feat(otel): capture true Execute-Agent-CLI start time so gh-aw.agent span excludes pre-agent overhead

[Copilot]

✨ Enhancement

What does this improve?

The gh-aw.<job>.agent OTel span started from GITHUB_AW_OTEL_JOB_START_MS (end of actions/setup), silently including workspace audit + CLI proxy startup (often 10–60 s of Docker pull) in the "LLM execution" duration. A DevOps engineer had no way to isolate true LLM time.

Why is this valuable?

After this change, the gh-aw.<job>.agent span starts precisely when the Execute Agent CLI step begins on the runner host — before the AWF container launches but after all pre-agent steps complete.

Implementation approach:

• New constant AgentCLIStartMsPath = "/tmp/gh-aw/agent_cli_start_ms.txt" (engine_output.go)

• BuildAWFCommand (awf_helpers.go) — prepends a timestamp write as the very first host command in every generated run: block, before PathSetup, before the AWF container launches:

  printf '%s' "$(date +%s%3N)" > /tmp/gh-aw/agent_cli_start_ms.txt

• Non-AWF paths — same printf line added as first command in the else-branch of all six engine files: claude_engine.go, codex_engine.go, gemini_engine.go, pi_engine.go, crush_engine.go, copilot_engine_execution.go

• sendJobConclusionSpan (send_otlp_span.cjs) — replaces the hard-coded agentStartMs = options.startMs with a read of agent_cli_start_ms.txt, falling back to options.startMs when the file is absent or invalid (backward-compatible with older compiled workflows):

  const agentStartMs = (() => {
    try {
      const raw = fs.readFileSync("/tmp/gh-aw/agent_cli_start_ms.txt", "utf8").trim();
      const ms = Number(raw);
      return Number.isFinite(ms) && ms > 0 ? ms : options.startMs;
    } catch {
      return options.startMs;
    }
  })();

• Golden files updated for TestWasmGolden_CompileFixtures; new TestBuildAWFCommand_WritesAgentCLIStartTimestamp Go test verifies ordering (timestamp → PathSetup → AWF); three new JS tests cover the happy path, absent-file fallback, and invalid-content fallback.

[Copilot]

Pull request overview

Adjusts OpenTelemetry agent-span timing so gh-aw.<job>.agent starts at the true beginning of the “Execute Agent CLI” step (excluding pre-agent overhead like audits / proxy startup).

Changes:

• Add AgentCLIStartMsPath and write an epoch-ms timestamp as the first command in generated Execute-Agent run blocks (AWF and non-AWF paths).
• Update sendJobConclusionSpan to prefer /tmp/gh-aw/agent_cli_start_ms.txt for the dedicated agent span start time, with fallback to options.startMs.
• Update workflow golden fixtures and add Go + JS tests covering ordering and fallback behaviors.

Show a summary per file

File	Description
pkg/workflow/engine_output.go	Introduces AgentCLIStartMsPath constant for host-written CLI start timestamp.
pkg/workflow/awf_helpers.go	Prepends timestamp write as the first host command in AWF run: blocks.
pkg/workflow/claude_engine.go	Adds timestamp write at start of non-AWF execution command.
pkg/workflow/codex_engine.go	Adds timestamp write at start of non-AWF execution command (both harness and non-harness branches).
pkg/workflow/gemini_engine.go	Adds timestamp write at start of non-AWF execution command.
pkg/workflow/pi_engine.go	Adds timestamp write at start of non-AWF execution command.
pkg/workflow/crush_engine.go	Adds timestamp write at start of non-AWF execution command.
pkg/workflow/copilot_engine_execution.go	Adds timestamp write at start of non-AWF execution command.
actions/setup/js/send_otlp_span.cjs	Reads CLI-start timestamp file to set dedicated agent span start time (with fallback).
actions/setup/js/send_otlp_span.test.cjs	Adds tests for file-present and fallback behaviors for agent span start time.
pkg/workflow/awf_config_test.go	Adds test ensuring timestamp write precedes PathSetup/config/AWF invocation in AWF command.
pkg/workflow/testdata/TestWasmGolden_CompileFixtures/with-imports.golden	Updates golden output to include timestamp write line in run block.
pkg/workflow/testdata/TestWasmGolden_CompileFixtures/smoke-copilot.golden	Updates golden output to include timestamp write line in run block.
pkg/workflow/testdata/TestWasmGolden_CompileFixtures/playwright-cli-mode.golden	Updates golden output to include timestamp write line in run block.
pkg/workflow/testdata/TestWasmGolden_CompileFixtures/basic-copilot.golden	Updates golden output to include timestamp write line in run block.
.github/workflows/technical-doc-writer.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/stale-repo-identifier.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/scout.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/safe-output-health.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/prompt-clustering-analysis.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/org-health-report.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/issue-arborist.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/glossary-maintainer.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/discussion-task-miner.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/deep-report.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/daily-safe-output-optimizer.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/daily-news.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/daily-issues-report.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/copilot-opt.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/cloclo.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/cli-version-checker.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/changeset.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/audit-workflows.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/api-consumption-report.lock.yml	Regenerated lock workflow output (includes updated compiled content).
.github/workflows/agentic_commands.yml	Updates embedded compiler version metadata for agentic commands payload.

Copilot's findings

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• Files reviewed: 35/35 changed files
• Comments generated: 1

[pelikhan]

@copilot review all comments

[Copilot]

@copilot review all comments

Fixed in 5b0d218 — updated the comment from "earlier" to "later" to correctly reflect that cliStartMs (1_700_000_030_000) is 30 s after jobStartMs (1_700_000_000_000).

[pelikhan]

@copilot merge main and recompile.

[Copilot]

@copilot merge main and recompile.

Done — merged origin/main, resolved conflicts in the generated lock files, then recompiled all 223 workflows with a clean binary. The updated lock files and agentic_commands.yml are in the latest commits.