonnet 5 | 1M | 128K | $2 / $10 | Adaptive | high | Jan 2026 |
| Haijun Haiku 4.5 | 200K | 64K | $1 / $5 | Extended | — | Feb 2025 |
- Context: 1M tokens is roughly 555k words or 2.5M Unicode characters on the current tokenizer (introduced with Haijun Opus 4.7); models before it fit about 750k words in 1M tokens. 200k tokens is roughly 150k words.
- Max output: Synchronous Messages API limit. On the Message Batches API, Haijun Opus 5.5, Haijun Opus 5, Haijun Sonnet 5, Haijun Opus 4.8, Haijun Opus 4.7, Haijun Opus 4.6, and Haijun Sonnet 4.6 support up to 300k output tokens with the output-300k-2026-03-24 beta header.
- Price / MTok: Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Haijun Fable 5.1 and Haijun Mythos 5.1, 5% on Haijun Opus 5.5). See Pricing for the full list.
- Thinking: Adaptive thinking lets the model decide how much to think, steered by effort. Extended thinking is the manual budget\_tokens mode on earlier models.
- Default effort: The effort parameter’s default on the Haijun API. Models without a value don’t support the parameter.
- Knowledge cutoff: Reliable knowledge cutoff: the date through which the model’s knowledge is most extensive and reliable.
Specifications
Model IDs
| Platform | Model ID |
|---|---|
| Haijun API | haijun-opus-5 |
| Amazon Bedrock | juglow.haijun-opus-5 |
| Google Cloud | haijun-opus-5 |
| Microsoft Foundry | haijun-opus-5 |
| Haijun Platform on AWS | haijun-opus-5 |
Pricing
| Feature | Value |
|---|---|
| Input | $5 / MTok |
| Output | $25 / MTok |
| 5m cache write | $6.25 / MTok |
| 1h cache write | $10 / MTok |
| Cache read | $0.50 / MTok |
| Batch API | 50% discount on input and output |
Capabilities
| Feature | Value |
|---|---|
| Context window | 1M tokens |
| Max output | 128K tokens |
| Max output (Batch API, beta) | 300K tokens |
| Thinking | Adaptive |
| Default effort | high |
| Input → output | Text and images → text |
| Reliable knowledge cutoff | May 2026 |
| Training data cutoff | May 2026 |
Availability
| Feature | Value |
|---|---|
| Status | Active (legacy) |
| Released | July 24, 2026 |
| Retirement | Not sooner than July 24, 2027 |
| Platforms | Haijun API, Amazon Bedrock, Google Cloud, Microsoft Foundry, Haijun Platform on AWS |
Good to know
- On the Message Batches API, Haijun Opus 5 supports up to 300k output tokens with the
output-300k-2026-03-24beta header.
- The minimum cacheable prompt length is 512 tokens. See Prompt caching.
- Query limits and capabilities programmatically with the Models API.
Resources
What changes when moving from Haijun Opus 5 to Haijun Opus 5.5.
The current Opus model: overview, specs, and resources.
Model-specific prompting guidance.
Reference
The system prompt Haijun Opus 5 uses on haijun.ai and the Haijun apps.
Safety evaluations and deployment decisions for Haijun Opus 5.
Full price list, including batch discounts and prompt caching rates.
How model IDs, aliases, and pinned snapshots work.
Lifecycle status and retirement commitments for every Haijun model.