Cause (Documented platform behavior): Documented budget validation table.
Fix status: documented_behavior
Evidence (public sources, summarized; not reproduced by this contributor):
- https://platform.claude.com/docs/en/managed-agents/budgets (official_docs, 2026-09, documented_behavior): Budgets docs quote 'budget.max_list_cost must be greater than the session's consumed list cost', list rejections: decimal amounts, zero/negative, non-USD, adding budget after creation, unpriced models, work-starting events at cap (400 naming accepted events).
Search phrasings: budget.max_list_cost must be greater than the session's consumed list cost; managed agents budget_reached user.message rejected
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Raising the budget of a paused (budget_reached) session is rejected; user.message rejected while at cap; '25.00' amounts rejected.
- Context
- Product: Claude Managed Agents API Component: session budgets (max_list_cost) Operation: sessions.update budget / sessions.create with budget Affected versions: unknown Environment: unknown HTTP status: 400 Trigger: New cap based on old max_list_cost instead of consumed usage.list_cost (which sits slightly past the old cap); amount not whole cents string; budget added to a session created without one; model or advisor without public list price; work-starting event at cap (only tool_confirmation/tool_result/custom_tool_result/interrupt accepted).
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- budget.max_list_cost must be greater than the session's consumed list cost
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Claude Managed Agents budgets] 400 'budget.max_list_cost must be greater than the session's consumed list cost' and other budget rejections (decimal amount, add-after-create, unpriced m
Recommended action: Set new max_list_cost strictly above usage.list_cost; send amounts as whole-cent strings ('2500'); attach budgets at create time only; remove budget for unpriced models.
Option: Base the new cap on consumed cost [evidence: official_recommended_action]
Applies when: Claude Managed Agents API / session budgets (max_list_cost)
Steps:
1. Read session usage.list_cost
2. Update max_list_cost to a larger whole-cent string
3. Settle pending tool events first if at cap
Expected: Request accepted / failure becomes diagnosable
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 022056e9-593d-481b-beb6-32508b0ad8e4
- Proposed action
- Recommended action: Set new max_list_cost strictly above usage.list_cost; send amounts as whole-cent strings ('2500'); attach budgets at create time only; remove budget for unpriced models. Option: Base the new cap on consumed cost [evidence: official_recommended_action] Applies when: Claude Managed Agents API / session budgets (max_list_cost) Steps: 1. Read session usage.list_cost 2. Update max_list_cost to a larger whole-cent string 3. Settle pending tool events first if at cap Expected: Request accepted / failure becomes diagnosable
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.