feat: support with-replacement sampling for weighted random failover

[fergusfinn]

Summary

• Bumps onwards to 0.13.0 which adds with_replacement and max_attempts to FallbackConfig
• Adds DB migration (065) with fallback_with_replacement (bool, default false) and fallback_max_attempts (nullable int) columns on deployed_models
• Wires the new fields through the full stack: DB models/handlers, API models, onwards sync, and dashboard UI
• Dashboard shows the new controls only for weighted random strategy when fallback is enabled

Test plan

• All 862 Rust tests pass
• All 384 TypeScript tests pass
• just lint rust and just lint ts pass
• cargo sqlx prepare --check passes
• Manual test: create a virtual model with "sample with replacement" enabled and verify it persists
• Manual test: edit routing config to toggle with-replacement and set max attempts

[railway-app]

🚅 Deployed to the control-layer-pr-704 environment in industrious-light

Service	Status	Web	Updated (UTC)
control-layer	🕒 Building (View Logs)	Web	Feb 17, 2026 at 11:43 am

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

Adds support for with_replacement sampling and max_attempts to composite-model fallback configuration, propagating the new settings from DB schema through the Rust API/sync layer to the dashboard UI, and updating the onwards dependency to consume the new fields.

Changes:

• Add DB columns for fallback_with_replacement and fallback_max_attempts and wire them through Rust DB models/handlers and API models.
• Sync the new fallback settings into onwards pool specs (requires onwards 0.13.0).
• Expose new controls in the dashboard for weighted-random routing when failover is enabled.

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
dwctl/src/sync/onwards_config.rs	Loads new fallback fields from DB and maps them into onwards fallback config.
dwctl/src/sync/endpoint_sync.rs	Updates test fixtures to include new fallback fields.
dwctl/src/sample_files/mod.rs	Updates sample/test config fixtures with new fallback fields.
dwctl/src/request_logging/batcher.rs	Updates integration test fixtures with new fallback fields.
dwctl/src/metrics/cache_info.rs	Updates test fixtures with new fallback fields.
dwctl/src/db/models/deployments.rs	Extends fallback config + create/update request/response structs to include new fields.
dwctl/src/db/handlers/deployments.rs	Extends SQL INSERT/SELECT/UPDATE paths to persist and load new fields.
dwctl/src/api/models/deployments/mod.rs	Extends API create/update/response models to include new fallback settings.
dwctl/migrations/065_add_fallback_with_replacement.sql	Adds new columns on deployed_models for the fallback settings.
dwctl/Cargo.toml	Bumps onwards dependency to 0.13.0.
dashboard/src/components/modals/CreateVirtualModelModal/CreateVirtualModelModal.tsx	Adds create-form controls for with-replacement and max-attempts.
dashboard/src/components/features/models/ModelInfo/ProvidersTab.tsx	Adds edit-routing controls for with-replacement and max-attempts.
dashboard/src/api/control-layer/types.ts	Extends dashboard API types with the new fallback fields.
Cargo.lock	Locks updated dependency graph after onwards bump.
.sqlx/query-*.json	Updates SQLx offline metadata for updated queries/columns.