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 header-forwarding gap in the ACP service: get_headers(agent) was called without request_headers on several code paths (send_message_stream, create_task, cancel/interrupt), causing filter_request_headers(None) to return {} and silently drop all allowlisted client x-* headers.

• Core fix (agent_acp_service.py): When request_headers is None, fall back to dict(self._request.headers) before filtering, so the existing security allowlist (x-* prefix, BLOCKED_HEADERS exclusion) now correctly forwards headers on all ACP code paths.
• Tests (test_agent_acp_service.py): Two new unit tests cover the fallback case (no explicit headers → inbound x-* forwarded, credentials blocked) and the explicit-empty-dict case (no fallback triggered, only x-request-id remains).

Confidence Score: 5/5

Safe to merge — minimal, well-targeted fallback that activates the already-existing security filter on code paths that previously bypassed it entirely.

The fix is four lines in one function, backed by two new unit tests that verify both the fallback and the explicit-override cases. The security allowlist was already correct — the only gap was that it was never reached when callers omitted request_headers. No new untested code paths are introduced.

Files Needing Attention: No files require special attention.

Important Files Changed

Filename	Overview
agentex/src/domain/services/agent_acp_service.py	Four-line fix in get_headers: falls back to dict(self._request.headers) when request_headers is None, preserving existing security filtering via filter_request_headers.
agentex/tests/unit/services/test_agent_acp_service.py	Two new tests covering the fallback-to-inbound-headers path and the explicit-empty-dict (no-fallback) path; assertions correctly check credential blocking and allowlist behavior.

Sequence Diagram

sequenceDiagram
    participant Caller as ACP Caller
    participant GH as get_headers(agent)
    participant FR as filter_request_headers()
    participant RQ as self._request.headers

    Caller->>GH: get_headers(agent) [no request_headers]
    Note over GH: request_headers is None
    GH->>RQ: dict(self._request.headers)
    RQ-->>GH: raw inbound headers
    GH->>FR: filter_request_headers(inbound_headers)
    Note over FR: Allow x-* only, block credentials
    FR-->>GH: "safe x-* subset"
    GH->>GH: merge filtered + delegation + auth headers
    GH-->>Caller: final headers dict

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_{Reviews (3): 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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