Imagine this scenario. You build an autonomous agent pipeline. You wire in standard skills, configure your API keys, grab a cup of coffee, and watch it tackle complex tasks. Everything feels futuristic.
Then suddenly, a cold splash of reality hits your logs:
Error: 404 Not Found - model 'claude-opus-4-20250514' has been retired.
No timeout. No rate limit. Just an abrupt HTTP 404 from the Anthropic API. Your autonomous agent just spent five minutes trying to summon a ghost.
Here is the story of how dead model identifiers linger inside official agent skills, how an autonomous AI babysitter bot reviewed my pull request, and why keeping documentation in sync across files is harder than it looks.
Large Language Model development moves at breakneck speed. New checkpoints drop, older snapshots get deprecated, and eventually, older model IDs get decommissioned completely.
In the official anthropics/skills
repository, the claude-api
skill is supposed to be the source of truth for how agent frameworks talk to Claude. It tells agents which model strings to use, which models support adaptive thinking, and which models have reached end-of-life.
While inspecting skills/claude-api/shared/models.md
and skills/claude-api/shared/model-migration.md
, I noticed several prominent models were still marked as "Deprecated (retiring soon)" even though their retirement dates had already passed:
claude-opus-4-20250514
(retired June 15, 2026)claude-sonnet-4-20250514
(retired June 15, 2026)claude-3-haiku-20240307
(retired April 19, 2026)claude-opus-4-1-20250805
(retired August 5, 2026)If an agent reads this skill table to resolve friendly names (such as "opus 4" or "haiku 3"), it would attempt to call a decommissioned model ID instead of routing to modern replacements like claude-opus-4-8
, claude-sonnet-5
, or claude-haiku-4-5
.
The fix looked simple enough: remove the outdated "Deprecated" table, move all four models into the "Retired" table, and point alias resolutions to active successors.
I submitted PR #1607 feeling satisfied. Simple documentation cleanup. Easy victory. Right?
Wrong.
A few hours after opening the PR, a GitHub notification popped up. A review had arrived.
Except it was not from a human maintainer. It came from an autonomous agent calling itself:
Reviewed by Hermes Agent (cron babysitter)
Verdict: Comment: correct and useful model-status update; two cross-file consistency nits.
There is something wonderfully surreal about writing open-source code for AI skills, only to have an automated AI agent run a cron job, read your git diff, and evaluate your work like a sharp-eyed proofreader.
And Hermes was not giving generic praise. It found two very real, very subtle cross-file discrepancies that I had missed:
In model-migration.md
, the old deprecated table had listed claude-3-haiku-20240307
retiring on April 19, 2026. But in my new table rows in models.md
, I had typed April 20, 2026.
A single day difference. To a casual reader, April 19 versus April 20 is trivia. But to an API consumer writing automated compliance checks, date drift between sibling markdown files creates confusion.
In models.md
, I had added claude-opus-4-1-20250805
to the Retired table. But in model-migration.md
, I had forgotten to add claude-opus-4-1-20250805
to its corresponding migration table.
The two documentation files inside the same skill were out of sync.
The feedback was spot on.
I checked Anthropic's official release timeline to verify the canonical retirement date: April 19, 2026 was the exact date.
Then I made two surgical updates:
skills/claude-api/shared/model-migration.md
claude-opus-4-1-20250805
pointing to drop-in replacement claude-opus-4-8
, and standardized claude-3-haiku-20240307
to April 19, 2026:
| Retired model | Retired | Drop-in replacement |
| ----------------------------- | ------------- | -------------------- |
| `claude-opus-4-1-20250805` | Aug 5, 2026 | `claude-opus-4-8` |
| `claude-opus-4-20250514` | Jun 15, 2026 | `claude-opus-4-8` |
| `claude-sonnet-4-20250514` | Jun 15, 2026 | `claude-sonnet-5` |
| `claude-3-haiku-20240307` | Apr 19, 2026 | `claude-haiku-4-5` |
skills/claude-api/shared/models.md
Pushed commit bdff74f
to the branch and replied to the review thread.
models.md
and model-migration.md
), always audit every sibling file when updating a status.