claude-opus-5
A Claude Code model, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
Opus 5 is now the default Opus, with a 1M-context option in the model picker.
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.219.
In the changelogs
37Releases whose published page names claude-opus-5.
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v2.1.304
Bundled default model changes to Opus 5.5 at medium effort
The model catalog shipped with Claude Code now defaults to claude-opus-5-5 at medium effort instead of claude-opus-5 at high effort
found in this entry's text
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v2.1.302
claude-opus-5 joins a model list used in a capability check
Claude Code now lists claude-opus-5 alongside other models in a list that one of its checks looks at
found in this entry's text
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v2.1.290
/code-review mediumnow runs the high-effort recipe on most modelsOn every model without its own
/code-reviewrow, Opus 5.5 included,mediumnow runs the eight-angle high recipe instead of a single pass.high,xhighand Opus 5 are unchanged.found in this entry's text
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v2.1.284
Claude Code's built-in model list now points to Opus 5.5 and Sonnet 5.5
Claude Code's built-in current models are now claude-opus-5-5 and claude-sonnet-5-5, with claude-opus-5 and claude-sonnet-5 as the previous ones
found in this entry's text
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v2.1.284
Refused requests on Sonnet 5.5 now fall back to Sonnet 5
When a Sonnet 5.5 request is refused as cyber or frontier_llm, Claude Code now falls back to claude-sonnet-5 instead of an Opus model
found in this entry's text
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v2.1.283
Admins can block specific models and require exact version matches
Managed settings gain
deniedModelsto block models andavailableModelsMatchto stop an allowed ID covering later versionsfound in this entry's text
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v2.1.283
Opus 5.5 can fall back to Opus 5 for one more refusal type
When claude-opus-5-5 refuses a request in the frontier_llm category, Claude Code can now fall back to claude-opus-5
found in this entry's text, named in this entry
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v2.1.282
Opus 5 moved to the overflow section of the built-in model list
In the built-in model list, Opus 5 moves to the overflow section and loses its quick-select flag and description
found in this entry's text, named in this entry
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v2.1.281
Bundled model catalog adds claude-opus-5-5 ("Opus 5.5"), which replaces Opus 5 in the Opus picker slot
Opus 5.5 (
claude-opus-5-5) replaces Opus 5 in the model picker's Opus slot, with default effort "medium" on theccsurfacefound in this entry's text
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v2.1.281
Bundled model catalog: 'Opus 5' quick-select entry is now 'Opus 5.5'
In the bundled model catalog, the "Opus" quick-select entry now points to Opus 5.5 instead of Opus 5
found in this entry's text
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v2.1.281
Bundled model-preset config: chat preset thinking effort for claude-opus-5-5 set to medium
A bundled model config now lists claude-opus-5-5 at medium thinking effort for the chat preset, alongside claude-opus-5 at high
found in this entry's text
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v2.1.281
Model selector config: always_on dropped, min version bumped to 2.1.280
One model entry in the bundled model selector config drops
always_onthinking and now requires Claude Code 2.1.280 or laterfound in this entry's text
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v2.1.281
Bundled model-selector sample defaults Opus 5.5 to medium effort
Built-in model data now sets Opus 5.5 to medium effort and marks Medium as Default for Opus 5.5 and Fable 5.1
found in this entry's text
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v2.1.280
Fast mode's default model resolution changed in prompt and code
Fast mode's system-prompt wording and its default-model fallback in code both changed
found in this entry's text
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v2.1.280
Fast mode no longer restricted to Opus 5/4.8 in the system prompt
The system prompt no longer says fast mode is limited to Opus 5/4.8, and now lists Opus 5.5 in the model catalog
found in this entry's text
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v2.1.280
Opus renamed to Opus 5.5 as the latest-per-family model
Opus model catalog entry renamed from 'Opus 5' to 'Opus 5.5' as the latest in its family
found in this entry's text
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v2.1.280
New cheaper cost table for claude-opus-5-5
A new, cheaper token-cost tier now applies to the claude-opus-5-5 model id
found in this entry's text
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v2.1.280
Safety-classification model routing table gains a 'frontier_llm' entry
Safety-classification model routing gains a new 'frontier_llm' category mapped to claude-opus-5
found in this entry's text
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v2.1.277
Model catalog version bump and per-surface model reassignment
Bundled model catalog updated to version 629 with model reassignments across ccr, ccd, and other surfaces
found in this entry's text, named in this entry
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v2.1.275
Offline/fallback model catalog switches ccr/ccd default model from Sonnet 4.6 to claude-opus-5
Fallback model list now defaults 'ccr' and 'ccd' to claude-opus-5 instead of Sonnet 4.6 when the live catalog is unreachable
found in this entry's text, named in this entry
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v2.1.267
thinking_disabled_effort_cap follows the same gate-precedence rework
The thinking_disabled_effort_cap flag can now override the claude-opus-5 hardcoded default in either direction
found in this entry's text
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v2.1.263
Effort-medium nudge generalized to multiple models and effort levels
The effort-downgrade nudge now works per model instead of just one, but each model needs its own flag turned on.
found in this entry's text
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v2.1.263
Effort-medium nudge generalized to per-model remote-config gates
The effort-downgrade nudge was rebuilt to support multiple models, each hidden behind its own remote switch.
found in this entry's text
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v2.1.257
Compiled seed catalog includes Opus 5 / Sonnet 5 placeholders
The compiled-in seed catalog used before the first fetch lists claude-opus-5, claude-sonnet-5 and claude-haiku-4-5.
found in this entry's text, named in this entry
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v2.1.251
Effort cap when thinking is off, tied to a specific model
Some models cap reasoning effort when thinking is off, matched by name or capability.
found in this entry's text
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v2.1.248
Model tables extended to Opus 4.7, 4.8 and Opus 5
Model tables now list claude-opus-4-7, claude-opus-4-8 and claude-opus-5.
named in this entry, found in this entry's text
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v2.1.248
Per-surface context limits for claude-sonnet-5
Context limits for claude-sonnet-5 are 500,000 on two surfaces and a million elsewhere.
found in this entry's text
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v2.1.246
The claude-api skill's documents moved out of the bundle, unchanged
The claude-api skill's documents moved to separate files with identical content and paths.
found in this entry's text
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v2.1.223
Thrifty-sonic narrowed to one model; plan artifacts moved to its own gate
Plan artifacts now have their own switch instead of riding along with an unrelated experiment.
found in this entry's text
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v2.1.220
Opus 5 is skipped when the client cannot see model entitlements
If your session has no model access info cached, Claude won't fall back to Opus 5.
found in this entry's text
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v2.1.220
Refusal fallback no longer picks Opus 5 when entitlements are unknown
When a refusal triggers a model switch and entitlements are unknown, you get Opus 4.8 instead of Opus 5.
found in this entry's text
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v2.1.219
Opus 5 replaces Opus 4.8 as the default Opus model
Opus 5 is now the default Opus, with a 1M-context option in the model picker.
named in this entry, found in this entry's text
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v2.1.219
The API skill's model placeholders now resolve to Claude Opus 5, with the previous Opus kept as a separate placeholder
The API skill's model placeholders now render Opus 5, keeping the previous Opus named separately.
found in this entry's text
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v2.1.219
Code-review prompt tuned for Opus 5
Code reviews on Opus 5 use a tighter prompt: one diff pass, at most fifteen findings.
found in this entry's text
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v2.1.219
Model-downgrade chain and effort tables know about Opus 5
Model fallbacks and reasoning-effort settings now handle Opus 5, stepping down to Opus 4.8 when needed.
named in this entry, found in this entry's text
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v2.1.219
Opus 5 wired through region env vars, refusal fallbacks and pricing copy
An Opus 5 model is wired through region variables, fast mode, 1M context and pricing text.
found in this entry's text
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v2.1.219
Effort profile added for claude-opus-5
A reasoning-effort table now includes settings for a model named claude-opus-5, with new medium and high profiles.
found in this entry's text
First cited
6The earliest release whose published evidence quoted claude-opus-5 was v2.1.219, 24 Jul 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the model does. All models.