[DNM] feat(da): support fiber (not via c-node)

[julienrbrt]

Overview

Support Fiber client (based on https://github.com/celestiaorg/celestia-app/blob/63fbf31cca216fc4e067a9e1b3a3431115c7009b/fibre), but not via celestia node or apex for this PoC
celestiaorg/celestia-node#4892

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The latest Buf updates on your PR. Results from workflow CI / buf-check (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	⏩ skipped	✅ passed	✅ passed	Apr 24, 2026, 9:38 PM

[claude]

Claude finished @julienrbrt's task in 3m 12s —— View job

---

Code Review: [DNM] feat(da): support fiber (not via c-node)

• Read AGENTS.md for repo-specific guidelines
• Read all changed files
• Review core Fiber DA client implementation
• Review configuration changes
• Review sequencer integration
• Review testing infrastructure
• Review tools/celestia-node-fiber package
• Post comprehensive review feedback

---

This is a well-structured PoC for integrating the Fiber DA protocol. The layered design (interface → mock → adapter → integration tests) is solid and the flattenBlobs/splitBlobs encoding is correct and well-tested. Below are the issues found, ordered by severity.

---

Critical

1. context.Background() in Submit ignores caller cancellation
block/internal/da/fiber_client.go:92

result, err := c.fiber.Upload(context.Background(), namespace[len(namespace)-10:], flat)

The passed ctx is completely discarded — uploads will not respect caller cancellation or deadlines. Change to ctx. Fix this →

2. panic in GetLatestDAHeight will crash the process
block/internal/da/fiber_client.go:303-305

func (c *fiberDAClient) GetLatestDAHeight(context.Context) (uint64, error) {
    panic(fmt.Errorf("p2p should not be enabled"))
}

A panic in an interface method that could be called by any part of the node is not an acceptable sentinel. Return (0, errors.ErrUnsupported) or a domain-specific error instead. Fix this →

---

High

3. Subscriber index corruption in MockDA.Listen under concurrent close
block/internal/da/fibremock/mock.go:218-228

The cleanup goroutine captures idx at subscription time, but the swap-with-last removal strategy invalidates idx when a subscriber with a lower index is removed first. For example:

• Start with subscribers [A(idx=0), B(idx=1), C(idx=2)]
• A's context is cancelled: swap [0] with [2] → [C, B]. C is now at position 0 but its closure still holds idx=2.
• C's context is cancelled: last = len-1 = 1, idx (2) <= last (1) → false → no swap, subscribers = subscribers[:1] → [C]. C is never removed and its channel leaks.

A simple fix is to use a map[int]subscriber with an auto-incrementing key, or accept the O(n) linear scan on removal since this is a mock.

4. Subscribe swallows Listen errors from the goroutine
block/internal/da/fiber_client.go:253-265

blobCh, err := c.fiber.Listen(...)
if err != nil {
    c.logger.Error().Err(err).Msg("fiber listen failed")
    return  // closes out — caller receives closed channel with no error
}

The caller receives (out, nil) and only discovers the failure when out immediately closes. Consider returning the error synchronously (move Listen before launching the goroutine) or signalling via a side-channel. Fix this →

5. Namespace slice panics if namespace is shorter than 10 bytes
fiber_client.go:92, 141, 260

namespace[len(namespace)-10:]  // panics if len(namespace) < 10

There is no guard before this slicing in Submit, retrieve, or Subscribe. Add a length check and return a clear error. Fix this →

6. NewFiberDAClient panics on error in block/public.go
block/public.go:86-93

base, err := da.NewFiberClient(...)
if err != nil {
    panic(err)
}

NewFiberClient can fail (e.g., nil client). Callers like StartNode construct this in the request path — a panic here brings down the whole process. The function should return (FullDAClient, error). Fix this →

---

Medium

7. KeyringPath has no CLI flag
pkg/config/config.go:303 defines FiberDAConfig.KeyringPath but AddFlags in the same file registers no FlagDAFiberKeyringPath. Users cannot set the keyring directory from the CLI or environment. Either add the flag or remove the field.

8. Validate silently returns true for everything
fiber_client.go:318-326

for i := range results {
    results[i] = true  // not implemented
}
return results, nil

This bypasses blob integrity checks entirely without signalling to callers. Return errors.ErrUnsupported (like GetProofs does) so callers can decide how to handle unimplemented verification.

9. retrieve / RetrieveBlobs are identical
fiber_client.go:129-135

func (c *fiberDAClient) Retrieve(ctx context.Context, height uint64, namespace []byte) datypes.ResultRetrieve {
    return c.retrieve(ctx, height, namespace, true)
}
func (c *fiberDAClient) RetrieveBlobs(ctx context.Context, height uint64, namespace []byte) datypes.ResultRetrieve {
    return c.retrieve(ctx, height, namespace, false)
}

The bool parameter is named _ in retrieve — it has no effect. The two methods produce identical results. Either give the flag meaning or collapse them.

10. P2P broadcast suppressed for Fiber — undocumented
block/internal/executing/executor.go:631

if !e.config.DA.IsFiberEnabled() {
    // Broadcast header and data to P2P network

When Fiber is enabled, full nodes receive no P2P gossip. This is a significant protocol change that affects sync for non-sequencer nodes and deserves a doc comment explaining the rationale and expected sync path.

11. Listen performs a Download per event for DataSize
tools/celestia-node-fiber/listen.go:30-33
The comment acknowledges one FSP round-trip per blob. At high throughput this could saturate the connection. Consider making DataSize optional (0 = unknown) and letting consumers decide whether to resolve it.

---

Minor

12. Magic number fiberSubscribeChanSize = 42
fiber_client.go:248 — the value 42 carries no semantic meaning. A constant named something like defaultSubscriptionBuffer with a comment explaining the rationale (e.g., matching upstream buffer) would be clearer.

13. TODO blocks in returned ResultSubmit
fiber_client.go:115, 125

Height: 0, /* TODO */

The zero height is returned to callers including the coordinator. Several tests are skipped because of this. Track the root cause (Fiber protocol doesn't confirm celestia block height synchronously) as a GitHub issue rather than leaving silent /* TODO */ in results.

14. Hardcoded blobExpiration = 24 * time.Hour in adapter
tools/celestia-node-fiber/adapter.go:28
The placeholder expiry could mislead callers into assuming blobs are retained longer (or shorter) than the actual protocol. The TODO is noted, but consider returning a zero ExpiresAt (meaning "unknown") until the real value is available.

15. Comment typo in config constants
pkg/config/config.go:102

// FlagConsensusChainID is the Chain ID of the celestia app node
FlagDAFiberConsensusChainID = FlagPrefixEvnode + "da.fiber.consensus_chain_id"

The comment says FlagConsensusChainID but the constant is FlagDAFiberConsensusChainID.

16. UploadConcurrency mentioned but not defined
pkg/config/config.go:306

// UploadConcurrency limits the number of concurrent upload connections

The comment ends the struct body — there is no actual field. Either add the field or remove the comment.

17. Missing error log in forwardFibreBlobs on skip
tools/celestia-node-fiber/listen.go:71-76
When fibreBlobToEvent fails, the event is silently dropped. A logger.Warn() or logger.Debug() would significantly aid debugging in production.

---

Testing

The unit and mock test coverage is good. A few notes:

• Multiple Retrieve/Subscribe/Validate tests are skipped pending height tracking (t.Skip("pending Height tracking from fiber DA")). These should be tracked in issues so they don't remain skipped indefinitely.
• The //go:build fibre integration tests are a clean opt-in pattern.
• TestMockDA_DeterministicBlobID uploads the same payload twice, verifying the blob ID is content-addressed — this would silently coalesce two different uploads at the same height if they share content. Consider whether this is intentional.

[codecov]

Codecov Report

❌ Patch coverage is 90.65657% with 37 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.16%. Comparing base (2865d6d) to head (4485d91).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
block/public.go	0.00%	12 Missing ⚠️
block/internal/da/fibremock/mock.go	90.90%	5 Missing and 5 partials ⚠️
block/internal/da/fiber_client.go	96.74%	5 Missing and 3 partials ⚠️
pkg/sequencers/solo/sequencer.go	61.53%	5 Missing ⚠️
pkg/config/config.go	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3244      +/-   ##
==========================================
+ Coverage   62.33%   63.16%   +0.82%     
==========================================
  Files         122      124       +2     
  Lines       12873    13258     +385     
==========================================
+ Hits         8024     8374     +350     
- Misses       3968     3995      +27     
- Partials      881      889       +8     

Flag	Coverage Δ
combined	63.16% <90.65%> (+0.82%)	⬆️

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