fix(evm): don't create single sequencer for non-aggregator nodes

[tac0turtle]

Overview

P2P-only followers (no DA address configured) crash on startup with a nil pointer dereference:

panic: runtime error: invalid memory address or nil pointer dereference
github.com/evstack/ev-node/block/internal/da.NewForcedInclusionRetriever
block/internal/da/forced_inclusion_retriever.go:57

#3386 made the DA client nil when no DA address is set and guarded block/components.go and testapp's createSequencer, but the EVM app's createSequencer was missed: it unconditionally builds a single sequencer, whose forced-inclusion retriever constructor calls GetForcedInclusionNamespace() on the nil client.

While verifying the follower paths, a second gap surfaced: the sequencer is only consumed via leaderFactory → newAggregatorMode, but promotable nodes start as followers (Aggregator=false) and are handed to the aggregator components on promotion. A plain !Aggregator guard (as added to testapp in #3386) leaves promotable nodes with a nil sequencer and breaks promotion.

Changes

• apps/evm/cmd/run.go: skip sequencer creation for nodes that are neither aggregator nor promotable. Plain followers run newSyncMode, which never touches the sequencer.
• apps/testapp/cmd/run.go: extend the feat: support p2p-only followers without DA #3386 guard to keep the sequencer for promotable followers, fixing the promotion path there too.
• pkg/cmd/run_node.go: require a DA address for promotable mode in ParseStartConfig, same as aggregator mode — a promoted proposer needs DA, so fail at config validation instead of later.
• pkg/sequencers/single/sequencer.go: fail fast with a clear error when NewSequencer receives a nil DA client — the sequencer dereferences it in several paths, so any future regression surfaces as an error instead of a SIGSEGV.
• Regression tests for the nil-client guard and the promotable DA-address validation.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Prevented sequencer creation for nodes that are neither aggregators nor promotable.
  • Added clearer startup validation when required data-availability configuration is missing (DA address and DA client).
• Tests
  • Added a test to ensure sequencer creation errors when the DA client is nil.
  • Expanded tests to confirm DA address requirements for both aggregator and promotable modes.

[coderabbitai]

📝 Walkthrough

Walkthrough

Sequencer creation now supports aggregator and promotable nodes while skipping followers. Startup validation requires a DA address for either mode, and single sequencer construction rejects nil DA clients with test coverage.

Changes

Sequencer guard behavior

Layer / File(s)	Summary
Aggregator and promotable DA validation pkg/cmd/run_node.go, pkg/cmd/run_node_test.go	Startup configuration requires a DA address when aggregator or promotable mode is enabled, with tests covering both flags.
Promotable sequencer creation and DA client validation apps/evm/cmd/run.go, apps/testapp/cmd/run.go, pkg/sequencers/single/sequencer.go, pkg/sequencers/single/sequencer_test.go	Sequencer creation is enabled for aggregators and promotable nodes, while NewSequencer rejects nil DA clients and returns a nil sequencer on error.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• evstack/ev-node#3214: Changes the single.NewSequencer invocation in the same test application sequencer-creation path.
• evstack/ev-node#3386: Changes DA and sequencer initialization behavior around DA availability and aggregator-like modes.

Suggested reviewers:tzdybal, auricom, gupadhyaya

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title matches the main EVM sequencer startup fix, though it omits the promotable-node nuance.
Description check	✅ Passed	The description includes the required Overview and clearly explains the context, rationale, and changes.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch marko/fix-p2p-only-sequencer-panic

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[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	⏩ skipped	Jul 16, 2026, 2:34 PM

[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

pkg/sequencers/single/sequencer_test.go (1)

117-122: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Assert the descriptive error message.

require.Error verifies only that some error occurred; it would still pass if the clear DA-client error were replaced by an unrelated generic failure. Assert the expected message with require.EqualError (or require.ErrorContains) to protect the new contract.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
In `@pkg/sequencers/single/sequencer_test.go` around lines 117 - 122, Update
TestNewSequencer_NilDAClient to assert the descriptive error returned by
NewSequencer using require.EqualError or require.ErrorContains, while preserving
the existing nil sequencer assertion. Match the expected DA-client validation
message to protect the intended error contract.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.
Inline comments:
In `@apps/evm/cmd/run.go`:
- Around line 163-165: Update the early-return logic in the node setup flow so
the BasedSequencer-and-non-Aggregator combination is validated before the
ordinary non-aggregator return. Preserve the existing configuration error from
the check near the BasedSequencer validation, while still returning nil for
valid non-aggregator nodes.
---
Nitpick comments:
In `@pkg/sequencers/single/sequencer_test.go`:
- Around line 117-122: Update TestNewSequencer_NilDAClient to assert the
descriptive error returned by NewSequencer using require.EqualError or
require.ErrorContains, while preserving the existing nil sequencer assertion.
Match the expected DA-client validation message to protect the intended error
contract.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 4db8d811-7e4f-4521-8f7e-f1fc52594f67

📥 Commits

Reviewing files that changed from the base of the PR and between b4b895b and 5960890.

📒 Files selected for processing (3)

• apps/evm/cmd/run.go
• pkg/sequencers/single/sequencer.go
• pkg/sequencers/single/sequencer_test.go

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.32%. Comparing base (8e8cdde) to head (6d941ab).

Additional details and impacted files

@@ Coverage Diff @@## main #3389 +/- ##
==========================================
+ Coverage 62.31% 62.32% +0.01% 
==========================================
Files 120 120 Lines 13452 13454 +2 ==========================================
+ Hits 8382 8385 +3 + Misses 4128 4127 -1 
Partials 942 942 

Flag	Coverage Δ
combined	62.32% <100.00%> (+0.01%)	⬆️

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