feat: validate routing CEL expressions at write time in create/update handlers

[impoiler]

Summary

Routing rule CEL expressions were previously only compiled and validated at first evaluation, meaning a malformed expression could be persisted successfully and fail silently at runtime. This PR adds write-time validation so that invalid CEL expressions are rejected with a 400 error when a routing rule is created or updated.

Changes

• Added ValidateRoutingCELExpression in plugins/governance/routing.go that builds the CEL environment once (via sync.Once) and compiles the normalized expression, returning a descriptive error on any syntax or type problem. Empty/whitespace-only expressions are treated as match-all and pass validation.
• Wired ValidateRoutingCELExpression into the createRoutingRule and updateRoutingRule HTTP handlers so invalid expressions are rejected at write time. The update handler only validates when CelExpression is explicitly supplied, so unrelated updates (e.g. toggling enabled) are unaffected.
• Added TestValidateRoutingCELExpression covering valid expressions (empty, whitespace, equality, contains, header lookup, conjunction) and invalid ones (unknown identifiers, syntax errors, type mismatches, dangling operators).

Type of change

• Bug fix
• Feature
• Refactor
• Documentation
• Chore/CI

Affected areas

• Core (Go)
• Transports (HTTP)
• Providers/Integrations
• Plugins
• UI (React)
• Docs

How to test

go test ./plugins/governance/... ./transports/bifrost-http/...

To validate manually, attempt to create or update a routing rule with an invalid CEL expression (e.g. model ==) and confirm a 400 response is returned with a descriptive error message. A valid expression (e.g. model == "gpt-4o") should be accepted as before.

Screenshots/Recordings

N/A

Breaking changes

• Yes
• No

Related issues

Security considerations

CEL expressions are now compiled before persistence, reducing the risk of storing expressions that could cause unexpected runtime behaviour or panics during evaluation.

Checklist

• I read docs/contributing/README.md and followed the guidelines
• I added/updated tests where appropriate
• I updated documentation where needed
• I verified builds succeed (Go and UI)
• I verified the CI pipeline passes locally if applicable

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Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 0b6971bc-77ba-439b-9b3d-e55d16e395d7

📥 Commits

Reviewing files that changed from the base of the PR and between 0698f7b and 8b87614.

📒 Files selected for processing (3)

• plugins/governance/routing.go
• plugins/governance/routing_test.go
• transports/bifrost-http/handlers/governance.go

📝 Walkthrough

Walkthrough

Routing rule handlers now validate CEL expressions before creating or updating rules. A cached governance helper normalizes map keys, performs routing schema validation, compiles expressions, and reports invalid input. Tests cover valid, empty, and invalid expressions.

Changes

Routing CEL validation

Layer / File(s)	Summary
Routing CEL validation helper plugins/governance/routing.go, plugins/governance/routing_test.go	Adds cached CEL environment initialization, map-key normalization, schema validation, compilation, and table-driven coverage for valid and invalid expressions.
Routing rule handler integration transports/bifrost-http/handlers/governance.go	Validates expressions during rule creation and conditional validation during updates, returning HTTP 400 for invalid supplied expressions.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant HTTPClient
  participant createRoutingRule
  participant ValidateRoutingCELExpression
  participant routing.ValidateCELExpression
  HTTPClient->>createRoutingRule: Submit cel_expression
  createRoutingRule->>ValidateRoutingCELExpression: Validate expression
  ValidateRoutingCELExpression->>routing.ValidateCELExpression: Validate normalized expression
  routing.ValidateCELExpression-->>ValidateRoutingCELExpression: Return validation result
  ValidateRoutingCELExpression-->>createRoutingRule: Return error or success
  createRoutingRule-->>HTTPClient: Return HTTP 400 or create rule

Loading

Suggested reviewers: akshaydeo, pratham-mishra04

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: validating routing CEL expressions at write time in create/update handlers.
Description check	✅ Passed	The description follows the template well, covering summary, changes, testing, impacted areas, security, and breaking changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 07-16-feat_routing_rules_cel_expression_validation_backend

---

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

[impoiler]

• fix: remove isFetching prop from VirtualKeysTable and simplify empty state check #5297
• feat: add raw CEL mode to routing rule builder with inline error display and round-trip edit support #5289
• feat: validate routing CEL expressions at write time in create/update handlers #5288 👈 (View in Graphite)
• dev

This stack of pull requests is managed by Graphite. Learn more about stacking.

[greptile-apps]

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed code.

Important Files Changed

Filename	Overview
plugins/governance/routing.go	Adds reusable write-time CEL validation using the runtime routing environment and normalization logic.
plugins/governance/routing_test.go	Adds table-driven tests for accepted and rejected CEL expressions.
transports/bifrost-http/handlers/governance.go	Validates supplied CEL expressions before routing rules are created or updated.

_{Reviews (2): Last reviewed commit: "feat: routing rules CEL expression valid..." | Re-trigger Greptile}

[coderabbitai]

🧹 Nitpick comments (1)

transports/bifrost-http/handlers/governance.go (1)

4007-4011: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add handler-level regression tests for the 400 contract.

The helper tests cover compilation, but not that create/update handlers return 400 and skip persistence when cel_expression is invalid. Add focused tests for both paths, including an update where the field is omitted.

Also applies to: 4124-4129

🤖 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 `@transports/bifrost-http/handlers/governance.go` around lines 4007 - 4011, Add
focused regression tests for the create and update governance handlers around
their ValidateRoutingCELExpression calls, asserting malformed cel_expression
returns HTTP 400 and does not persist changes. Include an update case with
cel_expression omitted to confirm it remains valid and follows the existing
update behavior.

🤖 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.

Nitpick comments:
In `@transports/bifrost-http/handlers/governance.go`:
- Around line 4007-4011: Add focused regression tests for the create and update
governance handlers around their ValidateRoutingCELExpression calls, asserting
malformed cel_expression returns HTTP 400 and does not persist changes. Include
an update case with cel_expression omitted to confirm it remains valid and
follows the existing update behavior.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: a4a8cb09-e54b-4dad-820e-a39952573b6e

📥 Commits

Reviewing files that changed from the base of the PR and between c0909f9 and 0698f7b.

📒 Files selected for processing (3)

• plugins/governance/routing.go
• plugins/governance/routing_test.go
• transports/bifrost-http/handlers/governance.go

[Pratham-Mishra04]

Merge activity

• Jul 17, 11:09 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Jul 17, 11:10 AM UTC: Graphite rebased this pull request as part of a merge.
• Jul 17, 11:11 AM UTC: Graphite rebased this pull request as part of a merge.
• Jul 17, 11:11 AM UTC: @Pratham-Mishra04 merged this pull request with Graphite.