Summary

Blueprint .bp files currently define HTTP headers inside step scope using a headers { ... } block.
However, during transpilation those headers are stored only in Step.headers, while HttpProbe.headers remains empty.

As a result, HTTP probes execute without the intended request headers.

Problem

Given a blueprint like:

blueprint "Test" {
    phase "test" {
        step "user agent" {
            probe http GET /user-agent
            headers { User-Agent: test-agent/1.0 }
            expect {
                status: 200
                body: "test-agent/1.0"
            }
        }
    }
}

• headers are parsed from step scope (Step.headers)
• probe http ... resolves to Probe::Http(HttpProbe { headers: HashMap::new(), ... })
• executor (crates/blueprint/src/executor/probes/http.rs) sends only probe.headers

    let mut builder = match probe.method {
        HttpMethod::GET => client.get(url),
        HttpMethod::POST => client.post(url),
        HttpMethod::PUT => client.put(url),
        HttpMethod::DELETE => client.delete(url),
        HttpMethod::PATCH => client.patch(url),
        HttpMethod::HEAD => client.head(url),
        HttpMethod::OPTIONS => client.request(reqwest::Method::OPTIONS, url),
    };


    for (k, v) in &probe.headers {
        let v = ctx.interpolate(v);
        builder = builder.header(k, v);
    }

So requests are sent without step-defined headers.

Root Cause

Scope mismatch between transpiler and executor:

• Transpiler puts headers in Step.headers
• Executor reads headers from HttpProbe.headers
• No transfer/merge happens between the two

Solution (implemented in this PR)

Adopted Approach 2: move headers from step scope to HTTP probe scope during transpilation.

What changed

In crates/blueprint/src/transpiler/resolve.rs (resolve_step):

• After resolving the probe, if probe type is HTTP:
  • move headers into HttpProbe.headers using std::mem::take
• Keep non-HTTP probe behavior unchanged

This ensures headers defined in step scope are available where execution expects them.

Alternatives considered

1. Change blueprint syntax/design (define headers inline on probe)

   • Rejected for now: Architectural Decision

2. Move headers during transpilation ✅ (chosen)

3. Inject/override headers at execution time from Step

   • Rejected: executor currently operates on probe-level data; introducing step-to-probe coupling at runtime is not clean/feasible in current structure.

Tests

Added regression test in crates/blueprint/src/transpiler/resolve.rs:

• test_http_step_headers_are_moved_into_probe_headers

Validates that:

• step-level headers { ... } are present in Probe::Http.headers
• Step.headers is empty after move (no duplication)