fix(acp): forward allowlisted client headers on all ACP paths

[rehmanmuradali]

Summary

• get_headers(agent) is called from several ACP paths (send_message_stream, create_task, cancel/interrupt) without threading the inbound client headers.
• As a result filter_request_headers(None) returned {}, so no allowlisted client x-* headers ever reached the agent.
• Fall back to the inbound request headers when callers don't pass them, so the existing allowlist actually forwards them.

Test plan

• Trigger an ACP path that previously dropped headers (e.g. send_message_stream) and confirm allowlisted client x-* headers now reach the agent.
• Confirm existing behavior is preserved when request_headers is explicitly passed.

Made with Cursor

Greptile Summary

This PR fixes a bug where allowlisted x-* client headers were never forwarded to the agent on most ACP paths because get_headers() received request_headers=None and filter_request_headers(None) returned {}. The fix adds a four-line fallback that reads self._request.headers when no headers are explicitly passed, consistent with how get_delegation_headers() already reads the same source.

• get_headers() now falls back to dict(self._request.headers) when request_headers is None; the existing BLOCKED_HEADERS + x-*-allowlist filtering in filter_request_headers() is unchanged, so credentials (authorization, x-api-key, etc.) remain blocked.
• Callers that pass request_headers={} explicitly opt out of the fallback — the empty dict short-circuits filter_request_headers and no client headers are forwarded.
• Two new unit tests cover both the fallback path and the explicit-empty-dict opt-out, including assertions that blocked headers (authorization, x-api-key) are not forwarded.

Confidence Score: 5/5

Safe to merge. The change is minimal and scoped to a single fallback in get_headers(); the security-sensitive filtering path (filter_request_headers + BLOCKED_HEADERS) is untouched.

The four-line fallback is consistent with how get_delegation_headers() already reads self._request.headers. Credential headers remain blocked by the existing allowlist. The two new tests directly exercise both the fallback and the opt-out paths with correct assertions on sensitive header names.

Files Needing Attention: No files require special attention.

Important Files Changed

Filename	Overview
agentex/src/domain/services/agent_acp_service.py	Adds a 4-line fallback in get_headers() so inbound x-* client headers are forwarded when callers don't explicitly pass request_headers. Security filtering via filter_request_headers and BLOCKED_HEADERS is unchanged.
agentex/tests/unit/services/test_agent_acp_service.py	Adds two new unit tests covering the fallback path (omitted request_headers uses inbound headers) and the explicit empty-dict opt-out path. Both cover the security-critical header filtering cases.

Sequence Diagram

sequenceDiagram
    participant Client
    participant ACPPath as ACP Path
    participant GetHeaders as get_headers
    participant FilterHeaders as filter_request_headers
    participant AgentPod as Agent Pod

    Client->>ACPPath: "HTTP request with x-* headers"
    ACPPath->>GetHeaders: get_headers(agent)

    alt Before fix
        GetHeaders->>FilterHeaders: filter_request_headers(None)
        FilterHeaders-->>GetHeaders: "{} empty dict"
    else After fix
        GetHeaders->>GetHeaders: "request_headers = dict(self._request.headers)"
        GetHeaders->>FilterHeaders: filter_request_headers(inbound headers)
        FilterHeaders-->>GetHeaders: "allowlisted x-* headers only"
    end

    GetHeaders-->>ACPPath: merged headers with delegation + auth + x-request-id
    ACPPath->>AgentPod: JSON-RPC with forwarded allowlisted headers

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_{Reviews (5): Last reviewed commit: "test(acp): cover get_headers inbound-hea..." | Re-trigger Greptile}

[Copilot]

Pull request overview

This PR fixes ACP header propagation by ensuring allowlisted client x-* headers are forwarded to agent ACP servers on ACP paths where get_headers(agent) was previously called without explicit request_headers.

Changes:

• Add a fallback in AgentACPService.get_headers() to use inbound Request.headers when request_headers is not provided.
• Preserve existing behavior when request_headers is explicitly passed (including opting out by passing {}).

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