fix(agent): continue truncated model turns

[iamjr15]

Summary

• Treat provider length finish reasons as nonterminal model turns.
• Checkpoint the partial response and continue durably with an internal instruction to split interrupted operations into smaller complete tool calls.
• Validate the SDK finish-reason contract at the agent boundary and accept only stop as tool-free semantic completion.
• Fail blocked, provider-error, and invalid terminal reasons explicitly instead of publishing incomplete work as successful.

Root cause

The production Pomodoro retry recovered its Daytona runtime correctly, but Claude reached its per-response output limit while forming the next operation. The Workflow used only the absence of parsed tool calls as its completion condition, so it finalized that truncated turn and exposed the sandbox readiness page.

Architecture

The Mastra adapter validates the six AI SDK finish reasons. Cloudflare Workflow owns the policy: tool calls execute durably; length appends a non-visible continuation message and starts another checkpointed model turn; only stop completes a tool-free run. This keeps semantic completion in charge without adding a step, token, duration, or cost ceiling.

Decisions

Decision	Choice	Reason
Handle truncation in Workflow	Durable continuation	It preserves replay safety and applies to every provider and run type.
Preserve partial response history	Append an internal user continuation message	The next turn sees the exact work already attempted and avoids repeating completed actions.
Keep provider output settings unchanged	No fixed output-token override	A larger fixed cap only postpones truncation and does not establish correct completion semantics.
Reject non-stop terminal reasons	Explicit upstream failure	Content filtering and provider errors are not successful outcomes.

Production evidence

• Run 019fe1b3-af54-7a69-bd1d-0cd940842e41 completed after model turn 5 returned finishReason: "length" with no tool call.
• The replacement Daytona sandbox was healthy and mounted the correct durable volume, isolating this from the sandbox recovery issue fixed in fix: fail over unhealthy Daytona sandbox hosts #183 and refactor(sandbox): normalize Daytona recovery errors #184.

Verification

• pnpm lint
• pnpm typecheck
• pnpm turbo build --force
• pnpm deadcode
• pnpm architecture:check
• pnpm turbo skills:build
• production flow will be repeated after merge and exact-SHA Cloudflare deployment

How to review

1. Review the finish-reason schema in packages/agent-core/src/mastra/durable-agent-step.ts.
2. Review the durable loop policy in apps/agent-worker/src/durable-objects/agent-run-workflow.ts.
3. Confirm the shared schema is enforced by agent-run-workflow-runtime.ts and the README contract matches the implementation.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
cheatcode	Skipped		Aug 8, 2026 2:19pm