[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

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 802ace03-f982-4c73-bb6b-cb92876703ae

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch julien/fiber

Tip

💬 Introducing Slack Agent: The best way for teams to turn conversations into code.

Slack Agent is built on CodeRabbit's deep understanding of your code, so your team can collaborate across the entire SDLC without losing context.

• Generate code and open pull requests
• Plan features and break down work
• Investigate incidents and troubleshoot customer tickets together
• Automate recurring tasks and respond to alerts with triggers
• Summarize progress and report instantly

Built for teams:

• Shared memory across your entire org—no repeating context
• Per-thread sandboxes to safely plan and execute work
• Governance built-in—scoped access, auditability, and budget controls

One agent for your entire SDLC. Right inside Slack.

👉 Get started

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[github-actions]

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	May 6, 2026, 5:00 PM

[claude]

Claude finished @julienrbrt's task in 6m 35s —— View job

---

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

Note: This is a PoC/DNM branch. Review focuses on correctness issues and architectural risks before productionization.

• Read AGENTS.md and project guidelines
• Analyze PR structure and key changed files
• Review fiber DA client implementation
• Review DA submitter changes
• Review configuration changes
• Review cache and block package changes
• Review tools (celestia-node-fiber, talis)
• Compile and post final review

---

Overview

This PR adds a Fiber/Fibre DA client as an alternative to the default JSON-RPC blob path, introducing a full upload/download/subscribe cycle against Celestia's Fibre protocol. The implementation is well-structured with a clear interface (fiber.DA), a good mock (fibremock), and a real adapter in tools/celestia-node-fiber. The DA submitter refactor and batching strategy improvements are solid engineering. Below are issues, ordered by severity.

---

Critical Issues

1. context.Background() ignores caller's cancellation in Submit

block/internal/da/fiber_client.go:102

result, err := c.fiber.Upload(context.Background(), nsID, flat)

The passed ctx is ignored here — the upload will run until completion (or internal error) regardless of whether the caller cancels or times out. For a 128 MiB Fibre upload this could hang for tens of seconds after the node's submission loop is cancelled. Should be ctx.

Fix this →

---

2. DefaultMaxBlobSize global is now Fibre's 128 MiB cap — wrong for all non-Fibre nodes

block/internal/common/consts.go

The comment itself calls this a HACK:

"this default is correct for fiber-enabled deployments but WRONG for the legacy JSON-RPC blob client path — the bridge/chain rejects blobs above its own (much smaller) cap"

Any non-Fibre deployment that upgrades without an ldflag override or code change will silently attempt to submit 128 MiB blobs and get rejected by the DA bridge. The SetMaxBlobSize global mutator (exported, unsynchronized) in block/public.go:26 makes this worse since it's a package-level side-effect with no guard.

Recommendation: Don't change the default; make this per-DA-backend. If the refactor is deferred (TODO(throughput-cleanup)), at minimum ensure the non-Fiber default is preserved (e.g., keep 5 MiB default, let evnode-fibre tool set it as it already does via block.SetMaxBlobSize(100 << 20)).

---

Significant Issues

3. Submit always returns Height: 0 — breaks DA inclusion tracking

block/internal/da/fiber_client.go:142,149

Height: 0, /* TODO */

The submitter uses res.Height to record DA inclusion in the cache (cache.SetHeaderDAIncluded, cache.SetDataDAIncluded). With Fiber, all headers and data are recorded as included at DA height 0. This will break processDAInclusionLoop which reads these heights to advance the rollup state. The retrieve tests confirm this is known but deferred:

t.Skip("pending Height tracking from fiber DA")

This means the current Fibre integration cannot correctly track rollup liveness on the read path. The TODO must be resolved before this can be merged for any production use.

---

4. panic(err) in NewFiberDAClient is a public API anti-pattern

block/public.go:103

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

NewFiberClient only errors on nil client, and StartNode checks fiberClient == nil before calling this. But panicking in an exported function violates the principle that library code should not crash calling programs. The function signature should return (FullDAClient, error).

Fix this →

---

5. EVM app unconditionally creates a WebSocket DA client even when Fiber is enabled

apps/evm/cmd/run.go:62-68

blobClient, err := blobrpc.NewWSClient(cmd.Context(), logger, nodeConfig.DA.Address, nodeConfig.DA.AuthToken, "")
if err != nil {
    return fmt.Errorf("failed to create blob client: %w", err)
}
defer blobClient.Close()
daClient := block.NewDAClient(blobClient, nodeConfig, logger)

This code runs before StartNode regardless of whether Fiber is configured. If DA.Fiber.Enabled=true and no legacy WebSocket DA server is running, the app crashes here instead of proceeding to the Fiber path. The daClient created here is also used for the force-inclusion server and sequencer, meaning the EVM app has two independent DA clients (one created here, one inside StartNode).

---

6. FiberDAConfig.Validate() doesn't validate KeyringPath or KeyName

pkg/config/config.go:311-339

KeyringPath and KeyName are required for Fiber payment promise signing but are not validated at startup. An operator who omits them will get a runtime error deep in the Fibre client, not a clear startup failure.

Also, FlagDAFiberKeyringPath flag constant is missing — KeyringPath can only be set via config file, not via CLI --evnode.da.fiber.keyring_path.

Fix this →

---

7. ApplyFiberDefaults() must be called manually — not invoked in the common startup path

Config.ApplyFiberDefaults() sets critical tuning parameters (adaptive batching, 1s block time, 10 pending limit) that are required to prevent OOM under Fibre load. It is only called in tools/celestia-node-fiber/cmd/evnode-fibre/main.go:304. Any application that uses pkg/cmd.StartNode with Fiber enabled (future integrators) will not get these defaults automatically and may OOM.

Consider calling ApplyFiberDefaults() inside StartNode when IsFiberEnabled() is true, or at minimum document this requirement prominently.

---

Minor Issues

8. Typo: heigth in GetLatestDAHeight

block/internal/da/fiber_client.go:370

heigth, err := c.fiber.Head(headCtx)
// ...
return heigth, nil

Fix this →

---

9. Silent error swallowing in forwardFibreBlobs

tools/celestia-node-fiber/listen.go:73

event, err := a.fibreBlobToEvent(ctx, b.Blob, height)
if err != nil {
    continue  // silently dropped
}

If a blob is garbage-collected from FSPs between the subscription event and the download, the error is silently dropped. This creates an invisible data gap in the sync stream. A warning log with blob ID and height would make this diagnosable.

---

10. retrieve silently ignores the includeHeader discriminator

block/internal/da/fiber_client.go:198

func (c *fiberDAClient) retrieve(ctx context.Context, height uint64, namespace []byte, _ bool) datypes.ResultRetrieve {

Both Retrieve and RetrieveBlobs call the same retrieve function with the bool discarded. The distinction between these two methods is meaningful to callers. This should either be implemented or clearly noted as a PoC limitation.

---

11. GetProofs returns an opaque error string instead of a typed sentinel

block/internal/da/fiber_client.go:379

return []datypes.Proof{}, fmt.Errorf("not implemented")

Use errors.ErrUnsupported (Go 1.21+) so callers can use errors.Is to detect unimplemented operations.

---

12. MockDA subscriber removal can remove the wrong subscriber

block/internal/da/fibremock/mock.go:226-235

The swap-with-last cleanup uses the index captured at subscribe time. With ≥3 concurrent subscribers being cancelled, the captured idx can end up pointing to a different subscriber after earlier cleanups rearrange the slice. In pathological cases a zombie subscriber remains in the slice after its context is done, and a subsequent Upload may attempt to send on a closed channel (panic). This is a test-only mock but correctness is still expected.

---

Architecture / Design Notes

Fiber height tracking is fundamentally unresolved. ResultSubmit.Height returns 0, which propagates to cache.SetHeaderDAIncluded(hash, 0, height). The DA submitter then tells the cache every header was included at DA height 0. The processDAInclusionLoop will stall or behave incorrectly. This is the most important design question to answer before the PoC can progress: does Fibre provide per-upload height, or does the listener's BlobEvent.Height need to feed back into the submitter? The current architecture separates submit and subscribe paths in a way that makes height correlation non-trivial.

DefaultMaxBlobSize as a global is a production footgun. The throughput-cleanup TODO is acknowledged in comments. Consider prioritizing this since it's a latent breakage for all non-Fiber users of the package.

tools/talis (large addition) — not reviewed in detail as it appears to be operational infrastructure, but it imports real cloud provider SDKs (AWS, GCP, DigitalOcean) and contains shell scripts. Ensure secrets (cloud credentials, SSH keys) are never checked in and the tool is not wired into CI without review.

---

[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%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.