Agent Skills and the Skills API left beta on the Claude API on 19 August 2026. Anthropic's own release notes state it directly: "Agent Skills and the Skills API (/v1/skills) are out of beta on the Claude API. Requests no longer require the skills-2025-10-02 beta header, including Messages API requests that load Skills through the container parameter." For anyone building on the Skills API rather than using Claude Code's filesystem-based skills or claude.ai's upload flow, this is worth understanding precisely, both what it changes today and what a follow-up SDK release changed a week later.
What "beta" meant here in the first place
Agent Skills launched on the Claude API under the skills-2025-10-02 beta header, the same mechanism Anthropic uses for any Claude API feature it wants field-tested before locking in the request and response shapes for good. A beta header, per Anthropic's own beta headers documentation, exists specifically to "access experimental features and new model capabilities before they become part of the standard API," with the explicit warning that beta features "may have breaking changes with notice" or "be deprecated or removed." Nearly a year on the Claude API, custom Skills upload through /v1/skills, pre-built document Skills for PowerPoint, Excel, Word and PDF, and Messages API requests loading a Skill through the container parameter, all still carried that header requirement until 19 August 2026.
What actually changed on GA day
The core change is narrow and specific: the skills-2025-10-02 header is no longer required anywhere it was previously mandatory, including on /v1/skills create, list, retrieve, delete, and version endpoints, and on Messages API requests that reference a skill_id through the container parameter. Requests that still include the header keep working exactly as before and keep receiving the beta response shapes, so nothing that depended on the header broke that day. GA here means the feature is no longer subject to the beta warning about breaking changes without notice, not that new functionality shipped alongside it.
This landed the same day as four other Claude Platform features reaching GA, all confirmed in the same release notes entry for 19 August 2026: the computer use tool (as the computer_toolset_20260801 toolset, with batch actions and per-member configs), a newly launched browser use tool (browser_toolset_20260801), the Files API, and the Admin API's user-management endpoints for Claude Enterprise organizations (members, invites, groups, and custom roles, covered separately in the Admin API's user-management endpoints, now GA). Five features in one day is a meaningful clearing of Anthropic's beta backlog, and it's a reasonable signal that Agent Skills on the API is now considered stable enough to build production integrations against without expecting the request shape to shift under you.
The Files API's migration path shows the shape of the Skills one
Anthropic's Files API migration guide, published alongside its own GA on the same day, lays out exactly what changes when you actually drop a beta header, and the pattern is instructive since the Skills API's own equivalent migration section works the same way. For the Files API, the guide states: "The Files API is out of beta and needs no beta header. Migrating off files-api-2025-04-14 is optional: requests that still send it keep working and keep returning the beta response shapes, so an existing integration keeps working until you change it." It then documents concrete shape differences: has_more/first_id/last_id pagination gives way to page/next_page, before_id/after_id cursors are replaced (and now return a 400 error if you send them without the header), and expires_at becomes a field that's always present rather than absent entirely.
The Skills API's own beta header removal follows the same shape: nothing breaks on removal day, but specific behaviors change once you're actually off the beta header on a qualifying SDK version, as the next section covers.
What changed a week later, in the SDKs
Anthropic's release notes for 27 August 2026 document a follow-up, SDK-level change: "In Python SDK 1.2.0, TypeScript SDK 0.122.0, Go SDK 1.68.0, Java SDK 2.59.0, Ruby SDK 1.67.0, and C# SDK 12.44.0, client.beta.files and client.beta.skills no longer send the files-api-2025-04-14 and skills-2025-10-02 beta headers and return the same shapes as client.files and client.skills." Two specific behavior changes come with it for Skills:
client.beta.skills.delete()now deletes a Skill together with all of its versions, rather than the single version the beta shape deleted before.- The beta Messages type
BetaSkill, the container Skill reference, is renamedBetaContainerSkill.
Both changes apply only once you're running one of the qualifying SDK releases above and have moved off the beta header, whether by calling client.skills directly or by relying on client.beta.skills on a new-enough SDK version, since that alias itself stopped sending the header. Requests that still send skills-2025-10-02 explicitly keep the older, single-version delete behavior and the BetaSkill type name, exactly as they did before this SDK release.
The current, non-beta Skills API shape
With the beta header dropped, the Skills API's endpoints look like this, per Anthropic's current API reference:
# Create a Skill (multipart form-data, one file must be SKILL.md at the root)
curl https://api.anthropic.com/v1/skills \
-H "anthropic-version: 2023-06-01" \
-H "X-Api-Key: $ANTHROPIC_API_KEY" \
-F files='@SKILL.md' \
-F display_name="My custom skill"
# Delete a Skill (and, on a qualifying SDK, all of its versions)
curl https://api.anthropic.com/v1/skills/$SKILL_ID \
-X DELETE \
-H "anthropic-version: 2023-06-01" \
-H "X-Api-Key: $ANTHROPIC_API_KEY"
A created Skill returns an id, a display_name (derived from the SKILL.md frontmatter name field when you don't set one explicitly), a latest_version_id, and a source field distinguishing "custom" (yours, private to your workspace), "anthropic" (published by Anthropic, read-only), "anthropic_example", and "plugin" Skills. None of this is beta-gated behavior; it's the shape the endpoint returns with no header at all.
What GA doesn't touch
It's worth being precise about the boundaries here, since "Agent Skills" spans several products and only one of them went through this beta process at all:
- Claude Code Skills are unaffected, and always were: they're filesystem-based folders under
.claude/skills/or~/.claude/skills/, discovered and used without any API upload or beta header, and Claude Code's own Skills documentation never referencedskills-2025-10-02in the first place. - claude.ai's custom Skills upload as zip files through Settings on Pro, Max, Team, and Enterprise plans with code execution enabled, a separate surface with its own individual-user sharing model, also untouched by the API's beta status.
- Pre-built document Skills (PowerPoint, Excel, Word, PDF) were already usable by referencing
skill_idvalues likepptxorxlsx; GA doesn't add new pre-built Skills, only removes the header requirement around using any Skill, pre-built or custom, through the API. - Custom Skills still don't sync across surfaces. A Skill uploaded through the API is still not automatically available on claude.ai, and vice versa; GA changed the header requirement, not the sharing model documented in Anthropic's Agent Skills overview.
Why this matters beyond API integrators
Most of this site's coverage of Agent Skills is about the filesystem-based version: a SKILL.md folder that Claude Code, Codex CLI, Cursor, and other agents discover on disk. The Skills API is a different distribution path for the same underlying idea, used by teams building their own Claude-powered products rather than working inside an agentic CLI. A support tool built on the Claude API, for instance, might upload a custom Skill through /v1/skills so every agent session in that product gets the same domain knowledge, without redeploying the application every time the Skill's instructions change.
GA matters to that audience specifically because a production integration built against a beta feature carries real risk: Anthropic's own beta-headers documentation warns that beta features "may have breaking changes with notice" or be "deprecated or removed" outright. A team that shipped a Skills API integration in late 2025 or early 2026 was building on a foundation Anthropic hadn't yet committed to keeping stable. As of 19 August 2026, that commitment exists, which is a meaningful signal for anyone deciding whether the Skills API is solid enough to build a real product feature on, not just prototype with.
Troubleshooting
My integration still sends skills-2025-10-02 and I'm not sure if that's a problem. It isn't. Requests with the header keep working and keep the beta response shapes indefinitely as documented; nothing forces removal, and there's no deprecation timeline currently published for the header itself.
I removed the header and client.beta.skills.delete() now deletes more than I expected. That's the documented 27 August 2026 SDK change working as intended: once you're on a qualifying SDK version and off the beta header, deleting a Skill removes all of its versions, not just one. If you relied on deleting a single version while keeping others, you'll need the version-specific delete behavior the beta shape offered, which means staying on the header and an SDK release still typed to it.
A type in my code called BetaSkill no longer compiles. Check your SDK version against the list above (Python 1.2.0, TypeScript 0.122.0, Go 1.68.0, Java 2.59.0, Ruby 1.67.0, C# 12.44.0, or later). On those releases, the type is renamed BetaContainerSkill; update the reference rather than pinning an older SDK just to keep the old name, since the underlying type didn't change behavior, only its name.
I'm looking for this in Claude Code or claude.ai and can't find anything about a beta header. That's expected. Neither surface ever used the skills-2025-10-02 header; it's specific to the Claude API's /v1/skills endpoints and Messages API skill loading. Claude Code's skills documentation and claude.ai's Skills settings describe their own, separate mechanics.
Should you migrate off the header now
There's no forcing function to do this today. Requests that keep the skills-2025-10-02 header work exactly as they always have, on the older, single-version delete behavior and the BetaSkill type name, indefinitely as far as anything currently documented states. The case for migrating anyway is the same case for any beta-to-GA move: a header your code no longer needs is one less thing to remember when debugging, and matching the current, documented shape rather than a frozen beta snapshot means your code won't be surprised by a future change to how the beta shape itself is handled. If your integration doesn't lean on the beta's single-version delete behavior specifically, dropping the header on a qualifying SDK version is low-risk, well-documented migration work rather than something that needs to happen under time pressure.
Where to go next
For the mechanics of using Agent Skills through the API day to day, see how to use agent skills with the Claude API. For the open-source skill Anthropic bundles with Claude Code and publishes for API use, see Anthropic's open-source Claude API skill explained. For the other Enterprise-facing endpoints that reached GA the same day, see the Admin API's user-management endpoints, now GA. Browse every skill cataloged on this site at getclaudeskills.com/skills.
Verified 30 August 2026 directly against Anthropic's Claude Platform release notes (the 19 August and 27 August 2026 entries, both read in full), the current Agent Skills overview and beta headers pages, and the live, non-beta Create Skill and Delete Skill API reference pages at platform.claude.com.
