Sentry: cockroachkvs.go:327: runtime error: slice bounds out of range [:-89] (1) attached stack trace -- stack trace: | github.com/cockroachdb/pebble/cockroachkvs.Compare | external/com_github_...

This issue was auto filed by Sentry. It represents a crash or reported error on a live cluster with telemetry enabled.

Sentry Link: [https://cockroach-labs.sentry.io/issues/7725857611/?referrer=webhooks_plugin](https://cockroach-labs.sentry.io/issues/7725857611/?referrer=webhooks_plugin)

Panic Message:

```
cockroachkvs.go:327: runtime error: slice bounds out of range [:-89]
(1) attached stack trace
-- stack trace:
| github.com/cockroachdb/pebble/cockroachkvs.Compare
| external/com_github_cockroachdb_pebble/cockroachkvs/cockroachkvs.go:327
| github.com/cockroachdb/pebble/sstable.(*Writer).addRangeKeySpanToFragmenter
| external/com_github_cockroachdb_pebble/sstable/writer.go:250
| github.com/cockroachdb/pebble/sstable.(*Writer).RangeKeyDelete
| external/com_github_cockroachdb_pebble/sstable/writer.go:240
| github.com/cockroachdb/pebble/tool.(*dbT).runExcise
| external/com_github_cockroachdb_pebble/tool/db.go:733
| github.com/spf13/cobra.(*Command).execute
| external/com_github_spf13_cobra/command.go:920
| github.com/spf13/cobra.(*Command).ExecuteC
| external/com_github_spf13_cobra/command.go:1044
| github.com/spf13/cobra.(*Command).Execute
| external/com_github_spf13_cobra/command.go:968
| github.com/cockroachdb/cockroach/pkg/cli.Run
| cli.go:301
| github.com/cockroachdb/cockroach/pkg/cli.doMain
| cli.go:140
| github.com/cockroachdb/cockroach/pkg/cli.Main
| cli.go:65
| main.main
| pkg/cmd/cockroach/main.go:21
| runtime.main
| GOROOT/src/runtime/proc.go:272
| runtime.goexit
| src/runtime/asm_arm64.s:1223
Wraps: (2) runtime error: slice bounds out of range [:-89]
Error types: (1) *withstack.withStack (2) runtime.boundsError
-- report composition:
runtime.boundsError
cockroachkvs.go:327: *withstack.withStack (top exception)
```

Stacktrace (expand for inline code snippets):

[src/runtime/asm_arm64.s#L1222-L1224](src/runtime/asm_arm64.s#L1222-L1224)
[GOROOT/src/runtime/proc.go#L271-L273](GOROOT/src/runtime/proc.go#L271-L273)
[pkg/cmd/cockroach/main.go#L20-L22](pkg/cmd/cockroach/main.go#L20-L22)
[cli.go#L64-L66](cli.go#L64-L66)
[cli.go#L139-L141](cli.go#L139-L141)
[cli.go#L300-L302](cli.go#L300-L302)
[external/com_github_spf13_cobra/command.go#L967-L969](external/com_github_spf13_cobra/command.go#L967-L969)
[external/com_github_spf13_cobra/command.go#L1043-L1045](external/com_github_spf13_cobra/command.go#L1043-L1045)
[external/com_github_spf13_cobra/command.go#L919-L921](external/com_github_spf13_cobra/command.go#L919-L921)
[external/com_github_cockroachdb_pebble/tool/db.go#L732-L734](external/com_github_cockroachdb_pebble/tool/db.go#L732-L734)
[external/com_github_cockroachdb_pebble/sstable/writer.go#L239-L241](external/com_github_cockroachdb_pebble/sstable/writer.go#L239-L241)
[external/com_github_cockroachdb_pebble/sstable/writer.go#L249-L251](external/com_github_cockroachdb_pebble/sstable/writer.go#L249-L251)
[external/com_github_cockroachdb_pebble/cockroachkvs/cockroachkvs.go#L326-L328](external/com_github_cockroachdb_pebble/cockroachkvs/cockroachkvs.go#L326-L328)

```
src/runtime/asm_arm64.s in runtime.goexit at line 1223
GOROOT/src/runtime/proc.go in runtime.main at line 272
pkg/cmd/cockroach/main.go in main.main at line 21
cli.go in pkg/cli.Main at line 65
cli.go in pkg/cli.doMain at line 140
cli.go in pkg/cli.Run at line 301
external/com_github_spf13_cobra/command.go in github.com/spf13/cobra.(*Command).Execute at line 968
external/com_github_spf13_cobra/command.go in github.com/spf13/cobra.(*Command).ExecuteC at line 1044
external/com_github_spf13_cobra/command.go in github.com/spf13/cobra.(*Command).execute at line 920
external/com_github_cockroachdb_pebble/tool/db.go in github.com/cockroachdb/pebble/tool.(*dbT).runExcise at line 733
external/com_github_cockroachdb_pebble/sstable/writer.go in github.com/cockroachdb/pebble/sstable.(*Writer).RangeKeyDelete at line 240
external/com_github_cockroachdb_pebble/sstable/writer.go in github.com/cockroachdb/pebble/sstable.(*Writer).addRangeKeySpanToFragmenter at line 250
external/com_github_cockroachdb_pebble/cockroachkvs/cockroachkvs.go in github.com/cockroachdb/pebble/cockroachkvs.Compare at line 327
```

### Tags

| Tag | Value |
| --- | --- |
| Command | debug pebble db excise |
| Environment | v25.4.5 |
| Go Version | go1.23.12 X:nocoverageredesign |
| Platform | linux arm64 |
| Distribution | CCL |
| Cockroach Release | v25.4.5 |
| Cockroach SHA | a5d3d359798dfbfa7a3cfd129441674afe498592 |
| # of CPUs | 4 |
| # of Goroutines | 10 |

Jira issue: CRDB-68180

Start with the reported stack trace at external/com_github_cockroachdb_pebble/cockroachkvs/cockroachkvs.go:327 and trace the call through sstable/writer.go and tool/db.go. Run the `debug pebble db excise` command against a case that reaches this path; done means the reported slice-bounds panic no longer occurs on the v25.4.5 arm64 scenario.

Written by the indexing model from the issue text.