FiberTraceboxFailure replay infrastructure
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Trace ID

trace_a5c65ebc-ebd5-4d88-a937-835ee5a30fd3

replayed
Amount
500 CKB
Mode
sandbox
Latency
84ms
Failure stage
capacity_probe
Sender
fiber-devnet-sender-01
Receiver
fiber-devnet-receiver-09

ROUTE_CAPACITY_INSUFFICIENT

Route capacity insufficient

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

Likely Causes

  • Outbound liquidity is below the payment size
  • One hop has a lower max HTLC than the payment amount
  • The route can carry smaller payments but not this full amount

Suggested Fixes

  • 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

Failure Timeline

Lifecycle events captured in milliseconds.

6 events
  1. 0ms
    request_receivedinfo

    Payment attempt created for 500 CKB

  2. 8ms
    invoice_validationsuccess

    Invoice fields parsed

  3. 18ms
    route_discoveryinfo

    Candidate routes loaded from sandbox graph

  4. 50ms
    policy_checkinfo

    Route policies evaluated

  5. 62ms
    capacity_probewarning

    Candidate path capacity: 320 CKB available for 500 CKB request

  6. 84ms
    capacity_probeerror

    Route capacity insufficient: max forwardable 320 CKB

Replay-to-Fix Results

same_conditions

Original amount, route, peer state, fee limit, timeout, and asset unchanged

failed

The original failure reproduces under the same conditions, confirming the fingerprint is stable.

91ms

reduced_amount_80

Reduced amount to 80%: 400 CKB

failed

400 CKB still exceeds the constrained route capacity, so the payment fails again.

70ms

reduced_amount_64

Reduced amount to 64%: 320 CKB

success

320 CKB matches the observed maximum forwardable capacity and settles.

58msSmallest-fix recommendation

increased_outbound_capacity

Added exact outbound route capacity deficit: 180 CKB

success

Adding 180 CKB raises route capacity to the original payment amount and removes the constrained hop.

66ms

alternate_route

Selected alternate route excluding the failing condition

success

A route with different hops avoids the original failure point with slightly higher latency.

73ms

split_payment

Split payment into 250 CKB + 250 CKB

failed

The route has only 320 CKB total forwardable capacity. After the first part, the same static route cannot carry the second part, so the full 500 CKB payment is not completed.

79ms

Exportable Debug Report

Markdown and JSON report output for trace reviews and operator handoff.

# 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.
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