# FiberTracebox Report

## Trace Summary

- Trace ID: trace_a5c65ebc-ebd5-4d88-a937-835ee5a30fd3
- Payment status: replayed
- Amount: 500 CKB
- Sender: fiber-devnet-sender-01
- Receiver: fiber-devnet-receiver-09
- Mode: sandbox
- Latency: 84ms
- Failure time: 84ms
- Failure stage: capacity_probe
- Failure fingerprint: ROUTE_CAPACITY_INSUFFICIENT


## Root Cause

A route was discovered, but the available forwarding capacity was lower than the requested payment amount.





## Evidence Source

- Trace source: sandbox
- Replay mode: deterministic sandbox replay
- Live mutation: no
- RPC methods observed: not applicable
- Observed failure: not applicable
- Sandbox events are deterministic and safe for repeatable demos and CI.
- Replay-to-Fix changes simulated route conditions without moving funds.

## Timeline

| ms | stage | severity | message |
| --- | --- | --- | --- |
| 0 | request_received | info | Payment attempt created for 500 CKB |
| 8 | invoice_validation | success | Invoice fields parsed |
| 18 | route_discovery | info | Candidate routes loaded from sandbox graph |
| 50 | policy_check | info | Route policies evaluated |
| 62 | capacity_probe | warning | Candidate path capacity: 320 CKB available for 500 CKB request |
| 84 | capacity_probe | error | Route capacity insufficient: max forwardable 320 CKB |

## Replay Results

| strategy | changed condition | result | latency ms | recommended |
| --- | --- | --- | --- | --- |
| same_conditions | Original amount, route, peer state, fee limit, timeout, and asset unchanged | failed | 91 | no |
| reduced_amount_80 | Reduced amount to 80%: 400 CKB | failed | 70 | no |
| reduced_amount_64 | Reduced amount to 64%: 320 CKB | success | 58 | yes |
| increased_outbound_capacity | Added exact outbound route capacity deficit: 180 CKB | success | 66 | no |
| alternate_route | Selected alternate route excluding the failing condition | success | 73 | no |
| split_payment | Split payment into 250 CKB + 250 CKB | failed | 79 | no |



## Smallest-Fix Recommendation

Smallest route-capacity fix: Send at most 320 CKB now as a partial payment, or add capacity to send the full 500 CKB.

If the operator controls liquidity, add at least 180 CKB outbound route capacity.

Confidence: high

## Suggested Next Actions

- Reduce amount to the largest successful replay amount
- Add outbound route capacity on the constrained hop
- Use an alternate route with enough capacity for the full payment
- Send at most 320 CKB now as a partial payment, or add capacity to send the full 500 CKB.
- If the operator controls liquidity, add at least 180 CKB outbound route capacity.

## Mode Disclosure

Sandbox mode: deterministic simulated Fiber payment conditions are used for repeatable diagnostics.