docs(claude): distinguish access paths and feature limits

[aheritier]

🤖 Automated implementer agent — this comment was posted by the implementer bot from Docker Agentic Platform, not by a human developer

Summary

• Document existing Claude transports separately from their hosts: direct/custom Messages, Models Gateway, native Vertex prediction, Bedrock ConverseStream, and OpenAI-compatible aggregators. Distinguish OpenCode aliases from custom Messages and Azure aliases from native Foundry.
• Add a source-dated nine-model evidence matrix and exact card-sourced AWS IDs. The audit's 24 corroborated pairs + 2 limited Google announcements + 1 unsupported Mythos 5/Converse pair are not live-tested integration successes.
• Separate compaction service support from client integration/API limits, Google organization policy and account/consent prerequisites, and model-card restrictions. Explicitly leave complete 5.x core/fallback work to feat(Claude): ship atomic 5.x request and signed-history safety [P4; depends on #4582, #4576 contract] #4583/feat(Claude): enable end-to-end 5.x server fallback [P5; depends on #4583, #4576 contract] #4584; do not inherit proxy signature/beta/price guarantees.
• Cross-link existing provider and structured-output guides; correct generic profile/GDPR advice and the Vertex example's location. Docs only: no model defaults, code, schema, SDKs, dependencies or auth-policy changes. fix: make Haiku 5.5 requests compatible across Claude providers #4553 is untouched.

Closes #4581

Validation

• Markdownlint:127files,0errors; canonical115pages; llms.txt114entries/7sections; offline lychee0errors; Hugo120pages.
• Rendered checks:69 internal content links/fragment targets across all8changedpages, canonical URLs correct.
• Accessibility: pa11y-ci@3.1.0, Tier1+all8changedpages, 28/28URLs, both themes,0errors.
• Offline schema validation:56existing YAMLexamples/fragments on changedpages. Changed Vertex config resolves as version16 with debug config; no inference.
• task build, CGO_ENABLED=1 task test, CGO_ENABLED=1 task lint:passed (golangci-lint2.14.0 zeroissues). Compiler/linter/browser libraries provisioned after initial missing-tool/CGO setup failures.
• Fresh independent review: approve, no findings; signed and DCO signed-off commit.

Link-check caveat: full task docs-check-links did not pass: external AWS403s and pre-existing stable-docs404s/other forbidden endpoints. A newly detected tool-mode anchor was fixed; changed-page rendered links pass. Internal-only muffet also found an unchanged guides/headless → sandbox/#how-it-works anchor; it passes only when that baseline page and external URLs are excluded. No unrelated link repairs included.

Upstream docs build and ci / gate await the PR workflow. Docs-only Go CI jobs are expected skipped, not passed; local Go checks above are separate. No vendor inference, entitlement test or cloud/consent-setting change.

[Copilot]

🟡 Changes recommended

The custom Messages authentication table omits credential fallback behavior that can expose provider credentials to the configured host.

1 open finding

• Document provider credential fallback for custom base_url authentication · New

What changed in this PR

Documents Claude access paths, model availability, authentication, and provider-specific limitations.

Changes:

• Adds a source-dated Claude transport and model-support matrix.
• Clarifies Vertex, Bedrock, custom-host, and OpenCode behavior.
• Cross-links structured-output and provider guidance.

File	Description
docs/​providers/​overview/​index.md	Links to Claude access-path guidance.
docs/​providers/​anthropic/​index.md	Adds the primary access-path and compatibility guide.
docs/​providers/​google/​index.md	Clarifies native Vertex behavior and prerequisites.
docs/​providers/​bedrock/​index.md	Documents ConverseStream and feature limitations.
docs/​providers/​custom/​index.md	Distinguishes custom Messages and Azure paths.
docs/​providers/​opencode-zen/​index.md	Separates OpenAI-compatible and Messages paths.
docs/​providers/​opencode-go/​index.md	Clarifies alias protocol and feature guarantees.
docs/​configuration/​structured-output/​index.md	Refines provider-specific structured-output support.

🧠 Review effort: Balanced

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[aheritier]

Reviewed the eight-file documentation change for quality, performance, security, and relevance against #4581 and the implementation at this head. No blocking defects found. The transport/authentication distinctions and credential-disclosure warning align with the implementation; the evidence matrix distinguishes corroborated availability from limited-access announcements rather than claiming live-tested support. Future implementation work remains explicitly out of scope.

One optional readability improvement is noted inline. Relative links/heading targets and YAML examples were checked successfully. CI reports SUCCESS; documentation checks passed, while docs-only Go test/race/build jobs were skipped. Rendering/accessibility checks were verified through CI, not rerun locally; no live inference or entitlement tests were performed. This COMMENT is not an approval.

[aheritier]

Optional: Could we name the two mechanisms beside their beta IDs? AWS distinguishes threshold-triggered compaction from explicit on-demand compaction, but this paragraph identifies them only by dates. For example: ‘requires InvokeModel for both threshold-triggered compaction (compact-2026-01-12) and on-demand compaction (compact-2026-09-04); neither works through Converse.’ This makes the limitation understandable without opening the vendor reference and keeps the existing meaning.